Features#

Single-binary bootstrapper#

cx is a single ~17 MB static binary written in Rust. It requires no Python, no installer framework, and no shell modifications. Download it, run it, and you have a working conda installation.

Compile-time lockfile#

build.rs performs a full dependency solve at cargo build time using rattler crates, producing a rattler-lock v6 lockfile that is embedded into the binary. At runtime, bootstrap skips repodata fetching and solving entirely — it downloads and installs packages directly from the locked URLs.

This gives cx deterministic, reproducible bootstraps with ~3–5 second install times.

Package exclusion#

conda on conda-forge hard-depends on conda-libmamba-solver, which pulls in 27 native dependencies (libsolv, libarchive, libcurl, spdlog, etc.). Since cx uses conda-rattler-solver instead, these are unnecessary.

cx removes them via a post-solve transitive dependency pruning algorithm: after the solver produces a complete solution, cx identifies packages that are exclusively required by the excluded packages and removes them. This reduces the install from 113 to 86 packages.

conda-rattler-solver#

cx configures conda-rattler-solver as the default solver via .condarc. This solver is based on resolvo, the fastest SAT solver in the conda ecosystem, and ships as a pure Python package with py-rattler wheels.

conda-spawn activation#

cx ships with conda-spawn and disables traditional conda activate/deactivate/init. Instead:

cx shell myenv          # spawns a subshell with myenv activated
exit                    # leaves the environment

No .bashrc/.zshrc modifications required. Just add ~/.cx/condabin to your PATH.

`cx shell` alias#

cx shell is a convenience alias for conda spawn. It works identically:

cx shell myenv          # same as: conda spawn myenv

Frozen base prefix (CEP 22)#

After bootstrap, cx writes a conda-meta/frozen marker file per CEP 22. This protects the base prefix from accidental modification. Users should create named environments for their work:

cx create -n myenv numpy pandas
cx shell myenv

Auto-bootstrap#

If the prefix doesn’t exist when you run a conda command, cx automatically bootstraps before executing:

# First time: bootstraps ~/.cx, then creates the environment
cx create -n myenv python=3.12

External lockfile support#

For custom deployments, you can override the embedded lockfile:

cx bootstrap --lockfile /path/to/custom.lock

Or skip the lockfile entirely for a live solve:

cx bootstrap --no-lock

Uninstall (`cx uninstall`)#

cx provides a clean uninstall command that reverses the bootstrap:

cx uninstall

This will:

List what will be removed (prefix, named environments, cx binary)
Ask for confirmation (--yes to skip)
Remove the conda prefix and all environments
Remove the cx binary
Clean up PATH entries from shell profiles

GitHub Action for custom builds#

cx ships a composite GitHub Action and a reusable workflow that let you build custom cx binaries with your own package set baked in. The build performs a full compile-time dependency solve, producing a self-contained binary with an embedded lockfile — just like the official cx releases.

This is powered by the same environment variable overrides that work locally, but wrapped in a ready-to-use Action.

See the GitHub Action reference for inputs, outputs, and behavior. For a step-by-step walkthrough, see the custom builds guide.

Multi-platform support#

cx builds and tests on 5 platforms via GitHub Actions:

Platform	Runner
linux-x64	`ubuntu-latest`
linux-aarch64	`ubuntu-24.04-arm`
macos-x64	`macos-15-large`
macos-arm64	`macos-latest`
windows-x64	`windows-latest`

PyPI and crates.io distribution#

cx is published as conda-express on both PyPI and crates.io:

pip install conda-express       # from PyPI
cargo install conda-express     # from crates.io

Both use trusted publishing (OIDC) for secure, tokenless releases.