[MODEL] Opus 4.7 ignores standing debugging instructions far more than 4.6

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 ignored my instructions or configuration

What You Asked Claude to Do

Compared to Opus 4.6, Opus 4.7 forgets detailed debugging instructions much more frequently. It assumes how things work without verifying against data, even when I remind it roughly every 10 minutes to verify everything with data before drawing conclusions.

Impact: Forces constant re-prompting; conclusions are drawn from assumptions rather than evidence; reliability of long debugging sessions is significantly worse than 4.6.

Repro pattern: Long debugging session with explicit standing rule "verify every claim with data / a tool call before stating it." 4.7 reverts to assumption-based reasoning within ~10 minutes; 4.6 held the rule reliably.

Ask: Investigate instruction-adherence regression for standing/repeated rules in 4.7 vs 4.6.

What Claude Actually Did

Assumes how the simulation works without checking code or simulation data.

Expected Behavior

Check simulation data and read code

Files Affected

Permission Mode

Accept Edits was ON (auto-accepting changes)

Can You Reproduce This?

Yes, every time with the same prompt

Steps to Reproduce

Have a 20k LOC simulation with chaotic behavior ask it to chagne the bahavior in some way.

Claude Model

Opus

Relevant Conversation

Impact

High - Significant unwanted changes

Claude Code Version

2.1.119 (Claude Code)

Platform

Anthropic API

Additional Context

_No response_