500-series errors are server-side, 400 series are client side.
A 500 error is almost never "just you".
( 404 is a client error, because it's the client requesting a file that does not exist, a problem with the client, not the server, who is _obviously_ blameless in the file not existing. )
I know that in principle this is true. However, I have seen claude shadow-throttle my ipv4 address (I am behind CGNAT), in line with their "VPN" policy -- so I do not trust it, frankly.
> A 500 error is almost never "just you".
I know you added the defensive "almost" but if I had a dollar each time I saw a 500 due to the session cookies being sent by the client that made the backend explode - for whatever root cause - well, I would have a fatter wallet.