feat(translator/antigravity/claude): support interleaved thinking, signature restoration and system hint injection

internal/translator/antigravity/claude/antigravity_claude_request.go

@@ -7,8 +7,11 @@ package claude
 
 import (
 	"bytes"
+	"crypto/sha256"
+	"encoding/hex"
 	"strings"
 
+	"github.com/router-for-me/CLIProxyAPI/v6/internal/cache"
 	"github.com/router-for-me/CLIProxyAPI/v6/internal/translator/gemini/common"
 	"github.com/router-for-me/CLIProxyAPI/v6/internal/util"
 	"github.com/tidwall/gjson"
@@ -17,6 +20,29 @@ import (
 
 const geminiCLIClaudeThoughtSignature = "skip_thought_signature_validator"
 
+// deriveSessionID generates a stable session ID from the request.
+// Uses the hash of the first user message to identify the conversation.
+func deriveSessionID(rawJSON []byte) string {
+	messages := gjson.GetBytes(rawJSON, "messages")
+	if !messages.IsArray() {
+		return ""
+	}
+	for _, msg := range messages.Array() {
+		if msg.Get("role").String() == "user" {
+			content := msg.Get("content").String()
+			if content == "" {
+				// Try to get text from content array
+				content = msg.Get("content.0.text").String()
+			}
+			if content != "" {
+				h := sha256.Sum256([]byte(content))
+				return hex.EncodeToString(h[:16])
+			}
+		}
+	}
+	return ""
+}
+
 // ConvertClaudeRequestToAntigravity parses and transforms a Claude Code API request into Gemini CLI API format.
 // It extracts the model name, system instruction, message contents, and tool declarations
 // from the raw JSON request and returns them in the format expected by the Gemini CLI API.
@@ -37,7 +63,9 @@ const geminiCLIClaudeThoughtSignature = "skip_thought_signature_validator"
 //   - []byte: The transformed request data in Gemini CLI API format
 func ConvertClaudeRequestToAntigravity(modelName string, inputRawJSON []byte, _ bool) []byte {
 	rawJSON := bytes.Clone(inputRawJSON)
-	rawJSON = bytes.Replace(rawJSON, []byte(`"url":{"type":"string","format":"uri",`), []byte(`"url":{"type":"string",`), -1)
+
+	// Derive session ID for signature caching
+	sessionID := deriveSessionID(rawJSON)
 
 	// system instruction
 	systemInstructionJSON := ""
@@ -67,13 +95,15 @@ func ConvertClaudeRequestToAntigravity(modelName string, inputRawJSON []byte, _
 	messagesResult := gjson.GetBytes(rawJSON, "messages")
 	if messagesResult.IsArray() {
 		messageResults := messagesResult.Array()
-		for i := 0; i < len(messageResults); i++ {
+		numMessages := len(messageResults)
+		for i := 0; i < numMessages; i++ {
 			messageResult := messageResults[i]
 			roleResult := messageResult.Get("role")
 			if roleResult.Type != gjson.String {
 				continue
 			}
-			role := roleResult.String()
+			originalRole := roleResult.String()
+			role := originalRole
 			if role == "assistant" {
 				role = "model"
 			}
@@ -82,20 +112,47 @@ func ConvertClaudeRequestToAntigravity(modelName string, inputRawJSON []byte, _
 			contentsResult := messageResult.Get("content")
 			if contentsResult.IsArray() {
 				contentResults := contentsResult.Array()
-				for j := 0; j < len(contentResults); j++ {
+				numContents := len(contentResults)
+				for j := 0; j < numContents; j++ {
 					contentResult := contentResults[j]
 					contentTypeResult := contentResult.Get("type")
 					if contentTypeResult.Type == gjson.String && contentTypeResult.String() == "thinking" {
-						prompt := contentResult.Get("thinking").String()
+						thinkingText := contentResult.Get("thinking").String()
 						signatureResult := contentResult.Get("signature")
-						signature := geminiCLIClaudeThoughtSignature
+						signature := ""
-						if signatureResult.Exists() {
+						if signatureResult.Exists() && signatureResult.String() != "" {
 							signature = signatureResult.String()
 						}
+
+						// P3: Try to restore signature from cache for unsigned thinking blocks
+						if !cache.HasValidSignature(signature) && sessionID != "" && thinkingText != "" {
+							if cachedSig := cache.GetCachedSignature(sessionID, thinkingText); cachedSig != "" {
+								signature = cachedSig
+								log.Debugf("Restored cached signature for thinking block")
+							}
+						}
+
+						// P2-A: Skip trailing unsigned thinking blocks on last assistant message
+						isLastMessage := (i == numMessages-1)
+						isLastContent := (j == numContents-1)
+						isAssistant := (originalRole == "assistant")
+						isUnsigned := !cache.HasValidSignature(signature)
+
+						if isLastMessage && isLastContent && isAssistant && isUnsigned {
+							// Skip this trailing unsigned thinking block
+							continue
+						}
+
+						// Apply sentinel for unsigned thinking blocks that are not trailing
+						// (includes empty string and short/invalid signatures < 50 chars)
+						if isUnsigned {
+							signature = geminiCLIClaudeThoughtSignature
+						}
+
 						partJSON := `{}`
 						partJSON, _ = sjson.Set(partJSON, "thought", true)
-						if prompt != "" {
+						if thinkingText != "" {
-							partJSON, _ = sjson.Set(partJSON, "text", prompt)
+							partJSON, _ = sjson.Set(partJSON, "text", thinkingText)
 						}
 						if signature != "" {
 							partJSON, _ = sjson.Set(partJSON, "thoughtSignature", signature)

internal/translator/antigravity/claude/antigravity_claude_request_test.go

@@ -0,0 +1,567 @@
+package claude
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/tidwall/gjson"
+)
+
+func TestConvertClaudeRequestToAntigravity_BasicStructure(t *testing.T) {
+	inputJSON := []byte(`{
+		"model": "claude-3-5-sonnet-20240620",
+		"messages": [
+			{
+				"role": "user",
+				"content": [
+					{"type": "text", "text": "Hello"}
+				]
+			}
+		],
+		"system": [
+			{"type": "text", "text": "You are helpful"}
+		]
+	}`)
+
+	output := ConvertClaudeRequestToAntigravity("claude-sonnet-4-5", inputJSON, false)
+	outputStr := string(output)
+
+	// Check model
+	if gjson.Get(outputStr, "model").String() != "claude-sonnet-4-5" {
+		t.Errorf("Expected model 'claude-sonnet-4-5', got '%s'", gjson.Get(outputStr, "model").String())
+	}
+
+	// Check contents exist
+	contents := gjson.Get(outputStr, "request.contents")
+	if !contents.Exists() || !contents.IsArray() {
+		t.Error("request.contents should exist and be an array")
+	}
+
+	// Check role mapping (assistant -> model)
+	firstContent := gjson.Get(outputStr, "request.contents.0")
+	if firstContent.Get("role").String() != "user" {
+		t.Errorf("Expected role 'user', got '%s'", firstContent.Get("role").String())
+	}
+
+	// Check systemInstruction
+	sysInstruction := gjson.Get(outputStr, "request.systemInstruction")
+	if !sysInstruction.Exists() {
+		t.Error("systemInstruction should exist")
+	}
+	if sysInstruction.Get("parts.0.text").String() != "You are helpful" {
+		t.Error("systemInstruction text mismatch")
+	}
+}
+
+func TestConvertClaudeRequestToAntigravity_RoleMapping(t *testing.T) {
+	inputJSON := []byte(`{
+		"model": "claude-3-5-sonnet-20240620",
+		"messages": [
+			{"role": "user", "content": [{"type": "text", "text": "Hi"}]},
+			{"role": "assistant", "content": [{"type": "text", "text": "Hello"}]}
+		]
+	}`)
+
+	output := ConvertClaudeRequestToAntigravity("claude-sonnet-4-5", inputJSON, false)
+	outputStr := string(output)
+
+	// assistant should be mapped to model
+	secondContent := gjson.Get(outputStr, "request.contents.1")
+	if secondContent.Get("role").String() != "model" {
+		t.Errorf("Expected role 'model' (mapped from 'assistant'), got '%s'", secondContent.Get("role").String())
+	}
+}
+
+func TestConvertClaudeRequestToAntigravity_ThinkingBlocks(t *testing.T) {
+	// Valid signature must be at least 50 characters
+	validSignature := "abc123validSignature1234567890123456789012345678901234567890"
+	inputJSON := []byte(`{
+		"model": "claude-sonnet-4-5-thinking",
+		"messages": [
+			{
+				"role": "assistant",
+				"content": [
+					{"type": "thinking", "thinking": "Let me think...", "signature": "` + validSignature + `"},
+					{"type": "text", "text": "Answer"}
+				]
+			}
+		]
+	}`)
+
+	output := ConvertClaudeRequestToAntigravity("claude-sonnet-4-5-thinking", inputJSON, false)
+	outputStr := string(output)
+
+	// Check thinking block conversion
+	firstPart := gjson.Get(outputStr, "request.contents.0.parts.0")
+	if !firstPart.Get("thought").Bool() {
+		t.Error("thinking block should have thought: true")
+	}
+	if firstPart.Get("text").String() != "Let me think..." {
+		t.Error("thinking text mismatch")
+	}
+	if firstPart.Get("thoughtSignature").String() != validSignature {
+		t.Errorf("Expected thoughtSignature '%s', got '%s'", validSignature, firstPart.Get("thoughtSignature").String())
+	}
+}
+
+func TestConvertClaudeRequestToAntigravity_ThinkingBlockWithoutSignature(t *testing.T) {
+	inputJSON := []byte(`{
+		"model": "claude-sonnet-4-5-thinking",
+		"messages": [
+			{
+				"role": "assistant",
+				"content": [
+					{"type": "thinking", "thinking": "Let me think..."},
+					{"type": "text", "text": "Answer"}
+				]
+			}
+		]
+	}`)
+
+	output := ConvertClaudeRequestToAntigravity("claude-sonnet-4-5-thinking", inputJSON, false)
+	outputStr := string(output)
+
+	// Without signature, should use sentinel value
+	firstPart := gjson.Get(outputStr, "request.contents.0.parts.0")
+	if firstPart.Get("thoughtSignature").String() != geminiCLIClaudeThoughtSignature {
+		t.Errorf("Expected sentinel signature '%s', got '%s'",
+			geminiCLIClaudeThoughtSignature, firstPart.Get("thoughtSignature").String())
+	}
+}
+
+func TestConvertClaudeRequestToAntigravity_ToolDeclarations(t *testing.T) {
+	inputJSON := []byte(`{
+		"model": "claude-3-5-sonnet-20240620",
+		"messages": [],
+		"tools": [
+			{
+				"name": "test_tool",
+				"description": "A test tool",
+				"input_schema": {
+					"type": "object",
+					"properties": {
+						"name": {"type": "string"}
+					},
+					"required": ["name"]
+				}
+			}
+		]
+	}`)
+
+	output := ConvertClaudeRequestToAntigravity("gemini-1.5-pro", inputJSON, false)
+	outputStr := string(output)
+
+	// Check tools structure
+	tools := gjson.Get(outputStr, "request.tools")
+	if !tools.Exists() {
+		t.Error("Tools should exist in output")
+	}
+
+	funcDecl := gjson.Get(outputStr, "request.tools.0.functionDeclarations.0")
+	if funcDecl.Get("name").String() != "test_tool" {
+		t.Errorf("Expected tool name 'test_tool', got '%s'", funcDecl.Get("name").String())
+	}
+
+	// Check input_schema renamed to parametersJsonSchema
+	if funcDecl.Get("parametersJsonSchema").Exists() {
+		t.Log("parametersJsonSchema exists (expected)")
+	}
+	if funcDecl.Get("input_schema").Exists() {
+		t.Error("input_schema should be removed")
+	}
+}
+
+func TestConvertClaudeRequestToAntigravity_ToolUse(t *testing.T) {
+	inputJSON := []byte(`{
+		"model": "claude-3-5-sonnet-20240620",
+		"messages": [
+			{
+				"role": "assistant",
+				"content": [
+					{
+						"type": "tool_use",
+						"id": "call_123",
+						"name": "get_weather",
+						"input": "{\"location\": \"Paris\"}"
+					}
+				]
+			}
+		]
+	}`)
+
+	output := ConvertClaudeRequestToAntigravity("claude-sonnet-4-5", inputJSON, false)
+	outputStr := string(output)
+
+	// Check function call conversion
+	funcCall := gjson.Get(outputStr, "request.contents.0.parts.0.functionCall")
+	if !funcCall.Exists() {
+		t.Error("functionCall should exist")
+	}
+	if funcCall.Get("name").String() != "get_weather" {
+		t.Errorf("Expected function name 'get_weather', got '%s'", funcCall.Get("name").String())
+	}
+	if funcCall.Get("id").String() != "call_123" {
+		t.Errorf("Expected function id 'call_123', got '%s'", funcCall.Get("id").String())
+	}
+}
+
+func TestConvertClaudeRequestToAntigravity_ToolResult(t *testing.T) {
+	inputJSON := []byte(`{
+		"model": "claude-3-5-sonnet-20240620",
+		"messages": [
+			{
+				"role": "user",
+				"content": [
+					{
+						"type": "tool_result",
+						"tool_use_id": "get_weather-call-123",
+						"content": "22C sunny"
+					}
+				]
+			}
+		]
+	}`)
+
+	output := ConvertClaudeRequestToAntigravity("claude-sonnet-4-5", inputJSON, false)
+	outputStr := string(output)
+
+	// Check function response conversion
+	funcResp := gjson.Get(outputStr, "request.contents.0.parts.0.functionResponse")
+	if !funcResp.Exists() {
+		t.Error("functionResponse should exist")
+	}
+	if funcResp.Get("id").String() != "get_weather-call-123" {
+		t.Errorf("Expected function id, got '%s'", funcResp.Get("id").String())
+	}
+}
+
+func TestConvertClaudeRequestToAntigravity_ThinkingConfig(t *testing.T) {
+	// Note: This test requires the model to be registered in the registry
+	// with Thinking metadata. If the registry is not populated in test environment,
+	// thinkingConfig won't be added. We'll test the basic structure only.
+	inputJSON := []byte(`{
+		"model": "claude-sonnet-4-5-thinking",
+		"messages": [],
+		"thinking": {
+			"type": "enabled",
+			"budget_tokens": 8000
+		}
+	}`)
+
+	output := ConvertClaudeRequestToAntigravity("claude-sonnet-4-5-thinking", inputJSON, false)
+	outputStr := string(output)
+
+	// Check thinking config conversion (only if model supports thinking in registry)
+	thinkingConfig := gjson.Get(outputStr, "request.generationConfig.thinkingConfig")
+	if thinkingConfig.Exists() {
+		if thinkingConfig.Get("thinkingBudget").Int() != 8000 {
+			t.Errorf("Expected thinkingBudget 8000, got %d", thinkingConfig.Get("thinkingBudget").Int())
+		}
+		if !thinkingConfig.Get("include_thoughts").Bool() {
+			t.Error("include_thoughts should be true")
+		}
+	} else {
+		t.Log("thinkingConfig not present - model may not be registered in test registry")
+	}
+}
+
+func TestConvertClaudeRequestToAntigravity_ImageContent(t *testing.T) {
+	inputJSON := []byte(`{
+		"model": "claude-3-5-sonnet-20240620",
+		"messages": [
+			{
+				"role": "user",
+				"content": [
+					{
+						"type": "image",
+						"source": {
+							"type": "base64",
+							"media_type": "image/png",
+							"data": "iVBORw0KGgoAAAANSUhEUg=="
+						}
+					}
+				]
+			}
+		]
+	}`)
+
+	output := ConvertClaudeRequestToAntigravity("claude-sonnet-4-5", inputJSON, false)
+	outputStr := string(output)
+
+	// Check inline data conversion
+	inlineData := gjson.Get(outputStr, "request.contents.0.parts.0.inlineData")
+	if !inlineData.Exists() {
+		t.Error("inlineData should exist")
+	}
+	if inlineData.Get("mime_type").String() != "image/png" {
+		t.Error("mime_type mismatch")
+	}
+	if !strings.Contains(inlineData.Get("data").String(), "iVBORw0KGgo") {
+		t.Error("data mismatch")
+	}
+}
+
+func TestConvertClaudeRequestToAntigravity_GenerationConfig(t *testing.T) {
+	inputJSON := []byte(`{
+		"model": "claude-3-5-sonnet-20240620",
+		"messages": [],
+		"temperature": 0.7,
+		"top_p": 0.9,
+		"top_k": 40,
+		"max_tokens": 2000
+	}`)
+
+	output := ConvertClaudeRequestToAntigravity("claude-sonnet-4-5", inputJSON, false)
+	outputStr := string(output)
+
+	genConfig := gjson.Get(outputStr, "request.generationConfig")
+	if genConfig.Get("temperature").Float() != 0.7 {
+		t.Errorf("Expected temperature 0.7, got %f", genConfig.Get("temperature").Float())
+	}
+	if genConfig.Get("topP").Float() != 0.9 {
+		t.Errorf("Expected topP 0.9, got %f", genConfig.Get("topP").Float())
+	}
+	if genConfig.Get("topK").Float() != 40 {
+		t.Errorf("Expected topK 40, got %f", genConfig.Get("topK").Float())
+	}
+	if genConfig.Get("maxOutputTokens").Float() != 2000 {
+		t.Errorf("Expected maxOutputTokens 2000, got %f", genConfig.Get("maxOutputTokens").Float())
+	}
+}
+
+// ============================================================================
+// P2-A: Trailing Unsigned Thinking Block Removal
+// ============================================================================
+
+func TestConvertClaudeRequestToAntigravity_TrailingUnsignedThinking_Removed(t *testing.T) {
+	// Last assistant message ends with unsigned thinking block - should be removed
+	inputJSON := []byte(`{
+		"model": "claude-sonnet-4-5-thinking",
+		"messages": [
+			{
+				"role": "user",
+				"content": [{"type": "text", "text": "Hello"}]
+			},
+			{
+				"role": "assistant",
+				"content": [
+					{"type": "text", "text": "Here is my answer"},
+					{"type": "thinking", "thinking": "I should think more..."}
+				]
+			}
+		]
+	}`)
+
+	output := ConvertClaudeRequestToAntigravity("claude-sonnet-4-5-thinking", inputJSON, false)
+	outputStr := string(output)
+
+	// The last part of the last assistant message should NOT be a thinking block
+	lastMessageParts := gjson.Get(outputStr, "request.contents.1.parts")
+	if !lastMessageParts.IsArray() {
+		t.Fatal("Last message should have parts array")
+	}
+	parts := lastMessageParts.Array()
+	if len(parts) == 0 {
+		t.Fatal("Last message should have at least one part")
+	}
+
+	// The unsigned thinking should be removed, leaving only the text
+	lastPart := parts[len(parts)-1]
+	if lastPart.Get("thought").Bool() {
+		t.Error("Trailing unsigned thinking block should be removed")
+	}
+}
+
+func TestConvertClaudeRequestToAntigravity_TrailingSignedThinking_Kept(t *testing.T) {
+	// Last assistant message ends with signed thinking block - should be kept
+	inputJSON := []byte(`{
+		"model": "claude-sonnet-4-5-thinking",
+		"messages": [
+			{
+				"role": "user",
+				"content": [{"type": "text", "text": "Hello"}]
+			},
+			{
+				"role": "assistant",
+				"content": [
+					{"type": "text", "text": "Here is my answer"},
+					{"type": "thinking", "thinking": "Valid thinking...", "signature": "abc123validSignature1234567890123456789012345678901234567890"}
+				]
+			}
+		]
+	}`)
+
+	output := ConvertClaudeRequestToAntigravity("claude-sonnet-4-5-thinking", inputJSON, false)
+	outputStr := string(output)
+
+	// The signed thinking block should be preserved
+	lastMessageParts := gjson.Get(outputStr, "request.contents.1.parts")
+	parts := lastMessageParts.Array()
+	if len(parts) < 2 {
+		t.Error("Signed thinking block should be preserved")
+	}
+}
+
+func TestConvertClaudeRequestToAntigravity_MiddleUnsignedThinking_SentinelApplied(t *testing.T) {
+	// Middle message has unsigned thinking - should use sentinel (existing behavior)
+	inputJSON := []byte(`{
+		"model": "claude-sonnet-4-5-thinking",
+		"messages": [
+			{
+				"role": "assistant",
+				"content": [
+					{"type": "thinking", "thinking": "Middle thinking..."},
+					{"type": "text", "text": "Answer"}
+				]
+			},
+			{
+				"role": "user",
+				"content": [{"type": "text", "text": "Follow up"}]
+			}
+		]
+	}`)
+
+	output := ConvertClaudeRequestToAntigravity("claude-sonnet-4-5-thinking", inputJSON, false)
+	outputStr := string(output)
+
+	// Middle unsigned thinking should have sentinel applied
+	thinkingPart := gjson.Get(outputStr, "request.contents.0.parts.0")
+	if !thinkingPart.Get("thought").Bool() {
+		t.Error("Middle thinking block should be preserved with sentinel")
+	}
+	if thinkingPart.Get("thoughtSignature").String() != geminiCLIClaudeThoughtSignature {
+		t.Errorf("Middle unsigned thinking should use sentinel signature, got: %s", thinkingPart.Get("thoughtSignature").String())
+	}
+}
+
+// ============================================================================
+// P2-B: Tool + Thinking System Hint Injection
+// ============================================================================
+
+func TestConvertClaudeRequestToAntigravity_ToolAndThinking_HintInjected(t *testing.T) {
+	// When both tools and thinking are enabled, hint should be injected into system instruction
+	inputJSON := []byte(`{
+		"model": "claude-sonnet-4-5-thinking",
+		"messages": [{"role": "user", "content": [{"type": "text", "text": "Hello"}]}],
+		"system": [{"type": "text", "text": "You are helpful."}],
+		"tools": [
+			{
+				"name": "get_weather",
+				"description": "Get weather",
+				"input_schema": {"type": "object", "properties": {"location": {"type": "string"}}}
+			}
+		],
+		"thinking": {"type": "enabled", "budget_tokens": 8000}
+	}`)
+
+	output := ConvertClaudeRequestToAntigravity("claude-sonnet-4-5-thinking", inputJSON, false)
+	outputStr := string(output)
+
+	// System instruction should contain the interleaved thinking hint
+	sysInstruction := gjson.Get(outputStr, "request.systemInstruction")
+	if !sysInstruction.Exists() {
+		t.Fatal("systemInstruction should exist")
+	}
+
+	// Check if hint is appended
+	sysText := sysInstruction.Get("parts").Array()
+	found := false
+	for _, part := range sysText {
+		if strings.Contains(part.Get("text").String(), "Interleaved thinking is enabled") {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Errorf("Interleaved thinking hint should be injected when tools and thinking are both active, got: %v", sysInstruction.Raw)
+	}
+}
+
+func TestConvertClaudeRequestToAntigravity_ToolsOnly_NoHint(t *testing.T) {
+	// When only tools are present (no thinking), hint should NOT be injected
+	inputJSON := []byte(`{
+		"model": "claude-sonnet-4-5",
+		"messages": [{"role": "user", "content": [{"type": "text", "text": "Hello"}]}],
+		"system": [{"type": "text", "text": "You are helpful."}],
+		"tools": [
+			{
+				"name": "get_weather",
+				"description": "Get weather",
+				"input_schema": {"type": "object", "properties": {"location": {"type": "string"}}}
+			}
+		]
+	}`)
+
+	output := ConvertClaudeRequestToAntigravity("claude-sonnet-4-5", inputJSON, false)
+	outputStr := string(output)
+
+	// System instruction should NOT contain the hint
+	sysInstruction := gjson.Get(outputStr, "request.systemInstruction")
+	if sysInstruction.Exists() {
+		for _, part := range sysInstruction.Get("parts").Array() {
+			if strings.Contains(part.Get("text").String(), "Interleaved thinking is enabled") {
+				t.Error("Hint should NOT be injected when only tools are present (no thinking)")
+			}
+		}
+	}
+}
+
+func TestConvertClaudeRequestToAntigravity_ThinkingOnly_NoHint(t *testing.T) {
+	// When only thinking is enabled (no tools), hint should NOT be injected
+	inputJSON := []byte(`{
+		"model": "claude-sonnet-4-5-thinking",
+		"messages": [{"role": "user", "content": [{"type": "text", "text": "Hello"}]}],
+		"system": [{"type": "text", "text": "You are helpful."}],
+		"thinking": {"type": "enabled", "budget_tokens": 8000}
+	}`)
+
+	output := ConvertClaudeRequestToAntigravity("claude-sonnet-4-5-thinking", inputJSON, false)
+	outputStr := string(output)
+
+	// System instruction should NOT contain the hint (no tools)
+	sysInstruction := gjson.Get(outputStr, "request.systemInstruction")
+	if sysInstruction.Exists() {
+		for _, part := range sysInstruction.Get("parts").Array() {
+			if strings.Contains(part.Get("text").String(), "Interleaved thinking is enabled") {
+				t.Error("Hint should NOT be injected when only thinking is present (no tools)")
+			}
+		}
+	}
+}
+
+func TestConvertClaudeRequestToAntigravity_ToolAndThinking_NoExistingSystem(t *testing.T) {
+	// When tools + thinking but no system instruction, should create one with hint
+	inputJSON := []byte(`{
+		"model": "claude-sonnet-4-5-thinking",
+		"messages": [{"role": "user", "content": [{"type": "text", "text": "Hello"}]}],
+		"tools": [
+			{
+				"name": "get_weather",
+				"description": "Get weather",
+				"input_schema": {"type": "object", "properties": {"location": {"type": "string"}}}
+			}
+		],
+		"thinking": {"type": "enabled", "budget_tokens": 8000}
+	}`)
+
+	output := ConvertClaudeRequestToAntigravity("claude-sonnet-4-5-thinking", inputJSON, false)
+	outputStr := string(output)
+
+	// System instruction should be created with hint
+	sysInstruction := gjson.Get(outputStr, "request.systemInstruction")
+	if !sysInstruction.Exists() {
+		t.Fatal("systemInstruction should be created when tools + thinking are active")
+	}
+
+	sysText := sysInstruction.Get("parts").Array()
+	found := false
+	for _, part := range sysText {
+		if strings.Contains(part.Get("text").String(), "Interleaved thinking is enabled") {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Errorf("Interleaved thinking hint should be in created systemInstruction, got: %v", sysInstruction.Raw)
+	}
+}