SCM: "Open Changes" hangs while a commit message is being generated with Copilot

[tamuratak]

Version: 1.134.0-insider (Universal)
Commit: 72f433c
Date: 2026-08-13T04:55:17Z
Electron: 42.8.1
ElectronBuildId: 14906494
Chromium: 148.0.7778.280
Node.js: 24.18.1
V8: 14.8.178.38-electron.0
@github/copilot: 1.0.79
@github/copilot-sdk: 1.0.10-preview.0
OS: 72f433c

Summary

When a commit message is being generated with Copilot from the SCM input box, clicking Open Changes does not open the multi-file diff editor. It stays loading until the generation finishes (several seconds), so it looks blocked/frozen.

Notice that the generation of the message can take longer when setting a reasoning model as a BYOK utility small model.

Steps to Reproduce

1. Stage some changes in a git repository.
2. Trigger commit message generation from the SCM input box (Copilot).
3. Immediately click Open Changes.
4. The multi-file diff editor does not open (spinner only) until generation completes.

Expected Behavior

"Open Changes" opens immediately, showing the already-known resource group contents.

Actual Behavior

The diff editor opens only after the commit message generation finishes.

Analysis

While commit message generation is running, the Source Control view shows a progress badge. ScmMultiDiffSourceResolver.resolveDiffSource() (src/vs/workbench/contrib/multiDiffEditor/browser/scmMultiDiffSourceResolver.ts) waits via waitForState until that badge is gone before resolving the diff editor contents. This was added to avoid opening an empty diff during the initial repository scan (#216788), but it also treats long-running progress like AI generation as "repository not ready", blocking Open Changes for its entire duration.

Possible fixes:

• Wait on an explicit readiness signal (e.g., initial scan completed) instead of absence of progress badges.
• Or at minimum, add a timeout fallback.

Written with GitHub Copilot + OX Alpha free (stealth model)

CC: Ladislau Szomoru (@lszomoru)