[Bug] Claude degraded performance: inconsistent error corrections across codebase

**Bug Description**
For approximately the past two days, I’ve felt that Claude has become “dumber,” or less intelligent. Before, whenever I pointed out an error, it would correct it everywhere necessary without me having to ask. Over the past few days, however, it only fixes the issue in one place, and I have to guide it to make the same correction elsewhere.

Fortunately, I know my code well enough to guide it, but if someone unfamiliar with the code were using it, Claude could end up introducing even more problems. Besides, we expect an AI like Claude Opus running at maximum effort to handle this automatically, without requiring constant instructions.

This has left me feeling somewhat disappointed and frustrated over the past few days because I’m taking much longer to accomplish tasks that should be quick and using more tokens than necessary.

**Environment Info**
- Platform: win32
- Terminal: null
- Version: 2.1.260
- Feedback ID: df325fb6-91c6-4a6f-a819-fafe0a75b5b6

**Errors**
```json
[{"error":"TelemetrySafeError: VirtualMessageList: itemKeys/messages length desync (keys=1206 messages=1205 range=[1189,1206))\n at N$t (B:/~BUN/root/chunk-9tytjqtz.js:36:26122)\n at Sme (B:/~BUN/root/chunk-9tytjqtz.js:36:18954)\n at Ha (B:/~BUN/root/chunk-gcsbr8vy.js:18:20017)\n at Nu (B:/~BUN/root/chunk-gcsbr8vy.js:18:38158)\n at Yh (B:/~BUN/root/chunk-gcsbr8vy.js:18:84182)\n at Tg (B:/~BUN/root/chunk-gcsbr8vy.js:18:83184)\n at Qu (B:/~BUN/root/chunk-gcsbr8vy.js:18:83013)\n at Hh (B:/~BUN/root/chunk-gcsbr8vy.js:18:79547)\n at Ve (B:/~BUN/root/chunk-gcsbr8vy.js:18:6254)\n at Fe (B:/~BUN/root/chunk-gcsbr8vy.js:18:4788)","timestamp":"2026-09-18T02:08:18.047Z"}]
```

Start by reproducing the reported behavior on win32 with version 2.1.260, using feedback ID df325fb6-91c6-4a6f-a819-fafe0a75b5b6. Review the VirtualMessageList itemKeys/messages length-desync error in the reported bundled chunks and determine whether it relates to inconsistent corrections. Done means the issue has a reproducible cause and verified behavior for corrections across the codebase.

Written by the indexing model from the issue text.