Planning the 2.39 release

[WardBrian]

It’s that time again!

We’re coming up on 4 months post-2.38 release (January 13th).

I’d like to propose the following dates for the 2.39 release:

Feature freeze on Monday, May 11th 2026
Release on Monday, May 18th 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.

cc @stevebronder @avehtari @charlesm93 @syclik

[WardBrian]

In terms of PRs for me, I currently have a few small ones:

• Detect generated quantities timing in stan_csv_reader by WardBrian · Pull Request #3377 · stan-dev/stan · GitHub
• Add convergence information to optimization outputs by WardBrian · Pull Request #3379 · stan-dev/stan · GitHub
• Fix copy/paste error in qr() documentation by WardBrian · Pull Request #940 · stan-dev/docs · GitHub

I am also monitoring the laplace documentation PR

[spinkney]

For the docs, I think the two issues would be good to get in. Having info on how to work with PRs from forks is a great idea. The other one for mdivide_* is easy and we just need to add. The wiener diffusion model needs docs if we’re exposing the function to users for the next release.

I think the gamma_lccdf fix is good to go after the @stevebronder fix. I’m deferring to @stevebronder or @syclik to do the final approval and merge.

Docs

• Instructions for working with PRs from forks · Issue #936 · stan-dev/docs · GitHub
• Missing functions: mdivide_left, mdivide_right · Issue #908 · stan-dev/docs · GitHub
• entry for wiener diffusion model by Franzi2114 · Pull Request #934 · stan-dev/docs · GitHub

Math

• Fix gamma lccdf by syclik · Pull Request #3275 · stan-dev/math · GitHub