hermes - 💡(How to fix) Fix [Feature]: nix package should support source patching [1 comments, 1 participants]

Feature Description

The nix package (nix/packages.nix) uses dontUnpack = true; dontBuild = true; — it's a wrapper that copies bundled skills and creates makeWrapper entries around hermesVenv binaries. The Python source (tools/, run_agent.py, etc.) lives inside hermesVenv, built by python.nix via pythonSet.mkVirtualEnv.

This makes it impossible for downstream consumers to apply patches to the Python source via overrideAttrs + patches — there's no source to patch since patchPhase is skipped.

Use Case

Consumer flakes that follows hermes-agent need to apply unmerged bugfix PRs (e.g. #13567) to the Python source. Currently the only option is maintaining a fork branch, which doesn't scale when carrying multiple unrelated patches.

Proposed Approach

Expose a sourcePatches argument (or similar) in python.nix / packages.nix that applies patches to the workspace source before the uv2nix venv build. For example:

# python.nix
{ python312, lib, callPackage, uv2nix, pyproject-nix, pyproject-build-systems, stdenv,
  sourcePatches ? [],  # ← new
}:
let
  patchedSource = if sourcePatches == [] then ./.. else
    pkgs.applyPatches { src = ./..; patches = sourcePatches; };
  workspace = uv2nix.lib.workspace.loadWorkspace { workspaceRoot = patchedSource; };
  ...

Then in packages.nix, pass it through:

hermesVenv = pkgs.callPackage ./python.nix {
  inherit (inputs) uv2nix pyproject-nix pyproject-build-systems;
  sourcePatches = cfg.sourcePatches or [];
};

Alternatives Considered

• Fork branch: works but doesn't scale with multiple patches and requires constant rebasing.
• postInstall patching on the wrapper: only works for bundled skills in $out/share/hermes-agent/skills/, not for Python source in the venv.
• python312.override { packageOverrides }: only overrides nixpkgs Python packages, not the hermes-agent workspace package itself.