import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
import { getModel } from "../src/models.js";
import { streamOpenAICompletions } from "../src/providers/openai-completions.js";
import type { Model } from "../src/types.js";
interface FakeOpenAIClientOptions {
apiKey: string;
baseURL: string;
dangerouslyAllowBrowser: boolean;
defaultHeaders?: Record<string, string>;
}
interface CapturedCompletionsPayload {
prompt_cache_key?: string;
prompt_cache_retention?: "24h" | "in-memory" | null;
}
const mockState = vi.hoisted(() => ({
lastParams: undefined as CapturedCompletionsPayload | undefined,
lastClientOptions: undefined as FakeOpenAIClientOptions | undefined,
}));
vi.mock("openai", () => {
class FakeOpenAI {
chat = {
completions: {
create: (params: CapturedCompletionsPayload) => {
mockState.lastParams = params;
const stream = {
async *[Symbol.asyncIterator]() {
yield {
choices: [{ delta: {}, finish_reason: "stop" }],
usage: {
prompt_tokens: 1,
completion_tokens: 1,
prompt_tokens_details: { cached_tokens: 0 },
completion_tokens_details: { reasoning_tokens: 0 },
},
};
},
};
const promise = Promise.resolve(stream) as Promise<typeof stream> & {
withResponse: () => Promise<{
data: typeof stream;
response: { status: number; headers: Headers };
}>;
};
promise.withResponse = async () => ({
data: stream,
response: { status: 200, headers: new Headers() },
});
return promise;
},
},
};
constructor(options: FakeOpenAIClientOptions) {
mockState.lastClientOptions = options;
}
}
return { default: FakeOpenAI };
});
describe("openai-completions prompt caching", () => {
const originalEnv = process.env.PI_CACHE_RETENTION;
beforeEach(() => {
mockState.lastParams = undefined;
mockState.lastClientOptions = undefined;
delete process.env.PI_CACHE_RETENTION;
});
afterEach(() => {
if (originalEnv === undefined) {
delete process.env.PI_CACHE_RETENTION;
} else {
process.env.PI_CACHE_RETENTION = originalEnv;
}
});
function createModel(overrides: Partial<Model<"openai-completions">> = {}): Model<"openai-completions"> {
const { compat: _compat, ...baseModel } = getModel("openai", "gpt-4o-mini");
return {
...(baseModel as Omit<Model<"openai-completions">, "api">),
api: "openai-completions",
...overrides,
};
}
async function captureRequest(
options?: {
cacheRetention?: "none" | "short" | "long";
sessionId?: string;
headers?: Record<string, string>;
},
model: Model<"openai-completions"> = createModel(),
) {
await streamOpenAICompletions(
model,
{
systemPrompt: "sys",
messages: [{ role: "user", content: "hi", timestamp: Date.now() }],
},
{ apiKey: "test-key", ...options },
).result();
return {
payload: mockState.lastParams,
headers: mockState.lastClientOptions?.defaultHeaders ?? {},
};
}
it("sets prompt_cache_key for direct OpenAI requests when caching is enabled", async () => {
const { payload } = await captureRequest({ sessionId: "session-123" });
expect(payload?.prompt_cache_key).toBe("session-123");
expect(payload?.prompt_cache_retention).toBeUndefined();
});
it("sets prompt_cache_retention to 24h for direct OpenAI requests when cacheRetention is long", async () => {
const { payload } = await captureRequest({ cacheRetention: "long", sessionId: "session-456" });
expect(payload?.prompt_cache_key).toBe("session-456");
expect(payload?.prompt_cache_retention).toBe("24h");
});
it("omits prompt cache fields when cacheRetention is none", async () => {
const { payload } = await captureRequest({ cacheRetention: "none", sessionId: "session-789" });
expect(payload?.prompt_cache_key).toBeUndefined();
expect(payload?.prompt_cache_retention).toBeUndefined();
});
it("omits prompt cache fields for non-OpenAI base URLs without compatible long retention", async () => {
const model = createModel({
baseUrl: "https://proxy.example.com/v1",
compat: { supportsLongCacheRetention: false },
});
const { payload } = await captureRequest({ cacheRetention: "long", sessionId: "session-proxy" }, model);
expect(payload?.prompt_cache_key).toBeUndefined();
expect(payload?.prompt_cache_retention).toBeUndefined();
});
it("uses PI_CACHE_RETENTION for direct OpenAI requests", async () => {
process.env.PI_CACHE_RETENTION = "long";
const { payload } = await captureRequest({ sessionId: "session-env" });
expect(payload?.prompt_cache_key).toBe("session-env");
expect(payload?.prompt_cache_retention).toBe("24h");
});
it("sends known session-affinity headers when compat.sendSessionAffinityHeaders is enabled", async () => {
const model = createModel({
baseUrl: "https://proxy.example.com/v1",
compat: { sendSessionAffinityHeaders: true },
});
const { headers } = await captureRequest({ sessionId: "session-affinity" }, model);
expect(headers.session_id).toBe("session-affinity");
expect(headers["x-client-request-id"]).toBe("session-affinity");
expect(headers["x-session-affinity"]).toBe("session-affinity");
});
it("omits session-affinity headers when cacheRetention is none", async () => {
const model = createModel({
baseUrl: "https://proxy.example.com/v1",
compat: { sendSessionAffinityHeaders: true },
});
const { headers } = await captureRequest({ cacheRetention: "none", sessionId: "session-affinity" }, model);
expect(headers.session_id).toBeUndefined();
expect(headers["x-client-request-id"]).toBeUndefined();
expect(headers["x-session-affinity"]).toBeUndefined();
});
it("lets explicit headers override generated session-affinity headers", async () => {
const model = createModel({
baseUrl: "https://proxy.example.com/v1",
compat: { sendSessionAffinityHeaders: true },
});
const { headers } = await captureRequest(
{
sessionId: "session-affinity",
headers: {
session_id: "override-session",
"x-client-request-id": "override-request",
"x-session-affinity": "override-affinity",
},
},
model,
);
expect(headers.session_id).toBe("override-session");
expect(headers["x-client-request-id"]).toBe("override-request");
expect(headers["x-session-affinity"]).toBe("override-affinity");
});
});