Bug: /clear command auto-injected on self-interruption + API 400 concurrency error

Bug: /clear command auto-injected on self-interruption

Claude Code Version: 2.1.19
OS: macOS 15 (Darwin 25.2.0) ARM64

What Happened

1. Claude was running a task (#3 "Add tests for Stop hook context tracking")
2. A pytest command was executing: tests/unit/test_stop_hook.py::TestStopHookContextTr...
3. System displayed "Interrupted - What should Claude do instead?" - but user did NOT interrupt
4. /clear was automatically injected without any user action
5. Session resumed after clear with context restored
6. Then received: "API Error: 400 due to tool use concurrency issues"

Expected Behavior

• /clear should only be injected when user explicitly types it
• Self-interruption should not trigger /clear injection
• No API 400 concurrency errors during normal task execution

Evidence

Screenshot shows the full sequence:

• Test running with 1m 0s timeout
• "Interrupted - What should Claude do instead?" message
• /clear appearing in input without user typing it
• Session resuming with context
• API 400 error appearing

Possible Causes

• Race condition in tool use handling
• Timeout triggering interruption logic incorrectly
• Concurrency issue between task execution and input handling

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Reported via Claude Code CLI