fix(components): stop sidebar resize chat jitter

[wibus-wee]

Related issue

Same-repository fix; no tracking issue was required for intake.

Problem / pressure

Opening or closing the desktop navigation sidebar animates the conversation viewport width. The sticky-scroll viewport observer treated every width-only ResizeObserver record as a reason to re-anchor Virtua at the bottom, competing with use-stick-to-bottom and making the conversation move vertically by a few pixels.

Summary

• Ignore viewport ResizeObserver records when the viewport height did not change.
• Preserve height-driven re-anchoring for keyboard, terminal dock, and window layout changes.
• Add a regression test that emits several consecutive width-only resize records while the conversation remains sticky.
• Record the adapter ownership boundary in the scoped hooks contributor guidance.

Before / after

Before	After
Every sidebar animation frame could request a Virtua bottom re-anchor.	Width-only sidebar animation frames leave the vertical scroll position untouched.
Viewport height changes kept a sticky conversation pinned to the bottom.	Viewport height changes continue to keep a sticky conversation pinned to the bottom.

Test plan

• pnpm exec vitest run tests/use-sticky-scroll.test.ts from packages/components: 7 tests passed.
• pnpm typecheck from packages/components: passed.
• pnpm exec prettier --check src/hooks/use-sticky-scroll.ts tests/use-sticky-scroll.test.ts src/hooks/AGENTS.md: passed.
• git diff --check: passed.

Context handoff

Instructions for reviewing agents

• Review focus: Check the height-only filter in use-sticky-scroll.ts and the repeated width-resize regression in use-sticky-scroll.test.ts.
• Decisions to challenge: Confirm that content reflow remains owned by use-stick-to-bottom while the app adapter owns only viewport height re-anchoring.
• Plausible failures / evidence gaps: A browser-level Electron interaction test was not run; evidence is the focused deterministic ResizeObserver test plus the existing height/content-growth cases.

Authoring context

• User goal / directives: Remove the visible vertical conversation jitter when toggling the desktop sidebar and publish the fix as a PR.
• Constraints / non-goals: Preserve sticky streaming, user escape behavior, composer suppression, session restoration, and keyboard or terminal height handling; do not redesign the sidebar animation.
• Risk-bearing decisions: Width-only viewport changes are ignored by the Virtua adapter because content-height changes continue through the library's content observer.
• Destructive or irreversible behavior: The change performs no data mutation, migration, deletion, or irreversible operation.
• Deliberately not done or tested: Full Electron end-to-end interaction was omitted because the deterministic hook suite directly exercises the conflicting observer path.
• Unknowns / confidence: Confidence is high for the reported path; platform-specific ResizeObserver scheduling remains covered indirectly rather than by a packaged-app test.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-04T03:03:19.987834Z	b9730d1	PR opened

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