# NousResearch/hermes-agent · Timeline rail geometry caching and scroll perf

## Open now

- Nothing open on GitHub.

These items concern repeated layout measurements (getBoundingClientRect) in the timeline rail scroll handler causing significant frame drops and input latency. The work involves caching rail geometry to avoid redundant reads during scrolling.

## TL;DR

- 4 member(s): 0 open issue(s), 1 closed issue(s), 0 open PR(s), 1 merged PR(s), 2 PR(s) closed without merging.
- A fix was merged to main in PR #128613. Verify it addresses your case.
- **Recommended:** read PR #128613 (and any competing PRs below) before filing. Confirm the merged change covers your symptom.

## Maintainer resolution verdict

- Internal-tracker verdict over this cluster's issue members: `resolved` · deciding PR(s): `pr-128613`. This is distinct from the fix status above. Weigh it yourself.

## How this cluster was grouped

- Link evidence (`STRUCTURAL_SPANNING`): every member is connected by structural evidence: shared changed files, or a closing/superseded reference.
- Pairwise link density `0.50`: the share of member pairs that carry a link, counting a structural link in full and a relevance-only link at 0.36. `1.00` means every pair is linked.

## Closed / duplicate issues

- #118782: \[Bug\]: Timeline-rail scroll handler re-measures every mounted turn every frame — 3.2s getBoundingClientRect in a 10.7s scroll trace, 60% dropped frames, ~0.7-0.8s scroll input latency on long sessions

## Prior & competing PRs

- **#128613: perf(desktop): avoid full transcript geometry sweeps for timeline position**. merged to main · fix tier `verified`
  - maintainer direction: category `merged`
  - files: `apps/desktop/e2e/messages-below-position.spec.ts`, `apps/desktop/e2e/timeline-position.spec.ts`, `apps/desktop/src/components/assistant-ui/thread/timeline-position.test.tsx`, `apps/desktop/src/components/assistant-ui/thread/timeline-position.ts`, `apps/desktop/src/components/assistant-ui/thread/timeline.tsx`, `apps/desktop/src/components/assistant-ui/thread/use-messages-below-perf.test.ts`, `apps/desktop/src/components/assistant-ui/thread/use-messages-below.test.tsx`, `apps/desktop/src/components/assistant-ui/thread/use-messages-below.ts`
- **#118786: fix(desktop): cache timeline rail geometry**. closed without merge
  - maintainer direction: category `superseded_by_pr`; implication `superseded`; refs `#128613`
- **#128568: perf(desktop): cache timeline rail geometry so scrolling reads no layout**. closed without merge
  - maintainer direction: category `superseded_by_pr`; implication `superseded`; refs `#128613`, `#125851`

## Fix status

- Merged to main in PR #128613 (cited above). No release data is tracked. Verify downstream.
- Fix last verified (merged) `2026-10-01`.