diff --git a/backend/internal/service/openai_gateway_grok.go b/backend/internal/service/openai_gateway_grok.go
index 198055f20e..dec30c3bd2 100644
--- a/backend/internal/service/openai_gateway_grok.go
+++ b/backend/internal/service/openai_gateway_grok.go
@@ -52,18 +52,21 @@ func (s *OpenAIGatewayService) forwardGrokResponses(
 	if isGrokImageGenerationModel(upstreamModel) {
 		return nil, fmt.Errorf("model %s is an image model and is not available on the Responses endpoint; use /v1/images/generations instead", upstreamModel)
 	}
-	cacheIdentity := resolveGrokCacheIdentity(c, body, "", upstreamModel)
 	patchedBody, err := patchGrokResponsesBody(body, upstreamModel)
 	if err != nil {
 		return nil, err
 	}
+	// Derive the identity from the request xAI will actually see. This makes
+	// Codex Responses Lite additional_tools part of the stable tool prefix.
+	cacheIdentity := resolveGrokCacheIdentity(c, patchedBody, "", upstreamModel)
+	mixedCacheIntentBody := append([]byte(nil), patchedBody...)
 	patchedBody, err = applyGrokResponsesCacheIdentity(patchedBody, body, cacheIdentity, account.IsGrokOAuth())
 	if err != nil {
 		return nil, fmt.Errorf("apply grok prompt cache identity: %w", err)
 	}
 	// Free OAuth + client function tools: reuse Messages mixed-tools cache route
 	// (append web_search/x_search so xAI does not force non-cacheable build-free).
-	patchedBody, err = applyGrokFreeMessagesFunctionToolCacheRoute(patchedBody, body, account, cacheIdentity)
+	patchedBody, err = applyGrokFreeRequestToolCacheRoute(c, patchedBody, mixedCacheIntentBody, account, cacheIdentity)
 	if err != nil {
 		return nil, fmt.Errorf("apply grok Free function-tool cache route: %w", err)
 	}
@@ -374,10 +377,9 @@ func deleteJSONFields(value any, fields map[string]struct{}) bool {
 }
 
 // additional_tools is a Codex/Responses Lite private input carrier. xAI's
-// Responses schema accepts ordinary message/function-call input items but
-// rejects this carrier before inference with a ModelInput deserialization
-// error. Top-level supported tools remain available through the separate
-// sanitizeGrokResponsesTools path.
+// Responses schema rejects the carrier itself, but accepts supported tools at
+// the top level. Preserve top-level order, append newly discovered tools in
+// carrier order, then let sanitizeGrokResponsesTools filter unsupported types.
 func sanitizeGrokResponsesInput(body []byte) ([]byte, error) {
 	if !bytes.Contains(body, []byte(`"additional_tools"`)) {
 		return body, nil
@@ -389,8 +391,36 @@ func sanitizeGrokResponsesInput(body []byte) ([]byte, error) {
 
 	rawItems := input.Array()
 	filtered := make([]json.RawMessage, 0, len(rawItems))
+	topLevelTools := gjson.GetBytes(body, "tools")
+	mergedTools := make([]json.RawMessage, 0)
+	seenTools := make(map[string]struct{})
+	appendTool := func(tool gjson.Result) bool {
+		key := grokResponsesToolDedupKey(tool)
+		if _, exists := seenTools[key]; exists {
+			return false
+		}
+		seenTools[key] = struct{}{}
+		mergedTools = append(mergedTools, json.RawMessage(tool.Raw))
+		return true
+	}
+	if topLevelTools.IsArray() {
+		for _, tool := range topLevelTools.Array() {
+			seenTools[grokResponsesToolDedupKey(tool)] = struct{}{}
+			mergedTools = append(mergedTools, json.RawMessage(tool.Raw))
+		}
+	}
+
+	promoted := false
 	for _, item := range rawItems {
 		if strings.TrimSpace(item.Get("type").String()) == "additional_tools" {
+			tools := item.Get("tools")
+			if tools.IsArray() {
+				for _, tool := range tools.Array() {
+					if appendTool(tool) {
+						promoted = true
+					}
+				}
+			}
 			continue
 		}
 		filtered = append(filtered, json.RawMessage(item.Raw))
@@ -402,7 +432,30 @@ func sanitizeGrokResponsesInput(body []byte) ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
-	return sjson.SetRawBytes(body, "input", encoded)
+	body, err = sjson.SetRawBytes(body, "input", encoded)
+	if err != nil || !promoted {
+		return body, err
+	}
+	encodedTools, err := json.Marshal(mergedTools)
+	if err != nil {
+		return nil, err
+	}
+	return sjson.SetRawBytes(body, "tools", encodedTools)
+}
+
+func grokResponsesToolDedupKey(tool gjson.Result) string {
+	toolType := strings.TrimSpace(tool.Get("type").String())
+	if toolType != "" {
+		if name := strings.TrimSpace(tool.Get("name").String()); name != "" {
+			return "type:" + toolType + "\x00name:" + name
+		}
+		if toolType == "mcp" {
+			if label := strings.TrimSpace(tool.Get("server_label").String()); label != "" {
+				return "type:mcp\x00server_label:" + label
+			}
+		}
+	}
+	return "json:" + normalizeCompatSeedJSON(json.RawMessage(tool.Raw))
 }
 
 // sanitizeGrokReasoningNullContent 删除 reasoning 项中的 "content": null。
diff --git a/backend/internal/service/openai_gateway_grok_cache.go b/backend/internal/service/openai_gateway_grok_cache.go
index d9e34cbb58..9fb916cacd 100644
--- a/backend/internal/service/openai_gateway_grok_cache.go
+++ b/backend/internal/service/openai_gateway_grok_cache.go
@@ -12,10 +12,12 @@ import (
 )
 
 const (
-	grokConversationIDHeader        = "X-Grok-Conv-Id"
-	grokFreeCacheNativeToolsJSON    = `[{"type":"web_search"},{"type":"x_search"}]`
-	grokFreeCacheDisabledToolChoice = "none"
-	grokFreeRolling24hTokenLimit    = int64(2_000_000)
+	grokConversationIDHeader         = "X-Grok-Conv-Id"
+	grokClientToolCacheOptInHeader   = "X-Sub2API-Grok-Client-Tool-Cache"
+	grokFreeCacheNativeToolsJSON     = `[{"type":"web_search"},{"type":"x_search"}]`
+	grokFreeCacheDisabledToolChoice  = "none"
+	grokClientToolCacheOptInExtraKey = "grok_client_tool_cache_enabled"
+	grokFreeRolling24hTokenLimit     = int64(2_000_000)
 )
 
 // resolveGrokCacheIdentity derives one stable, tenant-isolated routing identity
@@ -122,7 +124,7 @@ func applyGrokResponsesCacheIdentity(body, intentSourceBody []byte, identity str
 	// Inspect the pre-sanitization source. patchGrokResponsesBody may remove an
 	// unsupported client tool and its tool_choice; that must not turn an
 	// explicit client tool intent into an eligible native-tool request.
-	if gjson.GetBytes(intentSourceBody, "tools").Exists() || gjson.GetBytes(intentSourceBody, "tool_choice").Exists() {
+	if hasGrokResponsesToolIntent(intentSourceBody) {
 		return out, nil
 	}
 	out, err = sjson.SetRawBytes(out, "tools", []byte(grokFreeCacheNativeToolsJSON))
@@ -132,12 +134,113 @@ func applyGrokResponsesCacheIdentity(body, intentSourceBody []byte, identity str
 	return sjson.SetBytes(out, "tool_choice", grokFreeCacheDisabledToolChoice)
 }
 
+func hasGrokResponsesToolIntent(body []byte) bool {
+	if gjson.GetBytes(body, "tools").Exists() || gjson.GetBytes(body, "tool_choice").Exists() {
+		return true
+	}
+	input := gjson.GetBytes(body, "input")
+	if !input.IsArray() {
+		return false
+	}
+	for _, item := range input.Array() {
+		if strings.TrimSpace(item.Get("type").String()) != "additional_tools" {
+			continue
+		}
+		tools := item.Get("tools")
+		if !tools.Exists() || !tools.IsArray() || len(tools.Array()) > 0 {
+			return true
+		}
+	}
+	return false
+}
+
 // applyGrokFreeMessagesFunctionToolCacheRoute enables xAI's cache-capable
-// mixed-tools route only for the Anthropic Messages bridge and only when the
-// selected account is known to be Free. Native tools become eligible under
-// auto selection, so callers must not apply this policy to paid accounts or
-// other ingress protocols implicitly.
+// mixed-tools route only for known Free accounts. Pure client tools default to
+// the cache-capable route so an intermediate sub2api does not need to preserve
+// client-specific opt-in headers. Operators can explicitly disable this per
+// account when native search tools would change the desired behavior (#4486).
 func applyGrokFreeMessagesFunctionToolCacheRoute(body, intentSourceBody []byte, account *Account, cacheIdentity string) ([]byte, error) {
+	allowPureClientTools, _ := grokClientToolCacheAccountPolicy(account)
+	return applyGrokFreeToolCacheRoute(body, intentSourceBody, account, cacheIdentity, allowPureClientTools, true)
+}
+
+// applyGrokFreeRequestToolCacheRoute also accepts a request-scoped opt-in. The
+// sub2api header is consumed locally because buildGrokResponsesRequest only
+// forwards the explicitly supported OpenAI-Beta header from downstream.
+func applyGrokFreeRequestToolCacheRoute(c *gin.Context, body, intentSourceBody []byte, account *Account, cacheIdentity string) ([]byte, error) {
+	allowPureClientTools, accountPolicyExplicit := grokClientToolCacheAccountPolicy(account)
+	requestOptOut := false
+	if c != nil {
+		switch strings.ToLower(strings.TrimSpace(c.GetHeader(grokClientToolCacheOptInHeader))) {
+		case "1", "true", "yes", "on", "prefer-cache":
+			allowPureClientTools = true
+		case "0", "false", "no", "off":
+			allowPureClientTools = false
+			requestOptOut = true
+		}
+	}
+	if !allowPureClientTools && !accountPolicyExplicit && !requestOptOut && isGrokClaudeDesktopResponsesCacheRequest(c) {
+		allowPureClientTools = true
+	}
+	// A function merely named web_search/x_search is still a client function.
+	// Known Free OAuth accounts use the cache route by default; a request-scoped
+	// opt-in may override an account opt-out, while an explicit request opt-out
+	// always wins. The legacy Claude fingerprint remains only as a compatibility
+	// fallback when no account policy has been recorded (#4486).
+	return applyGrokFreeToolCacheRoute(body, intentSourceBody, account, cacheIdentity, allowPureClientTools, allowPureClientTools)
+}
+
+// grokClientToolCacheAccountPolicy is intentionally strict for configured
+// values: only a JSON boolean is accepted. A missing key defaults on solely for
+// accounts positively identified as Grok Free OAuth; paid, API-key, and unknown
+// accounts remain fail-closed.
+func grokClientToolCacheAccountPolicy(account *Account) (enabled, explicit bool) {
+	if !isKnownGrokFreeAccount(account) {
+		return false, false
+	}
+	if account.Extra == nil {
+		return true, false
+	}
+	value, exists := account.Extra[grokClientToolCacheOptInExtraKey]
+	if !exists {
+		return true, false
+	}
+	enabled, valid := value.(bool)
+	if !valid {
+		return false, true
+	}
+	return enabled, true
+}
+
+// isGrokClaudeDesktopResponsesCacheRequest recognizes the strict wire
+// fingerprint emitted when Claude Desktop's local agent is translated by
+// CC Switch into an OpenAI Responses request. Requiring every independent
+// signal prevents a generic Claude-compatible client (or the Chat bridge)
+// from silently opting into the mixed native/client tool route.
+func isGrokClaudeDesktopResponsesCacheRequest(c *gin.Context) bool {
+	if c == nil || c.Request == nil || c.Request.URL == nil || isOpenAIResponsesCompactPath(c) {
+		return false
+	}
+	path := strings.TrimRight(strings.TrimSpace(c.Request.URL.Path), "/")
+	if !strings.HasSuffix(path, "/responses") {
+		return false
+	}
+
+	if !claudeCodeUAPattern.MatchString(strings.TrimSpace(c.GetHeader("User-Agent"))) {
+		return false
+	}
+	switch strings.ToLower(strings.TrimSpace(c.GetHeader("X-App"))) {
+	case "cli", "cli-bg":
+	default:
+		return false
+	}
+	if !strings.EqualFold(strings.TrimSpace(c.GetHeader("anthropic-client-platform")), "desktop_app") {
+		return false
+	}
+	return strings.TrimSpace(c.GetHeader("X-Claude-Code-Session-Id")) != ""
+}
+
+func applyGrokFreeToolCacheRoute(body, intentSourceBody []byte, account *Account, cacheIdentity string, allowPureClientTools, allowFunctionSearch bool) ([]byte, error) {
 	if strings.TrimSpace(cacheIdentity) == "" || !isKnownGrokFreeAccount(account) {
 		return body, nil
 	}
@@ -146,7 +249,12 @@ func applyGrokFreeMessagesFunctionToolCacheRoute(body, intentSourceBody []byte,
 	if !isGrokFreeCacheFunctionToolIntent(intentTools, intentToolChoice) {
 		return body, nil
 	}
-	return appendMissingGrokFreeCacheNativeTools(body)
+	if intentToolChoice.Type == gjson.String && strings.TrimSpace(intentToolChoice.String()) == grokFreeCacheDisabledToolChoice {
+		// Adding native cache-routing tools cannot change behavior when the
+		// client has explicitly disabled all tool execution.
+		return appendGrokFreeCacheNativeToolsWithPolicy(body, true, false)
+	}
+	return appendGrokFreeCacheNativeToolsWithPolicy(body, allowPureClientTools, allowFunctionSearch)
 }
 
 func isKnownGrokFreeAccount(account *Account) bool {
@@ -231,22 +339,44 @@ func isGrokFreeCacheFunctionToolIntent(tools, toolChoice gjson.Result) bool {
 		return false
 	}
 	for _, tool := range items {
-		if !tool.IsObject() || strings.TrimSpace(tool.Get("type").String()) != "function" {
+		if !tool.IsObject() {
 			return false
 		}
-		// Responses function declarations keep name at the top level. Reject
-		// Chat Completions' nested function shape and incomplete declarations.
-		if strings.TrimSpace(tool.Get("name").String()) == "" || tool.Get("function").Exists() {
+		toolType := strings.TrimSpace(tool.Get("type").String())
+		if _, ok := grokResponsesSupportedToolTypes[toolType]; !ok {
 			return false
 		}
+		if toolType == "function" {
+			// Responses function declarations keep name at the top level. Reject
+			// Chat Completions' nested function shape and incomplete declarations.
+			if strings.TrimSpace(tool.Get("name").String()) == "" || tool.Get("function").Exists() {
+				return false
+			}
+		}
 	}
 	if !toolChoice.Exists() {
 		return true
 	}
-	return toolChoice.Type == gjson.String && strings.TrimSpace(toolChoice.String()) == "auto"
+	if toolChoice.Type != gjson.String {
+		return false
+	}
+	switch strings.TrimSpace(toolChoice.String()) {
+	case "auto", grokFreeCacheDisabledToolChoice:
+		return true
+	default:
+		return false
+	}
 }
 
 func appendMissingGrokFreeCacheNativeTools(body []byte) ([]byte, error) {
+	return appendGrokFreeCacheNativeTools(body, false)
+}
+
+func appendGrokFreeCacheNativeTools(body []byte, allowPureClientTools bool) ([]byte, error) {
+	return appendGrokFreeCacheNativeToolsWithPolicy(body, allowPureClientTools, true)
+}
+
+func appendGrokFreeCacheNativeToolsWithPolicy(body []byte, allowPureClientTools, allowFunctionSearch bool) ([]byte, error) {
 	tools := gjson.GetBytes(body, "tools")
 	if !tools.Exists() || !tools.IsArray() {
 		return body, nil
@@ -256,9 +386,19 @@ func appendMissingGrokFreeCacheNativeTools(body []byte) ([]byte, error) {
 	if len(items) == 0 {
 		return body, nil
 	}
+	hasNativeSearch := false
+	for _, tool := range items {
+		switch strings.TrimSpace(tool.Get("type").String()) {
+		case "web_search", "x_search":
+			hasNativeSearch = true
+		}
+	}
+	if !allowPureClientTools && !allowFunctionSearch && !hasNativeSearch {
+		return body, nil
+	}
 	merged := make([]json.RawMessage, 0, len(items)+2)
 	present := make(map[string]bool, 2)
-	hasFunction := false
+	hasCompanionTool := false
 	for _, tool := range items {
 		toolType := strings.TrimSpace(tool.Get("type").String())
 		switch toolType {
@@ -269,7 +409,7 @@ func appendMissingGrokFreeCacheNativeTools(body []byte) ([]byte, error) {
 			}
 			// Grok Build may declare search as function tools. Convert to native
 			// entries so Free OAuth stays cache-capable without duplicate names.
-			if name == "web_search" || name == "x_search" {
+			if (name == "web_search" || name == "x_search") && allowFunctionSearch {
 				if present[name] {
 					continue
 				}
@@ -279,9 +419,17 @@ func appendMissingGrokFreeCacheNativeTools(body []byte) ([]byte, error) {
 				}
 				merged = append(merged, raw)
 				present[name] = true
+				if allowPureClientTools {
+					hasCompanionTool = true
+				}
 				continue
 			}
-			hasFunction = true
+			if name == "web_search" || name == "x_search" {
+				// Keep the client function intact and avoid adding a same-named
+				// native tool unless conversion was explicitly enabled.
+				present[name] = true
+			}
+			hasCompanionTool = true
 			merged = append(merged, json.RawMessage(tool.Raw))
 		case "web_search", "x_search":
 			if present[toolType] {
@@ -290,17 +438,21 @@ func appendMissingGrokFreeCacheNativeTools(body []byte) ([]byte, error) {
 			merged = append(merged, json.RawMessage(tool.Raw))
 			present[toolType] = true
 		default:
-			return body, nil
+			if _, ok := grokResponsesSupportedToolTypes[toolType]; !ok {
+				return body, nil
+			}
+			hasCompanionTool = true
+			merged = append(merged, json.RawMessage(tool.Raw))
 		}
 	}
-	if !hasFunction {
+	if !hasCompanionTool {
 		return body, nil
 	}
 	// Only complement missing native search tools when the request already contains
 	// at least one search tool (native or function-form). Pure client function tools
 	// (e.g. view_image) must not trigger injection to avoid biasing model tool
 	// selection (#4486).
-	if !present["web_search"] && !present["x_search"] {
+	if !allowPureClientTools && !present["web_search"] && !present["x_search"] {
 		return body, nil
 	}
 	for _, toolType := range []string{"web_search", "x_search"} {
diff --git a/backend/internal/service/openai_gateway_grok_cache_test.go b/backend/internal/service/openai_gateway_grok_cache_test.go
index 73b1ea5ec1..90155aadc6 100644
--- a/backend/internal/service/openai_gateway_grok_cache_test.go
+++ b/backend/internal/service/openai_gateway_grok_cache_test.go
@@ -197,7 +197,7 @@ func TestApplyGrokCacheIdentityWritesResponsesBodyAndHeader(t *testing.T) {
 	require.False(t, gjson.GetBytes(unscopedBody, "tool_choice").Exists())
 }
 
-func TestApplyGrokCacheIdentityAppendsNativeToolsToResponseFunctions(t *testing.T) {
+func TestGrokFreeMessagesClientToolCacheDefaultsOnForKnownFree(t *testing.T) {
 	account := healthyGrokOAuthGatewayTestAccount(901, "access-token")
 	account.Credentials["subscription_tier"] = " FREE "
 	tests := []struct {
@@ -211,7 +211,6 @@ func TestApplyGrokCacheIdentityAppendsNativeToolsToResponseFunctions(t *testing.
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			// Pure client function tools without search → no native injection (#4486).
 			intentBody := []byte(`{"model":"grok","tools":[{"type":"function","name":"lookup","description":"look up a value","parameters":{"type":"object"}},{"type":"function","name":"save","parameters":{"type":"object"}}]` + tt.toolChoiceJSON + `}`)
 			body, err := applyGrokResponsesCacheIdentity(intentBody, intentBody, "isolated-id", true)
 			require.NoError(t, err)
@@ -220,16 +219,46 @@ func TestApplyGrokCacheIdentityAppendsNativeToolsToResponseFunctions(t *testing.
 			require.NoError(t, err)
 			require.Equal(t, "isolated-id", gjson.GetBytes(body, "prompt_cache_key").String())
 			tools := gjson.GetBytes(body, "tools").Array()
-			require.Len(t, tools, 2, "pure client functions should not get native search injected")
+			require.Len(t, tools, 4)
 			require.Equal(t, "function", tools[0].Get("type").String())
 			require.Equal(t, "lookup", tools[0].Get("name").String())
 			require.Equal(t, "function", tools[1].Get("type").String())
 			require.Equal(t, "save", tools[1].Get("name").String())
+			require.Equal(t, "web_search", tools[2].Get("type").String())
+			require.Equal(t, "x_search", tools[3].Get("type").String())
 			require.Equal(t, tt.wantChoice, gjson.GetBytes(body, "tool_choice").Exists())
 		})
 	}
 }
 
+func TestGrokFreeMessagesClientToolCacheDefaultsWithMissingAccountSetting(t *testing.T) {
+	body := []byte(`{"model":"grok","tools":[{"type":"function","name":"view_image","parameters":{"type":"object"}}],"tool_choice":"auto"}`)
+	tests := []struct {
+		name  string
+		extra map[string]any
+	}{
+		{name: "nil extra"},
+		{name: "empty extra", extra: map[string]any{}},
+		{name: "unrelated extra", extra: map[string]any{"other_setting": true}},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			account := healthyGrokOAuthGatewayTestAccount(90101, "access-token")
+			account.Credentials["subscription_tier"] = "free"
+			account.Extra = tt.extra
+
+			patched, err := applyGrokFreeMessagesFunctionToolCacheRoute(body, body, account, "isolated-id")
+
+			require.NoError(t, err)
+			tools := gjson.GetBytes(patched, "tools").Array()
+			require.Len(t, tools, 3)
+			require.Equal(t, "web_search", tools[1].Get("type").String())
+			require.Equal(t, "x_search", tools[2].Get("type").String())
+		})
+	}
+}
+
 func TestApplyGrokCacheIdentityAppendsNativeToolsWhenSearchPresent(t *testing.T) {
 	account := healthyGrokOAuthGatewayTestAccount(901, "access-token")
 	account.Credentials["subscription_tier"] = " FREE "
@@ -249,6 +278,330 @@ func TestApplyGrokCacheIdentityAppendsNativeToolsWhenSearchPresent(t *testing.T)
 	require.Equal(t, "x_search", tools[2].Get("type").String())
 }
 
+func TestGrokFreeClientToolCacheAccountOptIn(t *testing.T) {
+	account := healthyGrokOAuthGatewayTestAccount(9011, "access-token")
+	account.Credentials["subscription_tier"] = "free"
+	account.Extra = map[string]any{grokClientToolCacheOptInExtraKey: true}
+	intentBody := []byte(`{"model":"grok","tools":[{"type":"function","name":"view_image","parameters":{"type":"object"}},{"type":"function","name":"read_file","parameters":{"type":"object"}}],"tool_choice":"auto"}`)
+
+	body, err := applyGrokResponsesCacheIdentity(intentBody, intentBody, "isolated-id", true)
+	require.NoError(t, err)
+	body, err = applyGrokFreeMessagesFunctionToolCacheRoute(body, intentBody, account, "isolated-id")
+	require.NoError(t, err)
+
+	tools := gjson.GetBytes(body, "tools").Array()
+	require.Len(t, tools, 4)
+	require.Equal(t, "view_image", tools[0].Get("name").String())
+	require.Equal(t, "read_file", tools[1].Get("name").String())
+	require.Equal(t, "web_search", tools[2].Get("type").String())
+	require.Equal(t, "x_search", tools[3].Get("type").String())
+}
+
+func TestGrokFreeMessagesClientToolCacheAccountOptOut(t *testing.T) {
+	body := []byte(`{"model":"grok","tools":[{"type":"function","name":"view_image","parameters":{"type":"object"}}],"tool_choice":"auto"}`)
+	tests := []struct {
+		name  string
+		value any
+	}{
+		{name: "explicit false", value: false},
+		{name: "string false is malformed", value: "false"},
+		{name: "numeric value is malformed", value: 1},
+		{name: "null value is malformed", value: nil},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			account := healthyGrokOAuthGatewayTestAccount(90111, "access-token")
+			account.Credentials["subscription_tier"] = "free"
+			account.Extra = map[string]any{grokClientToolCacheOptInExtraKey: tt.value}
+
+			patched, err := applyGrokFreeMessagesFunctionToolCacheRoute(body, body, account, "isolated-id")
+
+			require.NoError(t, err)
+			require.JSONEq(t, string(body), string(patched))
+		})
+	}
+}
+
+func TestGrokFreeClientToolCacheRequestOptInOverridesAccountOptOut(t *testing.T) {
+	account := healthyGrokOAuthGatewayTestAccount(9014, "access-token")
+	account.Credentials["subscription_tier"] = "free"
+	account.Extra = map[string]any{grokClientToolCacheOptInExtraKey: false}
+	c := newGrokCacheTestContext(9014)
+	c.Request.Header.Set(grokClientToolCacheOptInHeader, "prefer-cache")
+	intentBody := []byte(`{"model":"grok","tools":[{"type":"function","name":"view_image","parameters":{"type":"object"}}],"tool_choice":"auto"}`)
+
+	body, err := applyGrokResponsesCacheIdentity(intentBody, intentBody, "isolated-id", true)
+	require.NoError(t, err)
+	body, err = applyGrokFreeRequestToolCacheRoute(c, body, intentBody, account, "isolated-id")
+	require.NoError(t, err)
+
+	tools := gjson.GetBytes(body, "tools").Array()
+	require.Len(t, tools, 3)
+	require.Equal(t, "view_image", tools[0].Get("name").String())
+	require.Equal(t, "web_search", tools[1].Get("type").String())
+	require.Equal(t, "x_search", tools[2].Get("type").String())
+}
+
+func TestGrokFreeChatRequestClientToolCacheDefaultsOnWithoutClientFingerprint(t *testing.T) {
+	account := healthyGrokOAuthGatewayTestAccount(90140, "access-token")
+	account.Credentials["subscription_tier"] = "free"
+	c := newGrokCacheTestContext(90140)
+	c.Request.URL.Path = "/v1/chat/completions"
+	body := []byte(`{"model":"grok","tools":[{"type":"function","name":"view_image","parameters":{"type":"object"}}],"tool_choice":"auto"}`)
+
+	patched, err := applyGrokFreeRequestToolCacheRoute(c, body, body, account, "isolated-id")
+
+	require.NoError(t, err)
+	tools := gjson.GetBytes(patched, "tools").Array()
+	require.Len(t, tools, 3)
+	require.Equal(t, "view_image", tools[0].Get("name").String())
+	require.Equal(t, "web_search", tools[1].Get("type").String())
+	require.Equal(t, "x_search", tools[2].Get("type").String())
+}
+
+func TestGrokFreeClientToolCacheClaudeDesktopResponsesAutoOptIn(t *testing.T) {
+	account := healthyGrokOAuthGatewayTestAccount(90141, "access-token")
+	account.Credentials["subscription_tier"] = "free"
+	body := []byte(`{"model":"grok","tools":[{"type":"function","name":"Read","parameters":{"type":"object"}},{"type":"function","name":"Edit","parameters":{"type":"object"}}],"tool_choice":"auto"}`)
+
+	for _, xApp := range []string{"cli", "cli-bg"} {
+		t.Run(xApp, func(t *testing.T) {
+			c := newGrokCacheTestContext(90141)
+			// The desktop marker text is intentionally not required; CC Switch and
+			// Claude Desktop may change the descriptive User-Agent suffix.
+			c.Request.Header.Set("User-Agent", "claude-cli/2.1.215 (external, future-desktop, agent-sdk/0.3.215)")
+			c.Request.Header.Set("X-App", xApp)
+			c.Request.Header.Set("anthropic-client-platform", "desktop_app")
+			c.Request.Header.Set("X-Claude-Code-Session-Id", "desktop-session-1")
+
+			patched, err := applyGrokFreeRequestToolCacheRoute(c, body, body, account, "isolated-id")
+
+			require.NoError(t, err)
+			tools := gjson.GetBytes(patched, "tools").Array()
+			require.Len(t, tools, 4)
+			require.Equal(t, "Read", tools[0].Get("name").String())
+			require.Equal(t, "Edit", tools[1].Get("name").String())
+			require.Equal(t, "web_search", tools[2].Get("type").String())
+			require.Equal(t, "x_search", tools[3].Get("type").String())
+		})
+	}
+}
+
+func TestGrokFreeClientToolCacheClaudeDesktopFingerprintRequiresAllSignals(t *testing.T) {
+	account := healthyGrokOAuthGatewayTestAccount(90142, "access-token")
+	account.Credentials["subscription_tier"] = "free"
+	account.Extra = map[string]any{grokClientToolCacheOptInExtraKey: false}
+	body := []byte(`{"model":"grok","tools":[{"type":"function","name":"Read","parameters":{"type":"object"}}],"tool_choice":"auto"}`)
+
+	tests := []struct {
+		name     string
+		path     string
+		ua       string
+		xApp     string
+		platform string
+		session  string
+	}{
+		{
+			name:     "chat path",
+			path:     "/v1/chat/completions",
+			ua:       "claude-cli/2.1.215 (external, claude-desktop-3p, agent-sdk/0.3.215)",
+			xApp:     "cli",
+			platform: "desktop_app",
+			session:  "desktop-session-1",
+		},
+		{
+			name:     "compact responses path",
+			path:     "/v1/responses/compact",
+			ua:       "claude-cli/2.1.215 (external, claude-desktop-3p, agent-sdk/0.3.215)",
+			xApp:     "cli",
+			platform: "desktop_app",
+			session:  "desktop-session-1",
+		},
+		{
+			name:     "non claude cli user agent",
+			path:     "/v1/responses",
+			ua:       "Mozilla/5.0 (claude-desktop-3p)",
+			xApp:     "cli",
+			platform: "desktop_app",
+			session:  "desktop-session-1",
+		},
+		{
+			name:     "missing x app",
+			path:     "/v1/responses",
+			ua:       "claude-cli/2.1.215 (external, claude-desktop-3p, agent-sdk/0.3.215)",
+			platform: "desktop_app",
+			session:  "desktop-session-1",
+		},
+		{
+			name:     "wrong x app",
+			path:     "/v1/responses",
+			ua:       "claude-cli/2.1.215 (external, claude-desktop-3p, agent-sdk/0.3.215)",
+			xApp:     "desktop",
+			platform: "desktop_app",
+			session:  "desktop-session-1",
+		},
+		{
+			name:    "missing client platform",
+			path:    "/v1/responses",
+			ua:      "claude-cli/2.1.215 (external, claude-desktop-3p, agent-sdk/0.3.215)",
+			xApp:    "cli",
+			session: "desktop-session-1",
+		},
+		{
+			name:     "wrong client platform",
+			path:     "/v1/responses",
+			ua:       "claude-cli/2.1.215 (external, claude-desktop-3p, agent-sdk/0.3.215)",
+			xApp:     "cli",
+			platform: "web",
+			session:  "desktop-session-1",
+		},
+		{
+			name:     "missing session header",
+			path:     "/v1/responses",
+			ua:       "claude-cli/2.1.215 (external, claude-desktop-3p, agent-sdk/0.3.215)",
+			xApp:     "cli",
+			platform: "desktop_app",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			c := newGrokCacheTestContext(90142)
+			c.Request.URL.Path = tt.path
+			if tt.ua != "" {
+				c.Request.Header.Set("User-Agent", tt.ua)
+			}
+			if tt.xApp != "" {
+				c.Request.Header.Set("X-App", tt.xApp)
+			}
+			if tt.platform != "" {
+				c.Request.Header.Set("anthropic-client-platform", tt.platform)
+			}
+			if tt.session != "" {
+				c.Request.Header.Set("X-Claude-Code-Session-Id", tt.session)
+			}
+
+			patched, err := applyGrokFreeRequestToolCacheRoute(c, body, body, account, "isolated-id")
+
+			require.NoError(t, err)
+			require.JSONEq(t, string(body), string(patched))
+		})
+	}
+}
+
+func TestGrokFreeClientToolCacheExplicitRequestOptOut(t *testing.T) {
+	account := healthyGrokOAuthGatewayTestAccount(90144, "access-token")
+	account.Credentials["subscription_tier"] = "free"
+	body := []byte(`{"model":"grok","tools":[{"type":"function","name":"Read","parameters":{"type":"object"}}],"tool_choice":"auto"}`)
+
+	for _, value := range []string{"0", "false", "no", "off"} {
+		t.Run(value, func(t *testing.T) {
+			c := newGrokCacheTestContext(90144)
+			c.Request.URL.Path = "/v1/chat/completions"
+			c.Request.Header.Set(grokClientToolCacheOptInHeader, value)
+
+			patched, err := applyGrokFreeRequestToolCacheRoute(c, body, body, account, "isolated-id")
+
+			require.NoError(t, err)
+			require.JSONEq(t, string(body), string(patched))
+		})
+	}
+}
+
+func TestGrokFreeClientToolCacheClaudeDesktopAutoOptInDoesNotOverridePaidTier(t *testing.T) {
+	account := healthyGrokOAuthGatewayTestAccount(90143, "access-token")
+	account.Credentials["subscription_tier"] = "supergrok"
+	c := newGrokCacheTestContext(90143)
+	c.Request.Header.Set("User-Agent", "claude-cli/2.1.215 (external, claude-desktop-3p, agent-sdk/0.3.215)")
+	c.Request.Header.Set("X-App", "cli")
+	c.Request.Header.Set("anthropic-client-platform", "desktop_app")
+	c.Request.Header.Set("X-Claude-Code-Session-Id", "desktop-session-1")
+	body := []byte(`{"model":"grok","tools":[{"type":"function","name":"Read","parameters":{"type":"object"}}],"tool_choice":"auto"}`)
+
+	patched, err := applyGrokFreeRequestToolCacheRoute(c, body, body, account, "isolated-id")
+
+	require.NoError(t, err)
+	require.JSONEq(t, string(body), string(patched))
+}
+
+func TestGrokFreeRequestClientSearchFunctionUsesDefaultAccountPolicy(t *testing.T) {
+	account := healthyGrokOAuthGatewayTestAccount(9015, "access-token")
+	account.Credentials["subscription_tier"] = "free"
+	c := newGrokCacheTestContext(9015)
+	body := []byte(`{"model":"grok","tools":[{"type":"function","name":"view_image","parameters":{"type":"object"}},{"type":"function","name":"web_search","parameters":{"type":"object"}}],"tool_choice":"auto"}`)
+
+	patched, err := applyGrokFreeRequestToolCacheRoute(c, body, body, account, "isolated-id")
+
+	require.NoError(t, err)
+	tools := gjson.GetBytes(patched, "tools").Array()
+	require.Len(t, tools, 3)
+	require.Equal(t, "view_image", tools[0].Get("name").String())
+	require.Equal(t, "web_search", tools[1].Get("type").String())
+	require.Equal(t, "x_search", tools[2].Get("type").String())
+}
+
+func TestGrokFreeRequestToolChoiceNoneUsesSafeCacheRoute(t *testing.T) {
+	account := healthyGrokOAuthGatewayTestAccount(9016, "access-token")
+	account.Credentials["subscription_tier"] = "free"
+	c := newGrokCacheTestContext(9016)
+	body := []byte(`{"model":"grok","tools":[{"type":"function","name":"view_image","parameters":{"type":"object"}}],"tool_choice":"none"}`)
+
+	patched, err := applyGrokFreeRequestToolCacheRoute(c, body, body, account, "isolated-id")
+
+	require.NoError(t, err)
+	tools := gjson.GetBytes(patched, "tools").Array()
+	require.Len(t, tools, 3)
+	require.Equal(t, "view_image", tools[0].Get("name").String())
+	require.Equal(t, "web_search", tools[1].Get("type").String())
+	require.Equal(t, "x_search", tools[2].Get("type").String())
+	require.Equal(t, "none", gjson.GetBytes(patched, "tool_choice").String())
+}
+
+func TestApplyGrokCacheIdentityRecognizesResponsesLiteAdditionalTools(t *testing.T) {
+	intentBody := []byte(`{"model":"grok","input":[{"type":"additional_tools","tools":[{"type":"function","name":"lookup","parameters":{"type":"object"}}]},{"type":"message","role":"user","content":"hello"}]}`)
+	patchedBody := []byte(`{"model":"grok-4.5","tools":[{"type":"function","name":"lookup","parameters":{"type":"object"}}],"input":[{"type":"message","role":"user","content":"hello"}]}`)
+
+	patched, err := applyGrokResponsesCacheIdentity(patchedBody, intentBody, "isolated-id", true)
+
+	require.NoError(t, err)
+	tools := gjson.GetBytes(patched, "tools").Array()
+	require.Len(t, tools, 1)
+	require.Equal(t, "lookup", tools[0].Get("name").String())
+	require.False(t, gjson.GetBytes(patched, "tool_choice").Exists())
+	require.Equal(t, "isolated-id", gjson.GetBytes(patched, "prompt_cache_key").String())
+}
+
+func TestGrokFreeCacheRoutePreservesMixedSupportedToolsWithSearchIntent(t *testing.T) {
+	account := healthyGrokOAuthGatewayTestAccount(9012, "access-token")
+	account.Credentials["subscription_tier"] = "free"
+	intentBody := []byte(`{"model":"grok","tools":[{"type":"function","name":"view_image","parameters":{"type":"object"}},{"type":"shell"},{"type":"web_search"}],"tool_choice":"auto"}`)
+
+	body, err := applyGrokResponsesCacheIdentity(intentBody, intentBody, "isolated-id", true)
+	require.NoError(t, err)
+	body, err = applyGrokFreeMessagesFunctionToolCacheRoute(body, intentBody, account, "isolated-id")
+	require.NoError(t, err)
+
+	tools := gjson.GetBytes(body, "tools").Array()
+	require.Len(t, tools, 4)
+	require.Equal(t, "function", tools[0].Get("type").String())
+	require.Equal(t, "shell", tools[1].Get("type").String())
+	require.Equal(t, "web_search", tools[2].Get("type").String())
+	require.Equal(t, "x_search", tools[3].Get("type").String())
+}
+
+func TestGrokClientToolCacheOptInDoesNotOverridePaidTier(t *testing.T) {
+	account := healthyGrokOAuthGatewayTestAccount(9013, "access-token")
+	account.Credentials["subscription_tier"] = "supergrok"
+	account.Extra = map[string]any{grokClientToolCacheOptInExtraKey: true}
+	body := []byte(`{"model":"grok","tools":[{"type":"function","name":"view_image","parameters":{"type":"object"}}],"tool_choice":"auto"}`)
+
+	patched, err := applyGrokFreeMessagesFunctionToolCacheRoute(body, body, account, "isolated-id")
+
+	require.NoError(t, err)
+	require.JSONEq(t, string(body), string(patched))
+}
+
 func TestApplyGrokCacheIdentityRequiresPatchedFunctionTools(t *testing.T) {
 	account := healthyGrokOAuthGatewayTestAccount(902, "access-token")
 	account.Credentials["subscription_tier"] = "free"
@@ -260,7 +613,7 @@ func TestApplyGrokCacheIdentityRequiresPatchedFunctionTools(t *testing.T) {
 		{name: "missing tools", patchedBody: `{"model":"grok-4.5"}`},
 		{name: "empty tools", patchedBody: `{"model":"grok-4.5","tools":[]}`},
 		{name: "native tools only", patchedBody: `{"model":"grok-4.5","tools":[{"type":"web_search"}]}`},
-		{name: "unexpected patched tool", patchedBody: `{"model":"grok-4.5","tools":[{"type":"function","name":"lookup"},{"type":"mcp","name":"server"}]}`},
+		{name: "unexpected patched tool", patchedBody: `{"model":"grok-4.5","tools":[{"type":"function","name":"lookup"},{"type":"namespace","name":"server"}]}`},
 	}
 
 	for _, tt := range tests {
@@ -280,8 +633,7 @@ func TestApplyGrokCacheIdentityRequiresPatchedFunctionTools(t *testing.T) {
 }
 
 func TestGrokFreeMessagesFunctionToolCacheRouteRequiresKnownFreeTier(t *testing.T) {
-	// Include web_search as function to trigger native tool injection (pure client
-	// functions no longer trigger injection after #4486 fix).
+	// Include web_search as a function to also cover its conversion to a native tool.
 	intentBody := []byte(`{"model":"grok","tools":[{"type":"function","name":"lookup"},{"type":"function","name":"web_search"}],"tool_choice":"auto"}`)
 	tests := []struct {
 		name    string
diff --git a/backend/internal/service/openai_gateway_grok_chat_bridge.go b/backend/internal/service/openai_gateway_grok_chat_bridge.go
index 0b8f0e2d83..89ebb4049e 100644
--- a/backend/internal/service/openai_gateway_grok_chat_bridge.go
+++ b/backend/internal/service/openai_gateway_grok_chat_bridge.go
@@ -22,17 +22,23 @@ const (
 var grokChatResponsesBridgeTopLevelFields = map[string]struct{}{
 	"model":                 {},
 	"messages":              {},
+	"instructions":          {},
 	"stream":                {},
 	"stream_options":        {},
 	"max_tokens":            {},
 	"max_completion_tokens": {},
 	"temperature":           {},
 	"top_p":                 {},
+	"stop":                  {},
+	"reasoning_effort":      {},
 	"prompt_cache_key":      {},
 	"tools":                 {},
 	"tool_choice":           {},
 	"functions":             {},
 	"function_call":         {},
+	"parallel_tool_calls":   {},
+	"response_format":       {},
+	"service_tier":          {},
 }
 
 // grokChatResponsesBridgeEligibility deliberately accepts only request shapes
@@ -45,18 +51,49 @@ func grokChatResponsesBridgeEligibility(body []byte) (bool, string) {
 		return false, "invalid_json"
 	}
 
+	// These fields have no effect when explicitly set to JSON null. Accepting
+	// that common SDK representation keeps the request on the bridge path,
+	// while non-null values remain unsupported because the Responses converter
+	// cannot preserve their Chat Completions semantics.
 	for _, field := range []string{"stop", "reasoning_effort"} {
-		if _, exists := root[field]; exists {
+		if raw, exists := root[field]; exists && !grokChatJSONNull(raw) {
 			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["instructions"]; exists {
+		var instructions string
+		if !grokChatJSONNull(raw) && json.Unmarshal(raw, &instructions) != nil {
+			return false, "invalid_instructions"
 		}
 	}
-	if raw, exists := root["tool_choice"]; exists && !grokChatNullOrNone(raw) {
-		return false, "unsupported_tool_choice"
+	if raw, exists := root["response_format"]; exists {
+		var responseFormat map[string]json.RawMessage
+		if !grokChatJSONNull(raw) && (json.Unmarshal(raw, &responseFormat) != nil || responseFormat == nil) {
+			return false, "invalid_response_format"
+		}
+	}
+	if raw, exists := root["service_tier"]; exists {
+		var serviceTier string
+		if !grokChatJSONNull(raw) && json.Unmarshal(raw, &serviceTier) != nil {
+			return false, "invalid_service_tier"
+		}
+	}
+	if raw, exists := root["tools"]; exists {
+		if ok, reason := grokChatFunctionDeclarationsBridgeable(raw); !ok {
+			return false, reason
+		}
+	}
+	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 +115,12 @@ 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 +171,256 @@ 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", "reasoning_content", "tool_calls"); !ok {
+				return false, reason
+			}
+			reasoningContent := ""
+			if raw, exists := message["reasoning_content"]; exists {
+				if !grokChatJSONNull(raw) && json.Unmarshal(raw, &reasoningContent) != nil {
+					return false, "invalid_reasoning_content"
+				}
+			}
+			hasReasoningContent := strings.TrimSpace(reasoningContent) != ""
+			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 && !hasReasoningContent {
+					return false, "non_text_message_content"
+				}
+				continue
+			}
+			var content string
+			if json.Unmarshal(raw, &content) == nil {
+				if strings.TrimSpace(content) == "" && toolCallCount == 0 && !hasReasoningContent {
+					return false, "empty_message_content"
+				}
+				continue
+			}
+			if ok, reason := grokChatStructuredContentBridgeable(raw); !ok {
+				// The converter can still emit a standalone reasoning part when
+				// an otherwise empty content array accompanies reasoning_content.
+				// Do not broaden this exception to unsupported/malformed parts.
+				if !hasReasoningContent || reason != "empty_message_content" {
+					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", "index":
+			default:
+				return 0, "unsafe_tool_call_field_" + field
+			}
+		}
+		if rawIndex, exists := call["index"]; exists {
+			var index *int
+			if json.Unmarshal(rawIndex, &index) != nil || (index != nil && *index < 0) {
+				return 0, "invalid_tool_call_index"
+			}
+		}
+		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 +456,6 @@ 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 +464,34 @@ 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 grokChatJSONNull(raw json.RawMessage) bool {
+	return strings.TrimSpace(string(raw)) == "null"
+}
+
+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)
 }
 
@@ -268,6 +537,10 @@ func (s *OpenAIGatewayService) forwardGrokChatCompletionsViaResponses(
 	}
 	responsesReq.Model = upstreamModel
 	responsesReq.Stream = true
+	// Keep Chat and native Responses paths aligned for OpenAI-compatible
+	// service_tier aliases (for example, "fast" -> "priority"). Unknown
+	// values are omitted by the shared normalizer instead of reaching xAI.
+	normalizeResponsesRequestServiceTier(responsesReq)
 	// These fields are useful to Codex but are not needed by the Grok CLI
 	// protocol. Keep the bridge request as close as possible to native Grok.
 	responsesReq.Include = nil
@@ -277,18 +550,25 @@ 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..188e38f702 100644
--- a/backend/internal/service/openai_gateway_grok_chat_bridge_test.go
+++ b/backend/internal/service/openai_gateway_grok_chat_bridge_test.go
@@ -39,6 +39,31 @@ func TestGrokChatResponsesBridgeEligibility(t *testing.T) {
 			body: `{"model":"grok","messages":[{"role":"user","content":"hi"}],"stream":true,"stream_options":{"include_usage":true},"max_completion_tokens":256,"temperature":0.2,"top_p":0.9,"prompt_cache_key":"session","tools":[],"functions":null,"tool_choice":"none"}`,
 			want: true,
 		},
+		{
+			name: "Trae compatible fields",
+			body: `{"model":"grok","messages":[{"role":"user","content":"return json"}],"instructions":"Be concise","response_format":{"type":"json_object"},"service_tier":"fast","stop":null,"reasoning_effort":null}`,
+			want: true,
+		},
+		{
+			name: "Trae nullable SDK fields",
+			body: `{"model":"grok","messages":[{"role":"user","content":"hi"}],"instructions":null,"response_format":null,"service_tier":null,"stop":null,"reasoning_effort":null}`,
+			want: true,
+		},
+		{
+			name:   "invalid instructions fall back",
+			body:   `{"model":"grok","messages":[{"role":"user","content":"hi"}],"instructions":{"text":"invalid"}}`,
+			reason: "invalid_instructions",
+		},
+		{
+			name:   "invalid response format falls back",
+			body:   `{"model":"grok","messages":[{"role":"user","content":"hi"}],"response_format":"json_object"}`,
+			reason: "invalid_response_format",
+		},
+		{
+			name:   "invalid service tier falls back",
+			body:   `{"model":"grok","messages":[{"role":"user","content":"hi"}],"service_tier":1}`,
+			reason: "invalid_service_tier",
+		},
 		{
 			name:   "stop falls back",
 			body:   `{"model":"grok","messages":[{"role":"user","content":"hi"}],"stop":"done"}`,
@@ -75,15 +100,80 @@ 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: "Trae reasoning and indexed tool history bridges",
+			body: `{"model":"grok","messages":[{"role":"assistant","content":null,"reasoning_content":"I should call lookup","tool_calls":[{"index":0,"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"}}}]}`,
+			want: true,
+		},
+		{
+			name: "reasoning only assistant history bridges",
+			body: `{"model":"grok","messages":[{"role":"assistant","reasoning_content":"Prior reasoning"},{"role":"user","content":"continue"}]}`,
+			want: true,
+		},
+		{
+			name:   "invalid reasoning content falls back",
+			body:   `{"model":"grok","messages":[{"role":"assistant","reasoning_content":{"text":"invalid"}},{"role":"user","content":"continue"}]}`,
+			reason: "invalid_reasoning_content",
+		},
+		{
+			name:   "negative tool call index falls back",
+			body:   `{"model":"grok","messages":[{"role":"assistant","content":null,"tool_calls":[{"index":-1,"id":"call_lookup","type":"function","function":{"name":"lookup","arguments":"{}"}}]}]}`,
+			reason: "invalid_tool_call_index",
+		},
+		{
+			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 +190,9 @@ 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 +273,116 @@ 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 TestForwardGrokChatViaResponsesTraeCompatibilityFieldsKeepCacheRoute(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	firstTurnBody := []byte(`{"model":"grok","messages":[{"role":"user","content":"Find alpha"}],"instructions":"Return concise JSON","stream":false,"response_format":{"type":"json_object"},"service_tier":"fast","stop":null,"reasoning_effort":null,"tools":[{"type":"function","function":{"name":"lookup","description":"Lookup a value","parameters":{"type":"object","properties":{"key":{"type":"string"}},"required":["key"]}}}],"tool_choice":"auto","parallel_tool_calls":true}`)
+	body := []byte(`{"model":"grok","messages":[{"role":"user","content":"Find alpha"},{"role":"assistant","content":null,"reasoning_content":"I should use lookup","tool_calls":[{"index":0,"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"}],"instructions":"Return concise JSON","stream":false,"response_format":{"type":"json_object"},"service_tier":"fast","stop":null,"reasoning_effort":null,"tools":[{"type":"function","function":{"name":"lookup","description":"Lookup a value","parameters":{"type":"object","properties":{"key":{"type":"string"}},"required":["key"]}}}],"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.Set("api_key", &APIKey{ID: 7161})
+
+	account := grokChatBridgeTestAccount(716)
+	account.Credentials["subscription_tier"] = "free"
+	repo := &grokQuotaAccountRepo{mockAccountRepoForPlatform: &mockAccountRepoForPlatform{
+		accountsByID: map[int64]*Account{account.ID: account},
+	}}
+	upstream := &httpUpstreamRecorder{resp: grokChatBridgeCompletedResponse("resp_grok_chat_trae_compat", 12288)}
+	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, 12288, result.Usage.CacheReadInputTokens)
+	require.Equal(t, extendedTurnIdentity, gjson.GetBytes(upstream.lastBody, "prompt_cache_key").String())
+	require.Equal(t, extendedTurnIdentity, upstream.lastReq.Header.Get(grokConversationIDHeader))
+	require.Equal(t, "Return concise JSON", gjson.GetBytes(upstream.lastBody, "instructions").String())
+	require.Equal(t, "json_object", gjson.GetBytes(upstream.lastBody, "text.format.type").String())
+	require.Equal(t, "priority", gjson.GetBytes(upstream.lastBody, "service_tier").String())
+	require.False(t, gjson.GetBytes(upstream.lastBody, "stop").Exists())
+	require.False(t, gjson.GetBytes(upstream.lastBody, "reasoning").Exists())
+	require.Contains(t, gjson.GetBytes(upstream.lastBody, "input.1.content.0.text").String(), "<thinking>I should use lookup</thinking>")
+	require.Equal(t, "function_call", gjson.GetBytes(upstream.lastBody, "input.2.type").String())
+	require.Equal(t, "function_call_output", gjson.GetBytes(upstream.lastBody, "input.3.type").String())
+
+	tools := gjson.GetBytes(upstream.lastBody, "tools").Array()
+	require.Len(t, tools, 3)
+	require.Equal(t, "lookup", tools[0].Get("name").String())
+	require.Equal(t, "web_search", tools[1].Get("type").String())
+	require.Equal(t, "x_search", tools[2].Get("type").String())
+	require.Equal(t, int64(12288), gjson.Get(recorder.Body.String(), "usage.prompt_tokens_details.cached_tokens").Int())
+}
+
 func TestForwardGrokChatViaResponsesStreamingPropagatesCachedUsage(t *testing.T) {
 	gin.SetMode(gin.TestMode)
 
diff --git a/backend/internal/service/openai_gateway_grok_test.go b/backend/internal/service/openai_gateway_grok_test.go
index 1709e2485f..4bc6eb9b08 100644
--- a/backend/internal/service/openai_gateway_grok_test.go
+++ b/backend/internal/service/openai_gateway_grok_test.go
@@ -207,18 +207,27 @@ func TestPatchGrokResponsesBodyDropsToolChoiceWhenNoSupportedToolsRemain(t *test
 	require.False(t, gjson.GetBytes(patched, "tool_choice").Exists())
 }
 
-func TestPatchGrokResponsesBodyDropsCodexAdditionalToolsInputItems(t *testing.T) {
+func TestPatchGrokResponsesBodyPromotesCodexAdditionalTools(t *testing.T) {
 	t.Parallel()
 
 	body := []byte(`{
 		"model": "grok",
+		"tools": [
+			{"type": "function", "name": "existing", "description": "top-level wins"},
+			{"type": "web_search"}
+		],
+		"tool_choice": "auto",
 		"input": [
 			{
 				"type": "additional_tools",
 				"role": "developer",
 				"tools": [
-					{"type": "namespace", "name": "image_gen"},
-					{"type": "function", "name": "wait"}
+					{"type": "function", "name": "existing", "description": "duplicate carrier definition"},
+					{"type": "function", "name": "wait"},
+					{"type": "web_search"},
+					{"type": "shell"},
+					{"type": "custom", "name": "apply_patch"},
+					{"type": "namespace", "name": "collaboration"}
 				]
 			},
 			{
@@ -240,12 +249,235 @@ func TestPatchGrokResponsesBodyDropsCodexAdditionalToolsInputItems(t *testing.T)
 	require.Equal(t, "grok-4.5", gjson.GetBytes(patched, "model").String())
 	require.Equal(t, 2, len(gjson.GetBytes(patched, "input").Array()))
 	require.False(t, gjson.GetBytes(patched, `input.#(type=="additional_tools")`).Exists())
+	tools := gjson.GetBytes(patched, "tools").Array()
+	require.Len(t, tools, 4)
+	require.Equal(t, "existing", tools[0].Get("name").String())
+	require.Equal(t, "top-level wins", tools[0].Get("description").String())
+	require.Equal(t, "web_search", tools[1].Get("type").String())
+	require.Equal(t, "wait", tools[2].Get("name").String())
+	require.Equal(t, "shell", tools[3].Get("type").String())
+	require.False(t, gjson.GetBytes(patched, `tools.#(type=="custom")`).Exists())
+	require.False(t, gjson.GetBytes(patched, `tools.#(type=="namespace")`).Exists())
+	require.Equal(t, "auto", gjson.GetBytes(patched, "tool_choice").String())
 	require.Equal(t, "developer", gjson.GetBytes(patched, "input.0.role").String())
 	require.Equal(t, "system prompt", gjson.GetBytes(patched, "input.0.content.0.text").String())
 	require.Equal(t, "user", gjson.GetBytes(patched, "input.1.role").String())
 	require.Equal(t, "hello", gjson.GetBytes(patched, "input.1.content.0.text").String())
 }
 
+func TestForwardGrokResponsesCodexAdditionalToolsUsesMixedCacheIntent(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	body := []byte(`{
+		"model":"grok",
+		"stream":false,
+		"prompt_cache_key":"codex-session",
+		"input":[
+			{"type":"additional_tools","role":"developer","tools":[
+				{"type":"function","name":"lookup","description":"look up a key","parameters":{"type":"object"}},
+				{"type":"function","name":"web_search","description":"search","parameters":{"type":"object"}},
+				{"type":"custom","name":"apply_patch"},
+				{"type":"namespace","name":"collaboration"}
+			]},
+			{"type":"message","role":"user","content":[{"type":"input_text","text":"hello"}]}
+		]
+	}`)
+	recorder := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(recorder)
+	c.Request = httptest.NewRequest(http.MethodPost, "/v1/responses", bytes.NewReader(body))
+	c.Request.Header.Set(grokClientToolCacheOptInHeader, "prefer-cache")
+	c.Set("api_key", &APIKey{ID: 4501})
+
+	account := healthyGrokOAuthGatewayTestAccount(4501, "access-token")
+	account.Credentials["subscription_tier"] = "free"
+	repo := &grokQuotaAccountRepo{
+		mockAccountRepoForPlatform: &mockAccountRepoForPlatform{
+			accountsByID: map[int64]*Account{account.ID: account},
+		},
+	}
+	upstream := &httpUpstreamRecorder{resp: &http.Response{
+		StatusCode: http.StatusOK,
+		Header:     http.Header{"Content-Type": []string{"application/json"}},
+		Body: io.NopCloser(strings.NewReader(`{
+			"id":"resp_codex_lite","object":"response","model":"grok-4.5","status":"completed",
+			"output":[],"usage":{"input_tokens":10,"output_tokens":1}
+		}`)),
+	}}
+	svc := &OpenAIGatewayService{
+		httpUpstream:      upstream,
+		grokTokenProvider: NewGrokTokenProvider(repo, nil),
+		accountRepo:       repo,
+	}
+
+	result, err := svc.forwardGrokResponses(context.Background(), c, account, body, "grok", false, time.Now())
+
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.Equal(t, "resp_codex_lite", result.ResponseID)
+	require.False(t, gjson.GetBytes(upstream.lastBody, `input.#(type=="additional_tools")`).Exists())
+	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, "web_search", tools[1].Get("type").String())
+	require.Equal(t, "x_search", tools[2].Get("type").String())
+	require.False(t, gjson.GetBytes(upstream.lastBody, "tool_choice").Exists())
+	require.False(t, gjson.GetBytes(upstream.lastBody, `tools.#(type=="custom")`).Exists())
+	require.False(t, gjson.GetBytes(upstream.lastBody, `tools.#(type=="namespace")`).Exists())
+	identity := gjson.GetBytes(upstream.lastBody, "prompt_cache_key").String()
+	require.NotEmpty(t, identity)
+	require.Equal(t, identity, upstream.lastReq.Header.Get(grokConversationIDHeader))
+	require.Empty(t, upstream.lastReq.Header.Get(grokClientToolCacheOptInHeader))
+}
+
+func TestForwardGrokResponsesClaudeDesktopClientToolsUseCacheRoute(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	firstBody := []byte(`{
+		"model":"grok","stream":false,"instructions":"You are Claude Desktop.",
+		"tools":[
+			{"type":"function","name":"Read","parameters":{"type":"object"}},
+			{"type":"function","name":"Edit","parameters":{"type":"object"}},
+			{"type":"function","name":"WebSearch","parameters":{"type":"object"}},
+			{"type":"function","name":"mcp__workspace__bash","parameters":{"type":"object"}}
+		],
+		"input":[{"role":"user","content":[{"type":"input_text","text":"first turn"}]}]
+	}`)
+	secondBody := []byte(`{
+		"model":"grok","stream":false,"instructions":"You are Claude Desktop.",
+		"tools":[
+			{"type":"function","name":"Read","parameters":{"type":"object"}},
+			{"type":"function","name":"Edit","parameters":{"type":"object"}},
+			{"type":"function","name":"WebSearch","parameters":{"type":"object"}},
+			{"type":"function","name":"mcp__workspace__bash","parameters":{"type":"object"}}
+		],
+		"input":[
+			{"role":"user","content":[{"type":"input_text","text":"first turn"}]},
+			{"role":"assistant","content":[{"type":"output_text","text":"first answer"}]},
+			{"role":"user","content":[{"type":"input_text","text":"second turn"}]}
+		]
+	}`)
+
+	account := healthyGrokOAuthGatewayTestAccount(4504, "access-token")
+	account.Credentials["subscription_tier"] = "free"
+	repo := &grokQuotaAccountRepo{
+		mockAccountRepoForPlatform: &mockAccountRepoForPlatform{
+			accountsByID: map[int64]*Account{account.ID: account},
+		},
+	}
+	upstream := &httpUpstreamRecorder{responses: []*http.Response{
+		{
+			StatusCode: http.StatusOK,
+			Header:     http.Header{"Content-Type": []string{"application/json"}},
+			Body: io.NopCloser(strings.NewReader(`{
+				"id":"resp_claude_desktop_1","object":"response","model":"grok-4.5","status":"completed",
+				"output":[],"usage":{"input_tokens":30000,"output_tokens":10,"input_tokens_details":{"cached_tokens":0}}
+			}`)),
+		},
+		{
+			StatusCode: http.StatusOK,
+			Header:     http.Header{"Content-Type": []string{"application/json"}},
+			Body: io.NopCloser(strings.NewReader(`{
+				"id":"resp_claude_desktop_2","object":"response","model":"grok-4.5","status":"completed",
+				"output":[],"usage":{"input_tokens":30100,"output_tokens":12,"input_tokens_details":{"cached_tokens":28672}}
+			}`)),
+		},
+	}}
+	svc := &OpenAIGatewayService{
+		httpUpstream:      upstream,
+		grokTokenProvider: NewGrokTokenProvider(repo, nil),
+		accountRepo:       repo,
+	}
+
+	newContext := func(body []byte) *gin.Context {
+		recorder := httptest.NewRecorder()
+		c, _ := gin.CreateTestContext(recorder)
+		c.Request = httptest.NewRequest(http.MethodPost, "/v1/responses", bytes.NewReader(body))
+		c.Request.Header.Set("User-Agent", "claude-cli/2.1.215 (external, claude-desktop-3p, agent-sdk/0.3.215)")
+		c.Request.Header.Set("X-App", "cli")
+		c.Request.Header.Set("anthropic-client-platform", "desktop_app")
+		c.Request.Header.Set("X-Claude-Code-Session-Id", "claude-desktop-session")
+		c.Set("api_key", &APIKey{ID: 4504})
+		return c
+	}
+
+	first, err := svc.forwardGrokResponses(context.Background(), newContext(firstBody), account, firstBody, "grok", false, time.Now())
+	require.NoError(t, err)
+	second, err := svc.forwardGrokResponses(context.Background(), newContext(secondBody), account, secondBody, "grok", false, time.Now())
+	require.NoError(t, err)
+
+	require.Equal(t, 0, first.Usage.CacheReadInputTokens)
+	require.Equal(t, 28672, second.Usage.CacheReadInputTokens)
+	require.Len(t, upstream.bodies, 2)
+	require.Len(t, upstream.requests, 2)
+	for i := range upstream.bodies {
+		tools := gjson.GetBytes(upstream.bodies[i], "tools").Array()
+		require.Len(t, tools, 6)
+		require.Equal(t, "Read", tools[0].Get("name").String())
+		require.Equal(t, "Edit", tools[1].Get("name").String())
+		require.Equal(t, "WebSearch", tools[2].Get("name").String())
+		require.Equal(t, "mcp__workspace__bash", tools[3].Get("name").String())
+		require.Equal(t, "web_search", tools[4].Get("type").String())
+		require.Equal(t, "x_search", tools[5].Get("type").String())
+		require.False(t, gjson.GetBytes(upstream.bodies[i], "tool_choice").Exists())
+		require.Empty(t, upstream.requests[i].Header.Get("X-App"))
+		require.Empty(t, upstream.requests[i].Header.Get("anthropic-client-platform"))
+		require.Empty(t, upstream.requests[i].Header.Get("X-Claude-Code-Session-Id"))
+	}
+	firstIdentity := gjson.GetBytes(upstream.bodies[0], "prompt_cache_key").String()
+	secondIdentity := gjson.GetBytes(upstream.bodies[1], "prompt_cache_key").String()
+	require.NotEmpty(t, firstIdentity)
+	require.Equal(t, firstIdentity, secondIdentity)
+	require.Equal(t, firstIdentity, upstream.requests[0].Header.Get(grokConversationIDHeader))
+	require.Equal(t, secondIdentity, upstream.requests[1].Header.Get(grokConversationIDHeader))
+}
+
+func TestGrokResponsesCacheIdentityIncludesPromotedCodexTools(t *testing.T) {
+	c := newGrokCacheTestContext(4503)
+	lookupBody := []byte(`{"model":"grok","input":[{"type":"additional_tools","tools":[{"type":"function","name":"lookup","parameters":{"type":"object"}}]},{"type":"message","role":"user","content":"same prompt"}]}`)
+	readBody := []byte(`{"model":"grok","input":[{"type":"additional_tools","tools":[{"type":"function","name":"read_file","parameters":{"type":"object"}}]},{"type":"message","role":"user","content":"same prompt"}]}`)
+
+	patchedLookup, err := patchGrokResponsesBody(lookupBody, "grok-4.5")
+	require.NoError(t, err)
+	patchedRead, err := patchGrokResponsesBody(readBody, "grok-4.5")
+	require.NoError(t, err)
+
+	lookupIdentity := resolveGrokCacheIdentity(c, patchedLookup, "", "grok-4.5")
+	readIdentity := resolveGrokCacheIdentity(c, patchedRead, "", "grok-4.5")
+	require.NotEmpty(t, lookupIdentity)
+	require.NotEmpty(t, readIdentity)
+	require.NotEqual(t, lookupIdentity, readIdentity)
+}
+
+func TestCodexUnsupportedAdditionalToolsDoNotBecomeToolFreeCacheIntent(t *testing.T) {
+	body := []byte(`{
+		"model":"grok","tool_choice":"auto",
+		"input":[
+			{"type":"additional_tools","role":"developer","tools":[
+				{"type":"custom","name":"apply_patch"},
+				{"type":"namespace","name":"collaboration"}
+			]},
+			{"type":"message","role":"user","content":"hello"}
+		]
+	}`)
+	patched, err := patchGrokResponsesBody(body, "grok-4.5")
+	require.NoError(t, err)
+	require.False(t, gjson.GetBytes(patched, "tools").Exists())
+	require.False(t, gjson.GetBytes(patched, "tool_choice").Exists())
+
+	mixedCacheIntent := patched
+	patched, err = applyGrokResponsesCacheIdentity(patched, body, "isolated-id", true)
+	require.NoError(t, err)
+	account := healthyGrokOAuthGatewayTestAccount(4502, "access-token")
+	account.Credentials["subscription_tier"] = "free"
+	patched, err = applyGrokFreeRequestToolCacheRoute(nil, patched, mixedCacheIntent, account, "isolated-id")
+
+	require.NoError(t, err)
+	require.False(t, gjson.GetBytes(patched, "tools").Exists())
+	require.False(t, gjson.GetBytes(patched, "tool_choice").Exists())
+	require.Equal(t, "isolated-id", gjson.GetBytes(patched, "prompt_cache_key").String())
+}
+
 func TestBuildGrokResponsesRequestUsesAccountBaseURLAndBearerToken(t *testing.T) {
 	t.Setenv(xai.EnvAllowUnsafeURLOverrides, "true")
 
diff --git a/backend/internal/service/openai_ws_http_bridge.go b/backend/internal/service/openai_ws_http_bridge.go
index a84968061b..b140eeb689 100644
--- a/backend/internal/service/openai_ws_http_bridge.go
+++ b/backend/internal/service/openai_ws_http_bridge.go
@@ -196,12 +196,13 @@ func (s *OpenAIGatewayService) proxyOpenAIWSHTTPBridgeTurn(
 			releaseUpstreamCtx()
 			return nil, err
 		}
+		grokMixedCacheIntentBody := append([]byte(nil), body...)
 		body, err = applyGrokResponsesCacheIdentity(body, grokIntentSourceBody, grokCacheIdentity, account.IsGrokOAuth())
 		if err != nil {
 			releaseUpstreamCtx()
 			return nil, fmt.Errorf("apply grok prompt cache identity: %w", err)
 		}
-		body, err = applyGrokFreeMessagesFunctionToolCacheRoute(body, grokIntentSourceBody, account, grokCacheIdentity)
+		body, err = applyGrokFreeRequestToolCacheRoute(c, body, grokMixedCacheIntentBody, account, grokCacheIdentity)
 		if err != nil {
 			releaseUpstreamCtx()
 			return nil, fmt.Errorf("apply grok Free function-tool cache route: %w", err)
@@ -482,6 +483,10 @@ func resolveGrokWSCacheIdentity(c *gin.Context, account *Account, payload []byte
 		return "", err
 	}
 	upstreamModel := resolveGrokWSUpstreamModel(account, body, originalModel)
+	body, err = patchGrokResponsesBody(body, upstreamModel)
+	if err != nil {
+		return "", err
+	}
 	return resolveGrokCacheIdentity(c, body, "", upstreamModel), nil
 }
 
diff --git a/backend/internal/service/openai_ws_http_bridge_test.go b/backend/internal/service/openai_ws_http_bridge_test.go
index de2e463816..73f8d1f015 100644
--- a/backend/internal/service/openai_ws_http_bridge_test.go
+++ b/backend/internal/service/openai_ws_http_bridge_test.go
@@ -448,6 +448,78 @@ func TestProxyOpenAIWSHTTPBridgeTurnForGrokDefaultsEmptyModelTo45(t *testing.T)
 	require.Len(t, events, 2)
 }
 
+func TestProxyOpenAIWSHTTPBridgeTurnPromotesCodexAdditionalToolsForMixedCache(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	upstream := &httpUpstreamRecorder{resp: &http.Response{
+		StatusCode: http.StatusOK,
+		Header:     http.Header{"Content-Type": []string{"text/event-stream"}},
+		Body: io.NopCloser(strings.NewReader(strings.Join([]string{
+			`data: {"type":"response.created","response":{"id":"resp_grok_codex_lite","model":"grok-4.5"}}`,
+			"",
+			`data: {"type":"response.completed","response":{"id":"resp_grok_codex_lite","model":"grok-4.5","usage":{"input_tokens":4,"output_tokens":1}}}`,
+			"",
+		}, "\n"))),
+	}}
+	svc := &OpenAIGatewayService{
+		cfg:          &config.Config{Gateway: config.GatewayConfig{MaxLineSize: defaultMaxLineSize}},
+		httpUpstream: upstream,
+	}
+	account := &Account{
+		ID:          73,
+		Platform:    PlatformGrok,
+		Type:        AccountTypeOAuth,
+		Concurrency: 1,
+		Credentials: map[string]any{
+			"base_url":          xai.DefaultCLIBaseURL,
+			"subscription_tier": "free",
+		},
+	}
+	payload := []byte(`{
+		"type":"response.create","generate":true,"model":"grok","stream":true,
+		"input":[
+			{"type":"additional_tools","role":"developer","tools":[
+				{"type":"function","name":"lookup","parameters":{"type":"object"}},
+				{"type":"function","name":"web_search","parameters":{"type":"object"}},
+				{"type":"custom","name":"apply_patch"},
+				{"type":"namespace","name":"collaboration"}
+			]},
+			{"type":"message","role":"user","content":[{"type":"input_text","text":"hello"}]}
+		]
+	}`)
+	recorder := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(recorder)
+	c.Request = httptest.NewRequest(http.MethodGet, "/v1/responses", nil)
+	c.Request.Header.Set(grokClientToolCacheOptInHeader, "prefer-cache")
+	var events [][]byte
+
+	result, err := svc.proxyOpenAIWSHTTPBridgeTurn(
+		context.Background(), c, account, "access-token", payload, len(payload),
+		"grok", "", "", "", "isolated-ws-cache-id", 1,
+		func(message []byte) error {
+			events = append(events, append([]byte(nil), message...))
+			return nil
+		},
+	)
+
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.Len(t, events, 2)
+	require.False(t, gjson.GetBytes(upstream.lastBody, `input.#(type=="additional_tools")`).Exists())
+	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, "web_search", tools[1].Get("type").String())
+	require.Equal(t, "x_search", tools[2].Get("type").String())
+	require.False(t, gjson.GetBytes(upstream.lastBody, "tool_choice").Exists())
+	require.False(t, gjson.GetBytes(upstream.lastBody, `tools.#(type=="custom")`).Exists())
+	require.False(t, gjson.GetBytes(upstream.lastBody, `tools.#(type=="namespace")`).Exists())
+	require.Equal(t, "isolated-ws-cache-id", gjson.GetBytes(upstream.lastBody, "prompt_cache_key").String())
+	require.Equal(t, "isolated-ws-cache-id", upstream.lastReq.Header.Get(grokConversationIDHeader))
+	require.Empty(t, upstream.lastReq.Header.Get(grokClientToolCacheOptInHeader))
+}
+
 func TestProxyResponsesWebSocketFromClientForGrokUsesXAIHTTPBridge(t *testing.T) {
 	gin.SetMode(gin.TestMode)
 
diff --git a/frontend/src/components/account/EditAccountModal.vue b/frontend/src/components/account/EditAccountModal.vue
index c61ebf6050..df4838fd31 100644
--- a/frontend/src/components/account/EditAccountModal.vue
+++ b/frontend/src/components/account/EditAccountModal.vue
@@ -428,6 +428,26 @@
 
       </div>
 
+      <!-- Grok OAuth client-tool prompt cache opt-in -->
+      <div
+        v-if="account.platform === 'grok' && account.type === 'oauth'"
+        class="border-t border-gray-200 pt-4 dark:border-dark-600"
+      >
+        <div class="flex items-center justify-between gap-4">
+          <div class="min-w-0">
+            <label class="input-label mb-0">{{ t('admin.accounts.grokClientToolCache.title') }}</label>
+            <p class="mt-1 text-xs text-gray-500 dark:text-gray-400">
+              {{ t('admin.accounts.grokClientToolCache.hint') }}
+            </p>
+          </div>
+          <Toggle
+            v-model="grokClientToolCacheEnabled"
+            data-testid="grok-client-tool-cache-toggle"
+            :aria-label="t('admin.accounts.grokClientToolCache.title')"
+          />
+        </div>
+      </div>
+
       <!-- Grok OAuth Custom Upstream URL (仅改写转发端点，OAuth 授权/刷新不受影响) -->
       <div
         v-if="account.platform === 'grok' && account.type === 'oauth'"
@@ -2699,6 +2719,7 @@ const allowedModels = ref<string[]>([])
 const DEFAULT_POOL_MODE_RETRY_COUNT = 3
 const MAX_POOL_MODE_RETRY_COUNT = 10
 const DEFAULT_POOL_MODE_RETRY_STATUS_CODES = [401, 403, 429]
+const GROK_CLIENT_TOOL_CACHE_EXTRA_KEY = 'grok_client_tool_cache_enabled'
 const poolModeEnabled = ref(false)
 const poolModeRetryCount = ref(DEFAULT_POOL_MODE_RETRY_COUNT)
 const poolModeRetryStatusCodesInput = ref('')
@@ -2747,6 +2768,9 @@ const headerOverrideCapable = computed(
 // Grok OAuth 自定义上游地址（仅转发端点；OAuth 授权/令牌刷新不受影响）
 const grokOAuthCustomBaseUrlEnabled = ref(false)
 const grokOAuthBaseUrl = ref('')
+// Grok Free OAuth accounts use client-tool prompt caching by default. Keep an
+// explicit false in the account extra as the opt-out signal.
+const grokClientToolCacheEnabled = ref(true)
 
 const interceptWarmupRequests = ref(false)
 const autoPauseOnExpired = ref(false)
@@ -3402,6 +3426,14 @@ const syncFormFromAccount = (newAccount: Account | null) => {
   // Load Grok OAuth custom upstream URL state（存储的官方地址视同未定制）
   grokOAuthCustomBaseUrlEnabled.value = false
   grokOAuthBaseUrl.value = ''
+  const grokClientToolCacheSetting =
+    newAccount.platform === 'grok' && newAccount.type === 'oauth'
+      ? newAccount.extra?.[GROK_CLIENT_TOOL_CACHE_EXTRA_KEY]
+      : undefined
+  grokClientToolCacheEnabled.value =
+    newAccount.platform === 'grok' &&
+    newAccount.type === 'oauth' &&
+    (grokClientToolCacheSetting === undefined || grokClientToolCacheSetting === true)
   if (newAccount.platform === 'grok' && newAccount.type === 'oauth' && newAccount.credentials) {
     const grokCreds = newAccount.credentials as Record<string, unknown>
     if (isCustomGrokBaseUrl(grokCreds.base_url)) {
@@ -4288,6 +4320,14 @@ const handleSubmit = async () => {
       applyHeaderOverride(newCredentials, headerOverrideEnabled.value, headerOverrideRows.value, 'edit')
 
       updatePayload.credentials = newCredentials
+
+      const newExtra: Record<string, unknown> = {
+        ...((props.account.extra as Record<string, unknown>) || {})
+      }
+      // Persist both states so a disabled account remains opted out when the
+      // backend applies the default-enabled policy to missing values.
+      newExtra[GROK_CLIENT_TOOL_CACHE_EXTRA_KEY] = grokClientToolCacheEnabled.value
+      updatePayload.extra = newExtra
     }
 
     // OpenAI: 手动覆盖订阅档位 plan_type（Plus/Pro/Free）。仅 OAuth 非影子账号：
diff --git a/frontend/src/components/account/__tests__/EditAccountModal.grokUpstream.spec.ts b/frontend/src/components/account/__tests__/EditAccountModal.grokUpstream.spec.ts
index 310a370889..c96cd86d0c 100644
--- a/frontend/src/components/account/__tests__/EditAccountModal.grokUpstream.spec.ts
+++ b/frontend/src/components/account/__tests__/EditAccountModal.grokUpstream.spec.ts
@@ -67,7 +67,10 @@ const BaseDialogStub = defineComponent({
   template: '<div v-if="show"><slot /><slot name="footer" /></div>'
 })
 
-function buildGrokOAuthAccount(credentials: Record<string, unknown> = {}) {
+function buildGrokOAuthAccount(
+  credentials: Record<string, unknown> = {},
+  extra: Record<string, unknown> = {}
+) {
   return {
     id: 5,
     name: 'Grok OAuth',
@@ -80,7 +83,7 @@ function buildGrokOAuthAccount(credentials: Record<string, unknown> = {}) {
       ...credentials
     },
     credentials_status: { has_access_token: true, has_refresh_token: true },
-    extra: {},
+    extra,
     proxy_id: null,
     concurrency: 1,
     priority: 1,
@@ -225,4 +228,99 @@ describe('EditAccountModal Grok OAuth upstream config', () => {
       'x-xai-token-auth': 'xai-grok-cli'
     })
   })
+
+  it('shows the client-tool cache switch only for Grok OAuth accounts', () => {
+    const grokOAuthWrapper = mountModal(buildGrokOAuthAccount())
+    expect(grokOAuthWrapper.find('[data-testid="grok-client-tool-cache-toggle"]').exists()).toBe(true)
+
+    const grokAPIKeyWrapper = mountModal({
+      ...buildGrokOAuthAccount(),
+      type: 'apikey',
+      credentials: { api_key: 'xai-test', base_url: 'https://api.x.ai/v1' }
+    })
+    expect(grokAPIKeyWrapper.find('[data-testid="grok-client-tool-cache-toggle"]').exists()).toBe(false)
+
+    const openAIOAuthWrapper = mountModal({
+      ...buildGrokOAuthAccount(),
+      platform: 'openai'
+    })
+    expect(openAIOAuthWrapper.find('[data-testid="grok-client-tool-cache-toggle"]').exists()).toBe(false)
+  })
+
+  it('loads and disables client-tool caching while preserving unrelated extra fields', async () => {
+    const account = buildGrokOAuthAccount({}, {
+      grok_client_tool_cache_enabled: true,
+      custom_setting: 'keep-me'
+    })
+    updateAccountMock.mockResolvedValue(account)
+
+    const wrapper = mountModal(account)
+    const toggle = wrapper.get('[data-testid="grok-client-tool-cache-toggle"]')
+    expect(toggle.attributes('aria-checked')).toBe('true')
+
+    await toggle.trigger('click')
+    await wrapper.get('form#edit-account-form').trigger('submit.prevent')
+    await vi.waitFor(() => expect(updateAccountMock).toHaveBeenCalledTimes(1))
+
+    const payload = updateAccountMock.mock.calls[0]?.[1]
+    expect(payload?.extra?.custom_setting).toBe('keep-me')
+    expect(payload?.extra?.grok_client_tool_cache_enabled).toBe(false)
+  })
+
+  it('defaults client-tool caching on when the setting is missing and persists explicit true', async () => {
+    const account = buildGrokOAuthAccount({}, { custom_setting: 'keep-me' })
+    updateAccountMock.mockResolvedValue(account)
+
+    const wrapper = mountModal(account)
+    const toggle = wrapper.get('[data-testid="grok-client-tool-cache-toggle"]')
+    expect(toggle.attributes('aria-checked')).toBe('true')
+
+    await wrapper.get('form#edit-account-form').trigger('submit.prevent')
+    await vi.waitFor(() => expect(updateAccountMock).toHaveBeenCalledTimes(1))
+
+    const payload = updateAccountMock.mock.calls[0]?.[1]
+    expect(payload?.extra).toMatchObject({
+      grok_client_tool_cache_enabled: true,
+      custom_setting: 'keep-me'
+    })
+  })
+
+  it('keeps an explicit false opt-out when saving an untouched account', async () => {
+    const account = buildGrokOAuthAccount(
+      {},
+      {
+        grok_client_tool_cache_enabled: false,
+        custom_setting: 'keep-me'
+      }
+    )
+    updateAccountMock.mockResolvedValue(account)
+
+    const wrapper = mountModal(account)
+    const toggle = wrapper.get('[data-testid="grok-client-tool-cache-toggle"]')
+    expect(toggle.attributes('aria-checked')).toBe('false')
+
+    await wrapper.get('form#edit-account-form').trigger('submit.prevent')
+    await vi.waitFor(() => expect(updateAccountMock).toHaveBeenCalledTimes(1))
+
+    const payload = updateAccountMock.mock.calls[0]?.[1]
+    expect(payload?.extra).toMatchObject({
+      grok_client_tool_cache_enabled: false,
+      custom_setting: 'keep-me'
+    })
+  })
+
+  it('shows malformed cache settings as disabled so the UI matches the fail-closed backend', () => {
+    const account = buildGrokOAuthAccount(
+      {},
+      {
+        grok_client_tool_cache_enabled: 'true',
+        custom_setting: 'keep-me'
+      }
+    )
+
+    const wrapper = mountModal(account)
+    expect(
+      wrapper.get('[data-testid="grok-client-tool-cache-toggle"]').attributes('aria-checked')
+    ).toBe('false')
+  })
 })
diff --git a/frontend/src/i18n/locales/en/admin/accounts.ts b/frontend/src/i18n/locales/en/admin/accounts.ts
index 206c7c5172..9352f04c35 100644
--- a/frontend/src/i18n/locales/en/admin/accounts.ts
+++ b/frontend/src/i18n/locales/en/admin/accounts.ts
@@ -641,6 +641,10 @@ export default {
           official: 'Official API'
         }
       },
+      grokClientToolCache: {
+        title: 'Client Tool Cache (May Change Automatic Tool Selection)',
+        hint: 'For detected Grok Free OAuth accounts, this is enabled by default for client function tools such as Codex and Trae. Turn it off to opt out if the automatic tool-selection behavior is not acceptable.'
+      },
       autoPauseOnExpired: 'Auto Pause On Expired',
       autoPauseOnExpiredDesc: 'When enabled, the account will auto pause scheduling after it expires',
 	  autoPause5hThreshold: '5h Usage Threshold (%)',
diff --git a/frontend/src/i18n/locales/zh/admin/accounts.ts b/frontend/src/i18n/locales/zh/admin/accounts.ts
index 48da50175d..d493b7aeff 100644
--- a/frontend/src/i18n/locales/zh/admin/accounts.ts
+++ b/frontend/src/i18n/locales/zh/admin/accounts.ts
@@ -734,6 +734,10 @@ export default {
           official: '官方 API'
         }
       },
+      grokClientToolCache: {
+        title: '客户端工具缓存（可能改变自动工具选择）',
+        hint: '仅对已识别为 Free 的 Grok OAuth 账号生效，默认会为 Codex、Trae 等客户端函数工具请求启用上游提示缓存；如不接受自动工具选择行为，可关闭此开关退出。'
+      },
       autoPauseOnExpired: '过期自动暂停调度',
       autoPauseOnExpiredDesc: '启用后，账号过期将自动暂停调度',
 	  autoPause5hThreshold: '5h 用量阈值(%)',