perf(ui): stabilize snapshot slice identity so sidebar memos hit#34
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The sidebar ref-tree builds were already memoized, but refreshSnapshot replaced status/workTree/refs/submodules/meta with freshly deserialized objects on every refresh, so input identity churned on every stage toggle and watcher tick and every memo rebuilt for identical data. - lib/stable.ts: stable(prev, next) keeps the previous reference when the new value is structurally equal (jsonEqual, early-exit walk). Applied to every snapshot-fed slice and the standalone refreshStatus/ refreshRefs/refreshTree/refreshSubmodules setters; the per-tab meta patch also skips when the tab meta is unchanged. - Sidebar: drop the status dep from the Files-tab effect — since the repo_snapshot batch, every status-changing path already refreshes workTree from the same statuses walk, so the effect IPC-walked the working tree a second time on every stage toggle. It now runs only on tab show / repo switch (the lazy first load). - Sidebar: precompute folder leaf counts once per tree build (countLeaves fills TreeNode.leaves) instead of recursing per folder row on every render. Closes the last open item under TASKS - Performance - Audit follow-ups. Verified: tsc, vitest (198, +13 stable), vite build.
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Summary
Closes the last open item under TASKS → Performance → Audit follow-ups ("Sidebar: memoize ref-tree builds /
leafCount; debouncerefreshTreeoff thestatusdep").Root-caused one level down: the sidebar ref-tree builds were already
useMemo'd — they rebuilt anyway becauserefreshSnapshotreplacedstatus/workTree/refs/submodules/metawith freshly deserialized objects on every refresh, so input identity churned on every stage toggle and watcher tick.ui/src/lib/stable.ts—stable(prev, next)returns the previous reference when the new value is structurally equal (jsonEqual, early-exit walk so the something-changed case stays cheap). Applied to every snapshot-fed slice and the standalonerefreshStatus/refreshRefs/refreshTree/refreshSubmodulessetters; the per-tab meta patch also keepstabsidentity when the tab meta is unchanged. Unchanged slices keep their identity, so the sidebar ref trees, palette index, and FilesPierreTreestop rebuilding — and their zustand selector subscribers stop re-rendering — for identical data.statusdep is removed rather than debounced: since therepo_snapshotbatch, every status-changing path already refreshesworkTreefrom the same statuses walk, so the effect'srepo_treeIPC was a redundant second walk of the working tree on every stage toggle. It now runs only on tab show / repo switch (the lazy first load).countLeavesfillsTreeNode.leaves) instead of recursing per folder row on every render.Audited all consumers before stabilizing: nothing keys effects off these slices' identity as a "refresh tick" — every dependent is a pure memo/callback, so keep-if-equal is behavior-preserving.
Test plan
tsc --noEmit— cleanvitest run— 198 tests pass (+13 new forjsonEqual/stable: primitives, null vs undefined, arrays, nested objects, key-set mismatch, identity-keeping semantics)vite build— clean🤖 Generated with Claude Code