Session switching must be instant #128

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opened 2026-10-09 08:08:01 +00:00 by kayg · 3 comments

kayg commented

2026-10-09 08:08:01 +00:00

Owner

Owner (production 63b1f10e): switching a window to another session via the UI takes noticeable time; it must be instant. Measure through the real UI against the real server at the 300 ms profile (choice → first paint of the new session → live), find where the time goes (round trips, attach, snapshot, renderer re-init, layout), fix the client side (paint the cached last screen within a frame, keep renderers warm, never block on a round trip), and report backend costs for a Codex job. TASTE row main 9e99a8da.

Owner (production 63b1f10e): switching a window to another session via the UI takes noticeable time; it must be instant. Measure through the real UI against the real server at the 300 ms profile (choice → first paint of the new session → live), find where the time goes (round trips, attach, snapshot, renderer re-init, layout), fix the client side (paint the cached last screen within a frame, keep renderers warm, never block on a round trip), and report backend costs for a Codex job. TASTE row main 9e99a8da.

kayg commented

2026-10-09 09:41:02 +00:00

Author

Owner

Measured and fixed, branch canvas-switch, head 9a770037 (base dev 63b1f10e). Root cause: a stream opened on an already welcomed connection attached on stream 0 (handler ran inside openStream before the caller had its id); the server closed the socket and the page reconnected on every switch (1 socket -> 5 over 4 switches). Plus a new TerminalClient per switch and an empty terminal until the snapshot round trip. Also found: sidebar and palette opened a NEW shell instead of the session (live open() ignored session). Table (median first painted frame / live, ms): manager 174/174 -> 27/75 local, 589/589 -> 38/347 at 300 ms; sidebar 149 -> 23/123, 702 -> 23/380; palette 125 -> 16/80, 669 -> 22/374. Server side: attach to snapshot painted is one round trip plus ~30 ms; nothing slow found in Rust.

Measured and fixed, branch canvas-switch, head 9a770037 (base dev 63b1f10e). Root cause: a stream opened on an already welcomed connection attached on stream 0 (handler ran inside openStream before the caller had its id); the server closed the socket and the page reconnected on every switch (1 socket -> 5 over 4 switches). Plus a new TerminalClient per switch and an empty terminal until the snapshot round trip. Also found: sidebar and palette opened a NEW shell instead of the session (live open() ignored session). Table (median first painted frame / live, ms): manager 174/174 -> 27/75 local, 589/589 -> 38/347 at 300 ms; sidebar 149 -> 23/123, 702 -> 23/380; palette 125 -> 16/80, 669 -> 22/374. Server side: attach to snapshot painted is one round trip plus ~30 ms; nothing slow found in Rust.

kayg commented

2026-10-09 10:13:11 +00:00

Author

Owner

Deployed to production 2026-10-09 ~12:15 CEST: web build of dev 01a6d848 (server binary unchanged; rollback web.prev = 63b1f10e). Gate: scripts/verify fast EXIT 0; real-server specs 29/30 with the one failure (switch.spec keys acknowledged, load 48) passing 21/21 on three reruns.

Deployed to production 2026-10-09 ~12:15 CEST: web build of dev 01a6d848 (server binary unchanged; rollback web.prev = 63b1f10e). Gate: scripts/verify fast EXIT 0; real-server specs 29/30 with the one failure (switch.spec keys acknowledged, load 48) passing 21/21 on three reruns.