From f35382de562e1041cc418ff10b31cc4ce2b6aa8a Mon Sep 17 00:00:00 2001
From: ryder777777 <sahilridder@gmail.com>
Date: Thu, 22 Oct 2026 15:33:20 +0000
Subject: [PATCH 1/2] fix(router): fallback for ModelNotMappedError in
 get_router_model_info (#47922)

Complexity-router compaction calls get_router_model_info for every
candidate deployment. On 1.106.0 with LITELLM_ENABLE_MCP_STDIO=true,
deployed MCP stdio models are not in model_cost, so
litellm.get_model_info raises ModelNotMappedError and crashes
/chat/completions via context_compaction._budget.

Wrap get_model_info in try/except: on ModelNotMappedError return a
minimal fallback ModelMapInfo with null windows and zero costs so
compaction treats the model as uncompactable instead of crashing
the request.
---
 litellm/router.py | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/litellm/router.py b/litellm/router.py
index da04e59f18a..052498f43d6 100644
--- a/litellm/router.py
+++ b/litellm/router.py
@@ -12198,7 +12198,27 @@ class Router:
         else:
             model_info_name = model
 
-        model_info: Final = litellm.get_model_info(model=model_info_name)
+        try:
+            model_info: Final = litellm.get_model_info(model=model_info_name)
+        except Exception as e:
+            if e.__class__.__name__ == "ModelNotMappedError" or "not mapped" in str(e).lower():
+                verbose_router_logger.warning(
+                    "Model '%s' not mapped in model_cost; returning fallback info for compaction/budget checks: %s",
+                    model_info_name,
+                    e,
+                )
+                fallback: ModelMapInfo = {
+                    "key": model_info_name,
+                    "max_tokens": None,
+                    "max_input_tokens": None,
+                    "max_output_tokens": None,
+                    "input_cost_per_token": 0,
+                    "output_cost_per_token": 0,
+                    "litellm_provider": custom_llm_provider or "",
+                    "mode": "chat",
+                }
+                return fallback
+            raise
         if model_info is None:
             return model_info
 

From d5951c174df762df0e8b669dd724af6c15e35c9d Mon Sep 17 00:00:00 2001
From: ryder777777 <sahilridder@gmail.com>
Date: Fri, 23 Oct 2026 21:08:33 +0000
Subject: [PATCH 2/2] fix(router): annotate fallback as Final[ModelMapInfo] and
 add unit coverage (#47922)

---
 litellm/router.py                             |  2 +-
 .../test_router_model_not_mapped_fallback.py  | 48 +++++++++++++++++++
 2 files changed, 49 insertions(+), 1 deletion(-)
 create mode 100644 tests/unit/test_router_model_not_mapped_fallback.py

diff --git a/litellm/router.py b/litellm/router.py
index 052498f43d6..3795c426582 100644
--- a/litellm/router.py
+++ b/litellm/router.py
@@ -12207,7 +12207,7 @@ class Router:
                     model_info_name,
                     e,
                 )
-                fallback: ModelMapInfo = {
+                fallback: Final[ModelMapInfo] = {
                     "key": model_info_name,
                     "max_tokens": None,
                     "max_input_tokens": None,
diff --git a/tests/unit/test_router_model_not_mapped_fallback.py b/tests/unit/test_router_model_not_mapped_fallback.py
new file mode 100644
index 00000000000..95161dc879c
--- /dev/null
+++ b/tests/unit/test_router_model_not_mapped_fallback.py
@@ -0,0 +1,48 @@
+from typing import Final
+from unittest.mock import patch
+
+import pytest
+
+import litellm
+from litellm.exceptions import ModelNotMappedError
+from litellm.router import Router
+
+
+def test_get_router_model_info_returns_fallback_on_model_not_mapped_error() -> None:
+    router: Final = Router(
+        model_list=[
+            {
+                "model_name": "mcp-stdio-group",
+                "litellm_params": {
+                    "model": "openai/unmapped-mcp-stdio-model",
+                    "api_key": "test-key",
+                },
+            }
+        ]
+    )
+
+    with patch.object(
+        litellm,
+        "get_model_info",
+        side_effect=ModelNotMappedError(message="Model 'unmapped-mcp-stdio-model' is not mapped", model="unmapped-mcp-stdio-model"),
+    ):
+        info: Final = router.get_router_model_info(model="mcp-stdio-group")
+
+    assert info is not None
+    assert info["max_tokens"] is None
+    assert info["max_input_tokens"] is None
+    assert info["max_output_tokens"] is None
+    assert info["input_cost_per_token"] == 0
+    assert info["output_cost_per_token"] == 0
+    assert info["litellm_provider"] == "openai"
+    assert info["mode"] == "chat"
+
+
+def test_get_router_model_info_reraises_unrelated_exceptions() -> None:
+    router: Final = Router(model_list=[])
+
+    with (
+        patch.object(litellm, "get_model_info", side_effect=RuntimeError("unexpected failure")),
+        pytest.raises(RuntimeError, match="unexpected failure"),
+    ):
+        router.get_router_model_info(model="any-model")