feat(ai): use zstd compression for codex sse transport

2026-06-30 14:29:51 +02:00
parent a3cc169d97
commit 0ac3cfe09b
3 changed files with 138 additions and 4 deletions
@@ -1,6 +1,7 @@
 import { mkdtempSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
+import { zstdDecompressSync } from "node:zlib";
 import { afterEach, describe, expect, it, vi } from "vitest";
 import {
 	getOpenAICodexWebSocketDebugStats,
@@ -32,6 +33,16 @@ function mockToken(): string {
 	return `aaa.${payload}.bbb`;
 }

+function decodeCodexRequestBody(body: RequestInit["body"] | undefined): Record<string, unknown> | null {
+	if (typeof body === "string") {
+		return JSON.parse(body) as Record<string, unknown>;
+	}
+	if (body instanceof Uint8Array) {
+		return JSON.parse(Buffer.from(zstdDecompressSync(body)).toString("utf8")) as Record<string, unknown>;
+	}
+	return null;
+}
+
 function buildSSEPayload({
 	status,
 	includeDone = false,
@@ -541,7 +552,7 @@ describe("openai-codex streaming", () => {
 				expect(headers?.get("x-client-request-id")).toBe(sessionId);

 				// Verify sessionId is set in request body as prompt_cache_key
-				const body = typeof init?.body === "string" ? (JSON.parse(init.body) as Record<string, unknown>) : null;
+				const body = decodeCodexRequestBody(init?.body);
 				expect(body?.prompt_cache_key).toBe(sessionId);

 				return new Response(stream, {
@@ -649,7 +660,7 @@ describe("openai-codex streaming", () => {
 				return new Response("PROMPT", { status: 200, headers: { etag: '"etag"' } });
 			}
 			if (url === "https://chatgpt.com/backend-api/codex/responses") {
-				const body = typeof init?.body === "string" ? (JSON.parse(init.body) as Record<string, unknown>) : null;
+				const body = decodeCodexRequestBody(init?.body);
 				requestedReasoning = body?.reasoning;
 				return new Response(stream, {
 					status: 200,
@@ -746,7 +757,7 @@ describe("openai-codex streaming", () => {
 				return new Response("PROMPT", { status: 200, headers: { etag: '"etag"' } });
 			}
 			if (url === "https://chatgpt.com/backend-api/codex/responses") {
-				const body = typeof init?.body === "string" ? (JSON.parse(init.body) as Record<string, unknown>) : null;
+				const body = decodeCodexRequestBody(init?.body);
 				requestedReasoning = body?.reasoning;

 				return new Response(stream, {
@@ -1654,6 +1665,79 @@ describe("openai-codex streaming", () => {
 		expect(codexRequests).toBe(2);
 	});

+	it("zstd-compresses SSE request bodies", async () => {
+		const token = mockToken();
+		const encoder = new TextEncoder();
+		const sse = buildSSEPayload({ status: "completed" });
+
+		let capturedEncoding: string | null = null;
+		let capturedBody: Uint8Array | string | undefined;
+
+		const fetchMock = vi.fn(async (input: string | URL, init?: RequestInit) => {
+			const url = typeof input === "string" ? input : input.toString();
+			if (url !== "https://chatgpt.com/backend-api/codex/responses") {
+				throw new Error(`Unexpected URL: ${url}`);
+			}
+			const headers = init?.headers instanceof Headers ? init.headers : undefined;
+			capturedEncoding = headers?.get("content-encoding") ?? null;
+			capturedBody = init?.body as Uint8Array | string | undefined;
+			return new Response(
+				new ReadableStream<Uint8Array>({
+					start(controller) {
+						controller.enqueue(encoder.encode(sse));
+						controller.close();
+					},
+				}),
+				{ status: 200, headers: { "content-type": "text/event-stream" } },
+			);
+		});
+		vi.stubGlobal("fetch", fetchMock);
+
+		const model: Model<"openai-codex-responses"> = {
+			id: "gpt-5.1-codex",
+			name: "GPT-5.1 Codex",
+			api: "openai-codex-responses",
+			provider: "openai-codex",
+			baseUrl: "https://chatgpt.com/backend-api",
+			reasoning: true,
+			input: ["text"],
+			cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+			contextWindow: 400000,
+			maxTokens: 128000,
+		};
+
+		const largeText = "compress me ".repeat(400);
+		await streamOpenAICodexResponses(
+			model,
+			{
+				systemPrompt: "You are a helpful assistant.",
+				messages: [{ role: "user", content: largeText, timestamp: 1 }],
+			},
+			{ apiKey: token, transport: "sse" },
+		).result();
+
+		expect(capturedEncoding).toBe("zstd");
+		expect(capturedBody).toBeInstanceOf(Uint8Array);
+		const decoded = JSON.parse(Buffer.from(zstdDecompressSync(capturedBody as Uint8Array)).toString("utf8")) as {
+			input: Array<{ content: Array<{ text: string }> }>;
+		};
+		expect(decoded.input[0].content[0].text).toBe(largeText);
+
+		capturedEncoding = null;
+		capturedBody = undefined;
+		await streamOpenAICodexResponses(
+			model,
+			{
+				systemPrompt: "You are a helpful assistant.",
+				messages: [{ role: "user", content: "hi", timestamp: 1 }],
+			},
+			{ apiKey: token, transport: "sse" },
+		).result();
+
+		expect(capturedEncoding).toBe("zstd");
+		expect(capturedBody).toBeInstanceOf(Uint8Array);
+	});
+
 	it("uses exponential backoff across repeated SSE retries without retry headers", async () => {
 		vi.useFakeTimers();
 		vi.setSystemTime(new Date("2026-05-13T00:00:00Z"));