diff --git a/backend/internal/service/openai_codex_model_metadata_test.go b/backend/internal/service/openai_codex_model_metadata_test.go
index b058fdc0df..558c621ce5 100644
--- a/backend/internal/service/openai_codex_model_metadata_test.go
+++ b/backend/internal/service/openai_codex_model_metadata_test.go
@@ -93,6 +93,83 @@ func TestBuildCodexModelsManifestForGroupUsesNoneForExplicitNonReasoningMetadata
 	require.Equal(t, []string{"none"}, effortsFromManifestModel(t, models[0]))
 }
 
+func TestBuildCodexModelsManifestForGroupAdvertisesSearchOnlyForChatBridgeRoutes(t *testing.T) {
+	t.Parallel()
+
+	newAccount := func(id int64, nativeResponses bool) Account {
+		return Account{
+			ID: id, Platform: PlatformOpenAI, Type: AccountTypeAPIKey,
+			Credentials: map[string]any{
+				"base_url":      "https://provider.example/v1",
+				"model_mapping": map[string]any{"company-coding-model": "company-coding-model"},
+			},
+			Extra: map[string]any{"openai_responses_supported": nativeResponses},
+		}
+	}
+
+	for _, tc := range []struct {
+		name     string
+		accounts []Account
+		want     bool
+	}{
+		{name: "chat bridge", accounts: []Account{newAccount(80, false)}, want: true},
+		{name: "native responses", accounts: []Account{newAccount(81, true)}, want: false},
+		{name: "mixed routes", accounts: []Account{newAccount(82, false), newAccount(83, true)}, want: false},
+	} {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			body, err := buildCodexModelsManifestForAccounts(
+				PlatformOpenAI, []string{"company-coding-model"}, tc.accounts, nil, true,
+			)
+			require.NoError(t, err)
+			models := decodeCodexManifestModels(t, body)
+			require.Len(t, models, 1)
+			require.Equal(t, tc.want, models[0]["supports_search_tool"])
+		})
+	}
+}
+
+func TestCompleteAPIKeyCodexManifestSearchCapabilityPreservesUpstreamAndFailsClosed(t *testing.T) {
+	t.Parallel()
+
+	nativeAccount := &Account{
+		Platform: PlatformOpenAI,
+		Type:     AccountTypeAPIKey,
+		Credentials: map[string]any{
+			"base_url": "https://provider.example/v1",
+		},
+		Extra: map[string]any{"openai_responses_supported": true},
+	}
+	body, err := completeAPIKeyCodexModelsManifestMetadata([]byte(`{"models":[
+		{"slug":"explicit","supports_search_tool":true},
+		{"slug":"missing"}
+	]}`), true, nativeAccount)
+	require.NoError(t, err)
+	models := decodeCodexManifestModels(t, body)
+	require.Equal(t, true, models[0]["supports_search_tool"])
+	require.Equal(t, false, models[1]["supports_search_tool"])
+
+	chatAccount := &Account{
+		Platform: PlatformOpenAI,
+		Type:     AccountTypeAPIKey,
+		Credentials: map[string]any{
+			"base_url": "https://provider.example/v1",
+		},
+		Extra: map[string]any{"openai_responses_supported": false},
+	}
+	body, err = completeAPIKeyCodexModelsManifestMetadata(
+		[]byte(`{"models":[
+			{"slug":"explicit-disabled","supports_search_tool":false},
+			{"slug":"generated"}
+		]}`), true, chatAccount,
+	)
+	require.NoError(t, err)
+	models = decodeCodexManifestModels(t, body)
+	require.Equal(t, false, models[0]["supports_search_tool"])
+	require.Equal(t, true, models[1]["supports_search_tool"])
+}
+
 // Scenario: multiple schedulable accounts advertise only their shared capabilities.
 func TestBuildCodexModelsManifestForGroupIntersectsSyncedAccountMetadata(t *testing.T) {
 	t.Parallel()
diff --git a/backend/internal/service/openai_codex_models_service.go b/backend/internal/service/openai_codex_models_service.go
index 6c97eb9b84..d1abc54e01 100644
--- a/backend/internal/service/openai_codex_models_service.go
+++ b/backend/internal/service/openai_codex_models_service.go
@@ -734,7 +734,7 @@ func claudeCodexDisplayName(modelID string) string {
 // routed through a custom provider. The response is also suitable for saving
 // as model_catalog_json in clients that do not refresh custom-provider catalogs.
 func BuildCodexModelsManifest(modelIDs []string) ([]byte, error) {
-	return buildCodexModelsManifest(modelIDs, nil, nil, nil)
+	return buildCodexModelsManifest(modelIDs, nil, nil, nil, nil)
 }
 
 // BuildCodexModelsManifestForGroup derives input capabilities from the
@@ -789,6 +789,7 @@ func buildCodexModelsManifestForAccounts(
 	compositeRoutesAvailable bool,
 ) ([]byte, error) {
 	imageInputModels := make(map[string]bool, len(modelIDs))
+	searchToolModels := make(map[string]bool, len(modelIDs))
 	metadataModels := codexCatalogMetadataModels(
 		effectivePlatform,
 		modelIDs,
@@ -808,6 +809,15 @@ func buildCodexModelsManifestForAccounts(
 		) {
 			imageInputModels[modelID] = true
 		}
+		if groupCodexModelSupportsSearchTool(
+			effectivePlatform,
+			modelID,
+			accounts,
+			compositeRoutes,
+			compositeRoutesAvailable,
+		) {
+			searchToolModels[modelID] = true
+		}
 		if metadata, ok := groupCodexModelMetadata(
 			effectivePlatform,
 			modelID,
@@ -818,12 +828,13 @@ func buildCodexModelsManifestForAccounts(
 			modelMetadata[modelID] = metadata
 		}
 	}
-	return buildCodexModelsManifest(modelIDs, imageInputModels, metadataModels, modelMetadata)
+	return buildCodexModelsManifest(modelIDs, imageInputModels, searchToolModels, metadataModels, modelMetadata)
 }
 
 func buildCodexModelsManifest(
 	modelIDs []string,
 	imageInputModels map[string]bool,
+	searchToolModels map[string]bool,
 	metadataModels map[string]string,
 	modelMetadata map[string]codexModelMetadataOverride,
 ) ([]byte, error) {
@@ -850,6 +861,7 @@ func buildCodexModelsManifest(
 		if imageInputModels[modelID] {
 			descriptor.InputModalities = []string{"text", "image"}
 		}
+		descriptor.SupportsSearchTool = searchToolModels[modelID]
 		if metadata, ok := modelMetadata[modelID]; ok {
 			applyUpstreamModelMetadataToCodexDescriptor(&descriptor, metadata)
 		}
@@ -1005,6 +1017,52 @@ func groupCodexModelSupportsImageInput(
 	return candidates > 0
 }
 
+// groupCodexModelSupportsSearchTool advertises client-side tool discovery only
+// when every account that may serve the model uses the gateway's Responses to
+// Chat Completions bridge. Native Responses routes must declare the capability
+// in their upstream Codex manifest instead of having it inferred here.
+func groupCodexModelSupportsSearchTool(
+	platform string,
+	modelID string,
+	accounts []Account,
+	compositeRoutes []CompositeModelRoute,
+	compositeRoutesAvailable bool,
+) bool {
+	modelID = strings.TrimSpace(modelID)
+	if modelID == "" {
+		return false
+	}
+	upstreamModel := modelID
+	if platform == PlatformComposite {
+		var resolved bool
+		platform, upstreamModel, resolved = resolveCodexCompositeModelTarget(
+			modelID,
+			accounts,
+			compositeRoutes,
+			compositeRoutesAvailable,
+		)
+		if !resolved {
+			return false
+		}
+	}
+	if platform != PlatformOpenAI {
+		return false
+	}
+
+	candidates := 0
+	for i := range accounts {
+		account := &accounts[i]
+		if account.Platform != platform || !account.IsModelSupported(upstreamModel) {
+			continue
+		}
+		candidates++
+		if !shouldForwardOpenAIResponsesViaRawChatCompletions(account) {
+			return false
+		}
+	}
+	return candidates > 0
+}
+
 func resolveCodexCompositeModelTarget(
 	modelID string,
 	accounts []Account,
@@ -1939,7 +1997,13 @@ func convertOpenAIModelListToCodexManifestForAccount(body []byte, account *Accou
 			imageInputModels[modelID] = true
 		}
 	}
-	converted, err := buildCodexModelsManifest(modelIDs, imageInputModels, nil, nil)
+	searchToolModels := make(map[string]bool, len(modelIDs))
+	if shouldForwardOpenAIResponsesViaRawChatCompletions(account) {
+		for _, modelID := range modelIDs {
+			searchToolModels[modelID] = true
+		}
+	}
+	converted, err := buildCodexModelsManifest(modelIDs, imageInputModels, searchToolModels, nil, nil)
 	if err != nil {
 		return body
 	}
@@ -2141,6 +2205,7 @@ func completeAPIKeyCodexModelsManifestMetadata(body []byte, completeAll bool, ac
 		}
 
 		descriptor := newConfiguredCodexModelDescriptor(slug)
+		descriptor.SupportsSearchTool = shouldForwardOpenAIResponsesViaRawChatCompletions(account)
 		if accountCodexModelSupportsImageInput(account, slug) {
 			descriptor.InputModalities = []string{"text", "image"}
 		}