[teamleaderleo]

Leo, 2026-11-03: "i also dont like how the session info overlay is when it goes to a right split honestly it's often fine to just not have it open by default on the right like it doesn't need to inherit that..."

Leo, 2026-11-03: "like if they want it open they can just do it on the right split one but otherwise it really doesn't have that much space pretty often"

Follow-up to #32677, which made an opened subagent go to the right split.

What changes

• A chat opened in a split starts with Session Info closed. That covers a subagent's pane, and a chat its agent started (startedBy/spawnedBy, the task and sub-session chips) when it opens beside its parent.
  • Session Info's state for such a pane is kept under a key of its own (sessionInfoPaneKey, split:<session>). With no saved state, that key starts closed instead of taking the parent's state or the last choice made.
  • If the person opens Session Info there, the choice sticks for that pane and never reaches the parent's.
  • A subagent's pane shows its chat's own session. Before this change it read and wrote the chat's own Session Info state, so the parent's open state carried over into the split.
• Review follow-up from agent pane: an opened subagent goes to the right split; no "Back to" names a raw id #32677: the comment above showSubagent in App.tsx no longer says panes open only while the switch is on.

Logic is in shared web only (sessionInfoState.ts, SessionInfo.tsx, App.tsx). The native Session Info layout is untouched.

Tests

test/session-info-split-starts-closed.test.ts:

• A split pane's first frame and its bind read closed while the parent stays open, including after a relaunch.
• A started chat opened beside its parent starts closed.
• Opening Session Info in the split pane sticks there and leaves the parent's state alone.

Observed / Not run

• Observed: bun test on the new test, session-info-per-pane-state and subagent-click-opens-right-split (23 pass); vp fmt/vp lint on the changed files; prepush gate.
• Not run:
  • A native capture of a split chat.
  • The "split" signal for a chat opened beside an unrelated chat (for example, a "Sent to" sender chip opening another root chat). The page has no signal for that case today, and the app does not tell the page that a chat tab was opened as a split. Those panes keep the old default.

Agent session: agent session

🤖 Generated with Claude Code

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^{Open in [code]smith · Need help on this PR? Tag @codesmith-bot with what you need.}

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Summary by cubic

Chats opened in a split — a subagent's pane, or a chat its agent started — now start with Session Info closed instead of inheriting the parent's open state.

• The split pane keeps its own Session Info state under a separate key (split:<session>); opening it there sticks and never reaches the parent's.
• A subagent's pane reads and writes its own state now that it shows its chat's session, instead of the chat's own.
• Fixes a stale comment above showSubagent (follow-up to agent pane: an opened subagent goes to the right split; no "Back to" names a raw id #32677).

Not covered: a chat opened beside an unrelated chat (a "Sent to" sender chip) and a native capture of a split chat; those panes keep the old default.

^{Written for commit 6efe02e. 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 6efe02e: 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=pr32763 -f ref=lane/split-session-info-closed -f platform=macos -f backend_mode=local

Gallery before/after for 6efe02e: 16 states rendered, 10 images differ, 3034 more touched states not rendered. Images are in the run's artifact, not on this public PR; the independent review of this head reads them on its own, so the PR needs no hand-made screenshots of these states.

gh run download 41556457919 -R manaflow-ai/cmux -n gallery-advisory-32763-6efe02e75adeb999d534bd61edf44597498fc23e (then read gallery-review.json)

States

State	Theme	Status	Diff	Picked by
agent-pane.chat-inspector/full	Apple System Colors Light	unchanged	0%	own SessionInfo.tsx
agent-pane.chat-inspector/full	Apple System Colors	unchanged	0%	own SessionInfo.tsx
agent-pane.chat-inspector/workflow-running	Apple System Colors Light	changed	0.0064%	own SessionInfo.tsx
agent-pane.chat-inspector/workflow-running	Apple System Colors	changed	0.0056%	own SessionInfo.tsx
agent-pane.chat-inspector/workflow-finished	Apple System Colors Light	unchanged	0%	own SessionInfo.tsx
agent-pane.chat-inspector/workflow-finished	Apple System Colors	unchanged	0%	own SessionInfo.tsx
agent-pane.chat-inspector/workflow-agent-failed	Apple System Colors Light	unchanged	0%	own SessionInfo.tsx
agent-pane.chat-inspector/workflow-agent-failed	Apple System Colors	unchanged	0%	own SessionInfo.tsx
agent-pane.chat-inspector/workflow-agent-row-compact	Apple System Colors Light	changed	0.0048%	own SessionInfo.tsx
agent-pane.chat-inspector/workflow-agent-row-compact	Apple System Colors	changed	0.0023%	own SessionInfo.tsx
agent-pane.chat-inspector/workflow-agent-row-detail	Apple System Colors Light	changed	0.0067%	own SessionInfo.tsx
agent-pane.chat-inspector/workflow-agent-row-detail	Apple System Colors	changed	0.0055%	own SessionInfo.tsx
agent-pane.chat-inspector/workflow-agent-row-grid	Apple System Colors Light	changed	0.0062%	own SessionInfo.tsx
agent-pane.chat-inspector/workflow-agent-row-grid	Apple System Colors	changed	0.0059%	own SessionInfo.tsx
agent-pane.chat-inspector/workflow-agent-row-narrow	Apple System Colors Light	changed	0.0063%	own SessionInfo.tsx
agent-pane.chat-inspector/workflow-agent-row-narrow	Apple System Colors	changed	0.0056%	own SessionInfo.tsx
agent-pane.chat-inspector-surfaces/transcript	Apple System Colors Light	unchanged	0%	own SessionInfo.tsx
agent-pane.chat-inspector-surfaces/transcript	Apple System Colors	unchanged	0%	own SessionInfo.tsx
agent-pane.chat-inspector-surfaces/diff-in-place	Apple System Colors Light	unchanged	0%	own SessionInfo.tsx
agent-pane.chat-inspector-surfaces/diff-in-place	Apple System Colors	unchanged	0%	own SessionInfo.tsx
agent-pane.chat-inspector-surfaces/document-beside	Apple System Colors Light	unchanged	0%	own SessionInfo.tsx
agent-pane.chat-inspector-surfaces/document-beside	Apple System Colors	unchanged	0%	own SessionInfo.tsx
agent-pane.chat-inspector-surfaces/diff-closed	Apple System Colors Light	unchanged	0%	own SessionInfo.tsx
agent-pane.chat-inspector-surfaces/diff-closed	Apple System Colors	unchanged	0%	own SessionInfo.tsx
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-edge/short-edge	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.composer-edge/short-edge	Apple System Colors	unchanged	0%	own App.tsx

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

Shipped in:

• cmux NEXT nightly 1.0.0-nightly.4156284504201 (8ce390075e)
• cmux NEXT nightly 1.0.0-nightly.4156407433601 (79b76ff1ed)
• cmux NEXT nightly 1.0.0-nightly.4156482801501 (585171513e)
• cmux NEXT nightly 1.0.0-nightly.4156640893901 (06ca249ff1)
• cmux NEXT nightly 1.0.0-nightly.4156722095701 (26b4ff51c7)
• cmux NEXT nightly 1.0.0-nightly.4156852011001 (2f3ccfed7d)

[teamleaderleo]

Review (claude-opus-5-5): SHIP at 6efe02e

Review (subagent claude-opus-5-5): SHIP at 6efe02e
Visual verdict: no images; Session Info closed by default in a split-opened chat, layout untouched.
Checked the pane key match between App.tsx and useSessionInfo, snapshot stability of the closed default, index/prune with split: keys, native Session Info reading the bound state, and gallery plays (none expect Session Info open in a subagent pane or started chat). Tests pass.
Follow-ups: key subagent panes by subagent id instead of one split: key; avoid the first-frame bind to the parent's key before the subagent reveal; keep a split pane's open/close out of the global default for new chats; Chief-spawned chats (spawnedBy) start closed in their main pane too.