[teamleaderleo]

Fixes #29639.

The right-hand session card reads the chat's rows through useHeldWhileScrolling (summary/heldWhileScrolling.ts, #29282), but Session Info scoped to a subagent read snapshot.subagentViews[shown] live, so it could change under the reader's own scroll as history paged in. Those rows now go through the same hold, keyed by chat and subagent: the rows from when the scroll began stay until it settles, then the paged-in rows land once. Another subagent or another chat takes its rows at once.

Only what Session Info lists is held; the header's Background tasks count stays live, as the chat's transcriptWork count already does.

Test: webviews/test/summary-held-while-scrolling.test.tsx adds a case for the subagent key (held mid-scroll, applied on settle, another subagent at once). Fast checks plus bun run check passed on cmux-ci: https://github.com/manaflow-ai/cmux/actions/runs/41332644983

Risk: small, one hook call in App.tsx feeding one prop.

Agent session: agent session

🤖 Generated with Claude Code

---

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Summary by cubic

Fixes #29639. Subagent-scoped Session Info kept reading snapshot.subagentViews live, so history paging in under the reader's scroll changed its rows mid-gesture. It now uses the same held-while-scrolling mechanism as the chat's session card, keyed by chat and subagent: rows from when the scroll began stay until the scroll settles, then the paged-in rows land. Another subagent or chat takes its rows at once. Only the listed rows are held; the header's Background tasks count stays live.

^{Written for commit e901865. 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 e901865: 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=pr31176 -f ref=subagent-session-info-held-scroll -f platform=macos -f backend_mode=local

Gallery before/after for e901865: 16 states rendered, 0 images differ, 1210 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 41333256056 -R manaflow-ai/cmux -n gallery-advisory-31176-e9018653b884ba7f661a68de933429bf41d3270a (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-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
agent-pane.composer-edge/wide-edge	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.composer-edge/wide-edge	Apple System Colors	unchanged	0%	own App.tsx
agent-pane.composer-edge/no-edge	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.composer-edge/no-edge	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.composer-rest-gap/gap-40	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.composer-rest-gap/gap-40	Apple System Colors	unchanged	0%	own App.tsx
agent-pane.composer-rest-gap/gap-56	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.composer-rest-gap/gap-56	Apple System Colors	unchanged	0%	own App.tsx
agent-pane.composer-rest-gap/gap-72	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.composer-rest-gap/gap-72	Apple System Colors	unchanged	0%	own App.tsx
agent-pane.continuation-spacing/shipped	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.continuation-spacing/shipped	Apple System Colors	unchanged	0%	own App.tsx
agent-pane.continuation-spacing/two-thirds	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.continuation-spacing/two-thirds	Apple System Colors	unchanged	0%	own App.tsx
agent-pane.continuation-spacing/half-tucked	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.continuation-spacing/half-tucked	Apple System Colors	unchanged	0%	own App.tsx
agent-pane.continuation-spacing/before	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.continuation-spacing/before	Apple System Colors	unchanged	0%	own App.tsx
agent-pane.copy-controls/output	Apple System Colors Light	unchanged	0%	own App.tsx
agent-pane.copy-controls/output	Apple System Colors	unchanged	0%	own App.tsx

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

red: cmux-next checks (god files, concurrency, crash safety, l10n); base red: the same failure on the base 3545d99; does not block

Shipped in:

• cmux NEXT nightly 1.0.0-nightly.4133598742701 (1e1948befb)
• cmux NEXT nightly 1.0.0-nightly.4133716725501 (d30463325c)
• cmux NEXT nightly 1.0.0-nightly.4133769596201 (0272db645e)
• cmux NEXT nightly 1.0.0-nightly.4133822529301 (68e3df851b)
• cmux NEXT nightly 1.0.0-nightly.4133907849701 (c2ef233b76)
• cmux NEXT nightly 1.0.0-nightly.4133963836301 (48e4448d11)
• cmux NEXT nightly 1.0.0-nightly.4134024448601 (94322a6ccf)

[teamleaderleo]

Review (subagent opus-5.5 medium): SHIP at e901865

Hooks order safe (flat block beside cardRows/cardEdit); key chat+subagent takes a new subagent or chat at once; Session Info's chat rows already come from the held cardSnapshot; memo deps correct.

Follow-ups:

• [follow-up] An App-level check (or mock scene) that subagent-scoped Session Info reads the held rows; the new test drives the hook only.
• [follow-up] The header Background tasks count stays live while the panel is held (same as the chat's transcriptWork); note it in heldWhileScrolling.ts if intended.

[teamleaderleo]

Owned by an agent session · session

[blacksmith-sh]

Found 8 test failures on Blacksmith runners:

Failures

Test	View Logs
/tmp/tmp1wl7bf__/summary-fail.json (live):/summary-fail.json (live):	View Logs
/tmp/tmpideed3f9/summary-missing.json (live):/summary-missing.json (live):	View Logs
[new_workspaces] debug.new_workspace timed 0 of 50 new workspace rows/ [new_workspaces] debug.new_workspace timed 0 of 50 new workspace rows	View Logs
[new_workspaces] the window draws no frames/[new_workspaces] the window draws no frames	View Logs
[tabs] debug.tab_switch timed 0 of 40 switches/ [tabs] debug.tab_switch timed 0 of 40 switches	View Logs
[tabs] the window draws no frames/[tabs] the window draws no frames	View Logs
test_runtime_added_app_capabilities_are_runtime_only (main.StaticCapabilityRuntimeO nlyTests.test_runtime_added_app_capabilities_are_runtime_only)/ test_runtime_added_app_capabilities_are_runtime_only (main.StaticCapabilityRuntimeO nlyTests.test_runtime_added_app_capabilities_are_runtime_only)	View Logs
test_the_repository_highlights_validate (main.DigestTests.test_the_repository_highl ights_validate)/ test_the_repository_highlights_validate (main.DigestTests.test_the_repository_highl ights_validate)	View Logs

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