Chrome.identity works perfectly without asking for credentials - google-chrome

Question

I have implemented the chrome.identity launchWebAuthFlow to authenticate users of a web extension against an oauth2 provider and the entire flow works perfectly, I receive the access token back in the redirect URL, I extract the token using a regex and then it is valid and accepted to query the APIs.
However, I do not understand why it does not prompt anymore for credentials when I launch again the launchWebAuthFlow. Instead, it retrieves another (valid !) token in the background. Don't get me wrong, I like this, and I prefer it works in the background, but I just don't understand how. Even after clearing all cookies and local data, when I launch the launchWebAuthFlow again it just works in the background without asking for credentials...where are they stored?
Also, not sure if that helps, but my flow is the following:
extension ->oauth2 server->azure ad SSO->enter credentials->redirect to extension
So the real authentication is managed by Azure AD. However, even when I'm signed out from Microsoft, the extension keeps getting a valid auth token when the below code is triggered and without asking for credentials...so the credentials must be stored somewhere...
chrome.identity.launchWebAuthFlow(
{
url: dev.identity_url(),
interactive: true
},
function (responseWithToken) {
// the access token needs to be extracted from the response.
console.log(responseWithToken);
let token = responseWithToken.match(/(?<=access_token=).*(?=&token_type)/);
token = token[0];
chrome.storage.local.set({ "auth-token": token }, function () {
console.log(`Access Token has been saved: ${token}`);
});
}
);