refactor(cache, translator): refine signature caching logic and tests, replace session-based logic with model group handling

internal/cache/signature_cache.go

@@ -3,7 +3,6 @@ package cache
 import (
 	"crypto/sha256"
 	"encoding/hex"
-	"fmt"
 	"strings"
 	"sync"
 	"time"
@@ -25,18 +24,18 @@ const (
 	// MinValidSignatureLen is the minimum length for a signature to be considered valid
 	MinValidSignatureLen = 50
 
-	// SessionCleanupInterval controls how often stale sessions are purged
-	SessionCleanupInterval = 10 * time.Minute
+	// CacheCleanupInterval controls how often stale entries are purged
+	CacheCleanupInterval = 10 * time.Minute
 )
 
-// signatureCache stores signatures by sessionId -> textHash -> SignatureEntry
+// signatureCache stores signatures by model group -> textHash -> SignatureEntry
 var signatureCache sync.Map
 
-// sessionCleanupOnce ensures the background cleanup goroutine starts only once
-var sessionCleanupOnce sync.Once
+// cacheCleanupOnce ensures the background cleanup goroutine starts only once
+var cacheCleanupOnce sync.Once
 
-// sessionCache is the inner map type
-type sessionCache struct {
+// groupCache is the inner map type
+type groupCache struct {
 	mu      sync.RWMutex
 	entries map[string]SignatureEntry
 }
@@ -47,36 +46,36 @@ func hashText(text string) string {
 	return hex.EncodeToString(h[:])[:SignatureTextHashLen]
 }
 
-// getOrCreateSession gets or creates a session cache
-func getOrCreateSession(sessionID string) *sessionCache {
+// getOrCreateGroupCache gets or creates a cache bucket for a model group
+func getOrCreateGroupCache(groupKey string) *groupCache {
 	// Start background cleanup on first access
-	sessionCleanupOnce.Do(startSessionCleanup)
+	cacheCleanupOnce.Do(startCacheCleanup)
 
-	if val, ok := signatureCache.Load(sessionID); ok {
-		return val.(*sessionCache)
+	if val, ok := signatureCache.Load(groupKey); ok {
+		return val.(*groupCache)
 	}
-	sc := &sessionCache{entries: make(map[string]SignatureEntry)}
-	actual, _ := signatureCache.LoadOrStore(sessionID, sc)
-	return actual.(*sessionCache)
+	sc := &groupCache{entries: make(map[string]SignatureEntry)}
+	actual, _ := signatureCache.LoadOrStore(groupKey, sc)
+	return actual.(*groupCache)
 }
 
-// startSessionCleanup launches a background goroutine that periodically
-// removes sessions where all entries have expired.
-func startSessionCleanup() {
+// startCacheCleanup launches a background goroutine that periodically
+// removes caches where all entries have expired.
+func startCacheCleanup() {
 	go func() {
-		ticker := time.NewTicker(SessionCleanupInterval)
+		ticker := time.NewTicker(CacheCleanupInterval)
 		defer ticker.Stop()
 		for range ticker.C {
-			purgeExpiredSessions()
+			purgeExpiredCaches()
 		}
 	}()
 }
 
-// purgeExpiredSessions removes sessions with no valid (non-expired) entries.
-func purgeExpiredSessions() {
+// purgeExpiredCaches removes caches with no valid (non-expired) entries.
+func purgeExpiredCaches() {
 	now := time.Now()
 	signatureCache.Range(func(key, value any) bool {
-		sc := value.(*sessionCache)
+		sc := value.(*groupCache)
 		sc.mu.Lock()
 		// Remove expired entries
 		for k, entry := range sc.entries {
@@ -86,7 +85,7 @@ func purgeExpiredSessions() {
 		}
 		isEmpty := len(sc.entries) == 0
 		sc.mu.Unlock()
-		// Remove session if empty
+		// Remove cache bucket if empty
 		if isEmpty {
 			signatureCache.Delete(key)
 		}
@@ -94,7 +93,7 @@ func purgeExpiredSessions() {
 	})
 }
 
-// CacheSignature stores a thinking signature for a given session and text.
+// CacheSignature stores a thinking signature for a given model group and text.
 // Used for Claude models that require signed thinking blocks in multi-turn conversations.
 func CacheSignature(modelName, text, signature string) {
 	if text == "" || signature == "" {
@@ -104,9 +103,9 @@ func CacheSignature(modelName, text, signature string) {
 		return
 	}
 
-	text = fmt.Sprintf("%s#%s", GetModelGroup(modelName), text)
+	groupKey := GetModelGroup(modelName)
 	textHash := hashText(text)
-	sc := getOrCreateSession(textHash)
+	sc := getOrCreateGroupCache(groupKey)
 	sc.mu.Lock()
 	defer sc.mu.Unlock()
 
@@ -116,26 +115,25 @@ func CacheSignature(modelName, text, signature string) {
 	}
 }
 
-// GetCachedSignature retrieves a cached signature for a given session and text.
+// GetCachedSignature retrieves a cached signature for a given model group and text.
 // Returns empty string if not found or expired.
 func GetCachedSignature(modelName, text string) string {
-	family := GetModelGroup(modelName)
+	groupKey := GetModelGroup(modelName)
 
 	if text == "" {
-		if family == "gemini" {
+		if groupKey == "gemini" {
 			return "skip_thought_signature_validator"
 		}
 		return ""
 	}
-	text = fmt.Sprintf("%s#%s", GetModelGroup(modelName), text)
-	val, ok := signatureCache.Load(hashText(text))
+	val, ok := signatureCache.Load(groupKey)
 	if !ok {
-		if family == "gemini" {
+		if groupKey == "gemini" {
 			return "skip_thought_signature_validator"
 		}
 		return ""
 	}
-	sc := val.(*sessionCache)
+	sc := val.(*groupCache)
 
 	textHash := hashText(text)
 
@@ -145,7 +143,7 @@ func GetCachedSignature(modelName, text string) string {
 	entry, exists := sc.entries[textHash]
 	if !exists {
 		sc.mu.Unlock()
-		if family == "gemini" {
+		if groupKey == "gemini" {
 			return "skip_thought_signature_validator"
 		}
 		return ""
@@ -153,7 +151,7 @@ func GetCachedSignature(modelName, text string) string {
 	if now.Sub(entry.Timestamp) > SignatureCacheTTL {
 		delete(sc.entries, textHash)
 		sc.mu.Unlock()
-		if family == "gemini" {
+		if groupKey == "gemini" {
 			return "skip_thought_signature_validator"
 		}
 		return ""
@@ -167,22 +165,17 @@ func GetCachedSignature(modelName, text string) string {
 	return entry.Signature
 }
 
-// ClearSignatureCache clears signature cache for a specific session or all sessions.
-func ClearSignatureCache(sessionID string) {
-	if sessionID != "" {
-		signatureCache.Range(func(key, _ any) bool {
-			kStr, ok := key.(string)
-			if ok && strings.HasSuffix(kStr, "#"+sessionID) {
-				signatureCache.Delete(key)
-			}
-			return true
-		})
-	} else {
+// ClearSignatureCache clears signature cache for a specific model group or all groups.
+func ClearSignatureCache(modelName string) {
+	if modelName == "" {
 		signatureCache.Range(func(key, _ any) bool {
 			signatureCache.Delete(key)
 			return true
 		})
+		return
 	}
+	groupKey := GetModelGroup(modelName)
+	signatureCache.Delete(groupKey)
 }
 
 // HasValidSignature checks if a signature is valid (non-empty and long enough)

internal/cache/signature_cache_test.go

@@ -21,33 +21,33 @@ func TestCacheSignature_BasicStorageAndRetrieval(t *testing.T) {
 	}
 }
 
-func TestCacheSignature_DifferentSessions(t *testing.T) {
+func TestCacheSignature_DifferentModelGroups(t *testing.T) {
 	ClearSignatureCache("")
 
-	text := "Same text in different sessions"
+	text := "Same text across models"
 	sig1 := "signature1_1234567890123456789012345678901234567890123456"
 	sig2 := "signature2_1234567890123456789012345678901234567890123456"
 
-	CacheSignature("test-model", text, sig1)
-	CacheSignature("test-model", text, sig2)
+	CacheSignature("claude-sonnet-4-5-thinking", text, sig1)
+	CacheSignature("gpt-4o", text, sig2)
 
-	if GetCachedSignature("test-model", text) != sig1 {
-		t.Error("Session-a signature mismatch")
+	if GetCachedSignature("claude-sonnet-4-5-thinking", text) != sig1 {
+		t.Error("Claude signature mismatch")
 	}
-	if GetCachedSignature("test-model", text) != sig2 {
-		t.Error("Session-b signature mismatch")
+	if GetCachedSignature("gpt-4o", text) != sig2 {
+		t.Error("GPT signature mismatch")
 	}
 }
 
 func TestCacheSignature_NotFound(t *testing.T) {
 	ClearSignatureCache("")
 
-	// Non-existent session
+	// Non-existent cache entry
 	if got := GetCachedSignature("test-model", "some text"); got != "" {
-		t.Errorf("Expected empty string for nonexistent session, got '%s'", got)
+		t.Errorf("Expected empty string for missing entry, got '%s'", got)
 	}
 
-	// Existing session but different text
+	// Existing cache but different text
 	CacheSignature("test-model", "text-a", "sigA12345678901234567890123456789012345678901234567890")
 	if got := GetCachedSignature("test-model", "text-b"); got != "" {
 		t.Errorf("Expected empty string for different text, got '%s'", got)
@@ -58,7 +58,6 @@ func TestCacheSignature_EmptyInputs(t *testing.T) {
 	ClearSignatureCache("")
 
 	// All empty/invalid inputs should be no-ops
-	CacheSignature("test-model", "text", "sig12345678901234567890123456789012345678901234567890")
 	CacheSignature("test-model", "", "sig12345678901234567890123456789012345678901234567890")
 	CacheSignature("test-model", "text", "")
 	CacheSignature("test-model", "text", "short") // Too short
@@ -81,20 +80,21 @@ func TestCacheSignature_ShortSignatureRejected(t *testing.T) {
 	}
 }
 
-func TestClearSignatureCache_SpecificSession(t *testing.T) {
+func TestClearSignatureCache_ModelGroup(t *testing.T) {
 	ClearSignatureCache("")
 
-	sig := "validSig1234567890123456789012345678901234567890123456"
-	CacheSignature("test-model", "text", sig)
-	CacheSignature("test-model", "text", sig)
+	sigClaude := "validSig1234567890123456789012345678901234567890123456"
+	sigGpt := "validSig9876543210987654321098765432109876543210987654"
+	CacheSignature("claude-sonnet-4-5-thinking", "text", sigClaude)
+	CacheSignature("gpt-4o", "text", sigGpt)
 
-	ClearSignatureCache("session-1")
+	ClearSignatureCache("claude-sonnet-4-5-thinking")
 
-	if got := GetCachedSignature("test-model", "text"); got != "" {
-		t.Error("session-1 should be cleared")
+	if got := GetCachedSignature("claude-sonnet-4-5-thinking", "text"); got != "" {
+		t.Error("Claude cache should be cleared")
 	}
-	if got := GetCachedSignature("test-model", "text"); got != sig {
-		t.Error("session-2 should still exist")
+	if got := GetCachedSignature("gpt-4o", "text"); got != sigGpt {
+		t.Error("GPT cache should still exist")
 	}
 }
 
@@ -108,10 +108,10 @@ func TestClearSignatureCache_AllSessions(t *testing.T) {
 	ClearSignatureCache("")
 
 	if got := GetCachedSignature("test-model", "text"); got != "" {
-		t.Error("session-1 should be cleared")
+		t.Error("cache should be cleared")
 	}
 	if got := GetCachedSignature("test-model", "text"); got != "" {
-		t.Error("session-2 should be cleared")
+		t.Error("cache should be cleared")
 	}
 }
 

internal/translator/antigravity/claude/antigravity_claude_request.go

@@ -98,9 +98,15 @@ func ConvertClaudeRequestToAntigravity(modelName string, inputRawJSON []byte, _
 						// Use GetThinkingText to handle wrapped thinking objects
 						thinkingText := thinking.GetThinkingText(contentResult)
 
-						// Always try cached signature first (more reliable than client-provided)
-						// Client may send stale or invalid signatures from different sessions
 						signature := ""
+						signatureResult := contentResult.Get("signature")
+						hasClientSignature := signatureResult.Exists() && signatureResult.String() != ""
+
+						// Only consider cached signatures when the client provided a signature.
+						// Unsigned thinking blocks must be dropped.
+						if hasClientSignature {
+							// Always try cached signature first (more reliable than client-provided)
+							// Client may send stale or invalid signatures from other requests
 							if thinkingText != "" {
 								if cachedSig := cache.GetCachedSignature(modelName, thinkingText); cachedSig != "" {
 									signature = cachedSig
@@ -110,7 +116,6 @@ func ConvertClaudeRequestToAntigravity(modelName string, inputRawJSON []byte, _
 
 							// Fallback to client signature only if cache miss and client signature is valid
 							if signature == "" {
-							signatureResult := contentResult.Get("signature")
 								clientSignature := ""
 								if signatureResult.Exists() && signatureResult.String() != "" {
 									arrayClientSignatures := strings.SplitN(signatureResult.String(), "#", 2)
@@ -125,6 +130,7 @@ func ConvertClaudeRequestToAntigravity(modelName string, inputRawJSON []byte, _
 								}
 								// log.Debugf("Using client-provided signature for thinking block")
 							}
+						}
 
 						// Store for subsequent tool_use in the same message
 						if cache.HasValidSignature(modelName, signature) {

internal/translator/antigravity/claude/antigravity_claude_request_test.go

@@ -78,9 +78,7 @@ func TestConvertClaudeRequestToAntigravity_ThinkingBlocks(t *testing.T) {
 	validSignature := "abc123validSignature1234567890123456789012345678901234567890"
 	thinkingText := "Let me think..."
 
-	// Pre-cache the signature (simulating a response from the same session)
-	// The session ID is derived from the first user message hash
-	// Since there's no user message in this test, we need to add one
+	// Pre-cache the signature (simulating a previous response for the same thinking text)
 	inputJSON := []byte(`{
 		"model": "claude-sonnet-4-5-thinking",
 		"messages": [

internal/translator/antigravity/claude/antigravity_claude_response.go

@@ -139,7 +139,7 @@ func ConvertAntigravityResponseToClaude(_ context.Context, _ string, originalReq
 
 						if params.CurrentThinkingText.Len() > 0 {
 							cache.CacheSignature(modelName, params.CurrentThinkingText.String(), thoughtSignature.String())
-							// log.Debugf("Cached signature for thinking block (sessionID=%s, textLen=%d)", params.SessionID, params.CurrentThinkingText.Len())
+							// log.Debugf("Cached signature for thinking block (textLen=%d)", params.CurrentThinkingText.Len())
 							params.CurrentThinkingText.Reset()
 						}
 

internal/translator/antigravity/claude/antigravity_claude_response_test.go

@@ -12,10 +12,10 @@ import (
 // Signature Caching Tests
 // ============================================================================
 
-func TestConvertAntigravityResponseToClaude_SessionIDDerived(t *testing.T) {
+func TestConvertAntigravityResponseToClaude_ParamsInitialized(t *testing.T) {
 	cache.ClearSignatureCache("")
 
-	// Request with user message - should derive session ID
+	// Request with user message - should initialize params
 	requestJSON := []byte(`{
 		"messages": [
 			{"role": "user", "content": [{"type": "text", "text": "Hello world"}]}
@@ -37,10 +37,12 @@ func TestConvertAntigravityResponseToClaude_SessionIDDerived(t *testing.T) {
 	ctx := context.Background()
 	ConvertAntigravityResponseToClaude(ctx, "claude-sonnet-4-5-thinking", requestJSON, requestJSON, responseJSON, &param)
 
-	// Verify session ID was set
 	params := param.(*Params)
-	if params.SessionID == "" {
-		t.Error("SessionID should be derived from request")
+	if !params.HasFirstResponse {
+		t.Error("HasFirstResponse should be set after first chunk")
+	}
+	if params.CurrentThinkingText.Len() == 0 {
+		t.Error("Thinking text should be accumulated")
 	}
 }
 
@@ -130,12 +132,8 @@ func TestConvertAntigravityResponseToClaude_SignatureCached(t *testing.T) {
 	// Process thinking chunk
 	ConvertAntigravityResponseToClaude(ctx, "claude-sonnet-4-5-thinking", requestJSON, requestJSON, thinkingChunk, &param)
 	params := param.(*Params)
-	sessionID := params.SessionID
 	thinkingText := params.CurrentThinkingText.String()
 
-	if sessionID == "" {
-		t.Fatal("SessionID should be set")
-	}
 	if thinkingText == "" {
 		t.Fatal("Thinking text should be accumulated")
 	}

internal/translator/antigravity/gemini/antigravity_gemini_request.go

@@ -99,36 +99,44 @@ func ConvertGeminiRequestToAntigravity(modelName string, inputRawJSON []byte, _
 	}
 
 	// Gemini-specific handling for non-Claude models:
+	// - Remove thinking parts entirely.
 	// - Add skip_thought_signature_validator to functionCall parts so upstream can bypass signature validation.
-	// - Also mark thinking parts with the same sentinel when present (we keep the parts; we only annotate them).
 	if !strings.Contains(modelName, "claude") {
 		const skipSentinel = "skip_thought_signature_validator"
 
 		gjson.GetBytes(rawJSON, "request.contents").ForEach(func(contentIdx, content gjson.Result) bool {
-			if content.Get("role").String() == "model" {
-				// First pass: collect indices of thinking parts to mark with skip sentinel
-				var thinkingIndicesToSkipSignature []int64
-				content.Get("parts").ForEach(func(partIdx, part gjson.Result) bool {
-					// Collect indices of thinking blocks to mark with skip sentinel
-					if part.Get("thought").Bool() {
-						thinkingIndicesToSkipSignature = append(thinkingIndicesToSkipSignature, partIdx.Int())
+			if content.Get("role").String() != "model" {
+				return true
 			}
-					// Add skip sentinel to functionCall parts
+			partsResult := content.Get("parts")
+			if !partsResult.IsArray() {
+				return true
+			}
+
+			parts := partsResult.Array()
+			newParts := make([]interface{}, 0, len(parts))
+			for _, part := range parts {
+				if part.Get("thought").Bool() {
+					continue
+				}
+
+				partRaw := part.Raw
 				if part.Get("functionCall").Exists() {
 					existingSig := part.Get("thoughtSignature").String()
 					if existingSig == "" || len(existingSig) < 50 {
-							rawJSON, _ = sjson.SetBytes(rawJSON, fmt.Sprintf("request.contents.%d.parts.%d.thoughtSignature", contentIdx.Int(), partIdx.Int()), skipSentinel)
+						updatedPart, errSet := sjson.Set(partRaw, "thoughtSignature", skipSentinel)
+						if errSet != nil {
+							log.WithError(errSet).Debug("failed to set thoughtSignature on functionCall part")
+						} else {
+							partRaw = updatedPart
+						}
 					}
 				}
-					return true
-				})
 
-				// Add skip_thought_signature_validator sentinel to thinking blocks in reverse order to preserve indices
-				for i := len(thinkingIndicesToSkipSignature) - 1; i >= 0; i-- {
-					idx := thinkingIndicesToSkipSignature[i]
-					rawJSON, _ = sjson.SetBytes(rawJSON, fmt.Sprintf("request.contents.%d.parts.%d.thoughtSignature", contentIdx.Int(), idx), skipSentinel)
-				}
+				newParts = append(newParts, gjson.Parse(partRaw).Value())
 			}
+
+			rawJSON, _ = sjson.SetBytes(rawJSON, fmt.Sprintf("request.contents.%d.parts", contentIdx.Int()), newParts)
 			return true
 		})
 	}