From 421e2ceeee4a7275aa4e4ebbe5ae00f92b7d4db2 Mon Sep 17 00:00:00 2001
From: Mason Daugherty <mason@langchain.dev>
Date: Fri, 14 Nov 2025 09:05:29 -0500
Subject: [PATCH] fix(core): don't mask exceptions (#33959)

---
 .../language_models/chat_models.py            |  5 +-
 .../language_models/chat_models/test_base.py  | 91 +++++++++++++++++++
 2 files changed, 95 insertions(+), 1 deletion(-)

diff --git a/libs/core/langchain_core/language_models/chat_models.py b/libs/core/langchain_core/language_models/chat_models.py
index f37113b4661..bfd37ea5883 100644
--- a/libs/core/langchain_core/language_models/chat_models.py
+++ b/libs/core/langchain_core/language_models/chat_models.py
@@ -91,7 +91,10 @@ def _generate_response_from_error(error: BaseException) -> list[ChatGeneration]:
             try:
                 metadata["body"] = response.json()
             except Exception:
-                metadata["body"] = getattr(response, "text", None)
+                try:
+                    metadata["body"] = getattr(response, "text", None)
+                except Exception:
+                    metadata["body"] = None
         if hasattr(response, "headers"):
             try:
                 metadata["headers"] = dict(response.headers)
diff --git a/libs/core/tests/unit_tests/language_models/chat_models/test_base.py b/libs/core/tests/unit_tests/language_models/chat_models/test_base.py
index b20623ad6fb..e0a2cb291c9 100644
--- a/libs/core/tests/unit_tests/language_models/chat_models/test_base.py
+++ b/libs/core/tests/unit_tests/language_models/chat_models/test_base.py
@@ -18,6 +18,7 @@ from langchain_core.language_models import (
     ParrotFakeChatModel,
 )
 from langchain_core.language_models._utils import _normalize_messages
+from langchain_core.language_models.chat_models import _generate_response_from_error
 from langchain_core.language_models.fake_chat_models import (
     FakeListChatModelError,
     GenericFakeChatModel,
@@ -1234,3 +1235,93 @@ def test_model_profiles() -> None:
     model = MyModel(messages=iter([]))
     profile = model.profile
     assert profile
+
+
+class MockResponse:
+    """Mock response for testing _generate_response_from_error."""
+
+    def __init__(
+        self,
+        status_code: int = 400,
+        headers: dict[str, str] | None = None,
+        json_data: dict[str, Any] | None = None,
+        json_raises: type[Exception] | None = None,
+        text_raises: type[Exception] | None = None,
+    ):
+        self.status_code = status_code
+        self.headers = headers or {}
+        self._json_data = json_data
+        self._json_raises = json_raises
+        self._text_raises = text_raises
+
+    def json(self) -> dict[str, Any]:
+        if self._json_raises:
+            msg = "JSON parsing failed"
+            raise self._json_raises(msg)
+        return self._json_data or {}
+
+    @property
+    def text(self) -> str:
+        if self._text_raises:
+            msg = "Text access failed"
+            raise self._text_raises(msg)
+        return ""
+
+
+class MockAPIError(Exception):
+    """Mock API error with response attribute."""
+
+    def __init__(self, message: str, response: MockResponse | None = None):
+        super().__init__(message)
+        self.message = message
+        if response is not None:
+            self.response = response
+
+
+def test_generate_response_from_error_with_valid_json() -> None:
+    """Test `_generate_response_from_error` with valid JSON response."""
+    response = MockResponse(
+        status_code=400,
+        headers={"content-type": "application/json"},
+        json_data={"error": {"message": "Bad request", "type": "invalid_request"}},
+    )
+    error = MockAPIError("API Error", response=response)
+
+    generations = _generate_response_from_error(error)
+
+    assert len(generations) == 1
+    generation = generations[0]
+    assert isinstance(generation, ChatGeneration)
+    assert isinstance(generation.message, AIMessage)
+    assert generation.message.content == ""
+
+    metadata = generation.message.response_metadata
+    assert metadata["body"] == {
+        "error": {"message": "Bad request", "type": "invalid_request"}
+    }
+    assert metadata["headers"] == {"content-type": "application/json"}
+    assert metadata["status_code"] == 400
+
+
+def test_generate_response_from_error_handles_streaming_response_failure() -> None:
+    # Simulates scenario where accessing response.json() or response.text
+    # raises ResponseNotRead on streaming responses
+    response = MockResponse(
+        status_code=400,
+        headers={"content-type": "application/json"},
+        json_raises=Exception,  # Simulates ResponseNotRead or similar
+        text_raises=Exception,
+    )
+    error = MockAPIError("API Error", response=response)
+
+    # This should NOT raise an exception, but should handle it gracefully
+    generations = _generate_response_from_error(error)
+
+    assert len(generations) == 1
+    generation = generations[0]
+    metadata = generation.message.response_metadata
+
+    # When both fail, body should be None instead of raising an exception
+    assert metadata["body"] is None
+    assert metadata["headers"] == {"content-type": "application/json"}
+    assert metadata["status_code"] == 400