Terminal display corruption: rendered output overlaps/duplicates mid-session

[AThraen]

Symptom

The terminal display occasionally gets visibly corrupted — chunks of previously-rendered output overlap with current output. The bottom toolbar/status-bar area can appear duplicated, and lines from different parts of the buffer collide on the same row. Screenshot shows it happening inside a Claude session (ink TUI in auto-mode, mid-stream).

(Screenshot will be attached by the reporter — local copy at image-cache/18bf3a04-cb45-439b-ab12-be721bbe0ad9/1.png.)

Likely causes (in order of likelihood)

1. Resize during in-flight TUI redraw. Ink redraws by ANSI cursor positioning, not full-screen clear. If the WebView2 reports a new size while ink is mid-frame, the next frame writes to addresses that no longer match the visual grid → overlap.
2. PTY size drift. xterm.js's reported cols/rows and the PTY's ResizePseudoConsole value briefly disagree (e.g. resize message races with output). The shell renders at one size while xterm renders at another.
3. xterm.js alternate-screen-buffer transition. Switching in/out of the alt buffer (\e[?1049h/l) mid-stream can leave stale rows visible if the transition lands between two write chunks.
4. Partial-recovery from a stall. May correlate with the intermittent typing-freeze report — if the PTY read loop or WPF dispatcher stalls and then catches up, a backlog of small output chunks could replay out of phase with the app's cursor model.

Repro signals to collect

Not reliably reproducible. When it happens, useful to note:

• Whether the WPF window or pane was resized in the last few seconds
• Whether the Claude/TUI session was streaming a long response when corruption appeared
• Whether enabling Settings > Diagnostics > Trace terminal input/output (PR feat: terminal trace setting + shutdown/restore stability fixes #36) preceding the event captures unusual [DEBUG-tt] gaps in crash.log

Workarounds

• Resize the pane — typically triggers an app-side redraw and clears the corruption
• Scroll to the top of the buffer and back
• Worst case: close and reopen the session

Related

• PR feat: terminal trace setting + shutdown/restore stability fixes #36 added DebugTerminalTrace for the input-freeze investigation — same instrumentation may pin this one if it correlates with a stall