lopatin/snaketron/author-skin

Author a Snaketron skin

Build one exact retained prototype candidate as a SkinDoc v2 revision. This package is agent-neutral: use the inputs and output schemas supplied by the caller, not an agent's transcript, private memory, or provider-specific executable.

Required inputs

Stop with a typed invalid_input result if any item is absent or inconsistent:

• prototype bytes or a readable content-addressed reference;
• its prototype manifest and one exact input_authority record in either

approved_prototype or draft_submission mode;

• the repository-canonical design direction and literal human feedback;
• the generated capability manifest for the pinned schema/renderer SHA and a

separate literal host-operation capability record (authority modes, operations, and any tighter driver limits);

• output schemas, budgets, pure-tool allowlist, and artifact workspace.

The authority artifact hash must equal the prototype image hash. In approved_prototype, require the exact human prototype_approval. In draft_submission, require the agent-selected candidate hash, literal selection rationale, and retained selection-record hash; never describe that record as human approval. Never substitute another candidate or silently regenerate the selected direction.

Load the contract

Read references/contract.md completely. It is locked policy. Always read the locked shared Skin Design Guidelines completely and apply them in the implementation plan. Then read only the other craft references needed for this build:

• Always read references/prototypes.md and

references/playbook.md.

• For procedural layers or effects, read

references/layers-effects.md.

• For any image source, read

references/textures-sprites.md.

• For separable components, reusable modifier objects, extraction, or video,

also read references/modifiers-video.md.

• Before returning a result, read

references/validation.md.

Author in two logical passes

1. Inspect the prototype at game scale and identify the few visual features

that carry its identity. Treat its implementation_hint as advice.

1. Choose layers, texture, sprite_sheet, or hybrid using the routing

rules in the playbook. Prefer layers for patterns and formula-driven motion.

1. Before requesting or generating assets, emit implementation-plan.json

conforming to schemas/implementation-plan.schema.json. Fill its bounded design_guidelines object from the shared guidelines; these decisions must agree with the executable layer, asset, wrap, and animation plan. Record input_authority, the common animation period, and every image asset's natural X length and derived frame count Y, plus placement and wrap axes. Map every asset one-to-one to a modifier record, image layer, and earlier fallback. Put the reason for changing the prototype hint in rationale.

1. Compose the v2 document draft. For each planned image asset, declare one

matching texture name and use the same asset_index and texture_name in its request. Put a complete ordinary fallback immediately below every image layer. The only unresolved reference is pending:asset:<index>, with the planned kind and no descriptor. Do not fabricate a generated hash, descriptor, upload, or successful gate.

1. If ordinary generated assets are needed, emit generate_asset tool

requests whose arguments conform to schemas/asset-request.schema.json for the caller's image_generator role. Emit edit_asset only in a repair phase the caller explicitly advertises; otherwise the deterministic forge owns its isolated local LaMa helper. The configured generator default may be Gemini 3 Pro Image, but the skill never requires Gemini or calls a provider directly when running as a factory task worker. Extraction, modifier reuse, and video are separate journaled host capabilities: use their request schemas only when the caller advertises the exact operation and retained-input/output contract. Otherwise return platform_gap.

1. Return only the plan, v2-shaped document draft, tool requests, trace, usage,

or typed failure allowed by the caller's worker-result schema. If the prototype cannot be expressed by the pinned capabilities, return platform_gap; do not create a Rust skin.

1. The driver journals every external operation, generates/repairs assets,

binds exact served refs and descriptors into the draft, validates the exact bytes, registers the private revision, and captures real-browser evidence. A later bounded repair request may supply failed artifacts and reports, but neither worker nor driver overwrites their history. A pure factory worker never uploads, registers, approves, publishes, uses Git, or mutates external storage, and the factory accepts only approved_prototype. An explicitly authorized interactive agent acting as the advertised host may journal and execute the declared generation/extraction/binding operations, register the exact private revision, and request Snaketron admin review. It may never publish; an unadvertised operation is platform_gap.

The factory explicitly bundles this directory and records its SHA. Agent discovery wrappers are conveniences only; see references/integration.md.