nix

Parse the first argument to dispatch:

• No arguments → print this skill's usage summary and stop.
• build → go to Build.
• run → go to Run.
• status → run $CLAUDE_ARCS_ROOT/tools/nix-status.sh synchronously and report the output.
• Anything else → treat as a build output name (shorthand for build <arg>).

Build

Spawn a background Agent with the following prompt, substituting $COMMAND:

• /nix build → $COMMAND = nix build --print-build-logs
• /nix build foo → $COMMAND = nix build .#foo --print-build-logs

Run this nix build command:

    $COMMAND

Read the ENTIRE output before any analysis.

If the build SUCCEEDS: report the output name and that it succeeded.

If the build FAILS, apply these heuristics in order:

1. Read the full log. The error is rarely the last line. Scroll up to the first failure.
2. Suspect the hash before the change. If the build doesn't reflect the edit, the source hash is stale. Check that files are git-added (flakes only see tracked files).
3. Remember the daemon boundary. Builds run under nix-daemon, not your shell. Environment variables, PATH, and shell config do not carry into the build sandbox.
4. Isolate the phase. Nix builds in phases (unpack, patch, configure, build, install, check). Identify which phase failed.

Report the diagnosis. Do not propose a fix — just report what failed and why.

Set run_in_background: true. After launching, inform the user and resume the prior task.

When the agent completes, relay its report.

Run

Run a flake app from the project flake:

• /nix run → nix run (default app)
• /nix run foo → nix run .#foo

Run it synchronously. After the run completes, resume the prior task.