fix: reap orphaned browser sessions on startup - #7931
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When a Python process exits uncleanly (SIGKILL, crash, gateway restart
via hermes update), in-memory _active_sessions tracking is lost but the
agent-browser node daemons and their Chromium child processes keep
running indefinitely. On a long-running system this causes unbounded
memory growth — 24 orphaned sessions consumed 7.6 GB on a production
machine over 9 days.
Add _reap_orphaned_browser_sessions() which scans the tmp directory for
agent-browser-{h_*,cdp_*} socket dirs on cleanup thread startup. For
each dir not tracked by the current process, reads the daemon PID file
and sends SIGTERM if the daemon is still alive. Handles edge cases:
dead PIDs, corrupt PID files, permission errors, foreign processes.
The reaper runs once on thread startup (not every 30s) to avoid races
with sessions being actively created by concurrent agents.
Tommyeds
pushed a commit
to Tommyeds/hermes-agent
that referenced
this pull request
Apr 12, 2026
When a Python process exits uncleanly (SIGKILL, crash, gateway restart
via hermes update), in-memory _active_sessions tracking is lost but the
agent-browser node daemons and their Chromium child processes keep
running indefinitely. On a long-running system this causes unbounded
memory growth — 24 orphaned sessions consumed 7.6 GB on a production
machine over 9 days.
Add _reap_orphaned_browser_sessions() which scans the tmp directory for
agent-browser-{h_*,cdp_*} socket dirs on cleanup thread startup. For
each dir not tracked by the current process, reads the daemon PID file
and sends SIGTERM if the daemon is still alive. Handles edge cases:
dead PIDs, corrupt PID files, permission errors, foreign processes.
The reaper runs once on thread startup (not every 30s) to avoid races
with sessions being actively created by concurrent agents.
This was referenced Apr 22, 2026
aj-nt
pushed a commit
to aj-nt/hermes-agent
that referenced
this pull request
May 1, 2026
When a Python process exits uncleanly (SIGKILL, crash, gateway restart
via hermes update), in-memory _active_sessions tracking is lost but the
agent-browser node daemons and their Chromium child processes keep
running indefinitely. On a long-running system this causes unbounded
memory growth — 24 orphaned sessions consumed 7.6 GB on a production
machine over 9 days.
Add _reap_orphaned_browser_sessions() which scans the tmp directory for
agent-browser-{h_*,cdp_*} socket dirs on cleanup thread startup. For
each dir not tracked by the current process, reads the daemon PID file
and sends SIGTERM if the daemon is still alive. Handles edge cases:
dead PIDs, corrupt PID files, permission errors, foreign processes.
The reaper runs once on thread startup (not every 30s) to avoid races
with sessions being actively created by concurrent agents.
02356abc
pushed a commit
to 02356abc/hermes-agent
that referenced
this pull request
May 14, 2026
When a Python process exits uncleanly (SIGKILL, crash, gateway restart
via hermes update), in-memory _active_sessions tracking is lost but the
agent-browser node daemons and their Chromium child processes keep
running indefinitely. On a long-running system this causes unbounded
memory growth — 24 orphaned sessions consumed 7.6 GB on a production
machine over 9 days.
Add _reap_orphaned_browser_sessions() which scans the tmp directory for
agent-browser-{h_*,cdp_*} socket dirs on cleanup thread startup. For
each dir not tracked by the current process, reads the daemon PID file
and sends SIGTERM if the daemon is still alive. Handles edge cases:
dead PIDs, corrupt PID files, permission errors, foreign processes.
The reaper runs once on thread startup (not every 30s) to avoid races
with sessions being actively created by concurrent agents.
gweeteve
pushed a commit
to gweeteve/hermes-agent
that referenced
this pull request
Jun 2, 2026
When a Python process exits uncleanly (SIGKILL, crash, gateway restart
via hermes update), in-memory _active_sessions tracking is lost but the
agent-browser node daemons and their Chromium child processes keep
running indefinitely. On a long-running system this causes unbounded
memory growth — 24 orphaned sessions consumed 7.6 GB on a production
machine over 9 days.
Add _reap_orphaned_browser_sessions() which scans the tmp directory for
agent-browser-{h_*,cdp_*} socket dirs on cleanup thread startup. For
each dir not tracked by the current process, reads the daemon PID file
and sends SIGTERM if the daemon is still alive. Handles edge cases:
dead PIDs, corrupt PID files, permission errors, foreign processes.
The reaper runs once on thread startup (not every 30s) to avoid races
with sessions being actively created by concurrent agents.
waefrebeorn
pushed a commit
to waefrebeorn/slermes
that referenced
this pull request
Jul 2, 2026
When a Python process exits uncleanly (SIGKILL, crash, gateway restart
via hermes update), in-memory _active_sessions tracking is lost but the
agent-browser node daemons and their Chromium child processes keep
running indefinitely. On a long-running system this causes unbounded
memory growth — 24 orphaned sessions consumed 7.6 GB on a production
machine over 9 days.
Add _reap_orphaned_browser_sessions() which scans the tmp directory for
agent-browser-{h_*,cdp_*} socket dirs on cleanup thread startup. For
each dir not tracked by the current process, reads the daemon PID file
and sends SIGTERM if the daemon is still alive. Handles edge cases:
dead PIDs, corrupt PID files, permission errors, foreign processes.
The reaper runs once on thread startup (not every 30s) to avoid races
with sessions being actively created by concurrent agents.
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Summary
When the Python process that created a browser session exits uncleanly (SIGKILL, crash, gateway restart via
hermes update), the in-memory_active_sessionstracking is lost but the agent-browser node daemons and their Chromium child processes keep running indefinitely.Impact found on production: 24 orphaned sessions accumulated over 9 days, spawning 140 processes (node + Chromium trees) consuming 7.6 GB of RAM. Memory watchdog showed steady growth from 30% to 64% over 3 weeks, with these zombies as the primary cause.
Changes
_reap_orphaned_browser_sessions()totools/browser_tool.py/tmp/agent-browser-{h_*,cdp_*}/socket dirs on cleanup thread startup_active_sessions, reads the daemon PID file_browser_cleanup_thread_worker()before the periodic loopTest plan