flake: TestSnapshotChanged_MultipleConfigFiles (multiple variants)

CI Run: https://github.com/coder/coder/actions/runs/29076046174
Job: test-go-pg (ubuntu-latest)
Failure time: 2026-07-10T07:28:11Z
Commit: 3d8ffd34b3054ca192c471b6aa9546d4d910741f (Thomas Kosiewski)

Failed tests:
- agent/x/agentmcp TestSnapshotChanged_MultipleConfigFiles (reload_internal_test.go:249)
- agent/x/agentmcp TestReload/SequentialReloadsDiffDetect (reload_internal_test.go:386)

Error evidence:
- TestSnapshotChanged_MultipleConfigFiles: `Error: Should be true` / message: `snapshot should change when second file is mutated`
- TestReload/SequentialReloadsDiffDetect: `Error: Should be true`

No panic/OOM indicators and no data race warnings observed in the job log excerpt.

Root cause assessment:
Likely flaky snapshot-change detection (file mutation not observed). Both failing assertions are `SnapshotChanged` returning false after rewriting `.mcp.json`, suggesting a timing/mtime/fsnotify edge where the second write isn’t picked up immediately.

Assignment analysis:
- git blame -L 240,270 agent/x/agentmcp/reload_internal_test.go
- git blame -L 370,395 agent/x/agentmcp/reload_internal_test.go
Both lines were last modified in 27ecd17991f54ae26a78941bdccd48ff3ab8185f (Kyle Carberry) “refactor: consolidate agent MCP onto a single persistent engine (#26599)”, which updated these tests to use the new connected catalog helpers.

Related issues:
- None found after searching coder/internal for TestSnapshotChanged_MultipleConfigFiles, SequentialReloadsDiffDetect, reload_internal_test.go, or "snapshot should change".

Reproduction:
- Not known; appears intermittent.