From bb99f5774e2a68427d27c3d1d8567c6e84a8e045 Mon Sep 17 00:00:00 2001
From: Yassin Kortam <yassin@berri.ai>
Date: Fri, 21 Aug 2026 12:38:24 -0700
Subject: [PATCH] fix(responses): map Bedrock Mantle context overflow to
 ContextWindowExceededError (#37862)

Mantle reports context overflow as a structured 400 validation_error rather than
the plain-text patterns Bedrock itself uses, so callers such as Claude Code that
key reactive compaction off the phrase "prompt is too long" never see it. Detect
the pattern and normalize the message to that phrase.
---
 .../exception_mapping_utils.py                | 26 +++++++++++++++++++
 .../test_exception_mapping_utils.py           | 24 +++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/litellm/litellm_core_utils/exception_mapping_utils.py b/litellm/litellm_core_utils/exception_mapping_utils.py
index ee179b582cf..4a25eb218c0 100644
--- a/litellm/litellm_core_utils/exception_mapping_utils.py
+++ b/litellm/litellm_core_utils/exception_mapping_utils.py
@@ -811,6 +811,24 @@ def _map_openai_like_exception(
             )
 
 
+_BEDROCK_MANTLE_CONTEXT_WINDOW_PATTERN: Final = re.compile(r"prompt tokens \((\d+)\) exceed model maximum \((\d+)\)")
+
+
+def _get_bedrock_mantle_context_window_message(error_str: str) -> str | None:
+    """
+    Mantle reports context overflow as a structured validation error rather than
+    the plain-text patterns Bedrock itself uses, so it needs its own detection and a
+    message clients recognize as context overflow (litellm/litellm#36546).
+    """
+    if "invalid_request_error" not in error_str and "validation_error" not in error_str:
+        return None
+    match = _BEDROCK_MANTLE_CONTEXT_WINDOW_PATTERN.search(error_str)
+    if match is None:
+        return None
+    prompt_tokens, max_tokens = match.groups()
+    return f"prompt is too long: {prompt_tokens} tokens > {max_tokens} maximum"
+
+
 def _map_bedrock_exception(
     *,
     model: str,
@@ -821,6 +839,14 @@ def _map_bedrock_exception(
     exception_provider: str,
     extra_information: str,
 ) -> None:
+    if custom_llm_provider == "bedrock_mantle":
+        mantle_context_window_message = _get_bedrock_mantle_context_window_message(error_str)
+        if mantle_context_window_message is not None:
+            raise ContextWindowExceededError(
+                message=mantle_context_window_message,
+                model=model,
+                llm_provider=custom_llm_provider,
+            )
     if (
         "too many tokens" in error_str
         or "expected maxLength:" in error_str
diff --git a/tests/test_litellm/litellm_core_utils/test_exception_mapping_utils.py b/tests/test_litellm/litellm_core_utils/test_exception_mapping_utils.py
index 904675d4adc..38f46b26eea 100644
--- a/tests/test_litellm/litellm_core_utils/test_exception_mapping_utils.py
+++ b/tests/test_litellm/litellm_core_utils/test_exception_mapping_utils.py
@@ -785,3 +785,27 @@ def test_bedrock_mantle_400_maps_to_bad_request():
 
     assert excinfo.value.status_code == 400
     assert "Invalid 'input'" in excinfo.value.message
+    assert type(excinfo.value) is litellm.BadRequestError
+
+
+def test_bedrock_mantle_context_overflow_maps_to_context_window_exceeded():
+    from litellm.llms.base_llm.chat.transformation import BaseLLMException
+
+    original_exception = BaseLLMException(
+        status_code=400,
+        message=(
+            '{"error":{"code":"validation_error",'
+            '"message":"prompt tokens (1055489) exceed model maximum (1050000) for openai.gpt-5.6-sol",'
+            '"param":null,"type":"invalid_request_error"}}'
+        ),
+    )
+
+    with pytest.raises(litellm.ContextWindowExceededError) as excinfo:
+        exception_type(
+            model="openai.gpt-5.6-sol",
+            original_exception=original_exception,
+            custom_llm_provider="bedrock_mantle",
+        )
+
+    assert excinfo.value.status_code == 400
+    assert "prompt is too long: 1055489 tokens > 1050000 maximum" in excinfo.value.message