Thinking block chevron does not collapse (click ignored) on macOS 26.3.1

Summary

Clicking the chevron on an extended-thinking block in the transcript does nothing — the block stays expanded. Persists after a full reinstall of the Claude app.

Environment

• Claude Code: 2.1.79
• macOS: 26.3.1 (build 25D2128)
• Kernel: Darwin 25.3.0, arm64 (Apple Silicon)
• App reinstalled: yes (issue persists)

Steps to reproduce

1. Have a conversation where the model produces a thinking block.
2. Click the chevron/disclosure arrow on that thinking block to collapse it.

Expected

The thinking block collapses and the chevron rotates.

Actual

Click is ignored. Chevron does not rotate, block stays expanded. No visible feedback.

Other notes

• Other chevrons (tool output, todo list) — please confirm whether this is thinking-block-specific or affects others too.
• Reinstalling the app did not fix it, so the state likely lives in ~/.claude/ (settings, cached UI state) rather than the app bundle.