fix(core): drain stdin on exit to prevent escape sequence leakage (#34134)

FrozenPandaz · web-flow · commit 6754cde03abe · 2026-01-17T16:30:38.000Z
## Current Behavior

When exiting the TUI (especially via Ctrl+C), escape sequences leak to
the terminal:
```
^[]11;rgb:2121/2121/2121^[\^[[55;1R^[[?62;22;52c
```

This happens because the TUI queries terminal background color via OSC
11 to detect dark/light mode. The terminal responds with an escape
sequence, but if the program exits before fully consuming the response,
it appears in the terminal output.

## Expected Behavior

Clean terminal state after TUI exits, with no escape sequence artifacts.

## Related Issue(s)

N/A - discovered during development

## Solution

Added `drain_stdin()` function that polls and consumes any pending
terminal events before disabling raw mode. This clears any lingering OSC
responses (like the background color query response) before the terminal
is restored.

```rust
fn drain_stdin() {
    use std::time::Duration;
    while crossterm::event::poll(Duration::from_millis(5)).unwrap_or(false) {
        let _ = crossterm::event::read();
    }
}
```

The 5ms timeout is long enough to catch pending responses but short
enough not to noticeably delay exit.
diff --git a/packages/nx/src/native/tui/lifecycle.rs b/packages/nx/src/native/tui/lifecycle.rs
@@ -571,6 +571,10 @@ pub fn restore_terminal() -> napi::Result<()> {
     // Clear terminal progress indicator
     App::clear_terminal_progress();
 
+    // Drain pending terminal responses (e.g., OSC color query responses)
+    // to prevent escape sequences from leaking to the terminal on exit
+    super::tui::drain_stdin();
+
     if crossterm::terminal::is_raw_mode_enabled()? {
         crossterm::execute!(
             std::io::stderr(),
diff --git a/packages/nx/src/native/tui/tui.rs b/packages/nx/src/native/tui/tui.rs
@@ -3,7 +3,7 @@ use crate::native::tui::theme::THEME;
 use color_eyre::eyre::Result;
 use crossterm::{
     cursor,
-    event::{Event as CrosstermEvent, KeyEvent, KeyEventKind},
+    event::{self, Event as CrosstermEvent, KeyEvent, KeyEventKind},
     execute,
     terminal::{EnterAlternateScreen, LeaveAlternateScreen},
 };
@@ -53,6 +53,18 @@ pub struct Tui {
     pub current_mode: TuiMode,
 }
 
+/// Drain any pending input from stdin to prevent escape sequence leakage.
+/// This consumes terminal responses (e.g., from OSC color queries) that may
+/// arrive after a query was sent but before the response was fully read.
+pub(crate) fn drain_stdin() {
+    // Poll and consume any pending terminal events
+    // Note: Duration::ZERO can incorrectly return false with use-dev-tty feature
+    // See: https://github.com/crossterm-rs/crossterm/issues/839
+    while event::poll(Duration::from_millis(5)).unwrap_or(false) {
+        let _ = event::read();
+    }
+}
+
 impl Tui {
     pub fn new() -> Result<Self> {
         Self::new_with_mode(TuiMode::FullScreen)
@@ -75,15 +87,23 @@ impl Tui {
         // non-interactive environments, stdin is redirected so these queries hang.
         // By checking upfront, we avoid flakiness from deferred initialization.
         let inline_terminal = if Self::is_stdin_interactive() {
-            let inline_height = crossterm::terminal::size()
-                .map(|(_cols, rows)| rows)
-                .unwrap_or(24);
-            Some(ratatui::Terminal::with_options(
+            let size = crossterm::terminal::size();
+            debug!("Terminal size: {:?}", size);
+            let inline_height = size.map(|(_cols, rows)| rows).unwrap_or(24);
+            ratatui::Terminal::with_options(
                 CrosstermBackend::new(std::io::stderr()),
                 ratatui::TerminalOptions {
                     viewport: ratatui::Viewport::Inline(inline_height),
                 },
-            )?)
+            )
+            .inspect(|_| {
+                debug!(
+                    "Inline terminal created successfully with height {}",
+                    inline_height
+                )
+            })
+            .inspect_err(|e| debug!("Inline terminal not created: {}", e))
+            .ok()
         } else {
             debug!("Inline terminal not created: stdin is not a TTY");
             None
@@ -278,6 +298,10 @@ impl Tui {
         if crossterm::terminal::is_raw_mode_enabled()? {
             self.flush()?;
 
+            // Drain pending terminal responses (e.g., OSC color query responses)
+            // to prevent escape sequences from leaking to the terminal on exit
+            drain_stdin();
+
             // Only leave alternate screen if we're in full-screen mode
             match self.current_mode {
                 TuiMode::FullScreen => {
diff --git a/packages/nx/src/tasks-runner/is-tui-enabled.ts b/packages/nx/src/tasks-runner/is-tui-enabled.ts
@@ -29,8 +29,10 @@ export function shouldUseTui(
   skipCapabilityCheck = process.env.NX_TUI_SKIP_CAPABILITY_CHECK === 'true'
 ) {
   // If the current terminal/environment is not capable of displaying the TUI, we don't run it
+  const hasValidSize = process.stdout.columns > 0 && process.stdout.rows > 0;
   const isCapable =
-    skipCapabilityCheck || (process.stderr.isTTY && isUnicodeSupported());
+    skipCapabilityCheck ||
+    (process.stderr.isTTY && isUnicodeSupported() && hasValidSize);
 
   if (typeof nxArgs.tui === 'boolean') {
     if (nxArgs.tui && !isCapable) {
