🐞 Bug Summary

Forwarded RPC execution can incorrectly return a success-shaped payload ({"result": {}}) when the internal /rpc call fails with non-JSON-RPC HTTP errors (for example 401 {"detail":"Authorization token required"}).

This currently makes auth/policy failures look like successful forwarded execution.

Related test stability issue: two session-affinity tests depend on localhost port state (127.0.0.1:4444) and are non-hermetic.

🧩 Affected Component

Select the area of the project impacted:

• mcpgateway - API
• mcpgateway - UI (admin panel)
• mcpgateway.wrapper - stdio wrapper
• Federation or Transports
• CLI, Makefiles, or shell scripts
• Container setup (Docker/Podman/Compose)
• Other (explain below)

Other: session-affinity test reliability (tests/e2e/test_session_pool_e2e.py).

🔁 Steps to Reproduce

1. Run these tests:

   uv run pytest -vv \
     tests/e2e/test_session_pool_e2e.py::TestMultiWorkerSessionAffinityE2E::test_execute_forwarded_request_returns_error_when_no_server \
     tests/e2e/test_session_pool_e2e.py::TestMultiWorkerSessionAffinityE2E::test_affinity_logs_when_executing_forwarded_request

2. Ensure something is listening on 127.0.0.1:4444 and /rpc returns 401 with body shaped like {"detail": "..."} (non-JSON-RPC error object).
3. Re-run the same tests.

Observed: both tests fail with assert "error" in result because result is {"result": {}}.

Control: with nothing listening on :4444, same tests pass (connection error path returns JSON-RPC internal error).

🤔 Expected Behavior

• _execute_forwarded_request() should treat non-2xx internal /rpc responses as errors.
• If response body is JSON-RPC ({"error": ...}), propagate it.
• If response body is non-JSON-RPC ({"detail": ...}), map to JSON-RPC error instead of returning {"result": {}}.
• Tests should be deterministic and not depend on ambient localhost listeners.

📓 Logs / Error Output

Representative failure logs:

HTTP Request: POST http://127.0.0.1:4444/rpc "HTTP/1.0 401 Unauthorized"
[AFFINITY] ... Forwarded execution completed successfully
E AssertionError: assert 'error' in {'result': {}}

Relevant code paths:

• mcpgateway/services/mcp_session_pool.py (_execute_forwarded_request)
• mcpgateway/main.py (handle_rpc forwarded response handling)
• tests/e2e/test_session_pool_e2e.py (two tests above)

🧠 Environment Info

You can retrieve most of this from the /version endpoint.

🧩 Additional Context (optional)

Current behavior in _execute_forwarded_request() inspects JSON body for an error key but does not gate on HTTP status. That allows non-2xx + non-JSON-RPC bodies to be converted to {"result": {}}.

Suggested direction:

• Gate on response.status_code >= 400.
• Convert non-JSON-RPC non-2xx responses to JSON-RPC error.
• Update tests to mock internal HTTP response shapes instead of relying on localhost process state.