Webterm

Screenshot Debugging Skill

Purpose

Diagnose terminal screenshot corruption caused by incomplete terminal-state updates.

When to Use

• SVG screenshots show stale or overlaid text.
• Live WebSocket output looks correct but /screenshot.svg does not.
• Issues appear with full-screen TUIs (tmux/vim/less).

Procedure

1. Capture terminal bytes
   • Capture PTY output around the failing action.
2. Replay into the Go tracker
   • Feed bytes through internal/terminalstate (go-te based).
   • Confirm whether buffer state diverges from expected terminal behavior.
3. Check preprocessing/filtering
   • Validate DA filtering and any partial-sequence buffering logic.
4. Check dirty/refresh logic
   • Verify tracker updates happen before screenshot cache decisions.
5. Add regression coverage
   • Add a focused Go test and (when useful) fuzz corpus seed.
6. Verify
   • Run make check and re-test the real scenario.

Notes

• Prefer reproductions from real PTY captures over synthetic minimal sequences.
• If rendering differs only in dashboard thumbnails, inspect SSE activity gating and screenshot cache TTL/invalidations.

Source: rcarmo/webterm — distributed by TomeVault.