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fix(server): connectors header forwading #1553

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Merged
pilartomas merged 2 commits into from
Nov 13, 2025
Merged

fix(server): connectors header forwading #1553

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835269c
fix(server): connectors header forwading
pilartomas Nov 13, 2025
88bc591
fixup!
pilartomas Nov 13, 2025
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4 changes: 1 addition & 3 deletions apps/agentstack-server/src/agentstack_server/api/routes/connectors.py
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,6 @@
ConnectorPresetResponse,
ConnectorResponse,
)
from agentstack_server.api.utils import to_fastapi
from agentstack_server.configuration import ConnectorPreset
from agentstack_server.domain.models.common import PaginatedResult
from agentstack_server.domain.models.connector import Connector
Expand Down Expand Up @@ -118,8 +117,7 @@ async def mcp(
connector_service: ConnectorServiceDependency,
user: Annotated[AuthorizedUser, Depends(RequiresPermissions(connectors={"proxy"}))],
):
response = await connector_service.mcp_proxy(connector_id=connector_id, request=request, user=user.user)
return to_fastapi(response)
return await connector_service.mcp_proxy(connector_id=connector_id, request=request, user=user.user)


@router.get("/oauth/callback")
Expand Down
39 changes: 14 additions & 25 deletions apps/agentstack-server/src/agentstack_server/service_layer/services/connector.py
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,7 @@
from authlib.integrations.httpx_client import AsyncOAuth2Client
from authlib.oauth2.rfc8414 import AuthorizationServerMetadata, get_well_known_url
from fastapi import Request, status
from fastapi.responses import HTMLResponse, RedirectResponse
from fastapi.responses import HTMLResponse, RedirectResponse, StreamingResponse
from kink import inject
from mcp import ClientSession
from mcp.client.streamable_http import streamablehttp_client
Expand All @@ -33,7 +33,6 @@
)
from agentstack_server.domain.models.user import User
from agentstack_server.exceptions import EntityNotFoundError, PlatformError
from agentstack_server.service_layer.services.mcp import McpServerResponse
from agentstack_server.service_layer.unit_of_work import IUnitOfWorkFactory

logger = logging.getLogger(__name__)
Expand Down Expand Up @@ -118,7 +117,7 @@ async def connect_connector(
) from err
elif isinstance(err, httpx.RequestError):
raise PlatformError(
"Connector must be in connected or auth_required state",
"Unable to establish connection with the connector",
status_code=status.HTTP_504_GATEWAY_TIMEOUT,
) from err
else:
Expand Down Expand Up @@ -379,10 +378,14 @@ def client_factory(headers=None, timeout=None, auth=None):
raise excgroup.exceptions[0] from excgroup
raise excgroup

async def mcp_proxy(self, *, connector_id: UUID, request: Request, user: User | None = None) -> McpServerResponse:
async def mcp_proxy(self, *, connector_id: UUID, request: Request, user: User | None = None):
connector = await self.read_connector(connector_id=connector_id, user=user)

forward_headers = {key: request.headers[key] for key in ["accept", "content-type"] if key in request.headers}
forward_headers = {
key: request.headers[key]
for key in ["accept", "content-type", "mcp-protocol-version", "mcp-session-id", "last-event-id"]
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@gemini-code-assist gemini-code-assist bot Nov 13, 2025

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medium

This list of headers is getting long. For better readability and maintainability, consider defining it as a module-level constant (e.g., a frozenset for efficient lookups).

For example:

# At the top of the file
_FORWARDED_MCP_HEADERS = frozenset((
    "accept",
    "content-type",
    "mcp-protocol-version",
    "mcp-session-id",
    "last-event-id",
))

# In the method:
# ...
for key in _FORWARDED_MCP_HEADERS:
# ...

if key in request.headers
}

exit_stack = AsyncExitStack()
try:
Expand All @@ -399,32 +402,18 @@ async def mcp_proxy(self, *, connector_id: UUID, request: Request, user: User |
and connector.auth.token.token_type == "bearer"
else {}
),
content=await request.body(),
content=request.stream(),
)
)

content_type: str | None = response.headers.get("content-type")
is_stream = content_type.startswith("text/event-stream") if content_type else False
common = {
"status_code": response.status_code,
"headers": response.headers,
"media_type": content_type if is_stream else None,
}
if is_stream:

async def stream_fn():
try:
async for chunk in response.aiter_bytes():
yield chunk
finally:
await exit_stack.pop_all().aclose()

return McpServerResponse(content=None, stream=stream_fn(), **common)
else:
async def stream_fn():
try:
return McpServerResponse(content=await response.aread(), stream=None, **common)
async for chunk in response.aiter_bytes():
yield chunk
finally:
await exit_stack.pop_all().aclose()

return StreamingResponse(stream_fn(), status_code=response.status_code, headers=response.headers)
except BaseException:
await exit_stack.pop_all().aclose()
raise
Expand Down
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