Oas Extensions

OAS Extensions

When to use

Use this skill any time the task involves attaching domain-specific data outside the Core/Layout vocabulary: industrial machinery, materials, MEP systems, site context, or vendor metadata (Autodesk/Revit families, APS URNs). If the data fits a Core entity directly (e.g. a Furniture placement), keep it in Core — don't reach for an extension.

Key types

• Extension envelope — top-level extensions dictionary keyed by extension name
• Machinery — industrial equipment with multi-axis rotation and CAD geometry source
• Material — material definitions referenced by id from Core/Layout entities
• Site — site context (boundaries, orientation, surroundings)
• AutodeskMetadata — Revit family names, APS URNs, vendor-specific identifiers

Critical rules

1. Dictionary format in OAS 1.1.0+ — "extensions": { "oas-machinery": { "version": "..." }, "oas-autodesk": { ... } }. Parsers must still accept the legacy array form, but new documents should emit the dictionary.
2. Furniture and 3D fields are no longer extensions — they moved into Core. oas-furniture (position, rotation, dimensions, in_room) and oas-3d (wall_height_mm, base_offset_mm, top_profile_points, etc.) are deprecated extension names. Put these fields directly on Core entities; do not declare "oas-furniture" in extensions.
3. Versioned per extension. Each extension block carries its own version field independent of the OAS document version. Semver applies.
4. Machinery has three independent rotation axes — rotation_deg (Z, the default), rotation_x_deg, rotation_y_deg. Separate fields in degrees; don't fold them into one.
5. Machinery ids must be globally unique across the entire document, not just within the machinery array.
6. geometry_ref vs geometry_source. Base oas-machinery uses a simple geometry_ref URI/path string. When oas-autodesk is also active, machinery may carry the structured geometry_source object (urn, external_id, item_id, file_name, is_y_up, import_mode, mesh_quality) for APS Model Derivative / ACC imports.
7. Vendor-specific names live in their extension, not in Core. Revit revit_family / revit_type, APS external_id, etc., go under oas-autodesk, never inline on Core Wall.type_name.
8. Extensions may not override Core invariants — no decimal coordinates, no redefining Room/Wall/Opening, no breaking the mm-integer rule.

Full schema

See docs/extensions.md for the full reference, including the dictionary envelope, per-extension schemas (machinery, autodesk, MEP, materials, site), and the 1.0→1.1 migration notes.

Related skills

• oas-core — the document an extension augments
• oas-layout — extensions also attach to resolved layouts (e.g. machinery placed on a floor)