[lawrencecchen]

Takes back #36133: moves its flicker log from a static to one instance owned by AgentTabStore.wired (the composition root) to fix the arch-ratchet stateful_singletons +2 tip red; the log's behavior and its off-main writes do not change.

Fixes the arch-ratchet tip red on feat-cmux-next after #36133 (culprit 27fa467): [stateful_singletons] +2 (CmuxNextAgentPane +2), from AgentPageFlickerLog.shared and its static var occlusion.

The log is now one instance that the composition root makes and passes in (plans/cmux-next/PATTERNS.md, composition root):

• AgentTabStore.wired(to:) (built once per AppServices) makes it with AgentPageFlickerLog.forAppRun(). That is nil outside an app bundle, as shared was. The store passes it to every pane through AgentPaneShared.flickerLog.
• AgentPaneView keeps it (flickerLog). Its bridge, its navigation delegate and AgentPageTerminations record through the pane's log. A pane with no log (tests) writes nothing.
• The window occlusion watch is now state of the log instance. Each pane asks for it and the first one starts it. It takes its NotificationCenter so a test can post to its own.
• No arch exception, and the recorded margin does not change.

Threading does not change. The caller's turn only builds the JSON line. The file create, append and roll-over run on the log's utility DispatchQueue, never on the main thread. flush() (queue.sync) is called only by tests.

Red on base, green on head

Command: python3 scripts/cmux-next/arch-ratchet.py --base bacb88f2349f --head b1b7a3ff9d02 (the tip range), exit 1:

arch-ratchet: [stateful_singletons] stateful singletons (stored static or file-scope global of a stateful type): +2 (CmuxNextAgentPane +2)
  Packages/macOS/CmuxNext/Sources/CmuxNextAgentPane/AgentPageFlickerLog.swift:35: static let shared: AgentPageFlickerLog? = {
  Packages/macOS/CmuxNext/Sources/CmuxNextAgentPane/AgentPageFlickerLog.swift:141: @MainActor private static var occlusion: MainActorObservation?

arch-ratchet.py --audit --rev e3a11f5de68 (current base): stateful_singletons 201 over the recorded 199.

Head: arch-ratchet.py --base origin/feat-cmux-next --head HEAD gives stateful_singletons -2 (CmuxNextAgentPane -2), no architecture count rises, exit 0. --audit --rev HEAD reports no stateful_singletons rise (199). prepush-gate.py: no new violations.

Regression test: AgentPageFlickerLogTests.everyPaneAsksForTheWindowWatchAndAFlipIsOneLine. Two panes ask for the watch and one occlusion flip writes one line. The test does not compile on base, because the watch was a static on shared, and shared is nil in tests.

Fleet compile: cmux-ci compile-check --app --package CmuxNext --ref c425e04a4f841067068c5e166a7d0b06f87924b8, job 1879bbb659bbbe4fd139e0c2: CmuxNext passed, app passed (also passed at 9640563, job 43da2f7b56759e66e5ca241d)
Fleet test: cmux-ci run --class light --script scripts/ci/package-test-lane.sh --arg suite --arg Packages/macOS/CmuxNext --arg AgentPageFlickerLogTests, ref c425e04, step 9915cf9d004fc8ef48a8ea61 on aws-m4pro-7: 4 tests in AgentPageFlickerLogTests passed, the new test included

Changelog

none

Observed / Not run

• Observed: the arch-ratchet commands above (red on base, green on head); prepush-gate.py; the fleet compile and the fleet test run above.
• Not run: no tagged app build to confirm that the ring file still fills in a real app run. Only the wiring moved: the lines and the file path are the same.
• Out of scope: Agent pane: an always-on flicker log in a small ring file, matched to UTC time #36133 also added one observer_sites site (the occlusion watch). That row is part of older debt that no single commit raised (+15 at the tip), and the arch ratchet does not report it red. This PR keeps the count the same.

[github-actions]

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

Review c425e04: 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=pr36207 -f ref=fix/tip-red-flicker-log -f platform=macos -f backend_mode=local

web and size checks: green

Shipped in:

• cmux NEXT nightly 1.0.0-nightly.4200417289001 (42abbd2b81)
• cmux NEXT nightly 1.0.0-nightly.4201868763201 (5052d6545e)

The feat-cmux-next push run https://github.com/manaflow-ai/cmux/actions/runs/41992440601 at c293fc3 failed: cmux-next crash ends the app.
Those jobs last passed at 3deee62. This pull request is one of 3 merged since: #36285, #36207, #36251.
If the failure is in your change, fix forward on feat-cmux-next. Pull requests run only the tiers their paths reach (docs/ci/cmux-next-tiers.md); label a batch PR full-ci to run them all before merging.

[lawrencecchen]

Review (claude-review-subagent): SHIP at c425e04

Independent correctness review of the exact head. The first pass at 9640563 found one HOLD issue: the new test's NSWindow was closed with close() while isReleasedWhenClosed was still true, so AppKit could over-release it. c425e04 fixes this with closeAfterTest(). No findings remain.

• Recording sites: the bridge (diag.flicker), the navigation commit, web-content-ended (AgentPageTerminations) and the window occlusion watch all go through view.flickerLog. The app makes its only pane through AgentTabStore.wired (AppServices.agentTabs, lazy, one per app), so it makes one log for each run. forAppRun() is nil outside an app bundle, so tests and tools write nothing.
• Lifetime: the watch starts once per log, and the observation captures [weak self], so there is no retain cycle.
• Swift 6: the class is @MainActor, so it is implicitly Sendable. The members that tests and the queue touch are nonisolated and Sendable. The queue.async closure captures only [Data], URL and nonisolated statics. public is set where CmuxNextApp needs it.
• Threading: the caller's turn only builds the line. Create, append and roll-over stay on the utility queue. Only tests call flush().
• Composition root (PATTERNS P1): the store that AppServices makes builds the log once and passes it in through init. The PR adds no arch exception. arch-ratchet gives stateful_singletons -2, with no rises.
• Evidence at this head: fleet compile job 1879bbb659bbbe4fd139e0c2 passed. Fleet test step 9915cf9d004fc8ef48a8ea61 passed AgentPageFlickerLogTests (4 tests).

[lawrencecchen]

Classification of the non-green checks on this head:

• cmux-next checks (god files, concurrency, crash safety, l10n): base finding. It fails on check-no-process-scan (CmuxCuaHelperCore/TakeoverBench.swift:55, acpmux/src/cpu_class.rs:322) and on check-switch-fetches.test.sh. This PR touches none of these files, and unrelated Cloud relay chat: argument promptId, so cloud start-chat's --prompt-id reaches it #36193 fails the same way. The check-crash-safety step in the same job passes.
• cmux-next no new generated files (base red: crash-ratchet after #36165 #36206 only): flake. tests/test_generated_files_guard.py tearDown gave OSError: [Errno 39] Directory not empty: 'objects'. The same job is green on base red: arch-ratchet after #36133 #36207.
• nightly-guards / release-notary (base red: arch-ratchet after #36133 #36207 only): this PR touches no workflow or release file, so it is not this PR's red.

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