The server-side OAuthCallbackFlow callback window is 300_000 ms, but the
client starts its #send timer before the RPC command is dispatched. By
the time the callback server actually starts, some time has already been
consumed on the client side. If the user takes the full callback window
plus token exchange, the client 300_000 ms timeout fires first, rejects
login(), cleans up the onOpenUrl listener, and the server response
arrives into a discarded pending entry.
Use 600_000 ms (10 min) on the client — double the server window. The
server will always return an error or success response within its own
window, so this timeout is purely a safety net against server crash or
connection loss and never fires during a normal login.
Miroslav Drbal
c68f90cc7d