No Team Fortress 2 codename?
Older Steam Runtime releases were codenamed using Team Fortress 2 character classes, but we've running out of suitable names: scout, heavy, soldier and sniper were all released, spy and medic were internal prototypes, engineer and demoman seem unnecessarily confusing in the context of software engineering for games that sometimes have demos, and pyro doesn't seem like it promises stability :-)
Instead, we expect steamrt4 to be followed by steamrt5, which shouldn't come as a surprise to anyone. We might have made the switch to sequential names sooner, but using sniper for the release based on Debian 11 'bullseye' was just too perfect to miss out on.