# CmdStanR: v0.9.0 Release

**URL:** <https://discourse.mc-stan.org/t/cmdstanr-v0-9-0-release/39183>\
**Category:** Announcements\
**Created:** [March 30, 2025, 10:19am UTC](https://discourse.mc-stan.org/t/cmdstanr-v0-9-0-release/39183 "2025-03-30T10:19:56Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![andrjohns](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mc-stan.org/andrjohns/32/15297_2.png) [@andrjohns](https://discourse.mc-stan.org/u/andrjohns)\
**Post date:** [March 30, 2025, 10:19am UTC](https://discourse.mc-stan.org/t/cmdstanr-v0-9-0-release/39183/1 "2025-03-30T10:19:56Z")

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Hello all, I’m excited to announce that we have now released CmdStanR v0.9.0! This is a minor release, wrapping up several months of bugfixes, quality-of-life improvements, and updates to documentation (full release notes below)

One of the key updates for Windows users is that now the standard RTools toolchain with no additional configuration or downloads will be used for CmdStan v2.35+, for all R4.x versions.

As usual, you can install the latest release from our R-Universe:

```r
install.packages("cmdstanr", repos = c("https://stan-dev.r-universe.dev",
                                       "https://cloud.r-project.org"))

```

### Release Notes

#### General Improvements/Changes

- Added compatibility for RTools45 (#1066)
- cmdstanr will now use RTools with no additional toolchain updates needed on Windows (CmdStan 2.35+ only; #1065, #1054)
- Improve error messages when calling `sampler_diagnostics()` with `fixed_param=TRUE`
- Improve numerical stability in calculation of effective sample size during `loo` method (#1057)
- Improve numerical stablity with very small log-ratios in calculation of effective sample size during `loo` method (#1015)
- Add warning if input data/inits have been coerced to ints (#994)

#### Bugfixes

- Don’t require fixed\_param for models with zero parameters (only GQs) for CmdStan \>= 2.36 (#1046)
- Improve detection/handling of `make` (#1036)
- Fix saving of model objects to network drive (#1038, thanks to @bschneidr)
- Update usage of `untar` to fix installation errors (#1034)
- Respect compilation flags in `make/local` when exposing functions or model methods (#1003)
- Fix passing of include paths to CmdStan (#1000)
- Fix passing of factor data to CmdStan (#999)
- Fix extraction and passing of array data/parameters as model inits (#993)

#### Documentation Updates

- Clarifications to usage of `optimize` and `loo` methods (#1060)
- Add documentation for faster model saving with large models (#1042)
- Remove mentions of `rstan::read_stan_csv` due to incompatibility with newer CmdStan outputs (#1018)
- Document global option `cmdstanr_print_line_numbers` for printing line numbers (#1017)
- Change usage of ‘chapter’ to ‘section’ in documentation (#1014)
- Remove examples of updating removed array syntax as functionality no longer supported in CmdStan (#1008)
- Change usages of ‘sampling statement’ → ‘distribution statement’ (#987)

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**Author:** ![mhollanders](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mc-stan.org/mhollanders/32/17623_2.png) [@mhollanders](https://discourse.mc-stan.org/u/mhollanders)\
**Post date:** [March 30, 2025, 7:35pm UTC](https://discourse.mc-stan.org/t/cmdstanr-v0-9-0-release/39183/2 "2025-03-30T19:35:36Z")

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Congrats and thanks!