Switching sessions ran as one synchronous commit: sidebar highlight, URL,
a full timeline remount with markdown re-parse, and around nine requests,
so nothing changed on screen for 150-250ms after the click.
- ChatContainer swaps the timeline on a deferred copy of the selection, so
the active row, URL, and tab commit first and the timeline renders behind
them; selection policy keeps reading the live store value.
- The message fetch starts before the selection is published.
- Sidebar rows stop re-rendering on a project switch: directory-scoped sync
hooks read the runtime context and a subscribable current-directory source
instead of the directory-bearing context; the grouping builder reads git
branches through a ref and section caches key the branches they use;
descendant ids are keyed by content. Rows per switch went from 73 to 8.
- Markdown skips the async re-render when the settled cached blocks are
already painted, and mounts synchronously once its lazy module is loaded;
the module is preloaded at boot.
- A timeline reveal gate holds a freshly opened session at opacity 0 while
any provisional markdown paint catches up (250ms cap), then fades the whole
timeline in once, so text, tools, and recap appear together.
- Switch fan-out trimmed: knowledge summary deduped, MCP status refreshed only
when stale, non-repo directories cached by the git repo check, OpenChamber
defaults cached briefly, agent memory reused for the same project, goal
text cached, PWA manifest rebuilt after the switch settles.
- Header tabs snap into the active state and keep the title at the same
height in both states.
- Prefetch on row press; composer focus moved off the commit.
`bun run profile:switch` records ack/content latency, longest task, and
requests per switch, cold and warm, and compares runs against a baseline.
Measured warm switch: ack 228ms to about 40-60ms, content 228ms to about
100-120ms.
Adds `bun run profile:animation`: it serves an isolated fixture and measures
each animation variant directly, so comparing techniques takes seconds instead
of an application rebuild plus a streamed response.
The result is unambiguous and does not vary with element count, measured from 1
to 32: transform, opacity and filter cost zero extra style recalculations, while
the individual rotate property, background-position, border-color and box-shadow
each recalculate style 60 times a second, and geometry properties add layout on
top. Notably `rotate: 360deg` is not a cheap synonym for
`transform: rotate(360deg)`, and will-change, wrapper elements, containment and
stepped timing do not make a non-composited property cheap.
`scripts/perf/DOCUMENTATION.md` documents all four capture commands, how to
stand up a production build to measure against, how to read the artifacts, the
validity guarantees the scripts enforce, and the methodology rules, so this can
be handed to an agent as the entry point for measuring performance. It is linked
from the root guide's documentation anchors.
The theme skill gains an animation contract carrying the measured table, and the
performance skill points at the tooling documentation.
Bohdan Triapitsyn