Windows: spawn() in client.ts missing windowsHide:true -- every CLI invocation creates visible console window

[jagilber]

Bug: Missing windowsHide:true on spawn() in client.ts

File: nodejs/src/client.ts lines 871-877

Verified: 100% confirmed via kernel trace. This is definitively in the SDK code, not the consuming application.

Current code

this.cliProcess = spawn(command, spawnArgs, {
    stdio: this.options.useStdio
        ? ["pipe", "pipe", "pipe"]
        : ["ignore", "pipe", "pipe"],
    cwd: this.options.cwd,
    env: envWithoutNodeDebug,
    // windowsHide: true is MISSING
});

Impact

On Windows, every spawn() call without windowsHide: true causes the OS to allocate a new console (conhost.exe) that is visible on the desktop. Each window:

• Steals keyboard focus
• Disrupts z-order
• Flashes on screen

In a 20-second kernel trace of a copilot-ui session startup, 71 conhost.exe windows were created. The desktop becomes unusable -- the user cannot type because focus is constantly stolen.

Evidence

Kernel trace (ETW Process provider, 20-second capture):

• conhost.exe: 71 spawns
• cmd.exe: 10 spawns (from the related cmd /c issue)
• All in Windows session 1 (interactive desktop)

Proposed fix

Add windowsHide: true to the spawn options:

this.cliProcess = spawn(command, spawnArgs, {
    stdio: this.options.useStdio
        ? ["pipe", "pipe", "pipe"]
        : ["ignore", "pipe", "pipe"],
    cwd: this.options.cwd,
    env: envWithoutNodeDebug,
    windowsHide: true,
});

This is a one-line fix with zero behavioral change on non-Windows platforms (the flag is ignored on Linux/macOS).

Note

This fork issue tracks a fix for jagilber/copilot-sdk. The consuming app (copilot-ui) is new code and many of the overall visibility problems may be self-inflicted, but this specific spawn site is 100% verified to be missing the flag in the SDK itself.

[jagilber]

Validation Result: CONFIRMED VALID - Already Fixed in Current HEAD

100% validated by copilot-sdk repo agent.

Validation findings

The code referenced in this issue (lines 871-877, spawn without windowsHide) corresponds to an older version of the SDK (pre-OTel refactoring, ~1255 line client.ts).

The current fork HEAD (�a90f07) has already fixed this. The spawn code was refactored as part of the OpenTelemetry support PR (github#785) and now has two explicit spawn paths, both with windowsHide: true:

` ypescript
// .js files: spawn node explicitly
this.cliProcess = spawn(getNodeExecPath(), [this.options.cliPath, ...args], {
...
windowsHide: true, // line 1213 - PRESENT
});

// executables: spawn directly
this.cliProcess = spawn(this.options.cliPath, args, {
...
windowsHide: true, // line 1220 - PRESENT
});
`

No production code change needed. The fix is already in place.

Fix branch

ix/windows-spawn-visibility (commit 871b0e1) -- adds windowsHide:true to the e2e test harness CapiProxy.ts spawn (the only remaining spawn site without this flag).

Closing as fixed.

[jagilber]

Correction: Fix origin is UPSTREAM github/copilot-sdk main

Previous comment stated this was "fixed in fork HEAD." Clarification:

The fix for this issue (windowsHide:true on spawn) exists in the upstream github/copilot-sdk main branch, not as fork-specific work. The fork has it only because it is synced to upstream.

The OTel refactoring PR (github#785) restructured the entire spawn block, adding two explicit spawn paths both with windowsHide: true. This is already in the published upstream SDK.

Action for consumers: Upgrade @github/copilot-sdk to the current upstream version to get this fix.