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:

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.

# 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).

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

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

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.

"LUT-style" in the table means generating a fresh GLSL color grade that resembles a LUT — only when the user wants something new. If they want to apply a .cube file already in the library, don't generate; bind the existing asset instead.

No separate LUT or mask generator for the generation path — those are all effect.

Applying an Existing LUT Asset

.cube files uploaded by the user become lut assets. Applying one to a clip is not generation — it's a single edit_item call that attaches an effect item whose assetId is the literal string "lut" and whose propertyOverrides.lut binds the real LUT asset id. (Legacy contract; the unified LUT API binds the LUT effect asset id directly — see edit_item description.)

edit_item(json: '{"adds":[{"type":"effect","targetItemId":"<clip-id>","assetId":"lut","propertyOverrides":{"intensity":1,"lut":{"assetId":"<lut-asset-id>","assetType":"lut","type":"asset"}}}]}')

Key points:

• assetId is the literal string "lut", not the LUT asset's id. The real LUT asset id goes inside propertyOverrides.lut.assetId.
• intensity is 0–1; default 1 (full strength).
• targetItemType defaults to video; also supports image, gif.
• To swap a LUT on an existing effect: update propertyOverrides.lut.assetId to the new LUT asset id.
• To remove: delete the effect item.

Do not call generate.ts for this path. Do not pass a real LUT asset id as assetId — the editor checks assetId === "lut" to route into the LUT renderer; passing a UUID silently renders nothing.

Usage

Before calling submit_shader, restate the user's intent in one concrete sentence, then proceed immediately. After track_progress returns, state what was produced in one line — do NOT ask "要保留还是重新生成".

submit_shader({
  type: "effect",
  prompt: "Chromatic aberration with RGB split",
  name: "Chromatic Aberration",
});

submit_shader({
  type: "transition",
  prompt: "Smooth crossfade with soft edge",
  name: "Crossfade",
});

submit_shader({
  type: "effect",
  prompt: "Cinematic teal-orange color grade",
});

submit_shader({
  type: "effect",
  prompt: "Stronger version",
  referenceAssetIds: ["effect_asset_id"],
});

Strategy

• Submit, then stop. Tell user the job was created.
• Use the track_progress tool for status/wait after submission.
• Generation always produces a library asset — never refuse because the timeline isn't ready.
• Apply is separate and optional. Only apply when user explicitly asks ("加到视频", "apply", "用到第一段"). When ambiguous, default to library-only.

Editing Existing Properties

Any time you're about to edit shader asset.properties, applied effect/transition item.propertyOverrides, or promote a hardcoded shader value, read references/property-changes.md first.

It reinforces that shader properties is an array, but the allowed shader property types are only number, boolean, color, select, and vec2. Motion Graphic properties are also arrays, but use a different type set.

Parameters

Output

Returns { success, job: { jobId, status }, manage: { status, wait, watch } }.

Applying to Timeline

Only when user explicitly requests. Call read_project first for fresh timeline state.

Effect

edit_item(json: '{"adds":[{"type":"effect","targetItemId":"<id>","assetId":"<id>","enabled":true,"propertyOverrides":{}}]}')

Transition

Requires two adjacent same-track endpoints. edit_item validates live seam feasibility and refuses durations that would require freeze frames or overlapping neighboring transitions. If the add fails, retry with the suggested durationInFrames, trim the clips to expose handles, delete/shorten neighboring transitions, or keep a hard cut.

edit_item(json: '{"adds":[{"type":"transition","assetId":"<id>","outgoingItemId":"<id1>","incomingItemId":"<id2>","durationInFrames":30}]}')

Validation & Verification

Backend Validation

When generating via generate.ts, the backend handles validation automatically (transpile, AST security, class structure, retry on failure).

Manual Code Verification

NEVER write shader code from scratch. Always use generate.ts for new shaders. This section is ONLY for modifying existing shader code that was already generated.

When writing shader code manually, read ${CLAUDE_SKILL_DIR}/references/design-principles.md first. If the change touches editable properties, also read ${CLAUDE_SKILL_DIR}/references/property-changes.md.

Typical workflow:

1. read_project with the shader assetId and code: true — read the current source.
2. Edit the source in your own context.
3. edit_asset with action=update, the same assetId, and the full replacement source inline in json.code. Validation runs automatically on update — if code is invalid, the update is rejected with error details.