prevent flickering windows on Windows by adding DETACHED_PROCESS

[acarl005]

Description

With Warp on Windows running, sometimes random console windows flicker into view. Very annoying. This PR fixes that.

Recording.2026-05-02.203454.mp4

Apparently CREATE_NO_WINDOW only prevents the direct child from creating a visible window. It doesn't prevent the child from inheriting the console host. Grandchildren might still create a visible window since it doesn't pass the same creation flags (unlike console host, the flags are NOT inherited). DETACHED_PROCESS is necessary because it starts the background shell without any console attached in the first place, so PowerShell and its console-subsystem children have no foreground console host to flash.

Linked Issue

Fixes #11224

Testing

I don't see flickering windows anymore.

[oz-for-oss]

@acarl005

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[oz-for-oss]

Overview

This PR adds DETACHED_PROCESS to the Windows async command wrapper so background console-subsystem processes are started without inheriting Warp's console attachment, while preserving the existing job breakaway behavior.

Concerns

• No blocking correctness, security, or spec-alignment concerns found.
• One suggestion notes that CREATE_NO_WINDOW is ignored when DETACHED_PROCESS is present, so the effective flag set can be made clearer.

Verdict

Found: 0 critical, 0 important, 1 suggestions

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[oz-for-oss]

💡 [SUGGESTION] DETACHED_PROCESS causes Windows to ignore CREATE_NO_WINDOW, so keeping both makes the effective console behavior harder to reason about.

Suggested change

	let flags = Threading::CREATE_NO_WINDOW.0
	| Threading::DETACHED_PROCESS.0
	| Threading::CREATE_BREAKAWAY_FROM_JOB.0;
	let flags = Threading::DETACHED_PROCESS.0
	| Threading::CREATE_BREAKAWAY_FROM_JOB.0;