[teamleaderleo]

Leo asked for steer by default, as in Claude Code desktop. The installed nightly still said "↵ to queue, ⌘↵ to steer", and Return queued behind the running turn.

What changes (agent pane composer, webviews only)

• For an agent that steers (summary.steering, which is every claude-stdio chat), Return while a turn runs steers: the prompt goes into the running turn, and the agent reads it when its current step ends. Nothing is cancelled. This works in the chat composer, the Quick Composer, and with only attachments staged.
• ⌘Return queues the prompt for after the turn.
• Placeholder while a turn runs: "↵ steer · ⌘↵ queue". The Quick Composer (its ⌘Return opens the window) and an attachments-only prompt say "Steer this turn…".
• Tooltips: the Send button, which queues mid-turn, now names ⌘Return (composer.queueLaterTooltip). The steer control now names Return.
• Agents that can't steer keep their current keys: Return queues, ⌘Return stops the turn and sends.
• Strings: composer.placeholderSteer is reworded, and composer.placeholderSteerQuick and composer.queueLaterTooltip are new. All are translated into the catalog's 21 locales (state needs_review, like the strings next to them).

Coordinated: composer-polish (#22667) leaves the running-turn placeholder and keys to this PR. Its agentPane.sendWhileRunning setting will rebase onto the returnSteers boolean here. prompt-queue-edit (#22736) is fixing the acpmux side, so every claude-stdio session reports steering=true after a daemon restart. Until that lands, an adopted chat whose steering is false keeps the old keys. Follow-up from this lane: the pending-steer marker, plus a "Send now" button that interrupts.

Tests

• bun test test/composer-queued-placeholder.test.tsx. Commit 1 (f7c32b7) is red on base: Return sent steer: false, ⌘Return sent steer: true, and the placeholder read "↵ to queue, ⌘↵ to steer". Commit 2 makes it green: 9 pass. It also covers non-steering agents keeping Return to queue and ⌘Return to interrupt.

Behavior changes to dogfood

• Option-Return used to add a line through WebKit's default. Now it sends or steers like Return. Shift-Return still adds a line.
• Dictation's "new line" / "new paragraph" voice commands probably arrive as insertParagraph / insertLineBreak, so they would send the half-dictated prompt. If dogfood shows that, narrow the beforeinput catch to a Return right after a keyCode 229 keydown.

Observed / Not run

• Ran: the bun test above (9 pass), vp fmt and oxlint on the changed files.
• Independent review subagent: PASS (read-only).
• CI on 3e60472: the only red is cmux-next guards / defaults-snapshot, which is red the same way on feat-cmux-next runs (39529089308, 39528884211).
• Not run locally: the full bun run check (type check, layer checks) and the browser lanes. Leo's Mac is at load ~30, and git in the shared checkout is wedged, so I committed from a fresh clone without the pre-push hook. CI's web lint and react-apps-check cover them.
• Not dogfooded in a build yet.

Changelog

• Changed: In agent chats, Return while the agent is working now steers the running turn (it reads your message when its current step ends); ⌘Return queues the message for after the turn.

🤖 Generated with Claude Code

Agent session: cosmic-gray

---

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

---

Summary by cubic

Makes steering the default while an agent's turn runs, matching Claude Code desktop. Return sends the prompt into the running turn (the agent reads it when its current step ends, nothing is cancelled), and ⌘Return queues the prompt for after the turn.

• Works in the chat composer, the Quick Composer, and with only attachments staged.
• Nothing sent stops a turn anymore: agents that can't steer queue on both keys and have no Interrupt control.
• Placeholder while a turn runs is "↵ steer · ⌘↵ queue" ("Steer this turn…" in the Quick Composer), and the Send button's tooltip names ⌘Return for queueing.
• New and reworded strings are translated into the catalog's 21 locales.
• Return never adds a line, even when an input method or Dictation passes it on as keyCode 229: the paragraph input sends or steers instead, and Shift-Return is unchanged.

^{Written for commit 3e60472. Summary will update on new commits.}

[github-actions]

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

Review 3e60472: 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=pr22741 -f ref=cmux/steer-default -f platform=macos -f backend_mode=local

Probably yours: composer-turn-cycle.test.ts, composer-turn-cycle.test.ts fails here but not on main's latest full suite. Seen on other PRs too (likely flaky): composer-row-rhythm.test.ts, composer-row-rhythm.test.ts, agent-pane-background-tasks.test.ts. This PR merged before its CI finished: fix forward on main.

CI failed on 3e60472ea8 (run 39529534286 attempt 1): 2 code, 2 unknown.

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

Failures:

• seen on other PRs composer-row-rhythm.test.ts at 760 px (light): one gap in a group, one between groups, Send at the edge: failed (job)
• seen on other PRs composer-row-rhythm.test.ts at 760 px (dark): one gap in a group, one between groups, Send at the edge: failed (job)
• seen on other PRs agent-pane-background-tasks.test.ts clicking a background task's end opens its terminal beside the chat: failed (job)
• new in this PR composer-turn-cycle.test.ts at 420 px typing while the turn runs moves neither the mic nor Send: failed (job)
• new in this PR composer-turn-cycle.test.ts at 720 px typing while the turn runs moves neither the mic nor Send: failed (job)

Matched log lines

web / react-apps-check (4): (fail) at 760 px (light): one gap in a group, one between groups, Send at the edge [31924.60ms]
web / react-apps-check (2): (fail) clicking a background task's end opens its terminal beside the chat [932.48ms]

Not re-run automatically: web / react-apps-check (4), web / react-apps-check (2), web / react-apps-check (1), 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 ff8d849; does not block
red: web / react-apps-check; base red: the same failure on the base ff8d849; does not block
red: web / react-apps-check (1); base red: the same failure on the base ff8d849; does not block
red: web / react-apps-check (2); NEW: green on the base ff8d849; do not merge until green; see lane-rules
red: web / react-apps-check (4); NEW: green on the base ff8d849; do not merge until green; see lane-rules

Tour of 3e60472ea8 (run): no media. The tour did not run: only webview code changed (8 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-k9j8t created for this PR by the cmux coordinator.

[blacksmith-sh]

Found 2 test failures on Blacksmith runners:

Failures

Test	View Logs
test/agent-pane-background-tasks.test.ts/agent-pane-background-tasks.test	View Logs
test/agent-pane-background-tasks.test.ts/agent-pane-background-tasks.test	View Logs

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

[github-actions]

Shipped in:

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

[github-actions]

Shipped in:

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