Claude Code: Session-Destroying Failures from Compaction Timeouts

🐞 Critical Bug Report: Claude Code Unusable Due to Compaction Lockups & tool_use 400 Crashes

Environment

• Platform:

• [x] Claude CLI (Claude Code)
• Claude CLI version: <!-- output of claude --version -->
• OS: Windows 11 (via WSL)
• Terminal: VS Code Integrated Terminal

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❗ Summary

Claude Code is currently unusable for long-form or agent-based work due to two severe, session-breaking bugs:

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🚫 1. Compaction Lockup (Unrecoverable Timeout)

• When sessions exceed \~2,400 tokens, Claude triggers automatic compaction.
• This process retries up to 10 times with:

``
API Error (Request timed out.) · Retrying in X seconds… (attempt 1/10 to 10/10)
``

• After the 10th retry, the session completely freezes.
• Manually clearing the session results in:

``
404: conversation not found
``

• All progress is lost. The user must restart the conversation from scratch, breaking all continuity and flow.

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❌ 2. tool_use → tool_result Desync (400 Error Crash)

• In active coding sessions, Claude may invoke a tool:

``
tool_use: toolu_01RF5sCUUx9nbB3zCTHNqvCm
``

• This fails with a 400 invalid\_request\_error:

``
"messages.135: tool_use ids were found without tool_result blocks immediately after"
``

• Once this error occurs, the session is permanently broken. Claude cannot continue, and user interaction is blocked.
• The only solution is to clear and restart the entire session, losing all context and history.

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Steps to Reproduce

Compaction Issue:

1. Start session and interact until token count \~2,400
2. Wait for auto-compaction
3. Observe retry loop (10 attempts)
4. Session becomes unresponsive
5. Clearing shows 404, session dead

tool_use Error:

1. Claude triggers a tool (e.g., from UI interaction)
2. Fails to follow with tool_result
3. CLI returns 400 error
4. Session must be cleared and restarted

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Expected Behavior

• Compaction should run smoothly or recover gracefully
• Every tool_use must be immediately followed by a tool_result
• Session context must be preserved — crashes should never require wiping everything

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Actual Behavior

• Compaction stalls → session freezes → unrecoverable 404
• tool_use desyncs → 400 error → session permanently crashes
• Both require full restart, breaking continuity
• Makes Claude Code impossible to use for sustained or structured development

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Severity

🔥 Critical — Full Session Loss
These bugs completely prevent serious usage. They:

• Break long sessions
• Block agent workflows
• Destroy continuity
• Force manual restarts multiple times per day