Add native LLM core foundation (#24712)

packages/llm/src/protocols/openai-compatible-chat.ts

@@ -0,0 +1,28 @@
+import { Route, type RouteRoutedModelInput } from "../route/client"
+import { Endpoint } from "../route/endpoint"
+import { Framing } from "../route/framing"
+import * as OpenAIChat from "./openai-chat"
+
+const ADAPTER = "openai-compatible-chat"
+
+export type OpenAICompatibleChatModelInput = Omit<RouteRoutedModelInput, "baseURL"> & {
+  readonly baseURL: string
+}
+
+/**
+ * Route for non-OpenAI providers that expose an OpenAI Chat-compatible
+ * `/chat/completions` endpoint. Reuses `OpenAIChat.protocol` end-to-end and
+ * overrides only the route id so providers can be resolved per-family without
+ * colliding with native OpenAI. The model carries the host on `baseURL`,
+ * supplied by whichever profile/provider helper builds it.
+ */
+export const route = Route.make({
+  id: ADAPTER,
+  protocol: OpenAIChat.protocol,
+  endpoint: Endpoint.path("/chat/completions"),
+  framing: Framing.sse,
+})
+
+export const model = Route.model<OpenAICompatibleChatModelInput>(route)
+
+export * as OpenAICompatibleChat from "./openai-compatible-chat"