diff --git a/api/controllers/web/human_input_form.py b/api/controllers/web/human_input_form.py
index 775e802a70c..bd2b9a56efc 100644
--- a/api/controllers/web/human_input_form.py
+++ b/api/controllers/web/human_input_form.py
@@ -24,7 +24,7 @@ from extensions.ext_database import db
 from fields.base import ResponseModel
 from libs.helper import RateLimiter, dump_response, extract_remote_ip, to_timestamp
 from models.account import TenantStatus
-from models.model import App, Site
+from models.model import App, AppMode, Site
 from repositories.factory import DifyAPIRepositoryFactory
 from services.feature_service import FeatureService
 from services.human_input_file_upload_service import HumanInputFileUploadService
@@ -207,6 +207,7 @@ class HumanInputFormApi(Resource):
                 site=WebAppSiteResponse.from_app_site(
                     tenant=tenant,
                     app_model=app_model,
+                    mode=AppMode.value_of(app_model.mode),
                     site=site,
                     end_user_id=None,
                     features=features,
diff --git a/api/controllers/web/site.py b/api/controllers/web/site.py
index f6c4af013a1..1d9a01dcf4c 100644
--- a/api/controllers/web/site.py
+++ b/api/controllers/web/site.py
@@ -14,7 +14,7 @@ from extensions.storage.storage_type import StorageType
 from fields.base import ResponseModel
 from libs.helper import build_icon_url
 from models.account import Tenant, TenantStatus
-from models.model import App, EndUser, IconType, Site
+from models.model import App, AppMode, EndUser, IconType, Site
 from services.feature_service import FeatureModel, FeatureService
 from services.file_service import FileService
 
@@ -67,6 +67,7 @@ class WebAppCustomConfigResponse(ResponseModel):
 
 class WebAppSiteResponse(ResponseModel):
     app_id: str
+    mode: AppMode
     end_user_id: str | None = None
     enable_site: bool
     site: WebSiteResponse
@@ -83,6 +84,7 @@ class WebAppSiteResponse(ResponseModel):
         *,
         tenant: Tenant,
         app_model: App,
+        mode: AppMode,
         site: Site,
         end_user_id: str | None,
         features: FeatureModel,
@@ -109,6 +111,7 @@ class WebAppSiteResponse(ResponseModel):
 
         return cls(
             app_id=app_model.id,
+            mode=mode,
             end_user_id=end_user_id,
             enable_site=app_model.enable_site,
             site=site_response,
@@ -167,6 +170,7 @@ class AppSiteApi(WebApiResource):
         return WebAppSiteResponse.from_app_site(
             tenant=tenant,
             app_model=app_model,
+            mode=AppMode.value_of(app_model.mode_compatible_with_agent_with_session(session=db.session())),
             site=site,
             end_user_id=end_user.id,
             features=features,
diff --git a/api/openapi/markdown/web-openapi.md b/api/openapi/markdown/web-openapi.md
index 09c6842329c..c5fe79b60e5 100644
--- a/api/openapi/markdown/web-openapi.md
+++ b/api/openapi/markdown/web-openapi.md
@@ -965,6 +965,12 @@ Returns Server-Sent Events stream.
 | ---- | ---- | ----------- | -------- |
 | tool_icons | object | Tool icon metadata keyed by tool name | No |
 
+#### AppMode
+
+| Name | Type | Description | Required |
+| ---- | ---- | ----------- | -------- |
+| AppMode | string |  |  |
+
 #### AppPermissionQuery
 
 | Name | Type | Description | Required |
@@ -1646,6 +1652,7 @@ in form definition, or a variable while the workflow is running.
 | custom_config | [WebAppCustomConfigResponse](#webappcustomconfigresponse) |  | No |
 | enable_site | boolean |  | Yes |
 | end_user_id | string |  | No |
+| mode | [AppMode](#appmode) |  | Yes |
 | model_config | [WebModelConfigResponse](#webmodelconfigresponse) |  | No |
 | plan | string |  | Yes |
 | site | [WebSiteResponse](#websiteresponse) |  | Yes |
diff --git a/api/tests/test_containers_integration_tests/controllers/web/test_site.py b/api/tests/test_containers_integration_tests/controllers/web/test_site.py
index 7f4fd45d037..1e4d5aba030 100644
--- a/api/tests/test_containers_integration_tests/controllers/web/test_site.py
+++ b/api/tests/test_containers_integration_tests/controllers/web/test_site.py
@@ -97,6 +97,7 @@ class TestAppSiteApi:
         assert result["end_user_id"] == end_user.id
         assert result["plan"] == "basic"
         assert result["enable_site"] is True
+        assert result["mode"] == AppMode.CHAT
 
     @patch("controllers.web.site.FileService.get_file_presigned_url")
     @patch("controllers.web.site.FeatureService.get_features")
@@ -178,6 +179,7 @@ class TestWebAppSiteResponse:
         response = WebAppSiteResponse.from_app_site(
             tenant=tenant,
             app_model=app_model,
+            mode=AppMode.CHAT,
             site=_site_model(app_id=app_model.id),
             end_user_id="eu-1",
             features=FeatureModel(can_replace_logo=False, webapp_copyright_enabled=True),
@@ -185,6 +187,7 @@ class TestWebAppSiteResponse:
         )
 
         assert response.app_id == app_model.id
+        assert response.mode == AppMode.CHAT
         assert response.end_user_id == "eu-1"
         assert response.enable_site is True
         assert response.plan == "basic"
@@ -209,6 +212,7 @@ class TestWebAppSiteResponse:
         response = WebAppSiteResponse.from_app_site(
             tenant=tenant,
             app_model=app_model,
+            mode=AppMode.CHAT,
             site=site,
             end_user_id=None,
             features=FeatureModel(can_replace_logo=False, webapp_copyright_enabled=True),
@@ -236,6 +240,7 @@ class TestWebAppSiteResponse:
         response = WebAppSiteResponse.from_app_site(
             tenant=tenant,
             app_model=app_model,
+            mode=AppMode.CHAT,
             site=_site_model(app_id=app_model.id),
             end_user_id="eu-1",
             features=FeatureModel(can_replace_logo=True, webapp_copyright_enabled=True),
diff --git a/api/tests/unit_tests/controllers/web/test_human_input_form.py b/api/tests/unit_tests/controllers/web/test_human_input_form.py
index 3408e3049d1..042cb30a98e 100644
--- a/api/tests/unit_tests/controllers/web/test_human_input_form.py
+++ b/api/tests/unit_tests/controllers/web/test_human_input_form.py
@@ -163,6 +163,7 @@ def test_get_form_includes_site(monkeypatch: pytest.MonkeyPatch, app: Flask, dat
     assert body["expiration_time"] == int(expiration_time.timestamp())
     assert body["site"] == {
         "app_id": app_model.id,
+        "mode": "chat",
         "end_user_id": None,
         "enable_site": True,
         "site": {
@@ -383,6 +384,7 @@ def test_get_form_allows_backstage_token(monkeypatch: pytest.MonkeyPatch, app: F
     assert body["expiration_time"] == int(expiration_time.timestamp())
     assert body["site"] == {
         "app_id": app_model.id,
+        "mode": "chat",
         "end_user_id": None,
         "enable_site": True,
         "site": {
diff --git a/api/tests/unit_tests/controllers/web/test_site.py b/api/tests/unit_tests/controllers/web/test_site.py
index 1c2a403994f..f7a44afad6a 100644
--- a/api/tests/unit_tests/controllers/web/test_site.py
+++ b/api/tests/unit_tests/controllers/web/test_site.py
@@ -3,7 +3,42 @@ from unittest.mock import MagicMock, patch
 from configs import dify_config
 from controllers.web import site as site_module
 from extensions.storage.storage_type import StorageType
-from models.model import IconType, Site
+from models.model import AppMode, IconType, Site
+from services.feature_service import FeatureModel
+
+
+def test_app_site_api_returns_legacy_agent_compatible_mode() -> None:
+    app_model = MagicMock()
+    app_model.id = "app-id"
+    app_model.tenant_id = "tenant-id"
+    app_model.tenant = MagicMock(id="tenant-id", status="normal")
+    app_model.mode_compatible_with_agent_with_session.return_value = AppMode.AGENT_CHAT
+    end_user = MagicMock(id="end-user-id")
+    site = MagicMock(spec=Site)
+    response = MagicMock()
+    response.model_dump.return_value = {"mode": AppMode.AGENT_CHAT}
+
+    with (
+        patch.object(site_module, "db") as mock_db,
+        patch.object(site_module.FeatureService, "get_features", return_value=FeatureModel(can_replace_logo=False)),
+        patch.object(site_module, "_build_site_icon_url", return_value=None),
+        patch.object(site_module.WebAppSiteResponse, "from_app_site", return_value=response) as mock_from_app_site,
+    ):
+        mock_db.session.scalar.return_value = site
+        result = site_module.AppSiteApi().get(app_model, end_user)
+
+    assert result["mode"] == AppMode.AGENT_CHAT
+    app_model.mode_compatible_with_agent_with_session.assert_called_once_with(session=mock_db.session())
+    mock_from_app_site.assert_called_once_with(
+        tenant=app_model.tenant,
+        app_model=app_model,
+        mode=AppMode.AGENT_CHAT,
+        site=site,
+        end_user_id=end_user.id,
+        features=FeatureModel(can_replace_logo=False),
+        can_replace_logo=False,
+        icon_url=None,
+    )
 
 
 def test_build_site_icon_url_uses_s3_presigned_url() -> None:
diff --git a/packages/contracts/generated/api/web/types.gen.ts b/packages/contracts/generated/api/web/types.gen.ts
index d832ca3d98a..8812b164b9e 100644
--- a/packages/contracts/generated/api/web/types.gen.ts
+++ b/packages/contracts/generated/api/web/types.gen.ts
@@ -43,6 +43,16 @@ export type AppMetaResponse = {
   }
 }
 
+export type AppMode =
+  | 'advanced-chat'
+  | 'agent'
+  | 'agent-chat'
+  | 'channel'
+  | 'chat'
+  | 'completion'
+  | 'rag-pipeline'
+  | 'workflow'
+
 export type AppPermissionQuery = {
   appId: string
 }
@@ -575,6 +585,7 @@ export type WebAppSiteResponse = {
   custom_config?: WebAppCustomConfigResponse | null
   enable_site: boolean
   end_user_id?: string | null
+  mode: AppMode
   model_config?: WebModelConfigResponse | null
   plan: string
   site: WebSiteResponse
diff --git a/packages/contracts/generated/api/web/zod.gen.ts b/packages/contracts/generated/api/web/zod.gen.ts
index 0e1cd8fc76d..59eed414d4b 100644
--- a/packages/contracts/generated/api/web/zod.gen.ts
+++ b/packages/contracts/generated/api/web/zod.gen.ts
@@ -39,6 +39,20 @@ export const zAppMetaResponse = z.object({
   tool_icons: z.record(z.string(), z.unknown()).optional(),
 })
 
+/**
+ * AppMode
+ */
+export const zAppMode = z.enum([
+  'advanced-chat',
+  'agent',
+  'agent-chat',
+  'channel',
+  'chat',
+  'completion',
+  'rag-pipeline',
+  'workflow',
+])
+
 /**
  * AppPermissionQuery
  */
@@ -884,6 +898,7 @@ export const zWebAppSiteResponse = z.object({
   custom_config: zWebAppCustomConfigResponse.nullish(),
   enable_site: z.boolean(),
   end_user_id: z.string().nullish(),
+  mode: zAppMode,
   model_config: zWebModelConfigResponse.nullish(),
   plan: z.string(),
   site: zWebSiteResponse,