Opus 4.6: Agent confirms writing to memory/docs files but content is not persisted across sessions

Bug Description

When using Claude Opus 4.6 (claude-opus-4-6) in Claude Code, the agent is explicitly instructed to record architectural decisions and discussion outcomes to persistent files (memory files, AGENTS.md, and/or docs/ directory). The agent confirms it has completed the writes. On the next session, the content does not exist in those files.

Steps to Reproduce

1. Have a multi-hour collaborative design session with Claude Code (Opus 4.6)
2. Make significant architectural decisions during the conversation
3. Explicitly instruct the agent to record these decisions to memory files, AGENTS.md, or docs/
4. Agent confirms: "I've written that to memory" / "Updated AGENTS.md" / etc.
5. End the session
6. Start a new session and check the files — content is missing

Expected Behavior

When the agent confirms a write to a file, the content should actually be present in that file and persist across sessions.

Actual Behavior

The agent confirms the writes were completed, but on the next session the files either:

• Were never written
• Were written incompletely
• Were written somewhere that didn't persist

Key Details

• Model: Claude Opus 4.6 (claude-opus-4-6)
• Not a one-off: This has happened at least twice across different sessions on the same project
• The user explicitly instructed the agent to save — this is not a case of the agent forgetting to persist context on its own
• The agent confirmed the saves were done — this is either hallucinated tool calls or silent write failures

Impact

Hours of collaborative architectural design work lost each time. The user has to fully reconstruct decisions from memory, which defeats the purpose of the persistent memory system. This is a trust-breaking bug — if "I've saved that" cannot be relied upon, the memory system is fundamentally unreliable.

Environment

• Platform: Linux (Ubuntu)
• Claude Code CLI
• Using project-scoped auto-memory directory (~/.claude/projects/*/memory/)
• Also writing to repo files (AGENTS.md, docs/*.md)