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

packages/ai/src/providers/github-copilot-headers.ts

@@ -0,0 +1,59 @@
+import type { Message } from "../types.js";
+
+/**
+ * Infer whether the current request to Copilot is user-initiated or agent-initiated.
+ * Accepts `unknown[]` because providers may pass pre-converted message shapes.
+ */
+export function inferCopilotInitiator(messages: unknown[]): "user" | "agent" {
+	if (messages.length === 0) return "user";
+
+	const last = messages[messages.length - 1] as Record<string, unknown>;
+	const role = last.role as string | undefined;
+	if (!role) return "user";
+
+	if (role !== "user") return "agent";
+
+	// Check if last content block is a tool_result (Anthropic-converted shape)
+	const content = last.content;
+	if (Array.isArray(content) && content.length > 0) {
+		const lastBlock = content[content.length - 1] as Record<string, unknown>;
+		if (lastBlock.type === "tool_result") {
+			return "agent";
+		}
+	}
+
+	return "user";
+}
+
+/** Check whether any message in the conversation contains image content. */
+export function hasCopilotVisionInput(messages: Message[]): boolean {
+	return messages.some((msg) => {
+		if (msg.role === "user" && Array.isArray(msg.content)) {
+			return msg.content.some((c) => c.type === "image");
+		}
+		if (msg.role === "toolResult" && Array.isArray(msg.content)) {
+			return msg.content.some((c) => c.type === "image");
+		}
+		return false;
+	});
+}
+
+/**
+ * Build dynamic Copilot headers that vary per-request.
+ * Static headers (User-Agent, Editor-Version, etc.) come from model.headers.
+ */
+export function buildCopilotDynamicHeaders(params: {
+	messages: unknown[];
+	hasImages: boolean;
+}): Record<string, string> {
+	const headers: Record<string, string> = {
+		"X-Initiator": inferCopilotInitiator(params.messages),
+		"Openai-Intent": "conversation-edits",
+	};
+
+	if (params.hasImages) {
+		headers["Copilot-Vision-Request"] = "true";
+	}
+
+	return headers;
+}