crafting-rules

A guide for creating and editing OpenCode rules, which are Markdown files that tell an agent how to behave in particular situations. Rules can apply to certain files, projects, tools, models, branches, or operating systems.

In plain words
What is it for?
Use it to write project rules, limit guidance to matching files or prompts, and define environment-specific agent behavior.
Why use it?
It helps turn repeated instructions into saved guidance that is applied at the right time and scope.

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/frap129/opencode-rules/crafting-rules
Any agent
npx skills add frap129/opencode-rules --skill crafting-rules
Clone the repo
git clone --depth 1 https://github.com/frap129/opencode-rules

Made for: Claude Code, Codex.

Per session 58 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,224 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 $0.00058 $0.02224
Opus 5 $0.00029 $0.01112
Sonnet 5 $0.00012 $0.00445
Haiku 4.5 $0.00006 $0.00222

Measured 2d ago against content hash adf32cd2b1b5, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

crafting-rules 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.

skills/crafting-rules/SKILL.md · 221 lines

How it starts

The opening of the file, as written. The whole thing — 221 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Crafting Rules

Overview

Rules are markdown files with optional YAML frontmatter, injected into the system prompt to guide agent behavior. Scope them with filters or leave unconditional for global standards.

Field Reference

Field Type Category Purpose
globs string[] Legacy Apply when any observed file's path matches a pattern
fileContains string | string[] Legacy Apply when an observed file's text contains a literal substring
keywords string[] Legacy Apply when the user's latest prompt matches a keyword
tools string[] Legacy Apply when any listed tool ID is available
model string[] Runtime Match against the current LLM model ID
agent string[] Runtime Match against the current agent type (e.g., programmer)
command string[] Runtime Match against the current slash command (e.g., /plan)
project string[] Runtime Match against detected project tags (e.g., node, rust)
branch string[] Runtime Match against git branch name (supports glob patterns)
os string[] Runtime Match against OS (linux, darwin, win32)
ci boolean Runtime Match against CI environment (true = in CI)
match 'any' | 'all' Combinator any (default): OR logic. all: AND logic.
  • All fields are optional; no frontmatter means the rule always applies.
  • With match: any (default), the rule applies if ANY declared condition matches.
  • With match: all, the rule applies only if ALL declared conditions match.
  • globs and fileContains form one file-observation family: when both are declared, the same observed file must satisfy both. The family counts as one condition in the algebra.
  • File observations come only from successful live Read, Write, Edit, Apply Patch, and path-associated LSP tool events. Grep, Glob, shell, custom/MCP tools, message prose, and historical tool events contribute nothing to globs/fileContains.
  • A durable rule first matched by a live file observation takes effect at that earliest dispatch — not on the next user message.
  • When a runtime value is unavailable (e.g., no git repo), that dimension is a non-match.

Read the full file on GitHub · 221 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 · 221 lines · 58 tokens per session scan A adf32cd2b1b5

Subscribe to this mod's changes

crafting-rules is a skill published in the GitHub repository frap129/opencode-rules (112 stars, last pushed 2d ago), licensed MIT. It adds 58 tokens to every session and 2,224 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.

Related

Other skills, from other repositories

systematic-debugging

Use when encountering any bug, test failure, or unexpected behavior, before proposing fixes.

obra/superpowers · 21 tokens

next-cache-components-adoption

Turn on Cache Components in a Next.js app and resolve the blocking routes it surfaces. Use when the user wants to enable, adopt, or migrate to Cache Components, flip the cacheComponents flag, work through a flood of blocking-prerender / instant validation errors, run the cache-components-instant-false codemod, or…

vercel/next.js · 95 tokens

babysit-pr

Babysit a GitHub pull request after creation by continuously polling review comments, CI checks/workflow runs, and mergeability state until the PR is merged/closed or user help is required. Diagnose failures, retry likely flaky failures up to 3 times, auto-fix/push branch-related issues when appropriate, and keep…

openai/codex · 114 tokens

imagegen

Generate or edit raster images when the task benefits from AI-created bitmap visuals such as photos, illustrations, textures, sprites, mockups, or transparent-background cutouts. Use when Codex should create a brand-new image, transform an existing image, or derive visual variants from references, and the output…

openai/codex · 113 tokens

cpu-profile-analysis

Analyze V8/Chrome CPU profiles (.cpuprofile) and DevTools trace files (Trace-.json). Use when: profiling performance, investigating slow functions, comparing code paths, finding bottlenecks, analyzing timeToRequest, understanding call trees from sampling profiler data, analyzing layout/paint/rendering, investigating…

microsoft/vscode · 71 tokens

next-cache-components-optimizer

Drive a Next.js route to instant navigation by setting up an agentic loop, under Cache Components / PPR, on initial load (hard navigation) and client-side navigation (soft navigation). Encode the goal as a failing @next/playwright instant() e2e and work it to green, one verified route at a time; the shipped test then…

vercel/next.js · 170 tokens