By name: devenv-init description: > Use when initializing a new project with devenv, direnv, and jj version control. Triggers on: setting up dev environment, configuring nix shell, project bootstrap.
Initialize Devenv + Direnv + JJ
Overview
Bootstrap a development environment with jj (git-backed), devenv (nix-based tools), and direnv (auto-activation). Idempotent - safe to run multiple times to update configuration.
Quick Start
bash .claude/skills/devenv-init/setup-devenv.sh # Full setup
bash .claude/skills/devenv-init/setup-devenv.sh --force # Regenerate devenv.nix
bash .claude/skills/devenv-init/setup-devenv.sh --analyze # Analyze only
What It Does
- Ensures jj repo - Initializes if git exists but jj doesn't
- Warns on missing remotes - Continues anyway
- Analyzes repo - Detects language, tools, scripts, tasks
- Creates/updates .envrc - Works with OR without devenv
- Generates devenv.nix - With detected configuration
- Creates devenv.yaml - Nixpkgs input
Auto-Detection
| Detected | Source | Generated Config |
|---|---|---|
| Rust | Cargo.toml | languages.rust, cargo-watch, rustfmt/clippy hooks |
| Python | pyproject.toml | languages.python, ruff, uv, pytest |
| Node | package.json | languages.javascript, pnpm/yarn, scripts from package.json |
| Go | go.mod | languages.go, golangci-lint, gofmt hook |
| Tools | Makefile, justfile | packages (gnumake, just) |
Idempotency
| File | Behavior on Re-run |
|---|---|
| .envrc | Updates if managed, backs up if not |
| devenv.nix | Skips unless --force, backs up if unmanaged |
| devenv.yaml | Skips if exists |
| .jj | Initializes only if missing |
Files managed by this skill contain a marker comment. Unmanaged files are backed up before overwriting.
Options
--force, -f Regenerate devenv.nix even if already managed
--analyze, -a Only analyze repo, show recommendations, don't write
--help, -h Show help
Generated Sections
| Section | Auto-populated From |
|---|---|
| packages | Detected tools (cargo-watch, ruff, pnpm, etc) |
| scripts | Common dev commands (check, lint, test, dev) |
| tasks | Build/test commands for devenv tasks run |
| processes | Dev servers from package.json scripts |
| pre-commit.hooks | Language-appropriate formatters/linters |
.envrc Behavior
The generated .envrc gracefully handles:
- devenv installed: Full devenv shell activation
- nix only: Falls back to
use_nix - Neither: Succeeds silently (no-op)
Querying Devenv Options
Use devenv-query.sh to explore available options without loading full docs:
# List all available languages
bash .claude/skills/devenv-init/devenv-query.sh langs
# List all available services
bash .claude/skills/devenv-init/devenv-query.sh services
# Search options for a specific feature
bash .claude/skills/devenv-init/devenv-query.sh options languages.rust
bash .claude/skills/devenv-init/devenv-query.sh options services.postgres
# Search nixpkgs for packages
bash .claude/skills/devenv-init/devenv-query.sh packages ripgrep
# Evaluate current devenv.nix config (returns JSON)
bash .claude/skills/devenv-init/devenv-query.sh eval languages.rust.enable
Results are cached for 24h in ~/.cache/devenv-init/.
Troubleshooting
| Issue | Fix |
|---|---|
| "No git or jj repository" | Run git init first |
| "Not git-backed" | Run jj git init --colocate |
| Want to regenerate | Run with --force |
| Wrong detection | Edit devenv.nix manually, it won't be overwritten |
| Need option details | Run devenv-query.sh options <path> |