The universal schema is what a robot is — its links, joints, sensors, actuators and capabilities. Assets and twins each carry one, and both can now be edited as JSON from the app by anyone with write access.
Where to find it
Asset — open the asset, go to the Files tab, and choose Edit JSON on the Base schema card.
Twin — select the twin in the environment editor, open Advanced, and choose Schema JSON.
What gets checked before a save lands
The editor checks the JSON parses and is an object, and reports the line and column when it does not. On save, the server validates the whole document — capabilities, and a cross-check that any drive block names joints that actually exist. A schema that fails is refused with the reason, and nothing is written.
Two shapes are always refused: an empty schema, and one that drops links when it previously had them. Removing sensors or actuators is a normal edit and is allowed.
For an asset, some checks report rather than refuse. Your edit is saved and the editor lists what it found, so you can fix it in a follow-up edit instead of being blocked.
Removing links or joints asks for confirmation first. They are what the 3D viewer and the simulation exporter walk, so removing them changes what every twin of that asset resolves to.
If someone else edits at the same time
The editor remembers which version of the schema you opened. If someone saves a change before you do, your save is refused rather than overwriting theirs — close and reopen the editor to load the current schema, then reapply your edit.
What a rebuild or a sync discards
Assets — regenerating the schema from the URDF keeps per-joint home positions, sensors, actuators, capabilities and collision config. Anything else you edit by hand is discarded on the next rebuild.
Twins — a twin’s schema is its own snapshot of its asset. Running sync with asset re-snapshots it and discards edits made here, apart from sensor fields you changed and joint homes you authored. Editing a twin’s schema never changes its asset.
Moved joint zeros
If an edit changes a joint’s pose or axis, it moves that joint’s zero. Saved joint positions and home positions are offsets from that zero and are not adjusted to match, so they will refer to a different physical pose afterwards. The editor says so when it happens — re-teach those positions rather than assuming they carried over. 
