Add native LLM core foundation (#24712)

packages/llm/src/providers/github-copilot.ts

@@ -0,0 +1,48 @@
+import { Route } from "../route/client"
+import type { ModelInput } from "../llm"
+import { Provider } from "../provider"
+import { ProviderID, type ModelID } from "../schema"
+import * as OpenAIChat from "../protocols/openai-chat"
+import * as OpenAIResponses from "../protocols/openai-responses"
+import { withOpenAIOptions, type OpenAIProviderOptionsInput } from "./openai-options"
+
+export const id = ProviderID.make("github-copilot")
+
+// GitHub Copilot has no canonical public URL — callers (opencode, etc.) must
+// supply `baseURL` explicitly.
+export type ModelOptions = Omit<ModelInput, "id" | "provider" | "route"> & {
+  readonly providerOptions?: OpenAIProviderOptionsInput
+}
+type CopilotModelInput = ModelOptions & Pick<ModelInput, "id">
+
+export const shouldUseResponsesApi = (modelID: string | ModelID) => {
+  const model = String(modelID)
+  const match = /^gpt-(\d+)/.exec(model)
+  if (!match) return false
+  return Number(match[1]) >= 5 && !model.startsWith("gpt-5-mini")
+}
+
+export const routes = [OpenAIResponses.route, OpenAIChat.route]
+
+const mapInput = (input: CopilotModelInput) => withOpenAIOptions(input.id, input)
+
+const chatModel = Route.model<CopilotModelInput>(OpenAIChat.route, { provider: id }, { mapInput })
+const responsesModel = Route.model<CopilotModelInput>(OpenAIResponses.route, { provider: id }, { mapInput })
+
+export const responses = (modelID: string | ModelID, options: ModelOptions) =>
+  responsesModel({ ...options, id: modelID })
+
+export const chat = (modelID: string | ModelID, options: ModelOptions) => chatModel({ ...options, id: modelID })
+
+export const model = (modelID: string | ModelID, options: ModelOptions) => {
+  const create = shouldUseResponsesApi(modelID) ? responsesModel : chatModel
+  return create({ ...options, id: modelID })
+}
+
+export const provider = Provider.make({
+  id,
+  model,
+  apis: { responses, chat },
+})
+
+export const apis = provider.apis