Launch a profile's browser and wait for it to start; returns `{pid, cdpUrl}`, a full pool fails with 409 rather than queuing. Optional body `{diagnostic?: bool, headless?: bool, idle_timeout_secs?: integer}`: `diagnostic` opens the profile's proxy without its fingerprint, in a temporary directory; `headless` runs it without a window; `idle_timeout_secs` stops it after that long with no API call naming it (0 = never; default 30 min). A profile that is already running is not relaunched (409).

Diagnostic launch: the profile's proxy, but none of its fingerprint, in a fresh temporary browser directory deleted on stop — no cookies or logins, and nothing is written to the profile. The page sees THIS machine's real values (platform, CPU cores, GPU, screen, timezone, languages): use it to tell whether a site blocks the fingerprint or the IP/proxy, never on an account you care about. The engine's CDP hiding still applies; WebRTC is restricted to the proxy. Default false.

Headless launch: the browser runs without a window (--headless=new). The profile's fingerprint is unchanged, including its screen size, and the engine's CDP hiding still applies. Measured on the macOS engine 154: detector sites score a headless launch like a windowed one — it is NOT a stealth feature and NOT more detectable. A profile that is already running is not relaunched (409): reuse it through the profile list, which reports its cdpUrl and whether it runs headless. Default false.

Stop this browser after this many seconds with no Veilus API/MCP call naming the profile (navigate, click, snapshot, ...). Traffic sent straight to cdpUrl by another client does NOT count: a framework driving the profile over CDP should pass 0, which never stops it. Default: the app setting, 30 minutes unless changed. Profiles opened from the Veilus window are never stopped this way.