Windows: browse cold-start flashes focus-stealing console windows (Bun.spawnSync ignores windowsHide) #1784

Windows: browse cold-start flashes focus-stealing console windows (Bun.spawnSync ignores windowsHide)

Summary

On Windows 11, every cold start of browse (i.e. when no healthy daemon is already running) briefly flashes 2+ focus-stealing console windows on the interactive desktop. They steal foreground focus and interrupt typing in other apps. The cause is several console-subsystem child processes spawned without an effective windowsHide.

Root cause (verified with an elevated Win32_ProcessStartTrace)

Tracing process creation during a cold browse goto shows the flashing conhost.exe windows are parented to:

The key finding

Bun.spawnSync does not honor the windowsHide option on Windows (tested on bun 1.3.11). Adding windowsHide: true to a Bun.spawnSync(...) call has no effect — the child still allocates a console window.

Node's child_process (spawn / spawnSync / execFileSync) does honor windowsHide. (Confirmed in the same trace: the detached daemon node, spawned via Node's child_process.spawn({ detached:true, windowsHide:true }) inside launcherCode, did not get a console window — only the Bun.spawnSync-spawned launcher and git did.)

So the fix is: for Windows console spawns, use Node's child_process with windowsHide:true rather than Bun.spawnSync, and add windowsHide:true to the execFileSync('icacls', …) calls.

Suggested fix

# browse/src/cli.ts
-import { spawn as nodeSpawn } from 'child_process';
+import { spawn as nodeSpawn, spawnSync as nodeSpawnSync } from 'child_process';
@@ startServer() (Windows branch)
-      `{detached:true,stdio:['ignore','ignore','ignore'],env:Object.assign({},process.env,` +
+      `{detached:true,windowsHide:true,stdio:['ignore','ignore','ignore'],env:Object.assign({},process.env,` +
       `${extraEnvStr})}).unref()`;
-    Bun.spawnSync(['node', '-e', launcherCode], { stdio: ['ignore', 'ignore', 'ignore'] });
+    // Bun.spawnSync ignores windowsHide on Windows -> the launcher node flashes a
+    // console. Node's spawnSync honors it.
+    nodeSpawnSync('node', ['-e', launcherCode], { stdio: ['ignore', 'ignore', 'ignore'], windowsHide: true });

# browse/src/config.ts  (and browse/src/find-browse.ts likewise)
+import { execFileSync } from 'child_process';
-    const proc = Bun.spawnSync(['git', 'rev-parse', '--show-toplevel'], { stdout:'pipe', stderr:'pipe', timeout:2_000 });
-    if (proc.exitCode !== 0) return null;
-    return proc.stdout.toString().trim() || null;
+    // Node's execFileSync honors windowsHide; Bun.spawnSync does not.
+    const out = execFileSync('git', ['rev-parse', '--show-toplevel'],
+      { encoding:'utf-8', timeout:2_000, windowsHide:true, stdio:['ignore','pipe','ignore'] });
+    return out.trim() || null;

# browse/src/file-permissions.ts  (both execFileSync('icacls', …) calls)
-        { stdio: 'ignore' },
+        { stdio: 'ignore', windowsHide: true },

The detached daemon spawn just needs the windowsHide:true added to its options object (Node honors it).

Repro

1. Windows 11, no browse daemon running.
2. browse goto https://example.com.
3. Observe 2+ console windows flash and steal focus. An elevated Win32_ProcessStartTrace shows the conhost.exe parents are node (launcher), git, and icacls.

Environment

• Windows 11, gstack @ 920a13a, bun 1.3.11, Node from C:\Program Files\nodejs.
• Default headless path. (Separately, chrome-headless-shell.exe is a console-subsystem binary; launching full chromium with --headless=new avoids that one too, but it was not the cause of these particular flickers.)