diff --git a/litellm/litellm_core_utils/exception_mapping_utils.py b/litellm/litellm_core_utils/exception_mapping_utils.py
index 70374f87b99..e9e946a4e0d 100644
--- a/litellm/litellm_core_utils/exception_mapping_utils.py
+++ b/litellm/litellm_core_utils/exception_mapping_utils.py
@@ -91,6 +91,7 @@ class ExceptionCheckers:
             "`inputs` tokens + `max_new_tokens` must be",
             "exceeds the available context size",  # llama.cpp/Lemonade
             "exceeds the maximum number of tokens allowed",  # Gemini
+            "prompt is too long",
         ]
         for substring in known_exception_substrings:
             if substring in _error_str_lowercase:
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 8e89180a9e4..430b22ca607 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
@@ -406,6 +406,24 @@ def test_anthropic_context_window_error_mapping(error_message):
     assert excinfo.value.llm_provider == "anthropic"
 
 
+def test_vertex_ai_anthropic_context_window_error_mapping():
+    error_message = (
+        '{"type":"error","error":{"type":"invalid_request_error",'
+        '"message":"prompt is too long: 1000423 tokens > 1000000 maximum"}}'
+    )
+
+    with pytest.raises(litellm.ContextWindowExceededError) as excinfo:
+        exception_type(
+            model="claude-opus-5",
+            original_exception=Exception(error_message),
+            custom_llm_provider="vertex_ai",
+        )
+
+    assert excinfo.value.status_code == 400
+    assert excinfo.value.llm_provider == "vertex_ai"
+    assert excinfo.value.model == "claude-opus-5"
+
+
 # Test cases for Vertex AI RateLimitError mapping
 # As per https://github.com/BerriAI/litellm/issues/16189
 vertex_rate_limit_test_cases = [