# NousResearch/hermes-agent · MCP poll loop TimeoutError spin causing gateway OOM

## Open now

- Nothing open on GitHub.

Multiple fixes targeting an MCP poll loop bug where a completed future's real TimeoutError is mistaken for a poll timeout, causing infinite spinning and significant memory leakage. Several approaches to stopping the spin and surfacing the correct error are represented.

## TL;DR

- 6 member(s): 0 open issue(s), 1 closed issue(s), 0 open PR(s), 1 merged PR(s), 4 PR(s) closed without merging.
- A fix was merged to main in PR #67183. Verify it addresses your case.
- **Recommended:** read PR #67183 (and any competing PRs below) before filing. Confirm the merged change covers your symptom.

## Maintainer resolution verdict

- Internal-tracker verdict over this cluster's issue members: `resolved` · deciding PR(s): `pr-67183`. This is distinct from the fix status above. Weigh it yourself.

## How this cluster was grouped

- Link evidence (`STRUCTURAL_SPANNING`): every member is connected by structural evidence: shared changed files, or a closing/superseded reference.
- Pairwise link density `0.33`: the share of member pairs that carry a link, counting a structural link in full and a relevance-only link at 0.36. `1.00` means every pair is linked.

## Closed / duplicate issues

- #63892: gateway OOM: MCP poll loop mistakes a completed future's real TimeoutError for a poll timeout (Py>=3.8 alias) and spins, leaking ~108MB/s of traceback

## Prior & competing PRs

- **#67183: fix(mcp): stop gateway OOM from poll loop swallowing a completed future's real TimeoutError (supersedes #63918, #64072, #63903, #66039)**. merged to main · fix tier `verified`
  - maintainer direction: category `merged`; implication `superseded`
  - files: `tests/tools/test_mcp_poll_loop_oom_integration.py`, `tests/tools/test_mcp_tool.py`, `tools/mcp_tool.py`
- **#63903: fix(mcp): resolve completed future in poll loop to stop TimeoutError spin (#63892)**. closed without merge
  - maintainer direction: category `implemented_elsewhere`; implication `superseded`; refs `#67183`
- **#63918: fix(mcp): propagate stored timeouts from completed futures**. closed without merge
  - maintainer direction: category `merged_via`; implication `superseded`; refs `#67183`
- **#64072: fix(mcp): surface completed future's real TimeoutError instead of spinning (_run_on_mcp_loop, #63892)**. closed without merge
  - maintainer direction: category `implemented_elsewhere`; implication `superseded`; refs `#67183`
- **#66039: fix: prevent OOM from MCP poll loop swallowing real TimeoutError (#63892)**. closed without merge
  - maintainer direction: category `superseded_by_pr`; implication `superseded`; refs `#67183`, `#63892`

## Fix status

- Merged to main in PR #67183 (cited above). No release data is tracked. Verify downstream.
- Fix last verified (merged) `2026-07-18`.
- Subsystem: `mcp`