Add the Web Push sender for the push channel (Feature 19)

push.Sender implements notify.Sender for the "push" channel with
webpush-go and the VAPID key pair: it sends {title, body, url, tag} to
every stored subscription with a TTL of 12 hours, one request each.
Per subscription, an accepted notification records last_success_at, any
failure increments failure_count, and a 404 or 410 deletes the
subscription. Send succeeds when one device accepted it or when there
are no subscriptions (logged as nothing to send); otherwise it returns
an error so the outbox retries. Errors and logs name subscriptions by
id; a transport *url.Error is unwrapped so the endpoint is never quoted.

A mailto: VAPID subject is passed to webpush-go as its bare address,
since webpush-go prefixes mailto: itself.

The server registers the sender with the notify service.

Maestro task 32a1a4ad-9221-46de-8468-3ffce19b108c.

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

internal/push/sender.go

@@ -0,0 +1,195 @@
+package push
+
+import (
+	"context"
+	"database/sql"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"log/slog"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+
+	webpush "github.com/SherClockHolmes/webpush-go"
+
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/db"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/notify"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/store"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/vapid"
+)
+
+// pushTTL is how long a push service keeps a notification for a device
+// that is offline.
+const pushTTL = 12 * time.Hour
+
+// maxDrainBytes bounds how much of a push service response body is read.
+const maxDrainBytes = 4096
+
+// notice is what the service worker shows (web/src/push/notification.ts).
+type notice struct {
+	Title string `json:"title"`
+	Body  string `json:"body"`
+	URL   string `json:"url"`
+	Tag   string `json:"tag"`
+}
+
+// Sender is the notify.Sender of the push channel: it sends a notification
+// to every stored subscription, signed with the VAPID key pair.
+//
+// Per subscription, a notification the push service accepts records
+// last_success_at; one it refuses or cannot be sent increments
+// failure_count, and a 404 or 410 deletes the subscription, which the push
+// service no longer has. Send succeeds when at least one subscription
+// accepted the notification, and when there are no subscriptions at all.
+//
+// Errors and logs name a subscription by its id, never by its endpoint,
+// which is a capability URL.
+type Sender struct {
+	st     *store.Store
+	logger *slog.Logger
+	// subscriber is the VAPID subject as webpush-go takes it: an https://
+	// URL, or the bare email address of a mailto: subject.
+	subscriber string
+	publicKey  string
+	privateKey string
+	// client sends the push requests; tests replace it.
+	client webpush.HTTPClient
+	// now is the clock last_success_at is recorded on; tests replace it.
+	now func() time.Time
+}
+
+// NewSender returns the push channel's sender over st, signing with the
+// VAPID key pair publicKey and privateKey (vapid's encoding) and naming
+// subject, a mailto: URI or https:// URL, as the contact.
+func NewSender(st *store.Store, logger *slog.Logger, publicKey, privateKey, subject string) (*Sender, error) {
+	if st == nil {
+		return nil, errors.New("push: nil store")
+	}
+	if logger == nil {
+		return nil, errors.New("push: nil logger")
+	}
+	pub, err := vapid.ParsePublicKey(publicKey)
+	if err != nil {
+		return nil, fmt.Errorf("push: VAPID public key: %w", err)
+	}
+	priv, err := vapid.ParsePrivateKey(privateKey)
+	if err != nil {
+		return nil, fmt.Errorf("push: VAPID private key: %w", err)
+	}
+	if err := vapid.CheckPair(pub, priv); err != nil {
+		return nil, fmt.Errorf("push: VAPID keys: %w", err)
+	}
+	// webpush-go prefixes mailto: to any subject not starting with https:,
+	// so a mailto: subject is handed over as its bare address.
+	var subscriber string
+	if addr, ok := strings.CutPrefix(subject, "mailto:"); ok && addr != "" {
+		subscriber = addr
+	} else if strings.HasPrefix(subject, "https://") {
+		subscriber = subject
+	} else {
+		return nil, fmt.Errorf("push: VAPID subject %q is not a mailto: URI or https:// URL", subject)
+	}
+	return &Sender{
+		st:         st,
+		logger:     logger,
+		subscriber: subscriber,
+		publicKey:  publicKey,
+		privateKey: privateKey,
+		client:     &http.Client{},
+		now:        time.Now,
+	}, nil
+}
+
+// Send sends m to every stored subscription. It returns nil when at least
+// one accepted it or none is stored, and otherwise an error listing why
+// each failed, so the outbox retries. A database error is returned at once.
+func (s *Sender) Send(ctx context.Context, m notify.Message) error {
+	logger := s.logger.With("notification_id", m.ID, "event_key", m.EventKey)
+	subs, err := db.New(s.st.Reader).ListPushSubscriptions(ctx)
+	if err != nil {
+		return fmt.Errorf("push: list subscriptions: %w", err)
+	}
+	if len(subs) == 0 {
+		logger.InfoContext(ctx, "push notification has no subscriptions to send to; nothing sent")
+		return nil
+	}
+	message, err := json.Marshal(notice{Title: m.Payload.Title, Body: m.Payload.Body, URL: m.Payload.URL, Tag: m.Payload.Tag})
+	if err != nil {
+		return fmt.Errorf("push: encode notification: %w", err)
+	}
+
+	q := db.New(s.st.Writer)
+	delivered := 0
+	var failures []string
+	for _, sub := range subs {
+		status, err := s.sendOne(ctx, message, sub)
+		switch {
+		case err == nil && status >= 200 && status < 300:
+			delivered++
+			at := sql.NullString{String: timestamp(s.now()), Valid: true}
+			if err := q.RecordPushSuccess(ctx, db.RecordPushSuccessParams{LastSuccessAt: at, ID: sub.ID}); err != nil {
+				return fmt.Errorf("push: record success of subscription %s: %w", sub.ID, err)
+			}
+			continue
+		case err == nil && (status == http.StatusNotFound || status == http.StatusGone):
+			failures = append(failures, fmt.Sprintf("subscription %s gone (status %d), removed", sub.ID, status))
+			logger.InfoContext(ctx, "push subscription gone; removed", "subscription_id", sub.ID, "status", status)
+			if err := q.DeletePushSubscriptionByID(ctx, sub.ID); err != nil {
+				return fmt.Errorf("push: remove gone subscription %s: %w", sub.ID, err)
+			}
+			continue
+		case err == nil:
+			failures = append(failures, fmt.Sprintf("subscription %s: status %d", sub.ID, status))
+		default:
+			failures = append(failures, fmt.Sprintf("subscription %s: %v", sub.ID, err))
+		}
+		if err := q.RecordPushFailure(ctx, sub.ID); err != nil {
+			return fmt.Errorf("push: record failure of subscription %s: %w", sub.ID, err)
+		}
+	}
+	if delivered == 0 {
+		return fmt.Errorf("push: no subscription accepted the notification: %s", strings.Join(failures, "; "))
+	}
+	if len(failures) > 0 {
+		logger.WarnContext(ctx, "push notification not accepted by every subscription",
+			"delivered", delivered, "failures", strings.Join(failures, "; "))
+	}
+	return nil
+}
+
+// sendOne sends message to sub and returns the push service's status. Its
+// error never quotes the endpoint.
+func (s *Sender) sendOne(ctx context.Context, message []byte, sub db.ListPushSubscriptionsRow) (int, error) {
+	resp, err := webpush.SendNotificationWithContext(ctx, message, &webpush.Subscription{
+		Endpoint: sub.Endpoint,
+		Keys:     webpush.Keys{Auth: sub.Auth, P256dh: sub.P256dh},
+	}, &webpush.Options{
+		HTTPClient:      s.client,
+		Subscriber:      s.subscriber,
+		TTL:             int(pushTTL / time.Second),
+		VAPIDPublicKey:  s.publicKey,
+		VAPIDPrivateKey: s.privateKey,
+	})
+	if err != nil {
+		// A *url.Error quotes the request URL, the endpoint; keep only
+		// its cause.
+		var ue *url.Error
+		if errors.As(err, &ue) {
+			return 0, fmt.Errorf("request failed: %w", ue.Err)
+		}
+		return 0, err
+	}
+	defer resp.Body.Close()
+	// The status is the outcome; the body is read only so the connection
+	// can be reused.
+	io.CopyN(io.Discard, resp.Body, maxDrainBytes)
+	return resp.StatusCode, nil
+}
+
+// timestamp returns t in the stored UTC RFC 3339 form.
+func timestamp(t time.Time) string {
+	return store.Timestamp{Time: t.UTC().Truncate(time.Millisecond)}.String()
+}

internal/push/sender_test.go

@@ -0,0 +1,520 @@
+package push
+
+import (
+	"bytes"
+	"context"
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/ecdh"
+	"crypto/hkdf"
+	"crypto/rand"
+	"crypto/sha256"
+	"database/sql"
+	"encoding/base64"
+	"encoding/binary"
+	"encoding/json"
+	"io"
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/household"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/notify"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/store"
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/vapid"
+)
+
+const subject = "mailto:kitchen@example.com"
+
+// sentAt is the sender's fake clock.
+var sentAt = time.Date(2026, 10, 9, 17, 0, 0, 0, time.UTC)
+
+// device is a browser's push subscription with the private half of its
+// keys, so a test can read what was sent to it.
+type device struct {
+	path string
+	key  *ecdh.PrivateKey
+	auth []byte
+}
+
+func newDevice(t *testing.T, path string) device {
+	t.Helper()
+	k, err := ecdh.P256().GenerateKey(rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	auth := make([]byte, 16)
+	rand.Read(auth)
+	return device{path: path, key: k, auth: auth}
+}
+
+// request is one request the push service received.
+type request struct {
+	path   string
+	header http.Header
+	body   []byte
+}
+
+// pushService is an httptest push service answering each path with its
+// status.
+type pushService struct {
+	srv    *httptest.Server
+	status map[string]int
+
+	mu  sync.Mutex
+	got []request
+}
+
+func newPushService(t *testing.T, status map[string]int) *pushService {
+	t.Helper()
+	ps := &pushService{status: status}
+	ps.srv = httptest.NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		body, err := io.ReadAll(r.Body)
+		if err != nil {
+			t.Error(err)
+		}
+		ps.mu.Lock()
+		ps.got = append(ps.got, request{path: r.URL.Path, header: r.Header.Clone(), body: body})
+		ps.mu.Unlock()
+		code, ok := ps.status[r.URL.Path]
+		if !ok {
+			t.Errorf("unexpected push to %s", r.URL.Path)
+			code = http.StatusBadRequest
+		}
+		w.WriteHeader(code)
+	}))
+	t.Cleanup(ps.srv.Close)
+	return ps
+}
+
+func (ps *pushService) requests() []request {
+	ps.mu.Lock()
+	defer ps.mu.Unlock()
+	return append([]request(nil), ps.got...)
+}
+
+// newTestSender returns a sender over a migrated store with the devices
+// subscribed to ps, and the VAPID key pair it signs with.
+func newTestSender(t *testing.T, ps *pushService, devices ...device) (*Sender, *store.Store, vapid.KeyPair) {
+	t.Helper()
+	svc, st := newTestService(t)
+	for _, d := range devices {
+		_, err := svc.Subscribe(context.Background(), SubscribeRequest{
+			Endpoint: ps.srv.URL + d.path,
+			P256dh:   keyEncoding.EncodeToString(d.key.PublicKey().Bytes()),
+			Auth:     keyEncoding.EncodeToString(d.auth),
+		})
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+	pair, err := vapid.Generate()
+	if err != nil {
+		t.Fatal(err)
+	}
+	s, err := NewSender(st, slog.New(slog.NewTextHandler(io.Discard, nil)), pair.PublicKey, pair.PrivateKey, subject)
+	if err != nil {
+		t.Fatal(err)
+	}
+	s.client = ps.srv.Client()
+	s.now = func() time.Time { return sentAt }
+	return s, st, pair
+}
+
+func message() notify.Message {
+	return notify.Message{
+		ID:       "01NOTIFICATION",
+		EventKey: "plan_ready:2026-10-12",
+		Channel:  notify.ChannelPush,
+		Payload: notify.Payload{
+			Event: notify.PlanReady,
+			Title: "This week's plan is ready",
+			Body:  "Five dinners on the Draft board.",
+			URL:   "/plan",
+			Tag:   "plan_ready:2026-10-12",
+			Week:  "2026-10-12",
+		},
+		Attempt: 1,
+	}
+}
+
+// pushState is a subscription's delivery record.
+type pushState struct {
+	failures    int
+	lastSuccess sql.NullString
+}
+
+// states returns the delivery record of each stored subscription by path.
+func states(t *testing.T, st *store.Store, ps *pushService) map[string]pushState {
+	t.Helper()
+	rs, err := st.Reader.Query(`SELECT endpoint, failure_count, last_success_at FROM push_subscriptions`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer rs.Close()
+	got := map[string]pushState{}
+	for rs.Next() {
+		var ep string
+		var s pushState
+		if err := rs.Scan(&ep, &s.failures, &s.lastSuccess); err != nil {
+			t.Fatal(err)
+		}
+		got[strings.TrimPrefix(ep, ps.srv.URL)] = s
+	}
+	if err := rs.Err(); err != nil {
+		t.Fatal(err)
+	}
+	return got
+}
+
+// decrypt reads an aes128gcm push message body (RFC 8291) as d.
+func decrypt(t *testing.T, d device, body []byte) []byte {
+	t.Helper()
+	if len(body) < 21 {
+		t.Fatalf("body of %d bytes has no header", len(body))
+	}
+	salt, rs, idLen := body[:16], binary.BigEndian.Uint32(body[16:20]), int(body[20])
+	if rs != 4096 || idLen != 65 {
+		t.Fatalf("record size %d, key id length %d", rs, idLen)
+	}
+	asPublic, ciphertext := body[21:21+idLen], body[21+idLen:]
+	peer, err := ecdh.P256().NewPublicKey(asPublic)
+	if err != nil {
+		t.Fatal(err)
+	}
+	secret, err := d.key.ECDH(peer)
+	if err != nil {
+		t.Fatal(err)
+	}
+	info := append(append([]byte("WebPush: info\x00"), d.key.PublicKey().Bytes()...), asPublic...)
+	ikm, err := hkdf.Key(sha256.New, secret, d.auth, string(info), 32)
+	if err != nil {
+		t.Fatal(err)
+	}
+	cek, err := hkdf.Key(sha256.New, ikm, salt, "Content-Encoding: aes128gcm\x00", 16)
+	if err != nil {
+		t.Fatal(err)
+	}
+	nonce, err := hkdf.Key(sha256.New, ikm, salt, "Content-Encoding: nonce\x00", 12)
+	if err != nil {
+		t.Fatal(err)
+	}
+	block, err := aes.NewCipher(cek)
+	if err != nil {
+		t.Fatal(err)
+	}
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		t.Fatal(err)
+	}
+	plain, err := gcm.Open(nil, nonce, ciphertext, nil)
+	if err != nil {
+		t.Fatalf("decrypt: %v", err)
+	}
+	plain = bytes.TrimRight(plain, "\x00")
+	if len(plain) == 0 || plain[len(plain)-1] != 0x02 {
+		t.Fatal("no last-record delimiter")
+	}
+	return plain[:len(plain)-1]
+}
+
+// vapidClaims checks the VAPID Authorization header names pair's public key
+// and returns its token's claims (the signature is not checked).
+func vapidClaims(t *testing.T, header string, pair vapid.KeyPair) map[string]any {
+	t.Helper()
+	token, key, ok := strings.Cut(strings.TrimPrefix(header, "vapid t="), ", k=")
+	if !ok || !strings.HasPrefix(header, "vapid t=") {
+		t.Fatalf("Authorization = %q, want vapid t=…, k=…", header)
+	}
+	if key != pair.PublicKey {
+		t.Errorf("k = %q, want the VAPID public key %q", key, pair.PublicKey)
+	}
+	parts := strings.Split(token, ".")
+	if len(parts) != 3 {
+		t.Fatalf("token has %d parts", len(parts))
+	}
+	raw, err := base64.RawURLEncoding.DecodeString(parts[1])
+	if err != nil {
+		t.Fatal(err)
+	}
+	var claims map[string]any
+	if err := json.Unmarshal(raw, &claims); err != nil {
+		t.Fatal(err)
+	}
+	return claims
+}
+
+func TestSendDeliversToEveryDevice(t *testing.T) {
+	phone, tablet := newDevice(t, "/push/phone"), newDevice(t, "/push/tablet")
+	ps := newPushService(t, map[string]int{phone.path: http.StatusCreated, tablet.path: http.StatusCreated})
+	s, st, pair := newTestSender(t, ps, phone, tablet)
+
+	if err := s.Send(context.Background(), message()); err != nil {
+		t.Fatalf("Send: %v", err)
+	}
+
+	reqs := ps.requests()
+	if len(reqs) != 2 {
+		t.Fatalf("push service got %d requests, want 2", len(reqs))
+	}
+	for _, r := range reqs {
+		d := phone
+		if r.path == tablet.path {
+			d = tablet
+		}
+		if got := r.header.Get("TTL"); got != "43200" {
+			t.Errorf("%s: TTL = %q, want 43200 (12 hours)", r.path, got)
+		}
+		if got := r.header.Get("Content-Encoding"); got != "aes128gcm" {
+			t.Errorf("%s: Content-Encoding = %q", r.path, got)
+		}
+		claims := vapidClaims(t, r.header.Get("Authorization"), pair)
+		if claims["sub"] != subject {
+			t.Errorf("%s: VAPID sub = %v, want %s", r.path, claims["sub"], subject)
+		}
+		if claims["aud"] != ps.srv.URL {
+			t.Errorf("%s: VAPID aud = %v, want %s", r.path, claims["aud"], ps.srv.URL)
+		}
+		var got map[string]string
+		if err := json.Unmarshal(decrypt(t, d, r.body), &got); err != nil {
+			t.Fatal(err)
+		}
+		want := map[string]string{
+			"title": "This week's plan is ready",
+			"body":  "Five dinners on the Draft board.",
+			"url":   "/plan",
+			"tag":   "plan_ready:2026-10-12",
+		}
+		if len(got) != len(want) {
+			t.Errorf("%s: payload = %v, want %v", r.path, got, want)
+		}
+		for k, v := range want {
+			if got[k] != v {
+				t.Errorf("%s: payload %s = %q, want %q", r.path, k, got[k], v)
+			}
+		}
+	}
+
+	want := pushState{lastSuccess: sql.NullString{String: "2026-10-09T17:00:00Z", Valid: true}}
+	for path, got := range states(t, st, ps) {
+		if got.failures != want.failures || got.lastSuccess.Valid != want.lastSuccess.Valid ||
+			!sameInstant(t, got.lastSuccess.String, want.lastSuccess.String) {
+			t.Errorf("%s: state = %+v, want %+v", path, got, want)
+		}
+	}
+}
+
+func sameInstant(t *testing.T, a, b string) bool {
+	t.Helper()
+	ta, err := time.Parse(time.RFC3339Nano, a)
+	if err != nil {
+		t.Fatalf("last_success_at %q is not RFC 3339: %v", a, err)
+	}
+	tb, err := time.Parse(time.RFC3339Nano, b)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return ta.Equal(tb) && strings.HasSuffix(a, "Z")
+}
+
+func TestSendRemovesGoneSubscriptions(t *testing.T) {
+	for _, status := range []int{http.StatusNotFound, http.StatusGone} {
+		t.Run(http.StatusText(status), func(t *testing.T) {
+			gone := newDevice(t, "/push/gone")
+			ps := newPushService(t, map[string]int{gone.path: status})
+			s, st, _ := newTestSender(t, ps, gone)
+
+			err := s.Send(context.Background(), message())
+			if err == nil {
+				t.Fatal("Send with only a gone subscription succeeded, want an error so the outbox retries")
+			}
+			if strings.Contains(err.Error(), ps.srv.URL) {
+				t.Errorf("error %q quotes the endpoint", err)
+			}
+			if got := states(t, st, ps); len(got) != 0 {
+				t.Errorf("subscriptions = %v, want the gone one removed", got)
+			}
+		})
+	}
+}
+
+func TestSendSucceedsWhenOneDeviceAccepts(t *testing.T) {
+	ok, gone, broken := newDevice(t, "/push/ok"), newDevice(t, "/push/gone"), newDevice(t, "/push/broken")
+	ps := newPushService(t, map[string]int{
+		ok.path: http.StatusCreated, gone.path: http.StatusGone, broken.path: http.StatusInternalServerError,
+	})
+	s, st, _ := newTestSender(t, ps, ok, gone, broken)
+
+	if err := s.Send(context.Background(), message()); err != nil {
+		t.Fatalf("Send: %v", err)
+	}
+	got := states(t, st, ps)
+	if len(got) != 2 {
+		t.Fatalf("subscriptions = %v, want ok and broken kept, gone removed", got)
+	}
+	if s := got[ok.path]; !s.lastSuccess.Valid || s.failures != 0 {
+		t.Errorf("ok = %+v, want last_success_at set and no failures", s)
+	}
+	if s := got[broken.path]; s.lastSuccess.Valid || s.failures != 1 {
+		t.Errorf("broken = %+v, want one failure and no success", s)
+	}
+}
+
+func TestSendServerErrorIsRetryable(t *testing.T) {
+	broken := newDevice(t, "/push/broken")
+	ps := newPushService(t, map[string]int{broken.path: http.StatusInternalServerError})
+	s, st, _ := newTestSender(t, ps, broken)
+
+	for want := 1; want <= 2; want++ {
+		err := s.Send(context.Background(), message())
+		if err == nil {
+			t.Fatal("Send with only a failing subscription succeeded, want an error so the outbox retries")
+		}
+		if !strings.Contains(err.Error(), "status 500") || strings.Contains(err.Error(), ps.srv.URL) {
+			t.Errorf("error = %q, want the status and no endpoint", err)
+		}
+		got := states(t, st, ps)[broken.path]
+		if got.failures != want || got.lastSuccess.Valid {
+			t.Errorf("after send %d: state = %+v, want failure_count %d and no success", want, got, want)
+		}
+	}
+}
+
+func TestSendTransportErrorDoesNotQuoteEndpoint(t *testing.T) {
+	d := newDevice(t, "/push/secret-token")
+	ps := newPushService(t, map[string]int{})
+	s, st, _ := newTestSender(t, ps, d)
+	ps.srv.Close()
+
+	err := s.Send(context.Background(), message())
+	if err == nil {
+		t.Fatal("Send to a closed push service succeeded")
+	}
+	if strings.Contains(err.Error(), "secret-token") {
+		t.Errorf("error %q quotes the endpoint", err)
+	}
+	if got := states(t, st, ps)[d.path]; got.failures != 1 {
+		t.Errorf("state = %+v, want one failure", got)
+	}
+}
+
+func TestSendWithNoSubscriptionsIsSent(t *testing.T) {
+	ps := newPushService(t, map[string]int{})
+	s, _, _ := newTestSender(t, ps)
+
+	if err := s.Send(context.Background(), message()); err != nil {
+		t.Fatalf("Send with no subscriptions = %v, want nil", err)
+	}
+	if n := len(ps.requests()); n != 0 {
+		t.Errorf("push service got %d requests, want none", n)
+	}
+}
+
+// TestOutboxDelivery runs the sender under the notify worker and checks the
+// outbox row each outcome leaves.
+func TestOutboxDelivery(t *testing.T) {
+	cases := []struct {
+		name       string
+		status     map[string]int // by device path; nil for no devices
+		wantStatus string
+		wantError  bool
+	}{
+		{"delivered", map[string]int{"/push/ok": http.StatusCreated}, "sent", false},
+		{"server error", map[string]int{"/push/broken": http.StatusInternalServerError}, "pending", true},
+		{"no subscriptions", nil, "sent", false},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			ps := newPushService(t, tc.status)
+			var devices []device
+			for path := range tc.status {
+				devices = append(devices, newDevice(t, path))
+			}
+			s, st, _ := newTestSender(t, ps, devices...)
+			ctx, cancel := context.WithCancel(context.Background())
+			if err := household.SeedNotificationPrefs(ctx, st); err != nil {
+				t.Fatal(err)
+			}
+			if _, err := st.Writer.Exec(`UPDATE notification_prefs SET push = 1, chat = 0 WHERE event = 'plan_ready'`); err != nil {
+				t.Fatal(err)
+			}
+			n, err := notify.NewService(st, slog.New(slog.NewTextHandler(io.Discard, nil)))
+			if err != nil {
+				t.Fatal(err)
+			}
+			if err := n.Register(notify.ChannelPush, s); err != nil {
+				t.Fatal(err)
+			}
+			if err := n.Start(ctx); err != nil {
+				t.Fatal(err)
+			}
+			defer func() { cancel(); n.Wait() }()
+			if err := n.Emit(ctx, notify.Event{
+				Type: notify.PlanReady, Key: "plan_ready:2026-10-12", Title: "This week's plan is ready", URL: "/plan",
+			}); err != nil {
+				t.Fatal(err)
+			}
+
+			var status string
+			var attempts int
+			var lastError sql.NullString
+			deadline := time.Now().Add(10 * time.Second)
+			for {
+				err := st.Reader.QueryRow(`SELECT status, attempts, last_error FROM notification_outbox
+					WHERE event_key = 'plan_ready:2026-10-12' AND channel = 'push'`).Scan(&status, &attempts, &lastError)
+				if err != nil {
+					t.Fatal(err)
+				}
+				if attempts > 0 {
+					break
+				}
+				if time.Now().After(deadline) {
+					t.Fatal("the worker did not deliver the notification")
+				}
+				time.Sleep(10 * time.Millisecond)
+			}
+			if status != tc.wantStatus || attempts != 1 || lastError.Valid != tc.wantError {
+				t.Errorf("outbox row: status %s, attempts %d, last_error %v; want %s, 1, error %v",
+					status, attempts, lastError, tc.wantStatus, tc.wantError)
+			}
+		})
+	}
+}
+
+func TestNewSenderRefusesBadConfig(t *testing.T) {
+	_, st := newTestService(t)
+	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
+	pair, err := vapid.Generate()
+	if err != nil {
+		t.Fatal(err)
+	}
+	other, err := vapid.Generate()
+	if err != nil {
+		t.Fatal(err)
+	}
+	cases := map[string]struct{ public, private, subject string }{
+		"bad public key":  {"nope", pair.PrivateKey, subject},
+		"bad private key": {pair.PublicKey, "nope", subject},
+		"mismatched pair": {pair.PublicKey, other.PrivateKey, subject},
+		"bad subject":     {pair.PublicKey, pair.PrivateKey, "kitchen@example.com"},
+		"empty mailto":    {pair.PublicKey, pair.PrivateKey, "mailto:"},
+	}
+	for name, c := range cases {
+		t.Run(name, func(t *testing.T) {
+			_, err := NewSender(st, logger, c.public, c.private, c.subject)
+			if err == nil {
+				t.Fatal("NewSender succeeded")
+			}
+			if strings.Contains(err.Error(), pair.PrivateKey) || strings.Contains(err.Error(), other.PrivateKey) {
+				t.Errorf("error %q quotes the private key", err)
+			}
+		})
+	}
+	if _, err := NewSender(st, logger, pair.PublicKey, pair.PrivateKey, "https://kitchen.example.com/contact"); err != nil {
+		t.Errorf("https subject: %v", err)
+	}
+}