Planning the 2.40 release

Developers
1

It’s that time again!

We’re coming up on 4 months post-2.39 release (May 19th).

I’d like to propose the following dates for the 2.40 release:

Feature freeze on Tuesday, September 8th 2026
Release on Tuesday, September 14th 2026

As always, please use this thread if you have any thoughts on those dates, or if you need a pull request reviewed or think an issue is a high priority for this release.

For those curious about how the Stan releases are organized, please read the Stan Release Cycle design document.

cc @stevebronder @avehtari @andrjohns @Florence_Bockting

2

For my part, I think I’d really just like to see

Merged before the freeze. Add map-like helpers by florence-bockting · Pull Request #3346 · stan-dev/math · GitHub and Fix wiener_lpdf derivative with respect to w by martonaronvarga · Pull Request #3324 · stan-dev/math · GitHub would be nice as well

3
  • I should test using laplace_latent_solve(_tol) in practice

Tested and it works, but testing revealed that standalone generated quantities is not setting rng seed correctly (I have a working draft PR for this), and one other bug for which I’ll submit the issue and PR tomorrow

4

Hello, I am curious if the multi-thread tuple issue mentioned here will be addressed in the coming release of cmdstan? (Though technically it’s the Stan Math library that needs to be updated.)

5

@Yingnan_Gao I will try to take a look and flag it to other developers

6

I’ve made the tracking issue here