Opus 4.6 1m has degraded performance and now acts dumber than Sonnet 3.5

Preflight Checklist

• [x] I have searched existing issues for similar behavior reports
• [x] This report does NOT contain sensitive information (API keys, passwords, etc.)

Type of Behavior Issue

Claude modified files I didn't ask it to modify

What You Asked Claude to Do

I do not know what is going on but ever since around the time the opus models moved to the 1 million token context window I have found the models almost unusable. The change is night and day. This si not context bloat this is very simple prompts and tasks with a freshly cleared context and I am not able to trust anything going on anymore. I just had Opus reverse it's own decision 4 times in a row and search the web 2 times with a drizzle thing for on conflict do update and it literally could not stop tearing everything down and rebuilding it using raw sql and using drizzle after being told use drizzle and looking up the exact things to use ???????

Another case, II literally say hey we are using too small of a batch size on these upserts, increase the batch size and it claims to do this. An Hour later I find out it batch inserted one column's dat form the whole table and for the rest of the table was doing sequential single upserts per record???? Like WHAT? This is obviously retarded behavior.

The other day I literally couldn't get it to widen a dialogue component. A shadcn dialogue component??? I said make that dialogue wider and it literally cannot or would not do it, we are talking about things Claude sonnet 3.5 used to do and do them faster!!!

This is a large enough issue that if it does not improve very VERY VERY soon I am leaving Anthropic I feel like I am just getting ripped off at this point.

What Claude Actually Did

Literally failed to follow simple single line instructions as listed above

Expected Behavior

Behavior and intelligence equal to or greater than previous models and releases, this is a HUGE degradation in performance on basically every metric

Files Affected

Permission Mode

Accept Edits was ON (auto-accepting changes)

Can You Reproduce This?

Haven't tried to reproduce

Steps to Reproduce

This is not exactly reproducible its a general lack of performance in every task over the last 3 weeks or so. Simple things Claude used to finish in 2 seconds are now not done correctly and take longer. I am filing this to start signaling that there is something going wrong, something is deeply incorrect about the way we are currently interacting with Opus, it feels dumber than Claude Sonnet 3.5 most of the time.

Claude Model

Opus

Relevant Conversation

Impact

Critical - Data loss or corrupted project

Claude Code Version

v2.1.81

Platform

Anthropic API

Additional Context

_No response_