I have had this issue for some time now, whenever the agent wants to use a browser (in my case I use brave or edge) it attempts to launch the browser but ultimately fails, and no this is not the $HOME error because I have had this issue before and I had fixed it when using playwright test browsers.
I managed to fix that error via commands i found on other threads. I still verified it is correct and to counter this (current) issue I used playwright test browser which were working but they worked for some tasks but I don’t know why but there is another error I get when attempting to access some sites, that the Agent was not allowed to load that particular website, I even explicitly added it to the allow list which led me to believe it could be the test browser problem because the websites had cloudflare protection and i tried solving the captcha in the test browsers but it wouldn’t work but would work on brave and edge.
Because of this error I tried using my native browser again since I thought since now there have been multiple updates maybe it might’ve been fixed but nope, I tried reinstall playwright on my own or even let antigravity do it, also tried reinstalling antigravity, installing an older version of antigravity but to no avail. When the agent attempts to launch the browser it shows Launching browser at the bottom right of the IDE and the browser window pops up for a second and closes itself and IDE shows Successfully launched browser. I also noticed that the playwright node.js is also actively running in the background under Antigravity process I found this when I tried uninstalling playwright.
I am on Windows 11 25H2
Edit: The agent allowance error is this error: “The agent was prevented from accessing some sites”
Edit 2: Tried using the playwright MCP server by manually adding it in the raw config file and pointed the executable to my brave executable and asked the agent to call the MCP server instead and that seems to work