Forget pushed event ids when Google Calendar is disconnected (Feature 16)

Disconnect deleted the connection but left every pushed plan synced with
its stored event ids, though no calendar was chosen any more. It now
deletes the connection and runs the same invalidation as choosing another
calendar (forgetEvents: MarkCalendarPlansEdited, ClearCalendarEvents) in
one transaction, under the account lock. A refused revoke still changes
nothing.

Tests push three weeks, disconnect, and check each is changed with no
event id; then connect again, choose a calendar and push the whole week
to it. Also: a refused revoke keeps every week synced, and a disconnect
during a push waits for its record and then forgets it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

cmd/server/boot_test.go

@@ -44,6 +44,10 @@ func loadConfig(t *testing.T, keyFile string) config.Config {
 	if err := os.WriteFile(clientSecretPath, []byte("client-secret\n"), 0o600); err != nil {
 		t.Fatal(err)
 	}
+	googleSecretPath := filepath.Join(dir, "google_client_secret")
+	if err := os.WriteFile(googleSecretPath, []byte("google-secret\n"), 0o600); err != nil {
+		t.Fatal(err)
+	}
 	t.Setenv(config.EnvHTTPAddr, "127.0.0.1:0")
 	t.Setenv(config.EnvPublicURL, "http://localhost")
 	t.Setenv(config.EnvDataDir, t.TempDir())
@@ -53,6 +57,8 @@ func loadConfig(t *testing.T, keyFile string) config.Config {
 	t.Setenv(config.EnvOIDCClientID, "mealquest")
 	t.Setenv(config.EnvOIDCClientSecretFile, clientSecretPath)
 	t.Setenv(config.EnvOIDCAllowedGroups, "mealquest-admin")
+	t.Setenv(config.EnvGoogleClientID, "mealquest.apps.googleusercontent.com")
+	t.Setenv(config.EnvGoogleClientSecretFile, googleSecretPath)
 	// MEALQUEST_DEFAULT_TZ is left unset; t.Setenv restores any outer value.
 	t.Setenv(config.EnvDefaultTZ, "")
 	if err := os.Unsetenv(config.EnvDefaultTZ); err != nil {

cmd/server/main.go

@@ -21,6 +21,7 @@ import (
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/dinners"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/forwarded"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/frontend"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/household"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/jobs"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/plan"
@@ -113,7 +114,20 @@ func run(cfg config.Config, logger *slog.Logger) error {
 		return err
 	}
 
-	planSvc, err := plan.NewService(db, weekDrafter(ai, guard), runner, logger)
+	googleSvc, err := gcal.NewService(db, box, gcal.Config{
+		ClientID:     cfg.GoogleClientID,
+		ClientSecret: cfg.GoogleClientSecret.Reveal(),
+		PublicURL:    cfg.PublicURL,
+		SecretKey:    []byte(cfg.SecretKey.Reveal()),
+		Endpoint:     gcal.GoogleEndpoint,
+		RevokeURL:    gcal.GoogleRevokeURL,
+		CalendarAPI:  gcal.GoogleCalendarAPI,
+	})
+	if err != nil {
+		return err
+	}
+
+	planSvc, err := plan.NewService(db, weekDrafter(ai, guard), runner, googleSvc, cfg.PublicURL, logger)
 	if err != nil {
 		return err
 	}
@@ -134,7 +148,7 @@ func run(cfg config.Config, logger *slog.Logger) error {
 		return err
 	}
 
-	router, err := server.NewRouter(logger, version, cfg.TrustedProxy, authFlow, sessions, settings, search, ai, dinnerSvc, suggestSvc, planSvc, runner, photos, frontend.Assets())
+	router, err := server.NewRouter(logger, version, cfg.TrustedProxy, authFlow, sessions, settings, search, ai, dinnerSvc, suggestSvc, planSvc, googleSvc, runner, photos, frontend.Assets())
 	if err != nil {
 		return err
 	}

deploy/.env.example

@@ -8,6 +8,7 @@
 #   mkdir -p deploy/secrets && chmod 700 deploy/secrets
 #   head -c 32 /dev/urandom | base64 > deploy/secrets/secret_key
 #   printf '%s\n' '<Authentik client secret>' > deploy/secrets/oidc_client_secret
+#   printf '%s\n' '<Google OAuth client secret>' > deploy/secrets/google_client_secret
 #   sudo chown 10001:10001 deploy/secrets/* && sudo chmod 600 deploy/secrets/*
 #
 # SearXNG's secret key is the exception: compose reads it itself, so it
@@ -54,6 +55,14 @@ MEALQUEST_OIDC_CLIENT_ID=mealquest
 # Comma-separated Authentik groups whose members may sign in.
 MEALQUEST_OIDC_ALLOWED_GROUPS=mealquest-admin
 
+# --- Google Calendar (Push to Calendar) ------------------------------------
+
+# Client ID of the Google OAuth web client (deploy/RUNBOOK.md "Google
+# Calendar OAuth client"). Required: the service will not start without it
+# and the client secret file. Its authorized redirect URI is
+# <MEALQUEST_PUBLIC_URL origin>/api/v1/integrations/google/callback.
+MEALQUEST_GOOGLE_CLIENT_ID=<client id>.apps.googleusercontent.com
+
 # Optional session lifetimes. A session ends after IDLE unused and always MAX
 # after sign-in; MAX must be at least IDLE. Defaults: 720h and 4320h.
 MEALQUEST_SESSION_IDLE=720h
@@ -67,6 +76,8 @@ MEALQUEST_SESSION_MAX=4320h
 #   Base64 of 32 random bytes; encrypts secrets at rest (AES-256-GCM).
 # MEALQUEST_OIDC_CLIENT_SECRET_FILE=/run/secrets/oidc_client_secret
 #   The Authentik provider's client secret.
+# MEALQUEST_GOOGLE_CLIENT_SECRET_FILE=/run/secrets/google_client_secret
+#   The Google OAuth web client's secret.
 # MEALQUEST_SEARXNG_URL=http://searxng:8080
 #   The SearXNG recipe-search sidecar on the compose network. The Settings
 #   screen pre-fills it as the SearXNG URL until one is saved; the saved
@@ -81,7 +92,3 @@ MEALQUEST_SESSION_MAX=4320h
 # MEALQUEST_VAPID_PUBLIC_KEY=<base64url VAPID public key>
 # MEALQUEST_VAPID_PRIVATE_KEY_FILE=/run/secrets/vapid_private_key
 # MEALQUEST_VAPID_SUBJECT=mailto:<owner address>
-#
-# Google Calendar OAuth web client (Feature 16).
-# MEALQUEST_GOOGLE_CLIENT_ID=<client id>.apps.googleusercontent.com
-# MEALQUEST_GOOGLE_CLIENT_SECRET_FILE=/run/secrets/google_client_secret

deploy/RUNBOOK.md

@@ -33,6 +33,8 @@ On office-srvr (10.60.1.14), as recorded on 2026-10-05:
 Elsewhere:
 
 - Admin access to Authentik at <https://auth.cubecraftlabs.com>.
+- Owner access to the Google Cloud project that holds MealQuest's OAuth
+  client (see "Google Calendar OAuth client").
 - SSH access to the Traefik host 10.60.1.33.
 - Cloudflare access for the `cubecraftlabs.com` zone, and admin access to
   both Pi-holes (10.60.1.101 `dns.ccl`, 10.60.1.85 `dns2.ccl`).
@@ -129,6 +131,7 @@ Values in use:
 | `MEALQUEST_OIDC_ISSUER` | `https://auth.cubecraftlabs.com/application/o/mealquest/` |
 | `MEALQUEST_OIDC_CLIENT_ID` | `i6zraqmWsF552b8nmte070LXz0SI5pRdArBxFxeq` (not a secret) |
 | `MEALQUEST_OIDC_ALLOWED_GROUPS` | `mealquest-admin` |
+| `MEALQUEST_GOOGLE_CLIENT_ID` | Client ID of the Google OAuth web client (not a secret; see "Google Calendar OAuth client") |
 | `MEALQUEST_SESSION_IDLE` / `MEALQUEST_SESSION_MAX` | `720h` / `4320h` |
 
 `MEALQUEST_HTTP_ADDR`, `MEALQUEST_DATA_DIR` and the `*_FILE` variables are
@@ -146,6 +149,7 @@ service refuses to start.
 | --- | --- | --- |
 | `secret_key` | base64 of 32 random bytes; encrypts stored secrets (AES-256-GCM) | `/run/secrets/secret_key` |
 | `oidc_client_secret` | Client Secret of the Authentik provider `mealquest` | `/run/secrets/oidc_client_secret` |
+| `google_client_secret` | Client secret of the Google OAuth web client | `/run/secrets/google_client_secret` |
 | `litestream_key` | dedicated SSH private key for the NAS (see "Backups") | `/etc/litestream/sftp_key` |
 | `searxng.env` | `SEARXNG_SECRET=<64 hex characters>`; SearXNG's secret key | not mounted; compose passes it as an environment variable |
 
@@ -156,11 +160,12 @@ it (as `env_file`), so it is owned by `overseer`, mode 0600.
 mkdir -p deploy/secrets && chmod 700 deploy/secrets
 head -c 32 /dev/urandom | base64 > deploy/secrets/secret_key
 printf '%s\n' '<Authentik client secret>' > deploy/secrets/oidc_client_secret
+printf '%s\n' '<Google OAuth client secret>' > deploy/secrets/google_client_secret
 # litestream_key: see "Backups" > "Database — Litestream"
-sudo chown 10001:10001 deploy/secrets/secret_key deploy/secrets/oidc_client_secret deploy/secrets/litestream_key
+sudo chown 10001:10001 deploy/secrets/secret_key deploy/secrets/oidc_client_secret deploy/secrets/google_client_secret deploy/secrets/litestream_key
 sudo chmod 600 deploy/secrets/*
 (umask 077; printf 'SEARXNG_SECRET=%s\n' "$(openssl rand -hex 32)" > deploy/secrets/searxng.env)
-sudo ls -la deploy/secrets   # three files mealquest mealquest, searxng.env overseer overseer; all -rw-------
+sudo ls -la deploy/secrets   # four files mealquest mealquest, searxng.env overseer overseer; all -rw-------
 ```
 
 The `mealquest` host user (uid/gid 10001) is created in "Media — nightly
@@ -238,6 +243,38 @@ On 2026-10-05 discovery returned 200 with issuer
 `https://auth.cubecraftlabs.com/application/o/mealquest/` and
 `id_token_signing_alg_values_supported: ["RS256"]`.
 
+## Google Calendar OAuth client
+
+Push to Calendar connects the household's Google account with a Google
+OAuth web client. MealQuest calls Google's OAuth and Calendar REST
+endpoints directly. **The service will not start without
+`MEALQUEST_GOOGLE_CLIENT_ID` and `deploy/secrets/google_client_secret`**,
+so create the client before deploying a release that contains Feature 16.
+
+In the Google Cloud console, in the project that holds MealQuest:
+
+| Object | Setting |
+| --- | --- |
+| API | Google Calendar API enabled |
+| OAuth consent screen | User type External; app name MealQuest; publishing status **In production** (a client left in Testing gets refresh tokens that expire after 7 days, so Push to Calendar would stop working a week after connecting) |
+| Scopes | `https://www.googleapis.com/auth/calendar.events` and `https://www.googleapis.com/auth/calendar.calendarlist.readonly` |
+| Credentials | OAuth client ID, application type **Web application**, name `mealquest` |
+| Authorized redirect URI | `https://mealquest.cubecraftlabs.com/api/v1/integrations/google/callback` (exactly; it is `MEALQUEST_PUBLIC_URL`'s origin plus that path) |
+| Client ID | in `deploy/.env` as `MEALQUEST_GOOGLE_CLIENT_ID` (not a secret) |
+| Client secret | in `deploy/secrets/google_client_secret` only |
+
+The app is unverified, so Google shows an "unverified app" warning on the
+consent screen; choose to continue. That is expected for a single-household
+deployment.
+
+To connect, a signed-in household member opens
+`https://mealquest.cubecraftlabs.com/api/v1/integrations/google/connect`
+(the Settings screen links there once it ships). MealQuest asks for offline
+access with consent always prompted, and lands back on
+`/settings/calendar` once the refresh token is stored. Disconnecting
+(`DELETE /api/v1/integrations/google`) revokes the token at Google and
+forgets it.
+
 ## Reverse proxy (Traefik)
 
 MealQuest is published at <https://mealquest.cubecraftlabs.com> by the
@@ -1313,6 +1350,23 @@ Sign in at <https://mealquest.cubecraftlabs.com> to confirm; sign-ins
 fail between regenerating the secret in Authentik and recreating the
 service.
 
+### Google OAuth client secret (`deploy/secrets/google_client_secret`)
+
+In the Google Cloud console, open the OAuth client `mealquest`, add a new
+client secret, write it to the file (same owner and mode as above) and
+recreate the service:
+
+```sh
+printf '%s\n' '<new Google OAuth client secret>' | sudo tee deploy/secrets/google_client_secret >/dev/null
+sudo chown 10001:10001 deploy/secrets/google_client_secret
+sudo chmod 600 deploy/secrets/google_client_secret
+docker compose -f deploy/compose.yaml up -d --force-recreate mealquest
+```
+
+Then disable and delete the old secret in the console. A new client secret
+leaves the household's stored refresh token valid, so nothing needs
+reconnecting.
+
 ### LLM API key
 
 Stored encrypted in the database, not in `deploy/`. In the app, open

deploy/compose.yaml

@@ -32,10 +32,12 @@ services:
       MEALQUEST_DATA_DIR: /data
       MEALQUEST_SECRET_KEY_FILE: /run/secrets/secret_key
       MEALQUEST_OIDC_CLIENT_SECRET_FILE: /run/secrets/oidc_client_secret
+      MEALQUEST_GOOGLE_CLIENT_SECRET_FILE: /run/secrets/google_client_secret
       MEALQUEST_SEARXNG_URL: http://searxng:8080
     secrets:
       - secret_key
       - oidc_client_secret
+      - google_client_secret
     volumes:
       - mealquest-data:/data
     ports:
@@ -128,6 +130,8 @@ secrets:
     file: ./secrets/secret_key
   oidc_client_secret:
     file: ./secrets/oidc_client_secret
+  google_client_secret:
+    file: ./secrets/google_client_secret
 
 volumes:
   mealquest-data:

docs/ARCHITECTURE.md

@@ -100,7 +100,7 @@ Columns ending in `_ct` hold AES-256-GCM ciphertext (via `secretbox`).
 | `suggestion_batches` | trigger, status, ai_run_id. |
 | `suggestions` | dinner_id, batch_id, name (the name the dish was suggested under, kept whatever its dinner is later renamed, so a Pass stays an immutable record every later batch dedupes against), reason, cited_regular_ids (JSON), status, decided_at. |
 | `week_plans` | week_start (unique), status (`draft` / `synced` / `changed`), ai_note, ai_run_id, calendar_synced_at, revision (raised by every swap and stored draft). |
-| `plan_days` | plan_id, date (unique per plan), dinner_id, is_new, calendar_event_id. |
+| `plan_days` | plan_id, date (unique per plan), dinner_id, is_new, calendar_event_id (set while the chosen calendar shows the day as planned; cleared when its dinner changes, another calendar is chosen or Google Calendar is disconnected). |
 | `rotation_reviews` | dinner_id + plan_date (unique), status, decision (`keep` / `drop` / `not_made`), name (set only by a drop: the dinner's name when dropped, kept whatever it is later renamed, so a drop stays among the passed names), decided_at, updated_by. |
 | `shopping_lists` | week_start (unique), plan_id, title, status (`current` / `archived`), sent_to_chat_at, frozen_at. |
 | `shopping_groups` / `shopping_items` | One group per dinner/day; item name, qty, needed (bool), position. |
@@ -350,8 +350,9 @@ automatic** (D-021).
   409 `draft_running` and enqueues nothing. The job runs the `draft_week` skill on every Regular
   and every Quest log dinner no other plan for the current or a later week
   has, with the household context and last week's dinners, and stores the
-  week: a new plan is `draft`; a redraft keeps each day's
-  `calendar_event_id`, and a `synced` or `changed` plan becomes `changed`.
+  week: a new plan is `draft`; a redraft keeps the `calendar_event_id` of
+  each day whose dinner stays the same and clears it for the others; a
+  `synced` or `changed` plan becomes `changed`.
   Drafting over a `synced` or `changed` plan needs `{"confirm": true}`, else
   409 `confirm_required`; a plan synced while an unconfirmed draft runs is
   left as it is and the job fails `confirm_required`. The job reads the
@@ -366,8 +367,8 @@ automatic** (D-021).
   dinners fails the job `not_enough_dinners`, draft_week failing
   `ai_failed`. `PUT /api/v1/plans/{weekStart}/days/{date}` takes
   `{dinner_id}`, a Regular or Quest log dinner, swaps the day, recomputes
-  `is_new`, moves a `synced` plan to `changed`, and answers 200 with the
-  plan. A date outside the week is 400 `invalid_date`, an unknown dinner or
+  `is_new`, clears the day's `calendar_event_id`, moves a `synced` plan to
+  `changed`, and answers 200 with the plan. A date outside the week is 400 `invalid_date`, an unknown dinner or
   a week with no plan 404, any other dinner 409 `dinner_not_plannable`, and
   a dinner already on another day of the week 409 `dinner_already_planned`.
 - Rotation check (`plan.Service`, D-021). This release provides the
@@ -618,8 +619,103 @@ Runs are recorded in `schedule_runs` and executed through `jobs`.
   not come back.
 - Connected once with Google OAuth in Settings; one event per planned
   dinner.
-- **Deterministic event ids**; each plan day records its
-  `calendar_event_id`.
+- `internal/gcal` owns the connection, as a confidential OAuth web client
+  (`MEALQUEST_GOOGLE_CLIENT_ID`, `MEALQUEST_GOOGLE_CLIENT_SECRET_FILE`, both
+  required at boot) over plain REST — no Google SDK. Every route is under
+  the signed-in `/api/v1`:
+  - `GET /api/v1/integrations/google/connect` redirects to Google's consent
+    screen with scopes `calendar.events` and `calendar.calendarlist.readonly`,
+    `access_type=offline`, `prompt=consent` and PKCE. Its `state` travels in
+    the signed `__Host-mealquest_google` flow cookie (the same
+    `auth.FlowCookie` mechanism as the login cookie), bound to the session by
+    a hash of the session's CSRF token. The service also keeps each started
+    connect's `state` in memory until the cookie expires; the callback
+    consumes it, so a replayed cookie is refused (`invalid_state`), and a
+    restart mid-connect means connecting again.
+  - `GET /api/v1/integrations/google/callback` (the redirect URI:
+    `MEALQUEST_PUBLIC_URL`'s origin plus this path) checks the state and
+    session, exchanges the code, refuses a response with no refresh token
+    (`reconnect_required`) or without both scopes, seals the refresh token
+    with `secretbox` into `integrations_google.refresh_token_ct`, sets
+    `connected_at` and redirects to `/settings/calendar`. A reconnect keeps
+    the chosen calendar and clears `last_sync_error`.
+  - `DELETE /api/v1/integrations/google` (CSRF-checked) revokes the token at
+    Google, then deletes the row and, in the same transaction, forgets every
+    pushed event (see Push to Calendar); a token Google reports as
+    `invalid_token` counts as revoked, and any other revoke failure keeps
+    the connection and its pushed events.
+  - `GET /api/v1/integrations/google/calendars` trades the stored refresh
+    token for an access token and reads every page of the Calendar API's
+    `users/me/calendarList`, answering `[{id, summary, primary,
+    accessRole}]` for the calendars whose `accessRole` is `writer` or
+    `owner`, in Google's order. Nothing else from Google's response is
+    passed on.
+  - `PUT /api/v1/integrations/google/calendar` `{calendar_id}`
+    (CSRF-checked) lists the calendars the same way and stores
+    `calendar_id` and `calendar_name` (the calendar's `summary`) only when
+    the id is among them, answering `{calendar_id, calendar_name}`; any
+    other id is 422 `unknown_calendar` and leaves the stored choice as it
+    was. A calendar chosen earlier that has since been deleted or become
+    read-only drops out of the listing and cannot be chosen again; the
+    stored choice stays until the household chooses another.
+  - Listing and choosing answer 409 `not_connected` when nothing is
+    connected, and 502 `reconnect_required` when Google no longer accepts
+    the grant (`invalid_grant` on refresh, or HTTP 401 from the Calendar
+    API); the connection is left as it is. Any other Google failure is 502
+    `google_failed`.
+  - Connect's exchange-and-store, disconnect's read-revoke-delete and
+    every use of the stored token (listing and choosing calendars) hold one
+    lock across the Google requests and the database write: Google revokes
+    the whole grant, so a revoke overlapping a reconnect would otherwise
+    leave a stored token Google has already revoked.
+  - No response, log line or error ever holds a token or Google's response
+    text.
+- Push to Calendar: `POST /api/v1/plans/{weekStart}/push-calendar`
+  (CSRF-checked, `plan.Service.Push` writing through
+  `gcal.Service.PushEvents`) answers 200 with the plan as synced. Each day
+  is one event in the chosen calendar: summary `Dinner: {name}`, from the
+  household `dinner_time` on that date for 60 minutes, as `dateTime` with
+  the household `timeZone` (so its UTC instant follows a DST change within
+  the week), and a description of the dinner's name, `Start by {time}` for
+  a crock-pot dinner of known minutes, and
+  `{MEALQUEST_PUBLIC_URL}/dinner/{id}`.
+  - **Deterministic event ids**: lowercase unpadded base32hex of SHA-256 of
+    `mealquest|{weekStart}|{date}` — 52 characters of `a`–`v` and `0`–`9`,
+    within Google's id rule. Each event is inserted; a 409 (the id exists,
+    even as an event deleted in Calendar) updates it instead, with status
+    `confirmed`, so pushing again never adds a second event.
+  - A push writes the days whose `calendar_event_id` is empty (never
+    pushed, swapped, or redrafted to another dinner). When none is, it
+    writes every day again, which puts back anything changed in Calendar.
+  - A stored `calendar_event_id` is always an event on the chosen calendar.
+    Choosing a calendar other than the stored one, and disconnecting (which
+    leaves none chosen; connecting again chooses none either), clear every
+    day's `calendar_event_id` in the same transaction as the choice or the
+    delete, and edit each plan that had one (revision raised, `synced` →
+    `changed`), so the next push writes the whole week to the calendar then
+    chosen and a push that read such a plan before is refused (409
+    `plan_changed`). A reconnect while connected keeps the chosen calendar,
+    so it keeps the event ids. Nothing else clears the choice or the stored
+    token: a grant Google refuses leaves the connection as it is.
+  - Only a push that wrote all its events is recorded, in one transaction:
+    the plan becomes `synced` with `calendar_synced_at`, and each day
+    written stores its event id. A push that failed part way records
+    nothing and leaves the status as it was; pushing again updates the
+    events already written. The record runs under the account lock, in the
+    same hold as the event writes, so the chosen calendar cannot change
+    between them. A plan swapped or redrafted while it was being
+    pushed, or whose events another calendar choice cleared (its revision
+    moved), is not recorded: 409 `plan_changed`.
+  - Errors: 409 `not_connected`, 409 `no_calendar` (connected, no calendar
+    chosen), 409 `calendar_unavailable` (the chosen calendar was deleted —
+    Google 404 — or is no longer writable — 403 `requiredAccessLevel`;
+    choose another), 502 `reconnect_required` (the grant is refused; the
+    connection is left as it is), 502 `google_failed`, 404 when the week
+    has no plan, 400 `invalid_week`. The push holds the account lock
+    across its Google requests and its record, like listing and choosing.
+  - The week's Supply run (Feature 17) is made from a pushed plan: a
+    successful `Push` returns that plan, which is where Feature 17 hooks
+    in. Nothing here generates a shopping list.
 
 ## Frontend
 

internal/auth/auth.go

@@ -107,7 +107,7 @@ func New(ctx context.Context, cfg Config, sessions Sessions, logger *slog.Logger
 		return nil, err
 	}
 
-	client := &http.Client{Timeout: providerTimeout, CheckRedirect: checkRedirect}
+	client := &http.Client{Timeout: providerTimeout, CheckRedirect: CheckRedirect}
 	discovery := *client
 	recorder := &statusRecorder{next: http.DefaultTransport}
 	discovery.Transport = recorder
@@ -205,11 +205,12 @@ func checkEndpoint(name, raw string) error {
 // maxRedirects matches net/http's default redirect limit.
 const maxRedirects = 10
 
-// checkRedirect is the provider client's redirect policy. On a 307 or 308 to
-// the same host Go resends the body and Authorization header, which carry the
-// code and client secret, so every target must pass secureurl.Check and an
-// https:// request never follows a redirect to plain http://, even loopback.
-func checkRedirect(req *http.Request, via []*http.Request) error {
+// CheckRedirect is the redirect policy of every client that talks to an
+// OAuth provider. On a 307 or 308 to the same host Go resends the body and
+// Authorization header, which carry the code and client secret, so every
+// target must pass secureurl.Check and an https:// request never follows a
+// redirect to plain http://, even loopback.
+func CheckRedirect(req *http.Request, via []*http.Request) error {
 	if len(via) >= maxRedirects {
 		return fmt.Errorf("stopped after %d redirects", maxRedirects)
 	}
@@ -350,7 +351,7 @@ func (a *Auth) verify(ctx context.Context, code string, state loginState) (Claim
 	token, err := a.oauth.Exchange(context.WithValue(ctx, oauth2.HTTPClient, a.client), code,
 		oauth2.VerifierOption(state.Verifier))
 	if err != nil {
-		return Claims{}, exchangeError(err)
+		return Claims{}, ExchangeError(err)
 	}
 	raw, ok := token.Extra("id_token").(string)
 	if !ok || raw == "" {
@@ -400,7 +401,7 @@ func (a *Auth) userinfoGroups(ctx context.Context, token *oauth2.Token, subject
 }
 
 // userinfoError reduces a failed userinfo request to a fixed category, like
-// exchangeError: go-oidc's error text can carry the response body.
+// ExchangeError: go-oidc's error text can carry the response body.
 func userinfoError(err error) error {
 	var transport *url.Error
 	if errors.As(err, &transport) {
@@ -425,10 +426,11 @@ func (a *Auth) member(groups []string) bool {
 	return slices.ContainsFunc(groups, func(g string) bool { return slices.Contains(a.allowed, g) })
 }
 
-// exchangeError reduces a failed code exchange to a fixed category and safe
-// metadata. The oauth2 error text can carry the token endpoint's response
-// body or error_description, which may echo credentials, so it is dropped.
-func exchangeError(err error) error {
+// ExchangeError reduces a failed OAuth code exchange to a fixed category and
+// safe metadata. The oauth2 error text can carry the token endpoint's
+// response body or error_description, which may echo credentials, so it is
+// dropped.
+func ExchangeError(err error) error {
 	var retrieve *oauth2.RetrieveError
 	var transport *url.Error
 	switch {

internal/auth/auth_test.go

@@ -1060,7 +1060,7 @@ func TestCheckRedirect(t *testing.T) {
 		{"https://auth.example.com/token", "ftp://auth.example.com/token", false},
 	}
 	for _, tc := range tests {
-		err := checkRedirect(request(tc.to), []*http.Request{request(tc.from)})
+		err := CheckRedirect(request(tc.to), []*http.Request{request(tc.from)})
 		if (err == nil) != tc.ok {
 			t.Errorf("redirect %s -> %s: error = %v, want ok=%v", tc.from, tc.to, err, tc.ok)
 		}
@@ -1069,7 +1069,7 @@ func TestCheckRedirect(t *testing.T) {
 	for i := range via {
 		via[i] = request("https://auth.example.com/token")
 	}
-	if err := checkRedirect(request("https://auth.example.com/token"), via); err == nil {
+	if err := CheckRedirect(request("https://auth.example.com/token"), via); err == nil {
 		t.Errorf("redirect after %d hops: error = nil, want limit", maxRedirects)
 	}
 }

internal/auth/cookie.go

@@ -27,38 +27,86 @@ type loginState struct {
 	Nonce    string `json:"n"`
 	Verifier string `json:"v"`
 	Return   string `json:"r"`
-	Expires  int64  `json:"e"` // Unix seconds
+	FlowExpiry
 }
 
-// loginCookie signs and verifies the login cookie with HMAC-SHA256.
+// loginCookie is the FlowCookie carrying loginState.
 type loginCookie struct {
-	key []byte
+	flow FlowCookie
 }
 
 func newLoginCookie(secretKey []byte) loginCookie {
-	mac := hmac.New(sha256.New, secretKey)
-	mac.Write([]byte(loginCookieKeyLabel))
-	return loginCookie{key: mac.Sum(nil)}
+	return loginCookie{flow: NewFlowCookie(loginCookieName, loginCookieKeyLabel, loginCookieTTL, secretKey)}
 }
 
-func (c loginCookie) sign(payload string) string {
+func (c loginCookie) set(w http.ResponseWriter, s loginState, now time.Time) error {
+	return c.flow.Set(w, &s, now)
+}
+
+func (c loginCookie) clear(w http.ResponseWriter) { c.flow.Clear(w) }
+
+func (c loginCookie) read(r *http.Request, now time.Time) (loginState, error) {
+	var s loginState
+	if err := c.flow.Read(r, &s, now); err != nil {
+		return loginState{}, err
+	}
+	return s, nil
+}
+
+// FlowExpiry is embedded in every value a FlowCookie carries; Set fills it
+// and Read enforces it.
+type FlowExpiry struct {
+	Expires int64 `json:"e"` // Unix seconds
+}
+
+func (e *FlowExpiry) flowExpiry() *FlowExpiry { return e }
+
+// flowValue is a pointer to a struct that embeds FlowExpiry.
+type flowValue interface {
+	flowExpiry() *FlowExpiry
+}
+
+// FlowCookie carries a redirect flow's state — the OAuth state, PKCE
+// verifier and the like — from the request that sends the browser to a
+// provider to the callback it returns to. The value is JSON, signed with
+// HMAC-SHA256 under a key derived from the server secret and the cookie's
+// own label, and expires after a fixed time. It is not encrypted: it must
+// not hold anything the browser may not see.
+type FlowCookie struct {
+	name string
+	ttl  time.Duration
+	key  []byte
+}
+
+// NewFlowCookie returns the flow cookie name, valid for ttl, signed under a
+// key derived from secretKey and keyLabel. Each flow uses its own keyLabel so
+// one flow's cookie never verifies as another's. name must carry the __Host-
+// prefix: the cookie is Secure, host-only and Path=/.
+func NewFlowCookie(name, keyLabel string, ttl time.Duration, secretKey []byte) FlowCookie {
+	mac := hmac.New(sha256.New, secretKey)
+	mac.Write([]byte(keyLabel))
+	return FlowCookie{name: name, ttl: ttl, key: mac.Sum(nil)}
+}
+
+func (c FlowCookie) sign(payload string) string {
 	mac := hmac.New(sha256.New, c.key)
 	mac.Write([]byte(payload))
 	return base64.RawURLEncoding.EncodeToString(mac.Sum(nil))
 }
 
-func (c loginCookie) set(w http.ResponseWriter, s loginState, now time.Time) error {
-	s.Expires = now.Add(loginCookieTTL).Unix()
-	data, err := json.Marshal(s)
+// Set stores v, which expires ttl after now, in the cookie.
+func (c FlowCookie) Set(w http.ResponseWriter, v flowValue, now time.Time) error {
+	v.flowExpiry().Expires = now.Add(c.ttl).Unix()
+	data, err := json.Marshal(v)
 	if err != nil {
 		return err
 	}
 	payload := base64.RawURLEncoding.EncodeToString(data)
 	http.SetCookie(w, &http.Cookie{
-		Name:     loginCookieName,
+		Name:     c.name,
 		Value:    payload + "." + c.sign(payload),
 		Path:     "/",
-		MaxAge:   int(loginCookieTTL / time.Second),
+		MaxAge:   int(c.ttl / time.Second),
 		Secure:   true,
 		HttpOnly: true,
 		// Lax so the cookie rides the provider's top-level redirect back.
@@ -67,9 +115,12 @@ func (c loginCookie) set(w http.ResponseWriter, s loginState, now time.Time) err
 	return nil
 }
 
-func (c loginCookie) clear(w http.ResponseWriter) {
+// Clear asks the browser to discard the cookie. A copy of it still verifies
+// until it expires, so a flow that must be single-use also consumes its
+// state on the server.
+func (c FlowCookie) Clear(w http.ResponseWriter) {
 	http.SetCookie(w, &http.Cookie{
-		Name:     loginCookieName,
+		Name:     c.name,
 		Path:     "/",
 		MaxAge:   -1,
 		Secure:   true,
@@ -78,27 +129,28 @@ func (c loginCookie) clear(w http.ResponseWriter) {
 	})
 }
 
-func (c loginCookie) read(r *http.Request, now time.Time) (loginState, error) {
-	cookie, err := r.Cookie(loginCookieName)
+// Read verifies the cookie r carries and decodes it into v. It fails when
+// the cookie is missing, its signature is invalid or it has expired at now.
+func (c FlowCookie) Read(r *http.Request, v flowValue, now time.Time) error {
+	cookie, err := r.Cookie(c.name)
 	if err != nil {
-		return loginState{}, errors.New("login cookie missing")
+		return fmt.Errorf("%s cookie missing", c.name)
 	}
 	payload, sig, ok := strings.Cut(cookie.Value, ".")
 	if !ok || !hmac.Equal([]byte(sig), []byte(c.sign(payload))) {
-		return loginState{}, errors.New("login cookie signature invalid")
+		return fmt.Errorf("%s cookie signature invalid", c.name)
 	}
 	data, err := base64.RawURLEncoding.DecodeString(payload)
 	if err != nil {
-		return loginState{}, fmt.Errorf("login cookie encoding: %w", err)
+		return fmt.Errorf("%s cookie encoding: %w", c.name, err)
 	}
-	var s loginState
-	if err := json.Unmarshal(data, &s); err != nil {
-		return loginState{}, fmt.Errorf("login cookie payload: %w", err)
+	if err := json.Unmarshal(data, v); err != nil {
+		return fmt.Errorf("%s cookie payload: %w", c.name, err)
 	}
-	if now.Unix() >= s.Expires {
-		return loginState{}, errors.New("login cookie expired")
+	if now.Unix() >= v.flowExpiry().Expires {
+		return fmt.Errorf("%s cookie expired", c.name)
 	}
-	return s, nil
+	return nil
 }
 
 // returnPath validates the optional post-login return path. Empty means "/".

internal/config/config.go

@@ -29,6 +29,9 @@ const (
 	EnvOIDCClientSecretFile = "MEALQUEST_OIDC_CLIENT_SECRET_FILE"
 	EnvOIDCAllowedGroups    = "MEALQUEST_OIDC_ALLOWED_GROUPS"
 
+	EnvGoogleClientID         = "MEALQUEST_GOOGLE_CLIENT_ID"
+	EnvGoogleClientSecretFile = "MEALQUEST_GOOGLE_CLIENT_SECRET_FILE"
+
 	EnvSessionIdle = "MEALQUEST_SESSION_IDLE"
 	EnvSessionMax  = "MEALQUEST_SESSION_MAX"
 
@@ -61,6 +64,12 @@ type Config struct {
 	// OIDCAllowedGroups lists the groups whose members may sign in.
 	OIDCAllowedGroups []string
 
+	// GoogleClientID and GoogleClientSecret are the Google OAuth web client
+	// Push to Calendar connects with. Its redirect URI is PublicURL's origin
+	// followed by /api/v1/integrations/google/callback.
+	GoogleClientID     string
+	GoogleClientSecret Secret
+
 	// SessionIdle ends a session left unused this long.
 	SessionIdle time.Duration
 	// SessionMax ends every session this long after sign-in, used or not.
@@ -110,6 +119,9 @@ func load(lookup func(string) (string, bool)) (Config, error) {
 		OIDCClientSecret:  r.secretFile(EnvOIDCClientSecretFile),
 		OIDCAllowedGroups: r.list(EnvOIDCAllowedGroups),
 
+		GoogleClientID:     r.str(EnvGoogleClientID),
+		GoogleClientSecret: r.secretFile(EnvGoogleClientSecretFile),
+
 		SessionIdle: r.sessionDuration(EnvSessionIdle, DefaultSessionIdle),
 		SessionMax:  r.sessionDuration(EnvSessionMax, DefaultSessionMax),
 

internal/config/config_test.go

@@ -29,6 +29,10 @@ func TestLoad(t *testing.T) {
 	if err := os.WriteFile(clientSecretPath, []byte("client-s3cret\n"), 0o600); err != nil {
 		t.Fatal(err)
 	}
+	googleSecretPath := filepath.Join(dir, "google_client_secret")
+	if err := os.WriteFile(googleSecretPath, []byte("google-s3cret\n"), 0o600); err != nil {
+		t.Fatal(err)
+	}
 	emptyPath := filepath.Join(dir, "empty_secret")
 	if err := os.WriteFile(emptyPath, []byte("\n"), 0o600); err != nil {
 		t.Fatal(err)
@@ -46,6 +50,9 @@ func TestLoad(t *testing.T) {
 			EnvOIDCClientID:         "mealquest",
 			EnvOIDCClientSecretFile: clientSecretPath,
 			EnvOIDCAllowedGroups:    "mealquest-admin",
+
+			EnvGoogleClientID:         "mealquest.apps.googleusercontent.com",
+			EnvGoogleClientSecretFile: googleSecretPath,
 		}
 	}
 	with := func(changes map[string]string, unset ...string) map[string]string {
@@ -94,6 +101,7 @@ func TestLoad(t *testing.T) {
 			badVars: []string{
 				EnvHTTPAddr, EnvPublicURL, EnvDataDir, EnvShutdownTimeout, EnvSecretKeyFile,
 				EnvOIDCIssuer, EnvOIDCClientID, EnvOIDCClientSecretFile, EnvOIDCAllowedGroups,
+				EnvGoogleClientID, EnvGoogleClientSecretFile,
 			},
 		},
 		{
@@ -211,6 +219,31 @@ func TestLoad(t *testing.T) {
 			env:     with(map[string]string{"MEALQUEST_SECRET_KEY": "inline"}),
 			badVars: []string{"MEALQUEST_SECRET_KEY"},
 		},
+		{
+			name:    "Google client ID missing",
+			env:     with(nil, EnvGoogleClientID),
+			badVars: []string{EnvGoogleClientID},
+		},
+		{
+			name:    "Google client secret file missing",
+			env:     with(nil, EnvGoogleClientSecretFile),
+			badVars: []string{EnvGoogleClientSecretFile},
+		},
+		{
+			name:    "Google client secret file unreadable",
+			env:     with(map[string]string{EnvGoogleClientSecretFile: unreadablePath}),
+			badVars: []string{EnvGoogleClientSecretFile},
+		},
+		{
+			name:    "Google client secret file empty",
+			env:     with(map[string]string{EnvGoogleClientSecretFile: emptyPath}),
+			badVars: []string{EnvGoogleClientSecretFile},
+		},
+		{
+			name:    "inline Google client secret rejected",
+			env:     with(map[string]string{"MEALQUEST_GOOGLE_CLIENT_SECRET": "inline"}),
+			badVars: []string{"MEALQUEST_GOOGLE_CLIENT_SECRET"},
+		},
 		{
 			name:    "inline OIDC client secret rejected",
 			env:     with(map[string]string{"MEALQUEST_OIDC_CLIENT_SECRET": "inline"}),
@@ -409,6 +442,10 @@ func TestLoadValues(t *testing.T) {
 	if err := os.WriteFile(clientSecretPath, []byte("client-s3cret\n"), 0o600); err != nil {
 		t.Fatal(err)
 	}
+	googleSecretPath := filepath.Join(dir, "google_client_secret")
+	if err := os.WriteFile(googleSecretPath, []byte("google-s3cret\n"), 0o600); err != nil {
+		t.Fatal(err)
+	}
 	env := map[string]string{
 		EnvHTTPAddr:        "127.0.0.1:9000",
 		EnvPublicURL:       "http://localhost:9000",
@@ -421,6 +458,9 @@ func TestLoadValues(t *testing.T) {
 		EnvOIDCClientSecretFile: clientSecretPath,
 		EnvOIDCAllowedGroups:    " mealquest-admin ,family",
 
+		EnvGoogleClientID:         "mealquest.apps.googleusercontent.com",
+		EnvGoogleClientSecretFile: googleSecretPath,
+
 		EnvDefaultTZ: "Europe/London",
 
 		EnvSearXNGURL: "http://searxng:8080",
@@ -454,6 +494,12 @@ func TestLoadValues(t *testing.T) {
 	if cfg.OIDCClientSecret.Reveal() != "client-s3cret" {
 		t.Errorf("OIDCClientSecret.Reveal() = %q", cfg.OIDCClientSecret.Reveal())
 	}
+	if cfg.GoogleClientID != "mealquest.apps.googleusercontent.com" {
+		t.Errorf("GoogleClientID = %q", cfg.GoogleClientID)
+	}
+	if cfg.GoogleClientSecret.Reveal() != "google-s3cret" {
+		t.Errorf("GoogleClientSecret.Reveal() = %q", cfg.GoogleClientSecret.Reveal())
+	}
 	if want := []string{"mealquest-admin", "family"}; !slices.Equal(cfg.OIDCAllowedGroups, want) {
 		t.Errorf("OIDCAllowedGroups = %q, want %q", cfg.OIDCAllowedGroups, want)
 	}
@@ -492,7 +538,7 @@ func TestSecretRedacted(t *testing.T) {
 
 	s := Secret{value: "s3cret-value"}
 	for _, format := range []string{"%v", "%s", "%+v", "%#v"} {
-		cfg := Config{SecretKey: s, OIDCClientSecret: s}
+		cfg := Config{SecretKey: s, OIDCClientSecret: s, GoogleClientSecret: s}
 		for _, out := range []string{fmt.Sprintf(format, s), fmt.Sprintf(format, cfg)} {
 			if strings.Contains(out, "s3cret-value") {
 				t.Errorf("format %s leaked secret: %s", format, out)

internal/db/plans.sql.go

@@ -10,6 +10,18 @@ import (
 	"database/sql"
 )
 
+const clearCalendarEvents = `-- name: ClearCalendarEvents :exec
+UPDATE plan_days
+SET calendar_event_id = NULL, updated_at = ?
+WHERE calendar_event_id IS NOT NULL
+`
+
+// Clears every day's calendar event id: none is on the chosen calendar.
+func (q *Queries) ClearCalendarEvents(ctx context.Context, updatedAt string) error {
+	_, err := q.db.ExecContext(ctx, clearCalendarEvents, updatedAt)
+	return err
+}
+
 const createWeekPlan = `-- name: CreateWeekPlan :exec
 INSERT INTO week_plans (id, week_start, status, ai_note, created_at, updated_at)
 VALUES (?, ?, 'draft', ?, ?, ?)
@@ -154,7 +166,7 @@ func (q *Queries) ListDraftPool(ctx context.Context, arg ListDraftPoolParams) ([
 }
 
 const listPlanDays = `-- name: ListPlanDays :many
-SELECT plan_days.date, plan_days.is_new, dinners.id, dinners.name, dinners.normalized_name, dinners.status, dinners.origin, dinners.method, dinners.minutes_total, dinners.difficulty, dinners.cuisine, dinners.is_favorite, dinners.recipe_id, dinners.photo_id, dinners.grounding_status, dinners.updated_by, dinners.created_at, dinners.updated_at, dinners.recipe_url, dinners.grounding_error, dinners.grounding_revision
+SELECT plan_days.date, plan_days.is_new, plan_days.calendar_event_id, dinners.id, dinners.name, dinners.normalized_name, dinners.status, dinners.origin, dinners.method, dinners.minutes_total, dinners.difficulty, dinners.cuisine, dinners.is_favorite, dinners.recipe_id, dinners.photo_id, dinners.grounding_status, dinners.updated_by, dinners.created_at, dinners.updated_at, dinners.recipe_url, dinners.grounding_error, dinners.grounding_revision
 FROM plan_days
 JOIN dinners ON dinners.id = plan_days.dinner_id
 WHERE plan_days.plan_id = ?
@@ -162,9 +174,10 @@ ORDER BY plan_days.date
 `
 
 type ListPlanDaysRow struct {
-	Date   string
-	IsNew  int64
-	Dinner Dinner
+	Date            string
+	IsNew           int64
+	CalendarEventID sql.NullString
+	Dinner          Dinner
 }
 
 // The days of plan plan_id with their dinners, Monday first. A day with
@@ -181,6 +194,7 @@ func (q *Queries) ListPlanDays(ctx context.Context, planID string) ([]ListPlanDa
 		if err := rows.Scan(
 			&i.Date,
 			&i.IsNew,
+			&i.CalendarEventID,
 			&i.Dinner.ID,
 			&i.Dinner.Name,
 			&i.Dinner.NormalizedName,
@@ -247,6 +261,26 @@ func (q *Queries) ListWeekPlanDinnerIDs(ctx context.Context, weekStart string) (
 	return items, nil
 }
 
+const markCalendarPlansEdited = `-- name: MarkCalendarPlansEdited :exec
+UPDATE week_plans
+SET status = CASE WHEN status = 'synced' THEN 'changed' ELSE status END,
+	revision = revision + 1,
+	updated_at = ?
+WHERE EXISTS (
+	SELECT 1 FROM plan_days
+	WHERE plan_days.plan_id = week_plans.id AND plan_days.calendar_event_id IS NOT NULL
+)
+`
+
+// Records that Calendar no longer shows the days with a calendar event id
+// as planned, since another calendar or none is chosen: every plan with
+// such a day is edited as MarkWeekPlanEdited does, so a synced plan becomes
+// changed and a push that read it before is refused.
+func (q *Queries) MarkCalendarPlansEdited(ctx context.Context, updatedAt string) error {
+	_, err := q.db.ExecContext(ctx, markCalendarPlansEdited, updatedAt)
+	return err
+}
+
 const markWeekPlanEdited = `-- name: MarkWeekPlanEdited :exec
 UPDATE week_plans
 SET status = CASE WHEN status = 'synced' THEN 'changed' ELSE status END,
@@ -267,11 +301,42 @@ func (q *Queries) MarkWeekPlanEdited(ctx context.Context, arg MarkWeekPlanEdited
 	return err
 }
 
+const markWeekPlanSynced = `-- name: MarkWeekPlanSynced :execrows
+UPDATE week_plans
+SET status = 'synced', calendar_synced_at = ?, updated_at = ?
+WHERE id = ? AND revision = ?
+`
+
+type MarkWeekPlanSyncedParams struct {
+	CalendarSyncedAt sql.NullString
+	UpdatedAt        string
+	ID               string
+	Revision         int64
+}
+
+// Records a Push to Calendar of plan id as it was at revision: the plan
+// becomes synced. A plan edited since (another revision) is left as it is
+// (0 rows).
+func (q *Queries) MarkWeekPlanSynced(ctx context.Context, arg MarkWeekPlanSyncedParams) (int64, error) {
+	result, err := q.db.ExecContext(ctx, markWeekPlanSynced,
+		arg.CalendarSyncedAt,
+		arg.UpdatedAt,
+		arg.ID,
+		arg.Revision,
+	)
+	if err != nil {
+		return 0, err
+	}
+	return result.RowsAffected()
+}
+
 const putPlanDay = `-- name: PutPlanDay :exec
 INSERT INTO plan_days (id, plan_id, date, dinner_id, is_new, created_at, updated_at)
 VALUES (?, ?, ?, ?, ?, ?, ?)
 ON CONFLICT (plan_id, date) DO UPDATE
-SET dinner_id = excluded.dinner_id, is_new = excluded.is_new, updated_at = excluded.updated_at
+SET dinner_id = excluded.dinner_id, is_new = excluded.is_new,
+	calendar_event_id = CASE WHEN plan_days.dinner_id IS excluded.dinner_id THEN plan_days.calendar_event_id END,
+	updated_at = excluded.updated_at
 `
 
 type PutPlanDayParams struct {
@@ -284,8 +349,9 @@ type PutPlanDayParams struct {
 	UpdatedAt string
 }
 
-// Plans dinner_id on date of plan_id, keeping the day's calendar event id
-// when the day exists.
+// Plans dinner_id on date of plan_id. An existing day keeps its calendar
+// event id while its dinner stays the same; a new dinner clears it, since
+// Calendar no longer shows the day as planned.
 func (q *Queries) PutPlanDay(ctx context.Context, arg PutPlanDayParams) error {
 	_, err := q.db.ExecContext(ctx, putPlanDay,
 		arg.ID,
@@ -324,9 +390,37 @@ func (q *Queries) RedraftWeekPlan(ctx context.Context, arg RedraftWeekPlanParams
 	return err
 }
 
+const setPlanDayCalendarEvent = `-- name: SetPlanDayCalendarEvent :execrows
+UPDATE plan_days
+SET calendar_event_id = ?, updated_at = ?
+WHERE plan_id = ? AND date = ?
+`
+
+type SetPlanDayCalendarEventParams struct {
+	CalendarEventID sql.NullString
+	UpdatedAt       string
+	PlanID          string
+	Date            string
+}
+
+// Records that the event calendar_event_id on Calendar shows date of
+// plan_id as planned.
+func (q *Queries) SetPlanDayCalendarEvent(ctx context.Context, arg SetPlanDayCalendarEventParams) (int64, error) {
+	result, err := q.db.ExecContext(ctx, setPlanDayCalendarEvent,
+		arg.CalendarEventID,
+		arg.UpdatedAt,
+		arg.PlanID,
+		arg.Date,
+	)
+	if err != nil {
+		return 0, err
+	}
+	return result.RowsAffected()
+}
+
 const swapPlanDay = `-- name: SwapPlanDay :execrows
 UPDATE plan_days
-SET dinner_id = ?, is_new = ?, updated_at = ?
+SET dinner_id = ?, is_new = ?, calendar_event_id = NULL, updated_at = ?
 WHERE plan_id = ? AND date = ?
 `
 
@@ -338,8 +432,9 @@ type SwapPlanDayParams struct {
 	Date      string
 }
 
-// Plans dinner_id on an existing day of plan_id; a date the plan does not
-// have is left as it is (0 rows).
+// Plans dinner_id on an existing day of plan_id, clearing its calendar
+// event id since Calendar no longer shows the day as planned; a date the
+// plan does not have is left as it is (0 rows).
 func (q *Queries) SwapPlanDay(ctx context.Context, arg SwapPlanDayParams) (int64, error) {
 	result, err := q.db.ExecContext(ctx, swapPlanDay,
 		arg.DinnerID,

internal/db/querier.go

@@ -15,6 +15,8 @@ type Querier interface {
 	// Marks the oldest queued job running and returns it. Returns sql.ErrNoRows
 	// when no job is queued.
 	ClaimNextJob(ctx context.Context, now sql.NullString) (Job, error)
+	// Clears every day's calendar event id: none is on the chosen calendar.
+	ClearCalendarEvents(ctx context.Context, updatedAt string) error
 	// Drops references to the runs created before the cutoff, so the purge
 	// can delete them.
 	ClearSuggestionBatchAIRunsBefore(ctx context.Context, cutoff string) (int64, error)
@@ -50,6 +52,7 @@ type Querier interface {
 	// decided is left as it is (0 rows).
 	DecideSuggestion(ctx context.Context, arg DecideSuggestionParams) (int64, error)
 	DeleteAIRunsBefore(ctx context.Context, cutoff string) (int64, error)
+	DeleteIntegrationsGoogle(ctx context.Context) error
 	DeleteRecipeIngredients(ctx context.Context, recipeID string) error
 	DeleteRecipeSteps(ctx context.Context, recipeID string) error
 	FailJob(ctx context.Context, arg FailJobParams) (int64, error)
@@ -169,12 +172,21 @@ type Querier interface {
 	// The ids of the dinners planned in the week starting week_start, Monday
 	// first.
 	ListWeekPlanDinnerIDs(ctx context.Context, weekStart string) ([]sql.NullString, error)
+	// Records that Calendar no longer shows the days with a calendar event id
+	// as planned, since another calendar or none is chosen: every plan with
+	// such a day is edited as MarkWeekPlanEdited does, so a synced plan becomes
+	// changed and a push that read it before is refused.
+	MarkCalendarPlansEdited(ctx context.Context, updatedAt string) error
 	// Moves a dinner still in the Quest log to tried; a dinner with any other
 	// status is left as it is (0 rows).
 	MarkDinnerTried(ctx context.Context, arg MarkDinnerTriedParams) (int64, error)
 	// Records an edit of plan id, raising its revision: a synced plan becomes
 	// changed, any other keeps its status.
 	MarkWeekPlanEdited(ctx context.Context, arg MarkWeekPlanEditedParams) error
+	// Records a Push to Calendar of plan id as it was at revision: the plan
+	// becomes synced. A plan edited since (another revision) is left as it is
+	// (0 rows).
+	MarkWeekPlanSynced(ctx context.Context, arg MarkWeekPlanSyncedParams) (int64, error)
 	// Moves a dinner still suggested to status (quest_log or archived),
 	// recording updated_by; a dinner no longer suggested is left as it is
 	// (0 rows).
@@ -185,20 +197,27 @@ type Querier interface {
 	MoveTriedDinner(ctx context.Context, arg MoveTriedDinnerParams) (int64, error)
 	// Stores a partial result of a running job.
 	PublishJobResult(ctx context.Context, arg PublishJobResultParams) (int64, error)
-	// Plans dinner_id on date of plan_id, keeping the day's calendar event id
-	// when the day exists.
+	// Plans dinner_id on date of plan_id. An existing day keeps its calendar
+	// event id while its dinner stays the same; a new dinner clears it, since
+	// Calendar no longer shows the day as planned.
 	PutPlanDay(ctx context.Context, arg PutPlanDayParams) error
 	// Records a new draft over plan id: its status and note, raising its
 	// revision.
 	RedraftWeekPlan(ctx context.Context, arg RedraftWeekPlanParams) error
 	// An unknown id returns sql.ErrNoRows.
 	SetDinnerFavorite(ctx context.Context, arg SetDinnerFavoriteParams) (Dinner, error)
+	// Sets the chosen calendar; affects no row when nothing is connected.
+	SetIntegrationsGoogleCalendar(ctx context.Context, arg SetIntegrationsGoogleCalendarParams) (int64, error)
+	// Records that the event calendar_event_id on Calendar shows date of
+	// plan_id as planned.
+	SetPlanDayCalendarEvent(ctx context.Context, arg SetPlanDayCalendarEventParams) (int64, error)
 	// Marks a pending batch running; a batch in any other status is left as
 	// it is (0 rows).
 	StartSuggestionBatch(ctx context.Context, arg StartSuggestionBatchParams) (int64, error)
 	SucceedJob(ctx context.Context, arg SucceedJobParams) (int64, error)
-	// Plans dinner_id on an existing day of plan_id; a date the plan does not
-	// have is left as it is (0 rows).
+	// Plans dinner_id on an existing day of plan_id, clearing its calendar
+	// event id since Calendar no longer shows the day as planned; a date the
+	// plan does not have is left as it is (0 rows).
 	SwapPlanDay(ctx context.Context, arg SwapPlanDayParams) (int64, error)
 	// An unknown id returns sql.ErrNoRows.
 	ToggleDinnerFavorite(ctx context.Context, arg ToggleDinnerFavoriteParams) (Dinner, error)

internal/db/settings.sql.go

@@ -10,6 +10,16 @@ import (
 	"database/sql"
 )
 
+const deleteIntegrationsGoogle = `-- name: DeleteIntegrationsGoogle :exec
+DELETE FROM integrations_google
+WHERE id = 1
+`
+
+func (q *Queries) DeleteIntegrationsGoogle(ctx context.Context) error {
+	_, err := q.db.ExecContext(ctx, deleteIntegrationsGoogle)
+	return err
+}
+
 const getAISettings = `-- name: GetAISettings :one
 SELECT id, provider, base_url, model, temperature, system_prompt, api_key_ct, api_key_last4, key_verified_at, created_at, updated_at FROM ai_settings
 WHERE id = 1
@@ -129,6 +139,27 @@ func (q *Queries) GetRecipeSearchSettings(ctx context.Context) (RecipeSearchSett
 	return i, err
 }
 
+const setIntegrationsGoogleCalendar = `-- name: SetIntegrationsGoogleCalendar :execrows
+UPDATE integrations_google
+SET calendar_id = ?, calendar_name = ?, updated_at = ?
+WHERE id = 1
+`
+
+type SetIntegrationsGoogleCalendarParams struct {
+	CalendarID   sql.NullString
+	CalendarName sql.NullString
+	UpdatedAt    string
+}
+
+// Sets the chosen calendar; affects no row when nothing is connected.
+func (q *Queries) SetIntegrationsGoogleCalendar(ctx context.Context, arg SetIntegrationsGoogleCalendarParams) (int64, error) {
+	result, err := q.db.ExecContext(ctx, setIntegrationsGoogleCalendar, arg.CalendarID, arg.CalendarName, arg.UpdatedAt)
+	if err != nil {
+		return 0, err
+	}
+	return result.RowsAffected()
+}
+
 const upsertAISettings = `-- name: UpsertAISettings :one
 INSERT INTO ai_settings (
 	id, provider, base_url, model, temperature, system_prompt, api_key_ct,

internal/gcal/calendars.go

@@ -0,0 +1,274 @@
+package gcal
+
+import (
+	"context"
+	"database/sql"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"time"
+
+	"golang.org/x/oauth2"
+
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/db"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/store"
+)
+
+const (
+	// calendarPageSize is the calendarList page size: Google's maximum.
+	calendarPageSize = 250
+	// maxCalendarPages caps how many calendarList pages a listing reads.
+	maxCalendarPages = 20
+	// maxCalendarBody caps how much of one calendarList page is read.
+	maxCalendarBody = 1 << 20
+)
+
+var (
+	// ErrReconnect means Google no longer accepts the stored grant: the
+	// household revoked MealQuest's access in their Google account, or the
+	// refresh token expired. Only connecting again restores it.
+	ErrReconnect = errors.New("gcal: Google no longer accepts MealQuest's access; connect Google Calendar again")
+	// ErrUnknownCalendar means the calendar chosen is not one the connected
+	// account can push to.
+	ErrUnknownCalendar = errors.New("gcal: not a calendar MealQuest can add dinners to")
+)
+
+// Calendar is one calendar the connected account can push to.
+type Calendar struct {
+	ID         string `json:"id"`
+	Summary    string `json:"summary"`
+	Primary    bool   `json:"primary"`
+	AccessRole string `json:"accessRole"`
+}
+
+// Selection is the calendar MealQuest pushes to.
+type Selection struct {
+	CalendarID   string `json:"calendar_id"`
+	CalendarName string `json:"calendar_name"`
+}
+
+// CalendarError is a Calendar API or token refresh request Google refused
+// or that failed in transit. Its text never holds a token or Google's
+// response body.
+type CalendarError struct {
+	msg string
+}
+
+func (e *CalendarError) Error() string { return e.msg }
+
+// Calendars lists the connected account's calendars it can push to: those
+// it is a writer or owner of, in Google's order.
+func (s *Service) Calendars(ctx context.Context) ([]Calendar, error) {
+	s.account.Lock()
+	defer s.account.Unlock()
+	return s.calendars(ctx)
+}
+
+// SelectCalendar makes id the calendar MealQuest pushes to, storing its id
+// and name. id must be among Calendars at the time of the call; anything
+// else, including a calendar chosen earlier that has since been deleted or
+// is no longer writable, is ErrUnknownCalendar and leaves the stored
+// choice as it was. Choosing another calendar than the one chosen returns
+// every plan pushed to that one to not synced; see saveSelection.
+func (s *Service) SelectCalendar(ctx context.Context, id string) (Selection, error) {
+	s.account.Lock()
+	defer s.account.Unlock()
+	cals, err := s.calendars(ctx)
+	if err != nil {
+		return Selection{}, err
+	}
+	for _, c := range cals {
+		if c.ID != id {
+			continue
+		}
+		sel := Selection{CalendarID: c.ID, CalendarName: c.Summary}
+		if err := s.saveSelection(ctx, sel); err != nil {
+			return Selection{}, err
+		}
+		return sel, nil
+	}
+	return Selection{}, ErrUnknownCalendar
+}
+
+// saveSelection stores sel as the chosen calendar. Choosing another calendar
+// than the one stored also forgets every plan day's calendar event id, in
+// the same transaction, since those events are on the calendar no longer
+// chosen (forgetEvents): each plan with one is edited, so a synced plan
+// becomes changed and its next push writes every day to sel. The caller
+// holds s.account, which a push also holds from its event writes through
+// recording them, so a push never records events written to another
+// calendar than the chosen one.
+func (s *Service) saveSelection(ctx context.Context, sel Selection) error {
+	return s.st.WithTx(ctx, func(tx *sql.Tx) error {
+		q := db.New(tx)
+		row, err := q.GetIntegrationsGoogle(ctx)
+		if errors.Is(err, sql.ErrNoRows) {
+			// The lock is held since the connection was read, so only a
+			// change outside this service gets here.
+			return ErrNotConnected
+		}
+		if err != nil {
+			return fmt.Errorf("gcal: read Google integration: %w", err)
+		}
+		now := store.Timestamp{Time: s.now().UTC().Truncate(time.Millisecond)}.String()
+		if _, err := q.SetIntegrationsGoogleCalendar(ctx, db.SetIntegrationsGoogleCalendarParams{
+			CalendarID:   sql.NullString{String: sel.CalendarID, Valid: true},
+			CalendarName: sql.NullString{String: sel.CalendarName, Valid: true},
+			UpdatedAt:    now,
+		}); err != nil {
+			return fmt.Errorf("gcal: save calendar: %w", err)
+		}
+		if row.CalendarID.Valid && row.CalendarID.String == sel.CalendarID {
+			return nil
+		}
+		return forgetEvents(ctx, q, now)
+	})
+}
+
+// forgetEvents records, in the caller's transaction q, that no calendar
+// event id stored is on the chosen calendar any more: every plan with one is
+// edited (a synced plan becomes changed, and a push that read it before is
+// refused), then every id is cleared. Every change that ends the chosen
+// calendar — choosing another (saveSelection) or disconnecting
+// (Disconnect) — runs it in the transaction that makes the change.
+func forgetEvents(ctx context.Context, q *db.Queries, now string) error {
+	if err := q.MarkCalendarPlansEdited(ctx, now); err != nil {
+		return fmt.Errorf("gcal: mark plans pushed to the earlier calendar edited: %w", err)
+	}
+	if err := q.ClearCalendarEvents(ctx, now); err != nil {
+		return fmt.Errorf("gcal: forget events on the earlier calendar: %w", err)
+	}
+	return nil
+}
+
+// calendars lists the writable calendars, each once, with the stored refresh
+// token. The caller holds s.account.
+func (s *Service) calendars(ctx context.Context) ([]Calendar, error) {
+	row, err := s.connection(ctx)
+	if err != nil {
+		return nil, err
+	}
+	access, err := s.accessToken(ctx, row)
+	if err != nil {
+		return nil, err
+	}
+	cals := []Calendar{}
+	// listed holds the ids in cals: pages can overlap, and a calendar is
+	// listed once, as Google first lists it.
+	listed := map[string]bool{}
+	pageToken := ""
+	for range maxCalendarPages {
+		page, err := s.calendarPage(ctx, access, pageToken)
+		if err != nil {
+			return nil, err
+		}
+		for _, item := range page.Items {
+			if item.ID == "" {
+				return nil, &CalendarError{msg: "gcal: Google listed a calendar without an id"}
+			}
+			if (item.AccessRole == "writer" || item.AccessRole == "owner") && !listed[item.ID] {
+				listed[item.ID] = true
+				cals = append(cals, Calendar{ID: item.ID, Summary: item.Summary, Primary: item.Primary, AccessRole: item.AccessRole})
+			}
+		}
+		if page.NextPageToken == "" {
+			return cals, nil
+		}
+		pageToken = page.NextPageToken
+	}
+	return nil, &CalendarError{msg: fmt.Sprintf("gcal: Google listed more than %d pages of calendars", maxCalendarPages)}
+}
+
+// connection reads the connected account, or ErrNotConnected.
+func (s *Service) connection(ctx context.Context) (db.IntegrationsGoogle, error) {
+	row, err := db.New(s.st.Reader).GetIntegrationsGoogle(ctx)
+	if errors.Is(err, sql.ErrNoRows) {
+		return db.IntegrationsGoogle{}, ErrNotConnected
+	}
+	if err != nil {
+		return db.IntegrationsGoogle{}, fmt.Errorf("gcal: read Google integration: %w", err)
+	}
+	return row, nil
+}
+
+// accessToken trades row's refresh token for an access token. A grant
+// Google reports as invalid_grant is ErrReconnect.
+func (s *Service) accessToken(ctx context.Context, row db.IntegrationsGoogle) (string, error) {
+	refresh, err := s.box.Decrypt(row.RefreshTokenCt)
+	if err != nil {
+		return "", fmt.Errorf("gcal: open refresh token: %w", err)
+	}
+	token, err := s.oauth.TokenSource(context.WithValue(ctx, oauth2.HTTPClient, s.client),
+		&oauth2.Token{RefreshToken: string(refresh)}).Token()
+	if err != nil {
+		var retrieve *oauth2.RetrieveError
+		var transport *url.Error
+		switch {
+		case errors.As(err, &retrieve) && retrieve.ErrorCode == "invalid_grant":
+			return "", ErrReconnect
+		case errors.As(err, &retrieve):
+			return "", &CalendarError{msg: fmt.Sprintf("gcal: Google refused the token refresh (HTTP %d)", retrieve.Response.StatusCode)}
+		case errors.As(err, &transport):
+			// The URL is dropped: after a refused redirect it is the
+			// Google-supplied Location.
+			return "", &CalendarError{msg: fmt.Sprintf("gcal: token refresh failed: %s: %v", transport.Op, transport.Err)}
+		default:
+			return "", &CalendarError{msg: "gcal: token refresh returned an unusable response"}
+		}
+	}
+	return token.AccessToken, nil
+}
+
+// calendarListPage is the part of a calendarList page MealQuest reads.
+type calendarListPage struct {
+	Items []struct {
+		ID         string `json:"id"`
+		Summary    string `json:"summary"`
+		Primary    bool   `json:"primary"`
+		AccessRole string `json:"accessRole"`
+	} `json:"items"`
+	NextPageToken string `json:"nextPageToken"`
+}
+
+// calendarPage fetches the calendarList page at pageToken ("" for the
+// first) with access. HTTP 401 means Google no longer accepts the grant.
+func (s *Service) calendarPage(ctx context.Context, access, pageToken string) (calendarListPage, error) {
+	q := url.Values{"maxResults": {fmt.Sprint(calendarPageSize)}}
+	if pageToken != "" {
+		q.Set("pageToken", pageToken)
+	}
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, s.calendarAPI+"/users/me/calendarList?"+q.Encode(), nil)
+	if err != nil {
+		return calendarListPage{}, fmt.Errorf("gcal: build calendar list request: %w", err)
+	}
+	req.Header.Set("Authorization", "Bearer "+access)
+	resp, err := s.client.Do(req)
+	if err != nil {
+		var transport *url.Error
+		if errors.As(err, &transport) {
+			return calendarListPage{}, &CalendarError{msg: fmt.Sprintf("gcal: calendar list request failed: %s: %v", transport.Op, transport.Err)}
+		}
+		return calendarListPage{}, &CalendarError{msg: "gcal: calendar list request failed"}
+	}
+	defer resp.Body.Close()
+	body, err := io.ReadAll(io.LimitReader(resp.Body, maxCalendarBody+1))
+	if err != nil {
+		return calendarListPage{}, &CalendarError{msg: "gcal: read calendar list failed"}
+	}
+	switch {
+	case resp.StatusCode == http.StatusUnauthorized:
+		return calendarListPage{}, ErrReconnect
+	case resp.StatusCode != http.StatusOK:
+		return calendarListPage{}, &CalendarError{msg: fmt.Sprintf("gcal: Google refused the calendar list (HTTP %d)", resp.StatusCode)}
+	case len(body) > maxCalendarBody:
+		return calendarListPage{}, &CalendarError{msg: fmt.Sprintf("gcal: calendar list page exceeds %d bytes", maxCalendarBody)}
+	}
+	var page calendarListPage
+	if err := json.Unmarshal(body, &page); err != nil {
+		return calendarListPage{}, &CalendarError{msg: "gcal: Google returned an unreadable calendar list"}
+	}
+	return page, nil
+}

internal/gcal/calendars_test.go

@@ -0,0 +1,302 @@
+package gcal_test
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"net/http"
+	"reflect"
+	"testing"
+	"time"
+
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal/gcaltest"
+)
+
+// Calendars the fake lists: two the household can push to, two it cannot,
+// and a third writable one with Google fields MealQuest must not pass on.
+var (
+	ownPrimary = gcaltest.Calendar{ID: "household@gmail.com", Summary: "household@gmail.com", Primary: true, AccessRole: "owner"}
+	family     = gcaltest.Calendar{ID: "family@group.calendar.google.com", Summary: "Family", AccessRole: "writer",
+		Description: "private notes", SummaryOverride: "Fam"}
+	holidays = gcaltest.Calendar{ID: "en.usa#holiday@group.v.calendar.google.com", Summary: "Holidays", AccessRole: "reader"}
+	busy     = gcaltest.Calendar{ID: "coworker@example.com", Summary: "Coworker", AccessRole: "freeBusyReader"}
+	dinners  = gcaltest.Calendar{ID: "dinners@group.calendar.google.com", Summary: "Dinners", AccessRole: "owner"}
+)
+
+// connected is a harness with the household's Google account connected
+// and the fake listing every calendar above, two to a page.
+func connected(t *testing.T) *harness {
+	t.Helper()
+	h := newHarness(t)
+	c := h.connect(t, session)
+	if _, err := h.callback(c, session, h.consented(c)); err != nil {
+		t.Fatalf("Complete: %v", err)
+	}
+	h.google.SetCalendars(2, ownPrimary, holidays, family, busy, dinners)
+	return h
+}
+
+func TestCalendarsListsWritableCalendars(t *testing.T) {
+	t.Parallel()
+	h := connected(t)
+	cals, err := h.svc.Calendars(context.Background())
+	if err != nil {
+		t.Fatalf("Calendars: %v", err)
+	}
+	got, err := json.Marshal(cals)
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Exactly the writer and owner calendars, in Google's order, with only
+	// id, summary, primary and accessRole.
+	want := `[` +
+		`{"id":"household@gmail.com","summary":"household@gmail.com","primary":true,"accessRole":"owner"},` +
+		`{"id":"family@group.calendar.google.com","summary":"Family","primary":false,"accessRole":"writer"},` +
+		`{"id":"dinners@group.calendar.google.com","summary":"Dinners","primary":false,"accessRole":"owner"}]`
+	if string(got) != want {
+		t.Errorf("Calendars =\n%s\nwant\n%s", got, want)
+	}
+	if n := h.google.CalendarCalls(); n != 3 {
+		t.Errorf("calendarList called %d times, want 3 (every page)", n)
+	}
+	if _, ok := h.row(t); !ok {
+		t.Error("listing changed the connection")
+	}
+}
+
+func TestCalendarsOverlappingPages(t *testing.T) {
+	t.Parallel()
+	h := connected(t)
+	// Two to a page, family ends the first page and starts the second
+	// again, renamed in between.
+	renamed := family
+	renamed.Summary = "Family (renamed)"
+	h.google.SetCalendars(2, ownPrimary, family, renamed, dinners)
+	cals, err := h.svc.Calendars(context.Background())
+	if err != nil {
+		t.Fatalf("Calendars: %v", err)
+	}
+	got, err := json.Marshal(cals)
+	if err != nil {
+		t.Fatal(err)
+	}
+	// family once, as first listed, in Google's order.
+	want := `[` +
+		`{"id":"household@gmail.com","summary":"household@gmail.com","primary":true,"accessRole":"owner"},` +
+		`{"id":"family@group.calendar.google.com","summary":"Family","primary":false,"accessRole":"writer"},` +
+		`{"id":"dinners@group.calendar.google.com","summary":"Dinners","primary":false,"accessRole":"owner"}]`
+	if string(got) != want {
+		t.Errorf("Calendars =\n%s\nwant\n%s", got, want)
+	}
+	if n := h.google.CalendarCalls(); n != 2 {
+		t.Errorf("calendarList called %d times, want 2 (every page)", n)
+	}
+}
+
+func TestCalendarsEmpty(t *testing.T) {
+	t.Parallel()
+	h := connected(t)
+	h.google.SetCalendars(0, holidays)
+	cals, err := h.svc.Calendars(context.Background())
+	if err != nil {
+		t.Fatalf("Calendars: %v", err)
+	}
+	if got, _ := json.Marshal(cals); string(got) != "[]" {
+		t.Errorf("Calendars = %s, want []", got)
+	}
+}
+
+func TestCalendarsNotConnected(t *testing.T) {
+	t.Parallel()
+	h := newHarness(t)
+	if _, err := h.svc.Calendars(context.Background()); !errors.Is(err, gcal.ErrNotConnected) {
+		t.Errorf("Calendars = %v, want ErrNotConnected", err)
+	}
+	if _, err := h.svc.SelectCalendar(context.Background(), family.ID); !errors.Is(err, gcal.ErrNotConnected) {
+		t.Errorf("SelectCalendar = %v, want ErrNotConnected", err)
+	}
+	if h.google.TokenCalls() != 0 || h.google.CalendarCalls() != 0 {
+		t.Error("Google was called with nothing connected")
+	}
+}
+
+func TestSelectCalendarStoresIDAndName(t *testing.T) {
+	t.Parallel()
+	h := connected(t)
+	before, _ := h.row(t)
+	h.clock = h.clock.Add(time.Hour)
+
+	sel, err := h.svc.SelectCalendar(context.Background(), family.ID)
+	if err != nil {
+		t.Fatalf("SelectCalendar: %v", err)
+	}
+	if sel != (gcal.Selection{CalendarID: family.ID, CalendarName: "Family"}) {
+		t.Errorf("selection = %+v", sel)
+	}
+	row, _ := h.row(t)
+	if row.CalendarID.String != family.ID || !row.CalendarID.Valid ||
+		row.CalendarName.String != "Family" || !row.CalendarName.Valid {
+		t.Errorf("stored calendar = %v %v, want %s Family", row.CalendarID, row.CalendarName, family.ID)
+	}
+	if row.UpdatedAt != "2026-10-07T19:30:00.000Z" {
+		t.Errorf("updated_at = %q, want the choice's time", row.UpdatedAt)
+	}
+	if !bytes.Equal(row.RefreshTokenCt, before.RefreshTokenCt) || row.ConnectedAt != before.ConnectedAt || row.CreatedAt != before.CreatedAt {
+		t.Error("choosing a calendar changed the connection")
+	}
+
+	// Choosing again replaces the choice.
+	if _, err := h.svc.SelectCalendar(context.Background(), ownPrimary.ID); err != nil {
+		t.Fatalf("second SelectCalendar: %v", err)
+	}
+	if row, _ := h.row(t); row.CalendarID.String != ownPrimary.ID || row.CalendarName.String != ownPrimary.Summary {
+		t.Errorf("stored calendar = %v %v, want the primary", row.CalendarID, row.CalendarName)
+	}
+}
+
+func TestSelectCalendarRejectsUnlistedCalendar(t *testing.T) {
+	t.Parallel()
+	for name, id := range map[string]string{
+		"unknown":          "nobody@group.calendar.google.com",
+		"reader":           holidays.ID,
+		"free/busy reader": busy.ID,
+	} {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+			h := connected(t)
+			if _, err := h.svc.SelectCalendar(context.Background(), dinners.ID); err != nil {
+				t.Fatal(err)
+			}
+			before, _ := h.row(t)
+			if _, err := h.svc.SelectCalendar(context.Background(), id); !errors.Is(err, gcal.ErrUnknownCalendar) {
+				t.Fatalf("SelectCalendar(%s) = %v, want ErrUnknownCalendar", id, err)
+			}
+			if row, _ := h.row(t); !reflect.DeepEqual(row, before) {
+				t.Errorf("a refused choice changed the row: %+v", row)
+			}
+		})
+	}
+}
+
+// TestSelectCalendarNoLongerWritable chooses a calendar, then has Google
+// stop listing it as writable, as when it is deleted or the household's
+// access drops to reader. It leaves the listing, and choosing it again is
+// refused; the stored choice stays until the household chooses another.
+func TestSelectCalendarNoLongerWritable(t *testing.T) {
+	t.Parallel()
+	for name, now := range map[string][]gcaltest.Calendar{
+		"deleted":         {ownPrimary},
+		"demoted to read": {ownPrimary, {ID: family.ID, Summary: family.Summary, AccessRole: "reader"}},
+	} {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+			h := connected(t)
+			if _, err := h.svc.SelectCalendar(context.Background(), family.ID); err != nil {
+				t.Fatal(err)
+			}
+			h.google.SetCalendars(0, now...)
+			cals, err := h.svc.Calendars(context.Background())
+			if err != nil {
+				t.Fatal(err)
+			}
+			if len(cals) != 1 || cals[0].ID != ownPrimary.ID {
+				t.Errorf("Calendars = %+v, want only the primary", cals)
+			}
+			if _, err := h.svc.SelectCalendar(context.Background(), family.ID); !errors.Is(err, gcal.ErrUnknownCalendar) {
+				t.Errorf("choosing it again = %v, want ErrUnknownCalendar", err)
+			}
+			if row, _ := h.row(t); row.CalendarID.String != family.ID {
+				t.Errorf("stored calendar = %v, want the earlier choice kept", row.CalendarID)
+			}
+		})
+	}
+}
+
+// TestCalendarsGrantNoLongerAccepted lists calendars after Google stops
+// accepting MealQuest's grant. The failure is ErrReconnect; the connection
+// is left as it is.
+func TestCalendarsGrantNoLongerAccepted(t *testing.T) {
+	t.Parallel()
+	for name, edit := range map[string]func(*gcaltest.Google){
+		"refresh refused":            (*gcaltest.Google).RevokeGrant,
+		"calendar list unauthorized": func(g *gcaltest.Google) { g.FailCalendarList(http.StatusUnauthorized) },
+	} {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+			h := connected(t)
+			edit(h.google)
+			_, err := h.svc.Calendars(context.Background())
+			if !errors.Is(err, gcal.ErrReconnect) {
+				t.Fatalf("Calendars = %v, want ErrReconnect", err)
+			}
+			assertNoSecret(t, "error", err.Error())
+			_, err = h.svc.SelectCalendar(context.Background(), family.ID)
+			if !errors.Is(err, gcal.ErrReconnect) {
+				t.Fatalf("SelectCalendar = %v, want ErrReconnect", err)
+			}
+			row, ok := h.row(t)
+			if !ok || row.CalendarID.Valid {
+				t.Errorf("row = %+v, %v: want the connection kept with no calendar", row, ok)
+			}
+		})
+	}
+}
+
+func TestCalendarsGoogleFailureIsRedacted(t *testing.T) {
+	t.Parallel()
+	for name, edit := range map[string]func(*gcaltest.Google){
+		"token endpoint": func(g *gcaltest.Google) { g.FailToken(http.StatusServiceUnavailable) },
+		"calendar list":  func(g *gcaltest.Google) { g.FailCalendarList(http.StatusForbidden) },
+	} {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+			h := connected(t)
+			edit(h.google)
+			_, err := h.svc.Calendars(context.Background())
+			var calendar *gcal.CalendarError
+			if !errors.As(err, &calendar) {
+				t.Fatalf("Calendars = %v, want *CalendarError", err)
+			}
+			assertNoSecret(t, "error", err.Error())
+		})
+	}
+}
+
+// TestSelectCalendarHoldsTheAccount holds a calendar choice at Google while
+// a disconnect starts: the disconnect waits for the choice, so it never
+// revokes the token the choice is using.
+func TestSelectCalendarHoldsTheAccount(t *testing.T) {
+	t.Parallel()
+	h := connected(t)
+	h.google.SetCalendars(0, family)
+	arrived, release := h.google.HoldCalendarList()
+	defer release()
+	selected := make(chan error, 1)
+	go func() {
+		_, err := h.svc.SelectCalendar(context.Background(), family.ID)
+		selected <- err
+	}()
+	<-arrived
+	disconnected := make(chan error, 1)
+	go func() { disconnected <- h.svc.Disconnect(context.Background()) }()
+	select {
+	case err := <-disconnected:
+		t.Fatalf("Disconnect finished (%v) while a calendar choice was at Google", err)
+	case <-time.After(200 * time.Millisecond):
+	}
+	if n := len(h.google.Revoked()); n != 0 {
+		t.Fatalf("revoked %d tokens while a calendar choice was at Google", n)
+	}
+	release()
+	if err := <-selected; err != nil {
+		t.Errorf("SelectCalendar: %v", err)
+	}
+	if err := <-disconnected; err != nil {
+		t.Errorf("Disconnect: %v", err)
+	}
+	if _, ok := h.row(t); ok {
+		t.Error("connection stored after the disconnect")
+	}
+}

internal/gcal/connect.go

@@ -0,0 +1,420 @@
+// Package gcal connects the household's Google account for Push to Calendar.
+// The service is a confidential OAuth web client: the authorization code,
+// tokens and client secret stay on the server. The refresh token is stored
+// sealed by secretbox in integrations_google and is never logged or
+// returned.
+package gcal
+
+import (
+	"context"
+	"crypto/rand"
+	"crypto/sha256"
+	"crypto/subtle"
+	"database/sql"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"slices"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/oauth2"
+	"golang.org/x/oauth2/endpoints"
+
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/auth"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/db"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/secretbox"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/store"
+)
+
+// CallbackPath is where Google returns the browser after consent. It is
+// served under the signed-in /api/v1 router, so the redirect URI registered
+// with Google is MEALQUEST_PUBLIC_URL's origin followed by this path.
+const CallbackPath = "/api/v1/integrations/google/callback"
+
+// Scopes requested at connect: create and change the events MealQuest pushes,
+// and list the calendars the household can push to.
+var Scopes = []string{
+	"https://www.googleapis.com/auth/calendar.events",
+	"https://www.googleapis.com/auth/calendar.calendarlist.readonly",
+}
+
+// GoogleRevokeURL is Google's OAuth token revocation endpoint.
+const GoogleRevokeURL = "https://oauth2.googleapis.com/revoke"
+
+// GoogleCalendarAPI is the base URL of Google's Calendar API v3.
+const GoogleCalendarAPI = "https://www.googleapis.com/calendar/v3"
+
+// GoogleEndpoint is Google's OAuth authorization and token endpoint.
+var GoogleEndpoint = oauth2.Endpoint{
+	AuthURL:   endpoints.Google.AuthURL,
+	TokenURL:  endpoints.Google.TokenURL,
+	AuthStyle: oauth2.AuthStyleInParams,
+}
+
+const (
+	connectCookieName = "__Host-mealquest_google"
+	connectCookieTTL  = 10 * time.Minute
+	// connectCookieKeyLabel separates the connect cookie's signing key from
+	// the login cookie's and every other key derived from the server secret.
+	connectCookieKeyLabel = "mealquest google connect cookie v1"
+	// googleTimeout bounds every request to Google.
+	googleTimeout = 10 * time.Second
+	// maxRevokeBody caps how much of a revoke response is read.
+	maxRevokeBody = 4 << 10
+)
+
+var (
+	// ErrBadState means the callback's state is missing, does not match the
+	// connect cookie, or the cookie is missing, expired or belongs to another
+	// session.
+	ErrBadState = errors.New("gcal: connect state is missing, expired or does not match this session")
+	// ErrDenied means Google returned an authorization error, usually because
+	// the household declined consent.
+	ErrDenied = errors.New("gcal: Google did not grant access")
+	// ErrNoCode means the callback carries no authorization code.
+	ErrNoCode = errors.New("gcal: callback has no authorization code")
+	// ErrNoRefreshToken means Google granted access without a refresh token,
+	// so MealQuest could not push later; the household must connect again.
+	ErrNoRefreshToken = errors.New("gcal: Google returned no refresh token")
+	// ErrScopes means the household did not grant every scope in Scopes.
+	ErrScopes = errors.New("gcal: Google did not grant every Calendar permission")
+	// ErrNotConnected means no Google account is connected.
+	ErrNotConnected = errors.New("gcal: Google Calendar is not connected")
+)
+
+// Config is what NewService needs to talk to Google.
+type Config struct {
+	ClientID     string
+	ClientSecret string
+	// PublicURL is the service's public URL; its origin prefixes CallbackPath
+	// to form the redirect URI.
+	PublicURL *url.URL
+	// SecretKey is the server key the connect cookie's signing key derives
+	// from.
+	SecretKey []byte
+	// Endpoint is Google's authorization and token endpoint; production uses
+	// GoogleEndpoint and tests a fake.
+	Endpoint oauth2.Endpoint
+	// RevokeURL is Google's revocation endpoint; production uses
+	// GoogleRevokeURL and tests a fake.
+	RevokeURL string
+	// CalendarAPI is the Calendar API's base URL; production uses
+	// GoogleCalendarAPI and tests a fake.
+	CalendarAPI string
+}
+
+// Service connects and disconnects the household's Google account,
+// chooses the calendar MealQuest pushes to and writes events to it.
+// MealQuest runs as one process, so the service's in-memory lock and pending
+// states see every request.
+type Service struct {
+	st        *store.Store
+	box       *secretbox.Box
+	oauth     oauth2.Config
+	revokeURL string
+	// calendarAPI is the Calendar API's base URL.
+	calendarAPI string
+	client      *http.Client
+	cookie      auth.FlowCookie
+	// now is the clock; tests replace it.
+	now func() time.Time
+
+	// account serializes every use of and change to the connected account —
+	// a connect's exchange and store, a disconnect's read, revoke and delete,
+	// a calendar listing's read and Calendar API calls, a calendar choice's
+	// listing and store, an event push's read, event writes and record —
+	// across the requests to Google and the database write. Google revokes the whole grant, so a revoke overlapping a
+	// connect would also kill the token the connect stores.
+	account sync.Mutex
+
+	// pending holds the state of every connect started and not yet
+	// completed, with when it expires. Complete consumes a state once, so a
+	// replayed cookie finds it gone.
+	pendingMu sync.Mutex
+	pending   map[string]time.Time
+}
+
+// NewService returns the service over st, sealing refresh tokens with box.
+func NewService(st *store.Store, box *secretbox.Box, cfg Config) (*Service, error) {
+	switch {
+	case st == nil:
+		return nil, errors.New("gcal: nil store")
+	case box == nil:
+		return nil, errors.New("gcal: nil secret box")
+	case cfg.ClientID == "", cfg.ClientSecret == "":
+		return nil, errors.New("gcal: client ID and client secret are required")
+	case cfg.PublicURL == nil:
+		return nil, errors.New("gcal: public URL is required")
+	case len(cfg.SecretKey) == 0:
+		return nil, errors.New("gcal: secret key is required")
+	case cfg.Endpoint.AuthURL == "", cfg.Endpoint.TokenURL == "", cfg.RevokeURL == "", cfg.CalendarAPI == "":
+		return nil, errors.New("gcal: authorization, token, revoke and Calendar API endpoints are required")
+	}
+	return &Service{
+		st:  st,
+		box: box,
+		oauth: oauth2.Config{
+			ClientID:     cfg.ClientID,
+			ClientSecret: cfg.ClientSecret,
+			Endpoint:     cfg.Endpoint,
+			RedirectURL:  cfg.PublicURL.Scheme + "://" + cfg.PublicURL.Host + CallbackPath,
+			Scopes:       slices.Clone(Scopes),
+		},
+		revokeURL:   cfg.RevokeURL,
+		calendarAPI: cfg.CalendarAPI,
+		client:      &http.Client{Timeout: googleTimeout, CheckRedirect: auth.CheckRedirect},
+		cookie:      auth.NewFlowCookie(connectCookieName, connectCookieKeyLabel, connectCookieTTL, cfg.SecretKey),
+		now:         time.Now,
+		pending:     map[string]time.Time{},
+	}, nil
+}
+
+// connectState travels from Connect to Complete in the signed connect
+// cookie.
+type connectState struct {
+	State    string `json:"s"`
+	Verifier string `json:"v"`
+	// Session binds the state to the session that started the connect: the
+	// SHA-256 of its CSRF token, which is unique to the session and never
+	// changes during it.
+	Session string `json:"b"`
+	auth.FlowExpiry
+}
+
+// sessionBinding is the value connectState.Session must hold for s.
+func sessionBinding(s auth.Session) string {
+	sum := sha256.Sum256([]byte(s.CSRFToken))
+	return hex.EncodeToString(sum[:])
+}
+
+// Connect sets the connect cookie on w, bound to session, and returns
+// Google's consent URL: offline access, consent always prompted so Google
+// always issues a refresh token, and PKCE (S256).
+func (s *Service) Connect(w http.ResponseWriter, session auth.Session) (string, error) {
+	if session.CSRFToken == "" {
+		return "", errors.New("gcal: connect needs a session")
+	}
+	state := connectState{
+		State:    rand.Text(),
+		Verifier: oauth2.GenerateVerifier(),
+		Session:  sessionBinding(session),
+	}
+	now := s.now()
+	if err := s.cookie.Set(w, &state, now); err != nil {
+		return "", fmt.Errorf("gcal: set connect cookie: %w", err)
+	}
+	s.addPending(state.State, now)
+	return s.oauth.AuthCodeURL(state.State,
+		oauth2.AccessTypeOffline,
+		oauth2.ApprovalForce,
+		oauth2.S256ChallengeOption(state.Verifier),
+	), nil
+}
+
+// Complete finishes the connect Google redirected r back with. It clears the
+// connect cookie, checks the state against it and session, consumes the
+// state, exchanges the code and stores the refresh token, sealed, with
+// connected_at now. A reconnect replaces the stored token and keeps the
+// chosen calendar.
+func (s *Service) Complete(w http.ResponseWriter, r *http.Request, session auth.Session) error {
+	ctx := r.Context()
+	s.cookie.Clear(w)
+
+	var state connectState
+	if err := s.cookie.Read(r, &state, s.now()); err != nil {
+		return fmt.Errorf("%w: %v", ErrBadState, err)
+	}
+	q := r.URL.Query()
+	if subtle.ConstantTimeCompare([]byte(q.Get("state")), []byte(state.State)) != 1 {
+		return fmt.Errorf("%w: state mismatch", ErrBadState)
+	}
+	if subtle.ConstantTimeCompare([]byte(sessionBinding(session)), []byte(state.Session)) != 1 {
+		return fmt.Errorf("%w: started by another session", ErrBadState)
+	}
+	// A copy of the cookie verifies until it expires, so the state is
+	// single-use only because it is consumed here.
+	if !s.consumePending(state.State) {
+		return fmt.Errorf("%w: already used", ErrBadState)
+	}
+	if q.Get("error") != "" {
+		// error and error_description are Google-supplied text; neither is
+		// kept.
+		return ErrDenied
+	}
+	code := q.Get("code")
+	if code == "" {
+		return ErrNoCode
+	}
+
+	s.account.Lock()
+	defer s.account.Unlock()
+	token, err := s.oauth.Exchange(context.WithValue(ctx, oauth2.HTTPClient, s.client), code,
+		oauth2.VerifierOption(state.Verifier))
+	if err != nil {
+		return fmt.Errorf("gcal: %w", auth.ExchangeError(err))
+	}
+	if token.RefreshToken == "" {
+		return ErrNoRefreshToken
+	}
+	if err := checkScopes(token); err != nil {
+		return err
+	}
+	sealed, err := s.box.Encrypt([]byte(token.RefreshToken))
+	if err != nil {
+		return fmt.Errorf("gcal: seal refresh token: %w", err)
+	}
+	return s.store(ctx, sealed)
+}
+
+// addPending records state, started at now, as pending until the connect
+// cookie expires, and forgets expired ones.
+func (s *Service) addPending(state string, now time.Time) {
+	s.pendingMu.Lock()
+	defer s.pendingMu.Unlock()
+	for k, expires := range s.pending {
+		if !now.Before(expires) {
+			delete(s.pending, k)
+		}
+	}
+	s.pending[state] = now.Add(connectCookieTTL)
+}
+
+// consumePending removes state from the pending states, reporting whether
+// it was there.
+func (s *Service) consumePending(state string) bool {
+	s.pendingMu.Lock()
+	defer s.pendingMu.Unlock()
+	_, ok := s.pending[state]
+	delete(s.pending, state)
+	return ok
+}
+
+// checkScopes fails with ErrScopes unless token's granted scopes include
+// every scope in Scopes. Google lets the household untick a permission on
+// the consent screen and reports what was granted in "scope".
+func checkScopes(token *oauth2.Token) error {
+	granted, _ := token.Extra("scope").(string)
+	have := strings.Fields(granted)
+	for _, want := range Scopes {
+		if !slices.Contains(have, want) {
+			return ErrScopes
+		}
+	}
+	return nil
+}
+
+// store saves sealed as the refresh token with connected_at now, clearing
+// any earlier sync error.
+func (s *Service) store(ctx context.Context, sealed []byte) error {
+	return s.st.WithTx(ctx, func(tx *sql.Tx) error {
+		q := db.New(tx)
+		row, err := q.GetIntegrationsGoogle(ctx)
+		exists := err == nil
+		if err != nil && !errors.Is(err, sql.ErrNoRows) {
+			return fmt.Errorf("gcal: read Google integration: %w", err)
+		}
+		now := store.Timestamp{Time: s.now().UTC().Truncate(time.Millisecond)}.String()
+		created := now
+		if exists {
+			created = row.CreatedAt
+		}
+		if _, err := q.UpsertIntegrationsGoogle(ctx, db.UpsertIntegrationsGoogleParams{
+			RefreshTokenCt: sealed,
+			CalendarID:     row.CalendarID,
+			CalendarName:   row.CalendarName,
+			ConnectedAt:    now,
+			CreatedAt:      created,
+			UpdatedAt:      now,
+		}); err != nil {
+			return fmt.Errorf("gcal: save Google integration: %w", err)
+		}
+		return nil
+	})
+}
+
+// Disconnect revokes the stored refresh token at Google, then deletes the
+// connection. A token Google no longer knows (the household already removed
+// MealQuest's access in their Google account) counts as revoked. Any other
+// revoke failure keeps the connection so the household can retry.
+//
+// No calendar is chosen once disconnected, so the same transaction that
+// deletes the connection forgets every pushed event (forgetEvents): every
+// synced plan becomes changed, and the next push after connecting again and
+// choosing a calendar writes the whole week.
+func (s *Service) Disconnect(ctx context.Context) error {
+	s.account.Lock()
+	defer s.account.Unlock()
+	row, err := db.New(s.st.Reader).GetIntegrationsGoogle(ctx)
+	if errors.Is(err, sql.ErrNoRows) {
+		return ErrNotConnected
+	}
+	if err != nil {
+		return fmt.Errorf("gcal: read Google integration: %w", err)
+	}
+	token, err := s.box.Decrypt(row.RefreshTokenCt)
+	if err != nil {
+		return fmt.Errorf("gcal: open refresh token: %w", err)
+	}
+	if err := s.revoke(ctx, string(token)); err != nil {
+		return err
+	}
+	return s.st.WithTx(ctx, func(tx *sql.Tx) error {
+		q := db.New(tx)
+		if err := q.DeleteIntegrationsGoogle(ctx); err != nil {
+			return fmt.Errorf("gcal: delete Google integration: %w", err)
+		}
+		return forgetEvents(ctx, q, store.Timestamp{Time: s.now().UTC().Truncate(time.Millisecond)}.String())
+	})
+}
+
+// RevokeError is a revoke Google refused or that failed in transit. Its text
+// never holds the token or Google's response body.
+type RevokeError struct {
+	msg string
+}
+
+func (e *RevokeError) Error() string { return e.msg }
+
+// revoke revokes token at Google. HTTP 200 and HTTP 400 invalid_token (the
+// token is already revoked or expired) both leave it unusable.
+func (s *Service) revoke(ctx context.Context, token string) error {
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, s.revokeURL,
+		strings.NewReader(url.Values{"token": {token}}.Encode()))
+	if err != nil {
+		return fmt.Errorf("gcal: build revoke request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	resp, err := s.client.Do(req)
+	if err != nil {
+		var transport *url.Error
+		if errors.As(err, &transport) {
+			// The URL is dropped: after a refused redirect it is the
+			// Google-supplied Location.
+			return &RevokeError{msg: fmt.Sprintf("gcal: revoke request failed: %s: %v", transport.Op, transport.Err)}
+		}
+		return &RevokeError{msg: "gcal: revoke request failed"}
+	}
+	defer resp.Body.Close()
+	body, err := io.ReadAll(io.LimitReader(resp.Body, maxRevokeBody))
+	if err != nil {
+		return &RevokeError{msg: "gcal: read revoke response failed"}
+	}
+	if resp.StatusCode == http.StatusOK {
+		return nil
+	}
+	if resp.StatusCode == http.StatusBadRequest {
+		var reply struct {
+			Error string `json:"error"`
+		}
+		if json.Unmarshal(body, &reply) == nil && reply.Error == "invalid_token" {
+			return nil
+		}
+	}
+	return &RevokeError{msg: fmt.Sprintf("gcal: Google refused the revoke (HTTP %d)", resp.StatusCode)}
+}

internal/gcal/connect_test.go

@@ -0,0 +1,588 @@
+package gcal_test
+
+import (
+	"bytes"
+	"context"
+	"crypto/rand"
+	"database/sql"
+	"encoding/base64"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"slices"
+	"strings"
+	"testing"
+	"time"
+
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/auth"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/db"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal/gcaltest"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/secretbox"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/store"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/migrations"
+)
+
+const publicURL = "https://meals.example.com/app"
+
+var (
+	redirectURL = "https://meals.example.com" + gcal.CallbackPath
+	session     = auth.Session{Subject: "user-1", CSRFToken: "csrf-session-one"}
+	other       = auth.Session{Subject: "user-1", CSRFToken: "csrf-session-two"}
+)
+
+type harness struct {
+	svc    *gcal.Service
+	google *gcaltest.Google
+	st     *store.Store
+	box    *secretbox.Box
+	clock  time.Time
+}
+
+func newHarness(t *testing.T) *harness {
+	t.Helper()
+	ctx := context.Background()
+	st, err := store.Open(ctx, t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() {
+		if err := st.Close(); err != nil {
+			t.Error(err)
+		}
+	})
+	if err := store.Migrate(ctx, st.Writer, migrations.FS); err != nil {
+		t.Fatal(err)
+	}
+	key := make([]byte, secretbox.KeySize)
+	rand.Read(key)
+	box, err := secretbox.New(base64.StdEncoding.EncodeToString(key))
+	if err != nil {
+		t.Fatal(err)
+	}
+	pub, err := url.Parse(publicURL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	google := gcaltest.New(t, redirectURL)
+	svc, err := gcal.NewService(st, box, gcal.Config{
+		ClientID:     gcaltest.ClientID,
+		ClientSecret: gcaltest.ClientSecret,
+		PublicURL:    pub,
+		SecretKey:    []byte("server-secret-key"),
+		Endpoint:     google.Endpoint(),
+		RevokeURL:    google.RevokeURL(),
+		CalendarAPI:  google.CalendarAPI(),
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	h := &harness{svc: svc, google: google, st: st, box: box, clock: time.Date(2026, 10, 7, 18, 30, 0, 0, time.UTC)}
+	gcal.SetClock(svc, func() time.Time { return h.clock })
+	return h
+}
+
+// connect is a started connect: Google's consent URL and the connect
+// cookie.
+type connect struct {
+	consent *url.URL
+	cookie  *http.Cookie
+}
+
+func (h *harness) connect(t *testing.T, s auth.Session) connect {
+	t.Helper()
+	rec := httptest.NewRecorder()
+	raw, err := h.svc.Connect(rec, s)
+	if err != nil {
+		t.Fatal(err)
+	}
+	consent, err := url.Parse(raw)
+	if err != nil {
+		t.Fatal(err)
+	}
+	cookies := rec.Result().Cookies()
+	if len(cookies) != 1 {
+		t.Fatalf("Connect set %d cookies, want 1", len(cookies))
+	}
+	return connect{consent: consent, cookie: cookies[0]}
+}
+
+// callback completes c as session s with query, returning the error and the
+// recorder Complete wrote to.
+func (h *harness) callback(c connect, s auth.Session, query url.Values) (*httptest.ResponseRecorder, error) {
+	req := httptest.NewRequest(http.MethodGet, gcal.CallbackPath+"?"+query.Encode(), nil)
+	if c.cookie != nil {
+		req.AddCookie(c.cookie)
+	}
+	rec := httptest.NewRecorder()
+	return rec, h.svc.Complete(rec, req, s)
+}
+
+// consented is the query Google sends back after consent to c.
+func (h *harness) consented(c connect) url.Values {
+	q := c.consent.Query()
+	return url.Values{"state": {q.Get("state")}, "code": {h.google.Authorize(q.Get("code_challenge"))}}
+}
+
+func (h *harness) row(t *testing.T) (db.IntegrationsGoogle, bool) {
+	t.Helper()
+	row, err := db.New(h.st.Reader).GetIntegrationsGoogle(context.Background())
+	if errors.Is(err, sql.ErrNoRows) {
+		return db.IntegrationsGoogle{}, false
+	}
+	if err != nil {
+		t.Fatal(err)
+	}
+	return row, true
+}
+
+func TestConnectRedirectsToConsent(t *testing.T) {
+	t.Parallel()
+	h := newHarness(t)
+	c := h.connect(t, session)
+
+	if got, want := c.consent.Scheme+"://"+c.consent.Host+c.consent.Path, h.google.Endpoint().AuthURL; got != want {
+		t.Errorf("consent URL = %s, want %s", got, want)
+	}
+	q := c.consent.Query()
+	for name, want := range map[string]string{
+		"client_id":             gcaltest.ClientID,
+		"redirect_uri":          redirectURL,
+		"response_type":         "code",
+		"access_type":           "offline",
+		"prompt":                "consent",
+		"code_challenge_method": "S256",
+	} {
+		if got := q.Get(name); got != want {
+			t.Errorf("%s = %q, want %q", name, got, want)
+		}
+	}
+	if got := strings.Fields(q.Get("scope")); !slices.Equal(got, []string{
+		"https://www.googleapis.com/auth/calendar.events",
+		"https://www.googleapis.com/auth/calendar.calendarlist.readonly",
+	}) {
+		t.Errorf("scope = %q", q.Get("scope"))
+	}
+	if q.Get("state") == "" || q.Get("code_challenge") == "" {
+		t.Errorf("state %q, code_challenge %q: want both set", q.Get("state"), q.Get("code_challenge"))
+	}
+	if q.Get("client_secret") != "" || strings.Contains(c.consent.String(), gcaltest.ClientSecret) {
+		t.Error("consent URL carries the client secret")
+	}
+
+	ck := c.cookie
+	if ck.Name != "__Host-mealquest_google" || ck.Path != "/" || !ck.Secure || !ck.HttpOnly ||
+		ck.SameSite != http.SameSiteLaxMode || ck.MaxAge != 600 || ck.Domain != "" {
+		t.Errorf("connect cookie = %+v, want __Host-, Path=/, Secure, HttpOnly, Lax, 10 minutes", ck)
+	}
+	// Two connects never share a state.
+	if again := h.connect(t, session); again.consent.Query().Get("state") == q.Get("state") {
+		t.Error("two connects share a state")
+	}
+}
+
+func TestCompleteStoresSealedRefreshToken(t *testing.T) {
+	t.Parallel()
+	h := newHarness(t)
+	c := h.connect(t, session)
+	rec, err := h.callback(c, session, h.consented(c))
+	if err != nil {
+		t.Fatalf("Complete: %v", err)
+	}
+
+	row, ok := h.row(t)
+	if !ok {
+		t.Fatal("no integration stored")
+	}
+	if bytes.Contains(row.RefreshTokenCt, []byte(gcaltest.RefreshToken)) {
+		t.Error("refresh token stored in plain text")
+	}
+	plain, err := h.box.Decrypt(row.RefreshTokenCt)
+	if err != nil || string(plain) != gcaltest.RefreshToken {
+		t.Errorf("stored token opens to %q, %v; want the refresh token", plain, err)
+	}
+	if want := "2026-10-07T18:30:00.000Z"; row.ConnectedAt != want || row.CreatedAt != want || row.UpdatedAt != want {
+		t.Errorf("connected_at %q created_at %q updated_at %q, want %s", row.ConnectedAt, row.CreatedAt, row.UpdatedAt, want)
+	}
+	if row.CalendarID.Valid || row.CalendarName.Valid || row.LastSyncError.Valid {
+		t.Errorf("new connection has calendar or sync error: %+v", row)
+	}
+	assertCookieCleared(t, rec)
+	assertNoSecret(t, "response", rec.Body.String()+headerText(rec.Header()))
+}
+
+func TestReconnectReplacesTokenAndKeepsCalendar(t *testing.T) {
+	t.Parallel()
+	h := newHarness(t)
+	ctx := context.Background()
+	if _, err := db.New(h.st.Writer).UpsertIntegrationsGoogle(ctx, db.UpsertIntegrationsGoogleParams{
+		RefreshTokenCt: []byte("old sealed token"),
+		CalendarID:     sql.NullString{String: "family@group.calendar.google.com", Valid: true},
+		CalendarName:   sql.NullString{String: "Family", Valid: true},
+		ConnectedAt:    "2026-09-01T00:00:00.000Z",
+		LastSyncError:  sql.NullString{String: "token revoked", Valid: true},
+		CreatedAt:      "2026-09-01T00:00:00.000Z",
+		UpdatedAt:      "2026-09-01T00:00:00.000Z",
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	c := h.connect(t, session)
+	if _, err := h.callback(c, session, h.consented(c)); err != nil {
+		t.Fatalf("Complete: %v", err)
+	}
+	row, _ := h.row(t)
+	if plain, err := h.box.Decrypt(row.RefreshTokenCt); err != nil || string(plain) != gcaltest.RefreshToken {
+		t.Errorf("token after reconnect opens to %q, %v", plain, err)
+	}
+	if row.CalendarID.String != "family@group.calendar.google.com" || row.CalendarName.String != "Family" {
+		t.Errorf("calendar after reconnect = %v %v, want it kept", row.CalendarID, row.CalendarName)
+	}
+	if row.LastSyncError.Valid {
+		t.Errorf("last_sync_error = %q, want it cleared", row.LastSyncError.String)
+	}
+	if row.CreatedAt != "2026-09-01T00:00:00.000Z" || row.ConnectedAt != "2026-10-07T18:30:00.000Z" {
+		t.Errorf("created_at %q connected_at %q", row.CreatedAt, row.ConnectedAt)
+	}
+}
+
+func TestCompleteRefusesBadState(t *testing.T) {
+	t.Parallel()
+	for _, tc := range []struct {
+		name string
+		// edit changes the connect, the callback's session or its query.
+		edit func(t *testing.T, h *harness, c *connect, s *auth.Session, q url.Values)
+	}{
+		{"missing state", func(_ *testing.T, _ *harness, _ *connect, _ *auth.Session, q url.Values) { q.Del("state") }},
+		{"wrong state", func(_ *testing.T, _ *harness, _ *connect, _ *auth.Session, q url.Values) { q.Set("state", "forged") }},
+		{"no connect cookie", func(_ *testing.T, _ *harness, c *connect, _ *auth.Session, _ url.Values) { c.cookie = nil }},
+		{"tampered cookie", func(_ *testing.T, _ *harness, c *connect, _ *auth.Session, _ url.Values) {
+			c.cookie = &http.Cookie{Name: c.cookie.Name, Value: "x" + c.cookie.Value}
+		}},
+		{"another session", func(_ *testing.T, _ *harness, _ *connect, s *auth.Session, _ url.Values) { *s = other }},
+		{"expired", func(_ *testing.T, h *harness, _ *connect, _ *auth.Session, _ url.Values) {
+			h.clock = h.clock.Add(10 * time.Minute)
+		}},
+		{"state of another connect", func(t *testing.T, h *harness, _ *connect, _ *auth.Session, q url.Values) {
+			q.Set("state", h.connect(t, session).consent.Query().Get("state"))
+		}},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			h := newHarness(t)
+			c := h.connect(t, session)
+			s := session
+			q := h.consented(c)
+			tc.edit(t, h, &c, &s, q)
+
+			rec, err := h.callback(c, s, q)
+			if !errors.Is(err, gcal.ErrBadState) {
+				t.Fatalf("Complete error = %v, want ErrBadState", err)
+			}
+			if h.google.TokenCalls() != 0 {
+				t.Error("the code was exchanged despite the bad state")
+			}
+			if _, ok := h.row(t); ok {
+				t.Error("an integration was stored")
+			}
+			assertCookieCleared(t, rec)
+		})
+	}
+}
+
+// TestCompleteRefusesReplayedState presents a connect's cookie and state a
+// second time, with a second valid code from the same consent URL, as an
+// attacker holding a copy of the cookie could. The server refuses it,
+// whatever the browser did with the cleared cookie.
+func TestCompleteRefusesReplayedState(t *testing.T) {
+	t.Parallel()
+	h := newHarness(t)
+	c := h.connect(t, session)
+	if _, err := h.callback(c, session, h.consented(c)); err != nil {
+		t.Fatalf("Complete: %v", err)
+	}
+	stored, _ := h.row(t)
+
+	_, err := h.callback(c, session, h.consented(c))
+	if !errors.Is(err, gcal.ErrBadState) {
+		t.Fatalf("replayed Complete error = %v, want ErrBadState", err)
+	}
+	if got := h.google.TokenCalls(); got != 1 {
+		t.Errorf("token endpoint called %d times, want once: the replayed code was exchanged", got)
+	}
+	if row, _ := h.row(t); !bytes.Equal(row.RefreshTokenCt, stored.RefreshTokenCt) {
+		t.Error("the replay replaced the stored token")
+	}
+}
+
+func TestCompleteRefusesMissingRefreshToken(t *testing.T) {
+	t.Parallel()
+	h := newHarness(t)
+	h.google.OmitRefreshToken()
+	c := h.connect(t, session)
+	_, err := h.callback(c, session, h.consented(c))
+	if !errors.Is(err, gcal.ErrNoRefreshToken) {
+		t.Fatalf("Complete error = %v, want ErrNoRefreshToken", err)
+	}
+	if _, ok := h.row(t); ok {
+		t.Error("an integration was stored without a refresh token")
+	}
+	assertNoSecret(t, "error", err.Error())
+}
+
+func TestCompleteRefusesMissingScope(t *testing.T) {
+	t.Parallel()
+	h := newHarness(t)
+	h.google.GrantScope("https://www.googleapis.com/auth/calendar.calendarlist.readonly")
+	c := h.connect(t, session)
+	_, err := h.callback(c, session, h.consented(c))
+	if !errors.Is(err, gcal.ErrScopes) {
+		t.Fatalf("Complete error = %v, want ErrScopes", err)
+	}
+	if _, ok := h.row(t); ok {
+		t.Error("an integration was stored without calendar.events")
+	}
+}
+
+func TestCompleteDenied(t *testing.T) {
+	t.Parallel()
+	h := newHarness(t)
+	c := h.connect(t, session)
+	q := url.Values{"state": {c.consent.Query().Get("state")}, "error": {"access_denied"}}
+	if _, err := h.callback(c, session, q); !errors.Is(err, gcal.ErrDenied) {
+		t.Fatalf("Complete error = %v, want ErrDenied", err)
+	}
+	if h.google.TokenCalls() != 0 {
+		t.Error("token endpoint called after a denial")
+	}
+}
+
+func TestCompleteExchangeFailureIsRedacted(t *testing.T) {
+	t.Parallel()
+	h := newHarness(t)
+	h.google.FailToken(http.StatusBadRequest)
+	c := h.connect(t, session)
+	_, err := h.callback(c, session, h.consented(c))
+	if err == nil {
+		t.Fatal("Complete succeeded despite the token endpoint failing")
+	}
+	if !strings.Contains(err.Error(), "HTTP 400") {
+		t.Errorf("error = %v, want the status", err)
+	}
+	assertNoSecret(t, "error", err.Error())
+	if _, ok := h.row(t); ok {
+		t.Error("an integration was stored")
+	}
+}
+
+func TestDisconnectRevokesAndClears(t *testing.T) {
+	t.Parallel()
+	h := newHarness(t)
+	c := h.connect(t, session)
+	if _, err := h.callback(c, session, h.consented(c)); err != nil {
+		t.Fatal(err)
+	}
+	if err := h.svc.Disconnect(context.Background()); err != nil {
+		t.Fatalf("Disconnect: %v", err)
+	}
+	if got := h.google.Revoked(); !slices.Equal(got, []string{gcaltest.RefreshToken}) {
+		t.Errorf("revoked %q, want the refresh token", got)
+	}
+	if _, ok := h.row(t); ok {
+		t.Error("integration still stored after disconnect")
+	}
+	if err := h.svc.Disconnect(context.Background()); !errors.Is(err, gcal.ErrNotConnected) {
+		t.Errorf("second Disconnect = %v, want ErrNotConnected", err)
+	}
+}
+
+// TestDisconnectRacingReconnect drives a disconnect and a reconnect into
+// each other at Google, with distinct tokens. However they interleave, the
+// end state is consistent: disconnected, or connected with a token Google
+// has not revoked.
+func TestDisconnectRacingReconnect(t *testing.T) {
+	t.Parallel()
+	for _, tc := range []struct {
+		name string
+		// hold stops the request the other operation must not slip past.
+		hold func(*gcaltest.Google) (<-chan struct{}, func())
+		// first is held at Google while second runs.
+		first, second func(h *harness, c connect, q url.Values) error
+	}{
+		{
+			// The disconnect has read the stored token and is revoking it
+			// when the reconnect would store a new one.
+			name:   "reconnect during revoke",
+			hold:   (*gcaltest.Google).HoldRevoke,
+			first:  disconnect,
+			second: reconnect,
+		},
+		{
+			// The reconnect's new token is issued but not yet stored when
+			// the disconnect would revoke the old one.
+			name:   "disconnect during exchange",
+			hold:   (*gcaltest.Google).HoldToken,
+			first:  reconnect,
+			second: disconnect,
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			h := newHarness(t)
+			first := h.connect(t, session)
+			if _, err := h.callback(first, session, h.consented(first)); err != nil {
+				t.Fatal(err)
+			}
+			c := h.connect(t, session)
+			q := h.consented(c)
+
+			arrived, release := tc.hold(h.google)
+			defer release()
+			firstDone := make(chan error, 1)
+			go func() { firstDone <- tc.first(h, c, q) }()
+			<-arrived
+			secondDone := make(chan error, 1)
+			go func() { secondDone <- tc.second(h, c, q) }()
+			// Let the second operation run as far as it can while the first
+			// is held at Google: to the end when nothing serializes them.
+			select {
+			case err := <-secondDone:
+				secondDone <- err
+			case <-time.After(500 * time.Millisecond):
+			}
+			release()
+			for _, done := range []chan error{firstDone, secondDone} {
+				if err := <-done; err != nil {
+					t.Logf("operation: %v", err)
+				}
+			}
+
+			row, ok := h.row(t)
+			if !ok {
+				return
+			}
+			plain, err := h.box.Decrypt(row.RefreshTokenCt)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if !h.google.Live(string(plain)) {
+				t.Errorf("stored as connected with a revoked token (Google revoked %d tokens)", len(h.google.Revoked()))
+			}
+		})
+	}
+}
+
+func disconnect(h *harness, _ connect, _ url.Values) error {
+	return h.svc.Disconnect(context.Background())
+}
+
+func reconnect(h *harness, c connect, q url.Values) error {
+	_, err := h.callback(c, session, q)
+	return err
+}
+
+func TestDisconnectTokenAlreadyRevokedAtGoogle(t *testing.T) {
+	t.Parallel()
+	h := newHarness(t)
+	c := h.connect(t, session)
+	if _, err := h.callback(c, session, h.consented(c)); err != nil {
+		t.Fatal(err)
+	}
+	h.google.AnswerRevoke(http.StatusBadRequest, `{"error":"invalid_token","error_description":"Token expired or revoked"}`)
+	if err := h.svc.Disconnect(context.Background()); err != nil {
+		t.Fatalf("Disconnect: %v", err)
+	}
+	if _, ok := h.row(t); ok {
+		t.Error("integration still stored")
+	}
+}
+
+func TestDisconnectRevokeFailureKeepsConnection(t *testing.T) {
+	t.Parallel()
+	for _, status := range []int{http.StatusBadRequest, http.StatusServiceUnavailable} {
+		h := newHarness(t)
+		c := h.connect(t, session)
+		if _, err := h.callback(c, session, h.consented(c)); err != nil {
+			t.Fatal(err)
+		}
+		h.google.AnswerRevoke(status, "")
+		err := h.svc.Disconnect(context.Background())
+		var revoke *gcal.RevokeError
+		if !errors.As(err, &revoke) {
+			t.Fatalf("HTTP %d: Disconnect error = %v, want *RevokeError", status, err)
+		}
+		assertNoSecret(t, "error", err.Error())
+		if _, ok := h.row(t); !ok {
+			t.Errorf("HTTP %d: connection cleared although Google did not revoke", status)
+		}
+	}
+}
+
+func TestDisconnectNotConnected(t *testing.T) {
+	t.Parallel()
+	h := newHarness(t)
+	if err := h.svc.Disconnect(context.Background()); !errors.Is(err, gcal.ErrNotConnected) {
+		t.Fatalf("Disconnect = %v, want ErrNotConnected", err)
+	}
+	if len(h.google.Revoked()) != 0 {
+		t.Error("revoke called with nothing connected")
+	}
+}
+
+func TestNewServiceRequiresConfig(t *testing.T) {
+	t.Parallel()
+	h := newHarness(t)
+	pub, _ := url.Parse(publicURL)
+	valid := gcal.Config{
+		ClientID: "id", ClientSecret: "secret", PublicURL: pub, SecretKey: []byte("k"),
+		Endpoint: gcal.GoogleEndpoint, RevokeURL: gcal.GoogleRevokeURL, CalendarAPI: gcal.GoogleCalendarAPI,
+	}
+	if _, err := gcal.NewService(h.st, h.box, valid); err != nil {
+		t.Fatalf("valid config: %v", err)
+	}
+	for name, edit := range map[string]func(*gcal.Config){
+		"client ID":     func(c *gcal.Config) { c.ClientID = "" },
+		"client secret": func(c *gcal.Config) { c.ClientSecret = "" },
+		"public URL":    func(c *gcal.Config) { c.PublicURL = nil },
+		"secret key":    func(c *gcal.Config) { c.SecretKey = nil },
+		"token URL":     func(c *gcal.Config) { c.Endpoint.TokenURL = "" },
+		"revoke URL":    func(c *gcal.Config) { c.RevokeURL = "" },
+		"Calendar API":  func(c *gcal.Config) { c.CalendarAPI = "" },
+	} {
+		cfg := valid
+		edit(&cfg)
+		if _, err := gcal.NewService(h.st, h.box, cfg); err == nil {
+			t.Errorf("NewService accepted a config without the %s", name)
+		}
+	}
+}
+
+func assertCookieCleared(t *testing.T, rec *httptest.ResponseRecorder) {
+	t.Helper()
+	for _, c := range rec.Result().Cookies() {
+		if c.Name == "__Host-mealquest_google" && c.MaxAge < 0 {
+			return
+		}
+	}
+	t.Error("connect cookie not cleared")
+}
+
+// assertNoSecret fails when text holds the refresh token, the access token
+// or the client secret.
+func assertNoSecret(t *testing.T, what, text string) {
+	t.Helper()
+	for _, secret := range []string{gcaltest.RefreshToken, gcaltest.AccessToken, gcaltest.ClientSecret} {
+		if strings.Contains(text, secret) {
+			t.Errorf("%s contains a secret: %s", what, text)
+		}
+	}
+}
+
+func headerText(h http.Header) string {
+	var b strings.Builder
+	for k, vs := range h {
+		b.WriteString(k + ": " + strings.Join(vs, ", ") + "\n")
+	}
+	return b.String()
+}

internal/gcal/events.go

@@ -0,0 +1,213 @@
+package gcal
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"regexp"
+	"time"
+)
+
+// maxEventBody caps how much of an events response is read.
+const maxEventBody = 64 << 10
+
+var (
+	// ErrNoCalendar means Google Calendar is connected but no calendar is
+	// chosen to push to.
+	ErrNoCalendar = errors.New("gcal: no calendar is chosen for Push to Calendar")
+	// ErrCalendarUnavailable means the chosen calendar was deleted or the
+	// connected account can no longer add events to it. Such a calendar
+	// cannot be chosen again; the household must choose another.
+	ErrCalendarUnavailable = errors.New("gcal: the chosen calendar was deleted or MealQuest can no longer add dinners to it")
+)
+
+// Google's rule for a client-chosen event id: base32hex characters
+// (lowercase a-v and 0-9), 5 to 1024 of them.
+var eventIDChars = regexp.MustCompile(`^[a-v0-9]+$`)
+
+const (
+	minEventID = 5
+	maxEventID = 1024
+)
+
+// Event is one event to write to the chosen calendar.
+type Event struct {
+	// ID is the event's id, chosen by the caller so that writing the same
+	// event again updates it; it must satisfy Google's id rule.
+	ID          string
+	Summary     string
+	Description string
+	Start, End  time.Time
+	// TimeZone is the IANA zone the event is in, such as America/New_York.
+	TimeZone string
+}
+
+func (e Event) validate() error {
+	switch {
+	case len(e.ID) < minEventID, len(e.ID) > maxEventID, !eventIDChars.MatchString(e.ID):
+		return fmt.Errorf("gcal: event id %q is not 5 to 1024 base32hex characters", e.ID)
+	case e.Summary == "":
+		return fmt.Errorf("gcal: event %s has no summary", e.ID)
+	case !e.End.After(e.Start):
+		return fmt.Errorf("gcal: event %s does not end after it starts", e.ID)
+	case e.TimeZone == "":
+		return fmt.Errorf("gcal: event %s has no time zone", e.ID)
+	}
+	return nil
+}
+
+// eventBody is an event as the Calendar API takes it.
+type eventBody struct {
+	ID          string    `json:"id"`
+	Status      string    `json:"status"`
+	Summary     string    `json:"summary"`
+	Description string    `json:"description"`
+	Start       eventTime `json:"start"`
+	End         eventTime `json:"end"`
+}
+
+type eventTime struct {
+	DateTime string `json:"dateTime"`
+	TimeZone string `json:"timeZone"`
+}
+
+// PushEvents writes events, in order, to the chosen calendar: each is
+// inserted with its id, and an id Google already has (HTTP 409, which
+// includes an event deleted in Calendar) is updated in place instead, so
+// writing an event again never adds a second one. It stops at the first
+// failure; the events before it stay written, and writing them all again
+// is safe. Nothing connected is ErrNotConnected, no calendar chosen is
+// ErrNoCalendar, a chosen calendar that was deleted or is no longer
+// writable is ErrCalendarUnavailable, a grant Google no longer accepts is
+// ErrReconnect, and any other Google failure is a *CalendarError.
+//
+// Once every event is written, PushEvents returns record(), which the
+// caller uses to store what it pushed. record runs under the same hold of
+// the account as the writes, so the chosen calendar cannot change between
+// them; it is not run when a write fails.
+func (s *Service) PushEvents(ctx context.Context, events []Event, record func() error) error {
+	if len(events) == 0 {
+		return errors.New("gcal: no events to push")
+	}
+	for _, e := range events {
+		if err := e.validate(); err != nil {
+			return err
+		}
+	}
+	s.account.Lock()
+	defer s.account.Unlock()
+	row, err := s.connection(ctx)
+	if err != nil {
+		return err
+	}
+	if !row.CalendarID.Valid || row.CalendarID.String == "" {
+		return ErrNoCalendar
+	}
+	access, err := s.accessToken(ctx, row)
+	if err != nil {
+		return err
+	}
+	base := s.calendarAPI + "/calendars/" + url.PathEscape(row.CalendarID.String) + "/events"
+	for _, e := range events {
+		if err := s.writeEvent(ctx, access, base, e); err != nil {
+			return err
+		}
+	}
+	return record()
+}
+
+// writeEvent inserts e at base, the chosen calendar's events collection,
+// and updates it when Google already has its id.
+func (s *Service) writeEvent(ctx context.Context, access, base string, e Event) error {
+	body, err := json.Marshal(eventBody{
+		ID:          e.ID,
+		Status:      "confirmed",
+		Summary:     e.Summary,
+		Description: e.Description,
+		Start:       eventTime{DateTime: e.Start.Format(time.RFC3339), TimeZone: e.TimeZone},
+		End:         eventTime{DateTime: e.End.Format(time.RFC3339), TimeZone: e.TimeZone},
+	})
+	if err != nil {
+		return fmt.Errorf("gcal: encode event %s: %w", e.ID, err)
+	}
+	status, err := s.eventRequest(ctx, access, http.MethodPost, base, body)
+	if err != nil {
+		return err
+	}
+	if status != http.StatusConflict {
+		return nil
+	}
+	// The status "confirmed" in the body restores an event deleted in
+	// Calendar, which Google keeps as cancelled under the same id.
+	_, err = s.eventRequest(ctx, access, http.MethodPut, base+"/"+url.PathEscape(e.ID), body)
+	return err
+}
+
+// eventRequest sends an event insert (POST) or update (PUT) and returns
+// HTTP 200 or, for an insert, 409; every other answer is an error.
+func (s *Service) eventRequest(ctx context.Context, access, method, target string, body []byte) (int, error) {
+	what := "event insert"
+	if method == http.MethodPut {
+		what = "event update"
+	}
+	req, err := http.NewRequestWithContext(ctx, method, target, bytes.NewReader(body))
+	if err != nil {
+		return 0, fmt.Errorf("gcal: build %s request: %w", what, err)
+	}
+	req.Header.Set("Authorization", "Bearer "+access)
+	req.Header.Set("Content-Type", "application/json")
+	resp, err := s.client.Do(req)
+	if err != nil {
+		var transport *url.Error
+		if errors.As(err, &transport) {
+			// The URL is dropped: after a refused redirect it is the
+			// Google-supplied Location.
+			return 0, &CalendarError{msg: fmt.Sprintf("gcal: %s request failed: %s: %v", what, transport.Op, transport.Err)}
+		}
+		return 0, &CalendarError{msg: fmt.Sprintf("gcal: %s request failed", what)}
+	}
+	defer resp.Body.Close()
+	reply, err := io.ReadAll(io.LimitReader(resp.Body, maxEventBody))
+	if err != nil {
+		return 0, &CalendarError{msg: fmt.Sprintf("gcal: read %s response failed", what)}
+	}
+	switch {
+	case resp.StatusCode == http.StatusOK:
+		return http.StatusOK, nil
+	case resp.StatusCode == http.StatusConflict && method == http.MethodPost:
+		return http.StatusConflict, nil
+	case resp.StatusCode == http.StatusUnauthorized:
+		return 0, ErrReconnect
+	case resp.StatusCode == http.StatusNotFound && method == http.MethodPost,
+		resp.StatusCode == http.StatusForbidden && errorReason(reply) == "requiredAccessLevel":
+		// An insert into a deleted calendar, or one the account no longer
+		// sees, is not found; a write to one it can only read is
+		// requiredAccessLevel. An update not found is the event missing
+		// from the calendar after Google reported its id taken, which
+		// says nothing about the calendar.
+		return 0, ErrCalendarUnavailable
+	}
+	return 0, &CalendarError{msg: fmt.Sprintf("gcal: Google refused the %s (HTTP %d)", what, resp.StatusCode)}
+}
+
+// errorReason is the reason of the first error in a Calendar API error
+// body, or "" when there is none. Only the reason is read; the rest of
+// Google's text is never kept.
+func errorReason(body []byte) string {
+	var reply struct {
+		Error struct {
+			Errors []struct {
+				Reason string `json:"reason"`
+			} `json:"errors"`
+		} `json:"error"`
+	}
+	if json.Unmarshal(body, &reply) != nil || len(reply.Error.Errors) == 0 {
+		return ""
+	}
+	return reply.Error.Errors[0].Reason
+}

internal/gcal/events_test.go

@@ -0,0 +1,189 @@
+package gcal_test
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"strings"
+	"testing"
+	"time"
+
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal"
+)
+
+// chosen is a harness connected with dinners chosen as the calendar to
+// push to.
+func chosen(t *testing.T) *harness {
+	t.Helper()
+	h := connected(t)
+	if _, err := h.svc.SelectCalendar(context.Background(), dinners.ID); err != nil {
+		t.Fatal(err)
+	}
+	return h
+}
+
+// noRecord is a PushEvents record that stores nothing.
+func noRecord() error { return nil }
+
+// event is a valid event with id.
+func event(id string) gcal.Event {
+	start := time.Date(2026, 10, 12, 21, 30, 0, 0, time.UTC)
+	return gcal.Event{ID: id, Summary: "Dinner: Beef Chili", Description: "Beef Chili",
+		Start: start, End: start.Add(time.Hour), TimeZone: "America/New_York"}
+}
+
+func TestPushEventsInsertsThenUpdates(t *testing.T) {
+	t.Parallel()
+	h := chosen(t)
+	if err := h.svc.PushEvents(context.Background(), []gcal.Event{event("abcde0"), event("abcde1")}, noRecord); err != nil {
+		t.Fatalf("PushEvents: %v", err)
+	}
+	renamed := event("abcde0")
+	renamed.Summary = "Dinner: Pot Roast"
+	if err := h.svc.PushEvents(context.Background(), []gcal.Event{renamed}, noRecord); err != nil {
+		t.Fatalf("PushEvents again: %v", err)
+	}
+	if inserts, updates := h.google.EventWrites(); inserts != 2 || updates != 1 {
+		t.Errorf("%d inserts and %d updates, want 2 and 1", inserts, updates)
+	}
+	events := h.google.Events(dinners.ID)
+	if len(events) != 2 || events["abcde0"].Summary != "Dinner: Pot Roast" {
+		t.Errorf("events = %+v", events)
+	}
+	if got := events["abcde1"].Start.DateTime; got != "2026-10-12T21:30:00Z" {
+		t.Errorf("start = %s, want the instant as given", got)
+	}
+}
+
+func TestPushEventsRefusesInvalidEvents(t *testing.T) {
+	t.Parallel()
+	h := chosen(t)
+	before := h.google.TokenCalls()
+	for name, edit := range map[string]func(*gcal.Event){
+		"uppercase id":      func(e *gcal.Event) { e.ID = "ABCDE" },
+		"id outside a-v":    func(e *gcal.Event) { e.ID = "abcdw" },
+		"id too short":      func(e *gcal.Event) { e.ID = "abcd" },
+		"id too long":       func(e *gcal.Event) { e.ID = strings.Repeat("a", 1025) },
+		"no summary":        func(e *gcal.Event) { e.Summary = "" },
+		"ends as it starts": func(e *gcal.Event) { e.End = e.Start },
+		"no time zone":      func(e *gcal.Event) { e.TimeZone = "" },
+	} {
+		ev := event("abcde")
+		edit(&ev)
+		if err := h.svc.PushEvents(context.Background(), []gcal.Event{event("abcde0"), ev}, noRecord); err == nil {
+			t.Errorf("%s: PushEvents succeeded", name)
+		}
+	}
+	if err := h.svc.PushEvents(context.Background(), nil, noRecord); err == nil {
+		t.Error("PushEvents of no events succeeded")
+	}
+	if err := h.svc.PushEvents(context.Background(), []gcal.Event{event(strings.Repeat("v", 1024))}, noRecord); err != nil {
+		t.Errorf("PushEvents of a 1024-character id: %v", err)
+	}
+	if inserts, _ := h.google.EventWrites(); inserts != 1 {
+		t.Errorf("%d events inserted, want only the valid one", inserts)
+	}
+	if n := h.google.TokenCalls() - before; n != 1 {
+		t.Errorf("token endpoint called %d times, want once, for the valid push", n)
+	}
+}
+
+func TestPushEventsGrantNoLongerAccepted(t *testing.T) {
+	t.Parallel()
+	h := chosen(t)
+	h.google.FailEventWrite(1, http.StatusUnauthorized)
+	err := h.svc.PushEvents(context.Background(), []gcal.Event{event("abcde")}, func() error {
+		t.Error("record ran after a failed write")
+		return nil
+	})
+	if !errors.Is(err, gcal.ErrReconnect) {
+		t.Fatalf("PushEvents = %v, want ErrReconnect", err)
+	}
+	assertNoSecret(t, "error", err.Error())
+	if _, ok := h.row(t); !ok {
+		t.Error("a refused grant forgot the connection")
+	}
+}
+
+func TestPushEventsGoogleFailureIsRedacted(t *testing.T) {
+	t.Parallel()
+	for name, n := range map[string]int{"insert": 1, "update": 2} {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+			h := chosen(t)
+			if name == "update" {
+				if err := h.svc.PushEvents(context.Background(), []gcal.Event{event("abcde")}, noRecord); err != nil {
+					t.Fatal(err)
+				}
+			}
+			// The fake's failure body quotes the access token.
+			h.google.FailEventWrite(n, http.StatusInternalServerError)
+			err := h.svc.PushEvents(context.Background(), []gcal.Event{event("abcde")}, noRecord)
+			var calendar *gcal.CalendarError
+			if !errors.As(err, &calendar) {
+				t.Fatalf("PushEvents = %v, want *CalendarError", err)
+			}
+			if !strings.Contains(err.Error(), "event "+name) || !strings.Contains(err.Error(), "HTTP 500") {
+				t.Errorf("error = %q, want the failed %s and its status", err, name)
+			}
+			assertNoSecret(t, "error", err.Error())
+		})
+	}
+}
+
+// TestPushEventsHoldsTheAccount holds an event write at Google while a
+// disconnect starts: the disconnect waits for the push, so it never
+// revokes the token the push is using.
+func TestPushEventsHoldsTheAccount(t *testing.T) {
+	t.Parallel()
+	h := chosen(t)
+	arrived, release := h.google.HoldEvents()
+	defer release()
+	pushed := make(chan error, 1)
+	go func() { pushed <- h.svc.PushEvents(context.Background(), []gcal.Event{event("abcde")}, noRecord) }()
+	<-arrived
+	disconnected := make(chan error, 1)
+	go func() { disconnected <- h.svc.Disconnect(context.Background()) }()
+	select {
+	case err := <-disconnected:
+		t.Fatalf("Disconnect finished (%v) while a push was at Google", err)
+	case <-time.After(200 * time.Millisecond):
+	}
+	if n := len(h.google.Revoked()); n != 0 {
+		t.Fatalf("revoked %d tokens while a push was at Google", n)
+	}
+	release()
+	if err := <-pushed; err != nil {
+		t.Errorf("PushEvents: %v", err)
+	}
+	if err := <-disconnected; err != nil {
+		t.Errorf("Disconnect: %v", err)
+	}
+}
+
+// TestPushEventsRecordsWhileTheCalendarIsChosen chooses another calendar
+// while a push records: the choice waits for the record, so a push never
+// records events on a calendar no longer chosen.
+func TestPushEventsRecordsWhileTheCalendarIsChosen(t *testing.T) {
+	t.Parallel()
+	h := chosen(t)
+	selected := make(chan error, 1)
+	err := h.svc.PushEvents(context.Background(), []gcal.Event{event("abcde")}, func() error {
+		go func() {
+			_, err := h.svc.SelectCalendar(context.Background(), family.ID)
+			selected <- err
+		}()
+		select {
+		case err := <-selected:
+			t.Errorf("SelectCalendar finished (%v) while a push was recording", err)
+		case <-time.After(200 * time.Millisecond):
+		}
+		return nil
+	})
+	if err != nil {
+		t.Fatalf("PushEvents: %v", err)
+	}
+	if err := <-selected; err != nil {
+		t.Errorf("SelectCalendar: %v", err)
+	}
+}

internal/gcal/export_test.go

@@ -0,0 +1,6 @@
+package gcal
+
+import "time"
+
+// SetClock replaces s's clock.
+func SetClock(s *Service, now func() time.Time) { s.now = now }

internal/gcal/gcaltest/gcaltest.go

@@ -0,0 +1,699 @@
+// Package gcaltest provides a fake Google OAuth server and Calendar API for
+// tests of the Google Calendar connection: a token endpoint that checks the
+// client, the redirect URI and PKCE, issues a distinct refresh token per
+// exchange and trades a live refresh token for an access token; a revoke
+// endpoint that, like Google's, revokes the whole grant: every token issued
+// so far; a calendarList endpoint that requires a live grant's access
+// token; and events insert and update endpoints that, like Google's, keep
+// each calendar's events by id, answer an insert of an id the calendar
+// already has (even a cancelled event's) with HTTP 409, and refuse a
+// calendar not listed (404) or not writable (403 requiredAccessLevel). It
+// never touches the network beyond its own httptest server.
+package gcaltest
+
+import (
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"slices"
+	"strconv"
+	"strings"
+	"sync"
+	"testing"
+
+	"golang.org/x/oauth2"
+
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/auth"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal"
+)
+
+// Fixed credentials and tokens the fake issues and expects. The first
+// exchange issues RefreshToken; exchange n after it issues RefreshToken
+// followed by "-n", so every issued refresh token contains RefreshToken. Every
+// exchange and refresh issues AccessToken.
+const (
+	ClientID     = "mealquest-test.apps.googleusercontent.com"
+	ClientSecret = "google-client-s3cret-4f1c"
+	RefreshToken = "1//google-refresh-t0ken-9a8b7c"
+	AccessToken  = "ya29.google-access-t0ken-5d6e"
+)
+
+// Google is the fake. Its exported fields script the next responses; set
+// them before the request they affect.
+type Google struct {
+	Server *httptest.Server
+	// RedirectURL is the redirect URI the token endpoint requires.
+	RedirectURL string
+
+	mu sync.Mutex
+	// omitRefresh leaves refresh_token out of the token response.
+	omitRefresh bool
+	// scope is the token response's granted scopes.
+	scope string
+	// tokenStatus, when not 200, fails the token endpoint with a body that
+	// quotes the refresh token and client secret.
+	tokenStatus int
+	// revokeStatus and revokeBody answer the revoke endpoint; revokeBody
+	// quotes the token when revokeStatus is not 200 or 400.
+	revokeStatus int
+	revokeBody   string
+	codes        map[string]string // code -> PKCE challenge
+	tokenCalls   int
+	revoked      []string
+	// issued is every refresh token issued, in order; dead is those a
+	// revoke has invalidated.
+	issued []string
+	dead   map[string]bool
+	// tokenHold, revokeHold and calendarHold, when set, stop the next
+	// request to that endpoint.
+	tokenHold, revokeHold, calendarHold *hold
+	// calendars is what the calendarList endpoint lists, pageSize entries
+	// to a page (all of them when 0).
+	calendars []Calendar
+	pageSize  int
+	// calendarStatus, when not 200, fails the calendarList endpoint with a
+	// body that quotes the access token.
+	calendarStatus int
+	calendarCalls  int
+	// events holds each calendar's events by id.
+	events map[string]map[string]Event
+	// inserts and updates count the events created and updated.
+	inserts, updates int
+	// eventWrites counts the requests that reached the events endpoints;
+	// failWrite, when not 0, fails the request that makes it that count
+	// with failStatus and a body that quotes the access token.
+	eventWrites, failWrite, failStatus int
+	// eventHold, when set, stops the next events request.
+	eventHold *hold
+}
+
+// Event is an event as the fake keeps it: what MealQuest sent.
+type Event struct {
+	ID          string    `json:"id"`
+	Status      string    `json:"status"`
+	Summary     string    `json:"summary"`
+	Description string    `json:"description"`
+	Start       EventTime `json:"start"`
+	End         EventTime `json:"end"`
+}
+
+// EventTime is an event's start or end.
+type EventTime struct {
+	DateTime string `json:"dateTime"`
+	TimeZone string `json:"timeZone"`
+}
+
+// Calendar is one calendarList entry. The fake answers each with Google's
+// other fields too, so tests can check that nothing beyond id, summary,
+// primary and accessRole reaches the household.
+type Calendar struct {
+	ID              string
+	Summary         string
+	Primary         bool
+	AccessRole      string
+	Description     string
+	SummaryOverride string
+}
+
+// hold stops one request: arrived is closed when it arrives, and it goes on
+// once release is closed.
+type hold struct {
+	arrived, release chan struct{}
+}
+
+// New starts a fake Google that requires redirectURL at its token endpoint.
+// It grants every scope in gcal.Scopes with a refresh token by default.
+func New(t *testing.T, redirectURL string) *Google {
+	t.Helper()
+	g := &Google{
+		RedirectURL:    redirectURL,
+		scope:          strings.Join(gcal.Scopes, " "),
+		tokenStatus:    http.StatusOK,
+		revokeStatus:   http.StatusOK,
+		calendarStatus: http.StatusOK,
+		codes:          map[string]string{},
+		dead:           map[string]bool{},
+		events:         map[string]map[string]Event{},
+	}
+	mux := http.NewServeMux()
+	mux.HandleFunc("POST /token", g.token)
+	mux.HandleFunc("POST /revoke", g.revoke)
+	mux.HandleFunc("GET /calendar/v3/users/me/calendarList", g.calendarList)
+	mux.HandleFunc("POST /calendar/v3/calendars/{calendar}/events", g.insertEvent)
+	mux.HandleFunc("PUT /calendar/v3/calendars/{calendar}/events/{event}", g.updateEvent)
+	g.Server = httptest.NewServer(mux)
+	t.Cleanup(g.Server.Close)
+	return g
+}
+
+// Endpoint is the fake's authorization and token endpoint, with Google's
+// client authentication style.
+func (g *Google) Endpoint() oauth2.Endpoint {
+	return oauth2.Endpoint{
+		AuthURL:   g.Server.URL + "/auth",
+		TokenURL:  g.Server.URL + "/token",
+		AuthStyle: gcal.GoogleEndpoint.AuthStyle,
+	}
+}
+
+// RevokeURL is the fake's revocation endpoint.
+func (g *Google) RevokeURL() string { return g.Server.URL + "/revoke" }
+
+// CalendarAPI is the fake's Calendar API base URL.
+func (g *Google) CalendarAPI() string { return g.Server.URL + "/calendar/v3" }
+
+// Authorize plays the consent screen for an authorization request with PKCE
+// challenge and returns the code Google would send back.
+func (g *Google) Authorize(challenge string) string {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	code := fmt.Sprintf("code-%d", len(g.codes)+1)
+	g.codes[code] = challenge
+	return code
+}
+
+// Connect connects svc to the fake as a household completing the consent
+// screen does. svc must use the fake's endpoints and redirect URL.
+func (g *Google) Connect(t *testing.T, svc *gcal.Service) {
+	t.Helper()
+	session := auth.Session{Subject: "gcaltest", CSRFToken: "gcaltest-session"}
+	started := httptest.NewRecorder()
+	raw, err := svc.Connect(started, session)
+	if err != nil {
+		t.Fatal(err)
+	}
+	consent, err := url.Parse(raw)
+	if err != nil {
+		t.Fatal(err)
+	}
+	q := url.Values{
+		"state": {consent.Query().Get("state")},
+		"code":  {g.Authorize(consent.Query().Get("code_challenge"))},
+	}
+	req := httptest.NewRequest(http.MethodGet, gcal.CallbackPath+"?"+q.Encode(), nil)
+	for _, c := range started.Result().Cookies() {
+		req.AddCookie(c)
+	}
+	if err := svc.Complete(httptest.NewRecorder(), req, session); err != nil {
+		t.Fatalf("connect: %v", err)
+	}
+}
+
+// OmitRefreshToken makes the token endpoint answer without a refresh token,
+// as Google does when it reuses an earlier grant.
+func (g *Google) OmitRefreshToken() {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.omitRefresh = true
+}
+
+// GrantScope sets the scopes the token endpoint reports as granted.
+func (g *Google) GrantScope(scope string) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.scope = scope
+}
+
+// FailToken makes the token endpoint answer status with a body that quotes
+// the refresh token and client secret.
+func (g *Google) FailToken(status int) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.tokenStatus = status
+}
+
+// AnswerRevoke makes the revoke endpoint answer status with body. A body of
+// "" with a status other than 200 quotes the token it was sent.
+func (g *Google) AnswerRevoke(status int, body string) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.revokeStatus, g.revokeBody = status, body
+}
+
+// RevokeGrant revokes every token issued so far, as the household removing
+// MealQuest's access in their Google account does.
+func (g *Google) RevokeGrant() {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	for _, t := range g.issued {
+		g.dead[t] = true
+	}
+}
+
+// SetCalendars makes the calendarList endpoint list cals, pageSize to a
+// page (all on one page when 0).
+func (g *Google) SetCalendars(pageSize int, cals ...Calendar) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.calendars, g.pageSize = slices.Clone(cals), pageSize
+}
+
+// FailCalendarList makes the calendarList endpoint answer status with a
+// body that quotes the access token.
+func (g *Google) FailCalendarList(status int) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.calendarStatus = status
+}
+
+// CalendarCalls is how many requests reached the calendarList endpoint.
+func (g *Google) CalendarCalls() int {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	return g.calendarCalls
+}
+
+// HoldCalendarList stops the next calendarList request before it is
+// answered. It returns a channel closed when the request arrives and the
+// function that lets it go on.
+func (g *Google) HoldCalendarList() (arrived <-chan struct{}, release func()) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.calendarHold = newHold()
+	return g.calendarHold.arrived, g.calendarHold.releaseFunc()
+}
+
+// Events returns the events of calendar, by id.
+func (g *Google) Events(calendar string) map[string]Event {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	out := map[string]Event{}
+	for id, e := range g.events[calendar] {
+		out[id] = e
+	}
+	return out
+}
+
+// EventWrites returns how many events were inserted and how many updated.
+func (g *Google) EventWrites() (inserts, updates int) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	return g.inserts, g.updates
+}
+
+// ResetEventWrites zeroes the insert and update counts.
+func (g *Google) ResetEventWrites() {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.inserts, g.updates = 0, 0
+}
+
+// CancelEvent marks event id of calendar cancelled, as deleting it in
+// Google Calendar does: Google keeps the id.
+func (g *Google) CancelEvent(calendar, id string) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	e := g.events[calendar][id]
+	e.Status = "cancelled"
+	g.events[calendar][id] = e
+}
+
+// FailEventWrite makes the nth request to the events endpoints from now
+// (1 for the next) answer status with a body that quotes the access token.
+func (g *Google) FailEventWrite(n, status int) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.failWrite, g.failStatus = g.eventWrites+n, status
+}
+
+// HoldEvents stops the next request to the events endpoints before it is
+// answered. It returns a channel closed when the request arrives and the
+// function that lets it go on.
+func (g *Google) HoldEvents() (arrived <-chan struct{}, release func()) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.eventHold = newHold()
+	return g.eventHold.arrived, g.eventHold.releaseFunc()
+}
+
+// TokenCalls is how many requests, exchanges and refreshes, reached the
+// token endpoint.
+func (g *Google) TokenCalls() int {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	return g.tokenCalls
+}
+
+// Revoked lists the tokens the revoke endpoint received, in order.
+func (g *Google) Revoked() []string {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	return append([]string(nil), g.revoked...)
+}
+
+// Live reports whether token was issued by the fake and no revoke has
+// invalidated it since.
+func (g *Google) Live(token string) bool {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	return slices.Contains(g.issued, token) && !g.dead[token]
+}
+
+// HoldToken stops the next token request after its refresh token is issued
+// and before it is answered, so a revoke can land in between. It returns a
+// channel closed when the request arrives and the function that lets it go
+// on.
+func (g *Google) HoldToken() (arrived <-chan struct{}, release func()) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.tokenHold = newHold()
+	return g.tokenHold.arrived, g.tokenHold.releaseFunc()
+}
+
+// HoldRevoke stops the next revoke request before Google acts on it. It
+// returns a channel closed when the request arrives and the function that
+// lets it go on.
+func (g *Google) HoldRevoke() (arrived <-chan struct{}, release func()) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.revokeHold = newHold()
+	return g.revokeHold.arrived, g.revokeHold.releaseFunc()
+}
+
+func newHold() *hold {
+	return &hold{arrived: make(chan struct{}), release: make(chan struct{})}
+}
+
+func (h *hold) releaseFunc() func() {
+	var once sync.Once
+	return func() { once.Do(func() { close(h.release) }) }
+}
+
+// wait stops the request at h, if any, without holding g.mu.
+func (g *Google) wait(h *hold) {
+	if h == nil {
+		return
+	}
+	g.mu.Unlock()
+	close(h.arrived)
+	<-h.release
+	g.mu.Lock()
+}
+
+func (g *Google) token(w http.ResponseWriter, r *http.Request) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.tokenCalls++
+	if err := r.ParseForm(); err != nil {
+		http.Error(w, "bad form", http.StatusBadRequest)
+		return
+	}
+	f := r.PostForm
+	if f.Get("grant_type") == "refresh_token" {
+		g.refresh(w, f)
+		return
+	}
+	challenge, known := g.codes[f.Get("code")]
+	delete(g.codes, f.Get("code"))
+	switch {
+	case f.Get("grant_type") != "authorization_code":
+		oauthError(w, http.StatusBadRequest, "unsupported_grant_type")
+		return
+	case f.Get("client_id") != ClientID || f.Get("client_secret") != ClientSecret:
+		oauthError(w, http.StatusUnauthorized, "invalid_client")
+		return
+	case !known, f.Get("redirect_uri") != g.RedirectURL, s256(f.Get("code_verifier")) != challenge:
+		oauthError(w, http.StatusBadRequest, "invalid_grant")
+		return
+	}
+	if g.tokenStatus != http.StatusOK {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(g.tokenStatus)
+		fmt.Fprintf(w, `{"error":"invalid_grant","error_description":"echo %s %s"}`, RefreshToken, ClientSecret)
+		return
+	}
+	refresh := ""
+	if !g.omitRefresh {
+		issue := RefreshToken
+		if n := len(g.issued); n > 0 {
+			issue = fmt.Sprintf("%s-%d", RefreshToken, n+1)
+		}
+		g.issued = append(g.issued, issue)
+		refresh = fmt.Sprintf(`"refresh_token":%q,`, issue)
+	}
+	h := g.tokenHold
+	g.tokenHold = nil
+	g.wait(h)
+	w.Header().Set("Content-Type", "application/json")
+	fmt.Fprintf(w, `{"access_token":%q,%s"expires_in":3599,"scope":%q,"token_type":"Bearer"}`,
+		AccessToken, refresh, g.scope)
+}
+
+// refresh answers a refresh_token grant: an access token for a live refresh
+// token, invalid_grant quoting the token for any other.
+func (g *Google) refresh(w http.ResponseWriter, f url.Values) {
+	token := f.Get("refresh_token")
+	switch {
+	case f.Get("client_id") != ClientID || f.Get("client_secret") != ClientSecret:
+		oauthError(w, http.StatusUnauthorized, "invalid_client")
+		return
+	case !slices.Contains(g.issued, token) || g.dead[token]:
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusBadRequest)
+		fmt.Fprintf(w, `{"error":"invalid_grant","error_description":"Token has been expired or revoked: %s"}`, token)
+		return
+	case g.tokenStatus != http.StatusOK:
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(g.tokenStatus)
+		fmt.Fprintf(w, `{"error":"server_error","error_description":"echo %s %s"}`, token, ClientSecret)
+		return
+	}
+	w.Header().Set("Content-Type", "application/json")
+	fmt.Fprintf(w, `{"access_token":%q,"expires_in":3599,"scope":%q,"token_type":"Bearer"}`, AccessToken, g.scope)
+}
+
+// calendarList answers like Google's calendarList.list: the scripted
+// calendars, a page at a time, to a live grant's access token.
+func (g *Google) calendarList(w http.ResponseWriter, r *http.Request) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.calendarCalls++
+	h := g.calendarHold
+	g.calendarHold = nil
+	g.wait(h)
+	auth := r.Header.Get("Authorization")
+	if auth != "Bearer "+AccessToken || !g.grantLive() {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusUnauthorized)
+		fmt.Fprintf(w, `{"error":{"code":401,"message":"Invalid Credentials: %s"}}`, auth)
+		return
+	}
+	if g.calendarStatus != http.StatusOK {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(g.calendarStatus)
+		fmt.Fprintf(w, `{"error":{"code":%d,"message":"echo %s"}}`, g.calendarStatus, auth)
+		return
+	}
+	start := 0
+	if pt := r.URL.Query().Get("pageToken"); pt != "" {
+		n, err := strconv.Atoi(strings.TrimPrefix(pt, "page-"))
+		if err != nil || n <= 0 || n > len(g.calendars) {
+			http.Error(w, "bad pageToken", http.StatusBadRequest)
+			return
+		}
+		start = n
+	}
+	end := len(g.calendars)
+	if g.pageSize > 0 {
+		end = min(start+g.pageSize, end)
+	}
+	items := []map[string]any{}
+	for _, c := range g.calendars[start:end] {
+		item := map[string]any{
+			"kind":            "calendar#calendarListEntry",
+			"etag":            `"1700000000000000"`,
+			"id":              c.ID,
+			"summary":         c.Summary,
+			"description":     c.Description,
+			"timeZone":        "America/New_York",
+			"colorId":         "14",
+			"backgroundColor": "#9fe1e7",
+			"foregroundColor": "#000000",
+			"selected":        true,
+			"accessRole":      c.AccessRole,
+			"defaultReminders": []map[string]any{
+				{"method": "popup", "minutes": 30},
+			},
+			"conferenceProperties": map[string]any{"allowedConferenceSolutionTypes": []string{"hangoutsMeet"}},
+		}
+		if c.Primary {
+			item["primary"] = true
+		}
+		if c.SummaryOverride != "" {
+			item["summaryOverride"] = c.SummaryOverride
+		}
+		items = append(items, item)
+	}
+	page := map[string]any{"kind": "calendar#calendarList", "etag": `"p33k"`, "items": items}
+	if end < len(g.calendars) {
+		page["nextPageToken"] = fmt.Sprintf("page-%d", end)
+	} else {
+		page["nextSyncToken"] = "sync-token"
+	}
+	w.Header().Set("Content-Type", "application/json")
+	if err := json.NewEncoder(w).Encode(page); err != nil {
+		panic(err)
+	}
+}
+
+// insertEvent answers like Google's events.insert with a client-chosen id.
+func (g *Google) insertEvent(w http.ResponseWriter, r *http.Request) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	cal, ok := g.eventCalendar(w, r)
+	if !ok {
+		return
+	}
+	var e Event
+	if err := json.NewDecoder(r.Body).Decode(&e); err != nil || e.ID == "" {
+		http.Error(w, "bad event", http.StatusBadRequest)
+		return
+	}
+	if _, exists := g.events[cal][e.ID]; exists {
+		apiError(w, http.StatusConflict, "duplicate", "The requested identifier already exists.")
+		return
+	}
+	if g.events[cal] == nil {
+		g.events[cal] = map[string]Event{}
+	}
+	g.events[cal][e.ID] = e
+	g.inserts++
+	writeEvent(w, e)
+}
+
+// updateEvent answers like Google's events.update.
+func (g *Google) updateEvent(w http.ResponseWriter, r *http.Request) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	cal, ok := g.eventCalendar(w, r)
+	if !ok {
+		return
+	}
+	id := r.PathValue("event")
+	if _, exists := g.events[cal][id]; !exists {
+		apiError(w, http.StatusNotFound, "notFound", "Not Found")
+		return
+	}
+	var e Event
+	if err := json.NewDecoder(r.Body).Decode(&e); err != nil || e.ID != id {
+		http.Error(w, "bad event", http.StatusBadRequest)
+		return
+	}
+	g.events[cal][id] = e
+	g.updates++
+	writeEvent(w, e)
+}
+
+// eventCalendar runs the checks every events request shares: the hold, a
+// live grant's access token, a scripted failure, and a listed, writable
+// calendar, which it returns. When a check fails it answers and returns
+// false. The caller holds g.mu.
+func (g *Google) eventCalendar(w http.ResponseWriter, r *http.Request) (string, bool) {
+	g.eventWrites++
+	h := g.eventHold
+	g.eventHold = nil
+	g.wait(h)
+	auth := r.Header.Get("Authorization")
+	if auth != "Bearer "+AccessToken || !g.grantLive() {
+		apiError(w, http.StatusUnauthorized, "authError", "Invalid Credentials: "+auth)
+		return "", false
+	}
+	if g.failWrite != 0 && g.eventWrites == g.failWrite {
+		apiError(w, g.failStatus, "backendError", "echo "+auth)
+		return "", false
+	}
+	cal := r.PathValue("calendar")
+	i := slices.IndexFunc(g.calendars, func(c Calendar) bool { return c.ID == cal })
+	switch {
+	case i < 0:
+		apiError(w, http.StatusNotFound, "notFound", "Not Found")
+		return "", false
+	case g.calendars[i].AccessRole != "writer" && g.calendars[i].AccessRole != "owner":
+		apiError(w, http.StatusForbidden, "requiredAccessLevel", "You need to have writer access to this calendar.")
+		return "", false
+	}
+	return cal, true
+}
+
+// writeEvent answers with e as Google does, with fields of its own.
+func writeEvent(w http.ResponseWriter, e Event) {
+	w.Header().Set("Content-Type", "application/json")
+	if err := json.NewEncoder(w).Encode(map[string]any{
+		"kind": "calendar#event", "etag": `"3300000000000000"`, "id": e.ID, "status": e.Status,
+		"htmlLink": "https://www.google.com/calendar/event?eid=" + e.ID,
+		"summary":  e.Summary, "description": e.Description, "start": e.Start, "end": e.End,
+		"iCalUID": e.ID + "@google.com", "sequence": 0,
+	}); err != nil {
+		panic(err)
+	}
+}
+
+// apiError answers a Calendar API error with reason and message.
+func apiError(w http.ResponseWriter, status int, reason, message string) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	if err := json.NewEncoder(w).Encode(map[string]any{"error": map[string]any{
+		"code": status, "message": message,
+		"errors": []map[string]any{{"domain": "global", "reason": reason, "message": message}},
+	}}); err != nil {
+		panic(err)
+	}
+}
+
+// grantLive reports whether any refresh token issued is still live. The
+// caller holds g.mu.
+func (g *Google) grantLive() bool {
+	for _, t := range g.issued {
+		if !g.dead[t] {
+			return true
+		}
+	}
+	return false
+}
+
+func (g *Google) revoke(w http.ResponseWriter, r *http.Request) {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	if r.Header.Get("Content-Type") != "application/x-www-form-urlencoded" {
+		http.Error(w, "want a form", http.StatusUnsupportedMediaType)
+		return
+	}
+	if err := r.ParseForm(); err != nil {
+		http.Error(w, "bad form", http.StatusBadRequest)
+		return
+	}
+	h := g.revokeHold
+	g.revokeHold = nil
+	g.wait(h)
+	token := r.PostForm.Get("token")
+	g.revoked = append(g.revoked, token)
+	if g.revokeStatus == http.StatusOK && slices.Contains(g.issued, token) {
+		// Google revokes the grant, not just the token: every token issued
+		// to it so far stops working.
+		for _, t := range g.issued {
+			g.dead[t] = true
+		}
+	}
+	body := g.revokeBody
+	if body == "" && g.revokeStatus != http.StatusOK {
+		body = "cannot revoke " + token
+	}
+	w.WriteHeader(g.revokeStatus)
+	fmt.Fprint(w, body)
+}
+
+func oauthError(w http.ResponseWriter, status int, code string) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	fmt.Fprintf(w, `{"error":%q}`, code)
+}
+
+// s256 is the PKCE S256 challenge for verifier.
+func s256(verifier string) string {
+	sum := sha256.Sum256([]byte(verifier))
+	return base64.RawURLEncoding.EncodeToString(sum[:])
+}

internal/plan/draft.go

@@ -136,9 +136,10 @@ func (s *Service) request(ctx context.Context, weekStart store.LocalDate) (skill
 
 // storeDraft stores week as the plan of the week starting weekStart in one
 // transaction and returns the plan's id. A new plan is draft. A draft
-// replaces the days of an existing plan, keeping each day's calendar
-// event id; a draft plan stays draft and a synced or changed one becomes
-// changed, since Calendar no longer shows it. A plan synced since the
+// replaces the days of an existing plan, keeping the calendar event id of
+// each day whose dinner stays the same and clearing the others'; a draft
+// plan stays draft and a synced or changed one becomes changed, since
+// Calendar no longer shows it. A plan synced since the
 // draft was asked for without confirm is left as it is, failing with
 // ReasonConfirmRequired, and so is a plan no longer at revision base (the
 // revision before draft_week ran, or noPlan), failing with

internal/plan/plan.go

@@ -4,7 +4,7 @@
 // a day from Monday to Sunday, and the job stores them as the week's plan,
 // replacing any draft before it unless the household edited the plan
 // while draft_week ran. A plan is draft until Push to Calendar
-// syncs it (Feature 16); an edit of a synced plan makes it changed.
+// syncs it (Push); an edit of a synced plan makes it changed.
 //
 // The Rotation check follows a plan day: MarkTried moves the Quest log
 // dinners planned on it to tried, and the household answers "Keep it in
@@ -17,6 +17,7 @@ import (
 	"errors"
 	"fmt"
 	"log/slog"
+	"net/url"
 	"slices"
 	"time"
 
@@ -132,19 +133,24 @@ func ParseWeekStart(s string) (store.LocalDate, error) {
 // skills.DraftWeek with the household's harness.Config.
 type Drafter func(ctx context.Context, scope string, in skills.WeekRequest) (skills.Week, error)
 
-// Service drafts, reads and edits weekly plans.
+// Service drafts, reads, edits and pushes weekly plans.
 type Service struct {
 	st       *store.Store
 	draft    Drafter
+	cal      Calendar
 	logger   *slog.Logger
 	draftJob *jobs.Kind[DraftJob]
+	// publicURL is MEALQUEST_PUBLIC_URL, under which a pushed event links
+	// to its dinner.
+	publicURL *url.URL
 }
 
-// NewService returns a service over st that drafts with draft and
-// registers the KindDraftWeek job on runner, which must not have started
-// yet. The kind is service-only: StartDraft, which keeps one draft in
-// flight per week, is the only way to enqueue it.
-func NewService(st *store.Store, draft Drafter, runner *jobs.Runner, logger *slog.Logger) (*Service, error) {
+// NewService returns a service over st that drafts with draft, pushes to
+// cal with links under publicURL, and registers the KindDraftWeek job on
+// runner, which must not have started yet. The kind is service-only:
+// StartDraft, which keeps one draft in flight per week, is the only way to
+// enqueue it.
+func NewService(st *store.Store, draft Drafter, runner *jobs.Runner, cal Calendar, publicURL *url.URL, logger *slog.Logger) (*Service, error) {
 	switch {
 	case st == nil:
 		return nil, errors.New("plan: nil store")
@@ -152,10 +158,14 @@ func NewService(st *store.Store, draft Drafter, runner *jobs.Runner, logger *slo
 		return nil, errors.New("plan: nil drafter")
 	case runner == nil:
 		return nil, errors.New("plan: nil job runner")
+	case cal == nil:
+		return nil, errors.New("plan: nil calendar")
+	case publicURL == nil:
+		return nil, errors.New("plan: nil public URL")
 	case logger == nil:
 		return nil, errors.New("plan: nil logger")
 	}
-	s := &Service{st: st, draft: draft, logger: logger}
+	s := &Service{st: st, draft: draft, cal: cal, logger: logger, publicURL: publicURL}
 	kind, err := jobs.Register(runner, KindDraftWeek, s.runDraft, Reasons...)
 	if err != nil {
 		return nil, err
@@ -344,8 +354,9 @@ func (s *Service) StartDraft(ctx context.Context, weekStart store.LocalDate, con
 }
 
 // Swap plans dinnerID on date of the week starting weekStart, marking the
-// day new when the dinner is in the Quest log. Swapping a synced plan
-// makes it changed. The week must have a plan (else ErrNotFound), date
+// day new when the dinner is in the Quest log and clearing its calendar
+// event id, so the next Push writes it. Swapping a synced plan makes it
+// changed. The week must have a plan (else ErrNotFound), date
 // must be one of its days (else *InvalidDayError), the dinner must be a
 // Regular or in the Quest log (else ErrDinnerNotFound or
 // *DinnerNotPlannableError), and it must not be on another day of the

internal/plan/plan_test.go

@@ -2,12 +2,15 @@ package plan_test
 
 import (
 	"context"
+	"crypto/rand"
 	"database/sql"
+	"encoding/base64"
 	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
 	"log/slog"
+	"net/url"
 	"slices"
 	"strings"
 	"sync"
@@ -18,9 +21,12 @@ import (
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/ai/llm"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/ai/skills"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/db"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal/gcaltest"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/household"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/jobs"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/plan"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/secretbox"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/store"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/migrations"
 )
@@ -31,6 +37,9 @@ var (
 	weekDates = []string{"2026-10-12", "2026-10-13", "2026-10-14", "2026-10-15", "2026-10-16", "2026-10-17", "2026-10-18"}
 )
 
+// publicURL is MEALQUEST_PUBLIC_URL in these tests.
+var publicURL = &url.URL{Scheme: "https", Host: "meals.example.com"}
+
 func mustDate(s string) store.LocalDate {
 	d, err := store.ParseLocalDate(s)
 	if err != nil {
@@ -44,6 +53,9 @@ type env struct {
 	st     *store.Store
 	runner *jobs.Runner
 	model  *llm.Fake
+	// google is the fake Google the service pushes to through gcal.
+	google *gcaltest.Google
+	gcal   *gcal.Service
 	// ids are the seeded dinners' ids by name.
 	ids map[string]string
 
@@ -55,7 +67,8 @@ type env struct {
 // America/New_York with dinner time 17:30, the Regulars below and Quest
 // log dinners Pad Thai and Shawarma Bowls, and an unstarted job runner
 // with two workers. It drafts through the real harness and draft_week with
-// the scripted e.model.
+// the scripted e.model, and pushes through gcal to e.google, which starts
+// unconnected.
 func newEnv(t *testing.T) *env {
 	t.Helper()
 	ctx := t.Context()
@@ -111,7 +124,26 @@ func newEnv(t *testing.T) *env {
 	if err != nil {
 		t.Fatal(err)
 	}
-	e.svc, err = plan.NewService(st, drafter, e.runner, logger)
+	e.google = gcaltest.New(t, "https://meals.example.com"+gcal.CallbackPath)
+	key := make([]byte, secretbox.KeySize)
+	rand.Read(key)
+	box, err := secretbox.New(base64.StdEncoding.EncodeToString(key))
+	if err != nil {
+		t.Fatal(err)
+	}
+	e.gcal, err = gcal.NewService(st, box, gcal.Config{
+		ClientID:     gcaltest.ClientID,
+		ClientSecret: gcaltest.ClientSecret,
+		PublicURL:    publicURL,
+		SecretKey:    []byte("server-secret-key"),
+		Endpoint:     e.google.Endpoint(),
+		RevokeURL:    e.google.RevokeURL(),
+		CalendarAPI:  e.google.CalendarAPI(),
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	e.svc, err = plan.NewService(st, drafter, e.runner, e.gcal, publicURL, logger)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -781,12 +813,26 @@ func TestDraftOverSyncedOrChangedPlanNeedsConfirm(t *testing.T) {
 			if got := dayNames(p); !slices.Equal(got, reversed) {
 				t.Errorf("days = %v, want %v", got, reversed)
 			}
-			var events int
-			if err := e.st.Reader.QueryRowContext(t.Context(), `SELECT COUNT(*) FROM plan_days WHERE calendar_event_id = 'ev-' || date`).Scan(&events); err != nil {
+			// Reversed, only Thursday keeps its dinner, so only Thursday
+			// keeps its event id: Calendar no longer shows the others as
+			// planned.
+			rows, err := e.st.Reader.QueryContext(t.Context(), `SELECT date FROM plan_days WHERE calendar_event_id = 'ev-' || date ORDER BY date`)
+			if err != nil {
 				t.Fatal(err)
 			}
-			if events != 7 {
-				t.Errorf("%d days kept their calendar event id, want 7", events)
+			var kept []string
+			for rows.Next() {
+				var date string
+				if err := rows.Scan(&date); err != nil {
+					t.Fatal(err)
+				}
+				kept = append(kept, date)
+			}
+			if err := errors.Join(rows.Err(), rows.Close()); err != nil {
+				t.Fatal(err)
+			}
+			if !slices.Equal(kept, []string{"2026-10-15"}) {
+				t.Errorf("days that kept their calendar event id = %v, want only the unchanged 2026-10-15", kept)
 			}
 		})
 	}

internal/plan/push.go

@@ -0,0 +1,223 @@
+package plan
+
+import (
+	"context"
+	"crypto/sha256"
+	"database/sql"
+	"encoding/base32"
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/db"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/household"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/store"
+)
+
+// eventLength is how long a dinner's Calendar event lasts.
+const eventLength = 60 * time.Minute
+
+// ErrPlanChanged is a Push to Calendar of a plan edited (swapped or
+// redrafted) while it was being pushed: Calendar may show the plan as it
+// was, so the push is not recorded and pushing again brings Calendar up to
+// date.
+var ErrPlanChanged = errors.New("the plan changed while it was being pushed to Calendar; push again")
+
+// Calendar writes events to the household's chosen calendar, then runs
+// record while that calendar stays chosen. In production it is
+// *gcal.Service.
+type Calendar interface {
+	PushEvents(ctx context.Context, events []gcal.Event, record func() error) error
+}
+
+// eventIDEncoding is base32hex, lowercase and unpadded: Google's alphabet
+// for event ids.
+var eventIDEncoding = base32.NewEncoding("0123456789abcdefghijklmnopqrstuv").WithPadding(base32.NoPadding)
+
+// EventID is the Calendar event id of date of the week starting weekStart:
+// the lowercase base32hex SHA-256 of "mealquest|{weekStart}|{date}", 52
+// characters of a-v and 0-9, within Google's rule for event ids (that
+// alphabet, 5 to 1024 characters). A day always has the same id, so
+// pushing it again updates its event rather than adding another.
+func EventID(weekStart, date store.LocalDate) string {
+	sum := sha256.Sum256([]byte("mealquest|" + weekStart.String() + "|" + date.String()))
+	return eventIDEncoding.EncodeToString(sum[:])
+}
+
+// pushDay is a day of a plan being pushed: its date and its event.
+type pushDay struct {
+	date  string
+	event gcal.Event
+}
+
+// Push pushes the plan of the week starting weekStart to the household's
+// chosen calendar and returns the plan as synced. Each day is an event
+// "Dinner: {name}" from the household's dinner time on that date, in the
+// household's zone, for an hour; its description is the dinner's name,
+// "Start by {time}" for a crock-pot dinner whose minutes are known, and
+// the dinner's link under the public URL. Its id is EventID.
+//
+// A push writes the days Calendar does not show as planned: those never
+// pushed, swapped, or redrafted to another dinner since, whose
+// calendar_event_id is empty. When every day has one, Calendar shows the
+// whole plan and every day is written again, which puts back anything
+// changed in Calendar since: the app is the source of truth. A stored event
+// id is always on the chosen calendar: choosing another
+// (gcal.Service.SelectCalendar) or disconnecting (gcal.Service.Disconnect)
+// clears them all, so the next push writes the whole week.
+//
+// Only a push that wrote every one of those events is recorded: the plan
+// becomes synced with calendar_synced_at now, and each day written stores
+// its event id. A push that failed part way records nothing and leaves the
+// plan's status as it was; since event ids are fixed, pushing again
+// updates the events already written rather than adding them twice. The
+// push is recorded while the calendar written to is still the chosen one.
+// A plan edited while it was pushed, or whose events were forgotten by
+// choosing another calendar or disconnecting, fails with ErrPlanChanged,
+// unrecorded.
+//
+// The week must have a plan (else ErrNotFound). The calendar's errors are
+// returned as they are: gcal.ErrNotConnected, gcal.ErrNoCalendar,
+// gcal.ErrCalendarUnavailable, gcal.ErrReconnect or *gcal.CalendarError.
+//
+// A successful Push is the household confirming the week's plan, which is
+// what the week's Supply run (Feature 17) is made from; the returned plan
+// is the one pushed.
+func (s *Service) Push(ctx context.Context, weekStart store.LocalDate) (Plan, error) {
+	if _, err := household.WeekDays(weekStart); err != nil {
+		return Plan{}, &InvalidWeekError{Value: weekStart.String()}
+	}
+	planID, revision, days, err := s.pushDays(ctx, weekStart)
+	if err != nil {
+		return Plan{}, err
+	}
+	events := make([]gcal.Event, len(days))
+	for i, d := range days {
+		events[i] = d.event
+	}
+	var p Plan
+	record := func() error {
+		return s.st.WithTx(ctx, func(tx *sql.Tx) error {
+			q := db.New(tx)
+			now := store.Now().String()
+			n, err := q.MarkWeekPlanSynced(ctx, db.MarkWeekPlanSyncedParams{
+				CalendarSyncedAt: sql.NullString{String: now, Valid: true},
+				UpdatedAt:        now,
+				ID:               planID,
+				Revision:         revision,
+			})
+			if err != nil {
+				return fmt.Errorf("plan: mark %s synced: %w", planID, err)
+			}
+			if n != 1 {
+				return ErrPlanChanged
+			}
+			for _, d := range days {
+				n, err := q.SetPlanDayCalendarEvent(ctx, db.SetPlanDayCalendarEventParams{
+					CalendarEventID: sql.NullString{String: d.event.ID, Valid: true},
+					UpdatedAt:       now,
+					PlanID:          planID,
+					Date:            d.date,
+				})
+				if err != nil {
+					return fmt.Errorf("plan: record event of %s of %s: %w", d.date, planID, err)
+				}
+				if n != 1 {
+					return fmt.Errorf("plan: %s has no day %s", planID, d.date)
+				}
+			}
+			p, err = readPlan(ctx, q, weekStart)
+			return err
+		})
+	}
+	if err := s.cal.PushEvents(ctx, events, record); err != nil {
+		return Plan{}, fmt.Errorf("plan: push %s to Calendar: %w", weekStart, err)
+	}
+	return p, nil
+}
+
+// pushDays reads, in one read transaction, the plan of the week starting
+// weekStart, its revision, and the days a push writes with their events.
+func (s *Service) pushDays(ctx context.Context, weekStart store.LocalDate) (planID string, revision int64, days []pushDay, err error) {
+	tx, err := s.st.Reader.BeginTx(ctx, nil)
+	if err != nil {
+		return "", 0, nil, fmt.Errorf("plan: begin read: %w", err)
+	}
+	defer func() {
+		err = errors.Join(err, tx.Rollback())
+	}()
+	q := db.New(tx)
+	row, err := q.GetWeekPlan(ctx, weekStart.String())
+	if errors.Is(err, sql.ErrNoRows) {
+		return "", 0, nil, ErrNotFound
+	}
+	if err != nil {
+		return "", 0, nil, fmt.Errorf("plan: read week %s: %w", weekStart, err)
+	}
+	settings, err := q.GetHouseholdSettings(ctx)
+	if err != nil {
+		return "", 0, nil, fmt.Errorf("plan: read household settings: %w", err)
+	}
+	zone, err := household.LoadZone(settings.Timezone)
+	if err != nil {
+		return "", 0, nil, fmt.Errorf("plan: household settings: %w", err)
+	}
+	rows, err := q.ListPlanDays(ctx, row.ID)
+	if err != nil {
+		return "", 0, nil, fmt.Errorf("plan: read days of %s: %w", row.ID, err)
+	}
+	dates, err := household.WeekDays(weekStart)
+	if err != nil {
+		return "", 0, nil, fmt.Errorf("plan: %w", err)
+	}
+	if len(rows) != len(dates) {
+		return "", 0, nil, fmt.Errorf("plan: week %s has %d planned days, want %d", weekStart, len(rows), len(dates))
+	}
+	all := make([]pushDay, len(rows))
+	for i, r := range rows {
+		if r.Date != dates[i].String() {
+			return "", 0, nil, fmt.Errorf("plan: week %s day %d is %s, want %s", weekStart, i+1, r.Date, dates[i])
+		}
+		event, err := s.event(zone, settings.Timezone, settings.DinnerTime, weekStart, dates[i], r.Dinner)
+		if err != nil {
+			return "", 0, nil, fmt.Errorf("plan: event of %s: %w", r.Date, err)
+		}
+		d := pushDay{date: r.Date, event: event}
+		all[i] = d
+		if !r.CalendarEventID.Valid {
+			days = append(days, d)
+		}
+	}
+	if len(days) == 0 {
+		days = all
+	}
+	return row.ID, row.Revision, days, nil
+}
+
+// event is the Calendar event of dinner d on date of the week starting
+// weekStart, at dinnerTime in zone, named zoneName.
+func (s *Service) event(zone *time.Location, zoneName, dinnerTime string, weekStart, date store.LocalDate, d db.Dinner) (gcal.Event, error) {
+	start, err := household.LocalTime(zone, date, dinnerTime)
+	if err != nil {
+		return gcal.Event{}, err
+	}
+	lines := []string{d.Name}
+	startBy, err := startBy(zone, date, dinnerTime, d)
+	if err != nil {
+		return gcal.Event{}, err
+	}
+	if startBy != nil {
+		lines = append(lines, "Start by "+startBy.In(zone).Format("3:04 pm"))
+	}
+	lines = append(lines, s.publicURL.JoinPath("dinner", d.ID).String())
+	return gcal.Event{
+		ID:          EventID(weekStart, date),
+		Summary:     "Dinner: " + d.Name,
+		Description: strings.Join(lines, "\n"),
+		Start:       start,
+		End:         start.Add(eventLength),
+		TimeZone:    zoneName,
+	}, nil
+}

internal/plan/push_test.go

@@ -0,0 +1,754 @@
+package plan_test
+
+import (
+	"crypto/sha256"
+	"database/sql"
+	"encoding/base32"
+	"errors"
+	"maps"
+	"net/http"
+	"regexp"
+	"slices"
+	"strings"
+	"testing"
+	"time"
+
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/db"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal/gcaltest"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/plan"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/store"
+)
+
+// dinnersCal is the calendar the tests push to.
+var dinnersCal = gcaltest.Calendar{ID: "dinners@group.calendar.google.com", Summary: "Dinners", AccessRole: "owner"}
+
+// connectCalendar connects the household's Google account and chooses
+// dinnersCal.
+func (e *env) connectCalendar(t *testing.T) {
+	t.Helper()
+	e.google.SetCalendars(0, dinnersCal)
+	e.google.Connect(t, e.gcal)
+	if _, err := e.gcal.SelectCalendar(t.Context(), dinnersCal.ID); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// storePlan stores a draft plan of the week starting weekStart with the
+// dinners named names, Monday first, and returns its days' dates.
+func (e *env) storePlan(t *testing.T, weekStart store.LocalDate, names ...string) []string {
+	t.Helper()
+	q := db.New(e.st.Writer)
+	now := store.Now().String()
+	id := store.NewID()
+	if err := q.CreateWeekPlan(t.Context(), db.CreateWeekPlanParams{ID: id, WeekStart: weekStart.String(), CreatedAt: now, UpdatedAt: now}); err != nil {
+		t.Fatal(err)
+	}
+	y, m, d := weekStart.Date()
+	var dates []string
+	for i, name := range names {
+		date := store.LocalDateOf(time.Date(y, m, d+i, 0, 0, 0, 0, time.UTC)).String()
+		if err := q.PutPlanDay(t.Context(), db.PutPlanDayParams{ID: store.NewID(), PlanID: id, Date: date,
+			DinnerID: sql.NullString{String: e.ids[name], Valid: true}, CreatedAt: now, UpdatedAt: now}); err != nil {
+			t.Fatal(err)
+		}
+		dates = append(dates, date)
+	}
+	return dates
+}
+
+// eventIDs returns each day's stored calendar_event_id of the week
+// starting weekStart, "" for none, by date.
+func (e *env) eventIDs(t *testing.T, weekStart store.LocalDate) map[string]string {
+	t.Helper()
+	rows, err := e.st.Reader.QueryContext(t.Context(), `SELECT plan_days.date, plan_days.calendar_event_id FROM plan_days
+		JOIN week_plans ON week_plans.id = plan_days.plan_id WHERE week_plans.week_start = ?`, weekStart.String())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer rows.Close()
+	out := map[string]string{}
+	for rows.Next() {
+		var date string
+		var id sql.NullString
+		if err := rows.Scan(&date, &id); err != nil {
+			t.Fatal(err)
+		}
+		out[date] = id.String
+	}
+	if err := rows.Err(); err != nil {
+		t.Fatal(err)
+	}
+	return out
+}
+
+// assertUnsynced fails unless the plan of weekStart has status, no
+// calendar_synced_at and no stored event ids.
+func (e *env) assertUnsynced(t *testing.T, weekStart store.LocalDate, status string) {
+	t.Helper()
+	p, err := e.svc.Get(t.Context(), weekStart)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if p.Status != status || p.CalendarSyncedAt != nil {
+		t.Errorf("plan = %s synced at %v, want %s and never synced", p.Status, p.CalendarSyncedAt, status)
+	}
+	for date, id := range e.eventIDs(t, weekStart) {
+		if id != "" {
+			t.Errorf("%s stored event id %q after a failed push", date, id)
+		}
+	}
+}
+
+// assertNoSecret fails when text holds the refresh token, the access token
+// or the client secret.
+func assertNoSecret(t *testing.T, what, text string) {
+	t.Helper()
+	for _, secret := range []string{gcaltest.RefreshToken, gcaltest.AccessToken, gcaltest.ClientSecret} {
+		if strings.Contains(text, secret) {
+			t.Errorf("%s contains a secret: %s", what, text)
+		}
+	}
+}
+
+func TestEventIDIsDeterministicAndWithinGoogleRules(t *testing.T) {
+	monday, tuesday := mustDate("2026-10-12"), mustDate("2026-10-13")
+	id := plan.EventID(monday, tuesday)
+	sum := sha256.Sum256([]byte("mealquest|2026-10-12|2026-10-13"))
+	if want := strings.ToLower(base32.HexEncoding.WithPadding(base32.NoPadding).EncodeToString(sum[:])); id != want {
+		t.Errorf("EventID = %s, want %s", id, want)
+	}
+	// Google: base32hex characters (a-v, 0-9), 5 to 1024 of them.
+	if !regexp.MustCompile(`^[a-v0-9]{5,1000}$`).MatchString(id) || len(id) != 52 {
+		t.Errorf("EventID = %q (%d characters), want 52 of a-v and 0-9", id, len(id))
+	}
+	if again := plan.EventID(monday, tuesday); again != id {
+		t.Errorf("EventID changed between calls: %s, %s", id, again)
+	}
+	if plan.EventID(monday, monday) == id || plan.EventID(mustDate("2026-10-19"), tuesday) == id {
+		t.Error("EventID is the same for another date or week")
+	}
+}
+
+func TestPushCreatesOneEventPerDay(t *testing.T) {
+	e := newEnv(t)
+	e.connectCalendar(t)
+	dates := e.storePlan(t, week, fullWeek...)
+
+	p, err := e.svc.Push(t.Context(), week)
+	if err != nil {
+		t.Fatalf("Push: %v", err)
+	}
+	if p.Status != plan.StatusSynced || p.CalendarSyncedAt == nil {
+		t.Errorf("pushed plan = %s synced at %v, want synced with a time", p.Status, p.CalendarSyncedAt)
+	}
+	if inserts, updates := e.google.EventWrites(); inserts != 7 || updates != 0 {
+		t.Errorf("Google saw %d inserts and %d updates, want 7 and 0", inserts, updates)
+	}
+	events := e.google.Events(dinnersCal.ID)
+	if len(events) != 7 {
+		t.Fatalf("calendar has %d events, want 7", len(events))
+	}
+	stored := e.eventIDs(t, week)
+	for i, date := range dates {
+		id := plan.EventID(week, mustDate(date))
+		ev, ok := events[id]
+		if !ok {
+			t.Errorf("%s: no event %s", date, id)
+			continue
+		}
+		if stored[date] != id {
+			t.Errorf("%s stored event id %q, want %s", date, stored[date], id)
+		}
+		name := fullWeek[i]
+		if ev.Summary != "Dinner: "+name || ev.Status != "confirmed" {
+			t.Errorf("%s event = %q %s, want \"Dinner: %s\" confirmed", date, ev.Summary, ev.Status, name)
+		}
+		// Dinner time 17:30 in New York, EDT all week, for an hour.
+		if want := (gcaltest.EventTime{DateTime: date + "T17:30:00-04:00", TimeZone: "America/New_York"}); ev.Start != want {
+			t.Errorf("%s start = %+v, want %+v", date, ev.Start, want)
+		}
+		if want := (gcaltest.EventTime{DateTime: date + "T18:30:00-04:00", TimeZone: "America/New_York"}); ev.End != want {
+			t.Errorf("%s end = %+v, want %+v", date, ev.End, want)
+		}
+	}
+	// Beef Chili cooks 240 minutes in the crock pot; Pot Roast's minutes
+	// are unknown, so it has no start time, and Pad Thai is not a crock-pot
+	// dinner.
+	for _, tc := range []struct{ date, want string }{
+		{"2026-10-12", "Beef Chili\nStart by 1:30 pm\nhttps://meals.example.com/dinner/" + e.ids["Beef Chili"]},
+		{"2026-10-13", "Pot Roast\nhttps://meals.example.com/dinner/" + e.ids["Pot Roast"]},
+		{"2026-10-14", "Pad Thai\nhttps://meals.example.com/dinner/" + e.ids["Pad Thai"]},
+	} {
+		if got := events[plan.EventID(week, mustDate(tc.date))].Description; got != tc.want {
+			t.Errorf("%s description = %q, want %q", tc.date, got, tc.want)
+		}
+	}
+	got, err := e.svc.Get(t.Context(), week)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.Status != plan.StatusSynced || got.CalendarSyncedAt == nil || *got.CalendarSyncedAt != *p.CalendarSyncedAt {
+		t.Errorf("stored plan = %s synced at %v, want as pushed", got.Status, got.CalendarSyncedAt)
+	}
+}
+
+func TestPushAgainUpdatesOnly(t *testing.T) {
+	e := newEnv(t)
+	e.connectCalendar(t)
+	e.storePlan(t, week, fullWeek...)
+	if _, err := e.svc.Push(t.Context(), week); err != nil {
+		t.Fatal(err)
+	}
+	// The household deletes Monday's event in Google Calendar; Google keeps
+	// its id.
+	monday := plan.EventID(week, week)
+	e.google.CancelEvent(dinnersCal.ID, monday)
+	e.google.ResetEventWrites()
+
+	p, err := e.svc.Push(t.Context(), week)
+	if err != nil {
+		t.Fatalf("second Push: %v", err)
+	}
+	if inserts, updates := e.google.EventWrites(); inserts != 0 || updates != 7 {
+		t.Errorf("second push: %d inserts and %d updates, want 0 and 7", inserts, updates)
+	}
+	events := e.google.Events(dinnersCal.ID)
+	if len(events) != 7 {
+		t.Errorf("calendar has %d events, want 7", len(events))
+	}
+	if events[monday].Status != "confirmed" {
+		t.Errorf("Monday's event is %s, want it put back", events[monday].Status)
+	}
+	if p.Status != plan.StatusSynced {
+		t.Errorf("status = %s, want synced", p.Status)
+	}
+}
+
+func TestSwapThenPushUpdatesThatDay(t *testing.T) {
+	e := newEnv(t)
+	e.connectCalendar(t)
+	e.storePlan(t, week, fullWeek...)
+	if _, err := e.svc.Push(t.Context(), week); err != nil {
+		t.Fatal(err)
+	}
+	before := e.google.Events(dinnersCal.ID)
+	e.google.ResetEventWrites()
+
+	fishTacos := e.dinner(t, "Fish Tacos", "regular", "stovetop", 25)
+	swapped, err := e.svc.Swap(t.Context(), week, "2026-10-14", fishTacos)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if swapped.Status != plan.StatusChanged {
+		t.Fatalf("status after swap = %s, want changed", swapped.Status)
+	}
+	if id := e.eventIDs(t, week)["2026-10-14"]; id != "" {
+		t.Errorf("swapped day kept event id %q", id)
+	}
+
+	p, err := e.svc.Push(t.Context(), week)
+	if err != nil {
+		t.Fatalf("Push: %v", err)
+	}
+	if inserts, updates := e.google.EventWrites(); inserts != 0 || updates != 1 {
+		t.Errorf("push after swap: %d inserts and %d updates, want 0 and 1", inserts, updates)
+	}
+	wednesday := plan.EventID(week, mustDate("2026-10-14"))
+	after := e.google.Events(dinnersCal.ID)
+	if got := after[wednesday]; got.Summary != "Dinner: Fish Tacos" ||
+		got.Description != "Fish Tacos\nhttps://meals.example.com/dinner/"+fishTacos {
+		t.Errorf("Wednesday's event = %+v, want Fish Tacos", got)
+	}
+	delete(before, wednesday)
+	delete(after, wednesday)
+	if !maps.Equal(before, after) {
+		t.Errorf("events of other days changed:\nbefore %+v\nafter  %+v", before, after)
+	}
+	if p.Status != plan.StatusSynced {
+		t.Errorf("status = %s, want synced", p.Status)
+	}
+	if id := e.eventIDs(t, week)["2026-10-14"]; id != wednesday {
+		t.Errorf("Wednesday stored event id %q, want %s", id, wednesday)
+	}
+}
+
+func TestPushAcrossDaylightSavingTime(t *testing.T) {
+	for _, tc := range []struct {
+		name string
+		week store.LocalDate
+		// utc is each day's 17:30 New York dinner as a UTC instant.
+		utc []string
+	}{
+		// New York leaves daylight saving time at 02:00 on Sunday
+		// 2026-11-01.
+		{"fall back", mustDate("2026-10-26"), []string{
+			"2026-10-26T21:30:00Z", "2026-10-27T21:30:00Z", "2026-10-28T21:30:00Z", "2026-10-29T21:30:00Z",
+			"2026-10-30T21:30:00Z", "2026-10-31T21:30:00Z", "2026-11-01T22:30:00Z",
+		}},
+		// It enters it at 02:00 on Sunday 2027-03-14.
+		{"spring forward", mustDate("2027-03-08"), []string{
+			"2027-03-08T22:30:00Z", "2027-03-09T22:30:00Z", "2027-03-10T22:30:00Z", "2027-03-11T22:30:00Z",
+			"2027-03-12T22:30:00Z", "2027-03-13T22:30:00Z", "2027-03-14T21:30:00Z",
+		}},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			e := newEnv(t)
+			e.connectCalendar(t)
+			dates := e.storePlan(t, tc.week, fullWeek...)
+			if _, err := e.svc.Push(t.Context(), tc.week); err != nil {
+				t.Fatalf("Push: %v", err)
+			}
+			events := e.google.Events(dinnersCal.ID)
+			for i, date := range dates {
+				ev := events[plan.EventID(tc.week, mustDate(date))]
+				start, err := time.Parse(time.RFC3339, ev.Start.DateTime)
+				if err != nil {
+					t.Fatalf("%s start %q: %v", date, ev.Start.DateTime, err)
+				}
+				end, err := time.Parse(time.RFC3339, ev.End.DateTime)
+				if err != nil {
+					t.Fatalf("%s end %q: %v", date, ev.End.DateTime, err)
+				}
+				if got := start.UTC().Format(time.RFC3339); got != tc.utc[i] {
+					t.Errorf("%s starts %s (%s), want %s", date, got, ev.Start.DateTime, tc.utc[i])
+				}
+				if !strings.HasPrefix(ev.Start.DateTime, date+"T17:30:00") {
+					t.Errorf("%s starts %s, want 17:30 local", date, ev.Start.DateTime)
+				}
+				if end.Sub(start) != time.Hour {
+					t.Errorf("%s lasts %v, want 1h", date, end.Sub(start))
+				}
+				if ev.Start.TimeZone != "America/New_York" || ev.End.TimeZone != "America/New_York" {
+					t.Errorf("%s zones = %s, %s", date, ev.Start.TimeZone, ev.End.TimeZone)
+				}
+			}
+		})
+	}
+}
+
+func TestPushNeedsAChosenCalendar(t *testing.T) {
+	e := newEnv(t)
+	e.storePlan(t, week, fullWeek...)
+	if _, err := e.svc.Push(t.Context(), week); !errors.Is(err, gcal.ErrNotConnected) {
+		t.Errorf("Push with nothing connected = %v, want ErrNotConnected", err)
+	}
+	e.google.SetCalendars(0, dinnersCal)
+	e.google.Connect(t, e.gcal)
+	if _, err := e.svc.Push(t.Context(), week); !errors.Is(err, gcal.ErrNoCalendar) {
+		t.Errorf("Push with no calendar chosen = %v, want ErrNoCalendar", err)
+	}
+	if inserts, updates := e.google.EventWrites(); inserts+updates != 0 {
+		t.Errorf("Google saw %d event writes", inserts+updates)
+	}
+	e.assertUnsynced(t, week, plan.StatusDraft)
+}
+
+func TestPushWithoutAPlan(t *testing.T) {
+	e := newEnv(t)
+	e.connectCalendar(t)
+	before := e.google.TokenCalls()
+	if _, err := e.svc.Push(t.Context(), week); !errors.Is(err, plan.ErrNotFound) {
+		t.Errorf("Push = %v, want ErrNotFound", err)
+	}
+	if n := e.google.TokenCalls() - before; n != 0 {
+		t.Errorf("token endpoint called %d times for a week with no plan", n)
+	}
+}
+
+func TestPushPartialFailureLeavesPlanUnsynced(t *testing.T) {
+	e := newEnv(t)
+	e.connectCalendar(t)
+	e.storePlan(t, week, fullWeek...)
+	// Google fails the fourth event.
+	e.google.FailEventWrite(4, http.StatusServiceUnavailable)
+
+	_, err := e.svc.Push(t.Context(), week)
+	var calendar *gcal.CalendarError
+	if !errors.As(err, &calendar) {
+		t.Fatalf("Push = %v, want *gcal.CalendarError", err)
+	}
+	assertNoSecret(t, "error", err.Error())
+	if n := len(e.google.Events(dinnersCal.ID)); n != 3 {
+		t.Fatalf("calendar has %d events, want the 3 before the failure", n)
+	}
+	e.assertUnsynced(t, week, plan.StatusDraft)
+
+	// Pushing again writes every day: the three already there are updated,
+	// not added twice.
+	e.google.ResetEventWrites()
+	p, err := e.svc.Push(t.Context(), week)
+	if err != nil {
+		t.Fatalf("retried Push: %v", err)
+	}
+	if inserts, updates := e.google.EventWrites(); inserts != 4 || updates != 3 {
+		t.Errorf("retry: %d inserts and %d updates, want 4 and 3", inserts, updates)
+	}
+	if n := len(e.google.Events(dinnersCal.ID)); n != 7 || p.Status != plan.StatusSynced {
+		t.Errorf("after retry: %d events, plan %s; want 7, synced", n, p.Status)
+	}
+}
+
+func TestPushPartialFailureKeepsAChangedPlanChanged(t *testing.T) {
+	e := newEnv(t)
+	e.connectCalendar(t)
+	e.storePlan(t, week, fullWeek...)
+	first, err := e.svc.Push(t.Context(), week)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for date, name := range map[string]string{"2026-10-12": "Fish Tacos", "2026-10-13": "Ramen"} {
+		if _, err := e.svc.Swap(t.Context(), week, date, e.dinner(t, name, "regular", "stovetop", 25)); err != nil {
+			t.Fatal(err)
+		}
+	}
+	e.google.FailEventWrite(2, http.StatusInternalServerError)
+	if _, err := e.svc.Push(t.Context(), week); err == nil {
+		t.Fatal("Push succeeded, want the second event to fail")
+	}
+	p, err := e.svc.Get(t.Context(), week)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if p.Status != plan.StatusChanged || *p.CalendarSyncedAt != *first.CalendarSyncedAt {
+		t.Errorf("plan = %s synced at %v, want changed, synced at %s", p.Status, *p.CalendarSyncedAt, *first.CalendarSyncedAt)
+	}
+	ids := e.eventIDs(t, week)
+	if ids["2026-10-12"] != "" || ids["2026-10-13"] != "" {
+		t.Errorf("swapped days stored event ids %v after a failed push", ids)
+	}
+}
+
+func TestPushToStaleCalendar(t *testing.T) {
+	for name, edit := range map[string]func(*gcaltest.Google){
+		"deleted": func(g *gcaltest.Google) { g.SetCalendars(0) },
+		"read-only": func(g *gcaltest.Google) {
+			g.SetCalendars(0, gcaltest.Calendar{ID: dinnersCal.ID, Summary: "Dinners", AccessRole: "reader"})
+		},
+	} {
+		t.Run(name, func(t *testing.T) {
+			e := newEnv(t)
+			e.connectCalendar(t)
+			e.storePlan(t, week, fullWeek...)
+			edit(e.google)
+			if _, err := e.svc.Push(t.Context(), week); !errors.Is(err, gcal.ErrCalendarUnavailable) {
+				t.Errorf("Push = %v, want ErrCalendarUnavailable", err)
+			}
+			e.assertUnsynced(t, week, plan.StatusDraft)
+		})
+	}
+}
+
+func TestPushGrantNoLongerAccepted(t *testing.T) {
+	e := newEnv(t)
+	e.connectCalendar(t)
+	e.storePlan(t, week, fullWeek...)
+	e.google.RevokeGrant()
+	_, err := e.svc.Push(t.Context(), week)
+	if !errors.Is(err, gcal.ErrReconnect) {
+		t.Fatalf("Push = %v, want ErrReconnect", err)
+	}
+	assertNoSecret(t, "error", err.Error())
+	e.assertUnsynced(t, week, plan.StatusDraft)
+	// The connection is left as it is: forgetting it is not the push's to
+	// decide.
+	if _, err := db.New(e.st.Reader).GetIntegrationsGoogle(t.Context()); err != nil {
+		t.Errorf("connection after a refused grant: %v", err)
+	}
+}
+
+func TestPushFailsWhenPlanSwappedWhilePushing(t *testing.T) {
+	e := newEnv(t)
+	e.connectCalendar(t)
+	e.storePlan(t, week, fullWeek...)
+	arrived, release := e.google.HoldEvents()
+	defer release()
+	pushed := make(chan error, 1)
+	go func() {
+		_, err := e.svc.Push(t.Context(), week)
+		pushed <- err
+	}()
+	<-arrived
+	if _, err := e.svc.Swap(t.Context(), week, "2026-10-14", e.dinner(t, "Fish Tacos", "regular", "stovetop", 25)); err != nil {
+		t.Fatal(err)
+	}
+	release()
+	if err := <-pushed; !errors.Is(err, plan.ErrPlanChanged) {
+		t.Fatalf("Push = %v, want ErrPlanChanged", err)
+	}
+	e.assertUnsynced(t, week, plan.StatusDraft)
+}
+
+// kitchenCal is the calendar the tests choose after pushing to dinnersCal.
+var kitchenCal = gcaltest.Calendar{ID: "kitchen@group.calendar.google.com", Summary: "Kitchen", AccessRole: "owner"}
+
+// assertWeekOn fails unless calendar shows each of names, Monday first, on
+// its day of the week starting weekStart, and each day stores that event's
+// id.
+func (e *env) assertWeekOn(t *testing.T, calendar string, weekStart store.LocalDate, dates []string, names ...string) {
+	t.Helper()
+	events := e.google.Events(calendar)
+	stored := e.eventIDs(t, weekStart)
+	for i, date := range dates {
+		id := plan.EventID(weekStart, mustDate(date))
+		if ev := events[id]; ev.Summary != "Dinner: "+names[i] || ev.Status != "confirmed" {
+			t.Errorf("%s on %s = %q %s, want \"Dinner: %s\" confirmed", date, calendar, ev.Summary, ev.Status, names[i])
+		}
+		if stored[date] != id {
+			t.Errorf("%s stored event id %q, want %s", date, stored[date], id)
+		}
+	}
+}
+
+func TestPushAfterChoosingAnotherCalendarWritesTheWholeWeek(t *testing.T) {
+	for _, swap := range []bool{false, true} {
+		name := "push again"
+		if swap {
+			name = "swap then push"
+		}
+		t.Run(name, func(t *testing.T) {
+			e := newEnv(t)
+			e.connectCalendar(t)
+			dates := e.storePlan(t, week, fullWeek...)
+			first, err := e.svc.Push(t.Context(), week)
+			if err != nil {
+				t.Fatal(err)
+			}
+			onDinners := e.google.Events(dinnersCal.ID)
+
+			// Choosing the same calendar again keeps the plan synced.
+			e.google.SetCalendars(0, dinnersCal, kitchenCal)
+			if _, err := e.gcal.SelectCalendar(t.Context(), dinnersCal.ID); err != nil {
+				t.Fatal(err)
+			}
+			if p, err := e.svc.Get(t.Context(), week); err != nil || p.Status != plan.StatusSynced {
+				t.Fatalf("plan after choosing the same calendar = %s, %v; want synced", p.Status, err)
+			}
+
+			if _, err := e.gcal.SelectCalendar(t.Context(), kitchenCal.ID); err != nil {
+				t.Fatal(err)
+			}
+			// The plan's events are on a calendar no longer chosen.
+			p, err := e.svc.Get(t.Context(), week)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if p.Status != plan.StatusChanged || *p.CalendarSyncedAt != *first.CalendarSyncedAt {
+				t.Errorf("plan after choosing another calendar = %s synced at %v, want changed", p.Status, *p.CalendarSyncedAt)
+			}
+			for date, id := range e.eventIDs(t, week) {
+				if id != "" {
+					t.Errorf("%s kept event id %q of the calendar no longer chosen", date, id)
+				}
+			}
+
+			names := slices.Clone(fullWeek)
+			if swap {
+				fishTacos := e.dinner(t, "Fish Tacos", "regular", "stovetop", 25)
+				if _, err := e.svc.Swap(t.Context(), week, "2026-10-14", fishTacos); err != nil {
+					t.Fatal(err)
+				}
+				names[2] = "Fish Tacos"
+			}
+
+			// A push that fails part way leaves the plan changed.
+			e.google.ResetEventWrites()
+			e.google.FailEventWrite(4, http.StatusServiceUnavailable)
+			if _, err := e.svc.Push(t.Context(), week); err == nil {
+				t.Fatal("Push succeeded, want the fourth event to fail")
+			}
+			if p, err := e.svc.Get(t.Context(), week); err != nil || p.Status != plan.StatusChanged {
+				t.Errorf("plan after a failed push = %s, %v; want changed", p.Status, err)
+			}
+
+			p, err = e.svc.Push(t.Context(), week)
+			if err != nil {
+				t.Fatalf("Push: %v", err)
+			}
+			if p.Status != plan.StatusSynced {
+				t.Errorf("status = %s, want synced", p.Status)
+			}
+			if n := len(e.google.Events(kitchenCal.ID)); n != 7 {
+				t.Errorf("%s has %d events, want 7", kitchenCal.ID, n)
+			}
+			e.assertWeekOn(t, kitchenCal.ID, week, dates, names...)
+			if after := e.google.Events(dinnersCal.ID); !maps.Equal(onDinners, after) {
+				t.Errorf("%s changed:\nbefore %+v\nafter  %+v", dinnersCal.ID, onDinners, after)
+			}
+		})
+	}
+}
+
+// TestChoosingAnotherCalendarWaitsForAPush chooses another calendar while a
+// push is at Google: the choice waits until the push is recorded, then
+// forgets its events, so the next push writes the whole week to the
+// calendar now chosen.
+func TestChoosingAnotherCalendarWaitsForAPush(t *testing.T) {
+	e := newEnv(t)
+	e.connectCalendar(t)
+	dates := e.storePlan(t, week, fullWeek...)
+	e.google.SetCalendars(0, dinnersCal, kitchenCal)
+	arrived, release := e.google.HoldEvents()
+	defer release()
+	pushed := make(chan error, 1)
+	go func() {
+		_, err := e.svc.Push(t.Context(), week)
+		pushed <- err
+	}()
+	<-arrived
+	selected := make(chan error, 1)
+	go func() {
+		_, err := e.gcal.SelectCalendar(t.Context(), kitchenCal.ID)
+		selected <- err
+	}()
+	select {
+	case err := <-selected:
+		t.Fatalf("SelectCalendar finished (%v) while a push was at Google", err)
+	case <-time.After(200 * time.Millisecond):
+	}
+	release()
+	if err := <-pushed; err != nil {
+		t.Fatalf("Push: %v", err)
+	}
+	if err := <-selected; err != nil {
+		t.Fatalf("SelectCalendar: %v", err)
+	}
+	p, err := e.svc.Get(t.Context(), week)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if p.Status != plan.StatusChanged {
+		t.Errorf("plan = %s, want changed: its events are on %s", p.Status, dinnersCal.ID)
+	}
+	for date, id := range e.eventIDs(t, week) {
+		if id != "" {
+			t.Errorf("%s kept event id %q of the calendar no longer chosen", date, id)
+		}
+	}
+
+	if p, err = e.svc.Push(t.Context(), week); err != nil || p.Status != plan.StatusSynced {
+		t.Fatalf("Push = %s, %v; want synced", p.Status, err)
+	}
+	e.assertWeekOn(t, kitchenCal.ID, week, dates, fullWeek...)
+}
+
+// pushedWeeks are the weeks the disconnect tests push: the calendar and the
+// connection are the household's, so a disconnect concerns every one.
+var pushedWeeks = []store.LocalDate{week, mustDate("2026-10-19"), mustDate("2026-10-26")}
+
+// assertForgotten fails unless the plan of weekStart is changed and no day
+// keeps an event id.
+func (e *env) assertForgotten(t *testing.T, weekStart store.LocalDate, why string) {
+	t.Helper()
+	p, err := e.svc.Get(t.Context(), weekStart)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if p.Status != plan.StatusChanged {
+		t.Errorf("plan of %s %s = %s, want changed", weekStart, why, p.Status)
+	}
+	for date, id := range e.eventIDs(t, weekStart) {
+		if id != "" {
+			t.Errorf("%s kept event id %q %s", date, id, why)
+		}
+	}
+}
+
+func TestDisconnectForgetsEveryPushedWeek(t *testing.T) {
+	e := newEnv(t)
+	e.connectCalendar(t)
+	dates := map[store.LocalDate][]string{}
+	for _, w := range pushedWeeks {
+		dates[w] = e.storePlan(t, w, fullWeek...)
+		if _, err := e.svc.Push(t.Context(), w); err != nil {
+			t.Fatalf("Push %s: %v", w, err)
+		}
+	}
+	draftWeek := mustDate("2026-11-02")
+	e.storePlan(t, draftWeek, fullWeek...)
+
+	if err := e.gcal.Disconnect(t.Context()); err != nil {
+		t.Fatalf("Disconnect: %v", err)
+	}
+	for _, w := range pushedWeeks {
+		e.assertForgotten(t, w, "after disconnecting")
+	}
+	e.assertUnsynced(t, draftWeek, plan.StatusDraft)
+
+	// Connecting again chooses no calendar, so nothing is pushed until one
+	// is chosen; then a push writes the whole week to it.
+	e.google.Connect(t, e.gcal)
+	if _, err := e.svc.Push(t.Context(), week); !errors.Is(err, gcal.ErrNoCalendar) {
+		t.Fatalf("Push after connecting again = %v, want ErrNoCalendar", err)
+	}
+	e.google.SetCalendars(0, dinnersCal, kitchenCal)
+	if _, err := e.gcal.SelectCalendar(t.Context(), kitchenCal.ID); err != nil {
+		t.Fatal(err)
+	}
+	for _, w := range pushedWeeks {
+		e.assertForgotten(t, w, "after connecting again")
+		p, err := e.svc.Push(t.Context(), w)
+		if err != nil || p.Status != plan.StatusSynced {
+			t.Fatalf("Push %s = %s, %v; want synced", w, p.Status, err)
+		}
+		e.assertWeekOn(t, kitchenCal.ID, w, dates[w], fullWeek...)
+	}
+}
+
+// TestDisconnectRefusedKeepsPushedWeeks: a revoke Google refuses keeps the
+// connection and its calendar, so every pushed week stays synced to it.
+func TestDisconnectRefusedKeepsPushedWeeks(t *testing.T) {
+	e := newEnv(t)
+	e.connectCalendar(t)
+	dates := map[store.LocalDate][]string{}
+	for _, w := range pushedWeeks {
+		dates[w] = e.storePlan(t, w, fullWeek...)
+		if _, err := e.svc.Push(t.Context(), w); err != nil {
+			t.Fatalf("Push %s: %v", w, err)
+		}
+	}
+	e.google.AnswerRevoke(http.StatusServiceUnavailable, "")
+	var revokeErr *gcal.RevokeError
+	if err := e.gcal.Disconnect(t.Context()); !errors.As(err, &revokeErr) {
+		t.Fatalf("Disconnect = %v, want a *RevokeError", err)
+	}
+	for _, w := range pushedWeeks {
+		if p, err := e.svc.Get(t.Context(), w); err != nil || p.Status != plan.StatusSynced {
+			t.Errorf("plan of %s after a refused disconnect = %s, %v; want synced", w, p.Status, err)
+		}
+		e.assertWeekOn(t, dinnersCal.ID, w, dates[w], fullWeek...)
+	}
+}
+
+// TestDisconnectWaitsForAPush disconnects while a push is at Google: the
+// disconnect waits until the push is recorded, then forgets its events.
+func TestDisconnectWaitsForAPush(t *testing.T) {
+	e := newEnv(t)
+	e.connectCalendar(t)
+	e.storePlan(t, week, fullWeek...)
+	arrived, release := e.google.HoldEvents()
+	defer release()
+	pushed := make(chan error, 1)
+	go func() {
+		_, err := e.svc.Push(t.Context(), week)
+		pushed <- err
+	}()
+	<-arrived
+	disconnected := make(chan error, 1)
+	go func() {
+		disconnected <- e.gcal.Disconnect(t.Context())
+	}()
+	select {
+	case err := <-disconnected:
+		t.Fatalf("Disconnect finished (%v) while a push was at Google", err)
+	case <-time.After(200 * time.Millisecond):
+	}
+	release()
+	if err := <-pushed; err != nil {
+		t.Fatalf("Push: %v", err)
+	}
+	if err := <-disconnected; err != nil {
+		t.Fatalf("Disconnect: %v", err)
+	}
+	e.assertForgotten(t, week, "after disconnecting")
+}

internal/server/aisettings_test.go

@@ -29,7 +29,7 @@ func newAIRouter(t *testing.T) http.Handler {
 	t.Helper()
 	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
 	r, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t),
-		newTestPlan(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {Data: []byte(fixtureIndex)}})
+		newTestPlan(t), newTestGoogle(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {Data: []byte(fixtureIndex)}})
 	if err != nil {
 		t.Fatal(err)
 	}

internal/server/dinners_test.go

@@ -92,7 +92,7 @@ func newDinnersEnv(t *testing.T) *dinnersEnv {
 		t.Fatal(err)
 	}
 	e.h, err = NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), newTestAI(t),
-		svc, newTestSuggest(t), newTestPlan(t), runner, newTestPhotos(t), fstest.MapFS{"index.html": {Data: []byte(fixtureIndex)}})
+		svc, newTestSuggest(t), newTestPlan(t), newTestGoogle(t), runner, newTestPhotos(t), fstest.MapFS{"index.html": {Data: []byte(fixtureIndex)}})
 	if err != nil {
 		t.Fatal(err)
 	}

internal/server/google.go

@@ -0,0 +1,173 @@
+package server
+
+import (
+	"errors"
+	"log/slog"
+	"net/http"
+
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/auth"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal"
+)
+
+// googleConnectedPath is where a completed connect sends the browser: the
+// Google Calendar settings screen.
+const googleConnectedPath = "/settings/calendar"
+
+// getGoogleConnect sends the browser to Google's consent screen with a state
+// bound to its session. The household opens it as a top-level navigation;
+// the session cookie is SameSite=Lax, so it rides along.
+func getGoogleConnect(logger *slog.Logger, svc *gcal.Service) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Cache-Control", "no-store")
+		session, ok := auth.SessionFrom(r.Context())
+		if !ok {
+			logger.ErrorContext(r.Context(), "Google connect without a session")
+			writeError(w, r, logger, http.StatusInternalServerError, "internal", "internal error")
+			return
+		}
+		consent, err := svc.Connect(w, session)
+		if err != nil {
+			logger.ErrorContext(r.Context(), "start Google connect", "error", err)
+			writeError(w, r, logger, http.StatusInternalServerError, "internal", "internal error")
+			return
+		}
+		http.Redirect(w, r, consent, http.StatusFound)
+	}
+}
+
+// getGoogleCallback completes the connect Google redirects back with, then
+// sends the browser to the Google Calendar settings screen. Every failure is
+// an API error; none holds a token or Google's response text.
+func getGoogleCallback(logger *slog.Logger, svc *gcal.Service) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Cache-Control", "no-store")
+		ctx := r.Context()
+		session, ok := auth.SessionFrom(ctx)
+		if !ok {
+			logger.ErrorContext(ctx, "Google callback without a session")
+			writeError(w, r, logger, http.StatusInternalServerError, "internal", "internal error")
+			return
+		}
+		err := svc.Complete(w, r, session)
+		switch {
+		case err == nil:
+			http.Redirect(w, r, googleConnectedPath, http.StatusSeeOther)
+		case errors.Is(err, gcal.ErrBadState):
+			logger.WarnContext(ctx, "Google callback refused", "error", err)
+			writeError(w, r, logger, http.StatusBadRequest, "invalid_state",
+				"this Google Calendar connection expired or was not started here; connect again")
+		case errors.Is(err, gcal.ErrDenied):
+			logger.WarnContext(ctx, "Google returned an authorization error")
+			writeError(w, r, logger, http.StatusForbidden, "google_denied",
+				"Google did not grant access to your calendar; connect again to retry")
+		case errors.Is(err, gcal.ErrNoCode):
+			writeError(w, r, logger, http.StatusBadRequest, "invalid_request", "missing authorization code")
+		case errors.Is(err, gcal.ErrNoRefreshToken):
+			logger.WarnContext(ctx, "Google connect refused", "error", err)
+			writeError(w, r, logger, http.StatusBadGateway, "reconnect_required",
+				"Google did not grant lasting access to your calendar; connect Google Calendar again")
+		case errors.Is(err, gcal.ErrScopes):
+			logger.WarnContext(ctx, "Google connect refused", "error", err)
+			writeError(w, r, logger, http.StatusForbidden, "scopes_missing",
+				"allow MealQuest to see your calendars and manage their events, then connect Google Calendar again")
+		default:
+			logger.WarnContext(ctx, "Google connect failed", "error", err)
+			writeError(w, r, logger, http.StatusBadGateway, "google_failed",
+				"Google Calendar could not be connected; connect again")
+		}
+	}
+}
+
+// deleteGoogle revokes the connected account's access at Google and forgets
+// it: 204 on success, 409 not_connected when nothing is connected, 502 when
+// Google could not revoke (the connection is kept, so it can be retried).
+func deleteGoogle(logger *slog.Logger, svc *gcal.Service) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		err := svc.Disconnect(r.Context())
+		var revoke *gcal.RevokeError
+		switch {
+		case err == nil:
+			w.WriteHeader(http.StatusNoContent)
+		case errors.Is(err, gcal.ErrNotConnected):
+			writeError(w, r, logger, http.StatusConflict, "not_connected", "Google Calendar is not connected")
+		case errors.As(err, &revoke):
+			logger.WarnContext(r.Context(), "revoke Google access", "error", err)
+			writeError(w, r, logger, http.StatusBadGateway, "revoke_failed",
+				"Google could not revoke MealQuest's access; try again")
+		default:
+			logger.ErrorContext(r.Context(), "disconnect Google Calendar", "error", err)
+			writeError(w, r, logger, http.StatusInternalServerError, "internal", "internal error")
+		}
+	}
+}
+
+// maxGoogleCalendarBody bounds a PUT /integrations/google/calendar body.
+const maxGoogleCalendarBody = 4 << 10
+
+// googleCalendarChoice is the PUT /integrations/google/calendar body.
+type googleCalendarChoice struct {
+	CalendarID *string `json:"calendar_id"`
+}
+
+// getGoogleCalendars lists the connected account's calendars MealQuest can
+// push to, as [{id, summary, primary, accessRole}].
+func getGoogleCalendars(logger *slog.Logger, svc *gcal.Service) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Cache-Control", "no-store")
+		cals, err := svc.Calendars(r.Context())
+		if err != nil {
+			writeGoogleCalendarError(w, r, logger, "list Google calendars", err)
+			return
+		}
+		writeJSON(w, r, logger, http.StatusOK, cals)
+	}
+}
+
+// putGoogleCalendar chooses the calendar MealQuest pushes to and answers
+// {calendar_id, calendar_name}.
+func putGoogleCalendar(logger *slog.Logger, svc *gcal.Service) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		body, err := decodePatch[googleCalendarChoice](http.MaxBytesReader(w, r.Body, maxGoogleCalendarBody))
+		if err != nil {
+			writeError(w, r, logger, http.StatusBadRequest, "invalid_request", err.Error())
+			return
+		}
+		if body.CalendarID == nil || *body.CalendarID == "" {
+			writeError(w, r, logger, http.StatusBadRequest, "invalid_request", "calendar_id: required")
+			return
+		}
+		sel, err := svc.SelectCalendar(r.Context(), *body.CalendarID)
+		if err != nil {
+			writeGoogleCalendarError(w, r, logger, "choose Google calendar", err)
+			return
+		}
+		writeJSON(w, r, logger, http.StatusOK, sel)
+	}
+}
+
+// writeGoogleCalendarError maps a calendar listing or choice error to its
+// API error: 409 not_connected when nothing is connected, 422
+// unknown_calendar for a calendar MealQuest cannot push to, 502
+// reconnect_required when Google no longer accepts the stored grant, and 502
+// google_failed when Google refused or could not be reached.
+func writeGoogleCalendarError(w http.ResponseWriter, r *http.Request, logger *slog.Logger, action string, err error) {
+	var calendar *gcal.CalendarError
+	switch {
+	case errors.Is(err, gcal.ErrNotConnected):
+		writeError(w, r, logger, http.StatusConflict, "not_connected", "Google Calendar is not connected")
+	case errors.Is(err, gcal.ErrUnknownCalendar):
+		writeError(w, r, logger, http.StatusUnprocessableEntity, "unknown_calendar",
+			"choose one of your calendars that MealQuest can add dinners to")
+	case errors.Is(err, gcal.ErrReconnect):
+		logger.WarnContext(r.Context(), action, "error", err)
+		writeError(w, r, logger, http.StatusBadGateway, "reconnect_required",
+			"Google no longer accepts MealQuest's access to your calendar; connect Google Calendar again")
+	case errors.As(err, &calendar):
+		logger.WarnContext(r.Context(), action, "error", err)
+		writeError(w, r, logger, http.StatusBadGateway, "google_failed",
+			"Google Calendar could not be reached; try again")
+	default:
+		logger.ErrorContext(r.Context(), action, "error", err)
+		writeError(w, r, logger, http.StatusInternalServerError, "internal", "internal error")
+	}
+}

internal/server/google_test.go

@@ -0,0 +1,454 @@
+package server
+
+import (
+	"bytes"
+	"context"
+	"database/sql"
+	"encoding/json"
+	"errors"
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"slices"
+	"strings"
+	"testing"
+	"testing/fstest"
+
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/db"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal/gcaltest"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/secretbox"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/store"
+)
+
+const (
+	googleConnectPath   = "/api/v1/integrations/google/connect"
+	googleCallbackPath  = "/api/v1/integrations/google/callback"
+	googlePath          = "/api/v1/integrations/google"
+	googleCalendarsPath = "/api/v1/integrations/google/calendars"
+	googleCalendarPath  = "/api/v1/integrations/google/calendar"
+)
+
+// googleEnv is a router whose Google Calendar service talks to a fake
+// Google, with every log line it writes.
+type googleEnv struct {
+	h      http.Handler
+	google *gcaltest.Google
+	st     *store.Store
+	box    *secretbox.Box
+	logs   *bytes.Buffer
+	// seen collects every response body and header, to check none holds a
+	// secret.
+	seen strings.Builder
+}
+
+func newGoogleEnv(t *testing.T) *googleEnv {
+	t.Helper()
+	pub, err := url.Parse("https://mealquest.example")
+	if err != nil {
+		t.Fatal(err)
+	}
+	e := &googleEnv{
+		google: gcaltest.New(t, "https://mealquest.example"+gcal.CallbackPath),
+		st:     newTestStore(t),
+		box:    newTestBox(t),
+		logs:   &bytes.Buffer{},
+	}
+	svc, err := gcal.NewService(e.st, e.box, gcal.Config{
+		ClientID:     gcaltest.ClientID,
+		ClientSecret: gcaltest.ClientSecret,
+		PublicURL:    pub,
+		SecretKey:    []byte("server-secret-key"),
+		Endpoint:     e.google.Endpoint(),
+		RevokeURL:    e.google.RevokeURL(),
+		CalendarAPI:  e.google.CalendarAPI(),
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	logger := slog.New(slog.NewJSONHandler(e.logs, &slog.HandlerOptions{Level: slog.LevelDebug}))
+	e.h, err = NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), newTestAI(t),
+		newTestDinners(t), newTestSuggest(t), newTestPlan(t), svc, newTestRunner(t), newTestPhotos(t),
+		fstest.MapFS{"index.html": {Data: []byte(fixtureIndex)}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() {
+		for _, secret := range []string{gcaltest.RefreshToken, gcaltest.AccessToken, gcaltest.ClientSecret} {
+			if strings.Contains(e.seen.String(), secret) {
+				t.Errorf("a response holds a secret: %s", e.seen.String())
+			}
+			if strings.Contains(e.logs.String(), secret) {
+				t.Errorf("the logs hold a secret: %s", e.logs.String())
+			}
+		}
+	})
+	return e
+}
+
+func (e *googleEnv) serve(req *http.Request) *httptest.ResponseRecorder {
+	rec := httptest.NewRecorder()
+	e.h.ServeHTTP(rec, req)
+	e.seen.WriteString(rec.Body.String())
+	for k, vs := range rec.Header() {
+		e.seen.WriteString(k + ": " + strings.Join(vs, ", ") + "\n")
+	}
+	return rec
+}
+
+// connect starts a connect as the test session and returns Google's consent
+// URL and the connect cookie.
+func (e *googleEnv) connect(t *testing.T) (*url.URL, *http.Cookie) {
+	t.Helper()
+	rec := e.serve(signedIn(http.MethodGet, googleConnectPath, nil))
+	if rec.Code != http.StatusFound {
+		t.Fatalf("connect = %d %s, want 302", rec.Code, rec.Body)
+	}
+	if cc := rec.Header().Get("Cache-Control"); cc != "no-store" {
+		t.Errorf("connect Cache-Control = %q, want no-store", cc)
+	}
+	consent, err := url.Parse(rec.Header().Get("Location"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	var cookie *http.Cookie
+	for _, c := range rec.Result().Cookies() {
+		if c.Name == "__Host-mealquest_google" {
+			cookie = c
+		}
+	}
+	if cookie == nil {
+		t.Fatal("connect set no connect cookie")
+	}
+	return consent, cookie
+}
+
+// callback returns to the callback as the test session with the connect
+// cookie and query.
+func (e *googleEnv) callback(cookie *http.Cookie, query url.Values) *httptest.ResponseRecorder {
+	req := httptest.NewRequest(http.MethodGet, googleCallbackPath+"?"+query.Encode(), nil)
+	req.AddCookie(validSessionCookie)
+	if cookie != nil {
+		req.AddCookie(cookie)
+	}
+	return e.serve(req)
+}
+
+func (e *googleEnv) consented(consent *url.URL) url.Values {
+	q := consent.Query()
+	return url.Values{"state": {q.Get("state")}, "code": {e.google.Authorize(q.Get("code_challenge"))}}
+}
+
+func (e *googleEnv) stored(t *testing.T) bool {
+	t.Helper()
+	_, err := db.New(e.st.Reader).GetIntegrationsGoogle(context.Background())
+	if errors.Is(err, sql.ErrNoRows) {
+		return false
+	}
+	if err != nil {
+		t.Fatal(err)
+	}
+	return true
+}
+
+func errorBodyCode(t *testing.T, rec *httptest.ResponseRecorder) (code, message string) {
+	t.Helper()
+	var body struct {
+		Error apiError `json:"error"`
+	}
+	if err := json.Unmarshal(rec.Body.Bytes(), &body); err != nil {
+		t.Fatalf("decode %q: %v", rec.Body.String(), err)
+	}
+	return body.Error.Code, body.Error.Message
+}
+
+func TestGoogleConnectAndDisconnect(t *testing.T) {
+	t.Parallel()
+	e := newGoogleEnv(t)
+
+	consent, cookie := e.connect(t)
+	q := consent.Query()
+	if consent.Host != strings.TrimPrefix(e.google.Server.URL, "http://") || consent.Path != "/auth" {
+		t.Errorf("consent URL = %s, want the fake's /auth", consent)
+	}
+	if q.Get("access_type") != "offline" || q.Get("prompt") != "consent" ||
+		q.Get("scope") != strings.Join(gcal.Scopes, " ") ||
+		q.Get("redirect_uri") != "https://mealquest.example"+gcal.CallbackPath {
+		t.Errorf("consent query = %v", q)
+	}
+
+	rec := e.callback(cookie, e.consented(consent))
+	if rec.Code != http.StatusSeeOther || rec.Header().Get("Location") != "/settings/calendar" {
+		t.Fatalf("callback = %d Location %q %s, want 303 to /settings/calendar", rec.Code, rec.Header().Get("Location"), rec.Body)
+	}
+	row, err := db.New(e.st.Reader).GetIntegrationsGoogle(context.Background())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if plain, err := e.box.Decrypt(row.RefreshTokenCt); err != nil || string(plain) != gcaltest.RefreshToken {
+		t.Errorf("stored token opens to %q, %v", plain, err)
+	}
+	if row.ConnectedAt == "" {
+		t.Error("connected_at not set")
+	}
+
+	// DELETE needs the CSRF header like every other write.
+	req := httptest.NewRequest(http.MethodDelete, googlePath, nil)
+	req.AddCookie(validSessionCookie)
+	if rec := e.serve(req); rec.Code != http.StatusForbidden {
+		t.Errorf("DELETE without CSRF = %d, want 403", rec.Code)
+	}
+	if len(e.google.Revoked()) != 0 || !e.stored(t) {
+		t.Fatal("a DELETE without CSRF revoked or cleared the connection")
+	}
+
+	rec = e.serve(signedIn(http.MethodDelete, googlePath, nil))
+	if rec.Code != http.StatusNoContent || rec.Body.Len() != 0 {
+		t.Fatalf("DELETE = %d %q, want 204 with no body", rec.Code, rec.Body)
+	}
+	if got := e.google.Revoked(); !slices.Equal(got, []string{gcaltest.RefreshToken}) {
+		t.Errorf("revoked %q, want the refresh token", got)
+	}
+	if e.stored(t) {
+		t.Error("connection still stored after DELETE")
+	}
+
+	rec = e.serve(signedIn(http.MethodDelete, googlePath, nil))
+	if code, _ := errorBodyCode(t, rec); rec.Code != http.StatusConflict || code != "not_connected" {
+		t.Errorf("second DELETE = %d %s, want 409 not_connected", rec.Code, rec.Body)
+	}
+}
+
+func TestGoogleCallbackBadState(t *testing.T) {
+	t.Parallel()
+	e := newGoogleEnv(t)
+	consent, cookie := e.connect(t)
+	good := e.consented(consent)
+
+	for name, tc := range map[string]struct {
+		cookie *http.Cookie
+		query  url.Values
+	}{
+		"missing state":  {cookie, url.Values{"code": good["code"]}},
+		"wrong state":    {cookie, url.Values{"state": {"forged"}, "code": good["code"]}},
+		"missing cookie": {nil, good},
+	} {
+		rec := e.callback(tc.cookie, tc.query)
+		if code, _ := errorBodyCode(t, rec); rec.Code != http.StatusBadRequest || code != "invalid_state" {
+			t.Errorf("%s: callback = %d %s, want 400 invalid_state", name, rec.Code, rec.Body)
+		}
+	}
+	if e.google.TokenCalls() != 0 {
+		t.Error("a code was exchanged despite a bad state")
+	}
+	if e.stored(t) {
+		t.Error("a connection was stored")
+	}
+}
+
+func TestGoogleCallbackWithoutRefreshTokenAsksToReconnect(t *testing.T) {
+	t.Parallel()
+	e := newGoogleEnv(t)
+	e.google.OmitRefreshToken()
+	consent, cookie := e.connect(t)
+	rec := e.callback(cookie, e.consented(consent))
+	code, message := errorBodyCode(t, rec)
+	if rec.Code != http.StatusBadGateway || code != "reconnect_required" || !strings.Contains(message, "connect Google Calendar again") {
+		t.Errorf("callback = %d %s, want 502 reconnect_required asking to connect again", rec.Code, rec.Body)
+	}
+	if e.stored(t) {
+		t.Error("a connection was stored without a refresh token")
+	}
+}
+
+func TestGoogleCallbackFailuresAreRedacted(t *testing.T) {
+	t.Parallel()
+	e := newGoogleEnv(t)
+	e.google.FailToken(http.StatusBadRequest)
+	consent, cookie := e.connect(t)
+	rec := e.callback(cookie, e.consented(consent))
+	if code, _ := errorBodyCode(t, rec); rec.Code != http.StatusBadGateway || code != "google_failed" {
+		t.Errorf("callback = %d %s, want 502 google_failed", rec.Code, rec.Body)
+	}
+	// newGoogleEnv's cleanup checks the response and logs hold no secret.
+}
+
+func TestGoogleRevokeFailureKeepsConnection(t *testing.T) {
+	t.Parallel()
+	e := newGoogleEnv(t)
+	consent, cookie := e.connect(t)
+	if rec := e.callback(cookie, e.consented(consent)); rec.Code != http.StatusSeeOther {
+		t.Fatalf("callback = %d %s", rec.Code, rec.Body)
+	}
+	e.google.AnswerRevoke(http.StatusServiceUnavailable, "")
+	rec := e.serve(signedIn(http.MethodDelete, googlePath, nil))
+	if code, _ := errorBodyCode(t, rec); rec.Code != http.StatusBadGateway || code != "revoke_failed" {
+		t.Errorf("DELETE = %d %s, want 502 revoke_failed", rec.Code, rec.Body)
+	}
+	if !e.stored(t) {
+		t.Error("connection cleared although Google did not revoke")
+	}
+}
+
+func TestGoogleRoutesRequireSession(t *testing.T) {
+	t.Parallel()
+	e := newGoogleEnv(t)
+	for _, c := range []struct{ method, path string }{
+		{http.MethodGet, googleConnectPath},
+		{http.MethodGet, googleCallbackPath + "?state=s&code=c"},
+		{http.MethodDelete, googlePath},
+		{http.MethodGet, googleCalendarsPath},
+		{http.MethodPut, googleCalendarPath},
+	} {
+		rec := e.serve(httptest.NewRequest(c.method, c.path, nil))
+		if rec.Code != http.StatusUnauthorized || rec.Body.String() != unauthenticatedJSON {
+			t.Errorf("%s %s signed out = %d %s, want 401", c.method, c.path, rec.Code, rec.Body)
+		}
+	}
+	if e.google.TokenCalls() != 0 || len(e.google.Revoked()) != 0 || e.google.CalendarCalls() != 0 {
+		t.Error("a signed-out request reached Google")
+	}
+}
+
+// connected connects the test session's Google account and has the fake
+// list an owned primary calendar, a writable shared one and a read-only one.
+func (e *googleEnv) connected(t *testing.T) {
+	t.Helper()
+	consent, cookie := e.connect(t)
+	if rec := e.callback(cookie, e.consented(consent)); rec.Code != http.StatusSeeOther {
+		t.Fatalf("callback = %d %s", rec.Code, rec.Body)
+	}
+	e.google.SetCalendars(0,
+		gcaltest.Calendar{ID: "household@gmail.com", Summary: "household@gmail.com", Primary: true, AccessRole: "owner"},
+		gcaltest.Calendar{ID: "family@group.calendar.google.com", Summary: "Family", AccessRole: "writer", Description: "private notes"},
+		gcaltest.Calendar{ID: "holidays@group.v.calendar.google.com", Summary: "Holidays", AccessRole: "reader"},
+	)
+}
+
+func chooseCalendar(id string) *http.Request {
+	return signedIn(http.MethodPut, googleCalendarPath, strings.NewReader(`{"calendar_id":"`+id+`"}`))
+}
+
+func TestGoogleCalendarsListAndChoose(t *testing.T) {
+	t.Parallel()
+	e := newGoogleEnv(t)
+	e.connected(t)
+
+	rec := e.serve(signedIn(http.MethodGet, googleCalendarsPath, nil))
+	want := `[{"id":"household@gmail.com","summary":"household@gmail.com","primary":true,"accessRole":"owner"},` +
+		`{"id":"family@group.calendar.google.com","summary":"Family","primary":false,"accessRole":"writer"}]`
+	if rec.Code != http.StatusOK || rec.Body.String() != want {
+		t.Fatalf("GET calendars = %d %s, want 200 %s", rec.Code, rec.Body, want)
+	}
+	if cc := rec.Header().Get("Cache-Control"); cc != "no-store" {
+		t.Errorf("Cache-Control = %q, want no-store", cc)
+	}
+
+	// PUT needs the CSRF header like every other write.
+	req := httptest.NewRequest(http.MethodPut, googleCalendarPath, strings.NewReader(`{"calendar_id":"family@group.calendar.google.com"}`))
+	req.AddCookie(validSessionCookie)
+	if rec := e.serve(req); rec.Code != http.StatusForbidden {
+		t.Errorf("PUT without CSRF = %d, want 403", rec.Code)
+	}
+	if row, _ := db.New(e.st.Reader).GetIntegrationsGoogle(context.Background()); row.CalendarID.Valid {
+		t.Fatal("a PUT without CSRF chose a calendar")
+	}
+
+	rec = e.serve(chooseCalendar("family@group.calendar.google.com"))
+	if want := `{"calendar_id":"family@group.calendar.google.com","calendar_name":"Family"}`; rec.Code != http.StatusOK || rec.Body.String() != want {
+		t.Fatalf("PUT calendar = %d %s, want 200 %s", rec.Code, rec.Body, want)
+	}
+	row, err := db.New(e.st.Reader).GetIntegrationsGoogle(context.Background())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if row.CalendarID.String != "family@group.calendar.google.com" || row.CalendarName.String != "Family" {
+		t.Errorf("stored calendar = %v %v", row.CalendarID, row.CalendarName)
+	}
+
+	for _, id := range []string{"holidays@group.v.calendar.google.com", "nobody@group.calendar.google.com"} {
+		rec := e.serve(chooseCalendar(id))
+		if code, _ := errorBodyCode(t, rec); rec.Code != http.StatusUnprocessableEntity || code != "unknown_calendar" {
+			t.Errorf("PUT %s = %d %s, want 422 unknown_calendar", id, rec.Code, rec.Body)
+		}
+	}
+	if row, _ := db.New(e.st.Reader).GetIntegrationsGoogle(context.Background()); row.CalendarID.String != "family@group.calendar.google.com" {
+		t.Errorf("a refused choice replaced the stored calendar with %v", row.CalendarID)
+	}
+}
+
+func TestGoogleCalendarChoiceBadRequest(t *testing.T) {
+	t.Parallel()
+	e := newGoogleEnv(t)
+	e.connected(t)
+	calls := e.google.CalendarCalls()
+	for _, body := range []string{``, `{}`, `{"calendar_id":""}`, `{"calendar_id":null}`, `{"calendar_id":7}`,
+		`{"calendar_id":"family@group.calendar.google.com","calendar_name":"Mine"}`} {
+		rec := e.serve(signedIn(http.MethodPut, googleCalendarPath, strings.NewReader(body)))
+		if code, _ := errorBodyCode(t, rec); rec.Code != http.StatusBadRequest || code != "invalid_request" {
+			t.Errorf("PUT %q = %d %s, want 400 invalid_request", body, rec.Code, rec.Body)
+		}
+	}
+	if e.google.CalendarCalls() != calls {
+		t.Error("a bad request reached Google")
+	}
+}
+
+func TestGoogleCalendarsNotConnected(t *testing.T) {
+	t.Parallel()
+	e := newGoogleEnv(t)
+	for _, req := range []*http.Request{
+		signedIn(http.MethodGet, googleCalendarsPath, nil),
+		chooseCalendar("family@group.calendar.google.com"),
+	} {
+		rec := e.serve(req)
+		code, message := errorBodyCode(t, rec)
+		if rec.Code != http.StatusConflict || code != "not_connected" || message != "Google Calendar is not connected" {
+			t.Errorf("%s %s = %d %s, want 409 not_connected", req.Method, req.URL.Path, rec.Code, rec.Body)
+		}
+	}
+	if e.google.TokenCalls() != 0 || e.google.CalendarCalls() != 0 {
+		t.Error("Google was called with nothing connected")
+	}
+}
+
+// TestGoogleCalendarsGrantRevoked lists and chooses after the household
+// removed MealQuest's access in their Google account: 502
+// reconnect_required, and the connection is kept for the household to
+// reconnect or disconnect.
+func TestGoogleCalendarsGrantRevoked(t *testing.T) {
+	t.Parallel()
+	e := newGoogleEnv(t)
+	e.connected(t)
+	e.google.RevokeGrant()
+	for _, req := range []*http.Request{
+		signedIn(http.MethodGet, googleCalendarsPath, nil),
+		chooseCalendar("family@group.calendar.google.com"),
+	} {
+		rec := e.serve(req)
+		code, message := errorBodyCode(t, rec)
+		if rec.Code != http.StatusBadGateway || code != "reconnect_required" || !strings.Contains(message, "connect Google Calendar again") {
+			t.Errorf("%s %s = %d %s, want 502 reconnect_required", req.Method, req.URL.Path, rec.Code, rec.Body)
+		}
+	}
+	if !e.stored(t) {
+		t.Error("the connection was cleared")
+	}
+	// newGoogleEnv's cleanup checks the responses and logs hold no secret.
+}
+
+func TestGoogleCalendarsFailureIsRedacted(t *testing.T) {
+	t.Parallel()
+	e := newGoogleEnv(t)
+	e.connected(t)
+	e.google.FailCalendarList(http.StatusInternalServerError)
+	rec := e.serve(signedIn(http.MethodGet, googleCalendarsPath, nil))
+	if code, _ := errorBodyCode(t, rec); rec.Code != http.StatusBadGateway || code != "google_failed" {
+		t.Errorf("GET calendars = %d %s, want 502 google_failed", rec.Code, rec.Body)
+	}
+	if !strings.Contains(e.logs.String(), "HTTP 500") {
+		t.Errorf("logs = %s, want the failure's status", e.logs)
+	}
+	// newGoogleEnv's cleanup checks the response and logs hold no secret.
+}

internal/server/login_test.go

@@ -83,7 +83,7 @@ func newLoginRouter(t *testing.T, issuer string) http.Handler {
 		t.Fatal(err)
 	}
 	r, err := NewRouter(logger, "dev", trusted, flow, sessions, newTestSettings(t),
-		newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {Data: []byte(fixtureIndex)}})
+		newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestGoogle(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {Data: []byte(fixtureIndex)}})
 	if err != nil {
 		t.Fatal(err)
 	}

internal/server/media_test.go

@@ -51,7 +51,7 @@ func newMediaRouter(t *testing.T) (r http.Handler, id, orphan string) {
 		t.Fatal(err)
 	}
 	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
-	r, err = NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestRunner(t),
+	r, err = NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestGoogle(t), newTestRunner(t),
 		photos, fstest.MapFS{"index.html": {Data: []byte(fixtureIndex)}})
 	if err != nil {
 		t.Fatal(err)

internal/server/origin_test.go

@@ -45,7 +45,7 @@ func newOriginRouter(t *testing.T, logs io.Writer) http.Handler {
 	}
 	logger := slog.New(forwarded.LogHandler(slog.NewJSONHandler(logs, nil)))
 	r, err := NewRouter(logger, "dev", trusted, probeAuth{}, stubSessions{}, newTestSettings(t),
-		newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {Data: []byte(fixtureIndex)}})
+		newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestGoogle(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {Data: []byte(fixtureIndex)}})
 	if err != nil {
 		t.Fatal(err)
 	}

internal/server/plans.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/go-chi/chi/v5"
 
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/plan"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/store"
 )
@@ -93,6 +94,58 @@ func putPlanDay(logger *slog.Logger, svc *plan.Service) http.HandlerFunc {
 	}
 }
 
+// postPlanPush pushes the week's plan to the chosen Google calendar
+// (Push to Calendar) and answers with the plan as synced.
+func postPlanPush(logger *slog.Logger, svc *plan.Service) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		week, ok := weekStartOrFail(w, r, logger)
+		if !ok {
+			return
+		}
+		p, err := svc.Push(r.Context(), week)
+		if err != nil {
+			writePlanPushError(w, r, logger, err)
+			return
+		}
+		writeJSON(w, r, logger, http.StatusOK, p)
+	}
+}
+
+// writePlanPushError maps a Push to Calendar error to its API error: 409
+// not_connected when Google Calendar is not connected, no_calendar when no
+// calendar is chosen, calendar_unavailable when the chosen calendar was
+// deleted or is no longer writable, and plan_changed when the plan was
+// edited during the push; 502 reconnect_required when Google no longer
+// accepts the grant, and google_failed when Google refused or could not be
+// reached. A failed push leaves the plan's status as it was. Any other
+// error is the plan's, as writePlanError maps it.
+func writePlanPushError(w http.ResponseWriter, r *http.Request, logger *slog.Logger, err error) {
+	var calendar *gcal.CalendarError
+	switch {
+	case errors.Is(err, gcal.ErrNotConnected):
+		writeError(w, r, logger, http.StatusConflict, "not_connected", "Google Calendar is not connected")
+	case errors.Is(err, gcal.ErrNoCalendar):
+		writeError(w, r, logger, http.StatusConflict, "no_calendar",
+			"choose the calendar to push dinners to in Settings, then push again")
+	case errors.Is(err, gcal.ErrCalendarUnavailable):
+		logger.WarnContext(r.Context(), "push plan to Calendar", "error", err)
+		writeError(w, r, logger, http.StatusConflict, "calendar_unavailable",
+			"the chosen calendar was deleted or MealQuest can no longer add dinners to it; choose another calendar in Settings")
+	case errors.Is(err, plan.ErrPlanChanged):
+		writeError(w, r, logger, http.StatusConflict, "plan_changed", err.Error())
+	case errors.Is(err, gcal.ErrReconnect):
+		logger.WarnContext(r.Context(), "push plan to Calendar", "error", err)
+		writeError(w, r, logger, http.StatusBadGateway, "reconnect_required",
+			"Google no longer accepts MealQuest's access to your calendar; connect Google Calendar again")
+	case errors.As(err, &calendar):
+		logger.WarnContext(r.Context(), "push plan to Calendar", "error", err)
+		writeError(w, r, logger, http.StatusBadGateway, "google_failed",
+			"Google Calendar could not be reached; push again")
+	default:
+		writePlanError(w, r, logger, "push plan to Calendar", err)
+	}
+}
+
 // weekStartOrFail parses the {weekStart} path parameter, or answers 400
 // when it is not a Monday date.
 func weekStartOrFail(w http.ResponseWriter, r *http.Request, logger *slog.Logger) (store.LocalDate, bool) {

internal/server/plans_test.go

@@ -1,14 +1,15 @@
 package server
 
 import (
+	"bytes"
 	"context"
 	"database/sql"
 	"encoding/json"
 	"errors"
-	"io"
 	"log/slog"
 	"net/http"
 	"net/http/httptest"
+	"net/url"
 	"strings"
 	"sync"
 	"testing"
@@ -17,6 +18,8 @@ import (
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/ai/harness"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/ai/skills"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/db"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal/gcaltest"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/household"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/jobs"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/plan"
@@ -34,6 +37,12 @@ type plansEnv struct {
 	st       *store.Store
 	svc      *plan.Service
 	questLog string
+	// google is the fake Google the plan service pushes to; it starts
+	// unconnected.
+	google *gcaltest.Google
+	gcal   *gcal.Service
+	// logs holds every log line the router writes.
+	logs *bytes.Buffer
 }
 
 func newPlansRouter(t *testing.T) plansEnv {
@@ -43,7 +52,8 @@ func newPlansRouter(t *testing.T) plansEnv {
 	if err := household.SeedSettings(ctx, st, "America/New_York"); err != nil {
 		t.Fatal(err)
 	}
-	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
+	logs := &bytes.Buffer{}
+	logger := slog.New(slog.NewJSONHandler(logs, &slog.HandlerOptions{Level: slog.LevelDebug}))
 	runner, err := jobs.NewRunner(st, logger, 1)
 	if err != nil {
 		t.Fatal(err)
@@ -51,12 +61,26 @@ func newPlansRouter(t *testing.T) plansEnv {
 	fail := func(context.Context, string, skills.WeekRequest) (skills.Week, error) {
 		return skills.Week{}, errors.New("no model in this test")
 	}
-	svc, err := plan.NewService(st, fail, runner, logger)
+	pub := &url.URL{Scheme: "https", Host: "mealquest.example"}
+	google := gcaltest.New(t, "https://mealquest.example"+gcal.CallbackPath)
+	googleSvc, err := gcal.NewService(st, newTestBox(t), gcal.Config{
+		ClientID:     gcaltest.ClientID,
+		ClientSecret: gcaltest.ClientSecret,
+		PublicURL:    pub,
+		SecretKey:    []byte("server-secret-key"),
+		Endpoint:     google.Endpoint(),
+		RevokeURL:    google.RevokeURL(),
+		CalendarAPI:  google.CalendarAPI(),
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	svc, err := plan.NewService(st, fail, runner, googleSvc, pub, logger)
 	if err != nil {
 		t.Fatal(err)
 	}
 	h, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), newTestAI(t),
-		newTestDinners(t), newTestSuggest(t), svc, runner, newTestPhotos(t), fstest.MapFS{"index.html": {Data: []byte(fixtureIndex)}})
+		newTestDinners(t), newTestSuggest(t), svc, googleSvc, runner, newTestPhotos(t), fstest.MapFS{"index.html": {Data: []byte(fixtureIndex)}})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -90,7 +114,8 @@ func newPlansRouter(t *testing.T) plansEnv {
 			t.Fatal(err)
 		}
 	}
-	return plansEnv{h: h, st: st, svc: svc, questLog: dinner("Pad Thai", "quest_log", "stovetop", 35)}
+	return plansEnv{h: h, st: st, svc: svc, questLog: dinner("Pad Thai", "quest_log", "stovetop", 35),
+		google: google, gcal: googleSvc, logs: logs}
 }
 
 func (e plansEnv) setStatus(t *testing.T, status string) {
@@ -324,3 +349,141 @@ func TestPutPlanDay(t *testing.T) {
 		t.Errorf("PUT archived dinner = %d %v, want 409 dinner_not_plannable", rec.Code, body)
 	}
 }
+
+// pushCalendar is the calendar the push tests choose.
+var pushCalendar = gcaltest.Calendar{ID: "dinners@group.calendar.google.com", Summary: "Dinners", AccessRole: "owner"}
+
+// connectCalendar connects the fake Google and, when choose, chooses
+// pushCalendar.
+func (e plansEnv) connectCalendar(t *testing.T, choose bool) {
+	t.Helper()
+	e.google.SetCalendars(0, pushCalendar)
+	e.google.Connect(t, e.gcal)
+	if !choose {
+		return
+	}
+	if _, err := e.gcal.SelectCalendar(t.Context(), pushCalendar.ID); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// push calls POST /plans/{weekStart}/push-calendar and checks that neither
+// the response nor any log line holds a secret.
+func (e plansEnv) push(t *testing.T, weekStart string) (*httptest.ResponseRecorder, map[string]any) {
+	t.Helper()
+	rec, body := callDinners(t, e.h, http.MethodPost, plansPath+weekStart+"/push-calendar", "")
+	for _, secret := range []string{gcaltest.RefreshToken, gcaltest.AccessToken, gcaltest.ClientSecret} {
+		if strings.Contains(rec.Body.String(), secret) {
+			t.Errorf("response holds a secret: %s", rec.Body)
+		}
+		if strings.Contains(e.logs.String(), secret) {
+			t.Errorf("logs hold a secret: %s", e.logs)
+		}
+	}
+	return rec, body
+}
+
+func TestPushPlanToCalendar(t *testing.T) {
+	t.Parallel()
+	e := newPlansRouter(t)
+	e.connectCalendar(t, true)
+
+	rec, body := e.push(t, "2026-10-12")
+	if rec.Code != http.StatusOK {
+		t.Fatalf("push = %d: %s", rec.Code, rec.Body)
+	}
+	if body["status"] != "synced" || body["calendar_synced_at"] == nil {
+		t.Errorf("pushed plan = %v, want synced", body)
+	}
+	if days, _ := body["days"].([]any); len(days) != 7 {
+		t.Errorf("days = %v, want 7", body["days"])
+	}
+	if n := len(e.google.Events(pushCalendar.ID)); n != 7 {
+		t.Errorf("calendar has %d events, want 7", n)
+	}
+	monday := e.google.Events(pushCalendar.ID)[plan.EventID(mustLocalDate(t, "2026-10-12"), mustLocalDate(t, "2026-10-12"))]
+	if !strings.HasPrefix(monday.Description, "Beef Chili\nStart by 1:30 pm\nhttps://mealquest.example/dinner/") {
+		t.Errorf("Monday's description = %q", monday.Description)
+	}
+}
+
+func TestPushPlanToCalendarErrors(t *testing.T) {
+	t.Parallel()
+	for _, tc := range []struct {
+		name   string
+		week   string
+		setup  func(t *testing.T, e plansEnv)
+		status int
+		code   string
+	}{
+		{"not connected", "2026-10-12", func(*testing.T, plansEnv) {}, http.StatusConflict, "not_connected"},
+		{"no calendar chosen", "2026-10-12", func(t *testing.T, e plansEnv) { e.connectCalendar(t, false) }, http.StatusConflict, "no_calendar"},
+		{"calendar deleted", "2026-10-12", func(t *testing.T, e plansEnv) {
+			e.connectCalendar(t, true)
+			e.google.SetCalendars(0)
+		}, http.StatusConflict, "calendar_unavailable"},
+		{"calendar read-only", "2026-10-12", func(t *testing.T, e plansEnv) {
+			e.connectCalendar(t, true)
+			e.google.SetCalendars(0, gcaltest.Calendar{ID: pushCalendar.ID, Summary: "Dinners", AccessRole: "reader"})
+		}, http.StatusConflict, "calendar_unavailable"},
+		{"grant revoked", "2026-10-12", func(t *testing.T, e plansEnv) {
+			e.connectCalendar(t, true)
+			e.google.RevokeGrant()
+		}, http.StatusBadGateway, "reconnect_required"},
+		{"Google fails part way", "2026-10-12", func(t *testing.T, e plansEnv) {
+			e.connectCalendar(t, true)
+			e.google.FailEventWrite(3, http.StatusServiceUnavailable)
+		}, http.StatusBadGateway, "google_failed"},
+		{"no plan", "2026-10-19", func(t *testing.T, e plansEnv) { e.connectCalendar(t, true) }, http.StatusNotFound, "not_found"},
+		{"not a Monday", "2026-10-13", func(t *testing.T, e plansEnv) { e.connectCalendar(t, true) }, http.StatusBadRequest, "invalid_week"},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			e := newPlansRouter(t)
+			tc.setup(t, e)
+			rec, body := e.push(t, tc.week)
+			if rec.Code != tc.status || errorCode(body) != tc.code {
+				t.Errorf("push = %d %s, want %d %s", rec.Code, rec.Body, tc.status, tc.code)
+			}
+			p, err := e.svc.Get(t.Context(), mustLocalDate(t, "2026-10-12"))
+			if err != nil {
+				t.Fatal(err)
+			}
+			if p.Status != plan.StatusDraft || p.CalendarSyncedAt != nil {
+				t.Errorf("plan = %s synced at %v after a failed push, want draft", p.Status, p.CalendarSyncedAt)
+			}
+		})
+	}
+}
+
+func TestPushPlanChangedWhilePushing(t *testing.T) {
+	t.Parallel()
+	e := newPlansRouter(t)
+	e.connectCalendar(t, true)
+	arrived, release := e.google.HoldEvents()
+	defer release()
+	pushed := make(chan *httptest.ResponseRecorder, 1)
+	go func() {
+		rec := httptest.NewRecorder()
+		e.h.ServeHTTP(rec, signedIn(http.MethodPost, plansPath+"2026-10-12/push-calendar", nil))
+		pushed <- rec
+	}()
+	<-arrived
+	if _, err := e.svc.Swap(t.Context(), mustLocalDate(t, "2026-10-12"), "2026-10-13", e.questLog); err != nil {
+		t.Fatal(err)
+	}
+	release()
+	rec := <-pushed
+	if rec.Code != http.StatusConflict || !strings.Contains(rec.Body.String(), `"code":"plan_changed"`) {
+		t.Errorf("push = %d %s, want 409 plan_changed", rec.Code, rec.Body)
+	}
+}
+
+func mustLocalDate(t *testing.T, s string) store.LocalDate {
+	t.Helper()
+	d, err := store.ParseLocalDate(s)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return d
+}

internal/server/recipesearch_test.go

@@ -22,7 +22,7 @@ const (
 func newRecipeSearchRouter(t *testing.T, search *recipes.SearchSettingsService) http.Handler {
 	t.Helper()
 	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
-	r, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), search, newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestRunner(t),
+	r, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), search, newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestGoogle(t), newTestRunner(t),
 		newTestPhotos(t), fstest.MapFS{"index.html": {Data: []byte(fixtureIndex)}})
 	if err != nil {
 		t.Fatal(err)

internal/server/server.go

@@ -14,6 +14,7 @@ import (
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/dinners"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/forwarded"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/frontend"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/household"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/jobs"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/plan"
@@ -45,12 +46,15 @@ type RouteMounter interface {
 // /decline; planSvc serves GET /api/v1/plans/{weekStart}, POST
 // /api/v1/plans/{weekStart}/draft, PUT
 // /api/v1/plans/{weekStart}/days/{date}, GET /api/v1/rotation-reviews and
-// POST /api/v1/dinners/{id}/rotation-review; runner serves
+// POST /api/v1/dinners/{id}/rotation-review; googleSvc serves GET
+// /api/v1/integrations/google/connect, /callback and /calendars, PUT
+// /api/v1/integrations/google/calendar and DELETE
+// /api/v1/integrations/google; runner serves
 // POST /api/v1/jobs and GET /api/v1/jobs/{id}; photos serves
 // GET /media/photos/{id}-{size}.jpg; assets is the web build
 // served for every other GET. /health, /auth and the web build are public.
 // Requests to /api/v1 other than GET also need the session's CSRF token in CSRFHeader.
-func NewRouter(logger *slog.Logger, version string, trusted forwarded.Trusted, auth RouteMounter, sessions SessionLookup, settings *household.SettingsService, search *recipes.SearchSettingsService, ai *aisettings.Service, dinnerSvc *dinners.Service, suggestSvc *suggest.Service, planSvc *plan.Service, runner *jobs.Runner, photos PhotoFiles, assets fs.FS) (http.Handler, error) {
+func NewRouter(logger *slog.Logger, version string, trusted forwarded.Trusted, auth RouteMounter, sessions SessionLookup, settings *household.SettingsService, search *recipes.SearchSettingsService, ai *aisettings.Service, dinnerSvc *dinners.Service, suggestSvc *suggest.Service, planSvc *plan.Service, googleSvc *gcal.Service, runner *jobs.Runner, photos PhotoFiles, assets fs.FS) (http.Handler, error) {
 	if settings == nil {
 		return nil, errors.New("server: nil household settings service")
 	}
@@ -69,6 +73,9 @@ func NewRouter(logger *slog.Logger, version string, trusted forwarded.Trusted, a
 	if planSvc == nil {
 		return nil, errors.New("server: nil plan service")
 	}
+	if googleSvc == nil {
+		return nil, errors.New("server: nil Google Calendar service")
+	}
 	if runner == nil {
 		return nil, errors.New("server: nil job runner")
 	}
@@ -126,8 +133,17 @@ func NewRouter(logger *slog.Logger, version string, trusted forwarded.Trusted, a
 	apiV1.Get("/plans/{weekStart}", getPlan(logger, planSvc))
 	apiV1.Post("/plans/{weekStart}/draft", postPlanDraft(logger, planSvc))
 	apiV1.Put("/plans/{weekStart}/days/{date}", putPlanDay(logger, planSvc))
+	apiV1.Post("/plans/{weekStart}/push-calendar", postPlanPush(logger, planSvc))
 	apiV1.Get("/rotation-reviews", getRotationReviews(logger, planSvc))
 	apiV1.Post("/dinners/{id}/rotation-review", postRotationReview(logger, planSvc))
+	// connect and callback are top-level browser navigations, so they are
+	// GETs: the Lax session cookie rides both and CSRF applies to neither.
+	// The callback's state is bound to the session that started connect.
+	apiV1.Get("/integrations/google/connect", getGoogleConnect(logger, googleSvc))
+	apiV1.Get("/integrations/google/callback", getGoogleCallback(logger, googleSvc))
+	apiV1.Delete("/integrations/google", deleteGoogle(logger, googleSvc))
+	apiV1.Get("/integrations/google/calendars", getGoogleCalendars(logger, googleSvc))
+	apiV1.Put("/integrations/google/calendar", putGoogleCalendar(logger, googleSvc))
 	apiV1.Post("/jobs", postJob(logger, runner))
 	apiV1.Get("/jobs/{id}", getJob(logger, runner))
 	media.Get("/photos/{name}", getPhoto(logger, photos))

internal/server/server_test.go

@@ -11,16 +11,19 @@ import (
 	"maps"
 	"net/http"
 	"net/http/httptest"
+	"net/url"
 	"strings"
 	"testing"
 	"testing/fstest"
 
 	"github.com/go-chi/chi/v5"
+	"golang.org/x/oauth2"
 
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/ai/aisettings"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/ai/llm"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/ai/skills"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/dinners"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/household"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/jobs"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/plan"
@@ -50,7 +53,7 @@ func newTestRouterWith(t *testing.T, version string, settings *household.Setting
 		"index.html":             {Data: []byte(fixtureIndex)},
 		"assets/index-AbC123.js": {Data: []byte(fixtureAsset)},
 	}
-	r, err := NewRouter(logger, version, nil, stubAuth{}, stubSessions{}, settings, newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), runner, newTestPhotos(t), assets)
+	r, err := NewRouter(logger, version, nil, stubAuth{}, stubSessions{}, settings, newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestGoogle(t), runner, newTestPhotos(t), assets)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -199,7 +202,7 @@ func newTestPlan(t *testing.T) *plan.Service {
 	fail := func(context.Context, string, skills.WeekRequest) (skills.Week, error) {
 		return skills.Week{}, errors.New("no model in this test")
 	}
-	svc, err := plan.NewService(st, fail, runner, logger)
+	svc, err := plan.NewService(st, fail, runner, newTestGoogle(t), &url.URL{Scheme: "https", Host: "mealquest.example"}, logger)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -218,6 +221,29 @@ func newTestBox(t *testing.T) *secretbox.Box {
 	return box
 }
 
+// newTestGoogle returns a Google Calendar service over a migrated temp
+// database whose Google endpoints refuse every connection.
+func newTestGoogle(t *testing.T) *gcal.Service {
+	t.Helper()
+	pub, err := url.Parse("https://mealquest.example")
+	if err != nil {
+		t.Fatal(err)
+	}
+	svc, err := gcal.NewService(newTestStore(t), newTestBox(t), gcal.Config{
+		ClientID:     "client-id",
+		ClientSecret: "client-secret",
+		PublicURL:    pub,
+		SecretKey:    []byte("server-secret-key"),
+		Endpoint:     oauth2.Endpoint{AuthURL: "http://127.0.0.1:1/auth", TokenURL: "http://127.0.0.1:1/token"},
+		RevokeURL:    "http://127.0.0.1:1/revoke",
+		CalendarAPI:  "http://127.0.0.1:1/calendar/v3",
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	return svc
+}
+
 // newTestAI returns an AI settings service over a migrated temp database
 // with the seed AI settings and a random secret box.
 func newTestAI(t *testing.T) *aisettings.Service {
@@ -237,7 +263,7 @@ func TestNewRouterRequiresAISettings(t *testing.T) {
 	t.Parallel()
 
 	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
-	if _, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), nil, newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {}}); err == nil {
+	if _, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), nil, newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestGoogle(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {}}); err == nil {
 		t.Fatal("NewRouter accepted a nil AI settings service")
 	}
 }
@@ -246,7 +272,7 @@ func TestNewRouterRequiresSearchSettings(t *testing.T) {
 	t.Parallel()
 
 	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
-	if _, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), nil, newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {}}); err == nil {
+	if _, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), nil, newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestGoogle(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {}}); err == nil {
 		t.Fatal("NewRouter accepted a nil recipe search settings service")
 	}
 }
@@ -255,7 +281,7 @@ func TestNewRouterRequiresPhotoFiles(t *testing.T) {
 	t.Parallel()
 
 	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
-	if _, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestRunner(t), nil, fstest.MapFS{"index.html": {}}); err == nil {
+	if _, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestGoogle(t), newTestRunner(t), nil, fstest.MapFS{"index.html": {}}); err == nil {
 		t.Fatal("NewRouter accepted nil photo files")
 	}
 }
@@ -264,7 +290,7 @@ func TestNewRouterRequiresSettings(t *testing.T) {
 	t.Parallel()
 
 	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
-	if _, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, nil, newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {}}); err == nil {
+	if _, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, nil, newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestGoogle(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {}}); err == nil {
 		t.Fatal("NewRouter accepted a nil settings service")
 	}
 }
@@ -273,7 +299,7 @@ func TestNewRouterRequiresDinners(t *testing.T) {
 	t.Parallel()
 
 	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
-	if _, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), newTestAI(t), nil, newTestSuggest(t), newTestPlan(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {}}); err == nil {
+	if _, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), newTestAI(t), nil, newTestSuggest(t), newTestPlan(t), newTestGoogle(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {}}); err == nil {
 		t.Fatal("NewRouter accepted a nil dinners service")
 	}
 }
@@ -282,7 +308,7 @@ func TestNewRouterRequiresSuggestions(t *testing.T) {
 	t.Parallel()
 
 	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
-	if _, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), newTestAI(t), newTestDinners(t), nil, newTestPlan(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {}}); err == nil {
+	if _, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), newTestAI(t), newTestDinners(t), nil, newTestPlan(t), newTestGoogle(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {}}); err == nil {
 		t.Fatal("NewRouter accepted a nil suggestions service")
 	}
 }
@@ -291,16 +317,25 @@ func TestNewRouterRequiresPlan(t *testing.T) {
 	t.Parallel()
 
 	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
-	if _, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t), nil, newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {}}); err == nil {
+	if _, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t), nil, newTestGoogle(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {}}); err == nil {
 		t.Fatal("NewRouter accepted a nil plan service")
 	}
 }
 
+func TestNewRouterRequiresGoogle(t *testing.T) {
+	t.Parallel()
+
+	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
+	if _, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), nil, newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {}}); err == nil {
+		t.Fatal("NewRouter accepted a nil Google Calendar service")
+	}
+}
+
 func TestNewRouterRequiresJobRunner(t *testing.T) {
 	t.Parallel()
 
 	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
-	if _, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), nil, newTestPhotos(t), fstest.MapFS{"index.html": {}}); err == nil {
+	if _, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestGoogle(t), nil, newTestPhotos(t), fstest.MapFS{"index.html": {}}); err == nil {
 		t.Fatal("NewRouter accepted a nil job runner")
 	}
 }

internal/server/settings_test.go

@@ -277,7 +277,7 @@ func TestHouseholdSettingsWithRealSession(t *testing.T) {
 	}
 	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
 	router, err := NewRouter(logger, "dev", nil, stubAuth{}, sessions, household.NewSettingsService(st),
-		newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {Data: []byte(fixtureIndex)}})
+		newTestSearch(t), newTestAI(t), newTestDinners(t), newTestSuggest(t), newTestPlan(t), newTestGoogle(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {Data: []byte(fixtureIndex)}})
 	if err != nil {
 		t.Fatal(err)
 	}

internal/server/suggestions_test.go

@@ -45,7 +45,7 @@ func newSuggestionsRouter(t *testing.T, names ...string) (http.Handler, *store.S
 		t.Fatal(err)
 	}
 	h, err := NewRouter(logger, "dev", nil, stubAuth{}, stubSessions{}, newTestSettings(t), newTestSearch(t), newTestAI(t),
-		newTestDinners(t), svc, newTestPlan(t), runner, newTestPhotos(t), fstest.MapFS{"index.html": {Data: []byte(fixtureIndex)}})
+		newTestDinners(t), svc, newTestPlan(t), newTestGoogle(t), runner, newTestPhotos(t), fstest.MapFS{"index.html": {Data: []byte(fixtureIndex)}})
 	if err != nil {
 		t.Fatal(err)
 	}

internal/suggest/suggest_test.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"io"
 	"log/slog"
+	"net/url"
 	"slices"
 	"strings"
 	"sync"
@@ -19,6 +20,7 @@ import (
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/ai/skills"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/db"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/dinners"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/gcal"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/household"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/jobs"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/plan"
@@ -927,7 +929,7 @@ func TestLaterBatchNeverResuggestsRenamedDrop(t *testing.T) {
 	fail := func(context.Context, string, skills.WeekRequest) (skills.Week, error) {
 		return skills.Week{}, errors.New("no draft in this test")
 	}
-	planSvc, err := plan.NewService(e.st, fail, e.runner, logger)
+	planSvc, err := plan.NewService(e.st, fail, e.runner, noCalendar{}, &url.URL{Scheme: "https", Host: "meals.example.com"}, logger)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1320,3 +1322,10 @@ func TestStartBatchRefusesUnknownTrigger(t *testing.T) {
 		t.Fatal("unknown trigger accepted")
 	}
 }
+
+// noCalendar is a plan.Calendar for tests that never push.
+type noCalendar struct{}
+
+func (noCalendar) PushEvents(context.Context, []gcal.Event, func() error) error {
+	return errors.New("no calendar in this test")
+}

migrations/queries/plans.sql

@@ -7,7 +7,7 @@ WHERE week_start = ?;
 -- name: ListPlanDays :many
 -- The days of plan plan_id with their dinners, Monday first. A day with
 -- no dinner is left out.
-SELECT plan_days.date, plan_days.is_new, sqlc.embed(dinners)
+SELECT plan_days.date, plan_days.is_new, plan_days.calendar_event_id, sqlc.embed(dinners)
 FROM plan_days
 JOIN dinners ON dinners.id = plan_days.dinner_id
 WHERE plan_days.plan_id = ?
@@ -25,20 +25,59 @@ SET status = ?, ai_note = ?, revision = revision + 1, updated_at = ?
 WHERE id = ?;
 
 -- name: PutPlanDay :exec
--- Plans dinner_id on date of plan_id, keeping the day's calendar event id
--- when the day exists.
+-- Plans dinner_id on date of plan_id. An existing day keeps its calendar
+-- event id while its dinner stays the same; a new dinner clears it, since
+-- Calendar no longer shows the day as planned.
 INSERT INTO plan_days (id, plan_id, date, dinner_id, is_new, created_at, updated_at)
 VALUES (?, ?, ?, ?, ?, ?, ?)
 ON CONFLICT (plan_id, date) DO UPDATE
-SET dinner_id = excluded.dinner_id, is_new = excluded.is_new, updated_at = excluded.updated_at;
+SET dinner_id = excluded.dinner_id, is_new = excluded.is_new,
+	calendar_event_id = CASE WHEN plan_days.dinner_id IS excluded.dinner_id THEN plan_days.calendar_event_id END,
+	updated_at = excluded.updated_at;
 
 -- name: SwapPlanDay :execrows
--- Plans dinner_id on an existing day of plan_id; a date the plan does not
--- have is left as it is (0 rows).
+-- Plans dinner_id on an existing day of plan_id, clearing its calendar
+-- event id since Calendar no longer shows the day as planned; a date the
+-- plan does not have is left as it is (0 rows).
 UPDATE plan_days
-SET dinner_id = ?, is_new = ?, updated_at = ?
+SET dinner_id = ?, is_new = ?, calendar_event_id = NULL, updated_at = ?
 WHERE plan_id = ? AND date = ?;
 
+-- name: SetPlanDayCalendarEvent :execrows
+-- Records that the event calendar_event_id on Calendar shows date of
+-- plan_id as planned.
+UPDATE plan_days
+SET calendar_event_id = ?, updated_at = ?
+WHERE plan_id = ? AND date = ?;
+
+-- name: MarkWeekPlanSynced :execrows
+-- Records a Push to Calendar of plan id as it was at revision: the plan
+-- becomes synced. A plan edited since (another revision) is left as it is
+-- (0 rows).
+UPDATE week_plans
+SET status = 'synced', calendar_synced_at = ?, updated_at = ?
+WHERE id = ? AND revision = ?;
+
+-- name: MarkCalendarPlansEdited :exec
+-- Records that Calendar no longer shows the days with a calendar event id
+-- as planned, since another calendar or none is chosen: every plan with
+-- such a day is edited as MarkWeekPlanEdited does, so a synced plan becomes
+-- changed and a push that read it before is refused.
+UPDATE week_plans
+SET status = CASE WHEN status = 'synced' THEN 'changed' ELSE status END,
+	revision = revision + 1,
+	updated_at = ?
+WHERE EXISTS (
+	SELECT 1 FROM plan_days
+	WHERE plan_days.plan_id = week_plans.id AND plan_days.calendar_event_id IS NOT NULL
+);
+
+-- name: ClearCalendarEvents :exec
+-- Clears every day's calendar event id: none is on the chosen calendar.
+UPDATE plan_days
+SET calendar_event_id = NULL, updated_at = ?
+WHERE calendar_event_id IS NOT NULL;
+
 -- name: MarkWeekPlanEdited :exec
 -- Records an edit of plan id, raising its revision: a synced plan becomes
 -- changed, any other keeps its status.

migrations/queries/settings.sql

@@ -106,6 +106,16 @@ ON CONFLICT (id) DO UPDATE SET
 	updated_at = excluded.updated_at
 RETURNING *;
 
+-- name: SetIntegrationsGoogleCalendar :execrows
+-- Sets the chosen calendar; affects no row when nothing is connected.
+UPDATE integrations_google
+SET calendar_id = ?, calendar_name = ?, updated_at = ?
+WHERE id = 1;
+
+-- name: DeleteIntegrationsGoogle :exec
+DELETE FROM integrations_google
+WHERE id = 1;
+
 -- name: GetChatSettings :one
 -- Returns sql.ErrNoRows until the row exists.
 SELECT * FROM chat_settings