The cookie that stayed behind

An HTTP client remembers cookies so you don't have to send them yourself with every request. When you clear that store, you expect the next request to leave them behind. In this run, one came along anyway.

Flash-Next's assignment was to give HTTPX a deterministic cookie store: predictable rules for keeping cookies, choosing which ones belong on a request, and sending them in a stable order. The implementation reached into the client as well as adding the store itself. The agent wrote tests and caught problems along the way, including how host-only cookies behaved on subdomains.

Its own 39 tests passed. The separate official grader found one more case: call clear() without arguments, then make another request. The outgoing header still contained a=1.

The cause was small enough to read in one line. The filter kept a cookie if the supplied domain and path were both None. With neither argument supplied, every cookie qualified to stay. The default way to empty the store did the opposite.

After about 12 minutes of agent work, the result was 114 of 115 feature checks and all 1,281 regression checks passed. That's a lot of working behavior beside a very ordinary bug. I'd want this failure spelled out in a code review rather than rounded away as “almost all tests passed.” The exact result and run settings are below.