fix(fireworks_ai): return None for transcription in get_supported_openai_params

Fireworks AI deprecated audio inference on 2026-06-10; the endpoint is
decommissioned. Without an explicit transcription branch, requests with
request_type='transcription' fell through to the else and returned
FireworksAIConfig chat-completion params. Return None instead to signal
the provider does not support transcription.

litellm/litellm_core_utils/get_supported_openai_params.py

@@ -85,6 +85,8 @@ def get_supported_openai_params(
             return litellm.FireworksAIEmbeddingConfig().get_supported_openai_params(
                 model=model
             )
+        elif request_type == "transcription":
+            return None
         else:
             return litellm.FireworksAIConfig().get_supported_openai_params(model=model)
     elif custom_llm_provider == "nvidia_nim":

tests/llm_translation/test_fireworks_ai_translation.py

@@ -7,6 +7,9 @@ sys.path.insert(
     0, os.path.abspath("../..")
 )  # Adds the parent directory to the system path
 import litellm
+from litellm.litellm_core_utils.get_supported_openai_params import (
+    get_supported_openai_params,
+)
 from litellm.llms.fireworks_ai.chat.transformation import FireworksAIConfig
 
 fireworks = FireworksAIConfig()
@@ -67,6 +70,18 @@ def test_map_response_format():
     assert result == {"response_format": response_format}
 
 
+def test_get_supported_openai_params_transcription_returns_none():
+    # Fireworks AI deprecated audio transcription on 2026-06-10; the endpoint
+    # is decommissioned. Returning None (not chat-completion params) signals
+    # to callers that transcription is unsupported for this provider.
+    result = get_supported_openai_params(
+        model="fireworks_ai/accounts/fireworks/models/whisper-v3",
+        custom_llm_provider="fireworks_ai",
+        request_type="transcription",
+    )
+    assert result is None
+
+
 @pytest.mark.parametrize(
     "disable_add_transform_inline_image_block",
     [True, False],