Resumed session loses prior conversation history

Description

When resuming a session, the prior conversation transcript is not restored into the model's context. System reminders, memory files (MEMORY.md), and project instructions (CLAUDE.md) all load correctly, but the actual user/assistant message history from the previous session is missing.

The model has no access to what was previously discussed, so it cannot reference earlier decisions, code changes, or context from the prior session — even though the UI presents it as a continuation.

Impact

• Users believe they're continuing a conversation but the model has amnesia about everything that was said
• Wasted time re-explaining context that should have persisted
• Confusing UX — the session looks resumed but effectively starts fresh

Expected behavior

On resume, prior messages should be available in the model's context (or the user should be clearly warned that history is not restored).

Environment

• Platform: darwin (macOS 24.6.0)
• Shell: zsh
• Model: Claude Opus 4.7 (1M context)