cmux-next: open a chat in a new window from its menu

[teamleaderleo]

Summary

The agent chat's "..." menu gets Open in new window, as in the Codex desktop app. It sits after Move to new workspace.

• The row runs the app's existing tab.moveToNewWindow on the chat's tab, the same action as the tab's own context menu. It joins the header's allowed actions (AgentPaneModel.headerActions).
• The keycap comes from the action catalog when the user binds one. No key is added.
• Quick Chat keeps its own Open in window. Its panel is not a tab, so its menu has no tab rows.
• String: chatMenu.newWindow in all 21 locales.

Inventory: manaflow-ai/cmuxterm-hq#1417 (item 3 of the follow-ups).

Testing

• The red commit (302efde) adds theMenuOpensTheChatInANewWindow in AgentPaneHeaderActionTests and a HEADER_ACTIONS.newWindow case in ChatHeaderTools.test.tsx. Recorded locally with bun test src/agent-session/acpmux/header/ChatHeaderTools.test.tsx: at the red commit 302efde, 6 pass and 1 fail (the menu opens the chat in a new window through the app's own action); at 3ff94f5, 7 pass and 0 fail.
• The agent pane bundle and generated/strings.json are regenerated.
• The Swift and web suites run on CI and the fleet; the local checkout has no web dependencies.
• 3ff94f5 rebuilds the pane catalog as the merge base's text plus this branch's keys; the base merge had rewritten its layout (792 lines). The strings are unchanged.
• Visible change: the agent chat's "..." menu has an Open in new window row after Move to new workspace.

Changelog

• Added: Open a chat in a new window from its "..." menu.

🤖 Generated with Claude Code

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Summary by cubic

Brings default-browser sign-in (ASWebAuthenticationSession) to cmux-next, adds Open in new window to the agent chat's "..." menu, and renders Codex accounts with the ChatGPT brand mark in both themes.

Default-browser sign-in
When cmux is the default browser, macOS routes every sign-in another app starts through a new session broker into a dedicated popup panel with a Chromium tab; ephemeral sessions use off-the-record profiles. The CEF shim cancels matching callback navigations before they load (cmux_shim_set_auth_callback / CMUX_SHIM_AUTH_CALLBACK), so OAuth codes never reach the network or another app, and the system's matcher confirms the callback. The capability key stays out of Info.plist until macOS delivers requests reliably, leaving the handler inert in current builds.

Agent chat and accounts
The "..." menu gains Open in new window, running the existing tab.moveToNewWindow (registered in header actions and shortcuts) with the string in all 21 locales; Quick Chat keeps its own Open in window. Codex rows show the ChatGPT brand mark with theme-aware colorScheme.

^{Written for commit 3ff94f5. Summary will update on new commits.}

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Note

High Risk
New OAuth/sign-in interception in the CEF shim and session broker affects authentication callbacks and navigation policy; incorrect matching could break third-party logins or leak callback URLs.

Overview
Adds default-browser sign-in handling so other apps’ ASWebAuthenticationSession flows open in cmux-owned panels, complete on the callback URL, and cancel when the tab closes. A new Swift stack (WebAuthSessionHandler, broker, ephemeral off-the-record profiles) wires into the CEF shim via cmux_shim_set_auth_callback and a new CMUX_SHIM_AUTH_CALLBACK event that cancels main-frame navigations to the session callback before they load (matching custom schemes or https host/path in shared auth_callback_policy.h). CI gains test-auth-callback-policy-cpp.sh; broker and callback behavior are covered by new tests.

Agent chat “…” menu gets Open in new window (tab.moveToNewWindow), registered in AgentPaneModel.headerActions, shortcuts, acpmux header menu, and chatMenu.newWindow across locales.

Accounts UI: Codex rows use the ChatGPT brand mark with palette-driven color scheme; AccountsPalette exposes isDark.

^{Reviewed by Cursor Bugbot for commit 3ff94f5. Bugbot is set up for automated code reviews on this repo. Configure here.}

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[github-actions]

Unclear: web / react-apps-check failed: no known signature; failed step: Check webviews (Oxlint, Oxfmt, type check).

CI failed on 3ff94f51cc (run 37849152094 attempt 1): 1 unknown.
macOS jobs did not run: compile and app tests were skipped: Fast static checks skipped.

Job	Verdict	Why
web / react-apps-check	unknown	no known signature; failed step: Check webviews (Oxlint, Oxfmt, type check)

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.

[teamleaderleo]

Batch queue: green. Batch stack b034a977a4d8 on feat-cmux-next d4056375d08d with #17537 #17597 #17599 #17602 #17604 #17609 #17611 #17613. Fleet production build: job 24360b4ae2a093d871aa1591 (cmux-ci artifact 24360b4ae2a093d871aa1591 (job 24360b4ae2a093d871aa1591, tag nb-local-20261006-180248-1)). heavy tier did not run on this branch (run); your PR's own checks are the tests. Validated this PR at de29bdeb7c2d.

Next: land it yourself with gh-merge-green on this receipt.

[teamleaderleo]

Batch queue: green. Batch stack ed71230a0e11 on feat-cmux-next ff267c4b41d1 with #17541 #17611 #17624 #17625. Fleet production build: job 362a7927afa7714ace3f1b33 (cmux-ci artifact 362a7927afa7714ace3f1b33 (job 362a7927afa7714ace3f1b33, tag nb-local-20261006-190840-1)). heavy tier did not run on this branch (run); your PR's own checks are the tests. Validated this PR at 2a0aa075695c.

Next: land it yourself with gh-merge-green on this receipt.

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[teamleaderleo]

Reviewed the menu, allowed action, shortcut projection and Quick Chat exclusion. Open in new window uses the existing tab.moveToNewWindow action. No concrete correctness findings.

Merged feat-cmux-next through 36f2e07; head 3e60c34b621. This update only brings in base changes, with no conflict resolutions or changes to this PR’s behavior. The published fleet captures were inspected; they cover the earlier implementation, not this exact head. No new capture was taken for this base sync. Exact-head CI is running.

[teamleaderleo]

Batch queue: green. Batch stack 05ed5a19dcf3 on feat-cmux-next 8096756a8d2c with #17609 #17611. Fleet production build: job cc4f4533d25cc5fc04a39a6f (cmux-ci artifact cc4f4533d25cc5fc04a39a6f (job cc4f4533d25cc5fc04a39a6f, tag nb-local-20261006-234630-1)). heavy tier did not run on this branch (run); your PR's own checks are the tests. Validated this PR at 23f3d597f422.

Next: land it yourself with gh-merge-green on this receipt.

[blacksmith-sh]

Found 1 test failure on Blacksmith runners:

Failure

Test	View Logs
test_every_routed_input_triggers_the_workflow (main.PullRequestTiers.test_every_rou ted_input_triggers_the_workflow) (path='Resources/bin/x')	View Logs

^{Need help on this PR? Tag @codesmith-bot with what you need.}

[teamleaderleo]

Updated to 1f52b172f188201b05b0a45e6551e966f9a0c114 with one base merge. Removed generated bundle files and regenerated strings. The touched header web test file passed all 7 tests; fleet AgentPaneHeaderActionTests passed all 4 (job 485a901753ed45a0a184ce8a). Independent review found no correctness defect; the one added string covers all 21 locales. Before/after capture and failing-before native evidence remain missing. Hosted CI is red; this is scoped verification only.

[teamleaderleo]

Parked pending before/after capture proof.

[teamleaderleo]

Capture is no longer a merge gate. The behavior proof is the red-to-green test pair already recorded in the body: 302efdeda9f has 6 web tests passing and the new menu behavior failing, while 3ff94f51cc5 has all 7 passing; fleet AgentPaneHeaderActionTests also passes 4/4 (job 485a901753ed45a0a184ce8a). The visible native change is documented in the body: the agent chat ... menu adds Open in new window after Move to new workspace. The capture-only park is cleared.