fix(web): prevent selection paste when middle-click closing panel tabs

[extoci]

Problem

On Linux, middle-clicking a right panel tab to close it can also paste the primary selection into the focused composer. The tab cancels middle-button mousedown and auxclick, but Chromium pastes on mouseup before auxclick runs.

Fixes #15939.

Change

Reuse the existing middle-button default guard for both mousedown and mouseup, with a name that covers both events. Keep closing in auxclick. This applies to every shared web/Electron right panel tab, including main's draggable tabs. Left and right clicks, activation, close controls, and drag handlers remain unchanged.

Scope and approval

This is a small fix for an unintended paste during the existing middle-click-close action. It qualifies for the focused obvious-bug exception. It changes one file and does not add a broader middle-click policy or address the separate timeline issue #15531.

Verification

Focused checks on the rebased branch passed:

• corepack pnpm exec vp test run apps/web/src/components/RightPanelTabs.test.tsx apps/web/src/components/RightPanelTabs.keyboard.test.tsx apps/web/src/rightPanelStore.test.ts, 3 files and 112 tests passed.
• corepack pnpm --filter @t3tools/web typecheck
• corepack pnpm exec vp lint apps/web/src/components/RightPanelTabs.tsx, exit 0 with an existing warning in the untouched effect at line 443.
• corepack pnpm exec vp fmt --check apps/web/src/components/RightPanelTabs.tsx
• git diff --check

The existing tests cover tab logic and keyboard interactions; they do not prove native primary-selection behavior. Browser use and clipboard access were not authorized, so no Linux native clipboard reproduction or before/after recording is included. The code cancels mouseup at the same event stage as the existing terminal primary-selection guard.

Model: GPT-6.1 Sol, high reasoning effort. Harness: Codex through T3 Code.

[macroscopeapp]

Approvability

Verdict: Approved at 9769af6

Macroscope's review found this PR approvable — This is a narrowly scoped one-file fix that prevents middle-button mouseup defaults on existing panel tabs, addressing Linux primary-selection paste while preserving tab closing and other click behavior. It introduces no schema, security, deployment, default-setting, or static-analysis changes.

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

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 50647de and 9769af6.

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📒 Files selected for processing (1)

• apps/web/src/components/RightPanelTabs.tsx

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📝 Walkthrough

Walkthrough

Right panel tabs now prevent the browser’s default middle-button action on both mousedown and mouseup. The mouseup prevention occurs before auxclick.

Changes

Right panel tab middle-click

Layer / File(s)	Summary
Prevent default middle-button actions apps/web/src/components/RightPanelTabs.tsx	The middle-button handler was renamed and now prevents the default action on both mousedown and mouseup.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Low

Suggested reviewers: juliusmarminge

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Merge Risk: ⚪ Minimal · up to 9769a

The change targets unwanted Linux middle-click paste while retaining the tab-close handler. No concrete merge-blocking issue is established.

Pre-merge checks | 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check		The title is concise, specific, and accurately summarizes the primary fix for Linux selection paste during middle-click tab closure.
Description check		The description covers the problem, change, scope rationale, verification results, and known testing limitations. It does not include the template-requested before/after UI evidence, but the omission …
Linked Issues check		Issue [#15939] requires middle-click tab closure without primary-selection paste into a focused composer on Linux. The PR summary states that preventTabMiddleClickDefault now prevents the middle-but…
Out of Scope Changes check		The reported change is limited to apps/web/src/components/RightPanelTabs.tsx with four additions and two removals. It renames the existing middle-click guard and applies it to mouseup in addition …

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create a new PR

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• Autofix · Keep fixing CodeRabbit findings and required CI, and resolving merge conflicts

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[juliusmarminge]

Note

This comment is posted by Julius' dot

Closing because the changed middle-click interaction has no before/after recording, and the PR explicitly says its tests do not verify native primary-selection paste. The verification requirement calls for evidence of that behavior. Add a short Linux recording showing the unintended paste before the fix and a tab closing without pasting after it, then request reconsideration.