propagate

A skill that creates tests from Allium specifications, which are files describing software behaviour. It connects the described behaviours to the project code and test conventions.

In plain words
What is it for?
It is for generating ordinary, property-based, and state-machine tests from an Allium file, and checking test coverage against that specification.
Why use it?
It helps ensure that each behaviour in a specification has a corresponding test. It can also reveal specification obligations that are not covered.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/juxt/allium/propagate
Any agent
npx skills add juxt/allium --skill propagate
Clone the repo
git clone --depth 1 https://github.com/juxt/allium

Made for: Claude Code, Codex.

Per session 57 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,443 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00057 $0.04443
Opus 5 $0.00028 $0.02221
Sonnet 5 $0.00011 $0.00889
Haiku 4.5 $0.00006 $0.00444

Measured 2d ago against content hash 5e2d88808bd9, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

propagate scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

  • propagate — 100% identical, 0 lines differ
skills/propagate/SKILL.md · 274 lines

How it starts

The opening of the file, as written. The whole thing — 274 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Propagation

This skill generates tests from Allium specifications. Propagation is how plants reproduce from cuttings of the parent: the spec is the parent, the tests are the offspring.

Deterministic tools guarantee completeness (every spec construct maps to a test obligation). You handle the implementation bridge: correlating spec constructs with code, generating tests in the project's conventions.

Interaction modes

This skill runs in two modes. Every instruction below that asks or suggests something to the user follows the mode:

  • Interactive — running inline in a conversation. Ask the user directly and wait for the answer.
  • Non-interactive — running as the propagate subagent (for example inside the Allium loop), where no user is reachable. Report anything that needs a human decision — a spec too coarse to propagate, an ambiguous implementation bridge, uncovered obligations — in your final output and continue with the work that does not depend on it.

Prerequisites

Before propagating tests, you need:

  1. An Allium spec — the .allium file describing the system's behaviour
  2. A target codebase — the implementation to test
  3. Test obligations — from allium plan <spec> (JSON listing every required test)
  4. Domain model — from allium model <spec> (JSON describing entity shapes, constraints, state machines)

If the CLI tools are not available, derive test obligations manually from the spec using the test-generation taxonomy in references/test-generation.md.

Modes

Surface mode

Generates boundary tests from surface declarations. Use when the user wants to test an API, UI contract or integration boundary.

For each surface in the spec:

  1. Exposure tests — verify each item in exposes is accessible to the specified actor, including for iteration over collections
  2. Provides tests — verify operations appear when their when conditions are true and are hidden otherwise, including when the corresponding rule's requires clauses are not met
  3. Actor restriction tests — verify the surface is not accessible to other actor types
  4. Actor identification tests — verify only entities matching the actor's identified_by predicate can interact; for actors with within, verify interaction is scoped to the declared context
  5. Context scoping tests — verify the surface instance is absent when no entity matches the context predicate
  6. Contract obligation tests — verify demands are satisfied by the counterpart, fulfils are supplied by this surface, including all typed signatures
  7. Guarantee tests — verify @guarantee annotations hold across the boundary
  8. Timeout tests — verify referenced temporal rules fire within the surface's context
  9. Related navigation tests — verify navigation to related surfaces resolves to the correct context entity

Read the full file on GitHub · 274 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 274 lines · 57 tokens per session scan A 5e2d88808bd9

Subscribe to this mod's changes

propagate is a skill published in the GitHub repository juxt/allium (478 stars, last pushed 6d ago), licensed MIT. It adds 57 tokens to every session and 4,443 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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