Keeps the existing persistent-progress indicator visible when scrolling back through a running chat. The original element moves with the transcript until it reaches the bottom edge, then stays directly above the session pills, or above the input when no pills are present. Scrolling back restores its normal position.

Changes and implications

• Adds opt-in bottom-sticky support to the tree and reference-counted retention of a rendered list row. The live progress stays in its original DOM parent and document order; it is not copied or reparented, preserving its focus, interactions, and animation state across scrolling and response refreshes.
• Retains the active response row while it is needed for progress. Other rows remain virtualized, and completion, cancellation, hiding, clearing, or disabling persistent progress releases the hold.
• Separates the pills/input boundary from decorative pet scroll padding. Top-input layouts retain their existing behavior.
• Updates clamping before paint when response content or the input changes size. Preserves flex-child width when the row becomes sticky, preventing terminal wrapping from feeding back into layout.
• Updates setting descriptions and accessibility help, with regression coverage and component scenarios for pills, no pills, pets, fractional zoom, and expanded terminal output.

Behavior verification

With persistent progress enabled, start a response, scroll its progress toward the input, continue into earlier turns, then return to the response. Repeat with and without session pills and with an expanded terminal. There should be one live progress indicator, no change in terminal width, and no movement of the indicator once clamped.

npm run gulp compile-client — passed, including client type checking.

The following regression selection passed: 1,253 tests, 6 pending.

./scripts/test.sh --reporter dot \
  --run src/vs/base/test/browser/ui/list/listView.test.ts \
  --run src/vs/base/test/browser/ui/list/listWidget.test.ts \
  --run src/vs/base/test/browser/ui/tree/objectTree.test.ts \
  --run src/vs/workbench/contrib/chat/test/browser/widget/chatListWidget.test.ts \
  --run src/vs/workbench/contrib/chat/test/browser/widget/chatListRenderer.test.ts \
  --run src/vs/workbench/contrib/chat/test/browser/widget/chatWidget.test.ts \
  --run src/vs/workbench/contrib/chat/test/browser/accessibility/chatAccessibilityHelp.test.ts \
  --run src/vs/workbench/contrib/chat/test/browser/chatConfiguration.test.ts