diff --git a/internal/cache/signature_cache.go b/internal/cache/signature_cache.go
index 477b1245..6ece41fa 100644
--- a/internal/cache/signature_cache.go
+++ b/internal/cache/signature_cache.go
@@ -156,7 +156,13 @@ func GetCachedSignature(modelName, sessionID, text string) string {
 // ClearSignatureCache clears signature cache for a specific session or all sessions.
 func ClearSignatureCache(sessionID string) {
 	if sessionID != "" {
-		signatureCache.Delete(sessionID)
+		signatureCache.Range(func(key, _ any) bool {
+			kStr, ok := key.(string)
+			if ok && strings.HasSuffix(kStr, "#"+sessionID) {
+				signatureCache.Delete(key)
+			}
+			return true
+		})
 	} else {
 		signatureCache.Range(func(key, _ any) bool {
 			signatureCache.Delete(key)
diff --git a/internal/translator/antigravity/claude/antigravity_claude_response_test.go b/internal/translator/antigravity/claude/antigravity_claude_response_test.go
index c749b259..ef6c0afe 100644
--- a/internal/translator/antigravity/claude/antigravity_claude_response_test.go
+++ b/internal/translator/antigravity/claude/antigravity_claude_response_test.go
@@ -97,6 +97,7 @@ func TestConvertAntigravityResponseToClaude_SignatureCached(t *testing.T) {
 	cache.ClearSignatureCache("")
 
 	requestJSON := []byte(`{
+		"model": "claude-sonnet-4-5-thinking",
 		"messages": [{"role": "user", "content": [{"type": "text", "text": "Cache test"}]}]
 	}`)
 
@@ -158,6 +159,7 @@ func TestConvertAntigravityResponseToClaude_MultipleThinkingBlocks(t *testing.T)
 	cache.ClearSignatureCache("")
 
 	requestJSON := []byte(`{
+		"model": "claude-sonnet-4-5-thinking",
 		"messages": [{"role": "user", "content": [{"type": "text", "text": "Multi block test"}]}]
 	}`)