perf(app): stop the per-second shell re-render and halve bundled renderer assets

[ozymandiashh]

Three quiet desktop inefficiencies, each measured before and after, each pinned by a regression test.

Update after merging main (#1459, #1462). #1459 replaced the flame art with onboarding-flame.png and deleted flame.png, so this PR's 192 px cut of the old art no longer applies and is removed; the flame parts of §3 and the table below are superseded. What remains of §3 is the splash re-encode. #1459's footer (RefreshMark) is kept as is, rendered from the leaf RefreshedAt so only it ticks. Section 2 was dropped in review (see CLI memo: dropped).

1. The shell stops re-rendering once a second

AppMain owned a wall-clock setInterval(1000) whose only consumer was the footer's "refreshed Ns ago" label, but every tick reconciled the whole tree — sidebar, hero, daily chart, activity heatmap, every table — 60 times a minute whether or not any data had changed.

The per-second tick now lives in a leaf RefreshedAt component that owns just that label. The shell re-renders on real state changes plus a 15-second day check that fires exactly when the local calendar rolls over; that rollover matters because the overview memo keys bake in a today/month boundary, so midnight must still produce one re-render to keep "Today" honest.

App.renderChurn.test.tsx pins both properties: on the base the shell re-rendered on every clock tick and on same-day checks, on this branch neither.

2. CLI resolution stops re-scanning the filesystem per request

Every read (each section poll, each prefetch warm) resolved the codeburn binary from scratch: a stat sweep over every PATH entry plus a readdir of the nvm versions tree — per request, purely to return the same path.

Resolution and the derived spawn PATH are memoized against the full set of inputs that can change the answer (CODEBURN_BIN, CODEBURN_BUNDLED_CLI, the dev-server and persisted-path overrides, CODEBURN_PATH_DIRS, PATH, NVM_DIR), so an unchanged environment costs a string compare. Safety valves:

• a miss is never cached, so a CLI installed — or a path persisted via locate-CLI — while the app is open is still discovered on the next read;
• a spawn error drops the memo, so a deleted binary cannot pin the app to a dead path (covered by a test that deletes the resolved binary and watches the next request find the successor);
• __resetCliResolutionForTests() keeps one test's filesystem layout out of the next.

Measured on this machine (18 PATH entries): 26.5 µs → 2.6 µs per resolution, and the syscalls leave the steady-state path entirely.

3. Splash video halves

The cold-start splash shipped a 2.6 MB VP9 clip.

• splash-loader.webm: re-encoded at VP9 CRF 30 — 1.29 MB, −50%, SSIM 0.994 against the source; video-only file, no audio track affected.

dist/renderer after merging main: 3,924 KB → 2,672 KB (local vite build). The JS bundle is untouched.

Proof (per review)

Render churn. Pinned by app/renderer/App.renderChurn.test.tsx: the shell's overview render count does not move across five 1 s ticks (growth ≤ 2, vs one render per tick before), rolls exactly once across the midnight boundary, and — the counterpart added for this review — the footer label still ticks every second (just now → 1s ago → 2s ago) while that same shell count stays flat. Reviewer's own measurement on his machine: AppMain renders over 10 s idle, 10 → 0.

Asset weight, per file (before merging main; the flame row is superseded by #1459's new art):

file	main	this PR	Δ
splash.webm	2,522 KB	1,264 KB	−1,257 KB
flame (880 px → 192 px cut)	696 KB	52 KB	−643 KB
index.css	91 KB	90 KB	~0
index.js	591 KB	591 KB	~0
assets total	4,177 KB	2,275 KB	−1,902 KB

dist/renderer: 4,228 KB → 2,328 KB locally (reviewer measured 4,200 → 2,300 on his machine).

CLI memo: dropped. Per the review, the memoization is removed entirely (b260394) — cli.ts and cli.test.ts restore to their pre-PR shape. 23 µs → 2 µs at a multi-second poll cadence was never user-visible, and the env key hashed the CLI-path file's path, not its contents, so a newly persisted path could never displace a successful resolution (the invalidation test wrote its successor to the same path and passed with a stale memo). Drop beats re-keying.

flame.png: deleted from the repo (713 KB, no importer after the cut). Main has since deleted it too, and the cut is gone with the merge.

Verification

• tsc --noEmit clean
• full app/ suite green after the review fixes: 1,000 passed, 4 skipped
• npm run build green
• churn tests verified to fail on the pre-change code and pass after
• deliberately out of scope: bundle code-splitting (gsap ~50 kB of the 510 kB chunk) — separate PR material

Changed

• The desktop shell stops re-rendering the whole tree once a second. AppMain owned a wall-clock setInterval(1000) that existed only so the footer could print "refreshed Ns ago", but every tick re-rendered the sidebar, the hero, the daily chart, the heatmap and every table 60 times a minute whether or not any data had changed. The per-second tick now lives in a leaf RefreshedAt component that owns just that label, and the shell itself re-renders only on real state changes plus a 15-second day check that fires exactly when the local calendar rolls over. Renderer render-count regressions are pinned by a churn test.

Fixed

• The renderer ships half the splash video weight. The cold-start splash video is re-encoded at VP9 CRF 30 (SSIM 0.994 against the source), taking app/renderer/assets/splash-loader.webm from 2,582,836 bytes to 1,294,904 bytes — about half.

[iamtoruk]

Measured on my machine. The render churn and the asset cut both check out: AppMain renders over 10 s idle on Overview went 10 to 0, and dist/renderer went 4,200 KB to 2,300 KB with the same 19 assets. Post the proof in the PR body so it survives: render count before and after or a CPU sample, the asset size table per file, and confirmation the "refreshed Ns ago" text still ticks every second.

On the CLI memo: 23 µs to 2 µs per resolution at a multi-second poll cadence is not a user-visible win, and the memo adds stale-path surface. The env key hashes the path of the CLI-path file, not its contents, so once resolution succeeds a newly persisted path is never picked up. The invalidation test writes the successor to the same path, so it passes with a stale memo too. Either drop the memo or key on the file contents and rewrite that test to use a different path.

Also: flame.png is still in the repo at 713 KB with no importer. Delete it.

Heads up: this conflicts with a branch of mine that rewrites the same footer line and still reads now. Whoever lands second merges by hand.

No screenshots needed, nothing visible changed.

[ozymandiashh]

b260394 addresses the review:

• CLI memo dropped entirely. cli.ts and cli.test.ts restore to their pre-PR shape — you were right that the env key hashed the CLI-path file's path rather than its contents, and the test's same-path successor could never catch it. Given the win was invisible at poll cadence, drop beats re-keying.
• flame.png deleted from the repo (713 KB, unimported).
• Proof posted in the PR body: the per-file asset table (main vs branch, same 19 assets), the churn-test render counts including the new counterpart pin — the refreshed Ns ago label ticks just now → 1s ago → 2s ago while the shell's render count stays flat — and my local dist/renderer numbers (4,228 → 2,328 KB) alongside yours.

Noted on the footer-line conflict with your branch — happy to be second and merge by hand.

[ozymandiashh]

Heads-up: pushes to this branch after 96807e7 (b260394, c98410a) have started no workflow runs at all — gh pr checks reports none, and the actions API shows zero runs for the new heads, while my other PRs from the same fork trigger normally. If a workflow approval got dropped along the way, a re-run (or an approval of the pending ones) would be appreciated; the review-fix commit is b260394, c98410a is only an empty re-trigger.

[ozymandiashh]

Merged main (#1459, #1462) by hand in cc47e20, as agreed for the footer line:

• Footer: your RefreshMark is kept byte for byte (fixed icon, spinner only while refreshing, sr-only status). RefreshedAt now renders it, so the 1 s tick still stays out of AppMain, and the day-rollover check still recomputes the memo keys at midnight. App.renderChurn.test.tsx passes on the merge, and so does the full app suite.
• Flame: Desktop: measured polish pass, new frame, card system, motion, onboarding #1459 replaced the art with onboarding-flame.png, so my 192 px cut of the old art no longer applies. It's deleted (8018118), and the changelog bullet now covers only the splash re-encode. After the merge, dist/renderer goes from 3,924 KB to 2,672 KB. The PR body is updated to match.

CI runs start again on the new head, all green.