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fix(web): return 405 for GET /api/mcp instead of hanging connection #1064

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Merged
brendan-kellam merged 2 commits into from
Mar 31, 2026
+12 −34
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fix(web): return 405 for GET /api/mcp instead of hanging connection #1064

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6f05df9
fix(web): return 405 for GET /api/mcp instead of hanging connection
brendan-kellam Mar 31, 2026
4920101
chore: update CHANGELOG for #1064
brendan-kellam Mar 31, 2026
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3 changes: 3 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
### Added
- Added `GET /api/diff` endpoint for retrieving structured diffs between two git refs ([#1063](https://github.com/sourcebot-dev/sourcebot/pull/1063))

### Fixed
- Fixed `GET /api/mcp` hanging with zero bytes by returning `405 Method Not Allowed` per the MCP Streamable HTTP spec ([#1064](https://github.com/sourcebot-dev/sourcebot/pull/1064))

## [4.16.3] - 2026-03-27

### Added
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43 changes: 9 additions & 34 deletions packages/web/src/app/api/(server)/mcp/route.ts
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Expand Up @@ -129,38 +129,13 @@ export const DELETE = apiHandler(async (request: NextRequest) => {
return result;
});

export const GET = apiHandler(async (request: NextRequest) => {
const result = await sew(() =>
withOptionalAuthV2(async ({ user }) => {
if (env.EXPERIMENT_ASK_GH_ENABLED === 'true' && !user) {
return notAuthenticated();
}
const ownerId = user?.id ?? null;
const sessionId = request.headers.get(MCP_SESSION_ID_HEADER);
if (!sessionId || !sessions.has(sessionId)) {
return {
statusCode: StatusCodes.NOT_FOUND,
errorCode: ErrorCode.NOT_FOUND,
message: 'Session not found.',
} satisfies ServiceError;
}

const session = sessions.get(sessionId)!;
if (session.ownerId !== ownerId) {
return {
statusCode: StatusCodes.FORBIDDEN,
errorCode: ErrorCode.INSUFFICIENT_PERMISSIONS,
message: 'Session does not belong to the authenticated user.',
} satisfies ServiceError;
}

return session.transport.handleRequest(request);
})
);

if (isServiceError(result)) {
return mcpErrorResponse(result);
}

return result;
// Sourcebot does not send server-initiated messages, so the GET SSE stream is not
// supported. Per the MCP Streamable HTTP spec, servers that do not offer a GET SSE
// stream MUST return 405 Method Not Allowed.
// @see: https://modelcontextprotocol.io/specification/2025-03-26/basic/transports#listening-for-messages-from-the-server
export const GET = apiHandler(async (_request: NextRequest) => {
return new Response(null, {
status: StatusCodes.METHOD_NOT_ALLOWED,
headers: { Allow: 'POST, DELETE' },
});
});
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