From 39c1f96fc22b1ac187206e06eede7071ac0dfec6 Mon Sep 17 00:00:00 2001
From: Kaiyi <me@kaiyi.cool>
Date: Thu, 5 Mar 2026 18:26:13 +0800
Subject: [PATCH] fix(embedded): classify model_context_window_exceeded as
 context overflow error

---
 ...embedded-helpers.isbillingerrormessage.test.ts | 15 +++++++++++++++
 src/agents/pi-embedded-helpers/errors.ts          |  3 +++
 2 files changed, 18 insertions(+)

diff --git a/src/agents/pi-embedded-helpers.isbillingerrormessage.test.ts b/src/agents/pi-embedded-helpers.isbillingerrormessage.test.ts
index c9d073ce8c9..8d9c678035a 100644
--- a/src/agents/pi-embedded-helpers.isbillingerrormessage.test.ts
+++ b/src/agents/pi-embedded-helpers.isbillingerrormessage.test.ts
@@ -269,6 +269,21 @@ describe("isContextOverflowError", () => {
     }
   });
 
+  it("matches model_context_window_exceeded stop reason surfaced by pi-ai", () => {
+    // Anthropic API (and some OpenAI-compatible providers like ZhipuAI/GLM) return
+    // stop_reason: "model_context_window_exceeded" when the context window is hit.
+    // The pi-ai library surfaces this as "Unhandled stop reason: model_context_window_exceeded".
+    const samples = [
+      "Unhandled stop reason: model_context_window_exceeded",
+      "model_context_window_exceeded",
+      "context_window_exceeded",
+      "Unhandled stop reason: context_window_exceeded",
+    ];
+    for (const sample of samples) {
+      expect(isContextOverflowError(sample)).toBe(true);
+    }
+  });
+
   it("matches Chinese context overflow error messages from proxy providers", () => {
     const samples = [
       "上下文过长",
diff --git a/src/agents/pi-embedded-helpers/errors.ts b/src/agents/pi-embedded-helpers/errors.ts
index 30112b74fb6..630071df451 100644
--- a/src/agents/pi-embedded-helpers/errors.ts
+++ b/src/agents/pi-embedded-helpers/errors.ts
@@ -105,6 +105,9 @@ export function isContextOverflowError(errorMessage?: string): boolean {
     (lower.includes("max_tokens") && lower.includes("exceed") && lower.includes("context")) ||
     (lower.includes("input length") && lower.includes("exceed") && lower.includes("context")) ||
     (lower.includes("413") && lower.includes("too large")) ||
+    // Anthropic API and OpenAI-compatible providers (e.g. ZhipuAI/GLM) return this stop reason
+    // when the context window is exceeded. pi-ai surfaces it as "Unhandled stop reason: model_context_window_exceeded".
+    lower.includes("context_window_exceeded") ||
     // Chinese proxy error messages for context overflow
     errorMessage.includes("上下文过长") ||
     errorMessage.includes("上下文超出") ||