pact-engineer

pact-engineer is a skill for Claude Code, Codex from jmcentire/pact. It costs 88 tokens per session (1,209 once invoked), scanned A, original, MIT.

A plan-first workflow that uses Pact as a contract and testing engine for software changes. It helps define the problem, constraints, architecture, contracts, and tests before implementation.

In plain words
What is it for?
Use it for substantial features, architecture changes, risky fixes, or tasks that need a written plan and contract-driven tests.
Why use it?
It makes important design assumptions explicit and exposes unclear or infeasible requirements early. This gives implementation and testing a shared target.

Skill for Claude CodeCodex

Part of the pact plugin — 2 skills, 1 command shipped together

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/jmcentire/pact/pact-engineer
Any agent
npx skills add jmcentire/pact --skill pact-engineer
Clone the repo
git clone --depth 1 https://github.com/jmcentire/pact

Made for: Claude Code, Codex.

Or install pact, the plugin that ships this one along with the rest of its 2 skills, 1 command.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for pact-engineer

README.md
[![agentmods](https://agentmods.dev/badge/skills/jmcentire/pact/pact-engineer.svg)](https://agentmods.dev/skills/jmcentire/pact/pact-engineer)
Your own site
<a href="https://agentmods.dev/skills/jmcentire/pact/pact-engineer"><img src="https://agentmods.dev/badge/skills/jmcentire/pact/pact-engineer.svg" alt="Measured on agentmods" height="20"></a>
Per session 88 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,209 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 $0.00088 $0.01209
Opus 5 $0.00044 $0.00605
Sonnet 5 $0.00018 $0.00242
Haiku 4.5 $0.00009 $0.00121

Measured 5d ago against content hash b5cae1ea1722, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

pact-engineer 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 5d 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.

skills/pact-engineer/SKILL.md · 111 lines

How it starts

The opening of the file, as written. The whole thing — 111 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Pact Engineer

Use Pact to make the implementation bet explicit before coding. Keep Pact's contracts and tests authoritative, but treat planning and implementation as a feedback loop rather than a one-way handoff.

Workflow

  1. Source ~/.profile when feasible.
  2. Start or resume a Kindex session, then search the task and affected domain.
  3. Read repository instructions and the relevant implementation, tests, and recent history before framing the change.
  4. Normalize vague task language into a concrete problem statement, boundaries, constraints, and acceptance criteria. Use Constrain artifacts when available; otherwise create equivalent prompt.md and constraints.yaml inputs.
  5. Run central architecture claims past Simulacrum before locking the frame.
  6. Run Pact in plan-only mode and advance it through interview/decomposition until it pauses after contracts and tests:
pact init "$PACT_DIR" --budget 10
pact run "$PACT_DIR" --constrain-dir "$CONSTRAIN_DIR" --plan-only --once

Answer or approve interview questions as needed, then continue pact run --once until the plan-only pause. Do not bypass unresolved ambiguity.

  1. Read design.md, .pact/decomposition/tree.json, contracts, visible tests, and generated task lists. Run pact assess on the affected source tree.
  2. Render a focused brief before implementing each component:
pact handoff "$PACT_DIR" "$COMPONENT_ID" --validate --max-tokens 2000
  1. Implement directly with the active agent. Follow the repository's existing patterns and verify incrementally.
  2. Reconcile contracts whenever implementation exposes infeasibility:
    • Stop instead of silently deviating.
    • Record the conflict and the failed assumption in Kindex.
    • Update task/constraints/contracts and regenerate affected tests or rerun Pact plan-only.
    • Resume only after the contract and implementation agree.
  3. Run repository tests, type checks, lint, pact validate, and pact audit where applicable. Then run the lean review checklist in references/lean-review.md: remove ceremony that does not improve correctness, recovery, observability, or evidence, but do not delete safety or production-readiness controls.
  4. Run post-implementation review:

Read the full file on GitHub · 111 lines

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 5d ago First seen · 111 lines · 88 tokens per session scan A b5cae1ea1722

Subscribe to this mod's changes

pact-engineer is a skill published in the GitHub repository jmcentire/pact (164 stars, last pushed 15d ago), licensed MIT. It adds 88 tokens to every session and 1,209 once invoked, about $0.0004 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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