Claude Code repeatedly ignores project-level CLAUDE.md guidelines during implementation

Problem

During extended implementation sessions, Claude Code repeatedly violates the project's CLAUDE.md guidelines despite them being loaded into context. The violations are systematic and require the user to catch and correct each one multiple times.

Observed Behavior

• Claude applies CLAUDE.md rules inconsistently — follows some guidelines early in a session but drifts as the session continues
• When corrected for a specific pattern violation, Claude avoids that exact instance but repeats the same category of violation elsewhere
• Claude does not re-read relevant CLAUDE.md sections before making code changes, even though the CLAUDE.md itself instructs this
• The longer the session, the more frequently guidelines are ignored

Expected Behavior

• CLAUDE.md guidelines should be applied consistently throughout the entire session
• When corrected once for a pattern, Claude should not repeat the same violation type
• Claude should proactively verify changes against CLAUDE.md before presenting them

Impact

The user had to interrupt and correct Claude dozens of times during a multi-day session, significantly slowing development. Many violations were caught only after code was written, requiring rework and additional refactoring cycles.

Environment

• Model: Claude Opus 4.6 (1M context)
• Session type: Extended multi-day implementation session
• CLAUDE.md: Detailed project-specific coding guidelines