[flamboh]

Note

🤖 Claude Opus 5.5 on behalf of Oliver

Fix for the redesign stack, targets layer 6 (#28845).

Problem

Swiping sideways over a terminal pane barely moves the pane strip, so it feels laggy. The same swipe over a thread pane is smooth.

The terminal's wheel handler cancelled every wheel event with any vertical movement. A trackpad's sideways swipe usually carries ±1px of vertical noise. Those events got cancelled, so the strip only moved on the few events with exactly zero vertical delta. Chromium on macOS usually locks a swipe to one axis, which hides the problem there. Firefox and Zen pass the noise through.

Fix

The terminal now leaves mostly-sideways wheel events alone. The strip scrolls them the same way it does over a thread pane. Mostly-vertical events still scroll the terminal's scrollback.

Before

https://gh-file-drop-api-prod-galwoqjslzlnws6s.oliver-boorstein.workers.dev/f/193cc9a724042d74/before.mp4

After

https://gh-file-drop-api-prod-galwoqjslzlnws6s.oliver-boorstein.workers.dev/f/a0d370c72fcac0ff/after.mp4

Validation

The red dot marks the pointer. Each clip swipes sideways over the thread pane, then over the terminal pane.

Firefox, 8 sideways wheel events of 20px with ±1px vertical noise. The strip starts at 226px.

Pointer over	Before	After
Thread pane	66 (moved)	66 (moved)
Terminal pane	226 (stuck)	66 (moved)
Terminal pane, focused	226 (stuck)	66 (moved)

The same synthetic input gets the same result in Chromium. Vertical wheel over the terminal still scrolls about 26 rows of scrollback and leaves the strip where it is, in both browsers.

surface.test.ts has a new case that fails on the layer and passes here.

Made with Claude Opus 5.5 in Claude Code.

[macroscopeapp]

Approvability

Verdict: Approved at a3d13e4

Macroscope's review found this PR approvable — Sideways wheel gestures over terminals now remain available to scroll the pane strip, while vertical gestures retain existing terminal handling. The change is limited to UI gesture routing and carries no evident material data or operational risk.

^{You can add or adjust custom eligibility rules. Learn more.}