fix(ai): honor Retry-After when retry-after-ms is unparseable (#111353)

* fix(ai): honor Retry-After when retry-after-ms is unparseable

The ChatGPT Responses retry path returned as soon as `retry-after-ms` was
present, so a malformed or empty value discarded a valid `Retry-After`
header sent alongside it and the client fell back to blind exponential
backoff. The sibling parser in `provider-transport-fetch.ts` treats the
two headers as ordered preferences and falls through on a parse failure;
this aligns the Responses path with that contract.

* test(ai): deduplicate retry header coverage

---------

Co-authored-by: Peter Steinberger <steipete@gmail.com>

packages/ai/src/providers/openai-chatgpt-responses.retry.test.ts

@@ -98,6 +98,38 @@ describe("streamOpenAICodexResponses retry classification", () => {
     expect(fetchMock).toHaveBeenCalledTimes(2);
   });
 
+  it.each([
+    { label: "unparseable", retryAfterMs: "not-a-number" },
+    { label: "empty", retryAfterMs: "" },
+  ])("honors retry-after when retry-after-ms is $label", async ({ retryAfterMs }) => {
+    const fetchMock = vi
+      .fn<typeof fetch>()
+      .mockResolvedValueOnce(
+        new Response("rate limited", {
+          status: 429,
+          headers: { "retry-after-ms": retryAfterMs, "retry-after": "7" },
+        }),
+      )
+      .mockRejectedValueOnce(new Error("usage limit: stop after retry delay"));
+    vi.stubGlobal("fetch", fetchMock);
+    const setTimeoutSpy = vi
+      .spyOn(globalThis, "setTimeout")
+      .mockImplementation((callback: TimerHandler) => {
+        if (typeof callback === "function") {
+          callback();
+        }
+        return 0 as unknown as ReturnType<typeof setTimeout>;
+      });
+
+    await streamOpenAICodexResponses(model, context, {
+      apiKey: jwt,
+      transport: "sse",
+    }).result();
+
+    expect(fetchMock).toHaveBeenCalledTimes(2);
+    expect(setTimeoutSpy).toHaveBeenCalledWith(expect.any(Function), 7_000);
+  });
+
   it("does not retry a bodyless 304 response", async () => {
     const fetchMock = vi
       .fn<typeof fetch>()

packages/ai/src/providers/openai-chatgpt-responses.ts

@@ -147,12 +147,12 @@ function isRetryableError(status: number, errorText: string): boolean {
 function resolveHttpRetryDelayMs(response: Response, attempt: number): number {
   const fallbackMs = BASE_DELAY_MS * 2 ** attempt;
   const retryAfterMs = response.headers.get("retry-after-ms");
-  if (retryAfterMs !== null) {
+  if (retryAfterMs) {
     const trimmed = retryAfterMs.trim();
     const millis = Number(trimmed);
-    return /^\d+(?:\.\d+)?$/.test(trimmed) && Number.isFinite(millis)
-      ? (clampTimerTimeoutMs(millis, 0) ?? fallbackMs)
-      : fallbackMs;
+    if (/^\d+(?:\.\d+)?$/.test(trimmed) && Number.isFinite(millis)) {
+      return clampTimerTimeoutMs(millis, 0) ?? fallbackMs;
+    }
   }
 
   const retryAfter = response.headers.get("retry-after");