fix: correctly pass headers in mcp stdio connections (#11804)

* fix: parse dicts from tweaks (#11753)

* Correctly parse dicts from tweaks

* Add test

* [autofix.ci] apply automated fixes

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

* fix: dict tweak parsing (#11756)

* Fix dict handling of different formats

* [autofix.ci] apply automated fixes

* [autofix.ci] apply automated fixes (attempt 2/3)

* [autofix.ci] apply automated fixes (attempt 3/3)

* cmp index

* [autofix.ci] apply automated fixes

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

* fix: correctly pass headers in mcp stdio connections (#11746)

* Update positional arg logic

* Add positiona logic tests

* ruff

* [autofix.ci] apply automated fixes

* add check for tweaking code, add check or mcp field type

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

src/backend/base/langflow/processing/process.py

@@ -158,6 +158,15 @@ def apply_tweaks(node: dict[str, Any], node_tweaks: dict[str, Any]) -> None:
             elif field_type == "mcp":
                 # MCP fields expect dict values to be set directly
                 template_data[tweak_name]["value"] = tweak_value
+            elif field_type == "dict" and isinstance(tweak_value, dict):
+                # Dict fields: set the dict directly as the value.
+                # If the tweak is wrapped in {"value": <actual>}, unwrap it
+                # to support the template-format style (e.g. from UI exports).
+                # Caveat: a legitimate single-key dict {"value": x} will be unwrapped.
+                if len(tweak_value) == 1 and "value" in tweak_value:
+                    template_data[tweak_name]["value"] = tweak_value["value"]
+                else:
+                    template_data[tweak_name]["value"] = tweak_value
             elif isinstance(tweak_value, dict):
                 for k, v in tweak_value.items():
                     k_ = "file_path" if field_type == "file" else k

src/backend/tests/unit/base/mcp/test_mcp_util.py

@@ -19,6 +19,7 @@ from lfx.base.mcp.util import (
     MCPStdioClient,
     MCPStreamableHttpClient,
     _process_headers,
+    update_tools,
     validate_headers,
 )
 
@@ -379,6 +380,209 @@ class TestStreamableHTTPHeaderIntegration:
         assert streamable_http_client._connection_params["headers"] == test_headers
 
 
+class TestUpdateToolsStdioHeaders:
+    """Test that update_tools injects component headers into stdio args."""
+
+    @pytest.mark.asyncio
+    async def test_stdio_headers_injected_with_existing_headers_flag(self):
+        """Headers should be injected as --headers key value before the existing --headers flag."""
+        mock_stdio = AsyncMock(spec=MCPStdioClient)
+        mock_stdio.connect_to_server.return_value = []
+        mock_stdio._connected = True
+
+        server_config = {
+            "command": "uvx",
+            "args": [
+                "mcp-proxy",
+                "--transport",
+                "streamablehttp",
+                "--headers",
+                "x-api-key",
+                "sk-existing",
+                "http://localhost:7860/api/v1/mcp/project/test/streamable",
+            ],
+            "headers": {"Authorization": "Bearer token123"},
+        }
+
+        await update_tools("test-server", server_config, mcp_stdio_client=mock_stdio)
+
+        mock_stdio.connect_to_server.assert_called_once()
+        full_command = mock_stdio.connect_to_server.call_args[0][0]
+
+        # The injected --headers should appear before the existing --headers
+        assert "--headers authorization 'Bearer token123' --headers x-api-key sk-existing" in full_command
+        # URL should still be at the end
+        assert full_command.endswith("http://localhost:7860/api/v1/mcp/project/test/streamable")
+
+    @pytest.mark.asyncio
+    async def test_stdio_headers_injected_without_existing_headers_flag(self):
+        """When no --headers flag exists, headers should be inserted before the last positional arg."""
+        mock_stdio = AsyncMock(spec=MCPStdioClient)
+        mock_stdio.connect_to_server.return_value = []
+        mock_stdio._connected = True
+
+        server_config = {
+            "command": "uvx",
+            "args": [
+                "mcp-proxy",
+                "--transport",
+                "streamablehttp",
+                "http://localhost:7860/streamable",
+            ],
+            "headers": {"X-Api-Key": "my-key"},
+        }
+
+        await update_tools("test-server", server_config, mcp_stdio_client=mock_stdio)
+
+        full_command = mock_stdio.connect_to_server.call_args[0][0]
+
+        # --headers should be inserted before the URL
+        assert "--headers x-api-key my-key http://localhost:7860/streamable" in full_command
+
+    @pytest.mark.asyncio
+    async def test_stdio_multiple_headers_each_get_own_flag(self):
+        """Each header should get its own --headers key value triplet."""
+        mock_stdio = AsyncMock(spec=MCPStdioClient)
+        mock_stdio.connect_to_server.return_value = []
+        mock_stdio._connected = True
+
+        server_config = {
+            "command": "uvx",
+            "args": [
+                "mcp-proxy",
+                "--transport",
+                "streamablehttp",
+                "--headers",
+                "x-api-key",
+                "sk-existing",
+                "http://localhost/streamable",
+            ],
+            "headers": {"X-Custom-One": "val1", "X-Custom-Two": "val2"},
+        }
+
+        await update_tools("test-server", server_config, mcp_stdio_client=mock_stdio)
+
+        full_command = mock_stdio.connect_to_server.call_args[0][0]
+
+        # Each header gets its own --headers flag
+        assert "--headers x-custom-one val1" in full_command
+        assert "--headers x-custom-two val2" in full_command
+        # Original header still present
+        assert "--headers x-api-key sk-existing" in full_command
+
+    @pytest.mark.asyncio
+    async def test_stdio_no_headers_leaves_args_unchanged(self):
+        """When no component headers are set, args should not be modified."""
+        mock_stdio = AsyncMock(spec=MCPStdioClient)
+        mock_stdio.connect_to_server.return_value = []
+        mock_stdio._connected = True
+
+        server_config = {
+            "command": "uvx",
+            "args": ["mcp-proxy", "--transport", "streamablehttp", "http://localhost/streamable"],
+        }
+
+        await update_tools("test-server", server_config, mcp_stdio_client=mock_stdio)
+
+        full_command = mock_stdio.connect_to_server.call_args[0][0]
+        assert full_command == "uvx mcp-proxy --transport streamablehttp http://localhost/streamable"
+
+    @pytest.mark.asyncio
+    async def test_stdio_headers_appended_when_all_args_are_flags(self):
+        """When all args are flags (no positional URL), headers should be appended."""
+        mock_stdio = AsyncMock(spec=MCPStdioClient)
+        mock_stdio.connect_to_server.return_value = []
+        mock_stdio._connected = True
+
+        server_config = {
+            "command": "some-tool",
+            "args": ["--verbose", "--debug"],
+            "headers": {"Authorization": "Bearer tok"},
+        }
+
+        await update_tools("test-server", server_config, mcp_stdio_client=mock_stdio)
+
+        full_command = mock_stdio.connect_to_server.call_args[0][0]
+        assert full_command == "some-tool --verbose --debug --headers authorization 'Bearer tok'"
+
+    @pytest.mark.asyncio
+    async def test_stdio_headers_appended_when_last_token_is_flag_value(self):
+        """When the last token is a flag's value, headers should be appended, not inserted before it."""
+        mock_stdio = AsyncMock(spec=MCPStdioClient)
+        mock_stdio.connect_to_server.return_value = []
+        mock_stdio._connected = True
+
+        server_config = {
+            "command": "some-tool",
+            "args": ["--port", "8080"],
+            "headers": {"Authorization": "Bearer tok"},
+        }
+
+        await update_tools("test-server", server_config, mcp_stdio_client=mock_stdio)
+
+        full_command = mock_stdio.connect_to_server.call_args[0][0]
+        # 8080 is a value for --port, not a positional arg, so headers go at the end
+        assert full_command == "some-tool --port 8080 --headers authorization 'Bearer tok'"
+
+    @pytest.mark.asyncio
+    async def test_stdio_headers_inserted_before_positional_with_flag_value_pairs(self):
+        """Headers should be inserted before the last positional arg even when flag+value pairs precede it."""
+        mock_stdio = AsyncMock(spec=MCPStdioClient)
+        mock_stdio.connect_to_server.return_value = []
+        mock_stdio._connected = True
+
+        server_config = {
+            "command": "uvx",
+            "args": ["mcp-proxy", "--port", "8080", "http://localhost/streamable"],
+            "headers": {"X-Api-Key": "my-key"},
+        }
+
+        await update_tools("test-server", server_config, mcp_stdio_client=mock_stdio)
+
+        full_command = mock_stdio.connect_to_server.call_args[0][0]
+        # --port 8080 is a flag pair; http://localhost/streamable is the positional arg
+        assert full_command == "uvx mcp-proxy --port 8080 --headers x-api-key my-key http://localhost/streamable"
+
+    @pytest.mark.asyncio
+    async def test_stdio_headers_inserted_before_last_positional_with_multiple_positionals(self):
+        """When multiple positional args exist, headers are inserted before the last one."""
+        mock_stdio = AsyncMock(spec=MCPStdioClient)
+        mock_stdio.connect_to_server.return_value = []
+        mock_stdio._connected = True
+
+        server_config = {
+            "command": "uvx",
+            "args": ["mcp-proxy", "--transport", "streamablehttp", "extra-pos-arg", "http://localhost/streamable"],
+            "headers": {"X-Key": "val"},
+        }
+
+        await update_tools("test-server", server_config, mcp_stdio_client=mock_stdio)
+
+        full_command = mock_stdio.connect_to_server.call_args[0][0]
+        # Should insert before the last positional (the URL), not before "extra-pos-arg"
+        assert "--headers x-key val http://localhost/streamable" in full_command
+        assert "extra-pos-arg --headers" in full_command
+
+    @pytest.mark.asyncio
+    async def test_stdio_does_not_mutate_original_config(self):
+        """The original server_config args list should not be mutated."""
+        mock_stdio = AsyncMock(spec=MCPStdioClient)
+        mock_stdio.connect_to_server.return_value = []
+        mock_stdio._connected = True
+
+        original_args = ["mcp-proxy", "--headers", "x-api-key", "sk-orig", "http://localhost/s"]
+        server_config = {
+            "command": "uvx",
+            "args": original_args,
+            "headers": {"X-Extra": "val"},
+        }
+
+        await update_tools("test-server", server_config, mcp_stdio_client=mock_stdio)
+
+        # Original list should be unchanged
+        assert original_args == ["mcp-proxy", "--headers", "x-api-key", "sk-orig", "http://localhost/s"]
+
+
 class TestFieldNameConversion:
     """Test camelCase to snake_case field name conversion functionality."""
 

src/backend/tests/unit/test_process.py

@@ -473,3 +473,115 @@ def test_apply_tweaks_field_type_extraction():
     # Verify both fields were modified
     assert node["data"]["node"]["template"]["param_no_type"]["value"] == "new_value_1"
     assert node["data"]["node"]["template"]["param_with_type"]["value"] == "new_value_2"
+
+
+def test_apply_tweaks_dict_field_type():
+    """Test that dict field types (e.g. DictInput headers) set the value directly.
+
+    Previously, passing a dict tweak for a 'dict' field type would iterate over
+    the dict keys and set them as top-level template properties instead of setting
+    the field's value. This caused headers passed via tweaks to be ignored.
+    """
+    from langflow.processing.process import apply_tweaks
+
+    # Create a node with a dict field type (like MCP Tools headers)
+    node = {
+        "id": "MCPTools-322Z0",
+        "data": {
+            "node": {
+                "template": {
+                    "headers": {
+                        "value": [
+                            {"key": "header1", "value": "default1"},
+                            {"key": "header2", "value": "default2"},
+                        ],
+                        "type": "dict",
+                    },
+                }
+            }
+        },
+    }
+
+    # Tweak headers with a plain dict (as sent via API tweaks)
+    node_tweaks = {
+        "headers": {"header1": "override1", "header2": "override2", "header3": "new3"},
+    }
+
+    apply_tweaks(node, node_tweaks)
+
+    # Verify the dict was set directly as the value, not spread as template properties
+    assert node["data"]["node"]["template"]["headers"]["value"] == {
+        "header1": "override1",
+        "header2": "override2",
+        "header3": "new3",
+    }
+    # Ensure the tweak keys were NOT set as top-level template field properties
+    assert "header1" not in node["data"]["node"]["template"]["headers"]
+    assert "header2" not in node["data"]["node"]["template"]["headers"]
+    assert "header3" not in node["data"]["node"]["template"]["headers"]
+
+
+def test_apply_tweaks_dict_field_overwrites_list_default():
+    """Test that a dict tweak fully replaces a list-format default value on a dict field."""
+    from langflow.processing.process import apply_tweaks
+
+    node = {
+        "id": "node1",
+        "data": {
+            "node": {
+                "template": {
+                    "headers": {
+                        "value": [{"key": "old", "value": "old_val"}],
+                        "type": "dict",
+                    },
+                }
+            }
+        },
+    }
+
+    apply_tweaks(node, {"headers": {"new_key": "new_val"}})
+
+    # The dict tweak should fully replace the old list value
+    assert node["data"]["node"]["template"]["headers"]["value"] == {"new_key": "new_val"}
+
+
+def test_apply_tweaks_dict_field_value_wrapped_list():
+    """Test that dict field tweaks wrapped in {"value": [...]} are unwrapped correctly.
+
+    When users pass tweaks in the template-format style (e.g. from UI exports),
+    the list of key-value pairs is wrapped in a "value" key. The tweak should
+    unwrap this and set the inner list as the field's value.
+    """
+    from langflow.processing.process import apply_tweaks
+
+    node = {
+        "id": "MCPTools-svrRq",
+        "data": {
+            "node": {
+                "template": {
+                    "headers": {
+                        "value": [],
+                        "type": "dict",
+                    },
+                }
+            }
+        },
+    }
+
+    # Tweak using the template-format wrapper: {"value": [list of key-value pairs]}
+    node_tweaks = {
+        "headers": {
+            "value": [
+                {"key": "header1", "value": "gabriel1"},
+                {"key": "header2", "value": "gabriel2"},
+            ]
+        },
+    }
+
+    apply_tweaks(node, node_tweaks)
+
+    # The inner list should be unwrapped and set as the field's value
+    assert node["data"]["node"]["template"]["headers"]["value"] == [
+        {"key": "header1", "value": "gabriel1"},
+        {"key": "header2", "value": "gabriel2"},
+    ]

src/lfx/src/lfx/base/mcp/util.py

@@ -5,7 +5,9 @@ import json
 import os
 import platform
 import re
+import shlex
 import shutil
+import subprocess
 import unicodedata
 from collections.abc import Awaitable, Callable
 from typing import Any
@@ -1056,7 +1058,7 @@ class MCPStdioClient:
         """Connect to MCP server using stdio transport (SDK style)."""
         from mcp import StdioServerParameters
 
-        command = command_str.split(" ")
+        command = shlex.split(command_str)
         env_data: dict[str, str] = {"DEBUG": "true", "PATH": os.environ["PATH"], **(env or {})}
 
         if platform.system() == "Windows":
@@ -1064,7 +1066,7 @@ class MCPStdioClient:
                 command="cmd",
                 args=[
                     "/c",
-                    f"{command[0]} {' '.join(command[1:])} || echo Command failed with exit code %errorlevel% 1>&2",
+                    f"{subprocess.list2cmdline(command)} || echo Command failed with exit code %errorlevel% 1>&2",
                 ],
                 env=env_data,
             )
@@ -1586,10 +1588,52 @@ async def update_tools(
     # Determine connection type and parameters
     client: MCPStdioClient | MCPStreamableHttpClient | None = None
     if mode == "Stdio":
-        # Stdio connection
-        args = server_config.get("args", [])
+        args = list(server_config.get("args", []))
         env = server_config.get("env", {})
-        full_command = " ".join([command, *args])
+        # For stdio mode, inject component headers as --headers CLI args.
+        # This enables passing headers through proxy tools like mcp-proxy
+        # that forward them to the upstream HTTP server.
+        if headers:
+            extra_args = []
+            for key, value in headers.items():
+                extra_args.extend(["--headers", key, str(value)])
+            if "--headers" in args:
+                # Insert before the existing --headers flag so all header
+                # flags are grouped together
+                idx = args.index("--headers")
+                for i, arg in enumerate(extra_args):
+                    args.insert(idx + i, arg)
+            else:
+                # No existing --headers flag; try to insert before the last
+                # positional arg (typically the URL in mcp-proxy commands).
+                # Scan args to find the last true positional token by skipping
+                # flag+value pairs so we don't mistake a flag's value for a
+                # positional argument (e.g. "--port 8080").
+                last_positional_idx: int | None = None
+                i = 0
+                while i < len(args):
+                    if args[i].startswith("-"):
+                        # Skip the flag and its value (assumes each flag
+                        # takes at most one value argument; boolean flags
+                        # are handled correctly since the next token will
+                        # start with '-' or be a URL-like positional).
+                        i += 1
+                        if (
+                            i < len(args)
+                            and not args[i].startswith("-")
+                            and not args[i].startswith("http://")
+                            and not args[i].startswith("https://")
+                        ):
+                            i += 1
+                    else:
+                        last_positional_idx = i
+                        i += 1
+
+                if last_positional_idx is not None:
+                    args = args[:last_positional_idx] + extra_args + args[last_positional_idx:]
+                else:
+                    args.extend(extra_args)
+        full_command = shlex.join([command, *args])
         tools = await mcp_stdio_client.connect_to_server(full_command, env)
         client = mcp_stdio_client
     elif mode in ["Streamable_HTTP", "SSE"]:

src/lfx/src/lfx/graph/vertex/param_handler.py

@@ -266,9 +266,24 @@ class ParameterHandler:
         """Handle dictionary field type."""
         match val:
             case list():
-                params[field_name] = {k: v for item in val for k, v in item.items()}
+                # Convert list of {"key": k, "value": v} pairs to a flat dict.
+                # e.g. [{"key": "h1", "value": "v1"}, {"key": "h2", "value": "v2"}] -> {"h1": "v1", "h2": "v2"}
+                if val and all(isinstance(item, dict) and "key" in item and "value" in item for item in val):
+                    params[field_name] = {item["key"]: item["value"] for item in val}
+                else:
+                    # Merge generic list of dicts into a single dict.
+                    # e.g. [{"a": 1}, {"b": 2}] -> {"a": 1, "b": 2}
+                    params[field_name] = {k: v for item in val for k, v in item.items()}
             case dict():
                 params[field_name] = val
+            case _:
+                logger.warning(
+                    "Unexpected type %s for dict field '%s'; expected list or dict, got %r",
+                    type(val).__name__,
+                    field_name,
+                    val,
+                )
+                params[field_name] = val
         return params
 
     def _handle_other_direct_types(

src/lfx/src/lfx/processing/process.py

@@ -172,16 +172,32 @@ def apply_tweaks(node: dict[str, Any], node_tweaks: dict[str, Any]) -> None:
     for tweak_name, tweak_value in node_tweaks.items():
         if tweak_name not in template_data:
             continue
+        if tweak_name == "code":
+            logger.warning("Security: Code field cannot be overridden via tweaks.")
+            continue
         if tweak_name in template_data:
-            if template_data[tweak_name]["type"] == "NestedDict":
+            field_type = template_data[tweak_name].get("type", "")
+            if field_type == "NestedDict":
                 value = validate_and_repair_json(tweak_value)
                 template_data[tweak_name]["value"] = value
+            elif field_type == "mcp":
+                # MCP fields expect dict values to be set directly
+                template_data[tweak_name]["value"] = tweak_value
+            elif field_type == "dict" and isinstance(tweak_value, dict):
+                # Dict fields: set the dict directly as the value.
+                # If the tweak is wrapped in {"value": <actual>}, unwrap it
+                # to support the template-format style (e.g. from UI exports).
+                # Caveat: a legitimate single-key dict {"value": x} will be unwrapped.
+                if len(tweak_value) == 1 and "value" in tweak_value:
+                    template_data[tweak_name]["value"] = tweak_value["value"]
+                else:
+                    template_data[tweak_name]["value"] = tweak_value
             elif isinstance(tweak_value, dict):
                 for k, v in tweak_value.items():
-                    k_ = "file_path" if template_data[tweak_name]["type"] == "file" else k
+                    k_ = "file_path" if field_type == "file" else k
                     template_data[tweak_name][k_] = v
             else:
-                key = "file_path" if template_data[tweak_name]["type"] == "file" else "value"
+                key = "file_path" if field_type == "file" else "value"
                 template_data[tweak_name][key] = tweak_value
 
 

src/lfx/tests/unit/graph/vertex/test_param_handler.py

@@ -191,3 +191,50 @@ class TestParameterHandlerTableLoadFromDb:
 
         assert set(load_from_db_columns) == {"col1", "col2"}
         assert "table:table_field" in self.handler.load_from_db_fields
+
+
+class TestParameterHandlerDictField:
+    """Tests for _handle_dict_field in ParameterHandler."""
+
+    def setup_method(self):
+        """Set up test fixtures."""
+        self.mock_vertex = MagicMock()
+        self.mock_vertex.data = {"node": {"template": {}}}
+        self.handler = ParameterHandler(self.mock_vertex, storage_service=None)
+
+    def test_handle_dict_field_with_key_value_list(self):
+        """Test that a list of {"key": k, "value": v} pairs is converted to a flat dict."""
+        val = [
+            {"key": "header1", "value": "value1"},
+            {"key": "header2", "value": "value2"},
+        ]
+        params = {}
+        result = self.handler._handle_dict_field("headers", val, params)
+        assert result["headers"] == {"header1": "value1", "header2": "value2"}
+
+    def test_handle_dict_field_with_single_key_value_item(self):
+        """Test a single-item key-value list."""
+        val = [{"key": "auth", "value": "token123"}]
+        params = {}
+        result = self.handler._handle_dict_field("headers", val, params)
+        assert result["headers"] == {"auth": "token123"}
+
+    def test_handle_dict_field_with_flat_dict(self):
+        """Test that a plain dict is passed through as-is."""
+        val = {"header1": "value1", "header2": "value2"}
+        params = {}
+        result = self.handler._handle_dict_field("headers", val, params)
+        assert result["headers"] == {"header1": "value1", "header2": "value2"}
+
+    def test_handle_dict_field_with_empty_list(self):
+        """Test that an empty list produces an empty dict."""
+        params = {}
+        result = self.handler._handle_dict_field("headers", [], params)
+        assert result["headers"] == {}
+
+    def test_handle_dict_field_with_generic_list_of_dicts(self):
+        """Test that a list of dicts without the key/value pattern merges them."""
+        val = [{"a": 1}, {"b": 2}]
+        params = {}
+        result = self.handler._handle_dict_field("data", val, params)
+        assert result["data"] == {"a": 1, "b": 2}