# Add Capability

> Add something Diffuse can observe on a device (typed capability, collector, registry line, and tests). Use when the user wants a new collector, observable, or capability ID.

- Skill: `hoangsonww/add-capability` (Agent Skill)
- Install (CLI): `npx skillmds@latest add hoangsonww/add-capability`
- Raw SKILL.md: https://api.skillmd.com/api/skills/hoangsonww/add-capability/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: hoangsonww (https://skillmd.com/u/hoangsonww)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/hoangsonww/add-capability

---


# Add a capability

Read in order: `Documentation/CapabilityGuide.md`, `Documentation/CollectorGuide.md`, `Documentation/adr/0002-capability-driven.md`.

## Create

1. Capability ID and schema in `Packages/DiffuseCapabilities` (or the catalog the guide points at).
2. A collector in `Packages/DiffuseCollectors` for each platform that can actually observe it. Do not pretend a Watch can enumerate Mac apps.
3. A registry line on each platform that should expose it.
4. Tests with a **fake** — never require live hardware in CI. Put API tests in `Tests/Domain` if the new type is public.

## Do not touch

Adding a capability must **not** require edits to the diff engine, snapshot store, search, export, or app screens. If you are adding a SwiftUI view for one capability, stop.

## Privacy

Every collected field needs `public` / `local` / `sensitive` / `restricted`. Restricted fields should not be collected. See skill `privacy`.

```bash
swift test --parallel
./Scripts/format.sh
```

If a golden fixture schema changed, skill `fixtures`.