Agents Window logs noisy customization errors during disposal

[copilot-swe-agent]

Type of issue

Bug

Description

The Window log is flooded with errors from the Agents Window customization and task-loading paths, apparently during disposal or cancellation. This was observed in VS Code Insiders on September 3, 2026.

Representative messages:

[trace] [Window] [SyncedCustomizationBundler] Failed to stat skill resource file:///Applications/Visual%20Studio%20Code%20-%20Insiders.app/Contents/Resources/app/out/vs/sessions/skills/fix-ci/SKILL.md Object has been disposed: Error: Object has been disposed
    at WI.queue (...)
    at LVe._queueFileOperation (...)
    at async LVe.bundle (...)

This repeats for many built-in skills, including generate-run-commands and update-pr.

There are also repeated missing-file traces while expanding plugin customizations:

[trace] [Window] file not found: EntryNotFound (FileSystemError): file not found
    at Hz.stat (...)
    at Vpe.doResolveFile (...)
    at async X_i.expandPluginContents (...)
    at async vhe.provideChatSessionCustomizations (...)
    at async U9e.getSlashCommands (...)

And a canceled tasks request is logged as an error:

[error] [Network] #17: https://api.githubcopilot.com/agents/tasks?per_page=100&page=1 - error GET Canceled

Expected behavior

Expected cancellation/disposal races and missing optional customization resources should not flood the Window log with stack traces.

Actual behavior

A normal Agents Window session produces many repeated trace entries and a network error, obscuring actionable diagnostics.

Created from a Slack conversation.

[benibenj]

Focused diagnosis for the SyncedCustomizationBundler errors:

2026-09-03 12:59:14.578 [error] Object has been disposed: Error: Object has been disposed
    at WI.queue (...)
    at AVe._queueFileOperation (...)
    at async AVe.bundle (...)

The same failure is also logged once per skill being traversed:

[trace] [SyncedCustomizationBundler] Failed to stat skill resource .../skills/fix-ci/SKILL.md Object has been disposed: Error: Object has been disposed

The cause appears to be a lifecycle race introduced when #333827 added recursive skill-directory traversal through a shared Limiter. AgentCustomizationScope can dispose its SyncedCustomizationBundler while an asynchronous bundle() is still running. Disposal immediately disposes the limiter, but the active traversal continues after an await and tries to queue more file operations. Limiter.queue() then throws Object has been disposed; disposing the limiter can also discard already-queued operations before their promises settle.

A simple fix would be to stop accepting new bundles after disposal, while keeping the file-operation limiter alive until bundles that already started have drained or cancelled cleanly. An active bundle should check for disposal before rewriting the synthetic customization tree and finish with CancellationError during normal shutdown. Bundle writes targeting the same synthetic authority should also be serialized so a stale, disposed scope cannot overwrite a replacement scope.

[vs-code-engineering]

connor4312 is out of office, assigning roblourens as backup.