conda-express (cx)

A lightweight, single-binary bootstrapper for conda, powered by rattler. The cx binary is short for conda express.

cx replaces the miniconda/constructor installation pattern with a ~17 MB static binary that bootstraps a fully functional conda environment in seconds.

Quick start

# Bootstrap a conda installation (first run only, ~3–5 s)
cx bootstrap

# Use conda normally — cx delegates transparently
cx install -n myenv numpy pandas
cx create -n science python=3.12 scipy

# Activate environments using conda-spawn (no shell init needed)
cx shell myenv

On first use, cx automatically installs conda and its plugins into ~/.cx from an embedded lockfile. Subsequent invocations hand off directly to the installed conda binary with no overhead.

What gets installed

cx installs a minimal conda stack from conda-forge:

The conda-libmamba-solver and its 27 exclusive native dependencies (libsolv, libarchive, libcurl, spdlog, etc.) are excluded by default, reducing the install from 113 to 86 packages.

Installation

Installer script (recommended)

macOS / Linux:

curl -fsSL https://jezdez.github.io/conda-express/get-cx.sh | sh

Windows (PowerShell):

powershell -ExecutionPolicy ByPass -c "irm https://jezdez.github.io/conda-express/get-cx.ps1 | iex"

The installer detects your platform, downloads the right binary, verifies the checksum, updates your shell profile / PATH, and runs cx bootstrap. Customize with environment variables:

• CX_INSTALL_DIR — where to place the binary (default: ~/.local/bin or %USERPROFILE%\.local\bin)
• CX_VERSION — specific version to install (default: latest)
• CX_NO_PATH_UPDATE — set to skip shell profile / PATH modification
• CX_NO_BOOTSTRAP — set to skip running cx bootstrap

From GitHub Releases

Download the binary for your platform from the latest release:

Each file has a matching .sha256 checksum.

From PyPI

pip install conda-express

From crates.io

cargo install conda-express

The package is published as conda-express on PyPI and crates.io.

Building from source

Requires pixi (recommended) or Rust (edition 2024).

With pixi (recommended)

pixi manages the Rust toolchain from conda-forge for reproducible builds:

git clone https://github.com/jezdez/conda-express.git
cd conda-express

pixi run build          # cargo build --release
pixi run test           # cargo test
pixi run lint           # fmt-check + clippy

With system Rust

git clone https://github.com/jezdez/conda-express.git
cd conda-express

# Build (first build solves packages at compile time — needs network)
cargo build --release

# Binary is at target/release/cx
./target/release/cx --help

The first build runs a compile-time solve via build.rs, generating a rattler-lock v6 lockfile that gets embedded into the binary. Subsequent builds reuse the cached lockfile unless pixi.toml changes.

Configuration

Package specs, channels, and exclusions live in the [tool.cx] section of pixi.toml:

[tool.cx]
channels = ["conda-forge"]
packages = [
    "python >=3.12",
    "conda >=25.1",
    "conda-rattler-solver",
    "conda-spawn",
    "conda-pypi",
    "conda-self",
]
exclude = ["conda-libmamba-solver"]

Edit this section to customize what cx installs, then rebuild.

CLI reference

cx bootstrap [OPTIONS]           Bootstrap a fresh conda installation
  --force                        Re-bootstrap even if prefix exists
  --prefix DIR                   Target directory (default: ~/.cx)
  --channel CH                   Channels (default: conda-forge)
  --package PKG                  Additional packages to install
  --exclude PKG                  Packages to exclude (default: conda-libmamba-solver)
  --no-exclude                   Disable default exclusions
  --no-lock                      Ignore embedded lockfile, do a live solve
  --lockfile PATH                Use an external lockfile instead

cx status [--prefix DIR]         Show cx installation status
cx shell [ENV]                   Alias for conda spawn (activate via subshell)
cx help                          Getting-started guide
cx <conda-args>                  Passed through to conda

Disabled commands

cx uses conda-spawn instead of traditional shell-based activation. The following commands are intentionally disabled:

Frozen base prefix

The ~/.cx prefix is protected with a CEP 22 frozen marker after bootstrap. This prevents accidental modification of the base environment (e.g., conda install numpy into base). Users should create named environments for their work:

cx create -n myenv numpy pandas
cx shell myenv

Updating the base installation is handled by conda self update (via conda-self).

How it works

1. Compile time: build.rs reads [tool.cx] from pixi.toml, solves dependencies using rattler, filters excluded packages, and writes a rattler-lock v6 lockfile embedded into the binary.

2. First run: cx parses the embedded lockfile, downloads packages from conda-forge, and installs them into the prefix. No repodata fetch or solve needed at runtime.

3. Subsequent runs: cx detects the existing prefix and replaces its own process with the installed conda binary, passing all arguments through.

Activation model

cx ships with conda-spawn instead of traditional conda activate. There is no need to run conda init or modify shell profiles.

# Add cx to PATH (one-time setup)
export PATH="$HOME/.cx/condabin:$PATH"

# Activate an environment (spawns a subshell)
cx shell myenv

# Deactivate by exiting the subshell
exit

Lockfile format

The embedded lockfile uses the rattler-lock v6 format (same as pixi.lock). It can be:

• Read by pixi
• Imported by conda-lockfiles
• Checked into version control for reproducibility auditing

License

BSD 3-Clause. See LICENSE.