[teamleaderleo]

Agent-to-agent work in acpmux is now visible in the agent pane, and a lane's acpmux send report draws as a message from that lane, not as the person's prompt.

What changes

• Who sent a prompt. When a connection proves it runs inside an acpmux session (the caller token acpmux puts in that session's env) and prompts a different session without a provenance of its own, the daemon records {kind: "session_message", from, fromName, to} on the user_message and on its queued record. The pane draws it as "Received message from ›", and the name opens that chat. The person's connections, prompts to the sender's own session, the acpmux TUI and a shell's acpmux send stay the person's. A provenance the sender gives is still checked and kept as before. This is the daemon-side fix the cmux-next agent pane: received agent messages are one "Received message from" line; nothing auto-folds #22761 review asked for in place of a client-name guess.
• Sub-session messages. A parent's send_message waits behind the child's running turn by default (deliver: after_turn). next_step is opt-in and delivers into the running turn when the child's agent can take a message mid-turn. The reply says which happened, with the queue's length.
• What a child waits on. get_session and the summary say what a sub-session waits on the person for (a question or a permission), plus its plan step and latest tool.
• Where the user sees the child. start_session's reply says the child is listed under the parent chat.
• The child's chat names its sender (parent, sub-session, ancestor or descendant), with the sender's short name.
• Transcript and summary. Sub-session tool calls draw as cards (started, sent, waiting, reply). The summary lists sub-sessions after subagents, and a row opens the child's chat.

Tests

• Failing first: cmux-tui/crates/acpmux/tests/subsessions_delivery.rs (e02cbe7, a parent's message waits behind a working child's turn) and tests/hub_integration/prompt_provenance.rs a_prompt_sent_from_inside_another_session_records_that_session_as_its_sender (bf479a0). Both are expected to fail on base and pass on the head.
• Webview: incomingMessage.test.ts, subsessionCalls.test.ts, subagents/subsessions.test.ts.

Observed / Not run

• Observed locally: scripts/web-lint.sh passed, prepush-gate.py found no new violations, and cargo fmt is clean.
• Not run: the Rust tests and the webview tests. Agents don't compile or run tests on Leo's Mac, so CI and the fleet are the first runs. The red-on-base and green-on-head results for the two failing-first tests come from CI.
• Not done: the Swift side (an open-tab action for a child chat, sidebar nesting). The Swift app also doesn't read session_message yet, so its own transcript still shows such a prompt as the person's.

No capture: the visible change is the agent pane's webview (sub-session cards, "Received message from …", the summary's sub-session rows), which the gallery advisory run captures; the only native path is build-agent-pane-web.sh adding the cards' stylesheet to the pane bundle.

Changelog

• Changed: Messages that agents send each other (sub-session messages and acpmux send from inside a session) show as "Received message from …" from the sending chat. Sub-sessions show as cards in the transcript and in the summary.

Agent session: cosmic-gray

🤖 Generated with Claude Code

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

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Summary by cubic

Acpmux now shows agent-to-agent messages with their sender in the agent pane, and sub-sessions appear in the transcript and summary instead of reading as the person's own prompts.

• A prompt sent from inside another session with no provenance of its own is recorded as session_message and drawn as "Received message from "; sub-session family messages draw as coming from the sending chat, and the pair guard counts these.
• send_message queues behind the target's running turn by default (deliver: after_turn); deliver: next_step is opt-in, and a child's next_step to its parent waits for the turn to end since a steer can cancel the parent's tool call. The reply says which happened and the queue length.
• Running turns expose their current activity (latest tool title, plan step), and session summaries, session rows and get_session report what a sub-session waits on the person for (question or permission); an ancestor may answer a question when the person enables that. These fields are masked for peers and in rows handed to a parent's agent and stay optional in the protocol spec, as schemars emits them; session rows carry the summary's whole field set, watching included.
• Sub-session tool calls draw as cards in the transcript, including a running call in a live turn as its own card so the working line never names it, and a settled run holding a sub-session card stays unfolded. The summary lists sub-sessions under subagents; names open the child's chat.

Not included: Swift-side support (open-tab action, sidebar nesting); the Swift app still shows session_message prompts as the person's.

^{Written for commit 610e3f8. Summary will update on new commits.}

[teamleaderleo]

Bead cx-3ynan created for this PR by the cmux coordinator.

[github-actions]

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

Review 610e3f8: 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=pr22827 -f ref=cmux/subsession-visibility -f platform=macos -f backend_mode=local

Gallery before/after for 610e3f8: 16 states rendered, 5 images differ, 1435 more touched states not rendered. Images are in the run's artifact, not on this public PR.

gh run download 39621210572 -R manaflow-ai/cmux -n gallery-advisory-22827-610e3f8721e1a66ce3729d0fdb7d1905ff666ab9 (then read gallery-review.json)

States

State	Theme	Status	Diff	Picked by
agent-pane.chat-width/standard	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.chat-width/standard	Apple System Colors	unchanged	0%	own App.tsx
agent-pane.chat-width/wide	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.chat-width/wide	Apple System Colors	unchanged	0%	own App.tsx
agent-pane.chat-width/wide-blocks	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.chat-width/wide-blocks	Apple System Colors	unchanged	0%	own App.tsx
agent-pane.composer-floats/scrolled-to-end	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.composer-floats/scrolled-to-end	Apple System Colors	unchanged	0%	own App.tsx
agent-pane.composer-floats/composer-grown	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.composer-floats/composer-grown	Apple System Colors	unchanged	0%	own App.tsx
agent-pane.docked-chat/new-chat	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.docked-chat/new-chat	Apple System Colors	unchanged	0%	own App.tsx
agent-pane.docked-chat/after-turn	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.docked-chat/after-turn	Apple System Colors	unchanged	0%	own App.tsx
agent-pane.docked-chat/working	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.docked-chat/working	Apple System Colors	unchanged	0%	own App.tsx
agent-pane.docked-chat/typing-in-dock	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.docked-chat/typing-in-dock	Apple System Colors	unchanged	0%	own App.tsx
agent-pane.docked-chat/long-title	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.docked-chat/long-title	Apple System Colors	unchanged	0%	own App.tsx
agent-pane.incoming-message/subsession	Apple System Colors Light	new	0%	own IncomingMessageCard.gallery.ts
agent-pane.incoming-message/subsession	Apple System Colors	new	0%	own IncomingMessageCard.gallery.ts
agent-pane.incoming-message/messages	Apple System Colors Light	unchanged	0%	own IncomingMessageCard.gallery.ts
agent-pane.incoming-message/messages	Apple System Colors	unchanged	0%	own IncomingMessageCard.gallery.ts
agent-pane.incoming-message/opened	Apple System Colors Light	changed	0.0024%	own IncomingMessageCard.gallery.ts
agent-pane.incoming-message/opened	Apple System Colors	changed	0.001%	own IncomingMessageCard.gallery.ts
agent-pane.incoming-message/details	Apple System Colors	changed	0%	own IncomingMessageCard.gallery.ts
agent-pane.incoming-message/details	Apple System Colors Light	unchanged	0%	own IncomingMessageCard.gallery.ts
agent-pane.incoming-message/mid-turn	Apple System Colors Light	unchanged	0%	own IncomingMessageCard.gallery.ts
agent-pane.incoming-message/mid-turn	Apple System Colors	unchanged	0%	own IncomingMessageCard.gallery.ts
agent-pane.incoming-message/reply	Apple System Colors Light	unchanged	0%	own IncomingMessageCard.gallery.ts
agent-pane.incoming-message/reply	Apple System Colors	unchanged	0%	own IncomingMessageCard.gallery.ts

_{Pick other states with a Gallery: entry.id, entry.id/variant line in the PR body.}

Unclear: web / react-apps-check (1) failed: no known signature; failed step: Fail on the gate checks.

CI failed on 610e3f8721 (run 39621210853 attempt 2): 3 unknown.

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

Not re-run automatically: web / react-apps-check (1), 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 9206eac; does not block
red: web / react-apps-check; base red: the same failure on the base 9206eac; does not block
red: web / react-apps-check (1); base red: the same failure on the base 9206eac; does not block
red: web / react-apps-check (2); NEW: green on the base 9206eac; do not merge until green; see lane-rules

CI fast guards failed on 610e3f8721 (https://github.com/manaflow-ai/cmux/actions/runs/39621210853). 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 610e3f8721 (run): no media. The tour job failed before the tour ran (build or setup); the run log has the output.

[cursor]

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[teamleaderleo]

Review (independent subagent, correctness first): SHIP at 97c8f08

Covers the base merges since 814adb4 (App.tsx; #22740's sub-session questions in hub/mod.rs, hub/subsessions.rs, subsession_mcp.rs, with the tool wording now saying only the person allows a permission while a question may be answered with answer_question), the gallery fix for subsession-cards#summary at popover width, and the spec fix: SessionDetail carries every SessionSummary field (incl. base's watching, missing since #21921) and waitingOn's description keeps its line break, as schemars emits them.

[teamleaderleo]

Review (independent subagent, correctness first): SHIP at 1da7852

Base merge only since 97c8f08: App.tsx keeps base's VirtualTranscript block (needsYou) inside the PR's SubsessionContext.Provider; base's sessionList.ts removals leave no callers; catalog in base order; toml equals base.

[teamleaderleo]

Review (independent subagent, correctness first): SHIP at 8f65b51

[teamleaderleo]

Review (independent subagent, correctness first): SHIP at 610e3f8

[teamleaderleo]

Merge check at 610e3f8: the build-script change (scripts/cmux-next/build-agent-pane-web.sh) is covered by cmux-next Release compile (Xcode 26), web bundles and generated drift, all green. swift test was cancelled and generated files is still queued on the Mac pool; the diff has no Swift. Remaining reds are base reds: gallery health (agent-pane.artifact-panel "Open preview" and composer fast-mode waitFor states, the same ones failing on other PRs; this PR adds neither), fast gates, clippy on changed cmux-tui packages, defaults-snapshot. Merges cleanly with current feat-cmux-next. Merging.

[github-actions]

Shipped in:

• cmux NEXT nightly 1.0.0-nightly.3964654862801 (06af62206e)
• cmux NEXT nightly 1.0.0-nightly.3965027402001 (6bc437994c)
• cmux NEXT nightly 1.0.0-nightly.3965153006601 (a10158f013)