A spec-driven development workflow called Forge. It moves a change through requirements, architecture, implementation planning, and coding, with a separate command for correcting course.

Use it to specify a change, design its solution, create implementation tasks, execute the work with checks, or realign the work when plans change.

It keeps the written requirements, technical design, task plan, and implementation aligned as a change progresses.

forge — Skill for Claude Code and Codex by emiliosheinz/agent-skills

Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo

git clone --depth 1 https://github.com/emiliosheinz/agent-skills

agentmods

npx agentmods add skills/emiliosheinz/agent-skills/forge

Made for: Claude Code, Codex.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/emiliosheinz/agent-skills/forge/github.svg)](https://agentmods.dev/skills/emiliosheinz/agent-skills/forge)

Your own site

<a href="https://agentmods.dev/skills/emiliosheinz/agent-skills/forge"><img src="https://agentmods.dev/badge/skills/emiliosheinz/agent-skills/forge/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/emiliosheinz/agent-skills/forge"><img src="https://agentmods.dev/badge/skills/emiliosheinz/agent-skills/forge.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 142 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 3,197 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

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.

Model	Per session	Once invoked
Fable 5.1	$0.00142	$0.03197
Opus 5.5	$0.00057	$0.01279
Sonnet 5.5	$0.00028	$0.00639
Haiku 4.5	$0.00014	$0.00320

Measured 13d ago against content hash 00adb7f1a233, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

forge 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 13d 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.

forge/SKILL.md · 240 lines

How it starts

The opening of the file, as written. The whole thing — 240 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Forge

Forge runs spec-driven development as four phases. You invoke one phase at a time. Each phase does its work, updates shared state, and recommends (but does not run) the next phase. A fifth command, fix, re-enters the flow to correct course at any layer. Every phase's depth auto-sizes to the change — see Sizing.

/forge specify <name>   Understand the problem + capture requirements   → spec.md
/forge design           Architecture, contracts, verification gates     → design.md
/forge plan             Atomic tasks, dependencies, AC traces            → plan.md
/forge execute          Implement, then run independent verifiers        → working code
/forge fix <change>     Correct course mid-stream, keep the chain aligned → aligned artifacts + code

Dispatch

Read the first argument as the phase verb. Read the matching reference file fully before acting — it is the step-by-step playbook for that phase.

Verb	Read	Produces
`specify`	`references/specify.md` (+ `references/review.md`)	`./.specs/<slug>/spec.md`
`design`	`references/design.md` (+ `references/review.md`)	`./.specs/<slug>/design.md`
`plan`	`references/plan.md`	`./.specs/<slug>/plan.md`
`execute`	`references/execute.md` (+ `references/verification.md`)	code + commits
`fix`	`references/fix.md`	re-aligned artifacts + code

references/structural-standards.md is the single always-applied baseline for what good structure is and how a structural review runs. Three dispatches load it: review.md's under-design lens, execute.md's per-batch structural axis, and fix.md's claim lenses. It is the only structural check set in forge.

references/glossary.md indexes forge's load-bearing terms — the door verdict, blast radius, a seam, the three lies — and names where each one is defined. No phase dispatches it; read it when a pointer uses a term you cannot place.

If no verb is given, infer the phase from the request and confirm it. Never fail because a verb is missing or unknown. Common mappings:

Read the full file on GitHub · 240 lines

Files

What ships with it

17 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.

13d ago Changed · +25 lines · -32 tokens per session 00adb7f1a233
1mo ago First seen · 215 lines · 174 tokens per session scan A 1b52393f8464

Subscribe to this mod's changes

forge is a skill published in the GitHub repository emiliosheinz/agent-skills (20 stars, last pushed 8d ago), licensed MIT. It adds 142 tokens to every session and 3,197 once invoked, about $0.0006 per session on Opus 5.5. 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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