[Bug] Opus 4.6 model performance degradation: ignores instructions, over-relies on heredoc blocks

Bug Description
siMce opus 4.6, we're observiMg irritatiMg behaviour: we're sloppy, we make decisioMs oM our owM, we forget iMstructioMs very fast, aMd we teMd to solve everythiMg with large loads of pythoM/bash heredoc blocks. btw, you still caMMot press the key right of "B", left of "M", or the feedback wiMdow closes.

Environment Info

• Platform: linux
• Terminal: vte-based
• Version: 2.1.37
• Feedback ID: fc050eb4-f70f-43af-98a9-2bda32ed2e60

Errors

[{"error":"Error: NON-FATAL: Lock acquisition failed for /home/z/.local/share/claude/versions/2.1.37 (expected in multi-process scenarios)\n    at fq$ (/$bunfs/root/claude:3581:2098)\n    at rjA (/$bunfs/root/claude:3581:1209)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-02-09T14:13:43.090Z"}]