feat(ai): route copilot claude via anthropic messages api

packages/ai/scripts/generate-models.ts

@@ -519,13 +519,21 @@ async function loadModelsDevData(): Promise<Model<any>[]> {
 				if (m.tool_call !== true) continue;
 				if (m.status === "deprecated") continue;
 
+				// Claude 4.x models route to Anthropic Messages API
+				const isCopilotClaude4 = /^claude-(haiku|sonnet|opus)-4([.\-]|$)/.test(modelId);
 				// gpt-5 models require responses API, others use completions
 				const needsResponsesApi = modelId.startsWith("gpt-5") || modelId.startsWith("oswe");
 
+				const api: Api = isCopilotClaude4
+					? "anthropic-messages"
+					: needsResponsesApi
+						? "openai-responses"
+						: "openai-completions";
+
 				const copilotModel: Model<any> = {
 					id: modelId,
 					name: m.name || modelId,
-					api: needsResponsesApi ? "openai-responses" : "openai-completions",
+					api,
 					provider: "github-copilot",
 					baseUrl: "https://api.individual.githubcopilot.com",
 					reasoning: m.reasoning === true,
@@ -540,13 +548,13 @@ async function loadModelsDevData(): Promise<Model<any>[]> {
 					maxTokens: m.limit?.output || 8192,
 					headers: { ...COPILOT_STATIC_HEADERS },
 					// compat only applies to openai-completions
-					...(needsResponsesApi ? {} : {
+					...(api === "openai-completions" ? {
 						compat: {
 							supportsStore: false,
 							supportsDeveloperRole: false,
 							supportsReasoningEffort: false,
 						},
-					}),
+					} : {}),
 				};
 
 				models.push(copilotModel);