fix(codex): harden streaming timeouts + Responses terminal events

Raise stall/connect timeouts to 60s (configurable per-provider), accept
codex response.done, and always emit a terminal response.failed + [DONE]
for Responses passthrough when a stream closes, stalls, or aborts before
a terminal event — preventing codex clients from hanging.

Co-authored-by: jonathanli12 <jonathanli12@users.noreply.github.com>
Co-authored-by: rifuki <rifuki@users.noreply.github.com>
Co-authored-by: nguyenha935 <nguyenha935@users.noreply.github.com>
Co-authored-by: trananhtung <trananhtung@users.noreply.github.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

open-sse/utils/responsesStreamHelpers.js

@@ -0,0 +1,49 @@
+// Helpers for OpenAI Responses API streaming termination + event framing
+import { FORMATS } from "../translator/formats.js";
+import { formatSSE } from "./streamHelpers.js";
+
+// Responses API events that signal the stream has reached a terminal state
+const OPENAI_RESPONSES_TERMINAL_EVENTS = new Set([
+  "response.completed",
+  "response.failed",
+  "error"
+]);
+
+export function getOpenAIResponsesEventName(eventName, chunk) {
+  if (eventName) return eventName;
+  if (chunk && typeof chunk.type === "string") return chunk.type;
+  return null;
+}
+
+export function isOpenAIResponsesTerminalEvent(eventName, chunk) {
+  const type = getOpenAIResponsesEventName(eventName, chunk);
+  if (OPENAI_RESPONSES_TERMINAL_EVENTS.has(type)) return true;
+  const status = chunk?.response?.status;
+  return status === "completed" || status === "failed";
+}
+
+const sharedEncoder = new TextEncoder();
+
+// Encoded response.failed + [DONE] payload for aborted/stalled Responses passthrough streams
+export function buildAbortedResponsesTerminalBytes() {
+  return sharedEncoder.encode(`${formatIncompleteOpenAIResponsesStreamFailure()}data: [DONE]\n\n`);
+}
+
+// Synthesize a response.failed event for streams that close without a terminal event
+export function formatIncompleteOpenAIResponsesStreamFailure() {
+  return formatSSE({
+    event: "response.failed",
+    data: {
+      type: "response.failed",
+      response: {
+        id: `resp_${Date.now()}`,
+        status: "failed",
+        error: {
+          type: "stream_error",
+          code: "stream_disconnected",
+          message: "stream closed before response.completed"
+        }
+      }
+    }
+  }, FORMATS.OPENAI_RESPONSES);
+}