The facade writes a math value component-wise, and an axis key is the domain identity

addBinding replaces object[key] for every scalar control. For a value the math dispatch matched it copies the committed axes onto the object already there instead, so a bound THREE.Vector3 keeps its identity, its methods, and any other reference an application holds to it. A caller who binds mesh.position gets a live Vector3 back from the change handler, not a plain record that has quietly replaced it.

That write leaves the property's identity unchanged, which the field's own hasChanged reads as no edit at all: ADR-0021 makes vector properties immutable snapshots compared component-wise, and the same object compares equal to itself. Binding.refresh() therefore assigns a fresh record built from the value's own numeric axes rather than the bound object.

Axes the bound object does not already carry are skipped, so binding a two-axis object never grows a z on it, and a Mixed axis is never written as a number.

Because writes go by axis name, the name has to be the truth. jolly-vector2 takes an axes pair, "xy", "xz" or "yz", and that key is what value holds, the glyph in the corner chip, the --jolly-axis-<key> colour and the data-axis scrub target. A field sizing a box across the ground plane reads as a red X and a blue Z, and hands back { x, z }. Switching axes on a mounted field moves each axis by position unless the new value already carries the new axes, so a template binding both together does not see its own value overwritten.

jolly-transform is left out of the dispatch. It is not a JollyField: it carries no label, disabled, align or path, and it owns three sub-fields that lock and revert independently, so one Binding cannot describe it. Three bindings, or the element directly, can.

Considered Options

• Replacing the property, as scalars do. Swaps a THREE.Vector3 for a plain object on the first edit, breaking every method call and every other reference to it.
• An explicit write: "assign" | "mutate" option. Every 3D caller wants the same answer, and the wrong default silently corrupts the bound object rather than failing.
• Assigning the bound object back to the field on refresh. Component-wise hasChanged sees the same object and never repaints.
• Relabelling a jolly-vector2 while keeping keys x and y. The field would show Z while writing y onto an object carrying x and z.
• A separate jolly-vector2-xz element. Three near-identical elements, registrations and API pages for one property's worth of difference.