Closing a tab took ~0.55-0.7s on an idle machine, more with child
processes or recently active subagents. Most of it was waiting:
- The web UI kept the tab until DELETE returned, then removed it on the
100ms tab-render debounce, which every session update restarts.
closeSession() is now optimistic: the tab, tile and split go and the
next session is selected before the request is sent, rendered at
once. A refused delete (checked with a GET, since a delete can land
and lose its reply) puts the row back at its old index with the
error toast. This also fixes a latent bug: _apiDelete never throws,
so an HTTP error used to report "Session closed" while the session
kept running. SSE upserts skip ids that are being closed.
- The kill path slept fixed intervals (100ms PTY grace, 200ms for the
pane's children, 100ms for the process group) and verified in 100ms
steps. waitForProcessesExit() (utils/process-exit-wait.ts) keeps
every deadline but returns once the processes are gone, counting a
zombie as exited. Signal decisions keep kill(pid, 0).
- tmux kill-session and the pane-pid lookup ran via execSync, freezing
the server for ~70ms per close. Now async.
- killSubagentsForSession() ran a full `pgrep -f claude` scan per
active/idle subagent (~85ms each with ~100 matching processes). It
now scans once for all of them.
Measured on an isolated instance: click to tab gone 540-690ms -> 58-95ms;
DELETE of a claude session ~450ms -> ~200-260ms.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
