A resumed session opened on a blank pane: the agent's conversation came
back, the terminal history the operator was reading did not. Each PTY
bridge's replay ring is now mirrored to `<state_dir>/scrollback/<id>.bin`
and handed to the new bridge on resume, and on the recovery pass that
re-adopts a session tmux still holds — that one lost its ring with the
previous daemon too. Restored bytes go out ahead of the live ones, and
are dropped once the ring holds a full budget of new output of its own.
Flushed every 10 seconds by the liveness watcher, and once more when a
bridge is sealed on exit. The timer is the part that matters: a host
reboot runs no exit path at all, so a scrollback written only on a clean
shutdown is missing in exactly the case this exists for. Ten seconds
bounds the loss to the last few lines — this is visual continuity, not
state — and costs at most one file write per active session per tick,
since a session whose bridge has read nothing since the last flush is
skipped.
The file is capped at the existing `pty_replay_bytes` budget rather than
a second one, is deleted on kill and when recovery prunes a sidecar, and
a missing, unreadable or oversized one degrades to an empty pane instead
of failing the resume.
Closes#171
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
