domain

Repository instructions that tell engineering skills how to find and use domain documentation, including context files and architecture decision records.

In plain words
What is it for?
Use them before investigating a codebase: read the relevant CONTEXT.md or CONTEXT-MAP.md files and the architecture decisions that affect the area.
Why use it?
They help an agent understand the project’s business terms and past design decisions before exploring or changing code.

Agent

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 agents/frap129/opencode-rules/domain
Clone the repo
git clone --depth 1 https://github.com/frap129/opencode-rules
Per session 0 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 492 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 72% copy Near-identical to another mod 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 $0.00000 $0.00492
Opus 5 $0.00000 $0.00246
Sonnet 5 $0.00000 $0.00098
Haiku 4.5 $0.00000 $0.00049

Measured 2d ago against content hash edc6d6131fdf, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

domain 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

This is a copy

72% identical to domain — 46 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

docs/agents/domain.md · 52 lines

What it actually says

Domain Docs

How the engineering skills should consume this repo's domain documentation when exploring the codebase.

Before exploring, read these

  • CONTEXT.md at the repo root, or
  • CONTEXT-MAP.md at the repo root if it exists: it points at one CONTEXT.md per context. Read each one relevant to the topic.
  • docs/adr/: read ADRs that touch the area you're about to work in. In multi-context repos, also check src/<context>/docs/adr/ for context-scoped decisions.

If any of these files don't exist, proceed silently. Don't flag their absence; don't suggest creating them upfront. The /domain-modeling skill (reached via /grill-with-docs and /improve-codebase-architecture) creates them lazily when terms or decisions actually get resolved.

File structure

Single-context repo (most repos):

/
├── CONTEXT.md
├── docs/adr/
│   ├── 0001-event-sourced-orders.md
│   └── 0002-postgres-for-write-model.md
└── src/

Multi-context repo (presence of CONTEXT-MAP.md at the root):

/
├── CONTEXT-MAP.md
├── docs/adr/                          ← system-wide decisions
└── src/
    ├── ordering/
    │   ├── CONTEXT.md
    │   └── docs/adr/                  ← context-specific decisions
    └── billing/
        ├── CONTEXT.md
        └── docs/adr/

Use the glossary's vocabulary

When your output names a domain concept (in an issue title, a refactor proposal, a hypothesis, a test name), use the term as defined in CONTEXT.md. Don't drift to synonyms the glossary explicitly avoids.

If the concept you need isn't in the glossary yet, that's a signal: either you're inventing language the project doesn't use (reconsider) or there's a real gap (note it for /domain-modeling).

Flag ADR conflicts

If your output contradicts an existing ADR, surface it explicitly rather than silently overriding:

Contradicts ADR-0007 (event-sourced orders), but worth reopening because…

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 · 52 lines · 0 tokens per session scan A edc6d6131fdf

Subscribe to this mod's changes

domain is an agent published in the GitHub repository frap129/opencode-rules (112 stars, last pushed 2d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 492 tokens. A static security scan graded it A with 0 findings. It is 72% identical to domain, differing in 46 lines, and is treated as a copy.

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