---
description: Language plugin system — LanguageSupport registry, text/markdown/zig/json plugins
globs:
  - src/sdk/**
  - src/plugins/text/**
  - src/plugins/markdown/**
  - docs/PLUGINS.md
---

# Language Plugins

Source of truth: `docs/PLUGINS.md` (markdown lives in `plugins/markdown`, not `core`).

## Invariants

- **`text` owns all text documents** — load/save/draw/undo. Language plugins never implement document vtable hooks.
- **Language plugins register `LanguageSupport` only** — optional `treeSitterHighlight` and/or `previewPane` hooks looked up by extension via `Host.treeSitterHighlightFor` / `Host.previewProviderFor`.
- **Plugins never import each other** — they meet only at the SDK registry.
- **`markdown` is a bundled in-tree utility plugin** — owns cmark renderer + `.md` preview; shell imports `@import("markdown")` plugin hub for store READMEs.
- **`zig` / `json` are external store plugins** in `~/dev/fizzyedit/zig` and `~/dev/fizzyedit/json`.

## SDK change checklist

When touching the language boundary:

1. `src/sdk/language.zig` — types
2. `src/sdk/Host.zig` — registry + lookup fns + `unregisterPlugin` cleanup
3. `src/sdk/dylib.zig` — add types to `sdk_boundary_types`
4. `src/sdk/version.zig` — bump `sdk_version` + `recorded_sdk_shape_fingerprint`
5. Run `zig build test-sdk-version`

## Build rule

Plugin builds must not leak app-only deps (Velopack). After build-graph changes:

```sh
cd src/plugins/image && rm -rf .zig-cache zig-out zig-pkg && zig build -Doptimize=ReleaseFast
ls zig-pkg | grep -i velo  # must be empty
```