# scratch — HTML diagram design guide for agents
You are authoring a standalone `.html` file that the scratch viewer transcludes
inline wherever a markdown doc references it. Unlike a live sketch surface, this
is **durable knowledge**: the file is baked into the page at render time and must
keep working offline and after `scratch export`. Read this once before your first
diagram.
## Embedding
Write `diagram.html` as a loose file **next to** the markdown doc, then reference
it with image syntax — that's the whole API:
```md
```
- Resolved by relative path. Do **not** `scratch add` it — it's a loose asset,
not a registered pad file.
- The viewer reads the file at render time and inlines it as a sandboxed
`