shader-gen

# Shader Generator

Submit-only: creates a backend generation job, returns `jobId`. Use the `track_progress` tool for job lifecycle after submission.

**Always use `generate.ts` for new shaders.** Manual authoring is only for editing existing asset code — never as a fallback when generation fails.

## Catalog-first rule — try existing assets before generation

Before generating a shader, call `browse_library` unless the user names an exact asset id that is already visible in `read_project`.

`browse_library` is the source of truth for built-in effects, built-in transitions, and project effect/transition assets. Built-ins are stable global asset ids, not per-project DB assets, so they may not appear in `read_project` asset lists.

Apply catalog entries with `edit_item`, do **not** call `submit_shader`.

Good catalog searches:

```text
browse_library(query: "zoom")
browse_library(category: "transitions", query: "dissolve")
browse_library(category: "audio-fx")
```

Generate only when no catalog entry matches the user's intent closely enough.

### `builtin:zoom` is track-bound only — DO NOT use item-bound

The default effect mode is `"item-bound"` (attach to a single item via `targetItemId`). **`builtin:zoom` does NOT render in item-bound mode** — the renderer reads zoom data exclusively from track-bound effect items. An item-bound zoom inserts into the DB silently but shows nothing in preview.

Use `mode: "track-bound"` with `trackId` + `trackBoundFrom` + `trackBoundDurationInFrames`. These three fields are required.

```text
# Zoom on the entire video clip
edit_item(json: '{"adds":[{"type":"effect","assetId":"builtin:zoom","mode":"track-bound","trackId":"<clip-trackId>","trackBoundFrom":<clip-fromFrame>,"trackBoundDurationInFrames":<clip-durationInFrames>,"propertyOverrides":{"magnification":1.5,"shape":"hold"}}]}')

# Zoom on a sub-range of the clip (e.g. frames 90–150 only, a punch zoom on a beat)
edit_item(json: '{"adds":[{"type":"effect","assetId":"builtin:zoom","mode":"track-bound","trackId":"<trackId>","trackBoundFrom":90,"trackBoundDurationInFrames":60,"propertyOverrides":{"magnification":2,"shape":"punch"}}]}')
```

Get `trackId` / `fromFrame` / `durationInFrames` from `read_project` (each video/image item lists its trackId and timeline-frame range).

| Key             | Type   | Range / values                             | Default | Notes                                          |
| --------------- | ------ | ------------------------------------------ | ------- | ---------------------------------------------- |
| `magnification` | number | 1–4                                        | `1.5`   | Zoom factor; 1 = no zoom, 2 = 2× in            |
| `focalPointX`   | number | 0–1                                        | `0.5`   | Horizontal focal point (0 = left, 1 = right)   |
| `focalPointY`   | number | 0–1                                        | `0.5`   | Vertical focal point (0 = top, 1 = bottom)     |
| `shape`         | select | `punch` / `hold` / `slow-push` / `instant` | `hold`  | Animation curve                                |
| `focalMode`     | select | `auto` / `manual`                          | `auto`  | `auto` picks subject; `manual` uses focalPoint |
| `easeInFrames`  | number | 0–60                                       | `8`     | Frames to ramp in                              |
| `easeOutFrames` | number | 0–60                                       | `8`     | Frames to ramp out                             |

Omit `propertyOverrides` entirely for default zoom. Send only the keys you want to change — patch semantics.

### Track-bound vs item-bound — the broader rule

Effect items in the schema have two modes:

- **`item-bound`** (default): `targetItemId` only. Effect covers the whole target item's playback. Works for shader effects, LUTs, color grades, blurs.
- **`track-bound`**: `trackId` + `trackBoundFrom` + `trackBoundDurationInFrames`. Effect covers a timeline range on a track, independent of any item. Required for `builtin:zoom`; also valid for any shader effect when you want it to cover a specific timeline range (e.g. a transition-like color shift across the boundary of two clips).

Default to item-bound for shader effects. Use track-bound when (a) the asset requires it (zoom), or (b) the effect should cover a timeline range that doesn't match a single item.

### Built-in LUT properties

```text
edit_item(json: '{"adds":[{"type":"effect","targetItemId":"<clip-id>","assetId":"builtin:slog3-s709","propertyOverrides":{"intensity":1}}]}')
```

| Key         | Type   | Range | Default | Notes                          |
| ----------- | ------ | ----- | ------- | ------------------------------ |
| `intensity` | number | 0–1   | `1`     | LUT strength; 1 = full applied |

To swap: delete the effect and re-add with a different `assetId`. To remove: delete the effect item.

These are separate from user-uploaded `.cube` LUT assets (see "Applying an Existing LUT Asset" below) — those use a different code path with `assetId:"lut"`.

## Beta Status Gate

New shader generation is beta. Before generating, warn the user and wait for explicit confirmation.

Use the user's language. Chinese: "新的特效/转场生成目前还是 beta 阶段，可能会有不稳定的问题。如果你坚持要做，我可以帮你实现。" Skip if user already acknowledged in the same request.

## Supported Targets

Effects and transitions apply to `video`, `image`, and `gif` items.

## Type Routing

Before generating anything, check two non-generation paths first:

1. **Catalog entry** — use `browse_library` for built-in and project effects/transitions.
2. **User-uploaded `.cube` LUT asset** that already exists in the project library — separate code path, see "Applying an Existing LUT Asset" below. The asset shows up in `read_project` with `type: lut`.

| User wants                                                           | `--type`     |
| -------------------------------------------------------------------- | ------------ |
| Video appearance (color, blur, glow, grain, di