CLAUDE.md instruction adherence significantly degraded since ~April 4

Custom instructions in CLAUDE.md are being ignored at a significantly higher rate since approximately 2026-04-04. This is observed across both Claude Code 2.1.87 and 2.1.92 -- it is not version-specific.

Specific CLAUDE.md instructions that are consistently skipped:

• Plan mode before non-trivial tasks (never adhered)
• End-to-end verification before declaring work complete (never done)
• Checking documentation before guessing (guesses repeatedly instead)
• Pausing after repeated failures to diagnose root cause (loops/thrashes instead)

Prior to ~April 4, these same instructions in the same CLAUDE.md file were followed more reliably. The file has not changed in ways that would explain the drop. Something else shifted -- possibly model-side, possibly in how CLAUDE.md content is weighted during generation.

This is not occasional drift. It is a consistent, noticeable regression in instruction adherence.