The bridge model

The bridge connects your Unity game to your Solid UI. You define it in C#; Loom generates matching TypeScript types.

Health belongs in state so the UI can read it after a reload. A damage flash belongs in an event because replaying it after a reload would be misleading. Use an action for a request from the UI, such as clicking Heal.

Define the bridge

using Loom;

[Bridge]
public partial class UIBridge : LoomBridgeBase
{
    public int Health { get; set; } = 100;

    [BridgeAction]
    public void Heal()
    {
        Health = 100;
    }

    public Event<DamageEvent> TookDamage { get; } = new();
}

public sealed class DamageEvent
{
    public int Amount { get; set; }
}

The class must be partial and inherit LoomBridgeBase. Loom allows one [Bridge] root per project. Group related values in nested state objects, such as Player or Inventory.

Public properties are state; public Event<T> properties are events. Only methods tagged [BridgeAction] are callable from the UI. The attribute also works on methods of nested state DTOs.

Read and call from Solid

Inside a component under BridgeProvider:

import { useBridge } from '@loomgui/bridge';

export function HealthPanel() {
  const bridge = useBridge();
  return (
    <div>
      <span>{bridge.health}</span>
      <button onClick={() => void bridge.heal()}>Heal</button>
    </div>
  );
}

C# assignments update the UI. Names become camelCase, and action calls always return promises. The starter configures the provider for you; see UI startup APIs for its contract.

Control exposed members

Use [BridgeIgnore] to exclude a public property from the bridge:

[BridgeIgnore]
public string InternalDebugName { get; set; } = "";

Use [BridgeName] when an exposed name must differ from the C# name:

[BridgeName("hp")]
public int Health { get; set; }

Change the contract

Stop Play mode before changing members, DTOs, enum values, or action signatures. Loom automatically regenerates the UI contract after Unity recompiles C#. Update UI/src/bridge.ts mocks to match, and restart an already running dev server. Do not hand-edit files in UI/generated/.

Continue with State and collections, Actions, Events, and DTO rules.