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BridgeStan

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What BridgeStan is

BridgeStan is a free open-source library that gives higher-level languages in-memory access to methods from Stan models. It is intended for researchers and library authors developing inference algorithms for arbitrary Stan models. The interface exposes log densities, gradients, Hessians, and parameter transforms for constraining and unconstraining values. Clients are available for Python, Julia, R, and Rust, with a public C API. BridgeStan wraps the Stan Model class generated by the Stan compiler in a C-compatible layer. Python users can provide model data as a JSON string, JSON file path, or dictionary converted to JSON; the package requires Python 3.9 or later and NumPy. Hessians use central finite differences by default, with nested autodiff available at compile time for supported models. Source archives and repository downloads are available. Building requires a C++ toolchain and GNU Make; Stan requires C++14, and Windows uses mingw32-make because Microsoft’s compiler is unsupported. Threaded and non-threaded model builds must not be mixed in one process.

Who it suits

BridgeStan suits researchers and library authors writing inference algorithms around Stan models. It fits developers working in Python, Julia, R, Rust, or through the C API.

What it does well

Exposes densities, gradients, Hessians, and transforms
Clients for Python, Julia, R, and Rust
Public C API available
JSON model-data options in Python
Free open-source library

What to know first

Requires a C++ toolchain and make utility
Python package requires Python 3.9 or newer
Microsoft’s Windows compiler is unsupported
Mixed threading builds may cause crashes

Limits

The library is free, but building requires the listed compiler and make utilities. Python requires Python 3.9 or newer and NumPy, while Hessians use finite differences by default unless nested autodiff is enabled at compile time.

Plans

Plan	Billed and limits	Price
BridgeStan	Open source library; requires a C++14 compiler and make utility	Free

As roualdes.us lists them, read 8 Oct 2026. The maker's own page has the final word.

Getting started

Download a released source archive or clone the repository from GitHub
Install a C++14 compiler and GNU Make, or mingw32-make on Windows
Install Python 3.9 or newer and NumPy for the Python interface
Install the Python package bridgestan from PyPI when using Python
Compile models with compatible STAN_THREADS settings within each process

Verdict

BridgeStan provides a language-neutral interface to core Stan model methods for custom inference work. Its build prerequisites and threading restriction matter when planning deployments.

Questions

How much does BridgeStan cost?

BridgeStan is free and has a free plan priced at 0.00 USD.

Which languages can use BridgeStan?

Language clients are available for Python, Julia, R, and Rust, and a public C API is provided.

What data formats does the Python interface accept?

It accepts a JSON string, a JSON file path, or a dictionary converted to JSON.

What does installation require?

The source build requires a C++ toolchain and GNU Make. Stan requires C++14; Windows uses mingw32-make and does not support Microsoft's compiler.

Where is the Python package distributed?

The Python interface is available on PyPI as bridgestan and requires Python 3.9 or later plus NumPy.

Facts from BridgeStan's own pages

Bayesian analysis: Yes · roualdes.us, 24 Sept 2026
Build requirements: Stan requires a C++14 compiler and GNU make on Unix-like systems or mingw32-make on Windows; Microsoft's compiler is unsupported on Windows. · roualdes.us, 8 Oct 2026
Customization: Compiler flags can be customized through make options or the make/local file, including optimization and Stan compiler flags. · roualdes.us, 8 Oct 2026
Data import formats: JSON · roualdes.us, 24 Sept 2026
Deployment: desktop · roualdes.us, 24 Sept 2026
Distribution: The source repository and released archives are available for download, and language packages can download BridgeStan sources when compiling a model. · roualdes.us, 8 Oct 2026
Free plan: Yes · roualdes.us, 24 Sept 2026
Hessian behavior: Hessians use central finite differences by default; nested autodiff can be enabled at compile time for models that support it. · roualdes.us, 8 Oct 2026
Installation: BridgeStan can be downloaded as a released source archive or cloned from GitHub, and requires a C++ toolchain and GNU Make. · roualdes.us, 8 Oct 2026
Intended users: The documentation describes researchers and library authors developing inference algorithms for arbitrary Stan models as its intended users. · roualdes.us, 8 Oct 2026
Language interfaces: BridgeStan has clients for Python, Julia, R, and Rust, plus a public C API. · roualdes.us, 8 Oct 2026
Model data: The Python interface accepts model data as a JSON string, a JSON file path, or a dictionary converted to JSON. · roualdes.us, 8 Oct 2026
Model methods: Its model interface exposes log densities, gradients, Hessians, and parameter constraining and unconstraining transforms. · roualdes.us, 8 Oct 2026
Parallelism: Threaded calls require enabling STAN_THREADS, and models with and without that setting should not be mixed in one process because this may cause crashes. · roualdes.us, 8 Oct 2026
Purpose: BridgeStan provides in-memory access to methods of Stan models for building inference algorithms in higher-level languages. · roualdes.us, 8 Oct 2026
Python package: The Python interface is available from PyPI as bridgestan and requires Python 3.9 or later and NumPy. · roualdes.us, 8 Oct 2026
Python requirements: The Python package requires Python 3.9 or newer and NumPy, and the system prerequisites still need to be installed separately. · roualdes.us, 8 Oct 2026
R distribution: BridgeStan is not available on CRAN but is mirrored by R-Multiverse and can also be installed from GitHub. · roualdes.us, 8 Oct 2026
Regression models: No · roualdes.us, 24 Sept 2026
Scripting support: Yes · roualdes.us, 24 Sept 2026
Security and compliance: The opened official documentation and repository pages do not state security certifications or compliance claims. · roualdes.us, 8 Oct 2026
Stan integration: BridgeStan works with Stan models, including models such as those in posteriordb. · roualdes.us, 8 Oct 2026
Statistical tests: No · roualdes.us, 24 Sept 2026
Support: The documentation links to Stan Forums and says contributions are welcome when language bindings lack desired features. · roualdes.us, 8 Oct 2026

Where BridgeStan stands on Freedom251

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