---
spec: hm-module-harness-integration
blocked-by: 0046-reshape-hm-module-per-harness-toggle
---

## What to build

Add the first automated proof of the module's composition, so that a change in home-manager or the Claude Code module that breaks the way the Skill is declared fails `nix flake check` rather than a maintainer rebuild weeks later.

A home-manager input is added to the flake, with its own nixpkgs following the flake's nixpkgs, so the module is checked against the same nixpkgs-and-home-manager pairing a consumer following this flake would get.

A flake check evaluates the actual module through home-manager's standalone configuration entry point and builds the resulting home files derivation under several configurations, asserting on the tree it produces.
Building the home files derivation is sufficient — it is the file-linkage layer that actually decides whether two declarations collide — and needs neither the Claude Code binary nor a running agent.
The check asserts on which files a generation contains, never on module internals (option values, store paths, the shape of the file mechanism).

The configurations exercised:

- An operator declaring their own skills as an attribute set: the module's Skill lands alongside the operator's, each at its own name.
- An operator declaring their own skills as a whole directory (path form): the module's Skill lands alongside the operator's directory contents.
  This is the case that guards the recursive-install coupling; a regression to a non-recursive path-form install fails here as a build-time file collision.
- Claude Code disabled: no gitea-axi Skill entry is written.
  This guards the explicit sibling-enable gate introduced in the reshape.
- The hook merges into an operator's own SessionStart hook list rather than replacing it.

This adds a module check alongside the existing package check in the flake's `checks` output rather than introducing a new kind of verification surface.

## Acceptance criteria

- [ ] The flake has a home-manager input whose nixpkgs follows the flake's nixpkgs; `flake.lock` is updated.
- [ ] A new check under the flake's `checks` output evaluates the real module through home-manager's standalone configuration entry point and builds the home files derivation — no Claude Code binary or running agent required.
- [ ] The attribute-set-skills configuration asserts the module's Skill and the operator's skill both land, each at its own name.
- [ ] The whole-directory-skills (path form) configuration asserts the module's Skill lands alongside the operator's directory contents; a non-recursive path-form install would fail this as a build-time collision.
- [ ] The Claude-Code-disabled configuration asserts no gitea-axi Skill entry is written.
- [ ] A configuration with an operator's own SessionStart hook asserts the module's hook merges into that list rather than replacing it.
- [ ] The check asserts on the generation's file tree only, not on option values or store paths.
- [ ] `nix flake check` runs the new check across the flake's systems and passes.