Silent conversation truncation mid-session without user-triggered compact

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Claude Code v2.1.90 · Opus 4.6 (1M context) · VS Code terminal · macOS

What happens: During a normal session at low context usage (~5%), earlier messages disappear from the visible conversation
UI without the user running /compact. The conversation appears to restart mid-session from a later point, losing the
visible history of earlier exchanges.

Steps to reproduce:

1. Start a new session that continues from a previous conversation (previous session ended with user-triggered /compact)
2. Work normally — several exchanges (chat, tool calls, file edits)
3. At some point, the earlier messages in the current session silently vanish from the terminal UI
4. The conversation visually appears to start from a later point (e.g., mid-way through tool operations)

Expected behavior: Conversation history remains visible in the terminal for the entire session unless the user explicitly
runs /compact or context window fills up and triggers automatic compression.

Observed behavior: Visible conversation history is silently truncated during normal work. No compact was triggered by the
user. No loading delay (normal /compact takes 1-3 minutes to process). Happens instantly and silently. Context usage was
~5% at the time — nowhere near the threshold for automatic compression.

Frequency: Observed across two consecutive sessions (2026-04-03 and 2026-04-04).

What Should Happen?

claude should show teh full earlier messages until compact.

Error Messages/Logs

Steps to Reproduce

just chat with claude...

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

v2.1.90

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

<img width="1018" height="268" alt="Image" src="https://github.com/user-attachments/assets/514c25fe-9865-4edd-b5ab-6e990a7201ee" />