Agent Universal Guideline formatter

One universal format for AI coding agent instructions. Write once, sync everywhere.

aniversize lets you maintain a single source of truth for your AI coding agent configuration and synchronise it to whichever agent tool your team uses — GitHub Copilot, Claude Code, Codex, or Antigravity.

Why

Every AI coding agent has its own configuration format:

| Agent | Config file(s) | |---|---| | GitHub Copilot | .github/copilot-instructions.md, .github/instructions/*.instructions.md | | Claude Code | CLAUDE.md, CLAUDE.local.md, .claude/commands/ | | Codex | codex.json (customInstructions), .codex/ | | Antigravity | ANTIGRAVITY.md, .antigravity/ |

aniversize stores everything in a neutral .aniversize/ folder and converts in both directions — from agent files into universal format (unify) and from universal format into agent files (generate, coming soon).

Install

# Global
npm install -g aniversize

# One-off
npx aniversize <command>
bunx aniversize <command>

Commands

identify [root]

Detect which AI coding agent is configured in the project and write .aniversize/meta.json.

aniversize identify
# Scanning /my/project for AI coding agent configurations...
#
# GitHub Copilot:
#   .github/copilot-instructions.md
#   .github/instructions/
#
# Primary agent: GitHub Copilot
# Wrote .aniversize/meta.json

Pass --dry to skip writing meta.json (prints Would write ... instead).

The detected agent is stored in .aniversize/meta.json:

{ "primary": "copilot" }

unify [agent]

Read the agent's existing configuration files and write them into the .aniversize/ universal format. Stale .aniversize/ files that have no corresponding source are deleted.

# Auto-detect agent from meta.json (or run identify first)
aniversize unify

# Explicit agent
aniversize unify copilot
aniversize unify claude

# Preview without writing anything
aniversize unify --dry

Example output:

Unifying GitHub Copilot configuration into .aniversize format…

  wrote   .aniversize/PROJECT.md
  wrote   .aniversize/rules/folder-module.md
  wrote   .aniversize/rules/functional-style.md
  deleted .aniversize/rules/old-rule.md

Done. 3 file(s) written, 1 file(s) deleted.

With --dry the output uses would write / would delete and no files are touched.

If no agent is specified and no meta.json exists, unify runs identify automatically.

update [agent]

Read the .aniversize/ universal format and write the appropriate configuration files for the primary agent. This is the reverse of unify.

# Auto-detect agent from .aniversize.json / meta.json (or run identify first)
aniversize update

# Explicit agent
aniversize update copilot
aniversize update claude

# Preview without writing anything
aniversize update --dry

Example output:

Updating GitHub Copilot configuration from .aniversize format…

  wrote   .github/copilot-instructions.md
  wrote   .github/instructions/typescript.instructions.md
  wrote   AGENTS.md

Done. 3 file(s) written, 0 file(s) skipped.

With --dry the output uses would write and no files are touched.

If no agent is specified and no .aniversize.json / meta.json exists, update runs identify automatically.

Mappings from .aniversize/ to agent files:

| Source | Copilot | Claude | Codex | Antigravity | |---|---|---|---|---| | PROJECT.md | .github/copilot-instructions.md | CLAUDE.md | codex.json (customInstructions) | ANTIGRAVITY.md | | MEMORY.md | — | CLAUDE.local.md | — | — | | AGENTS.md | AGENTS.md | AGENTS.md | AGENTS.md | AGENTS.md | | rules/*.md | .github/instructions/*.instructions.md | .claude/commands/*.md | .codex/*.md | .antigravity/*.md | | skills/*/SKILL.md | .github/instructions/*.instructions.md | .claude/commands/*.md | .codex/*.md | .antigravity/*.md |

Rules without frontmatter are universal and written for every agent.

setup [agent]

Set the primary agent in .aniversize.json and write its configuration files from .aniversize/. Equivalent to running switch followed by update in one step.

# Use agent from .aniversize.json, or prompt if not set
aniversize setup

# Explicit agent
aniversize setup copilot
aniversize setup claude

# Preview without writing anything
aniversize setup --dry

Example output:

Setting up GitHub Copilot configuration…

  wrote   .aniversize.json
  wrote   .github/copilot-instructions.md
  wrote   AGENTS.md

Done. 3 file(s) written, 0 file(s) skipped.

With --dry the output uses would write and no files are touched.

If no agent is specified and .aniversize.json has no primary, an interactive prompt asks you to pick one.

The .aniversize Format

.aniversize/
  PROJECT.md        — Project overview; loaded by every agent
  AGENTS.md         — Agent role definitions (e.g. Explore, Review, Implement)
  MEMORY.md         — Persistent memory hints; keep short
  meta.json         — Written by identify; read by unify/generate
  rules/
    {name}.md       — Single rule with YAML frontmatter declaring which agent(s) use it
  skills/
    {name}/
      SKILL.md      — Self-contained capability description

Rule frontmatter

---
copilot: instruction
claude: rule
applyTo: "src/**"
---

# Rule: No direct DOM manipulation
Always use framework abstractions instead of `document.querySelector`.

A rule file with no frontmatter is treated as universal — applied to all agents.

Development

bun install          # install dependencies
bun run dev -- identify   # run from source
bun run typecheck    # type-check without building
bun run build        # compile to dist/
bun test             # run tests

License

MIT © OwlMeans