fix(TabList): keep TabMenu arrow keys out of the tab strip

[korkt-kim]

User impact

A keyboard user opens a TabMenu, moves to an option, and presses Left or Right. Focus leaves the still-open menu and lands on the outer tab strip. The next key acts on a tab or the menu trigger, not the option the user was choosing.

Problem and solution fit

• Why it occurs: a menu-item keydown bubbles to TabList. The menu's vertical focus handler leaves horizontal arrows alone, and the outer useListFocus handles them as tab-strip navigation because it has no boundary configured.
• Why it harms the task: a key pressed inside the overflow menu moves focus away from its options without closing the menu.
• Why it matters: the visible menu and the keyboard's focus disagree, so the user has to get back into the menu to finish choosing a destination.

The fix gives the tab strip's existing focus hook a boundary, so a nested popup keeps its keys.

Expected behavior and authority

The WAI-ARIA APG menu pattern distinguishes a menu opened by a menu button from a menubar: Right Arrow does nothing on a leaf item when there is no menubar to move through. TabMenu is a menu button with leaf menuitemradio options, not a menubar submenu. Its horizontal arrows must not become navigation in the surrounding tab strip.

useListFocus already documents and implements boundarySelector for ignoring events owned by a nested list. The current component:TabList record governs edge compensation, not this keyboard behavior. No record changes.

Smallest restoration

One option in TabList.tsx: boundarySelector: '.astryx-tab-list, [popover]'. The selector names the common outer root, where the hook's ref lives; role="tablist" is on the inner strip. A key from the menu reaches its popover boundary first, while a key from the strip reaches its own root.

The regression test presses both horizontal arrows on an open menu item and checks that focus stays there and the menu stays open. A companion jsdom test checks that a role="tablist" inside a popover still navigates between its own tabs. A Core patch changeset accompanies them. This adds no API, default, visual change, or new key handling.

Evidence

• Reproduction before the change: real Chromium 149, core-tablist--with-menu. Open More and focus Reports. Right Arrow moves focus to Home; Left Arrow, tested from Reports again, moves focus to More. The popover remains open in both cases.
• Result after the change: both keys leave focus on Reports and keep the menu open.
• Representative unchanged path: in Chromium, menu Up/Down and Home/End still move between options, Escape closes the menu and returns focus to More, and the strip's Left/Right still move between More and Projects.
• Regression test or other mutation-sensitive proof: the new jsdom case fails against the pre-change TabList.tsx at the focus assertion after Right Arrow. With the change, all 131 targeted tests pass, including that case, tab-strip navigation inside a popover, menu selection and dismissal, and the Tabs DOM accessibility contracts.

Scope

• One defect is restored.
• Separable contradictory or unsettled tagalongs were removed or split.
• No new public API, visual representation, default, or interaction model is hidden under the bug-fix label.
• Public text and artifacts contain no internal Meta context.

Testing

pnpm exec vitest run packages/core/src/TabList/TabList.test.tsx \
  -t "leaves horizontal arrows to the open menu" --maxWorkers=4
  pre-change TabList.tsx: 1 failed (focus leaves the menu)

pnpm exec vitest run packages/core/src/TabList \
  packages/core/src/hooks/useListFocus.test.tsx --maxWorkers=4
  Test Files 3 passed (3) · Tests 131 passed (131)

ASTRYX_STRICT_LINT=1 pnpm exec eslint packages/core/src/TabList  ✓
pnpm -F @astryxdesign/core typecheck                           ✓
pnpm check:repo                                               ✓
pnpm build                                                    ✓

Chromium checks above used the existing Storybook story against the pre-change source and this branch. WebKit and Firefox were not run.

The PR is draft because full local validation is not green. pnpm lint:strict passed check:repo, then reported 992 errors in the ignored local artifact assets/theme-runtime-lab.generated.js; no TabList lint errors were reported. pnpm test --maxWorkers=4 reported two failures in apps/storybook/.storybook/story-tree.test.ts; the full run was then stopped and is not reported as passing. Those files are outside this diff.

[vercel]

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Project	Deployment	Actions	Updated
astryx	Ready	Preview	Oct 11, 2026 1:14pm UTC

[astracat-bot]

AI review status for this pull request.

Review status	Updated
❓ Needs maintainer input (for maintainers only)	Oct 11, 2026, 2:49 PM UTC

[github-actions]

PR Analysis Report

Preview availability: Storybook and Sandbox are not both ready on the exact-head Vercel preview.

No new or modified components detected.

Bundle Size Summary

Package	Size (ESM)	Size (CJS)	Gzipped
@astryxdesign/core	N/A	4.9KB	1.2KB

Accessibility Audit

Status: No accessibility violations detected.

Visual Regression

23 of 446 shot(s) changed.

A change here is a question, not a failure: check whether the after is the
picture you intended. Record that review on the PR. Baseline maintenance is an
explicit dispatch of CI; this report never rewrites the baseline or adds a release gate.

component	story	theme	mode	pixels
Selector	Indicator Space Bottom Sheet Narrow End RTL	neutral	light	754,077
Selector	Indicator Space Bottom Sheet Wide Start	neutral	light	740,188
Chat	Full AI Chat	probe	light	155,733
Chat	Full AI Chat	probe	dark	155,005
Chat	Default	neutral	dark	33,205
Chat	Default	neutral	light	32,876
Chat	Empty State	probe	light	23,531
Chat	Empty State	probe	dark	22,622
ChatAutoScroll	Scroll Behavior Comparison	neutral	dark	15,378
ChatAutoScroll	Scroll Behavior Comparison	neutral	light	14,107
Chat	With Attachments	probe	light	13,229
Chat	With Attachments	probe	dark	11,065
TableRowExpansion	Detail Panel	neutral	dark	5,129
TableRowExpansion	Detail Panel	neutral	light	4,050
SideNav	Resizable in AppShell	probe	light	3,208
TableGroupedRows	Default	neutral	light	2,133
TableGroupedRows	Default	neutral	dark	2,116
Markdown	Default	probe	dark	897
Markdown	Default	probe	light	897
Markdown	Default	neutral	dark	882

and 3 more.

---

_{Generated by PR Enrichment workflow | View full report}

[astracat-bot]

Approval is waiting on a maintainer spec decision, not on changes from you. The fix looks correct and is well covered by its new tests. No current Astryx spec covers TabList or TabMenu keyboard behavior, so a maintainer needs to provide or identify the spec claim that keys pressed inside a nested popup, such as an open TabMenu, belong to that popup, with Left/Right on a menu option keeping focus there. No code changes are requested right now; thanks for the clear write-up.

[Automated review]