handle openai websocket previous_response_not_found error

packages/ai/src/api/openai-codex-responses.ts

@@ -67,6 +67,7 @@ const REQUEST_COMPRESSION_ZSTD_LEVEL = 3;
 const CODEX_TOOL_CALL_PROVIDERS = new Set(["openai", "openai-codex", "opencode"]);
 const WEBSOCKET_MESSAGE_TOO_BIG_CLOSE_CODE = 1009;
 const WEBSOCKET_CONNECTION_LIMIT_REACHED_CODE = "websocket_connection_limit_reached";
+const PREVIOUS_RESPONSE_NOT_FOUND_CODE = "previous_response_not_found";
 
 const CODEX_RESPONSE_STATUSES = new Set<CodexResponseStatus>([
 	"completed",
@@ -273,6 +274,7 @@ export const stream: StreamFunction<"openai-codex-responses", OpenAICodexRespons
 			const httpTimeoutMs = normalizeTimeoutMs(options?.timeoutMs);
 			const websocketConnectTimeoutMs = normalizeTimeoutMs(options?.websocketConnectTimeoutMs);
 			const transport = options?.transport || "auto";
+			let startEmitted = false;
 			const websocketDisabledForSession = transport !== "sse" && isWebSocketSseFallbackActive(options?.sessionId);
 			if (websocketDisabledForSession) {
 				recordWebSocketSseFallback(options?.sessionId);
@@ -281,6 +283,7 @@ export const stream: StreamFunction<"openai-codex-responses", OpenAICodexRespons
 			if (transport !== "sse" && !websocketDisabledForSession) {
 				let websocketStarted = false;
 				let retriedWebSocketConnectionLimit = false;
+				let retriedMissingWebSocketContinuation = false;
 				while (true) {
 					websocketStarted = false;
 					try {
@@ -293,6 +296,10 @@ export const stream: StreamFunction<"openai-codex-responses", OpenAICodexRespons
 							model,
 							() => {
 								websocketStarted = true;
+								if (!startEmitted) {
+									startEmitted = true;
+									stream.push({ type: "start", partial: output });
+								}
 							},
 							httpTimeoutMs,
 							websocketConnectTimeoutMs,
@@ -312,6 +319,11 @@ export const stream: StreamFunction<"openai-codex-responses", OpenAICodexRespons
 					} catch (error) {
 						const aborted = options?.signal?.aborted;
 						const connectionLimitBeforeStart = !websocketStarted && isWebSocketConnectionLimitReachedError(error);
+						const previousResponseNotFound = isPreviousResponseNotFoundError(error);
+						if (!aborted && previousResponseNotFound && !retriedMissingWebSocketContinuation) {
+							retriedMissingWebSocketContinuation = true;
+							continue;
+						}
 						if (!aborted && connectionLimitBeforeStart && !retriedWebSocketConnectionLimit) {
 							retriedWebSocketConnectionLimit = true;
 							continue;
@@ -432,7 +444,10 @@ export const stream: StreamFunction<"openai-codex-responses", OpenAICodexRespons
 				throw new Error("No response body");
 			}
 
-			stream.push({ type: "start", partial: output });
+			if (!startEmitted) {
+				startEmitted = true;
+				stream.push({ type: "start", partial: output });
+			}
 			await processStream(response, output, stream, model, options);
 
 			if (options?.signal?.aborted) {
@@ -636,6 +651,10 @@ function isWebSocketConnectionLimitReachedError(error: unknown): boolean {
 	return error instanceof CodexApiError && error.code === WEBSOCKET_CONNECTION_LIMIT_REACHED_CODE;
 }
 
+function isPreviousResponseNotFoundError(error: unknown): boolean {
+	return error instanceof CodexApiError && error.code === PREVIOUS_RESPONSE_NOT_FOUND_CODE;
+}
+
 function extractCodexEventError(event: Record<string, unknown>): { code?: string; message?: string } {
 	const nested = event.error && typeof event.error === "object" ? (event.error as Record<string, unknown>) : undefined;
 	return {
@@ -1358,16 +1377,13 @@ function buildCachedWebSocketRequestBody(entry: CachedWebSocketConnection, body:
 
 async function* startWebSocketOutputOnFirstEvent(
 	events: AsyncIterable<ResponseStreamEvent>,
-	output: AssistantMessage,
-	stream: AssistantMessageEventStream,
 	onStart: () => void,
 ): AsyncGenerator<ResponseStreamEvent> {
 	let started = false;
 	for await (const event of events) {
 		if (!started) {
 			started = true;
 			onStart();
-			stream.push({ type: "start", partial: output });
 		}
 		yield event;
 	}
@@ -1422,8 +1438,6 @@ async function processWebSocketStream(
 		await processResponsesStream(
 			startWebSocketOutputOnFirstEvent(
 				mapCodexEvents(parseWebSocket(socket, options?.signal, idleTimeoutMs)),
-				output,
-				stream,
 				onStart,
 			),
 			output,

packages/ai/test/openai-codex-stream.test.ts

@@ -1802,6 +1802,224 @@ describe("openai-codex streaming", () => {
 		});
 	});
 
+	it.each(["websocket", "sse"] as const)(
+		"recovers a missing cached websocket continuation via %s",
+		async (recoveryTransport) => {
+			const token = mockToken();
+			const sessionId = `missing-continuation-${recoveryTransport}`;
+			const encoder = new TextEncoder();
+			const fetchMock = vi.fn(
+				async () =>
+					new Response(
+						new ReadableStream<Uint8Array>({
+							start(controller) {
+								controller.enqueue(encoder.encode(buildSSEPayload({ status: "completed" })));
+								controller.close();
+							},
+						}),
+						{ status: 200, headers: { "content-type": "text/event-stream" } },
+					),
+			);
+			vi.stubGlobal("fetch", fetchMock);
+			const sentBodies: Array<{
+				connectionId: number;
+				input: unknown[];
+				previous_response_id?: string;
+			}> = [];
+			let connections = 0;
+
+			class MockWebSocket {
+				static OPEN = 1;
+				static CLOSED = 3;
+				readyState = MockWebSocket.OPEN;
+				private readonly connectionId = ++connections;
+				private listeners = new Map<string, Set<(event: unknown) => void>>();
+
+				constructor(_url: string, _protocols?: string | string[] | { headers?: Record<string, string> }) {
+					queueMicrotask(() => this.dispatch("open", {}));
+				}
+
+				addEventListener(type: string, listener: (event: unknown) => void): void {
+					let listeners = this.listeners.get(type);
+					if (!listeners) {
+						listeners = new Set();
+						this.listeners.set(type, listeners);
+					}
+					listeners.add(listener);
+				}
+
+				removeEventListener(type: string, listener: (event: unknown) => void): void {
+					this.listeners.get(type)?.delete(listener);
+				}
+
+				send(data: string): void {
+					const body = JSON.parse(data) as { input: unknown[]; previous_response_id?: string };
+					sentBodies.push({ ...body, connectionId: this.connectionId });
+					if (sentBodies.length === 2) {
+						this.dispatchEvents([
+							{
+								type: "codex.rate_limits",
+								plan_type: "plus",
+								rate_limits: {
+									allowed: true,
+									limit_reached: false,
+									primary: {
+										used_percent: 7,
+										window_minutes: 10080,
+										reset_after_seconds: 556112,
+										reset_at: 1785269351,
+									},
+									secondary: null,
+								},
+								code_review_rate_limits: null,
+								additional_rate_limits: null,
+								credits: { has_credits: false, unlimited: false, balance: "0" },
+								promo: null,
+							},
+							{
+								type: "error",
+								status: 400,
+								error: {
+									code: "previous_response_not_found",
+									message: "Previous response with id 'resp_1' not found.",
+									param: "previous_response_id",
+								},
+							},
+						]);
+						return;
+					}
+					if (sentBodies.length === 3 && recoveryTransport === "sse") {
+						queueMicrotask(() => this.dispatch("error", { message: "retry websocket failed" }));
+						return;
+					}
+
+					const response =
+						sentBodies.length === 1
+							? { responseId: "resp_1", messageId: "msg_1", text: "Hello" }
+							: { responseId: "resp_2", messageId: "msg_2", text: "Recovered" };
+					this.dispatchEvents([
+						{ type: "response.created", response: { id: response.responseId } },
+						{
+							type: "response.output_item.added",
+							output_index: 0,
+							item: {
+								type: "message",
+								id: response.messageId,
+								role: "assistant",
+								status: "in_progress",
+								content: [],
+							},
+						},
+						{
+							type: "response.output_item.done",
+							output_index: 0,
+							item: {
+								type: "message",
+								id: response.messageId,
+								role: "assistant",
+								status: "completed",
+								content: [{ type: "output_text", text: response.text }],
+							},
+						},
+						{
+							type: "response.completed",
+							response: {
+								id: response.responseId,
+								status: "completed",
+								usage: { input_tokens: 5, output_tokens: 3, total_tokens: 8 },
+							},
+						},
+					]);
+				}
+
+				close(): void {
+					this.readyState = MockWebSocket.CLOSED;
+				}
+
+				private dispatchEvents(events: unknown[]): void {
+					queueMicrotask(() => {
+						for (const event of events) {
+							this.dispatch("message", { data: JSON.stringify(event) });
+						}
+					});
+				}
+
+				private dispatch(type: string, event: unknown): void {
+					for (const listener of this.listeners.get(type) ?? []) {
+						listener(event);
+					}
+				}
+			}
+
+			vi.stubGlobal("WebSocket", MockWebSocket);
+
+			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 firstContext: Context = {
+				systemPrompt: "You are a helpful assistant.",
+				messages: [{ role: "user", content: "Say hello", timestamp: 1 }],
+			};
+
+			const first = await streamOpenAICodexResponses(model, firstContext, {
+				apiKey: token,
+				sessionId,
+				transport: "websocket-cached",
+			}).result();
+			const secondContext: Context = {
+				systemPrompt: "You are a helpful assistant.",
+				messages: [...firstContext.messages, first, { role: "user", content: "Now finish", timestamp: 2 }],
+			};
+			const eventTypes: string[] = [];
+			const secondStream = streamOpenAICodexResponses(model, secondContext, {
+				apiKey: token,
+				sessionId,
+				transport: "websocket-cached",
+			});
+			for await (const event of secondStream) {
+				eventTypes.push(event.type);
+			}
+			const second = await secondStream.result();
+
+			expect(second.stopReason).toBe("stop");
+			expect(second.content.find((content) => content.type === "text")?.text).toBe(
+				recoveryTransport === "sse" ? "Hello" : "Recovered",
+			);
+			expect(eventTypes.filter((type) => type === "start")).toHaveLength(1);
+			expect(eventTypes).not.toContain("error");
+			expect(connections).toBe(2);
+			expect(sentBodies).toHaveLength(3);
+			expect(sentBodies.map((body) => body.connectionId)).toEqual([1, 1, 2]);
+			expect(sentBodies[1].previous_response_id).toBe("resp_1");
+			expect(sentBodies[1].input).toEqual([{ role: "user", content: [{ type: "input_text", text: "Now finish" }] }]);
+			expect(sentBodies[2].previous_response_id).toBeUndefined();
+			expect(sentBodies[2].input).toHaveLength(3);
+			expect(sentBodies[2].input.at(-1)).toEqual({
+				role: "user",
+				content: [{ type: "input_text", text: "Now finish" }],
+			});
+			expect(fetchMock).toHaveBeenCalledTimes(recoveryTransport === "sse" ? 1 : 0);
+			expect(getOpenAICodexWebSocketDebugStats(sessionId)).toMatchObject({
+				requests: 3,
+				connectionsCreated: 2,
+				connectionsReused: 1,
+				fullContextRequests: 2,
+				deltaRequests: 1,
+				websocketFailures: recoveryTransport === "sse" ? 1 : 0,
+				sseFallbacks: recoveryTransport === "sse" ? 1 : 0,
+			});
+		},
+	);
+
 	it.each([
 		["retry-after-ms", () => ({ "content-type": "application/json", "retry-after-ms": "1500" }), 1500],
 		["retry-after seconds", () => ({ "content-type": "application/json", "retry-after": "60" }), 60_000],