fix: align OpenAI cache affinity and use uuidv7 session ids

packages/ai/test/openai-responses-copilot-provider.test.ts

@@ -2,7 +2,54 @@ import { afterEach, describe, expect, it, vi } from "vitest";
 import { getModel } from "../src/models.js";
 import { streamOpenAIResponses } from "../src/providers/openai-responses.js";
 
-describe("openai-responses github-copilot defaults", () => {
+type CapturedHeaders = Headers | string[][] | Record<string, string | readonly string[]> | undefined;
+
+function getHeader(headers: CapturedHeaders, name: string): string | null {
+	if (!headers) return null;
+	if (headers instanceof Headers) return headers.get(name);
+
+	const lowerName = name.toLowerCase();
+	if (Array.isArray(headers)) {
+		const match = headers.find(([key]) => key?.toLowerCase() === lowerName);
+		return match?.[1] ?? null;
+	}
+
+	for (const [key, value] of Object.entries(headers)) {
+		if (key.toLowerCase() === lowerName) return typeof value === "string" ? value : value.join(", ");
+	}
+	return null;
+}
+
+async function captureOpenAIResponseHeaders(
+	options: Parameters<typeof streamOpenAIResponses>[2],
+): Promise<{ sessionId: string | null; clientRequestId: string | null }> {
+	const captured = { sessionId: null as string | null, clientRequestId: null as string | null };
+	vi.spyOn(globalThis, "fetch").mockImplementation(async (_input, init) => {
+		captured.sessionId = getHeader(init?.headers, "session_id");
+		captured.clientRequestId = getHeader(init?.headers, "x-client-request-id");
+		return new Response("data: [DONE]\n\n", {
+			status: 200,
+			headers: { "content-type": "text/event-stream" },
+		});
+	});
+
+	const stream = streamOpenAIResponses(
+		getModel("openai", "gpt-5.4"),
+		{
+			systemPrompt: "sys",
+			messages: [{ role: "user", content: "hi", timestamp: Date.now() }],
+		},
+		{ apiKey: "test-key", ...options },
+	);
+
+	for await (const event of stream) {
+		if (event.type === "done" || event.type === "error") break;
+	}
+
+	return captured;
+}
+
+describe("openai-responses provider defaults", () => {
 	afterEach(() => {
 		vi.restoreAllMocks();
 	});
@@ -41,4 +88,28 @@ describe("openai-responses github-copilot defaults", () => {
 			reasoning: expect.anything(),
 		});
 	});
+
+	it("sets cache-affinity headers for official OpenAI Responses requests with a sessionId", async () => {
+		const captured = await captureOpenAIResponseHeaders({ sessionId: "session-123" });
+
+		expect(captured).toEqual({ sessionId: "session-123", clientRequestId: "session-123" });
+	});
+
+	it("lets explicit headers override the default OpenAI cache-affinity headers", async () => {
+		const captured = await captureOpenAIResponseHeaders({
+			sessionId: "session-123",
+			headers: {
+				session_id: "override-session",
+				"x-client-request-id": "override-request",
+			},
+		});
+
+		expect(captured).toEqual({ sessionId: "override-session", clientRequestId: "override-request" });
+	});
+
+	it("omits OpenAI cache-affinity headers when cacheRetention is none", async () => {
+		const captured = await captureOpenAIResponseHeaders({ cacheRetention: "none", sessionId: "session-123" });
+
+		expect(captured).toEqual({ sessionId: null, clientRequestId: null });
+	});
 });