Not a serious test, but I tried M2.5 briefly in OpenCode on a very simple task equivalent to the last commit or two here[0] and it was really, really bad. This is a 250 line self-contained standalone script and what it does is very simple. M2.5 would have required far more detailed prompting to get me the result Opus 4.6 can do with the vaguest hints.

[0]: https://github.com/oxidecomputer/console/pull/3070/commits