User Guide

The conda-rattler-solver plugin lets you use the solver that powers pixi, directly in conda. The solver is called resolvo, and it reaches conda through the Rust-based rattler library and its Python bindings, py-rattler.

Environments solve meaningfully faster with rattler, especially large or complex ones, and your existing environments and workflows keep working.

Project status

conda-rattler-solver is in beta. Opt in to test it and send us your feedback, but it is not yet recommended for production use.

How to install

conda-rattler-solver requires conda 26.7 or later. If you have an older conda, we simply recommend updating conda to a more recent version first:

$ conda update -n base conda

Then install the package in your base environment:

$ conda install -n base conda-rattler-solver

Development builds are published to the conda-canary channel under the dev label:

$ conda install -n base conda-canary/label/dev::conda-rattler-solver

Usage

Try it on a single command

The --solver flag is available for conda create, conda install, conda remove, and conda update, and lets you use the solver without changing your configuration:

$ conda install numpy --solver=rattler

The flag is also exposed as the CONDA_SOLVER environment variable, in case you need that:

$ CONDA_SOLVER=rattler conda install numpy

Set it as the default

To use rattler for every solve, add solver: rattler to your .condarc file, either manually or with this command:

$ conda config --set solver rattler

Switching back

If you ever need another solver temporarily, use the --solver flag:

$ conda install numpy --solver=libmamba
$ conda install numpy --solver=classic

To revert the default configuration, remove the solver key:

$ conda config --remove-key solver

conda then falls back to its own default, which is libmamba. You can also make a different choice explicit with conda config --set solver libmamba.

Tip

If you are unsure what configuration is being used by conda, you can inspect it with conda config --show-sources.