Windows Terminal stalls when XTVERSION is sent before alt-screen

[Hona]

Summary

On a real Windows Terminal-attached session, OpenTUI startup can poison the session so ordinary JS timers and resize handling stall for seconds. The trigger appears to be sending XTVERSION (ESC[>0q) before switching to alt-screen.

Reordering startup so queryTerminalSend() runs after setupTerminalWithoutDetection(useAlternateScreen) made both the minimal harness and the real opencode TUI resize smoothly in local testing.

Symptoms

• resize (SIGWINCH) appears delayed by 5-30s
• plain setTimeout(..., 100) can be delayed by the same amount
• Ctrl+C can also feel delayed while in the stalled state
• once resize/render actually runs, the work is fast

Environment

• Windows Terminal / real attached host session
• Windows 11 / ConPTY path
• reproduces with both Bun and Node
• does not reproduce in a synthetic PTY driven by bun-pty

Smallest standalone repro

This can be reproduced outside OpenTUI with a tiny script that only sends XTVERSION before alt-screen and logs watchdog gaps:

process.stdout.write("\x1b[>0q\x1b[?1049h\x1b[?25l")
setInterval(() => {
  const now = performance.now()
  const gap = now - last
  last = now
  if (gap > 200) console.log({ gap })
}, 50)
setTimeout(() => process.exit(0), 4000)

Observed result in the real terminal:

• \x1b[>0q before alt-screen: watchdog lag entries appear
• \x1b[>0q after alt-screen: smooth
• no XTVERSION: smooth

I also verified the same ordering effect under both:

• node
• bun

So this does not look Bun-specific.

OpenTUI-specific evidence

Current startup order in packages/core/src/zig/renderer.zig:

self.terminal.queryTerminalSend(writer)
writer.flush()
self.setupTerminalWithoutDetection(useAlternateScreen)

That matches the bad ordering.

Relevant local experiments against the real bugged textarea harness:

• OPENTUI_MINIMAL_SETUP=1: smooth
• OPENTUI_SKIP_QUERY_SEND=1: smooth
• OPENTUI_SKIP_PENDING_QUERIES=1: still laggy
• OPENTUI_SKIP_ENABLE_FEATURES=1: still laggy
• OPENTUI_SKIP_XTVERSION=1: smooth
• OPENTUI_SKIP_QUERY_WRAPPER=1: still laggy

This points specifically at the initial query send, and more specifically at XTVERSION.

Likely fix

Move queryTerminalSend(writer) to run after setupTerminalWithoutDetection(useAlternateScreen).

That reorder fixed the issue in my local Windows Terminal testing for:

• a minimal OpenTUI TextareaRenderable harness
• the real opentui example selector
• the real opencode TUI (after ensuring the patched DLL was actually loaded)

Notes

The problem did not reproduce when I replayed the same query bundles in a synthetic PTY or when the same query bundle was sent after alt-screen, which is why the ordering looks important rather than the query content alone.

[Hona]

I created an upstream issue for WT microsoft/terminal#20092