Merge release-1.11.1 into main

Author: erichare

docs/docs/Support/troubleshooting.mdx

@@ -113,7 +113,8 @@ To pin FastAPI in an environment where Langflow is already installed:
 uv pip install "fastapi<0.140"
 ```
 
-Langflow version 1.11.1 constrains FastAPI to `<0.140.0`, so a new install of Langflow version `>=1.11.1` does not require this pin.
+Langflow version 1.11.1 resolves a compatible FastAPI 0.140.x and `fastapi-pagination` 0.15.16 pair on a new install, so it does not require this pin.
+If you constrain these dependencies yourself, use `fastapi-pagination>=0.15.16` with `fastapi>=0.140.5`.
 
 ## Langflow Desktop installation issues
 
@@ -778,4 +779,4 @@ For more information, see [Workarounds for Intel Mac users](./macos-support-matr
 ## See also
 
 - [Langflow GitHub Issues and Discussions](/contributing-github-issues)
-- [Langflow telemetry](/contributing-telemetry)
+- [Langflow telemetry](/contributing-telemetry)

docs/versioned_docs/version-1.11.0/Support/troubleshooting.mdx

@@ -113,7 +113,8 @@ To pin FastAPI in an environment where Langflow is already installed:
 uv pip install "fastapi<0.140"
 ```
 
-Langflow version 1.11.1 constrains FastAPI to `<0.140.0`, so a new install of Langflow version `>=1.11.1` does not require this pin.
+Langflow version 1.11.1 resolves a compatible FastAPI 0.140.x and `fastapi-pagination` 0.15.16 pair on a new install, so it does not require this pin.
+If you constrain these dependencies yourself, use `fastapi-pagination>=0.15.16` with `fastapi>=0.140.5`.
 
 ## Langflow Desktop installation issues
 
@@ -778,4 +779,4 @@ For more information, see [Workarounds for Intel Mac users](./macos-support-matr
 ## See also
 
 - [Langflow GitHub Issues and Discussions](/contributing-github-issues)
-- [Langflow telemetry](/contributing-telemetry)
+- [Langflow telemetry](/contributing-telemetry)

src/backend/base/langflow/api/utils/mcp/config_utils.py

@@ -7,6 +7,7 @@
 from fastapi import HTTPException
 from lfx.base.mcp.constants import MAX_MCP_SERVER_NAME_LENGTH
 from lfx.base.mcp.util import sanitize_mcp_name
+from lfx.base.mcp.uvx import mcp_sdk_constraint_args
 from lfx.log import logger
 from lfx.services.deps import get_settings_service
 from sqlmodel import select
@@ -23,6 +24,19 @@
 ALL_INTERFACES_HOST = "0.0.0.0"  # noqa: S104
 
 
+def mcp_server_config_uses_current_uvx_constraint(server_config: dict, package: str) -> bool:
+    """Return whether a generated uvx config uses the current SDK constraint and package."""
+    if server_config.get("command") != "uvx":
+        return False
+
+    args = server_config.get("args")
+    if not isinstance(args, list):
+        return False
+
+    expected_prefix = [*mcp_sdk_constraint_args(), package]
+    return args[: len(expected_prefix)] == expected_prefix
+
+
 class MCPServerValidationResult:
     """Represents the result of an MCP server validation check.
 
@@ -355,26 +369,27 @@ async def auto_configure_starter_projects_mcp(session):
                     operation="create",
                 )
 
-                # Skip if server already exists for this starter projects folder
+                # Skip if the server already has the expected URL and uvx SDK constraint.
                 if validation_result.should_skip:
-                    # Check if the URL needs updating (e.g., server port changed at restart)
                     expected_url = await get_project_streamable_http_url(user_starter_folder.id)
                     existing_config = validation_result.existing_config or {}
                     existing_args = existing_config.get("args", [])
                     existing_urls = await extract_urls_from_strings(existing_args)
 
-                    if any(expected_url == url for url in existing_urls):
+                    if mcp_server_config_uses_current_uvx_constraint(existing_config, "mcp-proxy") and any(
+                        expected_url == url for url in existing_urls
+                    ):
                         await logger.adebug(
                             f"MCP server '{validation_result.server_name}' already exists and is correctly "
                             f"configured for user {user.username}'s starter projects (project ID: "
                             f"{user_starter_folder.id}), skipping"
                         )
                         continue  # Skip this user since server already exists for the same project
 
-                    # URL has changed (e.g., server restarted on a different port), fall through to update
                     await logger.adebug(
                         f"MCP server '{validation_result.server_name}' exists for user {user.username}'s "
-                        f"starter projects but URL has changed (was: {existing_urls}, now: {expected_url}), updating"
+                        f"starter projects but its generated configuration is stale "
+                        f"(URLs: {existing_urls}, expected URL: {expected_url}), updating"
                     )
 
                 server_name = validation_result.server_name
@@ -413,6 +428,7 @@ async def auto_configure_starter_projects_mcp(session):
                 if default_auth.get("auth_type", "none") == "apikey":
                     command = "uvx"
                     args = [
+                        *mcp_sdk_constraint_args(),
                         "mcp-proxy",
                         "--transport",
                         "streamablehttp",
@@ -429,6 +445,7 @@ async def auto_configure_starter_projects_mcp(session):
                     # No authentication - direct connection
                     command = "uvx"
                     args = [
+                        *mcp_sdk_constraint_args(),
                         "mcp-proxy",
                         "--transport",
                         "streamablehttp",

src/backend/base/langflow/api/v1/mcp_projects.py

@@ -19,6 +19,7 @@
 from fastapi.responses import HTMLResponse, JSONResponse
 from lfx.base.mcp.constants import MAX_MCP_SERVER_NAME_LENGTH
 from lfx.base.mcp.util import sanitize_mcp_name
+from lfx.base.mcp.uvx import mcp_sdk_constraint_args
 from lfx.log import logger
 from lfx.services.deps import get_settings_service, session_scope
 from lfx.services.mcp_composer.service import (
@@ -880,6 +881,7 @@ async def install_mcp_config(
             settings = get_settings_service().settings
             command = "uvx"
             args = [
+                *mcp_sdk_constraint_args(),
                 f"mcp-composer{settings.mcp_composer_version}",
                 "--mode",
                 "http",
@@ -896,7 +898,7 @@ async def install_mcp_config(
             streamable_http_url = await get_project_streamable_http_url(project_id)
             legacy_sse_url = await get_project_sse_url(project_id)
             command = "uvx"
-            args = ["mcp-proxy"]
+            args = [*mcp_sdk_constraint_args(), "mcp-proxy"]
             # Check if we need to add Langflow API key headers
             # Necessary only when Project API Key Authentication is enabled
 

src/backend/base/langflow/api/v1/projects_mcp_helpers.py

@@ -7,10 +7,14 @@
 from uuid import UUID
 
 from fastapi import HTTPException
+from lfx.base.mcp.uvx import mcp_sdk_constraint_args
 from lfx.log.logger import logger
 from lfx.services.mcp_composer.service import MCPComposerService
 
-from langflow.api.utils.mcp.config_utils import validate_mcp_server_for_project
+from langflow.api.utils.mcp.config_utils import (
+    mcp_server_config_uses_current_uvx_constraint,
+    validate_mcp_server_for_project,
+)
 from langflow.api.v1.mcp_projects import get_project_streamable_http_url
 from langflow.api.v2.mcp import update_server
 from langflow.services.database.models.api_key.crud import create_api_key
@@ -48,7 +52,11 @@ def _server_config_matches_project_auth(
         return False
 
     args = existing_config.get("args")
-    if not isinstance(args, list) or not _server_config_uses_streamable_http(args, streamable_http_url):
+    if (
+        not isinstance(args, list)
+        or not mcp_server_config_uses_current_uvx_constraint(existing_config, "mcp-proxy")
+        or not _server_config_uses_streamable_http(args, streamable_http_url)
+    ):
         return False
 
     has_project_api_key = _server_config_has_project_api_key(args)
@@ -117,6 +125,7 @@ async def register_mcp_servers_for_project(
             unmasked_api_key = await create_api_key(session, ApiKeyCreate(name=api_key_name), current_user.id)
             command = "uvx"
             args = [
+                *mcp_sdk_constraint_args(),
                 "mcp-proxy",
                 "--transport",
                 "streamablehttp",
@@ -132,6 +141,7 @@ async def register_mcp_servers_for_project(
         else:
             command = "uvx"
             args = [
+                *mcp_sdk_constraint_args(),
                 "mcp-proxy",
                 "--transport",
                 "streamablehttp",

src/backend/base/pyproject.toml

@@ -18,7 +18,7 @@ maintainers = [
 
 dependencies = [
     "lfx~=1.11.0",
-    "fastapi>=0.139.0,<0.140.0",
+    "fastapi>=0.139.0,<1.0.0",
     "slowapi>=0.1.9,<1.0.0",
     "httpx[http2]>=0.27,<1.0.0",
     "aiofile>=3.9.0,<4.0.0",

src/backend/tests/unit/api/utils/test_config_utils.py

@@ -6,6 +6,7 @@
 from langflow.api.utils.mcp.config_utils import (
     MCPServerValidationResult,
     auto_configure_starter_projects_mcp,
+    mcp_server_config_uses_current_uvx_constraint,
     validate_mcp_server_for_project,
 )
 from langflow.services.database.models.flow.model import Flow
@@ -27,6 +28,38 @@ def _build_server_config(base_url: str, project_id, transport: str):
     return url, {"command": "uvx", "args": args}
 
 
+@pytest.mark.parametrize(
+    ("constraint_args", "server_args", "expected"),
+    [
+        (["--with", "mcp~=1.28"], ["--with", "mcp~=1.28", "mcp-proxy"], True),
+        (["--with", "mcp~=1.28"], ["mcp-proxy"], False),
+        (["--with", "mcp~=1.30"], ["--with", "mcp~=1.28", "mcp-proxy"], False),
+        ([], ["mcp-proxy"], True),
+        ([], ["--with", "mcp~=1.28", "mcp-proxy"], False),
+    ],
+)
+def test_generated_uvx_config_matches_current_sdk_constraint(constraint_args, server_args, expected):
+    config = {"command": "uvx", "args": [*server_args, "--transport", "streamablehttp"]}
+
+    with patch(
+        "langflow.api.utils.mcp.config_utils.mcp_sdk_constraint_args",
+        return_value=constraint_args,
+    ):
+        assert mcp_server_config_uses_current_uvx_constraint(config, "mcp-proxy") is expected
+
+
+@pytest.mark.parametrize(
+    "config",
+    [
+        {"command": "npx", "args": ["mcp-proxy"]},
+        {"command": "uvx", "args": "mcp-proxy"},
+        {"command": "uvx"},
+    ],
+)
+def test_generated_uvx_config_rejects_non_generated_shapes(config):
+    assert mcp_server_config_uses_current_uvx_constraint(config, "mcp-proxy") is False
+
+
 class TestMCPServerValidationResult:
     """Test the MCPServerValidationResult class and its properties."""
 

src/backend/tests/unit/api/v1/test_projects_mcp_helpers.py

@@ -0,0 +1,62 @@
+from unittest.mock import patch
+
+from langflow.api.v1.projects_mcp_helpers import _server_config_matches_project_auth
+
+
+def _project_server_config(url: str, *, pinned: bool, api_key: bool = False) -> dict:
+    args = ["--with", "mcp~=1.28"] if pinned else []
+    args.extend(["mcp-proxy", "--transport", "streamablehttp"])
+    if api_key:
+        args.extend(["--headers", "x-api-key", "test-key"])
+    args.append(url)
+    return {"command": "uvx", "args": args}
+
+
+def test_existing_project_config_without_sdk_constraint_requires_reconciliation():
+    url = "http://localhost:7860/api/v1/mcp/project/test/streamable"
+
+    with patch(
+        "langflow.api.utils.mcp.config_utils.mcp_sdk_constraint_args",
+        return_value=["--with", "mcp~=1.28"],
+    ):
+        assert (
+            _server_config_matches_project_auth(
+                _project_server_config(url, pinned=False),
+                "none",
+                url,
+            )
+            is False
+        )
+        assert (
+            _server_config_matches_project_auth(
+                _project_server_config(url, pinned=True),
+                "none",
+                url,
+            )
+            is True
+        )
+
+
+def test_existing_apikey_config_without_sdk_constraint_requires_reconciliation():
+    url = "http://localhost:7860/api/v1/mcp/project/test/streamable"
+
+    with patch(
+        "langflow.api.utils.mcp.config_utils.mcp_sdk_constraint_args",
+        return_value=["--with", "mcp~=1.28"],
+    ):
+        assert (
+            _server_config_matches_project_auth(
+                _project_server_config(url, pinned=False, api_key=True),
+                "apikey",
+                url,
+            )
+            is False
+        )
+        assert (
+            _server_config_matches_project_auth(
+                _project_server_config(url, pinned=True, api_key=True),
+                "apikey",
+                url,
+            )
+            is True
+        )

src/frontend/tests/extended/features/mcp-server.spec.ts

@@ -2,6 +2,10 @@ import { expect, test } from "../../fixtures";
 import { adjustScreenView } from "../../utils/adjust-screen-view";
 import { awaitBootstrapTest } from "../../utils/await-bootstrap-test";
 import { TEXTS } from "../../utils/constants/texts";
+import {
+  FETCH_SERVER_ARGS,
+  fillFetchServerCommand,
+} from "../../utils/fill-fetch-server-command";
 import { openBlankFlow } from "../../utils/flow/open-blank-flow";
 import { openFlowCard } from "../../utils/flow/open-flow-card";
 import { openAddMcpServerModal } from "../../utils/open-add-mcp-server-modal";
@@ -56,8 +60,7 @@ test(
     const testName = `test_server_${randomSuffix}`;
     await page.getByTestId("stdio-name-input").fill(testName);
 
-    await page.getByTestId("stdio-command-input").fill("uvx");
-    await page.getByTestId("stdio-args_0").fill("mcp-server-fetch");
+    await fillFetchServerCommand(page);
 
     await page.getByTestId("add-mcp-server-button").click();
 
@@ -157,9 +160,11 @@ test(
     expect(await page.getByTestId("stdio-command-input").inputValue()).toBe(
       "uvx",
     );
-    expect(await page.getByTestId("stdio-args_0").inputValue()).toBe(
-      "mcp-server-fetch",
-    );
+    for (const [index, arg] of FETCH_SERVER_ARGS.entries()) {
+      expect(await page.getByTestId(`stdio-args_${index}`).inputValue()).toBe(
+        arg,
+      );
+    }
 
     await page.waitForTimeout(500);
 
@@ -234,8 +239,7 @@ test(
 
     await page.waitForTimeout(500);
 
-    await page.getByTestId("stdio-command-input").fill("uvx");
-    await page.getByTestId("stdio-args_0").fill("mcp-server-fetch");
+    await fillFetchServerCommand(page);
 
     await page.getByTestId("add-mcp-server-button").click();
 
@@ -707,8 +711,7 @@ test(
     const testName = `test_server_${randomSuffix}`;
     await page.getByTestId("stdio-name-input").fill(testName);
 
-    await page.getByTestId("stdio-command-input").fill("uvx");
-    await page.getByTestId("stdio-args_0").fill("mcp-server-fetch");
+    await fillFetchServerCommand(page);
 
     await page.getByTestId("add-mcp-server-button").click();
 
@@ -821,11 +824,16 @@ test(
     expect(await page.getByTestId("stdio-command-input").inputValue()).toBe(
       "uvx",
     );
-    expect(await page.getByTestId("stdio-args_0").inputValue()).toBe(
-      "mcp-server-fetch",
-    );
+    for (const [index, arg] of FETCH_SERVER_ARGS.entries()) {
+      expect(await page.getByTestId(`stdio-args_${index}`).inputValue()).toBe(
+        arg,
+      );
+    }
 
-    await page.getByTestId("stdio-args_0").fill("mcp-server-time");
+    // Swap only the package operand; the leading `--with mcp~=1.28` still applies.
+    await page
+      .getByTestId(`stdio-args_${FETCH_SERVER_ARGS.length - 1}`)
+      .fill("mcp-server-time");
 
     await page.getByTestId("add-mcp-server-button").click();
 
@@ -937,8 +945,7 @@ test(
 
     await page.getByTestId("stdio-name-input").fill(testName);
 
-    await page.getByTestId("stdio-command-input").fill("uvx");
-    await page.getByTestId("stdio-args_0").fill("mcp-server-fetch");
+    await fillFetchServerCommand(page);
 
     await page.getByTestId("add-mcp-server-button").click();