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 browse_assets.

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 browse_assets.

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 uses the same track-bound placement as every effect

Effects always have timeline geometry. For a whole-clip effect, pass targetItemId; ChatCut resolves it to a clip-anchored range covering that clip. For an explicit timeline range, pass trackId + trackBoundFrom + trackBoundDurationInFrames.

# Zoom on the entire video clip
edit_item(json: '{"adds":[{"type":"effect","assetId":"builtin:zoom","targetItemId":"<clip-id>","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"}}]}')

Use preview_timeline({views:["timeline"],tracks:["V1"]}) to obtain track item ids and timeline-frame ranges. Use inspect_item({itemId:"..."}) when exact item detail is needed.

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

Clip-anchored vs adjustment-track

Effect items have two placements, both with a concrete time range:

• Clip-anchored: pass targetItemId for the whole clip, or include an explicit range that intersects the clip. The stored range is local to that clip and follows it when it moves.
• Adjustment-track: pass trackId + trackBoundFrom + trackBoundDurationInFrames for a range over empty track space. The range is absolute on the timeline.

Use targetItemId for whole-clip effects. Use explicit track geometry only when the requested range differs from a clip's full duration.

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.

User-uploaded .cube LUT assets take this exact same shape — only assetId differs. See "Applying an Existing LUT Asset" below.

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 — bind it instead of generating, see "Applying an Existing LUT Asset" below. It shows up in browse_assets as type: effect with a lut-typed entry in editableProperties.

"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

Default target is the timeline. "Apply this LUT" means an edit_item effect on the clip. Only reach for edit_asset sourceLut when the user asks for the source itself everywhere it appears — every clip cut from that asset, or a log-to-Rec.709 normalization of the footage — because that changes every instance of the asset on every timeline.

.cube files uploaded by the user become effect assets with category: "lut". Applying one to a clip is not generation — it is the same edit_item effect shape as a built-in LUT, with that asset's own id as assetId:

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

Key points:

• assetId is the LUT effect asset's real id. There is no literal "lut" assetId, and no LUT binding nested inside propertyOverrides.
• propertyOverrides carries only intensity (0–1, default 1). The .cube binding lives on the asset, not on the effect item.
• Find the id with browse_assets type:"effect": a LUT asset is the one whose editableProperties contain a lut-typed key. Built-in LUTs come from browse_library category:"luts".
• targetItemType defaults to video; also supports image, gif.
• To swap: delete the effect and re-add with the other LUT's assetId. To remove: delete the effect item.
• To grade a whole source clip everywhere it appears instead of one timeline item, use edit_asset update with {"sourceLut":{"assetId":"<lut-effect-asset-id>"}} on the video/image/gif asset; {"sourceLut":null} removes it.
• If the .cube is not in the project yet, you cannot get it in: this surface has no LUT import path, and .cube is not an accepted chat attachment either, so never ask the user to send you the file. Ask them to drag it into the editor's media pool instead — the editor registers it as a LUT asset and it then shows up in browse_assets. Do not tell them ChatCut cannot handle .cube; the editor can.

Do not call submit_shader for this path.

After applying, confirm with preview_timeline that the effect is listed on the target clip's track. Do not report success from the edit_item response alone.

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. Refresh the affected timeline with view:"timeline", passing track to narrow the read when appropriate.

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. inspect_asset with the shader assetId and includeCode: 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.