Fixed: #1675

fix(gemini): add model definitions for Gemini 3.1 Pro High and Image

config.example.yaml

@@ -159,6 +159,7 @@ nonstream-keepalive-interval: 0
 #       sensitive-words:             # optional: words to obfuscate with zero-width characters
 #         - "API"
 #         - "proxy"
+#       cache-user-id: true          # optional: default is false; set true to reuse cached user_id per API key instead of generating a random one each request
 
 # Default headers for Claude API requests. Update when Claude Code releases new versions.
 # These are used as fallbacks when the client does not send its own headers.

internal/api/modules/amp/proxy.go

@@ -3,6 +3,8 @@ package amp
 import (
 	"bytes"
 	"compress/gzip"
+	"context"
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -188,6 +190,10 @@ func createReverseProxy(upstreamURL string, secretSource SecretSource) (*httputi
 
 	// Error handler for proxy failures
 	proxy.ErrorHandler = func(rw http.ResponseWriter, req *http.Request, err error) {
+		// Client-side cancellations are common during polling; suppress logging in this case
+		if errors.Is(err, context.Canceled) {
+			return
+		}
 		log.Errorf("amp upstream proxy error for %s %s: %v", req.Method, req.URL.Path, err)
 		rw.Header().Set("Content-Type", "application/json")
 		rw.WriteHeader(http.StatusBadGateway)

internal/api/modules/amp/proxy_test.go

@@ -493,6 +493,30 @@ func TestReverseProxy_ErrorHandler(t *testing.T) {
 	}
 }
 
+func TestReverseProxy_ErrorHandler_ContextCanceled(t *testing.T) {
+	// Test that context.Canceled errors return 499 without generic error response
+	proxy, err := createReverseProxy("http://example.com", NewStaticSecretSource(""))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Create a canceled context to trigger the cancellation path
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel() // Cancel immediately
+
+	req := httptest.NewRequest(http.MethodGet, "/test", nil).WithContext(ctx)
+	rr := httptest.NewRecorder()
+
+	// Directly invoke the ErrorHandler with context.Canceled
+	proxy.ErrorHandler(rr, req, context.Canceled)
+
+	// Body should be empty for canceled requests (no JSON error response)
+	body := rr.Body.Bytes()
+	if len(body) > 0 {
+		t.Fatalf("expected empty body for canceled context, got: %s", body)
+	}
+}
+
 func TestReverseProxy_FullRoundTrip_Gzip(t *testing.T) {
 	// Upstream returns gzipped JSON without Content-Encoding header
 	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {

internal/config/config.go

@@ -301,6 +301,10 @@ type CloakConfig struct {
 	// SensitiveWords is a list of words to obfuscate with zero-width characters.
 	// This can help bypass certain content filters.
 	SensitiveWords []string `yaml:"sensitive-words,omitempty" json:"sensitive-words,omitempty"`
+
+	// CacheUserID controls whether Claude user_id values are cached per API key.
+	// When false, a fresh random user_id is generated for every request.
+	CacheUserID *bool `yaml:"cache-user-id,omitempty" json:"cache-user-id,omitempty"`
 }
 
 // ClaudeKey represents the configuration for a Claude API key,

internal/registry/model_definitions_static_data.go

@@ -184,6 +184,21 @@ func GetGeminiModels() []*ModelInfo {
 			SupportedGenerationMethods: []string{"generateContent", "countTokens", "createCachedContent", "batchGenerateContent"},
 			Thinking:                   &ThinkingSupport{Min: 128, Max: 32768, ZeroAllowed: false, DynamicAllowed: true, Levels: []string{"low", "high"}},
 		},
+		{
+			ID:                         "gemini-3.1-pro-preview",
+			Object:                     "model",
+			Created:                    1771459200,
+			OwnedBy:                    "google",
+			Type:                       "gemini",
+			Name:                       "models/gemini-3.1-pro-preview",
+			Version:                    "3.1",
+			DisplayName:                "Gemini 3.1 Pro Preview",
+			Description:                "Gemini 3.1 Pro Preview",
+			InputTokenLimit:            1048576,
+			OutputTokenLimit:           65536,
+			SupportedGenerationMethods: []string{"generateContent", "countTokens", "createCachedContent", "batchGenerateContent"},
+			Thinking:                   &ThinkingSupport{Min: 128, Max: 32768, ZeroAllowed: false, DynamicAllowed: true, Levels: []string{"low", "high"}},
+		},
 		{
 			ID:                         "gemini-3-flash-preview",
 			Object:                     "model",
@@ -297,7 +312,7 @@ func GetGeminiVertexModels() []*ModelInfo {
 		{
 			ID:                         "gemini-3.1-pro-preview",
 			Object:                     "model",
-			Created:                    1771491385,
+			Created:                    1771459200,
 			OwnedBy:                    "google",
 			Type:                       "gemini",
 			Name:                       "models/gemini-3.1-pro-preview",
@@ -307,7 +322,7 @@ func GetGeminiVertexModels() []*ModelInfo {
 			InputTokenLimit:            1048576,
 			OutputTokenLimit:           65536,
 			SupportedGenerationMethods: []string{"generateContent", "countTokens", "createCachedContent", "batchGenerateContent"},
-			Thinking:                   &ThinkingSupport{Min: 1, Max: 32768, ZeroAllowed: false, DynamicAllowed: true, Levels: []string{"low", "high"}},
+			Thinking:                   &ThinkingSupport{Min: 128, Max: 32768, ZeroAllowed: false, DynamicAllowed: true, Levels: []string{"low", "high"}},
 		},
 		{
 			ID:                         "gemini-3-pro-image-preview",
@@ -451,6 +466,21 @@ func GetGeminiCLIModels() []*ModelInfo {
 			SupportedGenerationMethods: []string{"generateContent", "countTokens", "createCachedContent", "batchGenerateContent"},
 			Thinking:                   &ThinkingSupport{Min: 128, Max: 32768, ZeroAllowed: false, DynamicAllowed: true, Levels: []string{"low", "high"}},
 		},
+		{
+			ID:                         "gemini-3.1-pro-preview",
+			Object:                     "model",
+			Created:                    1771459200,
+			OwnedBy:                    "google",
+			Type:                       "gemini",
+			Name:                       "models/gemini-3.1-pro-preview",
+			Version:                    "3.1",
+			DisplayName:                "Gemini 3.1 Pro Preview",
+			Description:                "Gemini 3.1 Pro Preview",
+			InputTokenLimit:            1048576,
+			OutputTokenLimit:           65536,
+			SupportedGenerationMethods: []string{"generateContent", "countTokens", "createCachedContent", "batchGenerateContent"},
+			Thinking:                   &ThinkingSupport{Min: 128, Max: 32768, ZeroAllowed: false, DynamicAllowed: true, Levels: []string{"low", "high"}},
+		},
 		{
 			ID:                         "gemini-3-flash-preview",
 			Object:                     "model",
@@ -532,6 +562,21 @@ func GetAIStudioModels() []*ModelInfo {
 			SupportedGenerationMethods: []string{"generateContent", "countTokens", "createCachedContent", "batchGenerateContent"},
 			Thinking:                   &ThinkingSupport{Min: 128, Max: 32768, ZeroAllowed: false, DynamicAllowed: true},
 		},
+		{
+			ID:                         "gemini-3.1-pro-preview",
+			Object:                     "model",
+			Created:                    1771459200,
+			OwnedBy:                    "google",
+			Type:                       "gemini",
+			Name:                       "models/gemini-3.1-pro-preview",
+			Version:                    "3.1",
+			DisplayName:                "Gemini 3.1 Pro Preview",
+			Description:                "Gemini 3.1 Pro Preview",
+			InputTokenLimit:            1048576,
+			OutputTokenLimit:           65536,
+			SupportedGenerationMethods: []string{"generateContent", "countTokens", "createCachedContent", "batchGenerateContent"},
+			Thinking:                   &ThinkingSupport{Min: 128, Max: 32768, ZeroAllowed: false, DynamicAllowed: true},
+		},
 		{
 			ID:                         "gemini-3-flash-preview",
 			Object:                     "model",
@@ -918,6 +963,7 @@ func GetAntigravityModelConfig() map[string]*AntigravityModelConfig {
 		"gemini-2.5-flash-lite":      {Thinking: &ThinkingSupport{Min: 0, Max: 24576, ZeroAllowed: true, DynamicAllowed: true}},
 		"gemini-3-pro-high":          {Thinking: &ThinkingSupport{Min: 128, Max: 32768, ZeroAllowed: false, DynamicAllowed: true, Levels: []string{"low", "high"}}},
 		"gemini-3-pro-image":         {Thinking: &ThinkingSupport{Min: 128, Max: 32768, ZeroAllowed: false, DynamicAllowed: true, Levels: []string{"low", "high"}}},
+		"gemini-3.1-pro-high":        {Thinking: &ThinkingSupport{Min: 128, Max: 32768, ZeroAllowed: false, DynamicAllowed: true, Levels: []string{"low", "high"}}},
 		"gemini-3-flash":             {Thinking: &ThinkingSupport{Min: 128, Max: 32768, ZeroAllowed: false, DynamicAllowed: true, Levels: []string{"minimal", "low", "medium", "high"}}},
 		"claude-sonnet-4-5-thinking": {Thinking: &ThinkingSupport{Min: 1024, Max: 128000, ZeroAllowed: true, DynamicAllowed: true}, MaxCompletionTokens: 64000},
 		"claude-opus-4-5-thinking":   {Thinking: &ThinkingSupport{Min: 1024, Max: 128000, ZeroAllowed: true, DynamicAllowed: true}, MaxCompletionTokens: 64000},

internal/runtime/executor/claude_executor.go

@@ -117,7 +117,7 @@ func (e *ClaudeExecutor) Execute(ctx context.Context, auth *cliproxyauth.Auth, r
 
 	// Apply cloaking (system prompt injection, fake user ID, sensitive word obfuscation)
 	// based on client type and configuration.
-	body = applyCloaking(ctx, e.cfg, auth, body, baseModel)
+	body = applyCloaking(ctx, e.cfg, auth, body, baseModel, apiKey)
 
 	requestedModel := payloadRequestedModel(opts, req.Model)
 	body = applyPayloadConfigWithRoot(e.cfg, baseModel, to.String(), "", body, originalTranslated, requestedModel)
@@ -258,7 +258,7 @@ func (e *ClaudeExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.A
 
 	// Apply cloaking (system prompt injection, fake user ID, sensitive word obfuscation)
 	// based on client type and configuration.
-	body = applyCloaking(ctx, e.cfg, auth, body, baseModel)
+	body = applyCloaking(ctx, e.cfg, auth, body, baseModel, apiKey)
 
 	requestedModel := payloadRequestedModel(opts, req.Model)
 	body = applyPayloadConfigWithRoot(e.cfg, baseModel, to.String(), "", body, originalTranslated, requestedModel)
@@ -982,10 +982,10 @@ func getClientUserAgent(ctx context.Context) string {
 }
 
 // getCloakConfigFromAuth extracts cloak configuration from auth attributes.
-// Returns (cloakMode, strictMode, sensitiveWords).
-func getCloakConfigFromAuth(auth *cliproxyauth.Auth) (string, bool, []string) {
+// Returns (cloakMode, strictMode, sensitiveWords, cacheUserID).
+func getCloakConfigFromAuth(auth *cliproxyauth.Auth) (string, bool, []string, bool) {
 	if auth == nil || auth.Attributes == nil {
-		return "auto", false, nil
+		return "auto", false, nil, false
 	}
 
 	cloakMode := auth.Attributes["cloak_mode"]
@@ -1003,7 +1003,9 @@ func getCloakConfigFromAuth(auth *cliproxyauth.Auth) (string, bool, []string) {
 		}
 	}
 
-	return cloakMode, strictMode, sensitiveWords
+	cacheUserID := strings.EqualFold(strings.TrimSpace(auth.Attributes["cloak_cache_user_id"]), "true")
+
+	return cloakMode, strictMode, sensitiveWords, cacheUserID
 }
 
 // resolveClaudeKeyCloakConfig finds the matching ClaudeKey config and returns its CloakConfig.
@@ -1036,16 +1038,24 @@ func resolveClaudeKeyCloakConfig(cfg *config.Config, auth *cliproxyauth.Auth) *c
 }
 
 // injectFakeUserID generates and injects a fake user ID into the request metadata.
-func injectFakeUserID(payload []byte) []byte {
+// When useCache is false, a new user ID is generated for every call.
+func injectFakeUserID(payload []byte, apiKey string, useCache bool) []byte {
+	generateID := func() string {
+		if useCache {
+			return cachedUserID(apiKey)
+		}
+		return generateFakeUserID()
+	}
+
 	metadata := gjson.GetBytes(payload, "metadata")
 	if !metadata.Exists() {
-		payload, _ = sjson.SetBytes(payload, "metadata.user_id", generateFakeUserID())
+		payload, _ = sjson.SetBytes(payload, "metadata.user_id", generateID())
 		return payload
 	}
 
 	existingUserID := gjson.GetBytes(payload, "metadata.user_id").String()
 	if existingUserID == "" || !isValidUserID(existingUserID) {
-		payload, _ = sjson.SetBytes(payload, "metadata.user_id", generateFakeUserID())
+		payload, _ = sjson.SetBytes(payload, "metadata.user_id", generateID())
 	}
 	return payload
 }
@@ -1082,7 +1092,7 @@ func checkSystemInstructionsWithMode(payload []byte, strictMode bool) []byte {
 
 // applyCloaking applies cloaking transformations to the payload based on config and client.
 // Cloaking includes: system prompt injection, fake user ID, and sensitive word obfuscation.
-func applyCloaking(ctx context.Context, cfg *config.Config, auth *cliproxyauth.Auth, payload []byte, model string) []byte {
+func applyCloaking(ctx context.Context, cfg *config.Config, auth *cliproxyauth.Auth, payload []byte, model string, apiKey string) []byte {
 	clientUserAgent := getClientUserAgent(ctx)
 
 	// Get cloak config from ClaudeKey configuration
@@ -1092,16 +1102,20 @@ func applyCloaking(ctx context.Context, cfg *config.Config, auth *cliproxyauth.A
 	var cloakMode string
 	var strictMode bool
 	var sensitiveWords []string
+	var cacheUserID bool
 
 	if cloakCfg != nil {
 		cloakMode = cloakCfg.Mode
 		strictMode = cloakCfg.StrictMode
 		sensitiveWords = cloakCfg.SensitiveWords
+		if cloakCfg.CacheUserID != nil {
+			cacheUserID = *cloakCfg.CacheUserID
+		}
 	}
 
 	// Fallback to auth attributes if no config found
 	if cloakMode == "" {
-		attrMode, attrStrict, attrWords := getCloakConfigFromAuth(auth)
+		attrMode, attrStrict, attrWords, attrCache := getCloakConfigFromAuth(auth)
 		cloakMode = attrMode
 		if !strictMode {
 			strictMode = attrStrict
@@ -1109,6 +1123,12 @@ func applyCloaking(ctx context.Context, cfg *config.Config, auth *cliproxyauth.A
 		if len(sensitiveWords) == 0 {
 			sensitiveWords = attrWords
 		}
+		if cloakCfg == nil || cloakCfg.CacheUserID == nil {
+			cacheUserID = attrCache
+		}
+	} else if cloakCfg == nil || cloakCfg.CacheUserID == nil {
+		_, _, _, attrCache := getCloakConfigFromAuth(auth)
+		cacheUserID = attrCache
 	}
 
 	// Determine if cloaking should be applied
@@ -1122,7 +1142,7 @@ func applyCloaking(ctx context.Context, cfg *config.Config, auth *cliproxyauth.A
 	}
 
 	// Inject fake user ID
-	payload = injectFakeUserID(payload)
+	payload = injectFakeUserID(payload, apiKey, cacheUserID)
 
 	// Apply sensitive word obfuscation
 	if len(sensitiveWords) > 0 {

internal/runtime/executor/claude_executor_test.go

@@ -2,9 +2,18 @@ package executor
 
 import (
 	"bytes"
+	"context"
+	"io"
+	"net/http"
+	"net/http/httptest"
 	"testing"
 
+	"github.com/router-for-me/CLIProxyAPI/v6/internal/config"
+	cliproxyauth "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/auth"
+	cliproxyexecutor "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/executor"
+	sdktranslator "github.com/router-for-me/CLIProxyAPI/v6/sdk/translator"
 	"github.com/tidwall/gjson"
+	"github.com/tidwall/sjson"
 )
 
 func TestApplyClaudeToolPrefix(t *testing.T) {
@@ -199,6 +208,119 @@ func TestApplyClaudeToolPrefix_NestedToolReference(t *testing.T) {
 	}
 }
 
+func TestClaudeExecutor_ReusesUserIDAcrossModelsWhenCacheEnabled(t *testing.T) {
+	resetUserIDCache()
+
+	var userIDs []string
+	var requestModels []string
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		body, _ := io.ReadAll(r.Body)
+		userID := gjson.GetBytes(body, "metadata.user_id").String()
+		model := gjson.GetBytes(body, "model").String()
+		userIDs = append(userIDs, userID)
+		requestModels = append(requestModels, model)
+		t.Logf("HTTP Server received request: model=%s, user_id=%s, url=%s", model, userID, r.URL.String())
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`{"id":"msg_1","type":"message","model":"claude-3-5-sonnet","role":"assistant","content":[{"type":"text","text":"ok"}],"usage":{"input_tokens":1,"output_tokens":1}}`))
+	}))
+	defer server.Close()
+
+	t.Logf("End-to-end test: Fake HTTP server started at %s", server.URL)
+
+	cacheEnabled := true
+	executor := NewClaudeExecutor(&config.Config{
+		ClaudeKey: []config.ClaudeKey{
+			{
+				APIKey:  "key-123",
+				BaseURL: server.URL,
+				Cloak: &config.CloakConfig{
+					CacheUserID: &cacheEnabled,
+				},
+			},
+		},
+	})
+	auth := &cliproxyauth.Auth{Attributes: map[string]string{
+		"api_key":  "key-123",
+		"base_url": server.URL,
+	}}
+
+	payload := []byte(`{"messages":[{"role":"user","content":[{"type":"text","text":"hi"}]}]}`)
+	models := []string{"claude-3-5-sonnet", "claude-3-5-haiku"}
+	for _, model := range models {
+		t.Logf("Sending request for model: %s", model)
+		modelPayload, _ := sjson.SetBytes(payload, "model", model)
+		if _, err := executor.Execute(context.Background(), auth, cliproxyexecutor.Request{
+			Model:   model,
+			Payload: modelPayload,
+		}, cliproxyexecutor.Options{
+			SourceFormat: sdktranslator.FromString("claude"),
+		}); err != nil {
+			t.Fatalf("Execute(%s) error: %v", model, err)
+		}
+	}
+
+	if len(userIDs) != 2 {
+		t.Fatalf("expected 2 requests, got %d", len(userIDs))
+	}
+	if userIDs[0] == "" || userIDs[1] == "" {
+		t.Fatal("expected user_id to be populated")
+	}
+	t.Logf("user_id[0] (model=%s): %s", requestModels[0], userIDs[0])
+	t.Logf("user_id[1] (model=%s): %s", requestModels[1], userIDs[1])
+	if userIDs[0] != userIDs[1] {
+		t.Fatalf("expected user_id to be reused across models, got %q and %q", userIDs[0], userIDs[1])
+	}
+	if !isValidUserID(userIDs[0]) {
+		t.Fatalf("user_id %q is not valid", userIDs[0])
+	}
+	t.Logf("✓ End-to-end test passed: Same user_id (%s) was used for both models", userIDs[0])
+}
+
+func TestClaudeExecutor_GeneratesNewUserIDByDefault(t *testing.T) {
+	resetUserIDCache()
+
+	var userIDs []string
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		body, _ := io.ReadAll(r.Body)
+		userIDs = append(userIDs, gjson.GetBytes(body, "metadata.user_id").String())
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`{"id":"msg_1","type":"message","model":"claude-3-5-sonnet","role":"assistant","content":[{"type":"text","text":"ok"}],"usage":{"input_tokens":1,"output_tokens":1}}`))
+	}))
+	defer server.Close()
+
+	executor := NewClaudeExecutor(&config.Config{})
+	auth := &cliproxyauth.Auth{Attributes: map[string]string{
+		"api_key":  "key-123",
+		"base_url": server.URL,
+	}}
+
+	payload := []byte(`{"messages":[{"role":"user","content":[{"type":"text","text":"hi"}]}]}`)
+
+	for i := 0; i < 2; i++ {
+		if _, err := executor.Execute(context.Background(), auth, cliproxyexecutor.Request{
+			Model:   "claude-3-5-sonnet",
+			Payload: payload,
+		}, cliproxyexecutor.Options{
+			SourceFormat: sdktranslator.FromString("claude"),
+		}); err != nil {
+			t.Fatalf("Execute call %d error: %v", i, err)
+		}
+	}
+
+	if len(userIDs) != 2 {
+		t.Fatalf("expected 2 requests, got %d", len(userIDs))
+	}
+	if userIDs[0] == "" || userIDs[1] == "" {
+		t.Fatal("expected user_id to be populated")
+	}
+	if userIDs[0] == userIDs[1] {
+		t.Fatalf("expected user_id to change when caching is not enabled, got identical values %q", userIDs[0])
+	}
+	if !isValidUserID(userIDs[0]) || !isValidUserID(userIDs[1]) {
+		t.Fatalf("user_ids should be valid, got %q and %q", userIDs[0], userIDs[1])
+	}
+}
+
 func TestStripClaudeToolPrefixFromResponse_NestedToolReference(t *testing.T) {
 	input := []byte(`{"content":[{"type":"tool_result","tool_use_id":"toolu_123","content":[{"type":"tool_reference","tool_name":"proxy_mcp__nia__manage_resource"}]}]}`)
 	out := stripClaudeToolPrefixFromResponse(input, "proxy_")

internal/runtime/executor/user_id_cache.go

@@ -0,0 +1,89 @@
+package executor
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"sync"
+	"time"
+)
+
+type userIDCacheEntry struct {
+	value  string
+	expire time.Time
+}
+
+var (
+	userIDCache            = make(map[string]userIDCacheEntry)
+	userIDCacheMu          sync.RWMutex
+	userIDCacheCleanupOnce sync.Once
+)
+
+const (
+	userIDTTL                = time.Hour
+	userIDCacheCleanupPeriod = 15 * time.Minute
+)
+
+func startUserIDCacheCleanup() {
+	go func() {
+		ticker := time.NewTicker(userIDCacheCleanupPeriod)
+		defer ticker.Stop()
+		for range ticker.C {
+			purgeExpiredUserIDs()
+		}
+	}()
+}
+
+func purgeExpiredUserIDs() {
+	now := time.Now()
+	userIDCacheMu.Lock()
+	for key, entry := range userIDCache {
+		if !entry.expire.After(now) {
+			delete(userIDCache, key)
+		}
+	}
+	userIDCacheMu.Unlock()
+}
+
+func userIDCacheKey(apiKey string) string {
+	sum := sha256.Sum256([]byte(apiKey))
+	return hex.EncodeToString(sum[:])
+}
+
+func cachedUserID(apiKey string) string {
+	if apiKey == "" {
+		return generateFakeUserID()
+	}
+
+	userIDCacheCleanupOnce.Do(startUserIDCacheCleanup)
+
+	key := userIDCacheKey(apiKey)
+	now := time.Now()
+
+	userIDCacheMu.RLock()
+	entry, ok := userIDCache[key]
+	valid := ok && entry.value != "" && entry.expire.After(now) && isValidUserID(entry.value)
+	userIDCacheMu.RUnlock()
+	if valid {
+		userIDCacheMu.Lock()
+		entry = userIDCache[key]
+		if entry.value != "" && entry.expire.After(now) && isValidUserID(entry.value) {
+			entry.expire = now.Add(userIDTTL)
+			userIDCache[key] = entry
+			userIDCacheMu.Unlock()
+			return entry.value
+		}
+		userIDCacheMu.Unlock()
+	}
+
+	newID := generateFakeUserID()
+
+	userIDCacheMu.Lock()
+	entry, ok = userIDCache[key]
+	if !ok || entry.value == "" || !entry.expire.After(now) || !isValidUserID(entry.value) {
+		entry.value = newID
+	}
+	entry.expire = now.Add(userIDTTL)
+	userIDCache[key] = entry
+	userIDCacheMu.Unlock()
+	return entry.value
+}

internal/runtime/executor/user_id_cache_test.go

@@ -0,0 +1,86 @@
+package executor
+
+import (
+	"testing"
+	"time"
+)
+
+func resetUserIDCache() {
+	userIDCacheMu.Lock()
+	userIDCache = make(map[string]userIDCacheEntry)
+	userIDCacheMu.Unlock()
+}
+
+func TestCachedUserID_ReusesWithinTTL(t *testing.T) {
+	resetUserIDCache()
+
+	first := cachedUserID("api-key-1")
+	second := cachedUserID("api-key-1")
+
+	if first == "" {
+		t.Fatal("expected generated user_id to be non-empty")
+	}
+	if first != second {
+		t.Fatalf("expected cached user_id to be reused, got %q and %q", first, second)
+	}
+}
+
+func TestCachedUserID_ExpiresAfterTTL(t *testing.T) {
+	resetUserIDCache()
+
+	expiredID := cachedUserID("api-key-expired")
+	cacheKey := userIDCacheKey("api-key-expired")
+	userIDCacheMu.Lock()
+	userIDCache[cacheKey] = userIDCacheEntry{
+		value:  expiredID,
+		expire: time.Now().Add(-time.Minute),
+	}
+	userIDCacheMu.Unlock()
+
+	newID := cachedUserID("api-key-expired")
+	if newID == expiredID {
+		t.Fatalf("expected expired user_id to be replaced, got %q", newID)
+	}
+	if newID == "" {
+		t.Fatal("expected regenerated user_id to be non-empty")
+	}
+}
+
+func TestCachedUserID_IsScopedByAPIKey(t *testing.T) {
+	resetUserIDCache()
+
+	first := cachedUserID("api-key-1")
+	second := cachedUserID("api-key-2")
+
+	if first == second {
+		t.Fatalf("expected different API keys to have different user_ids, got %q", first)
+	}
+}
+
+func TestCachedUserID_RenewsTTLOnHit(t *testing.T) {
+	resetUserIDCache()
+
+	key := "api-key-renew"
+	id := cachedUserID(key)
+	cacheKey := userIDCacheKey(key)
+
+	soon := time.Now()
+	userIDCacheMu.Lock()
+	userIDCache[cacheKey] = userIDCacheEntry{
+		value:  id,
+		expire: soon.Add(2 * time.Second),
+	}
+	userIDCacheMu.Unlock()
+
+	if refreshed := cachedUserID(key); refreshed != id {
+		t.Fatalf("expected cached user_id to be reused before expiry, got %q", refreshed)
+	}
+
+	userIDCacheMu.RLock()
+	entry := userIDCache[cacheKey]
+	userIDCacheMu.RUnlock()
+
+	if entry.expire.Sub(soon) < 30*time.Minute {
+		t.Fatalf("expected TTL to renew, got %v remaining", entry.expire.Sub(soon))
+	}
+}