Trusted external skill sources

A skill source is a repository — other than apache/magpie — that ships Magpie-shaped skills (and their evals and tests). This page defines how an adopter pulls a skill or whole skill-family from such a source and wires it in so it behaves exactly like an in-tree skill: same magpie--prefixed symlink relay, same override layer, same eval binding.

Per PRINCIPLES.md §13, installation is permitted only from a trusted source — one the adopter has explicitly vouched for by committing its pin (method + URL + ref + verification anchor) to the repo. A trusted install obeys the same snapshot-plus-pin discipline the framework uses for itself: a gitignored snapshot, a committed lock, a verified and deliberate fetch by the one setup skill — never a git submodule, and never an unpinned or unverified auto-fetch. The full rationale and threat model are in RFC-AI-0006.

The trust model — three layers

Trust is layered so an organization can curate candidate sources while the adopter keeps the final say. Nothing is fetched until the adopter opts in.

Layer	File	Home	Role
Discovery	`registry.md`	in-tree	The framework’s index of known sources — curated and community. Editorial only; lists a source, never installs it.
Org-curated	`organizations/<org>/skill-sources.md`	in-tree (or adopter-local org override)	An organization vouches for a set of sources its projects may draw from. Inherited by naming `organization: <org>`. Still not an install.
Adopter opt-in	`<project-config>/skill-sources.md`	committed in the adopter repo	The install gate. The adopter lists the source ids it trusts and commits each pin. Only sources listed here are ever fetched.

An adopter may trust a source their org did not curate (list it directly with a full descriptor), or decline one the org did. The org layer is a convenience default, never a mandate — the same project → organization → framework precedence the rest of the config model uses (see AGENTS.md).

Source descriptor

A descriptor identifies one source and enumerates what it provides. It appears in the org-curated file and/or the adopter opt-in file; the registry links to the canonical one. Fields reuse the install-method and lock vocabulary the framework snapshot already uses, so resolution is mechanical.

id: <source-id>                 # unique, kebab-case — the handle pointers reference
organization: <org>             # owning org; must name a directory under organizations/
name: "<human-readable name>"
maintainer: "<who — handle / team / org>"
method: <git-tag | git-branch | svn-zip>   # same three install methods as the framework
url: <git repo URL | svn/dist archive URL>
ref: <tag | branch | version>
# Verification anchor — the re-fetch guard, per method:
#   git-tag : commit: <SHA the tag resolved to>
#   svn-zip : sha512: <released archive SHA-512>
#   git-branch has no cryptographic anchor — it tracks the branch tip
layout:                         # where things live inside the source repo
  skills_root: skills           # default: skills
  evals_root: tools/skill-evals/evals   # default: tools/skill-evals/evals
provides:
  - skill: <name>               # one unprefixed skill directory name
  - family: <prefix>-*          # or a family prefix — pulls every skill matching it

method, url, ref, and the per-method anchor are exactly the keys the framework’s own .apache-magpie.lock carries; svn-zip is the only method with cryptographic verification (SHA-512 + optional GPG against the source’s KEYS), git-tag pins a resolved commit, and git-branch tracks a tip (WIP only, no frozen anchor).

Pointer file — the redirect

Where a skill directory would sit, a pointer file names its source. It is the “redirect link”: the skill body, evals, and tests are not committed here — they are fetched into the gitignored snapshot at adopt/upgrade time. The file is skills/<name>/source.md (deliberately not SKILL.md, so the skill validator’s SKILL.md-gated checks do not fire on a stub).

---
source: <source-id>            # references a descriptor above
organization: <org>            # must name a directory under organizations/
skill_path: skills/<name>      # subpath of the skill within the source repo
evals_path: tools/skill-evals/evals/<name>   # subpath of its eval suite
---

<!-- SPDX-License-Identifier: Apache-2.0 -->

# <name> — redirect to a trusted external source

This skill is provided by the trusted external source `<source-id>`
(`organization: <org>`). Its `SKILL.md`, eval suite, and tests are fetched
into the gitignored snapshot at `.apache-magpie-sources/<source-id>/` by
`/magpie-setup` and symlinked in exactly like an in-tree skill. This file
is a pointer only — do not add skill logic here; contribute it to the
source repo instead.

source: is already an allowed optional key in the skill validator’s frontmatter set, so nothing about the pointer is a special case for the common-path validation — only the additional pointer-specific checks in the validator apply (the source: resolves to a known descriptor; the organization: is a known org; the directory draws no eval-coverage advisory because its evals are external).

How a trusted skill is installed

The setup skill drives the fetch — the skill-sources sub-action (/magpie-setup skill-sources). In outline:

Read <project-config>/skill-sources.md — the trust list. Sources not listed there are never fetched.
For each trusted source, fetch + verify into .apache-magpie-sources/<source-id>/ (gitignored) reusing the framework install recipes verbatim — git clone --depth=1 --branch <ref> for git methods; download + sha512sum -c + optional gpg --verify for svn-zip.
Record the pins: committed .apache-magpie.sources.lock (per-source method/url/ref + anchor) and gitignored .apache-magpie.sources.local.lock (what this machine fetched + when) — the same two-lock drift model as the framework snapshot.
For each provided skill, create the canonical + relay symlinks (.agents/skills/magpie-<name> → ../../.apache-magpie-sources/<id>/skills/<name>/, with per-agent relays back through the canonical entry) — identical to how framework-family skills are wired.

Drift detection, upgrade, and verify extend to the source locks: a committed-vs-local mismatch surfaces the gap and proposes /magpie-setup upgrade, which re-fetches per the committed pins.

Layout contract — skills, evals, tests

A skill’s eval suite lives outside its directory, at tools/skill-evals/evals/<name>/, bound to the skill by directory name and a repo-relative skill_md: path in each step’s fixtures/step-config.json (see tools/skill-evals/README.md). For that binding to resolve after a fetch, a source repo must keep the same two-tree layout the framework uses — skills/<name>/ for the body and tools/skill-evals/evals/<name>/ for the evals — declared via the descriptor’s layout: block. Fetching a source pulls both trees plus any tool tests/ the skill depends on, so the pulled skill is testable and eval-able exactly as it is in its home repo.

Security model

Adopter-vouched, always. The <project-config>/skill-sources.md trust list is the only thing that authorizes a fetch. An org curating a source, or the registry listing one, never triggers an install.
Pinned + verified. Every trusted source carries a pin with a verification anchor (commit / sha512). git-branch (tip-tracking, no anchor) is WIP-only, exactly as for the framework snapshot.
Untrusted stays discovery-only. The registry and org curation are editorial pointers for humans to evaluate — not supply-chain hooks.
External content is data. Skills pulled from a source are still subject to the framework’s injection-guard discipline; a fetched skill is reviewed like any other before it runs.

The full threat model (source-repo compromise, eval provenance, unpinned fetch) is in RFC-AI-0006.

Discovery index

The known sources — framework-curated and community-maintained — are listed in registry.md. Listing is editorial discovery only; it makes no guarantee and triggers no install.