fix(proxy): register transcribe as a known provider for model grants

#41515 added the cost map entry transcribe/StartTranscriptionJob under a
new litellm_provider value "transcribe" without registering that provider
anywhere else, so litellm.models_by_provider had no "transcribe" key.

test_models_by_provider derives its provider set from the cost map itself,
so it went red on main. The user-visible half is that get_provider_models
returned None for the provider, which get_known_models_from_wildcard turns
into an empty list, leaving a transcribe/* key or team grant resolving to
no models.

Mirror the aws_polly registration: an enum member, a model set, an
ingestion branch, and a models_by_provider entry. Amazon Transcribe is
reached through the pass-through route rather than the Add Model form, so
it joins the frozen unlisted set the Add Model drift test tracks.

litellm/__init__.py

@@ -701,6 +701,7 @@ github_copilot_models: Set = set()
 chatgpt_models: Set = set()
 minimax_models: Set = set()
 aws_polly_models: Set = set()
+transcribe_models: Set = set()
 gigachat_models: Set = set()
 llamagate_models: Set = set()
 reducto_models: Set = set()
@@ -980,6 +981,8 @@ def _populate_provider_model_sets(model_cost_map: Dict) -> None:
             minimax_models.add(key)
         elif value.get("litellm_provider") == "aws_polly":
             aws_polly_models.add(key)
+        elif value.get("litellm_provider") == "transcribe":
+            transcribe_models.add(key)
         elif value.get("litellm_provider") == "gigachat":
             gigachat_models.add(key)
         elif value.get("litellm_provider") == "llamagate":
@@ -1227,6 +1230,7 @@ def _build_models_by_provider() -> dict:
         "chatgpt": chatgpt_models,
         "minimax": minimax_models,
         "aws_polly": aws_polly_models,
+        "transcribe": transcribe_models,
         "gigachat": gigachat_models,
         "llamagate": llamagate_models,
         "reducto": reducto_models,

litellm/types/utils.py

@@ -3989,6 +3989,7 @@ class LlmProviders(str, Enum):
     REDUCTO = "reducto"
     RUNWAYML = "runwayml"
     AWS_POLLY = "aws_polly"
+    TRANSCRIBE = "transcribe"
     HUGGINGFACE = "huggingface"
     TOGETHER_AI = "together_ai"
     OPENROUTER = "openrouter"

tests/test_litellm/proxy/auth/test_model_checks.py

@@ -879,3 +879,18 @@ def test_get_complete_model_list_sentinel_only_grants_nothing():
         infer_model_from_keys=False,
     )
     assert result == []
+
+
+def test_transcribe_is_a_known_provider_for_wildcard_expansion():
+    import litellm
+    from litellm.proxy.auth.model_checks import (
+        get_known_models_from_wildcard,
+        get_provider_models,
+    )
+
+    assert "transcribe" in litellm.models_by_provider
+    assert "transcribe/StartTranscriptionJob" in litellm.models_by_provider["transcribe"]
+    assert get_provider_models("transcribe") == ["transcribe/StartTranscriptionJob"]
+    assert get_known_models_from_wildcard("transcribe/*") == [
+        "transcribe/StartTranscriptionJob"
+    ]

tests/test_litellm/proxy/public_endpoints/test_public_endpoints.py

@@ -384,6 +384,7 @@ ADD_MODEL_UNLISTED_PROVIDERS: Final = frozenset(
         "tencent",
         "tensormesh",
         "text-completion-inception",
+        "transcribe",
         "valkey",
         "xiaomi_mimo",
         "zai",