Complete re-review of PR #188 (commits 224cab6 feature + 2c27fc5 perf/i18n follow-up). Gatekeeper focus: standards, correctness, perf/complexity, and translation completeness.
What this changes (pre -> post)
Pre: timeline primarily navigation/hover preview; bulk delete selection message-level and token metrics tied to backend assistant output tokens (missing tool payload weight).
Post: segment-level timeline selection + range (Shift) + toggle (Ctrl/Meta) + mobile long-press; histogram ribs overlay showing relative + absolute (~10k cap) token weight; assistant-turn grouping to avoid adjacency bugs; bulk-delete toolbar shows Before / Selection / After token pills.
Code standards / correctness
OK: Solid signal/memo/effect patterns with cleanup; no obvious lifecycle leaks. Grouping avoids adjacency overlap by mapping messageId to turns.
Fix: selection-id stability is mitigated by pruning stale ids after segment rebuilds; long term stable ids from part ids/toolPartIds remain recommended.
Fix: token counts now share getPartCharCount in both x-ray overlay and bulk-delete toolbar, keeping estimates consistent with live store updates.
Performance / complexity
OK: O(n^2) hotspots removed for liveSegmentChars and selectedTokenTotal. groupRole + deleteUpTo hover checks now memoize messageId sets/maps.
Note: getPartCharCount can be heavy for large tool payloads but remains gated behind selection mode.
CSS / UI integration
Fix: x-ray token label now uses theme tokens instead of hard-coded colors. Delete toolbar now uses menu-based controls with selection-mode toggle.
i18n
Fix: selection hint now renders Cmd/Ctrl via localized modifier placeholder; all locales updated.
Addresses bot review feedback on commit 224cab6.
## Performance: liveSegmentChars O(n²) → O(n)
The memo had three inner loops scanning all props.segments per unique
messageId. Added a single O(n) pre-pass building a
segmentsByMessageId Map, then replaced all three inner loops with
map lookups. Total complexity: O(n) instead of O(m×n).
File: packages/ui/src/components/message-timeline.tsx
## Performance: selectedTokenTotal O(n²) → O(n)
For each selected messageId, the memo scanned all segments to sum
chars. On "Select all" this was O(selected × segments). Now builds a
charsByMessageId map in one O(n) pass and does O(1) lookups per
selected message. Same pattern as aggregateTokensByMessageId.
File: packages/ui/src/components/message-section.tsx
## SSR guard: resize listener
window.addEventListener("resize", computeBadgeLayout) lacked a
typeof window !== "undefined" guard. Other window usage in the file
was guarded. Wrapped the addEventListener, requestAnimationFrame, and
onCleanup block in the guard.
File: packages/ui/src/components/message-timeline.tsx
## i18n: mirror selectionHint key in 5 locale files
messageSection.bulkDelete.selectionHint was only defined in
en/messaging.ts. Added the key (English string, since Ctrl/Shift/Esc
are universal keyboard labels) to es, fr, ja, ru, and zh-Hans.
Files: packages/ui/src/lib/i18n/messages/{es,fr,ja,ru,zh-Hans}/messaging.ts
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
