AG-UI bridge

TL;DR

import "@gemmapod/embed/runtime"; // side-effects window.GemmaPod
// or load the IIFE via <script>

runtime.events.on("ui.event", ({ event }) => {
  const agui = GemmaPod.mapDartcUiEventToAgUi(event);
  // agui.type is PascalCase now. Payload fields unchanged.
});

That's the whole bridge.

Why a mapper instead of native support

Two decisions baked into GemmaPod that AG-UI hosts care about:

1. Field names match AG-UI on purpose. threadId, runId, messageId, toolCallId, delta, snapshot, patch — every payload field is the same name on the wire. Hosts that already destructure these field names work without changes.

2. The discriminator differs by design. DARTC frames are visible in network panels and CI logs; SCREAMING_SNAKE jumps out from surrounding JSON. AG-UI uses PascalCase to fit TypeScript convention. Neither is wrong — they serve different audiences. The mapper bridges the two.

What the mapper does

function mapDartcUiEventToAgUi(event: DartcUiEvent): AgUiEvent;

• Takes a DartcUiEvent (the typed event you get on runtime.events.on("ui.event", …)).
• Returns a new object with the type rewritten to PascalCase and all other fields preserved verbatim.
• Pure: no allocation beyond the new top-level object, no runtime state, no async.
• Defensive: unknown DARTC type values map to Raw — your AG-UI host receives a typed Raw event with the original payload nested under dartc, rather than a missing field.

Where to call it

Anywhere. Three useful spots:

In the event handler

runtime.events.on("ui.event", ({ event }) => {
  host.dispatch(GemmaPod.mapDartcUiEventToAgUi(event));
});

In a generic adapter

function toAgUi(runtime, host) {
  return runtime.events.on("ui.event", ({ event }) =>
    host.dispatch(GemmaPod.mapDartcUiEventToAgUi(event)),
  );
}

In a worker for logging / replay

self.onmessage = (e) => {
  postMessage(GemmaPod.mapDartcUiEventToAgUi(e.data));
};

What it doesn't do

• It doesn't filter or batch events. If your host expects rate-limited events, you batch.
• It doesn't validate. Send any object with a type and you get back an object with a type. Validation belongs in the consumer.
• It doesn't introspect payloads. STATE_DELTA.delta stays a JSON-Patch operation array; field names match RFC 6902.

See also

• Side-by-side example
• CopilotKit-style integration guide
• DARTC UI event reference
• AG-UI event spec