diff --git a/backend/internal/service/openai_gateway_grok_chat_bridge.go b/backend/internal/service/openai_gateway_grok_chat_bridge.go
index 0b8f0e2d83..baf1d8a592 100644
--- a/backend/internal/service/openai_gateway_grok_chat_bridge.go
+++ b/backend/internal/service/openai_gateway_grok_chat_bridge.go
@@ -33,6 +33,7 @@ var grokChatResponsesBridgeTopLevelFields = map[string]struct{}{
 	"tool_choice":           {},
 	"functions":             {},
 	"function_call":         {},
+	"parallel_tool_calls":   {},
 }
 
 // grokChatResponsesBridgeEligibility deliberately accepts only request shapes
@@ -50,13 +51,22 @@ func grokChatResponsesBridgeEligibility(body []byte) (bool, string) {
 			return false, "unsupported_" + field
 		}
 	}
-	for _, field := range []string{"tools", "functions"} {
-		if raw, exists := root[field]; exists && !grokChatNullOrEmptyArray(raw) {
-			return false, "unsupported_" + field
+	if raw, exists := root["tools"]; exists {
+		if ok, reason := grokChatFunctionDeclarationsBridgeable(raw); !ok {
+			return false, reason
 		}
 	}
-	if raw, exists := root["tool_choice"]; exists && !grokChatNullOrNone(raw) {
-		return false, "unsupported_tool_choice"
+	if raw, exists := root["functions"]; exists && !grokChatNullOrEmptyArray(raw) {
+		return false, "unsupported_functions"
+	}
+	if raw, exists := root["tool_choice"]; exists {
+		if ok, reason := grokChatToolChoiceBridgeable(raw); !ok {
+			return false, reason
+		}
+		var choice string
+		if json.Unmarshal(raw, &choice) == nil && choice == "required" && !grokChatHasFunctionDeclarations(root) {
+			return false, "required_tool_choice_without_tools"
+		}
 	}
 	if raw, exists := root["function_call"]; exists && !grokChatNullOrNone(raw) {
 		return false, "unsupported_function_call"
@@ -78,6 +88,12 @@ func grokChatResponsesBridgeEligibility(body []byte) (bool, string) {
 			return false, "invalid_stream"
 		}
 	}
+	if raw, ok := root["parallel_tool_calls"]; ok {
+		var parallelToolCalls *bool
+		if json.Unmarshal(raw, &parallelToolCalls) != nil || parallelToolCalls == nil {
+			return false, "invalid_parallel_tool_calls"
+		}
+	}
 	if raw, ok := root["stream_options"]; ok {
 		var options map[string]json.RawMessage
 		if json.Unmarshal(raw, &options) != nil || options == nil {
@@ -128,42 +144,238 @@ func grokChatResponsesBridgeEligibility(body []byte) (bool, string) {
 		return false, "invalid_messages"
 	}
 	for _, message := range messages {
-		for field := range message {
-			if field != "role" && field != "content" {
-				return false, "unsafe_message_field_" + field
-			}
-		}
 		var role string
 		if raw, exists := message["role"]; !exists || json.Unmarshal(raw, &role) != nil {
 			return false, "invalid_message_role"
 		}
 		switch role {
-		case "system", "user", "assistant":
+		case "system", "user":
+			if ok, reason := grokChatMessageFieldsBridgeable(message, "role", "content"); !ok {
+				return false, reason
+			}
+			raw, exists := message["content"]
+			if !exists {
+				return false, "non_text_message_content"
+			}
+			if ok, reason := grokChatRequiredMessageContentBridgeable(raw); !ok {
+				return false, reason
+			}
+		case "assistant":
+			if ok, reason := grokChatMessageFieldsBridgeable(message, "role", "content", "tool_calls"); !ok {
+				return false, reason
+			}
+			toolCallCount := 0
+			if raw, exists := message["tool_calls"]; exists {
+				var reason string
+				toolCallCount, reason = grokChatAssistantToolCallsBridgeable(raw)
+				if reason != "" {
+					return false, reason
+				}
+			}
+			raw, hasContent := message["content"]
+			if !hasContent || strings.TrimSpace(string(raw)) == "null" {
+				if toolCallCount == 0 {
+					return false, "non_text_message_content"
+				}
+				continue
+			}
+			var content string
+			if json.Unmarshal(raw, &content) == nil {
+				if strings.TrimSpace(content) == "" && toolCallCount == 0 {
+					return false, "empty_message_content"
+				}
+				continue
+			}
+			if ok, reason := grokChatStructuredContentBridgeable(raw); !ok {
+				return false, reason
+			}
+		case "tool":
+			if ok, reason := grokChatMessageFieldsBridgeable(message, "role", "content", "tool_call_id"); !ok {
+				return false, reason
+			}
+			var callID string
+			if raw, exists := message["tool_call_id"]; !exists || json.Unmarshal(raw, &callID) != nil || strings.TrimSpace(callID) == "" {
+				return false, "invalid_tool_call_id"
+			}
+			var output string
+			if raw, exists := message["content"]; !exists || json.Unmarshal(raw, &output) != nil || output == "" {
+				return false, "invalid_tool_message_content"
+			}
 		default:
 			return false, "unsupported_message_role_" + role
 		}
-		raw, exists := message["content"]
-		if !exists {
-			return false, "non_text_message_content"
-		}
-		var content string
-		if json.Unmarshal(raw, &content) == nil {
-			if strings.TrimSpace(content) == "" {
-				return false, "empty_message_content"
-			}
-			continue
-		}
-		// Structured content: only allow arrays whose parts are text or
-		// image_url. These are losslessly convertible to Responses input_text/
-		// input_image parts, so the bridge preserves Chat Completions semantics.
-		if ok, reason := grokChatStructuredContentBridgeable(raw); !ok {
-			return false, reason
-		}
 	}
 
 	return true, ""
 }
 
+func grokChatFunctionDeclarationsBridgeable(raw json.RawMessage) (bool, string) {
+	if strings.TrimSpace(string(raw)) == "null" {
+		return true, ""
+	}
+	var declarations []json.RawMessage
+	if json.Unmarshal(raw, &declarations) != nil {
+		return false, "invalid_tools"
+	}
+	for _, declaration := range declarations {
+		var tool map[string]json.RawMessage
+		if json.Unmarshal(declaration, &tool) != nil || tool == nil {
+			return false, "invalid_tool"
+		}
+		for field := range tool {
+			if field != "type" && field != "function" {
+				return false, "unsafe_tool_field_" + field
+			}
+		}
+		var toolType string
+		if rawType, exists := tool["type"]; !exists || json.Unmarshal(rawType, &toolType) != nil || toolType != "function" {
+			return false, "unsupported_tool_type"
+		}
+		functionRaw, exists := tool["function"]
+		if !exists {
+			return false, "invalid_tool_function"
+		}
+
+		var function map[string]json.RawMessage
+		if json.Unmarshal(functionRaw, &function) != nil || function == nil {
+			return false, "invalid_tool_function"
+		}
+		for field := range function {
+			switch field {
+			case "name", "description", "parameters", "strict":
+			default:
+				return false, "unsafe_tool_function_field_" + field
+			}
+		}
+		var name string
+		if rawName, exists := function["name"]; !exists || json.Unmarshal(rawName, &name) != nil || strings.TrimSpace(name) == "" {
+			return false, "invalid_tool_function_name"
+		}
+		if rawDescription, exists := function["description"]; exists {
+			var description string
+			if json.Unmarshal(rawDescription, &description) != nil {
+				return false, "invalid_tool_function_description"
+			}
+		}
+		var parameters map[string]json.RawMessage
+		if rawParameters, exists := function["parameters"]; !exists || json.Unmarshal(rawParameters, &parameters) != nil || parameters == nil {
+			return false, "invalid_tool_function_parameters"
+		}
+		if rawStrict, exists := function["strict"]; exists {
+			var strict bool
+			if json.Unmarshal(rawStrict, &strict) != nil {
+				return false, "invalid_tool_function_strict"
+			}
+		}
+	}
+	return true, ""
+}
+
+func grokChatToolChoiceBridgeable(raw json.RawMessage) (bool, string) {
+	if strings.TrimSpace(string(raw)) == "null" {
+		return true, ""
+	}
+	var choice string
+	if json.Unmarshal(raw, &choice) != nil {
+		return false, "unsupported_tool_choice"
+	}
+	switch choice {
+	case "auto", "none", "required":
+		return true, ""
+	default:
+		return false, "unsupported_tool_choice"
+	}
+}
+
+func grokChatHasFunctionDeclarations(root map[string]json.RawMessage) bool {
+	for _, field := range []string{"tools", "functions"} {
+		raw, exists := root[field]
+		if !exists {
+			continue
+		}
+		var declarations []json.RawMessage
+		if json.Unmarshal(raw, &declarations) == nil && len(declarations) > 0 {
+			return true
+		}
+	}
+	return false
+}
+
+func grokChatMessageFieldsBridgeable(message map[string]json.RawMessage, allowedFields ...string) (bool, string) {
+	allowed := make(map[string]struct{}, len(allowedFields))
+	for _, field := range allowedFields {
+		allowed[field] = struct{}{}
+	}
+	for field := range message {
+		if _, ok := allowed[field]; !ok {
+			return false, "unsafe_message_field_" + field
+		}
+	}
+	return true, ""
+}
+
+func grokChatRequiredMessageContentBridgeable(raw json.RawMessage) (bool, string) {
+	var content string
+	if json.Unmarshal(raw, &content) == nil {
+		if strings.TrimSpace(content) == "" {
+			return false, "empty_message_content"
+		}
+		return true, ""
+	}
+	// Structured content: only allow arrays whose parts are text or
+	// image_url. These are losslessly convertible to Responses input_text/
+	// input_image parts, so the bridge preserves Chat Completions semantics.
+	return grokChatStructuredContentBridgeable(raw)
+}
+
+func grokChatAssistantToolCallsBridgeable(raw json.RawMessage) (int, string) {
+	if strings.TrimSpace(string(raw)) == "null" {
+		return 0, ""
+	}
+	var calls []map[string]json.RawMessage
+	if json.Unmarshal(raw, &calls) != nil {
+		return 0, "invalid_tool_calls"
+	}
+	for _, call := range calls {
+		if call == nil {
+			return 0, "invalid_tool_call"
+		}
+		for field := range call {
+			switch field {
+			case "id", "type", "function":
+			default:
+				return 0, "unsafe_tool_call_field_" + field
+			}
+		}
+		var callID string
+		if rawID, exists := call["id"]; !exists || json.Unmarshal(rawID, &callID) != nil || strings.TrimSpace(callID) == "" {
+			return 0, "invalid_tool_call_id"
+		}
+		var callType string
+		if rawType, exists := call["type"]; !exists || json.Unmarshal(rawType, &callType) != nil || callType != "function" {
+			return 0, "unsupported_tool_call_type"
+		}
+		var function map[string]json.RawMessage
+		if rawFunction, exists := call["function"]; !exists || json.Unmarshal(rawFunction, &function) != nil || function == nil {
+			return 0, "invalid_tool_call_function"
+		}
+		for field := range function {
+			if field != "name" && field != "arguments" {
+				return 0, "unsafe_tool_call_function_field_" + field
+			}
+		}
+		var name string
+		if rawName, exists := function["name"]; !exists || json.Unmarshal(rawName, &name) != nil || strings.TrimSpace(name) == "" {
+			return 0, "invalid_tool_call_function_name"
+		}
+		var arguments string
+		if rawArguments, exists := function["arguments"]; !exists || json.Unmarshal(rawArguments, &arguments) != nil || !json.Valid([]byte(arguments)) {
+			return 0, "invalid_tool_call_arguments"
+		}
+	}
+	return len(calls), ""
+}
+
 func grokChatStructuredContentBridgeable(raw json.RawMessage) (bool, string) {
 	var parts []map[string]json.RawMessage
 	if err := json.Unmarshal(raw, &parts); err != nil {
@@ -199,14 +411,6 @@ func grokChatStructuredContentBridgeable(raw json.RawMessage) (bool, string) {
 	return true, ""
 }
 
-func grokChatNullOrEmptyArray(raw json.RawMessage) bool {
-	if strings.TrimSpace(string(raw)) == "null" {
-		return true
-	}
-	var values []json.RawMessage
-	return json.Unmarshal(raw, &values) == nil && len(values) == 0
-}
-
 func grokChatNullOrNone(raw json.RawMessage) bool {
 	if strings.TrimSpace(string(raw)) == "null" {
 		return true
@@ -215,14 +419,30 @@ func grokChatNullOrNone(raw json.RawMessage) bool {
 	return json.Unmarshal(raw, &value) == nil && strings.EqualFold(strings.TrimSpace(value), "none")
 }
 
-func grokChatCacheIntentBody(body []byte) ([]byte, error) {
+func grokChatNullOrEmptyArray(raw json.RawMessage) bool {
+	if strings.TrimSpace(string(raw)) == "null" {
+		return true
+	}
+	var values []json.RawMessage
+	return json.Unmarshal(raw, &values) == nil && len(values) == 0
+}
+
+func grokChatResponsesCacheIntentBody(body []byte) ([]byte, error) {
+	// An empty Chat tools array is omitted by the Responses converter. In that
+	// case auto/none is also a semantic no-op and must not suppress the normal
+	// tool-free cache route. Non-empty converted tools are always kept intact.
+	if gjson.GetBytes(body, "tools").Exists() {
+		return append([]byte(nil), body...), nil
+	}
+	choice := gjson.GetBytes(body, "tool_choice")
+	if !choice.Exists() || choice.Type != gjson.String || (choice.String() != "auto" && choice.String() != "none") {
+		return append([]byte(nil), body...), nil
+	}
 	var root map[string]json.RawMessage
 	if err := json.Unmarshal(body, &root); err != nil {
 		return nil, err
 	}
-	for _, field := range []string{"tools", "tool_choice", "functions", "function_call"} {
-		delete(root, field)
-	}
+	delete(root, "tool_choice")
 	return json.Marshal(root)
 }
 
@@ -277,18 +497,25 @@ func (s *OpenAIGatewayService) forwardGrokChatCompletionsViaResponses(
 	if err != nil {
 		return nil, fmt.Errorf("marshal grok responses bridge request: %w", err)
 	}
+	// Preserve the converted Responses intent before Grok capability
+	// sanitization. Cache routing must see the actual client function tools,
+	// not the nested Chat Completions declarations and not a tool-free copy.
+	intentBody, err := grokChatResponsesCacheIntentBody(responsesBody)
+	if err != nil {
+		return nil, fmt.Errorf("normalize grok responses bridge cache intent: %w", err)
+	}
 	responsesBody, err = patchGrokResponsesBody(responsesBody, upstreamModel)
 	if err != nil {
 		return nil, fmt.Errorf("patch grok responses bridge request: %w", err)
 	}
-	intentBody, err := grokChatCacheIntentBody(body)
-	if err != nil {
-		return nil, fmt.Errorf("normalize grok responses bridge tool intent: %w", err)
-	}
 	responsesBody, err = applyGrokResponsesCacheIdentity(responsesBody, intentBody, cacheIdentity, true)
 	if err != nil {
 		return nil, fmt.Errorf("apply grok responses bridge cache identity: %w", err)
 	}
+	responsesBody, err = applyGrokFreeRequestToolCacheRoute(c, responsesBody, intentBody, account, cacheIdentity)
+	if err != nil {
+		return nil, fmt.Errorf("apply grok responses bridge function-tool cache route: %w", err)
+	}
 
 	updatedBody, policyErr := s.applyOpenAIFastPolicyToBody(ctx, account, upstreamModel, responsesBody)
 	if policyErr != nil {
diff --git a/backend/internal/service/openai_gateway_grok_chat_bridge_test.go b/backend/internal/service/openai_gateway_grok_chat_bridge_test.go
index 86fc45e952..6e39bae15d 100644
--- a/backend/internal/service/openai_gateway_grok_chat_bridge_test.go
+++ b/backend/internal/service/openai_gateway_grok_chat_bridge_test.go
@@ -75,15 +75,60 @@ func TestGrokChatResponsesBridgeEligibility(t *testing.T) {
 			reason: "empty_message_content",
 		},
 		{
-			name:   "function tools fall back",
-			body:   `{"model":"grok","messages":[{"role":"user","content":"hi"}],"tools":[{"type":"function","function":{"name":"lookup"}}]}`,
-			reason: "unsupported_tools",
+			name: "function tools bridge",
+			body: `{"model":"grok","messages":[{"role":"user","content":"hi"}],"tools":[{"type":"function","function":{"name":"lookup","parameters":{"type":"object"},"strict":false}}]}`,
+			want: true,
 		},
 		{
-			name:   "automatic tool choice falls back",
-			body:   `{"model":"grok","messages":[{"role":"user","content":"hi"}],"tools":[],"tool_choice":"auto"}`,
+			name:   "legacy functions fall back",
+			body:   `{"model":"grok","messages":[{"role":"user","content":"hi"}],"functions":[{"name":"lookup","parameters":{"type":"object"}}]}`,
+			reason: "unsupported_functions",
+		},
+		{
+			name: "automatic tool choice bridges",
+			body: `{"model":"grok","messages":[{"role":"user","content":"hi"}],"tools":[],"tool_choice":"auto"}`,
+			want: true,
+		},
+		{
+			name:   "required tool choice without tools falls back",
+			body:   `{"model":"grok","messages":[{"role":"user","content":"hi"}],"tools":[],"tool_choice":"required"}`,
+			reason: "required_tool_choice_without_tools",
+		},
+		{
+			name: "tool history bridges",
+			body: `{"model":"grok","messages":[{"role":"assistant","content":null,"tool_calls":[{"id":"call_lookup","type":"function","function":{"name":"lookup","arguments":"{\"key\":\"alpha\"}"}}]},{"role":"tool","tool_call_id":"call_lookup","content":"{\"value\":\"ok\"}"},{"role":"user","content":"summarize"}],"tools":[{"type":"function","function":{"name":"lookup","parameters":{"type":"object"}}}],"tool_choice":"auto","parallel_tool_calls":true}`,
+			want: true,
+		},
+		{
+			name:   "unknown tool type falls back",
+			body:   `{"model":"grok","messages":[{"role":"user","content":"hi"}],"tools":[{"type":"web_search","function":{"name":"lookup","parameters":{"type":"object"}}}]}`,
+			reason: "unsupported_tool_type",
+		},
+		{
+			name:   "missing tool schema falls back",
+			body:   `{"model":"grok","messages":[{"role":"user","content":"hi"}],"tools":[{"type":"function","function":{"name":"lookup"}}]}`,
+			reason: "invalid_tool_function_parameters",
+		},
+		{
+			name:   "named tool choice falls back",
+			body:   `{"model":"grok","messages":[{"role":"user","content":"hi"}],"tools":[{"type":"function","function":{"name":"lookup","parameters":{"type":"object"}}}],"tool_choice":{"type":"function","function":{"name":"lookup"}}}`,
 			reason: "unsupported_tool_choice",
 		},
+		{
+			name:   "invalid tool call arguments fall back",
+			body:   `{"model":"grok","messages":[{"role":"assistant","content":null,"tool_calls":[{"id":"call_lookup","type":"function","function":{"name":"lookup","arguments":"{"}}]}]}`,
+			reason: "invalid_tool_call_arguments",
+		},
+		{
+			name:   "tool result without call id falls back",
+			body:   `{"model":"grok","messages":[{"role":"tool","content":"ok"}]}`,
+			reason: "invalid_tool_call_id",
+		},
+		{
+			name:   "non boolean parallel tool calls falls back",
+			body:   `{"model":"grok","messages":[{"role":"user","content":"hi"}],"parallel_tool_calls":"true"}`,
+			reason: "invalid_parallel_tool_calls",
+		},
 		{
 			name:   "reasoning effort falls back because conversion adds summary",
 			body:   `{"model":"grok","messages":[{"role":"user","content":"hi"}],"reasoning_effort":"high"}`,
@@ -100,9 +145,9 @@ func TestGrokChatResponsesBridgeEligibility(t *testing.T) {
 			reason: "empty_message_content",
 		},
 		{
-			name:   "tool history falls back",
+			name:   "empty tool history falls back",
 			body:   `{"model":"grok","messages":[{"role":"assistant","content":"","tool_calls":[]}]}`,
-			reason: "unsafe_message_field_tool_calls",
+			reason: "empty_message_content",
 		},
 		{
 			name:   "unknown field falls back",
@@ -183,6 +228,64 @@ func TestForwardGrokChatViaResponsesNonStreamingCachesAndReturnsChat(t *testing.
 	require.NotNil(t, repo.updates[account.ID][grokQuotaSnapshotExtraKey])
 }
 
+func TestForwardGrokChatViaResponsesTraeToolHistoryKeepsCacheRoute(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	firstTurnBody := []byte(`{"model":"grok","messages":[{"role":"system","content":"Be concise"},{"role":"user","content":"Find alpha"}],"stream":false,"prompt_cache_key":"trae-session","tools":[{"type":"function","function":{"name":"lookup","description":"Lookup a value","parameters":{"type":"object","properties":{"key":{"type":"string"}},"required":["key"]},"strict":false}}],"tool_choice":"auto","parallel_tool_calls":true}`)
+	body := []byte(`{"model":"grok","messages":[{"role":"system","content":"Be concise"},{"role":"user","content":"Find alpha"},{"role":"assistant","content":null,"tool_calls":[{"id":"call_lookup","type":"function","function":{"name":"lookup","arguments":"{\"key\":\"alpha\"}"}}]},{"role":"tool","tool_call_id":"call_lookup","content":"{\"value\":\"ok\"}"},{"role":"user","content":"Summarize"}],"stream":false,"prompt_cache_key":"trae-session","tools":[{"type":"function","function":{"name":"lookup","description":"Lookup a value","parameters":{"type":"object","properties":{"key":{"type":"string"}},"required":["key"]},"strict":false}}],"tool_choice":"auto","parallel_tool_calls":true}`)
+	recorder := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(recorder)
+	c.Request = httptest.NewRequest(http.MethodPost, grokChatRawEndpoint, bytes.NewReader(body))
+	c.Request.Header.Set(grokClientToolCacheOptInHeader, "prefer-cache")
+	c.Set("api_key", &APIKey{ID: 7151})
+
+	account := grokChatBridgeTestAccount(715)
+	account.Credentials["subscription_tier"] = "free"
+	repo := &grokQuotaAccountRepo{mockAccountRepoForPlatform: &mockAccountRepoForPlatform{
+		accountsByID: map[int64]*Account{account.ID: account},
+	}}
+	upstream := &httpUpstreamRecorder{resp: grokChatBridgeCompletedResponse("resp_grok_chat_trae", 8192)}
+	svc := &OpenAIGatewayService{
+		httpUpstream:      upstream,
+		grokTokenProvider: NewGrokTokenProvider(repo, nil),
+		accountRepo:       repo,
+	}
+
+	firstTurnIdentity := resolveGrokCacheIdentity(c, firstTurnBody, "", "grok-4.5")
+	extendedTurnIdentity := resolveGrokCacheIdentity(c, body, "", "grok-4.5")
+	require.NotEmpty(t, firstTurnIdentity)
+	require.Equal(t, firstTurnIdentity, extendedTurnIdentity)
+
+	result, err := svc.ForwardAsChatCompletions(context.Background(), c, account, body, "", "")
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.Equal(t, xai.DefaultCLIBaseURL+"/responses", upstream.lastReq.URL.String())
+	require.Equal(t, grokChatResponsesEndpoint, result.UpstreamEndpoint)
+	require.Equal(t, extendedTurnIdentity, gjson.GetBytes(upstream.lastBody, "prompt_cache_key").String())
+	require.Equal(t, extendedTurnIdentity, upstream.lastReq.Header.Get(grokConversationIDHeader))
+
+	tools := gjson.GetBytes(upstream.lastBody, "tools").Array()
+	require.Len(t, tools, 3)
+	require.Equal(t, "function", tools[0].Get("type").String())
+	require.Equal(t, "lookup", tools[0].Get("name").String())
+	require.Equal(t, "Lookup a value", tools[0].Get("description").String())
+	require.Equal(t, "string", tools[0].Get("parameters.properties.key.type").String())
+	require.True(t, tools[0].Get("strict").Exists())
+	require.False(t, tools[0].Get("strict").Bool())
+	require.Equal(t, "web_search", tools[1].Get("type").String())
+	require.Equal(t, "x_search", tools[2].Get("type").String())
+	require.Equal(t, "auto", gjson.GetBytes(upstream.lastBody, "tool_choice").String())
+	require.True(t, gjson.GetBytes(upstream.lastBody, "parallel_tool_calls").Bool())
+
+	require.Equal(t, "function_call", gjson.GetBytes(upstream.lastBody, "input.2.type").String())
+	require.Equal(t, "call_lookup", gjson.GetBytes(upstream.lastBody, "input.2.call_id").String())
+	require.Equal(t, "lookup", gjson.GetBytes(upstream.lastBody, "input.2.name").String())
+	require.Equal(t, `{"key":"alpha"}`, gjson.GetBytes(upstream.lastBody, "input.2.arguments").String())
+	require.Equal(t, "function_call_output", gjson.GetBytes(upstream.lastBody, "input.3.type").String())
+	require.Equal(t, "call_lookup", gjson.GetBytes(upstream.lastBody, "input.3.call_id").String())
+	require.Equal(t, `{"value":"ok"}`, gjson.GetBytes(upstream.lastBody, "input.3.output").String())
+}
+
 func TestForwardGrokChatViaResponsesStreamingPropagatesCachedUsage(t *testing.T) {
 	gin.SetMode(gin.TestMode)