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fix: repaint Codex sessions after pane reattachment - #18283
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Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 8 remain after this review. 📝 WalkthroughWalkthroughThe host view reports reattachment. The renderer uses that callback to reset visible-paint state and retry a flush. The coordinator tracks asynchronous flushes by generation to ignore completions from an earlier state. ChangesSession reattachment
Priority: ➖ Normal Estimated code review effort: 3 (Moderate) | ~20 minutes Change: Bug fix · Severity of issue fixed: Medium Sequence Diagram(s)sequenceDiagram
participant AgentSessionWebHostView
participant AgentSessionWebRenderer
participant AgentSessionWebRendererCoordinator
AgentSessionWebHostView->>AgentSessionWebRenderer: invokes installed onDidReattach callback
AgentSessionWebRenderer->>AgentSessionWebRendererCoordinator: calls invalidateVisiblePaintAfterReattachment()
AgentSessionWebRendererCoordinator->>AgentSessionWebRendererCoordinator: resets paint state and retries flush if ready
Suggested reviewers: Merge Risk: ⚪ Minimal · up to Codex sessions moved between panes now reset their paint state and repaint once they are in the new host. The concern that paint could be marked complete before the new pane takes over was checked and does not hold. No blocking risk remains. 🚥 Pre-merge checks | ✅ 23 | ❌ 2❌ Failed checks (2 warnings)
✅ Passed checks (23 passed)
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Inline comments:
Review comments at @cmuxTests/AgentSessionWebRendererTests.swift:
- Around line 14-33: Update
testRetainedWebViewHostReportsReattachmentAfterPaneMove to exercise the
renderer-installed callback from AgentSessionWebRenderer.updateNSView instead of
only counting onDidReattach calls. Assert that reattachment resets
hasCompletedVisiblePaintFlush and requests a new visible-paint flush after the
pane move.
Review comments at @Sources/Panels/AgentSessionWebHostView.swift:
- Line 175: Track host changes in the retained coordinator across dismantle and
recreation, and invalidate the paint gate when the coordinator binds to a new
host so flushVisiblePaintIfReady() performs a new paint flush. Add a
dismantle-and-recreate test that verifies the moved session receives that flush.
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Sources/Panels/AgentSessionWebHostView.swiftSources/Panels/AgentSessionWebRenderer.swiftSources/Panels/AgentSessionWebRendererCoordinator.swiftcmuxTests/AgentSessionWebRendererTests.swift
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Review follow-up: all four review threads are resolved. The final head is ddba2da, and both focused AgentSessionWebRenderer lifecycle tests pass in run 37593703289. The remaining broad-suite failures were unrelated TerminalWindowPortalLifecycleTests failures. |
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Oct 7, 2026
d5bec00 fix: repaint Codex sessions after pane reattachment (manaflow-ai#18283) df3e34c fix(cloud): resolve 0.65.0 dogfood papercuts (manaflow-ai#18292) 7a5ff86 fix(cloud): restore from a snapshot with a stopped daemon supervisor (manaflow-ai#18320) bf0d292 Fix crash when a focused SwiftUI view outlives its hosting view (manaflow-ai#18250) 6b02ff8 feat(gh-merge-green): --revert rolls back a merged PR in one command (manaflow-ai#18312) 3cab11d Never point a non-production Cloud machine's edge at production coderouter (manaflow-ai#18313) 5df12be fix: let Claude Teams launch with integration disabled (manaflow-ai#18276) # Conflicts: # .github/workflows/ci-guards.yml
3 of 6 tasks
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Summary
Dragging two Codex sessions between panes can leave a retained session surface blank until another interaction causes WebKit to redraw it. Fixes #18270.
The surface and Codex runtime were retained; the failure was at the rendering lifecycle boundary. Bonsplit can reattach the existing
AgentSessionWebHostViewor itsWKWebViewafter the one-time visible-paint flush has completed. The host now reports that reattachment, the coordinator reopens the paint gate and requests a layout/paint flush, and stale asynchronous completions cannot close the gate for a newer attachment. Duplicate callbacks are coalesced while a flush is in flight.Testing
AgentSessionWebRendererTests.testRetainedWebViewHostReportsReattachmentAfterPaneMoveandtestRetainedCoordinatorReopensPaintGateForNewHost, covering pane reattachment and dismantle/recreate host transitions.python3 scripts/verify-local.py— passed all 5 selected checks (Swift syntax, localization defaults, app-source wiring, test wiring, feature-flag policy).python3 scripts/verify-local.py --only swift-syntax --swift-changed origin/main— passed../scripts/sync-test-wiring --check— passed.ObjectIdentifierreuse from suppressing repaint.TerminalWindowPortalLifecycleTests; the focusedAgentSessionWebRendererTestssuite passed.ddba2dabef33ebd00798b66ea28d8140906da07din run 37593703289.xcodebuildapp-host execution; the exact-SHA CI run above provides the executed test evidence.Changelog
Fixed: Dragging Codex sessions between panes redraws retained surfaces after reattachment
Proof
The regression is lifecycle-based and does not have a useful static screenshot; both focused app-host tests passed on final head
ddba2dabef33ebd00798b66ea28d8140906da07din exact-SHA CI run 37593703289.Checklist
cmux ssh: not applicableNote
Medium Risk
Touches WebKit view lifecycle and retained-session rendering in split-pane moves; scoped to paint invalidation with generation guards and new tests, but pane-drag behavior is user-visible.
Overview
Fixes blank Codex/agent session panes after dragging a retained session between split panes: WebKit had already completed its one-time visible-paint flush while detached, so reattachment did not trigger a redraw.
AgentSessionWebHostViewnow exposesonDidReattachwhen the host is added to a new superview (after the first attach) or when a retainedWKWebViewis moved from another host.AgentSessionWebRendererregisters the coordinator on the host and routes reattach toinvalidateVisiblePaintAfterReattachment().AgentSessionWebRendererCoordinatortracks the current host, resets visible-paint state (generation counter, in-flight guard) on workspace/renderer changes and reattach, and re-runs the layout/paint flush so WebKit commits the first layer once the view is visible again—stale async flush completions cannot mark the gate complete for a newer attachment.Adds two lifecycle tests for host reattachment signaling and coordinator paint-gate reopening.
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