Real-profile browsing (browser.use_real_profile) is meant to drive a COPY of
the user's profile headlessly in the background so they can keep working while
the agent acts on their behalf. Instead, on any host with a display it launched
the user's real browser binary HEADED, popping a window that grabbed focus on
every turn.
Root cause: the native launch (which bypasses agent-browser's own launcher to
avoid --use-mock-keychain dropping keychain-encrypted cookies) only added
--headless=new when Linux had no DISPLAY/WAYLAND_DISPLAY. On a normal desktop
the guard was false, so Chrome opened a visible window.
Fix: launch headless by default on every platform. Chrome's NEW headless mode
shares the profile's normal cookie store (unlike legacy --headless), and the
cookie drop we guard against comes from --use-mock-keychain, not from headless
— so real-profile auth still loads. Users who want to watch can opt in via the
existing browser.headed / AGENT_BROWSER_HEADED toggle (honored for real-profile
now, same as the rest of the browser stack); display-less hosts stay headless
regardless so the launch doesn't die at startup.
Live A/B on a real X seat: old argv mapped a Chrome window (focus steal),
--headless=new mapped zero windows while still exposing a working CDP port.
Updated the stale test that pinned 'never passes --headless' (a legacy-headless
premise) to positively assert the chrome launch is --headless=new by default.
d5fd2e9366