sessions: speed up split chat tab closing - #333014
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Connor Peet (connor4312) merged 3 commits intoAug 27, 2026
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Reduce synchronous UI work when a user closes a chat tab in a split Agents window. - Remove an orphaned split group before its empty chat assignment creates a temporary new-chat view. - Update active-chat, visibility, and session-action state without rebuilding all chat tabs. - Cache the observed tab bar height instead of reading layout during each group layout. - Preserve active tab ARIA state and atomic split-chat replacement behavior. - Add focused regression tests for the optimized paths. Performance trace comparison: | Measurement | Original | Updated | Improvement | | --- | ---: | ---: | ---: | | Close 1 click handler | 242.1 ms | 1.07 ms | 99.6% | | Close 1 complete input task | 243.2 ms | 5.12 ms | 97.9% | | Close 2 click handler | 298.1 ms | 0.95 ms | 99.7% | | Close 2 complete input task | 298.8 ms | 4.54 ms | 98.5% | Style recalculations fell from 182/151 to 1/1, and layout passes fell from 188/156 to 0/0. (Commit message generated by Copilot) Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
…plit-chat-tab-closing
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📬 CODENOTIFYThe following users are being notified based on files changed in this PR: Benjamin Christopher Simmonds (@benibenj)Matched files:
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Copilot review overview
Review tier: Balanced
Findings: 1
New issues introduced by this change (2)
| Severity | Finding |
|---|---|
 |
src/vs/sessions/browser/parts/chatCompositeBar.ts — This optimized session-action update is not covered by the new DOM-identity regression. The… |
 |
src/vs/sessions/browser/parts/chatCompositeBar.ts — The new cached-height path is not covered by the regression tests. A stale or zero _height now… |
What changed in this PR
Optimizes split-chat tab closing in the Agents window.
Changes:
- Removes orphaned chat groups before reconciliation.
- Updates tab state without unnecessary rebuilding.
- Caches tab-bar height and adds regression coverage.
| File | Description |
|---|---|
chatGroupsView.ts |
Removes orphaned groups efficiently. |
chatCompositeBar.ts |
Optimizes tab updates and height measurement. |
chatGroupsView.test.ts |
Tests split-group removal and replacement. |
chatCompositeBar.test.ts |
Tests tab identity and ARIA state. |
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Add focused coverage for the optimized state and height update paths. - Verify that session-action visibility changes preserve existing chat tab elements. - Inject a ResizeObserver test seam into the chat composite bar. - Verify changed and repeated observed heights and border-box observation. (Commit message generated by Copilot) Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Anthony Kim (anthonykim1)
approved these changes
Aug 27, 2026
Connor Peet (connor4312)
deleted the
connor4312/optimize-split-chat-tab-closing
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August 27, 2026 19:59
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sessions: speed up split chat tab closing
Reduce synchronous UI work when a user closes a chat tab in a split Agents window.
Performance trace comparison:
Style recalculations fell from 182/151 to 1/1, and layout passes fell from 188/156 to 0/0.
(Commit message generated by Copilot)
Co-authored-by: Copilot 223556219+Copilot@users.noreply.github.com