Hidden panes are exempt from pendingData flow control (main gate-drops
their bytes after ingestion), so N background agents ran unbounded ahead
on the one shared daemon->main stream socket (measured 192MB user-space
backlog) and visible-pane echo waited FIFO behind it — typing appeared
seconds late whenever several agents burst on a loaded machine
(8x512KB/s + 12 CPU spinners: p50 293ms fix-off; 12x1MB/s: 6.1s).
Mechanism (replaces producer pacing — no reveal catch-up, ever):
- Shallow socket write gate (128KB) + per-session fairness bypass bounds
echo latency by construction; kernel-flush refill sentinel keeps held
bulk draining at full speed (drain-only refill capped at ~8MB/s).
- Backgrounded sessions' queued output is keep-tail dropped (newest
512KB kept, in-order dataGap replaces the middle); a ~2MB GLOBAL
budget shrinks per-session keep-tails (floor 64KB) so a worktree
switch never waits behind the aggregate. Reply-eliciting query bytes
(DSR/DA/OSC probes) are salvaged from dropped spans.
- Notifications are structurally lossless: the daemon runs the same
shared scanners main uses (bell/OSC 133/pr-link/2031) over every byte
BEFORE drop decisions and relays facts in byte order; ordered
background markers hand scan authority back and forth, seeded with the
emulator's partial escape tail so a sequence split across the handoff
neither phantom-fires nor goes missing. Titles/agent-status stay
main-side (kept-tail convergent).
- Main: background = hidden AND no remote view subscriber (a live
mobile/web view is never thinned); on dataGap main resets cross-chunk
parse carries, drops the headless mobile mirror, and reuses the
hidden-drop model-restore marker.
Wire: three new stream events, tolerated within protocol v19 (old mains
ignore unknown events; old daemons never see the trigger). Kill
switches: ORCA_DAEMON_BACKGROUND_STREAM_DROP=0,
ORCA_DAEMON_SHALLOW_SOCKET_GATE=0.
A/B (pnpm bench:multi-workspace-typing): 8x512KB/s + 12 CPU workers
p50 293ms/p90 647ms -> 15/21ms (= baseline); 12x1MB/s 6,146ms -> 20ms;
light loads unchanged; zero missing echoes. Latin hidden-restore e2e
green (probe-verified aggregate-drain root cause). New deterministic
repro harness: tests/e2e/terminal-multi-workspace-typing-latency.spec.ts
+ CPU pressure workers.
Co-authored-by: Orca <help@stably.ai>
Jinwoo-HandOrca
d0b067e7f0