Aetheria/docs/shield-presentation-contract.md

Shield and Pickup Presentation Contract

Date: 2026-09-18

Status: target, operator direction only. Nothing here is built or scheduled. The panel interceptor's means live in docs/shield-panel-cut.md; the Lariat has no map. This document owns the contract both answer to.

Why

Aetheria is growing more than one presentation of the same capabilities: the existing field shield (FieldDriver), the hard-light panel interceptor, and the Lariat. They must be interchangeable without the simulation knowing which one is equipped.

Rulings (operator, 2026-09-18)

• Every shield effect is a drop-in behavioural replacement. A presentation takes capability events, presents them, and decides nothing.
• Coverage is expressed through the ship's envelope, not through an effect's own geometry. The envelope is derived from the existing per-ship shield transform, not authored twice (docs/shield-panel-cut.md R6).
• Presentation may anticipate. Operator: "anticipatory is great, and we'll want it for other one too". A presentation may begin reacting before a shot lands, and may be wrong when it does.
• One presentation may serve several capabilities. Operator: "the Lariat would be a presentation for both pickup and shielding capabilities."
• The hits a presentation shows are cosmetic. Fire control decides what happened; the intercept point is where the presentation says the shot arrived (docs/shield-panel-cut.md R6).

The anticipation feed

Capability events (ServerShared/CapabilityEvents.cs) report what happened. Anticipation needs what is about to happen, which is a different kind of signal and must never be mistaken for the first:

• It is speculative. A threat may miss, be absorbed by something else, or be destroyed in flight. A presentation that committed to it is simply wrong, and a whip that lunges at a shot it does not block is characterful, not a bug.
• Nothing outside presentation may read it. No gameplay decision, no damage, no state change. If a consumer wants certainty it waits for the capability event.
• Its source is the simulation's shots in flight, not Unity's Projectile instances, once fire control moves shot resolution into the sim (docs/three-gates-scope.md). Until then a Unity-side feed stands in, and it is the presentation layer's own business.
• It carries enough to aim at: where the threat is, where it is going, when it is expected to arrive, and how big it is. Not who fired it, not what it will do.

A presentation serving several capabilities

The Lariat answers absorb and grab with one object, so it owns an arbitration the single-capability presenters never needed:

• It decides what it is currently doing — idle, snapping, coiling, reeling — and what interrupts what. That decision is presentation-local.
• It may not delay or deny the simulation. The pickup completed and the damage was absorbed when the simulation says so, whether or not the whip has finished reeling. A presentation that is still animating is a presentation that is behind, never a gameplay state.
• It may refuse to show something (a second absorb mid-coil), and that refusal is cosmetic.

Open

• Where the anticipation feed lives, what publishes it today, and what publishes it after fire control.
• Whether the Lariat is one item carrying both capabilities, or a presentation shared by two items. The item data has to say which.
• The Lariat's strand: a node chain with distance and bending constraints, drawn as a tube, with the snap as a travelling kink. FieldDriver's bezier tendril (extend, envelop, pull, damped sliding base) is the existing half, and it cannot leave the field surface.