qBittorrent (or its reverse proxy) was returning 204 No Content with an SID
cookie and no body on a successful login, but the client only treated the
response as success if body == "Ok." or the cookie was in the parsed
requests cookie jar (resp.cookies.get("SID")). In the reported case the
Set-Cookie header was present (set-cookie=yes) yet the jar was empty —
requests doesn't always populate the jar from such headers (proxy-set/oddly-
attributed cookies) — so a valid login was reported as "Unexpected response".
The user re-entering correct credentials never helped.
Detect a successful login from EITHER the parsed jar OR the raw Set-Cookie
header (cookie name == SID). qBittorrent only sets SID on a valid login, so
this remains authoritative. The diagnostic now lists the cookie names it saw
for future-proofing.
New regression test reproduces the exact 204 + Set-Cookie SID + empty jar
case. 387/387 backend tests pass; ruff clean.
Developer
7e53edfcc6