[teamleaderleo]

Summary

Leo, on New Tab in his build: two scrollbars (the page's own at the window edge and the Chats list's inside it), and the list sliced half a row right above the template dots.

• One scroller. With the All chats list, the list takes the room left under the field and is the only scroller. In a short window it gives up rows instead of pushing the page past the window (before, its 240 px minimum did, and the page scrolled too). Only when there's no room for two rows of list does the page scroll, so nothing is ever out of reach.
• Soft edges. The list fades out under its top and bottom edges instead of cutting a row, as Settings does (cmux-next: Settings scrolls in one place (cx-jh7kq) #19763). The fades sit over end padding, so the first and last rows are in full ink. The page itself never fades: the composer's model menu opens inside it.

The scrollbar's own look (thin, shown only while scrolling, app-wide) is a separate PR, because it changes the SCROLLBARS-FOLLOW-MACOS rule and its guard.

Testing

• webviews/test/new-tab-scroll.test.ts (new, browser lane): the real gallery stages in Chromium.
  • many-chats at 900×360: one scroller (nt-all-list), the document never scrolls, the list fades, the page doesn't. Red at 84c2525 (two scrollers, no fade).
  • many-chats at 260 px: at least two rows of list, and the page can scroll to the rest. calm-default: at most one scroller, no page fade. Both added after review: red at f2af282 against the first fix (the list collapsed to nothing; the page fade dimmed the model menu).
  • Green at 5d9a03e.
• bun run check passes. The New Tab tests (calm default, field focus, dictation, places) pass.
• A review subagent measured the stages in Chromium; its three findings are fixed above.

Changelog

Fixed: New Tab scrolls in one place, and its lists fade out at their edges instead of cutting a row

Proof

The boundary test above (red, then green). The gallery's agent-pane.new-tab many-chats stage shows it in a short window.

🤖 Generated with Claude Code

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Summary by cubic

Fixes New Tab's double scrollbar: with an All chats list, the list is the page's only scroller and the document never scrolls; without the list (the calm default), the page itself scrolls. Either scroller fades out under its top and bottom edges instead of slicing a row, matching Settings behavior.

• The list now keeps two full rows in a short window; below that the page itself scrolls, so nothing is out of reach.
• Only the list fades; the page never fades, because a page fade would dim the composer's model menu (it opens inside the page). The fades sit in the list's end padding, so the first and last rows stay in full ink.
• Adds a Chromium browser test (new-tab-scroll.test.ts) that stages the real gallery at 900×360 and asserts one scroller, no document scroll, and the edge fade for both many-chats and calm-default.

^{Written for commit 5d9a03e. Summary will update on new commits.}

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[blacksmith-sh]

Found 1 test failure on Blacksmith runners:

Failure

Test	View Logs
test/chat-header-changes.test.tsx/chat-header-changes.test.tsx	View Logs

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[github-actions]

Unclear: web / react-apps-check failed: no known signature; failed step: Test webviews.

CI failed on 5d9a03eda3 (run 38226085273 attempt 1): 1 unknown.

Job	Verdict	Why
web / react-apps-check	unknown	no known signature; failed step: Test webviews

Not re-run automatically: web / react-apps-check is not a machine failure.

Written by scripts/ci/classify_failures.py (ci-failure-attribution.yml); signatures are its SIGNATURES table. A machine verdict is the runner's fault, not this PR's; yours means the failing file is one this PR changes, also red on main that main's latest full suite fails the same way, seen on other PRs that it failed on another pull request's run lately.

[github-actions]

CI fast guards failed on 5d9a03eda3 (https://github.com/manaflow-ai/cmux/actions/runs/38226085273). It does not block the merge; a red guard merged into main breaks it for every open PR.
The log named no failed step; see the run.

Agents: python3 scripts/ci/guard_attribution.py fix applies the mechanical fixes locally. This comment is updated in place on each push.

[github-actions]

Gallery

Review in feed

130 states changed: agent-pane.history/selected, agent-pane.history/chats, agent-pane.new-tab/template-threads, agent-pane.new-tab/template-console, agent-pane.new-tab/switcher-on, ... · 36 play checks failed

Diff page and renders (the run's gallery-pr artifact)

State	Before · after
agent-pane.history/selected (Apple System Colors Light, webkit)
agent-pane.history/selected (Apple System Colors Light, chromium)
agent-pane.history/selected (Apple System Colors, chromium)
agent-pane.history/chats (Apple System Colors Light, chromium)
agent-pane.history/chats (Apple System Colors Light, webkit)
agent-pane.history/selected (Apple System Colors, webkit)

124 more on the diff page.

Live preview (follows this branch; start it with scripts/gallery-live.sh up <branch> from an hq checkout):

• agent-pane.history/selected: /wt/fix-new-tab-scroll/?entry=agent-pane.history#/agent-pane.history/selected
• agent-pane.history/chats: /wt/fix-new-tab-scroll/?entry=agent-pane.history#/agent-pane.history/chats
• agent-pane.new-tab/template-threads: /wt/fix-new-tab-scroll/?entry=agent-pane.new-tab#/agent-pane.new-tab/template-threads
• agent-pane.new-tab/template-console: /wt/fix-new-tab-scroll/?entry=agent-pane.new-tab#/agent-pane.new-tab/template-console
• agent-pane.new-tab/switcher-on: /wt/fix-new-tab-scroll/?entry=agent-pane.new-tab#/agent-pane.new-tab/switcher-on
• agent-pane.new-tab/recently-closed: /wt/fix-new-tab-scroll/?entry=agent-pane.new-tab#/agent-pane.new-tab/recently-closed
• 48 more on the diff page

Play checks failed (0 px anchor movement, 0 layout shift, no frame over 33 ms unless the entry gives a reason):

• agent-pane.composer-pickers/model-press-drag-release (Apple System Colors, webkit): play: no element for [role="option"][data-key="model:gpt-6-astra"]
• agent-pane.composer/queued-send-remove (Apple System Colors, chromium): step 2 click .acpmux-queued:first-child button[aria-label="Remove queued prompt"]: layout shift 0.0106 (limit 0) · step 3 click button "Stop": layout shift 0.0074 (limit 0)
• agent-pane.composer-pickers/effort-press-drag-release (Apple System Colors, chromium): step 3 up text "High": layout shift 0.0010 (limit 0)
• agent-pane.header-tools/worktree-remove (Apple System Colors Light, chromium): step 1 click .acpmux-header-worktree: layout shift 0.0083 (limit 0)
• agent-pane.header-tools/worktree-remove (Apple System Colors, chromium): step 1 click .acpmux-header-worktree: layout shift 0.0083 (limit 0)
• agent-pane.transcript/thought-row (Apple System Colors Light, chromium): step 1 click button.cv-thought: layout shift 0.0004 (limit 0)
• 172 more on the diff page

217 nondeterministic states differed from a second render of the same head (a clock or fixture leak) and are not counted as changes.

_{1541 unchanged · base bf3cac7 · head 5d9a03e}