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name: flox-environments description: "Create reproducible, cross-platform development environments with Flox — a declarative environment manager built on Nix. ALWAYS use this skill when the user needs to: set up a project with system-level dependencies (compilers, databases, native libraries like openssl, libvips, BLAS, LAPACK); configure reproducible toolchains for Python, Node.js, Rust, Go, C/C++, Java, Ruby, Elixir, PHP, or any language; manage environments that must work identically across macOS and Linux; pin exact package versions for a team; run local services (PostgreSQL, Redis, Kafka) alongside development tools; onboard new developers with a single command; or solve 'works on my machine' problems. Especially valuable for AI-assisted and vibe coding — Flox lets agents install tools into a project-scoped environment without sudo, system pollution, or sandbox restrictions, and the resulting environment is committed to the repo so anyone can reproduce it instantly. Use this skill even if the user doesn't mention Flox — if they describe needing reproducible, declarative, cross-platform dev environments with system packages, this is the right tool. Also use when the user mentions .flox/, manifest.toml, flox activate, or FloxHub." origin: Flox

Flox Environments

Flox creates reproducible development environments defined in a single TOML manifest. Every developer on the team gets identical packages, tools, and configuration — across macOS and Linux — without containers or VMs. Built on Nix with access to over 150,000 packages.

When to Activate

Use this skill when the user has an environment management problem — even if they haven't mentioned Flox. Flox is the right tool when:

• The project needs system-level packages (compilers, databases, CLI tools) alongside language-specific dependencies
• Reproducibility matters — the setup should work identically on a teammate's machine, in CI, or on a fresh laptop
• The user needs multiple tools to coexist — e.g., Python 3.11 + PostgreSQL 16 + Redis + Node.js in one environment
• Cross-platform support is needed (macOS and Linux from the same config)
• AI agents need to install tools — Flox lets agents add packages to a project-scoped environment without sudo, system pollution, or sandbox restrictions

If the user just needs a single language runtime with no system dependencies, standard tooling (nvm, pyenv, rustup alone) may suffice. If they need full OS-level isolation, containers might be more appropriate. Flox sits in the sweet spot: declarative, reproducible environments without container overhead.

Prerequisite: Flox must be installed first — see flox.dev/docs for macOS, Linux, and Docker.

Core Concepts

Flox environments are defined in .flox/env/manifest.toml and activated with flox activate. The manifest declares packages, environment variables, setup hooks, and shell configuration — everything needed to reproduce the environment anywhere.

Key paths:

• .flox/env/manifest.toml — Environment definition (commit this)
• $FLOX_ENV — Runtime path to installed packages (like /usr — contains bin/, lib/, include/)
• $FLOX_ENV_CACHE — Persistent local storage for caches, venvs, data (survives rebuilds)
• $FLOX_ENV_PROJECT — Project root directory (where .flox/ lives)

Essential Commands

flox init                       # Create new environment
flox search <package> [--all]   # Search for packages
flox show <package>             # Show available versions
flox install <package>          # Add a package
flox list                       # List installed packages
flox activate                   # Enter environment
flox activate -- <cmd>          # Run a command in the environment without a subshell
flox edit                       # Edit manifest interactively

Manifest Structure

# .flox/env/manifest.toml

[install]
# Packages to install — the core of the environment
ripgrep.pkg-path = "ripgrep"
jq.pkg-path = "jq"

[vars]
# Static environment variables
DATABASE_URL = "postgres://localhost:5432/myapp"

[hook]
# Non-interactive setup scripts (run every activation)
on-activate = """
  echo "Environment ready"
"""

[profile]
# Shell functions and aliases (available in interactive shell)
common = """
  alias dev="npm run dev"
"""

[options]
# Supported platforms
systems = ["x86_64-linux", "aarch64-linux", "x86_64-darwin", "aarch64-darwin"]

Package Installation Patterns

Basic Installation

[install]
nodejs.pkg-path = "nodejs"
python.pkg-path = "python311"
rustup.pkg-path = "rustup"

Version Pinning

[install]
nodejs.pkg-path = "nodejs"
nodejs.version = "^20.0"          # Semver range: latest 20.x

postgres.pkg-path = "postgresql"
postgres.version = "16.2"         # Exact version

Platform-Specific Packages

[install]
# Linux-only tools
valgrind.pkg-path = "valgrind"
valgrind.systems =