# Planning the 2.40 release

**URL:** <https://discourse.mc-stan.org/t/planning-the-2-40-release/41502>\
**Category:** Developers\
**Created:** [August 10, 2026, 4:06pm UTC](https://discourse.mc-stan.org/t/planning-the-2-40-release/41502 "2026-08-10T16:06:20Z")\
**Posts on this page:** 8\
**Page:** 1

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**Author:** ![WardBrian](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mc-stan.org/wardbrian/32/12078_2.png) [@WardBrian](https://discourse.mc-stan.org/u/WardBrian)\
**Post date:** [August 10, 2026, 4:06pm UTC](https://discourse.mc-stan.org/t/planning-the-2-40-release/41502/1 "2026-08-10T16:06:20Z")

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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](https://github.com/stan-dev/design-docs/blob/master/designs/0036-stan-release-cycle.md).

cc @stevebronder @avehtari @andrjohns @Florence_Bockting

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<div class="post-metadata">

**Author:** ![WardBrian](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mc-stan.org/wardbrian/32/12078_2.png) [@WardBrian](https://discourse.mc-stan.org/u/WardBrian)\
**Post date:** [August 10, 2026, 4:56pm UTC](https://discourse.mc-stan.org/t/planning-the-2-40-release/41502/2 "2026-08-10T16:56:20Z")

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

- [Replace `Base` with Stdlib and custom shims by WardBrian · Pull Request #1655 · stan-dev/stanc3 · GitHub](https://github.com/stan-dev/stanc3/pull/1655)

Merged before the freeze. [Add map-like helpers by florence-bockting · Pull Request #3346 · stan-dev/math · GitHub](https://github.com/stan-dev/math/pull/3346) and [Fix wiener\_lpdf derivative with respect to w by martonaronvarga · Pull Request #3324 · stan-dev/math · GitHub](https://github.com/stan-dev/math/pull/3324) would be nice as well

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**Author:** ![avehtari](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mc-stan.org/avehtari/32/5935_2.png) [@avehtari](https://discourse.mc-stan.org/u/avehtari)\
**Post date:** [August 10, 2026, 5:21pm UTC](https://discourse.mc-stan.org/t/planning-the-2-40-release/41502/3 "2026-08-10T17:21:58Z")

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- 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](https://github.com/stan-dev/stan/issues/3401) (I have a working draft PR for this), and one other bug for which I’ll submit the issue and PR tomorrow

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**Author:** ![Yingnan\_Gao](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mc-stan.org/yingnan_gao/32/21198_2.png) [@Yingnan\_Gao](https://discourse.mc-stan.org/u/Yingnan_Gao)\
**Post date:** [August 17, 2026, 3:45am UTC](https://discourse.mc-stan.org/t/planning-the-2-40-release/41502/4 "2026-08-17T03:45:25Z")

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Hello, I am curious if the multi-thread tuple issue mentioned [here](https://github.com/stan-dev/cmdstan/issues/1343) will be addressed in the coming release of cmdstan? (Though technically it’s the Stan Math library that needs to be updated.)

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**Author:** ![WardBrian](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mc-stan.org/wardbrian/32/12078_2.png) [@WardBrian](https://discourse.mc-stan.org/u/WardBrian)\
**Post date:** [August 17, 2026, 9:01am UTC](https://discourse.mc-stan.org/t/planning-the-2-40-release/41502/5 "2026-08-17T09:01:24Z")

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

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<div class="post-metadata">

**Author:** ![WardBrian](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mc-stan.org/wardbrian/32/12078_2.png) [@WardBrian](https://discourse.mc-stan.org/u/WardBrian)\
**Post date:** [August 31, 2026, 2:02pm UTC](https://discourse.mc-stan.org/t/planning-the-2-40-release/41502/6 "2026-08-31T14:02:25Z")

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I’ve made the tracking issue [here](https://github.com/stan-dev/cmdstan/issues/1350)

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<div class="post-metadata">

**Author:** ![WardBrian](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mc-stan.org/wardbrian/32/12078_2.png) [@WardBrian](https://discourse.mc-stan.org/u/WardBrian)\
**Post date:** [September 5, 2026, 8:36pm UTC](https://discourse.mc-stan.org/t/planning-the-2-40-release/41502/7 "2026-09-05T20:36:34Z")

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Our recent Jenkins migration is still having some kinks worked out, so I would expect a delay to this release.

Due to personal reasons, if the delay takes more than a few extra days I will need to additionally delay it until the first week of October

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<div class="post-metadata">

**Author:** ![WardBrian](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mc-stan.org/wardbrian/32/12078_2.png) [@WardBrian](https://discourse.mc-stan.org/u/WardBrian)\
**Post date:** [September 8, 2026, 8:56pm UTC](https://discourse.mc-stan.org/t/planning-the-2-40-release/41502/8 "2026-09-08T20:56:16Z")

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My plan is to create the release candidates tomorrow morning