Description
Bifrost's MCP Gateway POST /mcp works, but authenticated GET /mcp with Accept: text/event-stream never sends response headers or an initial SSE event.
This breaks MCP clients using Streamable HTTP transport, such as opencode, because they open a GET SSE listener for server-to-client messages during connect.
Environment
- Bifrost Docker image:
maximhq/bifrost:latest
- MCP initialize reports:
serverInfo.version = v1.4.24
- Also reproduced with:
maximhq/bifrost:v1.5.0-prerelease7
- Governance / virtual key auth enabled
- Connected MCP clients are healthy;
POST /mcp works
Reproduction
Unauthenticated GET returns immediately with 401, so the route is reachable:
curl -i -m 5 http://localhost:8080/mcp \
-H 'Accept: text/event-stream'
Authenticated POST initialize works:
curl -i -m 10 http://localhost:8080/mcp \
-H 'Authorization: Bearer <virtual-key>' \
-H 'Content-Type: application/json' \
-H 'Accept: application/json, text/event-stream' \
--data-raw '{
"jsonrpc":"2.0",
"id":1,
"method":"initialize",
"params":{
"protocolVersion":"2025-03-26",
"capabilities":{},
"clientInfo":{"name":"curl","version":"test"}
}
}'Response on latest:
{
"jsonrpc": "2.0",
"id": 1,
"result": {
"protocolVersion": "2025-03-26",
"capabilities": {"tools": {"listChanged": true}},
"serverInfo": {"name": "dev", "version": "v1.4.24"}
}
}Authenticated GET SSE hangs without response headers:
curl -i -m 15 http://localhost:8080/mcp \
-H 'Authorization: Bearer <virtual-key>' \
-H 'Accept: text/event-stream'
Actual result:
curl: (28) Operation timed out after 15002 milliseconds with 0 bytes received
Same behavior was reproduced with X-Api-Key: <virtual-key> and with maximhq/bifrost:v1.5.0-prerelease7.
Expected behavior
According to the MCP Gateway docs, GET /mcp should establish an SSE stream and send a connection/opened message, then keep the connection alive.
Docs: https://docs.getbifrost.ai/mcp/gateway-url
Actual behavior
With valid virtual key auth, Bifrost accepts the connection but does not send HTTP response headers or SSE data. The client hangs until its timeout.
Related
Description
Bifrost's MCP Gateway
POST /mcpworks, but authenticatedGET /mcpwithAccept: text/event-streamnever sends response headers or an initial SSE event.This breaks MCP clients using Streamable HTTP transport, such as opencode, because they open a GET SSE listener for server-to-client messages during connect.
Environment
maximhq/bifrost:latestserverInfo.version = v1.4.24maximhq/bifrost:v1.5.0-prerelease7POST /mcpworksReproduction
Unauthenticated GET returns immediately with 401, so the route is reachable:
curl -i -m 5 http://localhost:8080/mcp \ -H 'Accept: text/event-stream'Authenticated POST initialize works:
Response on
latest:{ "jsonrpc": "2.0", "id": 1, "result": { "protocolVersion": "2025-03-26", "capabilities": {"tools": {"listChanged": true}}, "serverInfo": {"name": "dev", "version": "v1.4.24"} } }Authenticated GET SSE hangs without response headers:
Actual result:
Same behavior was reproduced with
X-Api-Key: <virtual-key>and withmaximhq/bifrost:v1.5.0-prerelease7.Expected behavior
According to the MCP Gateway docs,
GET /mcpshould establish an SSE stream and send aconnection/openedmessage, then keep the connection alive.Docs: https://docs.getbifrost.ai/mcp/gateway-url
Actual behavior
With valid virtual key auth, Bifrost accepts the connection but does not send HTTP response headers or SSE data. The client hangs until its timeout.
Related