[austinywang]

Summary

A chat pane opened a new split for every subagent its chat started. Agent work routinely starts several subagents (reviews, searches, dispatch), so the splits piled up to the right of the chat. The summary card's "Open new subagents in panes" switch could turn that off, but agent panes use non-persistent web storage (AgentPaneView.sharedDataStore is WKWebsiteDataStore.nonPersistent()), so the choice was gone after every restart.

This makes the switch off by default (subagents/subagentPanes.ts): new subagents stay in the chat, and the pane opens only once the user turns the switch on (stored as "on"; an old "off" value still reads as off). Clicking a subagent row or a summary card row still opens its pane, as before. The server snapshot uses the same read, so it no longer reports "on".

Making the choice survive restarts (a cmux.json setting) is a separate follow-up. With off as the default, a restart no longer brings the splits back.

Testing

Focused command (from webviews/): bun test test/subagent-panes-default-off.test.ts

• Base (0dba7a6f35f7d, test only): 1 pass, 2 fail. With nothing stored, the hook reported on (Expected: "<span>off</span>", Received: "<span>on</span>").
• Head: 3 pass, 0 fail.

Observed / Not run

• Observed: the focused test above, red on base and green on head. scripts/web-lint.sh passed (webviews).
• Not run: the full webviews suite and the gallery (left to PR CI). No tagged-app dogfood. The gallery's pane-open / card-open-pane cases cover the click path, which this change doesn't touch.

Changelog

• Changed: Subagents no longer open a split each by default. Click one to open it beside the chat, or turn on "Open new subagents in panes" in the chat's summary card.

🤖 Generated with Claude Code

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Summary by cubic

Makes the "Open new subagents in panes" switch off by default, so new subagents stay in the chat instead of opening a split each.

Agent panes use non-persistent storage, so the manual off setting was lost after every restart and the splits came back. The switch now reads as off until the user turns it on (stored as "on"); an old "off" value still reads as off, and clicking a subagent row or summary card row still opens its pane. The server snapshot uses the same read, so it no longer reports "on." The release notes entry gains a "Try it" action to satisfy the highlights validator.

^{Written for commit 733a537. Summary will update on new commits.}

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[github-actions]

cmux status _{(one comment, edited in place; each line is updated by the job that owns it)}

Review 733a537: HQ feed card · gallery before/after runs · checks

App of this head (app.zip, kept 1 day)

gh workflow run reload-build.yml -R manaflow-ai/cmux --ref feat-cmux-next -f tag=pr22615 -f ref=feat-cmux-next-subagent-panes-off -f platform=macos -f backend_mode=local

Unclear: web / react-apps-check failed: no known signature; failed step: Check webview test shards. This PR merged before its CI finished: fix forward on main.

CI failed on 733a53710a (run 39545103014 attempt 1): 4 code, 1 unknown.

Job	Verdict	Why
web / react-apps-check (3)	code	a web test failed
web / react-apps-check (1)	code	a web test failed
web / react-apps-check (4)	code	a web test failed
web / react-apps-check (2)	code	a web test failed
web / react-apps-check	unknown	no known signature; failed step: Check webview test shards

Failures:

• seen on other PRs agent-pane-trust-ask-corner.test.ts the trust bar's corner is the composer card's: failed (job)
• seen on other PRs agent-pane-trust-ask-corner.test.ts no caption stands between the open trust question and the card: failed (job)
• seen on other PRs composer-mention.test.ts @ then letters lists the chat's matching files and Return writes the path: failed (job)
• seen on other PRs composer-mention.test.ts after picking a path markdown escapes, typing on leaves the picker closed: failed (job)
• seen on other PRs composer-mention.test.ts @proje lists other chats, then folders, then the chat folder's files: failed (job)
• seen on other PRs composer-mention.test.ts a chat named for a long prompt does not take @app from the file: failed (job)
• seen on other PRs composer-mention.test.ts a bare @ lists the most recent other chats: failed (job)
• seen on other PRs composer-mention.test.ts an @ inside a word opens nothing and asks the host for nothing: failed (job)
• seen on other PRs agent-pane-soft-edges.test.ts the transcript fades under the header once scrolled, and above the composer while more lies below: failed (job)
• seen on other PRs composer-history.test.ts ↑ and ↓ in an empty prompt step through the chat's earlier prompts: failed (job)
• ... 17 more in the job logs

Matched log lines

web / react-apps-check (3): (fail) the trust bar's corner is the composer card's [6733.27ms]
web / react-apps-check (1): (fail) the transcript fades under the header once scrolled, and above the composer while more lies below [4088.75ms]
web / react-apps-check (4): (fail) queued and steering prompts > the queue takes its own place in the stack: nothing is cut off or drawn over [1286.72ms]
web / react-apps-check (2): (fail) the adopted turn's Worked for opens to its commands and edited files [31120.46ms]

Not re-run automatically: web / react-apps-check (3), web / react-apps-check (1), web / react-apps-check (4), web / react-apps-check (2), web / react-apps-check are not machine failures.

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.

red: web / Web status; base red: the same failure on the base 4a15471; does not block
red: web / react-apps-check; base red: the same failure on the base 4a15471; does not block
red: web / react-apps-check (1); base red: the same failure on the base 4a15471; does not block
red: web / react-apps-check (2); base red: the same failure on the base 4a15471; does not block
red: web / react-apps-check (3); base red: the same failure on the base 4a15471; does not block
red: web / react-apps-check (4); NEW: Expected: <= 552 Received: 577 at <anonymous> (/home/runner/_work/cmux/cmux/webviews/test/agent-pane-queue-steer.test.ts:355:32) is not red on the base 4a15471; do not merge until green; see lane-rules

CI fast guards failed on 39fc93a5c1 (https://github.com/manaflow-ai/cmux/actions/runs/39534166871). 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.

Tour of 733a53710a (run): no media. The tour did not run: only webview code changed (2 path(s)), which the gallery advisory run checks in Linux Chromium on the pull request (its artifact holds any captures); add the media-tour-mac label to tour it on a Mac.

[teamleaderleo]

Bead cx-dwsj5 created for this PR by the cmux coordinator.

[teamleaderleo]

cmux-next guards / defaults-snapshot is red on 17 of 17 fresh feat-cmux-next PR heads in the last 2:00:00, so it is most likely a base red, not this PR's. The base-reds lane has it; a base merge picks up the fix once it lands.

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[austinywang]

Review (head 0d1d4fc8e65a7f9917392ffa7aa361590b734ffb)

A correctness-first review subagent ran at be4130f and passed it (PASS). I checked the diff myself: it's still the same 3 files, and the only change since that review is a fix to the What's New file.

Findings and how each was resolved:

1. Consumers: only App.tsx uses the hooks. Clicking a subagent row or a card row still opens its pane through showSubagent, and that path never checks the switch. No change needed.
2. Gallery and tests: the pane-open and card-open-pane cases start from a click, and nothing depends on auto-open being on by default. No change needed.
3. Server snapshot set to read: no page hydrates, and read catches storage errors. No change needed.
4. Low: the test covers read but not the setter. Left as is; the setter is two lines.
5. Low: the What's New entry failed release-notary, which needs a Try it action. Fixed in 0d1d4fc (action: palette.newAgentChat). scripts/whats-new/test_digest.py now passes locally: 5 tests OK.

Red checks at be4130f

• release-notary: caused by this PR, fixed in 0d1d4fc (above).
• defaults-snapshot: base red. It flags CmuxNextFloating/ChiefPet/ChiefPetPanel.swift, which this PR doesn't touch, and it's red on 17 of 17 recent feat-cmux-next heads (base-red-watch comment above).
• web / react-apps-check (1): base red. The webviews check fails on an Oxlint warning in conversation/UserBubble.tsx:191, which came in with the base merge. All 146 test files passed.
• web / react-apps-check (2): base red. "clicking a background task's end opens its terminal beside the chat" (agent-pane-background-tasks.test.ts) fails the same way on unrelated PRs cmux NEXT composer: Return steers a running turn, ⌘Return queues #22741, Agent pane: a message sent mid-turn never leaves Return and Send dead #22732 and cmux NEXT transcript: no caret at the end of a streaming reply #22730, and it doesn't involve subagent panes.

Not run: the full webviews suite locally (CI ran it) and a tagged-app dogfood.

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[github-actions]

Shipped in:

• cmux NEXT nightly 1.0.0-nightly.3955987471201 (03960f5a64)
• cmux NEXT nightly 1.0.0-nightly.3956132659001 (233cc81754)