Keep %#v of every LLM adapter error free of the API key (MQ-03)

%#v prints struct field names, so a key that spells one (for example
"body" on ProviderError) leaked even though Error() was redacted.

- llm.ProviderError and llm.RateLimitedError gain GoString returning
  their already-redacted Error text.
- Both adapters' transportFailure now holds its fully redacted text and
  gains GoString.
- The redact backstop now wraps every non-nil error when a key is set,
  so the returned error and every unwrapped layer print through
  redactedError.GoString, never a raw struct such as fmt.wrapError.
- redactedError.As also refuses a match whose %#v form holds the key.
- Contract test in both adapters: field-name keys (body, status, text,
  RetryAfter, msg, err, key, kind) on HTTP 500 "down" and 429, checking
  %#v of the returned error, every unwrapped layer and errors.As results.

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

internal/ai/llm/anthropic/anthropic.go

@@ -0,0 +1,560 @@
+// Package anthropic is the llm.Provider adapter for Anthropic's Messages
+// API. It calls POST {base}/v1/messages and GET {base}/v1/models over plain
+// net/http.
+//
+// The adapter never logs, and no error it returns contains the API key:
+// errors do not quote caller- or vendor-supplied text, and every exported
+// method passes its error through redact as a backstop.
+package anthropic
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"math"
+	"net"
+	"net/http"
+	"net/url"
+	"reflect"
+	"regexp"
+	"strconv"
+	"strings"
+	"time"
+
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/ai/llm"
+)
+
+// APIVersion is the Messages API version sent as the anthropic-version
+// header.
+const APIVersion = "2023-06-01"
+
+// Config configures a Provider.
+type Config struct {
+	// BaseURL is the API root the /v1 endpoint paths are appended to, e.g.
+	// "https://api.anthropic.com".
+	BaseURL string
+	// APIKey is sent as the x-api-key header. It must not be empty.
+	APIKey string
+	// Model is the model Generate requests. ListModels and Verify do not
+	// need it.
+	Model string
+	// MaxTokens is the max_tokens Generate sends when a Request sets none:
+	// the Messages API requires one. It must be positive.
+	MaxTokens int
+}
+
+// Provider is an Anthropic Messages API llm.Provider.
+type Provider struct {
+	base      string
+	apiKey    string
+	model     string
+	maxTokens int
+	client    *http.Client
+}
+
+var _ llm.Provider = (*Provider)(nil)
+
+// New validates cfg and returns a Provider.
+func New(cfg Config) (*Provider, error) {
+	p, err := newFromConfig(cfg)
+	if err != nil {
+		return nil, redact(err, cfg.APIKey)
+	}
+	return p, nil
+}
+
+func newFromConfig(cfg Config) (*Provider, error) {
+	// No error from New quotes caller-supplied text: any of it may equal or
+	// contain the API key. Base URL errors never echo the URL.
+	u, err := url.Parse(cfg.BaseURL)
+	if err != nil {
+		return nil, errors.New("anthropic: base URL does not parse")
+	}
+	if (u.Scheme != "http" && u.Scheme != "https") || u.Host == "" {
+		return nil, errors.New("anthropic: base URL must be an absolute http or https URL")
+	}
+	// A trailing "?" or "#" parses to an empty query or fragment, yet the
+	// endpoint path appended to it would land in the query or fragment.
+	if u.User != nil || strings.ContainsAny(cfg.BaseURL, "?#") {
+		return nil, errors.New("anthropic: base URL must not carry credentials, a query or a fragment")
+	}
+	if cfg.APIKey == "" {
+		return nil, errors.New("anthropic: no API key configured")
+	}
+	if !validHeaderValue(cfg.APIKey) {
+		return nil, errors.New("anthropic: API key has a control character")
+	}
+	if cfg.MaxTokens <= 0 {
+		return nil, errors.New("anthropic: max tokens must be positive")
+	}
+	return &Provider{
+		base:      strings.TrimRight(cfg.BaseURL, "/"),
+		apiKey:    cfg.APIKey,
+		model:     cfg.Model,
+		maxTokens: cfg.MaxTokens,
+		client:    noRedirectClient(),
+	}, nil
+}
+
+// validHeaderValue reports whether value is an RFC 9110 field-value: no
+// control characters other than horizontal tab, so no CR, LF or DEL.
+func validHeaderValue(value string) bool {
+	for i := 0; i < len(value); i++ {
+		if c := value[i]; (c < 0x20 && c != '\t') || c == 0x7f {
+			return false
+		}
+	}
+	return true
+}
+
+// toolName is the pattern the Messages API requires of a tool name.
+var toolName = regexp.MustCompile(`^[a-zA-Z0-9_-]{1,64}$`)
+
+// maxResponseBody caps a successful response body; a larger one is an error.
+const maxResponseBody = 16 << 20
+
+// maxErrorBody caps how much of an error response body is read. It is far
+// above llm.MaxBodyExcerpt, so redaction still sees every secret that could
+// reach the excerpt.
+const maxErrorBody = 64 << 10
+
+type message struct {
+	Role    string `json:"role"`
+	Content string `json:"content"`
+}
+
+type tool struct {
+	Name        string          `json:"name"`
+	InputSchema json.RawMessage `json:"input_schema"`
+}
+
+type toolChoice struct {
+	Type string `json:"type"`
+	Name string `json:"name"`
+}
+
+type messagesRequest struct {
+	Model       string      `json:"model"`
+	MaxTokens   int         `json:"max_tokens"`
+	System      string      `json:"system,omitempty"`
+	Messages    []message   `json:"messages"`
+	Temperature *float64    `json:"temperature,omitempty"`
+	Tools       []tool      `json:"tools,omitempty"`
+	ToolChoice  *toolChoice `json:"tool_choice,omitempty"`
+}
+
+type messagesResponse struct {
+	Type    string `json:"type"`
+	Model   string `json:"model"`
+	Content []struct {
+		Type  string          `json:"type"`
+		Text  string          `json:"text"`
+		Name  string          `json:"name"`
+		Input json.RawMessage `json:"input"`
+	} `json:"content"`
+	StopReason string `json:"stop_reason"`
+	Usage      struct {
+		InputTokens  int `json:"input_tokens"`
+		OutputTokens int `json:"output_tokens"`
+	} `json:"usage"`
+}
+
+// Generate sends req to {base}/v1/messages. A Request with a Schema is sent
+// as one tool whose input_schema is the schema, with tool_choice forcing
+// it; Response.JSON is then that tool's input.
+func (p *Provider) Generate(ctx context.Context, req llm.Request) (llm.Response, error) {
+	resp, err := p.generate(ctx, req)
+	return resp, redact(err, p.apiKey)
+}
+
+func (p *Provider) generate(ctx context.Context, req llm.Request) (llm.Response, error) {
+	if err := req.Validate(); err != nil {
+		return llm.Response{}, fmt.Errorf("anthropic: generate: %w", err)
+	}
+	if p.model == "" {
+		return llm.Response{}, errors.New("anthropic: generate: no model configured")
+	}
+	body := messagesRequest{
+		Model:       p.model,
+		MaxTokens:   p.maxTokens,
+		System:      req.System,
+		Temperature: req.Temperature,
+	}
+	if req.MaxTokens > 0 {
+		body.MaxTokens = req.MaxTokens
+	}
+	if req.Schema != nil {
+		if !toolName.MatchString(req.Schema.Name) {
+			return llm.Response{}, errors.New("anthropic: generate: schema name is not a valid tool name")
+		}
+		body.Tools = []tool{{Name: req.Schema.Name, InputSchema: req.Schema.Schema}}
+		body.ToolChoice = &toolChoice{Type: "tool", Name: req.Schema.Name}
+	}
+	for _, m := range req.Messages {
+		body.Messages = append(body.Messages, message{Role: string(m.Role), Content: m.Content})
+	}
+	payload, err := json.Marshal(body)
+	if err != nil {
+		return llm.Response{}, fmt.Errorf("anthropic: generate: encode request: %w", err)
+	}
+
+	if req.Timeout > 0 {
+		var cancel context.CancelFunc
+		ctx, cancel = context.WithTimeout(ctx, req.Timeout)
+		defer cancel()
+	}
+	raw, err := p.do(ctx, http.MethodPost, "/v1/messages", payload)
+	if err != nil {
+		return llm.Response{}, fmt.Errorf("anthropic: generate: %w", err)
+	}
+
+	var mr messagesResponse
+	if err := json.Unmarshal(raw, &mr); err != nil {
+		return llm.Response{}, fmt.Errorf("anthropic: generate: decode response: %w", err)
+	}
+	if mr.Type != "message" {
+		return llm.Response{}, errors.New("anthropic: generate: response is not a message")
+	}
+	resp := llm.Response{
+		Usage:        llm.Usage{InputTokens: mr.Usage.InputTokens, OutputTokens: mr.Usage.OutputTokens},
+		Model:        mr.Model,
+		FinishReason: mr.StopReason,
+	}
+	var text strings.Builder
+	for _, block := range mr.Content {
+		switch block.Type {
+		case "text":
+			text.WriteString(block.Text)
+		case "tool_use":
+			if req.Schema != nil && block.Name == req.Schema.Name && resp.JSON == nil {
+				resp.JSON = block.Input
+			}
+		}
+	}
+	resp.Text = text.String()
+	if req.Schema == nil {
+		return resp, nil
+	}
+	if !isJSONObject(resp.JSON) {
+		resp.JSON = nil
+		return resp, fmt.Errorf("anthropic: generate: reply holds no input for the forced tool: %w", llm.ErrBadOutput)
+	}
+	return resp, nil
+}
+
+// isJSONObject reports whether raw is exactly one JSON object.
+func isJSONObject(raw json.RawMessage) bool {
+	s := bytes.TrimSpace(raw)
+	return bytes.HasPrefix(s, []byte("{")) && json.Valid(s)
+}
+
+type modelsResponse struct {
+	Data []struct {
+		ID          string `json:"id"`
+		DisplayName string `json:"display_name"`
+	} `json:"data"`
+	HasMore bool   `json:"has_more"`
+	LastID  string `json:"last_id"`
+}
+
+// modelsPageLimit is the largest page GET /v1/models serves.
+const modelsPageLimit = 1000
+
+// ListModels returns every model {base}/v1/models lists, following pages.
+func (p *Provider) ListModels(ctx context.Context) ([]llm.Model, error) {
+	models, err := p.listModels(ctx)
+	return models, redact(err, p.apiKey)
+}
+
+func (p *Provider) listModels(ctx context.Context) ([]llm.Model, error) {
+	models := []llm.Model{}
+	after := ""
+	for {
+		page, err := p.modelsPage(ctx, modelsPageLimit, after)
+		if err != nil {
+			return nil, fmt.Errorf("anthropic: list models: %w", err)
+		}
+		for _, m := range page.Data {
+			if m.ID == "" {
+				return nil, fmt.Errorf("anthropic: list models: model %d has no id", len(models))
+			}
+			name := m.DisplayName
+			if name == "" {
+				name = m.ID
+			}
+			models = append(models, llm.Model{ID: m.ID, DisplayName: name})
+		}
+		if !page.HasMore {
+			return models, nil
+		}
+		if page.LastID == "" || page.LastID == after {
+			return nil, errors.New("anthropic: list models: response has more pages but no new cursor")
+		}
+		after = page.LastID
+	}
+}
+
+// modelsPage fetches one page of GET {base}/v1/models.
+func (p *Provider) modelsPage(ctx context.Context, limit int, after string) (modelsResponse, error) {
+	q := url.Values{"limit": {strconv.Itoa(limit)}}
+	if after != "" {
+		q.Set("after_id", after)
+	}
+	raw, err := p.do(ctx, http.MethodGet, "/v1/models?"+q.Encode(), nil)
+	if err != nil {
+		return modelsResponse{}, err
+	}
+	var mr modelsResponse
+	if err := json.Unmarshal(raw, &mr); err != nil {
+		return modelsResponse{}, fmt.Errorf("decode response: %w", err)
+	}
+	if mr.Data == nil {
+		return modelsResponse{}, errors.New("response has no data list")
+	}
+	return mr, nil
+}
+
+// Verify checks the credentials with the cheapest authenticated call: one
+// page of GET {base}/v1/models holding at most one model.
+func (p *Provider) Verify(ctx context.Context) error {
+	_, err := p.modelsPage(ctx, 1, "")
+	if err != nil {
+		err = fmt.Errorf("anthropic: verify: %w", err)
+	}
+	return redact(err, p.apiKey)
+}
+
+// do sends one request and returns the body of a 2xx response. Any other
+// status becomes the matching llm typed error.
+func (p *Provider) do(ctx context.Context, method, path string, payload []byte) ([]byte, error) {
+	var reqBody io.Reader
+	if payload != nil {
+		reqBody = bytes.NewReader(payload)
+	}
+	httpReq, err := http.NewRequestWithContext(ctx, method, p.base+path, reqBody)
+	if err != nil {
+		// The parse error names the URL, whose path may hold the API key.
+		return nil, errors.New("build request: request URL is invalid")
+	}
+	httpReq.Header.Set("x-api-key", p.apiKey)
+	httpReq.Header.Set("anthropic-version", APIVersion)
+	httpReq.Header.Set("Accept", "application/json")
+	if payload != nil {
+		httpReq.Header.Set("Content-Type", "application/json")
+	}
+
+	httpResp, err := p.client.Do(httpReq)
+	if err != nil {
+		return nil, p.transportError(err)
+	}
+	defer httpResp.Body.Close()
+
+	if httpResp.StatusCode < 200 || httpResp.StatusCode > 299 {
+		body, err := io.ReadAll(io.LimitReader(httpResp.Body, maxErrorBody))
+		if err != nil {
+			return nil, p.transportError(err)
+		}
+		return nil, p.statusError(httpResp, body)
+	}
+	body, err := io.ReadAll(io.LimitReader(httpResp.Body, maxResponseBody+1))
+	if err != nil {
+		return nil, p.transportError(err)
+	}
+	if len(body) > maxResponseBody {
+		return nil, fmt.Errorf("response body exceeds %d bytes", maxResponseBody)
+	}
+	return body, nil
+}
+
+// statusOverloaded is the status the Messages API returns when it is
+// temporarily overloaded.
+const statusOverloaded = 529
+
+// statusError maps a non-2xx response to an llm typed error.
+func (p *Provider) statusError(resp *http.Response, body []byte) error {
+	switch resp.StatusCode {
+	case http.StatusUnauthorized, http.StatusForbidden:
+		return fmt.Errorf("HTTP %d: %w", resp.StatusCode, llm.ErrAuth)
+	case http.StatusTooManyRequests, statusOverloaded:
+		return llm.NewRateLimitedError(retryAfter(resp.Header.Get("Retry-After"), time.Now()), p.apiKey)
+	case http.StatusRequestTimeout:
+		return fmt.Errorf("HTTP %d: %w", resp.StatusCode, llm.ErrTimeout)
+	default:
+		return llm.NewProviderError(resp.StatusCode, body, p.apiKey)
+	}
+}
+
+// retryAfter parses a Retry-After header, in delay-seconds or HTTP-date
+// form. A missing, malformed or past value means the vendor gave no usable
+// wait, reported as 0.
+func retryAfter(value string, now time.Time) time.Duration {
+	value = strings.TrimSpace(value)
+	if value == "" {
+		return 0
+	}
+	if secs, err := strconv.ParseInt(value, 10, 64); err == nil || errors.Is(err, strconv.ErrRange) {
+		if secs < 0 {
+			return 0
+		}
+		// time.Duration counts nanoseconds in an int64; a larger wait is
+		// capped to the most whole seconds it holds instead of overflowing.
+		if secs > maxRetryAfterSeconds {
+			secs = maxRetryAfterSeconds
+		}
+		return time.Duration(secs) * time.Second
+	}
+	if at, err := http.ParseTime(value); err == nil && at.After(now) {
+		return at.Sub(now).Round(time.Second)
+	}
+	return 0
+}
+
+// maxRetryAfterSeconds is the largest delay-seconds value retryAfter
+// returns unchanged: the most whole seconds a time.Duration holds.
+const maxRetryAfterSeconds = math.MaxInt64 / int64(time.Second)
+
+// noRedirectClient returns an HTTP client that never follows a redirect.
+// A followed redirect would resend the credential headers, which net/http
+// strips only for its own list of sensitive headers and only across hosts;
+// instead the 3xx response is returned and becomes a provider error.
+func noRedirectClient() *http.Client {
+	return &http.Client{
+		CheckRedirect: func(*http.Request, []*http.Request) error {
+			return http.ErrUseLastResponse
+		},
+	}
+}
+
+func isTimeout(err error) bool {
+	var ne net.Error
+	return errors.Is(err, context.DeadlineExceeded) || (errors.As(err, &ne) && ne.Timeout())
+}
+
+// transportFailure is a failed HTTP exchange. It carries the cause's text
+// with the request URL removed and the API key redacted, and unwraps only to
+// the cause's category: llm.ErrTimeout, context.Canceled or nothing.
+type transportFailure struct {
+	text string
+	kind error
+}
+
+func (e *transportFailure) Error() string { return e.text }
+
+// GoString keeps %#v to the redacted Error text instead of the fields.
+func (e *transportFailure) GoString() string { return e.text }
+
+func (e *transportFailure) Unwrap() error { return e.kind }
+
+// transportError reports a failure to complete the HTTP exchange. A
+// *url.Error names the request URL, and a base URL path may hold the API
+// key, so only the wrapped cause is kept, rendered with the key redacted.
+func (p *Provider) transportError(err error) error {
+	var kind error
+	switch {
+	case isTimeout(err):
+		kind = llm.ErrTimeout
+	case errors.Is(err, context.Canceled):
+		kind = context.Canceled
+	}
+	var ue *url.Error
+	if errors.As(err, &ue) {
+		err = ue.Err
+	}
+	text := "transport: " + err.Error()
+	if kind == llm.ErrTimeout {
+		text = fmt.Sprintf("%s: %s", llm.ErrTimeout, text)
+	}
+	return &transportFailure{text: llm.Redact(text, p.apiKey), kind: kind}
+}
+
+// redactedError stands in for one layer of an error chain that holds the
+// API key. Its text is the layer's text with the key redacted, and Unwrap
+// returns the layer's causes passed through redact, so no error reached by
+// unwrapping has text holding the key. Is consults the original layer and
+// its chain, so sentinels still match. As does too. The llm typed errors
+// remove the key from their own complete text, fixed words included, so
+// they always match; As refuses a match whose text, or whose %#v form,
+// holds the key, so it never hands back an error that can print it.
+type redactedError struct {
+	text string
+	err  error
+	key  string
+}
+
+func (e *redactedError) Error() string { return e.text }
+
+// GoString keeps %#v from printing the fields, which hold the key.
+func (e *redactedError) GoString() string { return e.text }
+
+func (e *redactedError) Unwrap() error { return redact(errors.Unwrap(e.err), e.key) }
+
+func (e *redactedError) Is(target error) bool { return errors.Is(e.err, target) }
+
+func (e *redactedError) As(target any) bool {
+	if !errors.As(e.err, target) {
+		return false
+	}
+	found := reflect.ValueOf(target).Elem()
+	matched, isErr := found.Interface().(error)
+	if (isErr && holdsKey(matched, e.key)) || strings.Contains(fmt.Sprintf("%#v", found.Interface()), e.key) {
+		found.SetZero()
+		return false
+	}
+	return true
+}
+
+// redactedJoin is redactedError for a layer with several causes, such as
+// one built by errors.Join or by fmt.Errorf with more than one %w.
+type redactedJoin struct {
+	redactedError
+}
+
+func (e *redactedJoin) Unwrap() []error {
+	causes := e.err.(interface{ Unwrap() []error }).Unwrap()
+	safe := make([]error, len(causes))
+	for i, c := range causes {
+		safe[i] = redact(c, e.key)
+	}
+	return safe
+}
+
+// redact is the backstop every exported method applies to its error: with
+// a non-empty key, it returns a stand-in whose text, and the text of every
+// error it unwraps to, has the key redacted. Every non-nil err is wrapped,
+// even one whose text lacks the key, because %#v of an unwrapped error
+// prints its struct field names, and a key may spell one.
+func redact(err error, key string) error {
+	if err == nil || key == "" {
+		return err
+	}
+	re := redactedError{text: llm.Redact(err.Error(), key), err: err, key: key}
+	if _, ok := err.(interface{ Unwrap() []error }); ok {
+		return &redactedJoin{re}
+	}
+	return &re
+}
+
+// holdsKey reports whether the text of err or of any error in its chain
+// contains key.
+func holdsKey(err error, key string) bool {
+	if err == nil {
+		return false
+	}
+	if strings.Contains(err.Error(), key) {
+		return true
+	}
+	switch u := err.(type) {
+	case interface{ Unwrap() error }:
+		return holdsKey(u.Unwrap(), key)
+	case interface{ Unwrap() []error }:
+		for _, c := range u.Unwrap() {
+			if holdsKey(c, key) {
+				return true
+			}
+		}
+	}
+	return false
+}

internal/ai/llm/anthropic/testdata/README.md

@@ -0,0 +1,41 @@
+# Anthropic adapter fixtures
+
+These are the Messages API response bodies the contract tests in
+`anthropic_test.go` replay. They are **not live captures**. Product AI is
+tested with fakes, and live vendor calls are opt-in and never use
+credentials, so no request was sent to Anthropic to make them. Each fixture
+is a sanitized adaptation of the response shapes in Anthropic's public API
+documentation:
+
+- Messages: <https://docs.anthropic.com/en/api/messages>
+- Tool use, including `tool_choice` `{type: tool}`:
+  <https://docs.anthropic.com/en/docs/build-with-claude/tool-use>
+- List models: <https://docs.anthropic.com/en/api/models-list>
+- Errors: <https://docs.anthropic.com/en/api/errors>
+
+Sanitizing:
+
+- IDs, request IDs, timestamps and token counts are illustrative values in
+  the documented format, not values from a real account.
+- Message content and tool input are replaced with MealQuest dinner text.
+- No real credential appears anywhere. `{{KEY}}` is a placeholder the tests
+  replace with a fake key, to prove the adapter redacts a key echoed back in
+  a vendor body.
+
+Below, *not in the public example* marks fields or values that were added
+for a test case and do not come from the documented example.
+
+| Fixture | Shape | Not in the public example |
+| --- | --- | --- |
+| `messages_tool_use.json` | Message with one `tool_use` block, `stop_reason: tool_use`, `usage` with cache fields. | The tool name and input. |
+| `messages_text.json` | Message with `text` blocks, `stop_reason: end_turn`. | A second text block, to test joining. |
+| `messages_max_tokens.json` | Message with a `text` block, `stop_reason: max_tokens`. | — |
+| `models_page1.json` | Models list page: `data`, `has_more: true`, `first_id`, `last_id`. | — |
+| `models_page2.json` | Last models list page, `has_more: false`. | The second model has no `display_name`, to test the fallback to `id`. |
+| `error_authentication.json` | Error, `authentication_error` (401). | The `{{KEY}}` text; added to test redaction. |
+| `error_permission.json` | Error, `permission_error` (403). | — |
+| `error_rate_limit.json` | Error, `rate_limit_error` (429). | The `{{KEY}}` text; added to test redaction. |
+| `error_overloaded.json` | Error, `overloaded_error` (529). | — |
+| `error_not_found.json` | Error, `not_found_error` (404). | — |
+| `error_invalid_request.json` | Error, `invalid_request_error` (400). | — |
+| `error_api.json` | Error, `api_error` (500). | The `x-api-key: {{KEY}}` text; added to test redaction. |

internal/ai/llm/anthropic/testdata/error_api.json

@@ -0,0 +1 @@
+{"type": "error", "error": {"type": "api_error", "message": "An unexpected error has occurred internal to Anthropic's systems. x-api-key: {{KEY}}"}, "request_id": "req_011CSHoEeqs5C35K2UUqR7G4"}

internal/ai/llm/anthropic/testdata/error_authentication.json

@@ -0,0 +1 @@
+{"type": "error", "error": {"type": "authentication_error", "message": "invalid x-api-key: {{KEY}}"}, "request_id": "req_011CSHoEeqs5C35K2UUqR7Fy"}

internal/ai/llm/anthropic/testdata/error_invalid_request.json

@@ -0,0 +1 @@
+{"type": "error", "error": {"type": "invalid_request_error", "message": "max_tokens: Field required"}, "request_id": "req_011CSHoEeqs5C35K2UUqR7G3"}

internal/ai/llm/anthropic/testdata/error_not_found.json

@@ -0,0 +1 @@
+{"type": "error", "error": {"type": "not_found_error", "message": "model: claude-nonexistent"}, "request_id": "req_011CSHoEeqs5C35K2UUqR7G2"}

internal/ai/llm/anthropic/testdata/error_overloaded.json

@@ -0,0 +1 @@
+{"type": "error", "error": {"type": "overloaded_error", "message": "Overloaded"}, "request_id": "req_011CSHoEeqs5C35K2UUqR7G1"}

internal/ai/llm/anthropic/testdata/error_permission.json

@@ -0,0 +1 @@
+{"type": "error", "error": {"type": "permission_error", "message": "Your API key does not have permission to use the specified resource."}, "request_id": "req_011CSHoEeqs5C35K2UUqR7Fz"}

internal/ai/llm/anthropic/testdata/error_rate_limit.json

@@ -0,0 +1 @@
+{"type": "error", "error": {"type": "rate_limit_error", "message": "Number of request tokens has exceeded your per-minute rate limit for key {{KEY}}"}, "request_id": "req_011CSHoEeqs5C35K2UUqR7G0"}

internal/ai/llm/anthropic/testdata/messages_max_tokens.json

@@ -0,0 +1,12 @@
+{
+  "id": "msg_01XFDUDYJgAACzvnptvVoYEL",
+  "type": "message",
+  "role": "assistant",
+  "model": "claude-sonnet-5",
+  "content": [
+    {"type": "text", "text": "Here are some Side quests for Our kitchen"}
+  ],
+  "stop_reason": "max_tokens",
+  "stop_sequence": null,
+  "usage": {"input_tokens": 472, "output_tokens": 400}
+}

internal/ai/llm/anthropic/testdata/messages_text.json

@@ -0,0 +1,18 @@
+{
+  "id": "msg_013Zva2CMHLNnXjNJJKqJ2EF",
+  "type": "message",
+  "role": "assistant",
+  "model": "claude-sonnet-5",
+  "content": [
+    {"type": "text", "text": "Try a crock pot chili: "},
+    {"type": "text", "text": "it is a Quick dinner."}
+  ],
+  "stop_reason": "end_turn",
+  "stop_sequence": null,
+  "usage": {
+    "input_tokens": 2095,
+    "cache_creation_input_tokens": 0,
+    "cache_read_input_tokens": 0,
+    "output_tokens": 503
+  }
+}

internal/ai/llm/anthropic/testdata/messages_tool_use.json

@@ -0,0 +1,22 @@
+{
+  "id": "msg_01Aq9w938a90dw8q",
+  "type": "message",
+  "role": "assistant",
+  "model": "claude-sonnet-5",
+  "content": [
+    {
+      "type": "tool_use",
+      "id": "toolu_01A09q90qw90lq917835lq9",
+      "name": "side_quests",
+      "input": {"dinners": [{"name": "Sheet-pan gnocchi", "why": "Like your Regular tray bake, but quicker."}]}
+    }
+  ],
+  "stop_reason": "tool_use",
+  "stop_sequence": null,
+  "usage": {
+    "input_tokens": 472,
+    "cache_creation_input_tokens": 0,
+    "cache_read_input_tokens": 0,
+    "output_tokens": 61
+  }
+}

internal/ai/llm/anthropic/testdata/models_page1.json

@@ -0,0 +1,13 @@
+{
+  "data": [
+    {
+      "type": "model",
+      "id": "claude-sonnet-5",
+      "display_name": "Claude Sonnet 5",
+      "created_at": "2026-02-24T00:00:00Z"
+    }
+  ],
+  "has_more": true,
+  "first_id": "claude-sonnet-5",
+  "last_id": "claude-sonnet-5"
+}

internal/ai/llm/anthropic/testdata/models_page2.json

@@ -0,0 +1,18 @@
+{
+  "data": [
+    {
+      "type": "model",
+      "id": "claude-haiku-4-5-20251001",
+      "display_name": "Claude Haiku 4.5",
+      "created_at": "2025-10-01T00:00:00Z"
+    },
+    {
+      "type": "model",
+      "id": "claude-opus-5-5",
+      "created_at": "2026-05-01T00:00:00Z"
+    }
+  ],
+  "has_more": false,
+  "first_id": "claude-haiku-4-5-20251001",
+  "last_id": "claude-opus-5-5"
+}

internal/ai/llm/errors.go

@@ -0,0 +1,139 @@
+package llm
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+	"unicode/utf8"
+)
+
+var (
+	// ErrAuth means the vendor rejected the credentials.
+	ErrAuth = errors.New("llm: authentication failed")
+	// ErrRateLimited means the vendor throttled the request. The concrete
+	// error is a *RateLimitedError carrying the requested wait.
+	ErrRateLimited = errors.New("llm: rate limited")
+	// ErrTimeout means the request did not finish within its timeout.
+	ErrTimeout = errors.New("llm: request timed out")
+	// ErrBadOutput means the model replied but the reply is unusable, e.g.
+	// structured output that does not parse.
+	ErrBadOutput = errors.New("llm: unusable model output")
+	// ErrProvider means the vendor returned an unexpected HTTP status. The
+	// concrete error is a *ProviderError carrying the status and a redacted
+	// body excerpt.
+	ErrProvider = errors.New("llm: provider error")
+)
+
+// RateLimitedError is a throttled request. It matches ErrRateLimited.
+// Adapters build it with NewRateLimitedError so its text never holds their
+// credential.
+type RateLimitedError struct {
+	// RetryAfter is how long the vendor asked callers to wait; 0 means it
+	// did not say.
+	RetryAfter time.Duration
+	// text is the redacted Error text set by NewRateLimitedError; "" means
+	// the error was built without a credential.
+	text string
+}
+
+// NewRateLimitedError returns the error for a throttled request. secret is
+// the credential sent with the request, or "" when the request sent none.
+// Every occurrence of a non-empty secret is removed from the error text
+// when it is built, even where the fixed text happens to spell it, and the
+// secret itself is not kept.
+func NewRateLimitedError(retryAfter time.Duration, secret string) *RateLimitedError {
+	e := &RateLimitedError{RetryAfter: retryAfter}
+	e.text = Redact(e.Error(), secret)
+	return e
+}
+
+func (e *RateLimitedError) Error() string {
+	if e.text != "" {
+		return e.text
+	}
+	if e.RetryAfter == 0 {
+		return ErrRateLimited.Error()
+	}
+	return fmt.Sprintf("%s: retry after %v", ErrRateLimited, e.RetryAfter)
+}
+
+// GoString keeps %#v to the redacted Error text instead of the fields.
+func (e *RateLimitedError) GoString() string { return e.Error() }
+
+// Is reports whether target is ErrRateLimited.
+func (e *RateLimitedError) Is(target error) bool { return target == ErrRateLimited }
+
+// MaxBodyExcerpt is the longest response-body excerpt, in bytes, a
+// ProviderError keeps.
+const MaxBodyExcerpt = 512
+
+// redactionMarker replaces each secret in redacted text, unless the marker
+// would itself hold the secret.
+const redactionMarker = "[REDACTED]"
+
+// Redact returns s with every occurrence of a non-empty secret removed. Each
+// occurrence becomes "[REDACTED]" when the result then holds no secret;
+// otherwise, because the marker contains the secret or joins with its
+// neighbours to form it, occurrences are deleted until none remains. The
+// result never contains secret.
+func Redact(s, secret string) string {
+	if secret == "" {
+		return s
+	}
+	if out := strings.ReplaceAll(s, secret, redactionMarker); !strings.Contains(out, secret) {
+		return out
+	}
+	for strings.Contains(s, secret) {
+		s = strings.ReplaceAll(s, secret, "")
+	}
+	return s
+}
+
+// ProviderError is an unexpected HTTP status from the vendor. It matches
+// ErrProvider. Build it with NewProviderError, which redacts the body.
+type ProviderError struct {
+	status int
+	body   string
+	text   string
+}
+
+// NewProviderError returns the error for an unexpected HTTP status. It
+// always keeps a body excerpt of at most MaxBodyExcerpt bytes. secret is the
+// credential sent with the request, or "" when the request sent none; every
+// occurrence of a non-empty secret in body is removed by Redact before the
+// body is cut, so no part of it survives, and again after the cut, so the
+// truncation mark cannot complete it. It is removed from the complete error
+// text too, even where the fixed text happens to spell it, and the secret
+// itself is not kept.
+func NewProviderError(status int, body []byte, secret string) *ProviderError {
+	s := strings.TrimSpace(Redact(string(body), secret))
+	if len(s) > MaxBodyExcerpt {
+		cut := MaxBodyExcerpt
+		for cut > 0 && !utf8.RuneStart(s[cut]) {
+			cut--
+		}
+		s = Redact(s[:cut]+"…", secret)
+	}
+	text := fmt.Sprintf("%s: HTTP %d", ErrProvider, status)
+	if s != "" {
+		text += ": " + s
+	}
+	return &ProviderError{status: status, body: s, text: Redact(text, secret)}
+}
+
+// Status returns the HTTP status code.
+func (e *ProviderError) Status() int { return e.status }
+
+// Body returns the redacted, truncated response-body excerpt; it is empty
+// when the vendor sent no body.
+func (e *ProviderError) Body() string { return e.body }
+
+func (e *ProviderError) Error() string { return e.text }
+
+// GoString keeps %#v to the redacted Error text instead of the fields,
+// whose names could spell the credential.
+func (e *ProviderError) GoString() string { return e.text }
+
+// Is reports whether target is ErrProvider.
+func (e *ProviderError) Is(target error) bool { return target == ErrProvider }

internal/ai/llm/errors_test.go

@@ -0,0 +1,198 @@
+package llm
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestSentinelErrorsMatchWhenWrapped(t *testing.T) {
+	for _, sentinel := range []error{ErrAuth, ErrTimeout, ErrBadOutput} {
+		wrapped := fmt.Errorf("openai: generate: %w", sentinel)
+		if !errors.Is(wrapped, sentinel) {
+			t.Errorf("errors.Is(%v, %v) = false", wrapped, sentinel)
+		}
+		for _, other := range []error{ErrAuth, ErrTimeout, ErrBadOutput, ErrRateLimited, ErrProvider} {
+			if other != sentinel && errors.Is(wrapped, other) {
+				t.Errorf("errors.Is(%v, %v) = true", wrapped, other)
+			}
+		}
+	}
+}
+
+func TestRateLimitedError(t *testing.T) {
+	err := fmt.Errorf("anthropic: %w", &RateLimitedError{RetryAfter: 30 * time.Second})
+	if !errors.Is(err, ErrRateLimited) {
+		t.Fatal("errors.Is(err, ErrRateLimited) = false")
+	}
+	if errors.Is(err, ErrProvider) || errors.Is(err, ErrAuth) {
+		t.Fatal("rate-limited error matches an unrelated sentinel")
+	}
+	var rl *RateLimitedError
+	if !errors.As(err, &rl) {
+		t.Fatal("errors.As(err, *RateLimitedError) = false")
+	}
+	if rl.RetryAfter != 30*time.Second {
+		t.Fatalf("RetryAfter = %v, want 30s", rl.RetryAfter)
+	}
+	if got := err.Error(); got != "anthropic: llm: rate limited: retry after 30s" {
+		t.Fatalf("Error() = %q", got)
+	}
+	if got := (&RateLimitedError{}).Error(); got != "llm: rate limited" {
+		t.Fatalf("Error() without RetryAfter = %q", got)
+	}
+}
+
+func TestProviderError(t *testing.T) {
+	err := fmt.Errorf("gemini: %w", NewProviderError(503, []byte(` {"error":"overloaded"} `), "sk-test"))
+	if !errors.Is(err, ErrProvider) {
+		t.Fatal("errors.Is(err, ErrProvider) = false")
+	}
+	if errors.Is(err, ErrRateLimited) || errors.Is(err, ErrAuth) {
+		t.Fatal("provider error matches an unrelated sentinel")
+	}
+	var pe *ProviderError
+	if !errors.As(err, &pe) {
+		t.Fatal("errors.As(err, *ProviderError) = false")
+	}
+	if pe.Status() != 503 || pe.Body() != `{"error":"overloaded"}` {
+		t.Fatalf("Status, Body = %d, %q", pe.Status(), pe.Body())
+	}
+	if got := err.Error(); got != `gemini: llm: provider error: HTTP 503: {"error":"overloaded"}` {
+		t.Fatalf("Error() = %q", got)
+	}
+	if got := NewProviderError(500, nil, "sk-test").Error(); got != "llm: provider error: HTTP 500" {
+		t.Fatalf("Error() without body = %q", got)
+	}
+}
+
+func TestProviderErrorRedactsSecrets(t *testing.T) {
+	const key = "sk-live-0123456789abcdef"
+	body := []byte(`{"error":"invalid key sk-live-0123456789abcdef","echo":"Bearer sk-live-0123456789abcdef"}`)
+	pe := NewProviderError(400, body, key)
+	for _, s := range []string{pe.Error(), pe.Body()} {
+		if strings.Contains(s, key) {
+			t.Fatalf("secret leaked: %q", s)
+		}
+	}
+	want := `{"error":"invalid key [REDACTED]","echo":"Bearer [REDACTED]"}`
+	if pe.Body() != want {
+		t.Fatalf("Body() = %q, want %q", pe.Body(), want)
+	}
+}
+
+func TestProviderErrorRedactsBeforeTruncating(t *testing.T) {
+	const key = "sk-secret-straddling-the-cut"
+	// The key starts just before the excerpt limit, so truncating first
+	// would leave its prefix in the excerpt.
+	body := strings.Repeat("x", MaxBodyExcerpt-5) + key
+	pe := NewProviderError(500, []byte(body), key)
+	if strings.Contains(pe.Body(), "sk-se") {
+		t.Fatalf("secret prefix leaked: %q", pe.Body())
+	}
+}
+
+func TestProviderErrorTruncatesOnRuneBoundary(t *testing.T) {
+	body := strings.Repeat("a", MaxBodyExcerpt-1) + "é" + strings.Repeat("b", 100)
+	pe := NewProviderError(500, []byte(body), "sk-test")
+	want := strings.Repeat("a", MaxBodyExcerpt-1) + "…"
+	if pe.Body() != want {
+		t.Fatalf("Body() has %d bytes, want %d", len(pe.Body()), len(want))
+	}
+}
+
+func TestProviderErrorKeepsBoundedBodyWithoutSecret(t *testing.T) {
+	body := []byte(` {"error":"model \"llama9\" not found"} `)
+	pe := NewProviderError(404, body, "")
+	if pe.Body() != `{"error":"model \"llama9\" not found"}` {
+		t.Fatalf("Body() = %q", pe.Body())
+	}
+	if got := pe.Error(); got != `llm: provider error: HTTP 404: {"error":"model \"llama9\" not found"}` {
+		t.Fatalf("Error() = %q", got)
+	}
+	long := NewProviderError(500, []byte(strings.Repeat("x", 4*MaxBodyExcerpt)), "")
+	if want := strings.Repeat("x", MaxBodyExcerpt) + "…"; long.Body() != want {
+		t.Fatalf("Body() has %d bytes, want %d", len(long.Body()), len(want))
+	}
+}
+
+func TestRedactNeverLeavesSecret(t *testing.T) {
+	cases := []struct{ s, secret, want string }{
+		{"key sk-1 and Bearer sk-1", "sk-1", "key [REDACTED] and Bearer [REDACTED]"},
+		{"no secret here", "sk-1", "no secret here"},
+		{"x", "", "x"},
+		// The marker holds the secret, so occurrences are deleted.
+		{"rejected REDACTED", "REDACTED", "rejected "},
+		{"A then A", "A", " then "},
+		// The marker joins with a neighbour to form the secret.
+		{"]]aa", "]a", ""},
+		// The marker holds the secret and deleting once leaves a new one.
+		{"DDAA", "DA", ""},
+		{"aabb", "ab", "a[REDACTED]b"},
+	}
+	for _, c := range cases {
+		if got := Redact(c.s, c.secret); got != c.want {
+			t.Errorf("Redact(%q, %q) = %q, want %q", c.s, c.secret, got, c.want)
+		}
+	}
+}
+
+func TestProviderErrorWithMarkerSecretNeverLeaksSecret(t *testing.T) {
+	const key = "REDACTED"
+	pe := NewProviderError(500, []byte(`{"error":"bad key REDACTED","echo":"Bearer REDACTED"}`), key)
+	for _, s := range []string{pe.Error(), pe.Body()} {
+		if strings.Contains(s, key) {
+			t.Fatalf("secret leaked: %q", s)
+		}
+	}
+	if want := `{"error":"bad key ","echo":"Bearer "}`; pe.Body() != want {
+		t.Fatalf("Body() = %q, want %q", pe.Body(), want)
+	}
+}
+
+func TestProviderErrorTruncationMarkCannotCompleteSecret(t *testing.T) {
+	const key = "z…"
+	body := strings.Repeat("a", MaxBodyExcerpt-1) + "z" + strings.Repeat("b", 10)
+	if pe := NewProviderError(500, []byte(body), key); strings.Contains(pe.Body(), key) {
+		t.Fatalf("secret leaked: %q", pe.Body())
+	}
+}
+
+func TestProviderErrorWithFixedWordSecretNeverLeaksSecret(t *testing.T) {
+	const secret = "HTTP"
+	pe := NewProviderError(500, []byte(`{"error":"HTTP down"}`), secret)
+	if strings.Contains(pe.Error(), secret) || strings.Contains(pe.Body(), secret) {
+		t.Fatalf("secret leaked: Error %q, Body %q", pe.Error(), pe.Body())
+	}
+	if got := NewProviderError(500, nil, secret).Error(); got != "llm: provider error: [REDACTED] 500" {
+		t.Fatalf("Error() without body = %q", got)
+	}
+}
+
+func TestRateLimitedErrorWithFixedWordSecretNeverLeaksSecret(t *testing.T) {
+	for _, secret := range []string{"rate", "retry after"} {
+		for _, wait := range []time.Duration{0, 30 * time.Second} {
+			rl := NewRateLimitedError(wait, secret)
+			if strings.Contains(rl.Error(), secret) {
+				t.Fatalf("secret %q leaked: %q", secret, rl.Error())
+			}
+			if rl.RetryAfter != wait || !errors.Is(rl, ErrRateLimited) {
+				t.Fatalf("NewRateLimitedError(%v) = %+v", wait, rl)
+			}
+		}
+	}
+}
+
+func TestTypedErrorsDoNotKeepSecret(t *testing.T) {
+	const secret = "sk-live-0123456789abcdef"
+	for _, err := range []error{
+		NewProviderError(500, []byte("down "+secret), secret),
+		NewRateLimitedError(30*time.Second, secret),
+	} {
+		if got := fmt.Sprintf("%#v %+v", err, err); strings.Contains(got, secret) {
+			t.Fatalf("formatting %T leaks the secret: %q", err, got)
+		}
+	}
+}

internal/ai/llm/fake.go

@@ -0,0 +1,127 @@
+package llm
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"slices"
+	"sync"
+)
+
+// Fake is a scripted Provider for tests. Each method returns its queued
+// results in order, one per call, and records every Request Generate
+// receives. A call with nothing left in its queue fails, so an unexpected
+// call is never silently answered. It is safe for concurrent use.
+type Fake struct {
+	mu       sync.Mutex
+	generate []GenerateResult
+	models   []ListModelsResult
+	verify   []error
+	requests []Request
+}
+
+var _ Provider = (*Fake)(nil)
+
+// GenerateResult is one scripted Generate outcome.
+type GenerateResult struct {
+	Response Response
+	Err      error
+}
+
+// ListModelsResult is one scripted ListModels outcome.
+type ListModelsResult struct {
+	Models []Model
+	Err    error
+}
+
+// QueueGenerate appends results to the Generate script.
+func (f *Fake) QueueGenerate(results ...GenerateResult) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	f.generate = append(f.generate, results...)
+}
+
+// QueueListModels appends results to the ListModels script.
+func (f *Fake) QueueListModels(results ...ListModelsResult) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	f.models = append(f.models, results...)
+}
+
+// QueueVerify appends results to the Verify script; a nil entry is success.
+func (f *Fake) QueueVerify(results ...error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	f.verify = append(f.verify, results...)
+}
+
+// Generate records req and returns the next scripted result.
+func (f *Fake) Generate(_ context.Context, req Request) (Response, error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	f.requests = append(f.requests, cloneRequest(req))
+	if len(f.generate) == 0 {
+		return Response{}, fmt.Errorf("llm: fake: unscripted Generate call %d", len(f.requests))
+	}
+	r := f.generate[0]
+	f.generate = f.generate[1:]
+	return r.Response, r.Err
+}
+
+// ListModels returns the next scripted result.
+func (f *Fake) ListModels(context.Context) ([]Model, error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	if len(f.models) == 0 {
+		return nil, fmt.Errorf("llm: fake: unscripted ListModels call")
+	}
+	r := f.models[0]
+	f.models = f.models[1:]
+	return slices.Clone(r.Models), r.Err
+}
+
+// Verify returns the next scripted result.
+func (f *Fake) Verify(context.Context) error {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	if len(f.verify) == 0 {
+		return fmt.Errorf("llm: fake: unscripted Verify call")
+	}
+	err := f.verify[0]
+	f.verify = f.verify[1:]
+	return err
+}
+
+// Requests returns a copy of every Request Generate received, in order.
+func (f *Fake) Requests() []Request {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	out := make([]Request, len(f.requests))
+	for i, r := range f.requests {
+		out[i] = cloneRequest(r)
+	}
+	return out
+}
+
+// Remaining reports how many scripted results of each kind are unused, so a
+// test can assert its script was consumed.
+func (f *Fake) Remaining() (generate, listModels, verify int) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	return len(f.generate), len(f.models), len(f.verify)
+}
+
+// cloneRequest deep-copies r so a recorded Request is unaffected by later
+// changes the caller makes to its slices and pointers.
+func cloneRequest(r Request) Request {
+	r.Messages = slices.Clone(r.Messages)
+	if r.Temperature != nil {
+		t := *r.Temperature
+		r.Temperature = &t
+	}
+	if r.Schema != nil {
+		s := JSONSchema{Name: r.Schema.Name, Schema: json.RawMessage(slices.Clone([]byte(r.Schema.Schema)))}
+		r.Schema = &s
+	}
+	return r
+}

internal/ai/llm/fake_test.go

@@ -0,0 +1,138 @@
+package llm
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"sync"
+	"testing"
+	"time"
+)
+
+func TestFakeGenerateReturnsScriptInOrder(t *testing.T) {
+	ctx := context.Background()
+	var f Fake
+	f.QueueGenerate(
+		GenerateResult{Response: Response{Text: "first", Model: "m1"}},
+		GenerateResult{Err: &RateLimitedError{RetryAfter: time.Second}},
+	)
+	f.QueueGenerate(GenerateResult{Response: Response{JSON: json.RawMessage(`{"ok":true}`), FinishReason: "stop"}})
+
+	req := Request{Messages: []Message{{Role: RoleUser, Content: "one"}}}
+	resp, err := f.Generate(ctx, req)
+	if err != nil || resp.Text != "first" || resp.Model != "m1" {
+		t.Fatalf("call 1 = %+v, %v", resp, err)
+	}
+	if _, err := f.Generate(ctx, req); !errors.Is(err, ErrRateLimited) {
+		t.Fatalf("call 2 err = %v, want ErrRateLimited", err)
+	}
+	resp, err = f.Generate(ctx, req)
+	if err != nil || string(resp.JSON) != `{"ok":true}` || resp.FinishReason != "stop" {
+		t.Fatalf("call 3 = %+v, %v", resp, err)
+	}
+	if _, err := f.Generate(ctx, req); err == nil {
+		t.Fatal("unscripted call 4 succeeded")
+	}
+	if g, l, v := f.Remaining(); g != 0 || l != 0 || v != 0 {
+		t.Fatalf("Remaining() = %d, %d, %d", g, l, v)
+	}
+	if n := len(f.Requests()); n != 4 {
+		t.Fatalf("recorded %d requests, want 4 (unscripted calls are recorded too)", n)
+	}
+}
+
+func TestFakeRecordsRequests(t *testing.T) {
+	var f Fake
+	f.QueueGenerate(GenerateResult{}, GenerateResult{})
+	temp := 0.2
+	first := Request{
+		System:      "be brief",
+		Messages:    []Message{{Role: RoleUser, Content: "plan dinners"}},
+		Temperature: &temp,
+		MaxTokens:   100,
+		Schema:      &JSONSchema{Name: "plan", Schema: json.RawMessage(`{"type":"object"}`)},
+		Timeout:     5 * time.Second,
+	}
+	if _, err := f.Generate(context.Background(), first); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := f.Generate(context.Background(), Request{System: "second"}); err != nil {
+		t.Fatal(err)
+	}
+
+	// Later changes by the caller must not alter what was recorded.
+	first.Messages[0].Content = "changed"
+	temp = 1
+	first.Schema.Schema[2] = 'X'
+
+	got := f.Requests()
+	if len(got) != 2 || got[1].System != "second" {
+		t.Fatalf("Requests() = %+v", got)
+	}
+	r := got[0]
+	if r.System != "be brief" || r.Messages[0].Content != "plan dinners" || *r.Temperature != 0.2 ||
+		r.MaxTokens != 100 || r.Schema.Name != "plan" || string(r.Schema.Schema) != `{"type":"object"}` ||
+		r.Timeout != 5*time.Second {
+		t.Fatalf("recorded request = %+v", r)
+	}
+
+	// Changing a returned copy must not alter the record either.
+	got[0].Messages[0].Content = "mutated"
+	if f.Requests()[0].Messages[0].Content != "plan dinners" {
+		t.Fatal("Requests() returned shared state")
+	}
+}
+
+func TestFakeListModelsAndVerify(t *testing.T) {
+	ctx := context.Background()
+	var f Fake
+	f.QueueListModels(
+		ListModelsResult{Models: []Model{{ID: "a", DisplayName: "A"}, {ID: "b", DisplayName: "b"}}},
+		ListModelsResult{Err: ErrAuth},
+	)
+	f.QueueVerify(nil, fmt.Errorf("wrapped: %w", ErrAuth))
+
+	models, err := f.ListModels(ctx)
+	if err != nil || len(models) != 2 || models[0].ID != "a" {
+		t.Fatalf("ListModels 1 = %+v, %v", models, err)
+	}
+	if _, err := f.ListModels(ctx); !errors.Is(err, ErrAuth) {
+		t.Fatalf("ListModels 2 err = %v, want ErrAuth", err)
+	}
+	if _, err := f.ListModels(ctx); err == nil {
+		t.Fatal("unscripted ListModels succeeded")
+	}
+	if err := f.Verify(ctx); err != nil {
+		t.Fatalf("Verify 1 = %v", err)
+	}
+	if err := f.Verify(ctx); !errors.Is(err, ErrAuth) {
+		t.Fatalf("Verify 2 = %v, want ErrAuth", err)
+	}
+	if err := f.Verify(ctx); err == nil {
+		t.Fatal("unscripted Verify succeeded")
+	}
+}
+
+func TestFakeConcurrentUse(t *testing.T) {
+	const n = 50
+	var f Fake
+	for i := range n {
+		f.QueueGenerate(GenerateResult{Response: Response{Text: fmt.Sprint(i)}})
+	}
+	var wg sync.WaitGroup
+	for range n {
+		wg.Go(func() {
+			if _, err := f.Generate(context.Background(), Request{}); err != nil {
+				t.Error(err)
+			}
+		})
+	}
+	wg.Wait()
+	if len(f.Requests()) != n {
+		t.Fatalf("recorded %d requests, want %d", len(f.Requests()), n)
+	}
+	if g, _, _ := f.Remaining(); g != 0 {
+		t.Fatalf("%d Generate results unused", g)
+	}
+}

internal/ai/llm/llm.go

@@ -0,0 +1,133 @@
+// Package llm is the single interface MealQuest uses to talk to a language
+// model. Every vendor adapter implements Provider over plain net/http (no
+// vendor SDKs) and reports failures with this package's typed errors, so
+// callers decide what to do from errors.Is and errors.As alone.
+//
+// Errors from this package and its adapters never contain an API key.
+package llm
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"time"
+)
+
+// Provider is a language-model vendor.
+type Provider interface {
+	// Generate sends one request and returns the model's reply.
+	Generate(ctx context.Context, req Request) (Response, error)
+	// ListModels returns the models the configured credentials can use.
+	ListModels(ctx context.Context) ([]Model, error)
+	// Verify checks that the configured credentials are accepted.
+	Verify(ctx context.Context) error
+}
+
+// Role is the author of a Message.
+type Role string
+
+// The roles a Message may have. The system prompt is Request.System, not a
+// message.
+const (
+	RoleUser      Role = "user"
+	RoleAssistant Role = "assistant"
+)
+
+// Message is one turn of a conversation.
+type Message struct {
+	Role    Role
+	Content string
+}
+
+// JSONSchema is a named structured-output contract: when a Request carries
+// one, the model must reply with JSON matching Schema.
+type JSONSchema struct {
+	// Name identifies the contract to the vendor, e.g. "side_quests".
+	Name string
+	// Schema is a JSON Schema object.
+	Schema json.RawMessage
+}
+
+// Request is one generation request.
+type Request struct {
+	// System is the system prompt; empty means none.
+	System string
+	// Messages is the conversation, oldest first. It must not be empty.
+	Messages []Message
+	// Temperature is the sampling temperature; nil means the vendor default.
+	Temperature *float64
+	// MaxTokens caps the reply length; 0 means the vendor default.
+	MaxTokens int
+	// Schema, when set, requests structured output; the reply is then in
+	// Response.JSON.
+	Schema *JSONSchema
+	// Timeout bounds the request; 0 means only ctx bounds it.
+	Timeout time.Duration
+}
+
+// Validate reports whether r is well formed. Adapters call it before
+// contacting the vendor. Its errors never quote the request's text, such as
+// a role or schema name: any of it may equal the API key.
+func (r Request) Validate() error {
+	if len(r.Messages) == 0 {
+		return errors.New("llm: request has no messages")
+	}
+	for i, m := range r.Messages {
+		if m.Role != RoleUser && m.Role != RoleAssistant {
+			return fmt.Errorf("llm: message %d has an unknown role", i)
+		}
+	}
+	if r.Temperature != nil && *r.Temperature < 0 {
+		return fmt.Errorf("llm: temperature %v is negative", *r.Temperature)
+	}
+	if r.MaxTokens < 0 {
+		return fmt.Errorf("llm: max tokens %d is negative", r.MaxTokens)
+	}
+	if r.Timeout < 0 {
+		return fmt.Errorf("llm: timeout %v is negative", r.Timeout)
+	}
+	if r.Schema != nil {
+		if r.Schema.Name == "" {
+			return errors.New("llm: schema has no name")
+		}
+		var obj map[string]json.RawMessage
+		if err := json.Unmarshal(r.Schema.Schema, &obj); err != nil || obj == nil {
+			return errors.New("llm: schema is not a JSON object")
+		}
+	}
+	return nil
+}
+
+// Usage is the token count of one Generate call.
+type Usage struct {
+	InputTokens  int
+	OutputTokens int
+}
+
+// Total returns InputTokens + OutputTokens.
+func (u Usage) Total() int { return u.InputTokens + u.OutputTokens }
+
+// Response is the model's reply to a Request.
+type Response struct {
+	// Text is the reply text.
+	Text string
+	// JSON is the structured reply when the Request carried a Schema, and
+	// nil otherwise.
+	JSON json.RawMessage
+	// Usage is the tokens the call consumed.
+	Usage Usage
+	// Model is the model that answered, as the vendor reports it.
+	Model string
+	// FinishReason is why generation stopped, as the vendor reports it.
+	FinishReason string
+}
+
+// Model is a model a Provider offers.
+type Model struct {
+	// ID is the vendor's model identifier, used in requests.
+	ID string
+	// DisplayName is a human-readable name; it equals ID when the vendor
+	// gives none.
+	DisplayName string
+}

internal/ai/llm/llm_test.go

@@ -0,0 +1,44 @@
+package llm
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+func TestRequestValidate(t *testing.T) {
+	neg := -0.1
+	valid := func() Request {
+		return Request{
+			Messages: []Message{{Role: RoleUser, Content: "hi"}, {Role: RoleAssistant, Content: "hello"}},
+			Schema:   &JSONSchema{Name: "plan", Schema: json.RawMessage(`{"type":"object"}`)},
+		}
+	}
+	if err := valid().Validate(); err != nil {
+		t.Fatalf("valid request: %v", err)
+	}
+	cases := map[string]func(*Request){
+		"no messages":    func(r *Request) { r.Messages = nil },
+		"unknown role":   func(r *Request) { r.Messages[0].Role = "system" },
+		"negative temp":  func(r *Request) { r.Temperature = &neg },
+		"negative max":   func(r *Request) { r.MaxTokens = -1 },
+		"negative time":  func(r *Request) { r.Timeout = -1 },
+		"unnamed schema": func(r *Request) { r.Schema.Name = "" },
+		"schema array":   func(r *Request) { r.Schema.Schema = json.RawMessage(`[]`) },
+		"schema null":    func(r *Request) { r.Schema.Schema = json.RawMessage(`null`) },
+		"schema invalid": func(r *Request) { r.Schema.Schema = json.RawMessage(`{`) },
+		"schema empty":   func(r *Request) { r.Schema.Schema = nil },
+	}
+	for name, mutate := range cases {
+		r := valid()
+		mutate(&r)
+		if err := r.Validate(); err == nil {
+			t.Errorf("%s: Validate() = nil", name)
+		}
+	}
+}
+
+func TestUsageTotal(t *testing.T) {
+	if got := (Usage{InputTokens: 12, OutputTokens: 30}).Total(); got != 42 {
+		t.Fatalf("Total() = %d, want 42", got)
+	}
+}

internal/ai/llm/openai/openai.go

@@ -0,0 +1,628 @@
+// Package openai is the llm.Provider adapter for OpenAI-compatible chat
+// APIs: OpenAI itself, OpenRouter and Ollama's /v1 endpoint. It calls
+// POST {base}/chat/completions and GET {base}/models over plain net/http.
+//
+// The adapter never logs, and no error it returns contains the API key or
+// the Authorization header value: errors do not quote caller- or
+// vendor-supplied text, and every exported method passes its error through
+// redact as a backstop.
+package openai
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"math"
+	"net"
+	"net/http"
+	"net/textproto"
+	"net/url"
+	"reflect"
+	"strconv"
+	"strings"
+	"time"
+
+	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/ai/llm"
+)
+
+// StructuredOutput is how the adapter asks the vendor for JSON when a
+// Request carries a Schema. Which mode a vendor and model support comes
+// from its preset.
+type StructuredOutput string
+
+const (
+	// JSONSchema sends response_format {type: json_schema, strict: true}
+	// with the Request's schema.
+	JSONSchema StructuredOutput = "json_schema"
+	// JSONObject sends response_format {type: json_object} and puts the
+	// schema in the system prompt.
+	JSONObject StructuredOutput = "json_object"
+	// PromptOnly sends no response_format, puts the schema in the system
+	// prompt and takes the first JSON object found in the reply.
+	PromptOnly StructuredOutput = "prompt_only"
+)
+
+// Config configures a Provider.
+type Config struct {
+	// BaseURL is the API root the endpoint paths are appended to, e.g.
+	// "https://api.openai.com/v1", "https://openrouter.ai/api/v1" or
+	// "http://ollama:11434/v1".
+	BaseURL string
+	// APIKey is sent as "Authorization: Bearer <APIKey>". Empty sends no
+	// Authorization header, for endpoints such as Ollama that need none.
+	APIKey string
+	// Model is the model Generate requests. ListModels and Verify do not
+	// need it.
+	Model string
+	// Headers are extra request headers, e.g. OpenRouter's HTTP-Referer and
+	// X-Title. An Accept header replaces the default "application/json".
+	// Headers the adapter or net/http set themselves (see managedHeaders)
+	// are rejected.
+	Headers map[string]string
+	// StructuredOutput is how JSON is requested when a Request has a Schema.
+	StructuredOutput StructuredOutput
+}
+
+// Provider is an OpenAI-compatible llm.Provider.
+type Provider struct {
+	base    string
+	apiKey  string
+	model   string
+	headers http.Header
+	mode    StructuredOutput
+	client  *http.Client
+}
+
+var _ llm.Provider = (*Provider)(nil)
+
+// New validates cfg and returns a Provider.
+func New(cfg Config) (*Provider, error) {
+	p, err := newFromConfig(cfg)
+	if err != nil {
+		return nil, redact(err, cfg.APIKey)
+	}
+	return p, nil
+}
+
+func newFromConfig(cfg Config) (*Provider, error) {
+	// Base URL errors never echo the URL: a rejected one may carry a
+	// credential.
+	u, err := url.Parse(cfg.BaseURL)
+	if err != nil {
+		return nil, errors.New("openai: base URL does not parse")
+	}
+	if (u.Scheme != "http" && u.Scheme != "https") || u.Host == "" {
+		return nil, errors.New("openai: base URL must be an absolute http or https URL")
+	}
+	// A trailing "?" or "#" parses to an empty query or fragment, yet the
+	// endpoint path appended to it would land in the query or fragment.
+	if u.User != nil || strings.ContainsAny(cfg.BaseURL, "?#") {
+		return nil, errors.New("openai: base URL must not carry credentials, a query or a fragment")
+	}
+	// No error from New quotes caller-supplied text or a name derived from
+	// it: any such text may equal or contain the API key, and redaction
+	// cannot catch a fragment or a case-changed copy of it.
+	switch cfg.StructuredOutput {
+	case JSONSchema, JSONObject, PromptOnly:
+	default:
+		return nil, errors.New("openai: unknown structured output mode")
+	}
+	headers := make(http.Header, len(cfg.Headers)+1)
+	for name, value := range cfg.Headers {
+		if !validHeaderName(name) {
+			return nil, errors.New("openai: an extra header name is not a valid HTTP token")
+		}
+		canonical := textproto.CanonicalMIMEHeaderKey(name)
+		if managedHeaders[canonical] {
+			return nil, errors.New("openai: an extra header is set by the adapter")
+		}
+		if !validHeaderValue(value) {
+			return nil, errors.New("openai: an extra header value has a control character")
+		}
+		headers.Set(canonical, value)
+	}
+	if headers.Get("Accept") == "" {
+		headers.Set("Accept", "application/json")
+	}
+	return &Provider{
+		base:    strings.TrimRight(cfg.BaseURL, "/"),
+		apiKey:  cfg.APIKey,
+		model:   cfg.Model,
+		headers: headers,
+		mode:    cfg.StructuredOutput,
+		client:  noRedirectClient(),
+	}, nil
+}
+
+// managedHeaders are the request headers the adapter or net/http set; a
+// configured value for one would be overwritten or ignored.
+var managedHeaders = map[string]bool{
+	"Authorization":     true,
+	"Content-Type":      true,
+	"Content-Length":    true,
+	"Transfer-Encoding": true,
+	"Host":              true,
+	"Connection":        true,
+}
+
+// validHeaderName reports whether name is an RFC 9110 field-name: a
+// non-empty token of letters, digits and !#$%&'*+-.^_`|~.
+func validHeaderName(name string) bool {
+	if name == "" {
+		return false
+	}
+	for i := 0; i < len(name); i++ {
+		c := name[i]
+		switch {
+		case 'a' <= c && c <= 'z', 'A' <= c && c <= 'Z', '0' <= c && c <= '9':
+		case strings.IndexByte("!#$%&'*+-.^_`|~", c) >= 0:
+		default:
+			return false
+		}
+	}
+	return true
+}
+
+// validHeaderValue reports whether value is an RFC 9110 field-value: no
+// control characters other than horizontal tab, so no CR, LF or DEL.
+func validHeaderValue(value string) bool {
+	for i := 0; i < len(value); i++ {
+		if c := value[i]; (c < 0x20 && c != '\t') || c == 0x7f {
+			return false
+		}
+	}
+	return true
+}
+
+// maxResponseBody caps a successful response body; a larger one is an error.
+const maxResponseBody = 16 << 20
+
+// maxErrorBody caps how much of an error response body is read. It is far
+// above llm.MaxBodyExcerpt, so redaction still sees every secret that could
+// reach the excerpt.
+const maxErrorBody = 64 << 10
+
+type chatMessage struct {
+	Role    string `json:"role"`
+	Content string `json:"content"`
+}
+
+type jsonSchemaFormat struct {
+	Name   string          `json:"name"`
+	Schema json.RawMessage `json:"schema"`
+	Strict bool            `json:"strict"`
+}
+
+type responseFormat struct {
+	Type       string            `json:"type"`
+	JSONSchema *jsonSchemaFormat `json:"json_schema,omitempty"`
+}
+
+type chatRequest struct {
+	Model          string          `json:"model"`
+	Messages       []chatMessage   `json:"messages"`
+	Temperature    *float64        `json:"temperature,omitempty"`
+	MaxTokens      int             `json:"max_tokens,omitempty"`
+	ResponseFormat *responseFormat `json:"response_format,omitempty"`
+}
+
+type chatResponse struct {
+	Model   string `json:"model"`
+	Choices []struct {
+		Message struct {
+			Content *string `json:"content"`
+			Refusal *string `json:"refusal"`
+		} `json:"message"`
+		FinishReason string `json:"finish_reason"`
+	} `json:"choices"`
+	Usage struct {
+		PromptTokens     int `json:"prompt_tokens"`
+		CompletionTokens int `json:"completion_tokens"`
+	} `json:"usage"`
+	Error json.RawMessage `json:"error"`
+}
+
+// schemaInstruction is appended to the system prompt in the json_object and
+// prompt_only modes, where the schema is not sent in response_format.
+const schemaInstruction = "Reply with only a JSON object, and no other text, that matches this JSON Schema:\n"
+
+// Generate sends req to {base}/chat/completions.
+func (p *Provider) Generate(ctx context.Context, req llm.Request) (llm.Response, error) {
+	resp, err := p.generate(ctx, req)
+	return resp, redact(err, p.apiKey)
+}
+
+func (p *Provider) generate(ctx context.Context, req llm.Request) (llm.Response, error) {
+	if err := req.Validate(); err != nil {
+		return llm.Response{}, fmt.Errorf("openai: generate: %w", err)
+	}
+	if p.model == "" {
+		return llm.Response{}, errors.New("openai: generate: no model configured")
+	}
+	body := chatRequest{
+		Model:       p.model,
+		Temperature: req.Temperature,
+		MaxTokens:   req.MaxTokens,
+	}
+	system := req.System
+	if req.Schema != nil {
+		switch p.mode {
+		case JSONSchema:
+			body.ResponseFormat = &responseFormat{
+				Type:       "json_schema",
+				JSONSchema: &jsonSchemaFormat{Name: req.Schema.Name, Schema: req.Schema.Schema, Strict: true},
+			}
+		case JSONObject:
+			body.ResponseFormat = &responseFormat{Type: "json_object"}
+			system = appendInstruction(system, req.Schema.Schema)
+		case PromptOnly:
+			system = appendInstruction(system, req.Schema.Schema)
+		}
+	}
+	if system != "" {
+		body.Messages = append(body.Messages, chatMessage{Role: "system", Content: system})
+	}
+	for _, m := range req.Messages {
+		body.Messages = append(body.Messages, chatMessage{Role: string(m.Role), Content: m.Content})
+	}
+	payload, err := json.Marshal(body)
+	if err != nil {
+		return llm.Response{}, fmt.Errorf("openai: generate: encode request: %w", err)
+	}
+
+	if req.Timeout > 0 {
+		var cancel context.CancelFunc
+		ctx, cancel = context.WithTimeout(ctx, req.Timeout)
+		defer cancel()
+	}
+	raw, status, err := p.do(ctx, http.MethodPost, "/chat/completions", payload)
+	if err != nil {
+		return llm.Response{}, fmt.Errorf("openai: generate: %w", err)
+	}
+
+	var cr chatResponse
+	if err := json.Unmarshal(raw, &cr); err != nil {
+		return llm.Response{}, fmt.Errorf("openai: generate: decode response: %w", err)
+	}
+	if len(cr.Error) > 0 && string(cr.Error) != "null" {
+		// OpenRouter can report an upstream failure in a 2xx body.
+		return llm.Response{}, fmt.Errorf("openai: generate: %w", llm.NewProviderError(status, raw, p.apiKey))
+	}
+	if len(cr.Choices) == 0 {
+		return llm.Response{}, errors.New("openai: generate: response has no choices")
+	}
+	choice := cr.Choices[0]
+	resp := llm.Response{
+		Usage:        llm.Usage{InputTokens: cr.Usage.PromptTokens, OutputTokens: cr.Usage.CompletionTokens},
+		Model:        cr.Model,
+		FinishReason: choice.FinishReason,
+	}
+	if choice.Message.Content != nil {
+		resp.Text = *choice.Message.Content
+	}
+	if req.Schema == nil {
+		return resp, nil
+	}
+	if choice.Message.Refusal != nil && *choice.Message.Refusal != "" {
+		return resp, fmt.Errorf("openai: generate: model refused the structured request: %w", llm.ErrBadOutput)
+	}
+	if p.mode == PromptOnly {
+		resp.JSON = firstJSONObject(resp.Text)
+	} else if text := strings.TrimSpace(resp.Text); isJSONObject(text) {
+		resp.JSON = json.RawMessage(text)
+	}
+	if resp.JSON == nil {
+		return resp, fmt.Errorf("openai: generate: reply holds no JSON object: %w", llm.ErrBadOutput)
+	}
+	return resp, nil
+}
+
+func appendInstruction(system string, schema json.RawMessage) string {
+	instruction := schemaInstruction + string(schema)
+	if system == "" {
+		return instruction
+	}
+	return system + "\n\n" + instruction
+}
+
+// isJSONObject reports whether s is exactly one JSON object.
+func isJSONObject(s string) bool {
+	return strings.HasPrefix(s, "{") && json.Valid([]byte(s))
+}
+
+// firstJSONObject returns the first complete JSON object in s, trying each
+// "{" in order, or nil when there is none. Text around it, such as prose or
+// a Markdown code fence, is ignored.
+func firstJSONObject(s string) json.RawMessage {
+	for i := strings.IndexByte(s, '{'); i >= 0; {
+		var obj json.RawMessage
+		if err := json.NewDecoder(strings.NewReader(s[i:])).Decode(&obj); err == nil {
+			return obj
+		}
+		next := strings.IndexByte(s[i+1:], '{')
+		if next < 0 {
+			break
+		}
+		i += 1 + next
+	}
+	return nil
+}
+
+type modelsResponse struct {
+	Data []struct {
+		ID   string `json:"id"`
+		Name string `json:"name"`
+	} `json:"data"`
+}
+
+// ListModels returns the models {base}/models lists.
+func (p *Provider) ListModels(ctx context.Context) ([]llm.Model, error) {
+	models, err := p.listModels(ctx)
+	return models, redact(err, p.apiKey)
+}
+
+func (p *Provider) listModels(ctx context.Context) ([]llm.Model, error) {
+	raw, _, err := p.do(ctx, http.MethodGet, "/models", nil)
+	if err != nil {
+		return nil, fmt.Errorf("openai: list models: %w", err)
+	}
+	var mr modelsResponse
+	if err := json.Unmarshal(raw, &mr); err != nil {
+		return nil, fmt.Errorf("openai: list models: decode response: %w", err)
+	}
+	if mr.Data == nil {
+		return nil, errors.New("openai: list models: response has no data list")
+	}
+	models := make([]llm.Model, 0, len(mr.Data))
+	for i, m := range mr.Data {
+		if m.ID == "" {
+			return nil, fmt.Errorf("openai: list models: model %d has no id", i)
+		}
+		name := m.Name
+		if name == "" {
+			name = m.ID
+		}
+		models = append(models, llm.Model{ID: m.ID, DisplayName: name})
+	}
+	return models, nil
+}
+
+// Verify checks the credentials with an authenticated ListModels call.
+func (p *Provider) Verify(ctx context.Context) error {
+	_, err := p.listModels(ctx)
+	return redact(err, p.apiKey)
+}
+
+// do sends one request and returns the body and status of a 2xx response.
+// Any other status becomes the matching llm typed error.
+func (p *Provider) do(ctx context.Context, method, path string, payload []byte) ([]byte, int, error) {
+	var reqBody io.Reader
+	if payload != nil {
+		reqBody = bytes.NewReader(payload)
+	}
+	httpReq, err := http.NewRequestWithContext(ctx, method, p.base+path, reqBody)
+	if err != nil {
+		// The parse error names the URL, whose path may hold the API key.
+		return nil, 0, errors.New("build request: request URL is invalid")
+	}
+	for name, values := range p.headers {
+		httpReq.Header[name] = values
+	}
+	if payload != nil {
+		httpReq.Header.Set("Content-Type", "application/json")
+	}
+	if p.apiKey != "" {
+		httpReq.Header.Set("Authorization", "Bearer "+p.apiKey)
+	}
+
+	httpResp, err := p.client.Do(httpReq)
+	if err != nil {
+		return nil, 0, p.transportError(err)
+	}
+	defer httpResp.Body.Close()
+
+	if httpResp.StatusCode < 200 || httpResp.StatusCode > 299 {
+		body, err := io.ReadAll(io.LimitReader(httpResp.Body, maxErrorBody))
+		if err != nil {
+			return nil, httpResp.StatusCode, p.transportError(err)
+		}
+		return nil, httpResp.StatusCode, p.statusError(httpResp, body)
+	}
+	body, err := io.ReadAll(io.LimitReader(httpResp.Body, maxResponseBody+1))
+	if err != nil {
+		return nil, httpResp.StatusCode, p.transportError(err)
+	}
+	if len(body) > maxResponseBody {
+		return nil, httpResp.StatusCode, fmt.Errorf("response body exceeds %d bytes", maxResponseBody)
+	}
+	return body, httpResp.StatusCode, nil
+}
+
+// statusError maps a non-2xx response to an llm typed error.
+func (p *Provider) statusError(resp *http.Response, body []byte) error {
+	switch resp.StatusCode {
+	case http.StatusUnauthorized, http.StatusForbidden:
+		return fmt.Errorf("HTTP %d: %w", resp.StatusCode, llm.ErrAuth)
+	case http.StatusTooManyRequests:
+		return llm.NewRateLimitedError(retryAfter(resp.Header.Get("Retry-After"), time.Now()), p.apiKey)
+	case http.StatusRequestTimeout:
+		return fmt.Errorf("HTTP %d: %w", resp.StatusCode, llm.ErrTimeout)
+	default:
+		return llm.NewProviderError(resp.StatusCode, body, p.apiKey)
+	}
+}
+
+// retryAfter parses a Retry-After header, in delay-seconds or HTTP-date
+// form. A missing, malformed or past value means the vendor gave no usable
+// wait, reported as 0.
+func retryAfter(value string, now time.Time) time.Duration {
+	value = strings.TrimSpace(value)
+	if value == "" {
+		return 0
+	}
+	if secs, err := strconv.ParseInt(value, 10, 64); err == nil || errors.Is(err, strconv.ErrRange) {
+		if secs < 0 {
+			return 0
+		}
+		// time.Duration counts nanoseconds in an int64; a larger wait is
+		// capped to the most whole seconds it holds instead of overflowing.
+		if secs > maxRetryAfterSeconds {
+			secs = maxRetryAfterSeconds
+		}
+		return time.Duration(secs) * time.Second
+	}
+	if at, err := http.ParseTime(value); err == nil && at.After(now) {
+		return at.Sub(now).Round(time.Second)
+	}
+	return 0
+}
+
+// maxRetryAfterSeconds is the largest delay-seconds value retryAfter
+// returns unchanged: the most whole seconds a time.Duration holds.
+const maxRetryAfterSeconds = math.MaxInt64 / int64(time.Second)
+
+// noRedirectClient returns an HTTP client that never follows a redirect.
+// A followed redirect would resend the credential headers, which net/http
+// strips only for its own list of sensitive headers and only across hosts;
+// instead the 3xx response is returned and becomes a provider error.
+func noRedirectClient() *http.Client {
+	return &http.Client{
+		CheckRedirect: func(*http.Request, []*http.Request) error {
+			return http.ErrUseLastResponse
+		},
+	}
+}
+
+func isTimeout(err error) bool {
+	var ne net.Error
+	return errors.Is(err, context.DeadlineExceeded) || (errors.As(err, &ne) && ne.Timeout())
+}
+
+// transportFailure is a failed HTTP exchange. It carries the cause's text
+// with the request URL removed and the API key redacted, and unwraps only to
+// the cause's category: llm.ErrTimeout, context.Canceled or nothing.
+type transportFailure struct {
+	text string
+	kind error
+}
+
+func (e *transportFailure) Error() string { return e.text }
+
+// GoString keeps %#v to the redacted Error text instead of the fields.
+func (e *transportFailure) GoString() string { return e.text }
+
+func (e *transportFailure) Unwrap() error { return e.kind }
+
+// transportError reports a failure to complete the HTTP exchange. A
+// *url.Error names the request URL, and a base URL path may hold the API
+// key, so only the wrapped cause is kept, rendered with the key redacted.
+func (p *Provider) transportError(err error) error {
+	var kind error
+	switch {
+	case isTimeout(err):
+		kind = llm.ErrTimeout
+	case errors.Is(err, context.Canceled):
+		kind = context.Canceled
+	}
+	var ue *url.Error
+	if errors.As(err, &ue) {
+		err = ue.Err
+	}
+	text := "transport: " + err.Error()
+	if kind == llm.ErrTimeout {
+		text = fmt.Sprintf("%s: %s", llm.ErrTimeout, text)
+	}
+	return &transportFailure{text: llm.Redact(text, p.apiKey), kind: kind}
+}
+
+// redactedError stands in for one layer of an error chain that holds the
+// API key. Its text is the layer's text with the key redacted, and Unwrap
+// returns the layer's causes passed through redact, so no error reached by
+// unwrapping has text holding the key. Is consults the original layer and
+// its chain, so sentinels still match. As does too. The llm typed errors
+// remove the key from their own complete text, fixed words included, so
+// they always match; As refuses a match whose text, or whose %#v form,
+// holds the key, so it never hands back an error that can print it.
+type redactedError struct {
+	text string
+	err  error
+	key  string
+}
+
+func (e *redactedError) Error() string { return e.text }
+
+// GoString keeps %#v from printing the fields, which hold the key.
+func (e *redactedError) GoString() string { return e.text }
+
+func (e *redactedError) Unwrap() error { return redact(errors.Unwrap(e.err), e.key) }
+
+func (e *redactedError) Is(target error) bool { return errors.Is(e.err, target) }
+
+func (e *redactedError) As(target any) bool {
+	if !errors.As(e.err, target) {
+		return false
+	}
+	found := reflect.ValueOf(target).Elem()
+	matched, isErr := found.Interface().(error)
+	if (isErr && holdsKey(matched, e.key)) || strings.Contains(fmt.Sprintf("%#v", found.Interface()), e.key) {
+		found.SetZero()
+		return false
+	}
+	return true
+}
+
+// redactedJoin is redactedError for a layer with several causes, such as
+// one built by errors.Join or by fmt.Errorf with more than one %w.
+type redactedJoin struct {
+	redactedError
+}
+
+func (e *redactedJoin) Unwrap() []error {
+	causes := e.err.(interface{ Unwrap() []error }).Unwrap()
+	safe := make([]error, len(causes))
+	for i, c := range causes {
+		safe[i] = redact(c, e.key)
+	}
+	return safe
+}
+
+// redact is the backstop every exported method applies to its error: with
+// a non-empty key, it returns a stand-in whose text, and the text of every
+// error it unwraps to, has the key redacted. Every non-nil err is wrapped,
+// even one whose text lacks the key, because %#v of an unwrapped error
+// prints its struct field names, and a key may spell one.
+func redact(err error, key string) error {
+	if err == nil || key == "" {
+		return err
+	}
+	re := redactedError{text: llm.Redact(err.Error(), key), err: err, key: key}
+	if _, ok := err.(interface{ Unwrap() []error }); ok {
+		return &redactedJoin{re}
+	}
+	return &re
+}
+
+// holdsKey reports whether the text of err or of any error in its chain
+// contains key.
+func holdsKey(err error, key string) bool {
+	if err == nil {
+		return false
+	}
+	if strings.Contains(err.Error(), key) {
+		return true
+	}
+	switch u := err.(type) {
+	case interface{ Unwrap() error }:
+		return holdsKey(u.Unwrap(), key)
+	case interface{ Unwrap() []error }:
+		for _, c := range u.Unwrap() {
+			if holdsKey(c, key) {
+				return true
+			}
+		}
+	}
+	return false
+}

internal/ai/llm/openai/testdata/README.md

@@ -0,0 +1,71 @@
+# OpenAI-compatible adapter fixtures
+
+These are the vendor response bodies the contract tests in `openai_test.go`
+replay. They are **not live captures**. Product AI is tested with fakes, and
+live vendor calls are opt-in and never use credentials, so no request was
+sent to a vendor to make them. Each fixture is adapted from the response
+shape in that vendor's public API documentation or open source, then
+sanitized:
+
+- IDs, timestamps, fingerprints and token counts are illustrative values in
+  the documented format, not values from a real account.
+- Message content is replaced with MealQuest dinner text.
+- No real credential appears anywhere. `{{KEY}}` is a placeholder the tests
+  replace with a fake key, to prove the adapter redacts a key echoed back in
+  a vendor body.
+
+The tests check the adapter against these bodies with independent
+assertions on both the request sent (path, headers, `response_format`,
+messages) and the response decoded. The request side does not depend on the
+fixtures.
+
+Below, *not in the public example* marks fields or values that were added
+for a test case and do not come from the vendor's documented example.
+
+## OpenAI
+
+Sources: API reference, "The chat completion object" and "List models"
+(<https://platform.openai.com/docs/api-reference/chat/object>,
+<https://platform.openai.com/docs/api-reference/models/list>); the
+Structured Outputs guide, for `refusal`
+(<https://platform.openai.com/docs/guides/structured-outputs>); and the error
+codes guide (<https://platform.openai.com/docs/guides/error-codes>).
+
+| Fixture | Shape | Not in the public example |
+| --- | --- | --- |
+| `openai_chat_json_schema.json` | Chat completion object with `usage` details, `service_tier`, `system_fingerprint`. | The JSON reply content. |
+| `openai_chat_refusal.json` | Structured Outputs refusal: `content: null`, `refusal` set. | — |
+| `openai_models.json` | `{object: list, data: [model]}`. | — |
+| `openai_error_invalid_key.json` | Error object, `code: invalid_api_key`, message echoing the key. | The full key in the message; OpenAI masks most of it. Kept whole to test redaction. |
+| `openai_error_server.json` | Error object, `type: server_error`. | The `Authorization: Bearer {{KEY}}` text; added to test redaction. |
+
+## OpenRouter
+
+Sources: API reference, chat completion response and errors
+(<https://openrouter.ai/docs/api-reference/overview>,
+<https://openrouter.ai/docs/api-reference/errors>), and "List available
+models" (<https://openrouter.ai/docs/api-reference/list-available-models>).
+
+| Fixture | Shape | Not in the public example |
+| --- | --- | --- |
+| `openrouter_chat_json_object.json` | Chat completion with `provider`, `native_finish_reason` and `message.reasoning`. | The JSON reply content. |
+| `openrouter_chat_upstream_error.json` | An `error` object (`code`, `message`, `metadata.provider_name`, `metadata.raw`) in an HTTP 200 body, which OpenRouter documents for upstream failures. | `user_id`. |
+| `openrouter_error_rate_limited.json` | Error object, `code: 429`, rate-limit `metadata`. | The `Key {{KEY}}` text; added to test redaction. |
+| `openrouter_models.json` | `{data: [model]}` with `name`, `context_length`, `architecture`, `pricing`, `supported_parameters`. | The second model is a minimal entry, to test optional fields. |
+
+## Ollama
+
+Ollama's OpenAI compatibility page
+(<https://github.com/ollama/ollama/blob/main/docs/openai.md>) documents
+requests but shows no response bodies. The shapes come from its `openai`
+middleware source (<https://github.com/ollama/ollama/blob/main/openai/openai.go>):
+`chatcmpl-<n>` IDs, `system_fingerprint: fp_ollama`, `owned_by: library` on
+models, and errors as `{error: {message, type: api_error, param, code}}`.
+
+| Fixture | Shape | Not in the public example |
+| --- | --- | --- |
+| `ollama_chat_text.json` | Plain chat completion. | — |
+| `ollama_chat_prompt_only.json` | Chat completion. | The reply text: prose and stray braces around a fenced JSON object, to test prompt-only extraction. |
+| `ollama_chat_truncated.json` | Chat completion with `finish_reason: length`. | The cut-off JSON reply. |
+| `ollama_models.json` | `{object: list, data: [model]}`. | — |
+| `ollama_error_not_found.json` | Middleware error object for a missing model. | — |

internal/ai/llm/openai/testdata/ollama_chat_prompt_only.json

@@ -0,0 +1,18 @@
+{
+  "id": "chatcmpl-417",
+  "object": "chat.completion",
+  "created": 1741570322,
+  "model": "llama3.2",
+  "system_fingerprint": "fp_ollama",
+  "choices": [
+    {
+      "index": 0,
+      "message": {
+        "role": "assistant",
+        "content": "Sure! Here is a dinner {idea} for you:\n```json\n{\"dinners\": [{\"name\": \"Crock pot chili\", \"why\": \"A Quick dinner like your {Regular} stew.\"}]}\n```\nEnjoy {\"not\": \"this one\"}!"
+      },
+      "finish_reason": "stop"
+    }
+  ],
+  "usage": {"prompt_tokens": 512, "completion_tokens": 58, "total_tokens": 570}
+}

internal/ai/llm/openai/testdata/ollama_chat_text.json

@@ -0,0 +1,11 @@
+{
+  "id": "chatcmpl-419",
+  "object": "chat.completion",
+  "created": 1741570340,
+  "model": "llama3.2",
+  "system_fingerprint": "fp_ollama",
+  "choices": [
+    {"index": 0, "message": {"role": "assistant", "content": "Try a lemon orzo bake tonight."}, "finish_reason": "stop"}
+  ],
+  "usage": {"prompt_tokens": 40, "completion_tokens": 9, "total_tokens": 49}
+}

internal/ai/llm/openai/testdata/ollama_chat_truncated.json

@@ -0,0 +1,15 @@
+{
+  "id": "chatcmpl-418",
+  "object": "chat.completion",
+  "created": 1741570330,
+  "model": "llama3.2",
+  "system_fingerprint": "fp_ollama",
+  "choices": [
+    {
+      "index": 0,
+      "message": {"role": "assistant", "content": "{\"dinners\": [{\"name\": \"Crock pot ch"},
+      "finish_reason": "length"
+    }
+  ],
+  "usage": {"prompt_tokens": 512, "completion_tokens": 16, "total_tokens": 528}
+}

internal/ai/llm/openai/testdata/ollama_error_not_found.json

@@ -0,0 +1 @@
+{"error": {"message": "model \"llama9\" not found, try pulling it first", "type": "api_error", "param": null, "code": null}}

internal/ai/llm/openai/testdata/ollama_models.json

@@ -0,0 +1,7 @@
+{
+  "object": "list",
+  "data": [
+    {"id": "llama3.2:latest", "object": "model", "created": 1741000000, "owned_by": "library"},
+    {"id": "qwen2.5:7b", "object": "model", "created": 1740000000, "owned_by": "library"}
+  ]
+}

internal/ai/llm/openai/testdata/openai_chat_json_schema.json

@@ -0,0 +1,28 @@
+{
+  "id": "chatcmpl-B9MHDbslfkBeAs8l4bebGdFOJ6PeG",
+  "object": "chat.completion",
+  "created": 1741570283,
+  "model": "gpt-4o-2024-08-06",
+  "choices": [
+    {
+      "index": 0,
+      "message": {
+        "role": "assistant",
+        "content": "{\"dinners\":[{\"name\":\"Sheet-pan gnocchi\",\"why\":\"Like your Regular tray bake, but quicker.\"}]}",
+        "refusal": null,
+        "annotations": []
+      },
+      "logprobs": null,
+      "finish_reason": "stop"
+    }
+  ],
+  "usage": {
+    "prompt_tokens": 1117,
+    "completion_tokens": 46,
+    "total_tokens": 1163,
+    "prompt_tokens_details": {"cached_tokens": 0, "audio_tokens": 0},
+    "completion_tokens_details": {"reasoning_tokens": 0, "audio_tokens": 0, "accepted_prediction_tokens": 0, "rejected_prediction_tokens": 0}
+  },
+  "service_tier": "default",
+  "system_fingerprint": "fp_fc9f1d7035"
+}

internal/ai/llm/openai/testdata/openai_chat_refusal.json

@@ -0,0 +1,16 @@
+{
+  "id": "chatcmpl-B9MHDbslfkBeAs8l4bebGdFOJ6PeH",
+  "object": "chat.completion",
+  "created": 1741570290,
+  "model": "gpt-4o-2024-08-06",
+  "choices": [
+    {
+      "index": 0,
+      "message": {"role": "assistant", "content": null, "refusal": "I'm sorry, I can't help with that request.", "annotations": []},
+      "logprobs": null,
+      "finish_reason": "stop"
+    }
+  ],
+  "usage": {"prompt_tokens": 210, "completion_tokens": 11, "total_tokens": 221},
+  "system_fingerprint": "fp_fc9f1d7035"
+}

internal/ai/llm/openai/testdata/openai_error_invalid_key.json

@@ -0,0 +1,8 @@
+{
+  "error": {
+    "message": "Incorrect API key provided: {{KEY}}. You can find your API key at https://platform.openai.com/account/api-keys.",
+    "type": "invalid_request_error",
+    "param": null,
+    "code": "invalid_api_key"
+  }
+}

internal/ai/llm/openai/testdata/openai_error_server.json

@@ -0,0 +1 @@
+{"error": {"message": "The server had an error while processing your request. Authorization: Bearer {{KEY}}", "type": "server_error", "param": null, "code": null}}

internal/ai/llm/openai/testdata/openai_models.json

@@ -0,0 +1,7 @@
+{
+  "object": "list",
+  "data": [
+    {"id": "gpt-4o-2024-08-06", "object": "model", "created": 1722814719, "owned_by": "system"},
+    {"id": "gpt-4o-mini", "object": "model", "created": 1721172741, "owned_by": "system"}
+  ]
+}

internal/ai/llm/openai/testdata/openrouter_chat_json_object.json

@@ -0,0 +1,22 @@
+{
+  "id": "gen-1741570300-xQmT9vWb4kR2nP7sL3aE",
+  "provider": "OpenAI",
+  "model": "openai/gpt-4o-mini",
+  "object": "chat.completion",
+  "created": 1741570300,
+  "choices": [
+    {
+      "logprobs": null,
+      "finish_reason": "stop",
+      "native_finish_reason": "stop",
+      "index": 0,
+      "message": {
+        "role": "assistant",
+        "content": "{\n  \"dinners\": [{\"name\": \"Chicken tinga tacos\", \"why\": \"Close to your taco-night Regular.\"}]\n}",
+        "refusal": null,
+        "reasoning": null
+      }
+    }
+  ],
+  "usage": {"prompt_tokens": 842, "completion_tokens": 31, "total_tokens": 873}
+}

internal/ai/llm/openai/testdata/openrouter_chat_upstream_error.json

@@ -0,0 +1,5 @@
+{
+  "id": "gen-1741570311-aB3dE5fG7hJ9kL1mN2pQ",
+  "error": {"code": 502, "message": "Upstream error from provider", "metadata": {"provider_name": "Lambda", "raw": "upstream returned 502"}},
+  "user_id": "user_2abcDEF"
+}

internal/ai/llm/openai/testdata/openrouter_error_rate_limited.json

@@ -0,0 +1 @@
+{"error": {"code": 429, "message": "Rate limit exceeded: free-models-per-min. Key {{KEY}}", "metadata": {"headers": {"X-RateLimit-Limit": "20", "X-RateLimit-Remaining": "0"}}}}

internal/ai/llm/openai/testdata/openrouter_models.json

@@ -0,0 +1,22 @@
+{
+  "data": [
+    {
+      "id": "openai/gpt-4o-mini",
+      "canonical_slug": "openai/gpt-4o-mini",
+      "name": "OpenAI: GPT-4o-mini",
+      "created": 1721260800,
+      "description": "GPT-4o mini is OpenAI's newest model after GPT-4 Omni.",
+      "context_length": 128000,
+      "architecture": {"modality": "text+image->text", "input_modalities": ["text", "image"], "output_modalities": ["text"], "tokenizer": "GPT"},
+      "pricing": {"prompt": "0.00000015", "completion": "0.0000006"},
+      "supported_parameters": ["max_tokens", "temperature", "response_format", "structured_outputs"]
+    },
+    {
+      "id": "anthropic/claude-sonnet-5",
+      "name": "Anthropic: Claude Sonnet 5",
+      "created": 1767225600,
+      "context_length": 200000,
+      "supported_parameters": ["max_tokens", "temperature"]
+    }
+  ]
+}