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:

Package	Role
python >= 3.12	Runtime
conda >= 25.1	Package manager
conda-rattler-solver	Rust-based solver (replaces libmamba)
conda-spawn	Subprocess-based environment activation
conda-pypi	PyPI interoperability
conda-self	Base environment self-management

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

Homebrew (recommended)

The easiest way to install on macOS and Linux:

brew tap jezdez/conda-express https://github.com/jezdez/conda-express
brew install jezdez/conda-express/cx

Update later with brew upgrade cx.

Shell script

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 script 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:

Platform	File
Linux x86_64	cx-x86_64-unknown-linux-gnu
Linux ARM64	cx-aarch64-unknown-linux-gnu
macOS x86_64 (Intel)	cx-x86_64-apple-darwin
macOS ARM64 (Apple Silicon)	cx-aarch64-apple-darwin
Windows x86_64	cx-x86_64-pc-windows-msvc.exe

Each file has a matching .sha256 checksum.

Docker

A minimal, hardened multi-arch image (~37 MB) is published to GHCR on every release:

docker run --rm -v cx-data:/home/nonroot/.cx ghcr.io/jezdez/conda-express bootstrap

The image runs as non-root (uid 65532), works with --read-only, and includes provenance attestations and SBOMs. Docker Desktop on macOS and Windows automatically selects the right architecture (linux/amd64 or linux/arm64).

# Run conda commands through cx
docker run --rm -v cx-data:/home/nonroot/.cx ghcr.io/jezdez/conda-express create -n myenv python=3.12

Use as a container in CI (GitHub Actions):

jobs:
  test:
    container: ghcr.io/jezdez/conda-express:latest
    steps:
      - run: cx bootstrap && cx create -n test python numpy

Use as a base for multi-stage application builds:

FROM ghcr.io/jezdez/conda-express:latest AS conda-builder
RUN cx bootstrap && cx create -n app python numpy pandas
FROM gcr.io/distroless/cc-debian12:nonroot
COPY --from=conda-builder /home/nonroot/.cx/envs/app /opt/conda

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. You can also override these values at build time using environment variables — see Building custom cx binaries below.

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 uninstall [OPTIONS]           Remove cx, conda prefix, and all environments
  --prefix DIR                   Target directory (default: ~/.cx)
  -y, --yes                      Skip confirmation prompt

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:

Command	Instead
conda activate / deactivate	cx shell myenv
conda init	Add condabin to your PATH (see below)

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).

Building custom cx binaries

You can build a cx binary with your own set of packages using the composite GitHub Action or the reusable workflow.

Composite action (uses: jezdez/conda-express@main)

Use in a step within your own workflow. You control the platform matrix:

jobs:
  build:
    strategy:
      matrix:
        os: [ubuntu-latest, macos-latest, windows-latest]
    runs-on: ${{ matrix.os }}
    steps:
      - uses: jezdez/conda-express@main
        id: cx
        with:
          packages: "python >=3.12, conda >=25.1, conda-rattler-solver, conda-spawn, numpy, pandas"

      - uses: actions/upload-artifact@v4
        with:
          name: ${{ steps.cx.outputs.asset-name }}
          path: ${{ steps.cx.outputs.binary-path }}

Reusable workflow

Builds all 5 platforms in one call:

jobs:
  build-cx:
    uses: jezdez/conda-express/.github/workflows/build.yml@main
    with:
      packages: "python >=3.12, conda >=25.1, conda-rattler-solver, conda-spawn, numpy, pandas"

Build-time environment variables

When building from source, you can override the package configuration without editing pixi.toml:

Variable	Overrides	Format
CX_PACKAGES	[tool.cx].packages	Comma-separated match specs
CX_CHANNELS	[tool.cx].channels	Comma-separated channel names
CX_EXCLUDE	[tool.cx].exclude	Comma-separated package names

CX_PACKAGES="python >=3.12, conda >=25.1, numpy" pixi run build

Uninstalling

To completely remove cx, the conda prefix, all environments, and the cx binary:

cx uninstall

This will show what will be removed and ask for confirmation. Use --yes to skip the prompt. The command also cleans up PATH entries from shell profiles that were added by the installer.

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.