Summary

agent/lsp/manager.py defines DEFAULT_IDLE_TIMEOUT = 600 (line 66) and assigns it to self._idle_timeout (line 167), but no reaper exists. Idle LSP subprocesses live forever inside a long-running gateway / CLI session.

A long-lived gateway process accumulates one LSP subprocess per (language, workspace) ever touched. Realistic memory cost:

• pyright ~200 MB
• gopls ~80 MB
• tsserver ~150 MB
• rust-analyzer ~300+ MB

A gateway that sees edits across 5–10 different repos in different languages over a day-long session ends up holding ~1–2 GB of dead LSP subprocesses with no path to reclaim until the gateway restarts.

Repro

Spawn a gateway, edit .py in repo A, edit .go in repo B, edit .rs in repo C, leave the gateway running for an hour, watch ps aux | grep -E 'pyright|gopls|rust-analyzer' — none of them get reaped.

Locations

• agent/lsp/manager.py:66 — DEFAULT_IDLE_TIMEOUT = 600
• agent/lsp/manager.py:157 — idle_timeout: float = DEFAULT_IDLE_TIMEOUT,
• agent/lsp/manager.py:167 — self._idle_timeout = idle_timeout

grep -n '_reaper_loop\|_reap_idle' agent/lsp/manager.py returns no hits — the constant is wired into the constructor signature but nothing consumes it.

Proposed fix

Background reaper coroutine scheduled on _BackgroundLoop:

async def _reaper_loop(self):
    while True:
        await asyncio.sleep(self._idle_timeout / 2)
        self._reap_idle()

_reap_idle() is the unit-testable single pass — iterate self._last_used, tear down clients whose timestamp is older than now - self._idle_timeout. Schedule via _BackgroundLoop.schedule() in __init__ when enabled; cancel the handle in shutdown().

A note on cleanup: agent/lsp/__init__.py:75 already registers an atexit hook that tears down everything on process exit, so this issue is purely about reclaiming memory during a long-lived session, not at exit.

This was verified-real in scubamount's PR #24467 (defect D3). Credit to @scubamount for the original analysis. Filing as a standalone issue with a focused fix scope rather than the bundled refactor in that PR.