fix(agents): surface OpenAI model capacity errors

src/agents/pi-embedded-helpers.formatassistanterrortext.test.ts

@@ -64,6 +64,12 @@ describe("formatAssistantErrorText", () => {
       "The AI service is temporarily overloaded. Please try again in a moment.",
     );
   });
+  it("returns a model-switch hint for OpenAI model capacity errors", () => {
+    const msg = makeAssistantError("Selected model is at capacity. Please try a different model.");
+    expect(formatAssistantErrorText(msg)).toBe(
+      "⚠️ Selected model is at capacity. Try a different model, or wait and retry.",
+    );
+  });
   it("returns a recovery hint when tool call input is missing", () => {
     const msg = makeAssistantError("tool_use.input: Field required");
     const result = formatAssistantErrorText(msg);

src/agents/pi-embedded-helpers.sanitizeuserfacingtext.test.ts

@@ -141,6 +141,17 @@ describe("sanitizeUserFacingText", () => {
     );
   });
 
+  it("returns a model-switch hint for OpenAI model capacity errors", () => {
+    expect(
+      sanitizeUserFacingText(
+        "OpenAI error: Selected model is at capacity. Please try a different model.",
+        {
+          errorContext: true,
+        },
+      ),
+    ).toBe("⚠️ Selected model is at capacity. Try a different model, or wait and retry.");
+  });
+
   it("returns a transport-specific message for prefixed ECONNREFUSED errors", () => {
     expect(
       sanitizeUserFacingText("Error: connect ECONNREFUSED 127.0.0.1:443", {

src/agents/pi-embedded-helpers/failover-matches.test.ts

@@ -2,6 +2,7 @@ import { describe, expect, it } from "vitest";
 import {
   isAuthErrorMessage,
   isBillingErrorMessage,
+  isOverloadedErrorMessage,
   isRateLimitErrorMessage,
 } from "./failover-matches.js";
 
@@ -68,6 +69,12 @@ describe("Z.ai vendor error codes (#48988)", () => {
       expect(isRateLimitErrorMessage("rate limit exceeded")).toBe(true);
     });
 
+    it("OpenAI model-capacity text is classified as overloaded", () => {
+      expect(
+        isOverloadedErrorMessage("Selected model is at capacity. Please try a different model."),
+      ).toBe(true);
+    });
+
     it("billing still classified correctly", () => {
       expect(isBillingErrorMessage("insufficient credits")).toBe(true);
     });

src/agents/pi-embedded-helpers/failover-matches.ts

@@ -73,6 +73,7 @@ const ERROR_PATTERNS = {
   overloaded: [
     /overloaded_error|"type"\s*:\s*"overloaded_error"/i,
     "overloaded",
+    /\b(?:selected\s+)?model\s+(?:is\s+)?at capacity\b/i,
     // Match "service unavailable" only when combined with an explicit overload
     // indicator — a generic 503 from a proxy/CDN should not be classified as
     // provider-overload (#32828).

src/agents/pi-embedded-helpers/sanitize-user-facing-text.ts

@@ -34,6 +34,8 @@ export function formatBillingErrorMessage(provider?: string, model?: string): st
 export const BILLING_ERROR_USER_MESSAGE = formatBillingErrorMessage();
 
 const RATE_LIMIT_ERROR_USER_MESSAGE = "⚠️ API rate limit reached. Please try again later.";
+const MODEL_CAPACITY_ERROR_USER_MESSAGE =
+  "⚠️ Selected model is at capacity. Try a different model, or wait and retry.";
 const OVERLOADED_ERROR_USER_MESSAGE =
   "The AI service is temporarily overloaded. Please try again in a moment.";
 const FINAL_TAG_RE = /<\s*\/?\s*final\s*>/gi;
@@ -60,6 +62,7 @@ const HTTP_ERROR_HINTS = [
 ];
 const RATE_LIMIT_SPECIFIC_HINT_RE =
   /\bmin(ute)?s?\b|\bhours?\b|\bseconds?\b|\btry again in\b|\breset\b|\bplan\b|\bquota\b/i;
+const MODEL_CAPACITY_ERROR_RE = /\b(?:selected\s+)?model\s+(?:is\s+)?at capacity\b/i;
 const NON_ERROR_PROVIDER_PAYLOAD_MAX_LENGTH = 16_384;
 const NON_ERROR_PROVIDER_PAYLOAD_PREFIX_RE = /^codex\s*error(?:\s+\d{3})?[:\s-]+/i;
 
@@ -93,6 +96,9 @@ export function formatRateLimitOrOverloadedErrorCopy(raw: string): string | unde
   if (isRateLimitErrorMessage(raw)) {
     return extractProviderRateLimitMessage(raw) ?? RATE_LIMIT_ERROR_USER_MESSAGE;
   }
+  if (MODEL_CAPACITY_ERROR_RE.test(raw)) {
+    return MODEL_CAPACITY_ERROR_USER_MESSAGE;
+  }
   if (isOverloadedErrorMessage(raw)) {
     return OVERLOADED_ERROR_USER_MESSAGE;
   }

src/agents/pi-embedded-runner/run/payloads.errors.test.ts

@@ -101,6 +101,20 @@ describe("buildEmbeddedRunPayloads", () => {
     expect(payloads.some((payload) => payload.text?.includes("request_id"))).toBe(false);
   });
 
+  it("surfaces OpenAI model capacity errors instead of generic empty-response copy", () => {
+    const payloads = buildPayloads({
+      lastAssistant: makeAssistant({
+        errorMessage: "Selected model is at capacity. Please try a different model.",
+        content: [],
+      }),
+    });
+
+    expectSinglePayloadSummary(payloads, {
+      text: "⚠️ Selected model is at capacity. Try a different model, or wait and retry.",
+      isError: true,
+    });
+  });
+
   it("includes provider and model context for billing errors", () => {
     const payloads = buildPayloads({
       lastAssistant: makeAssistant({