fix: treat gpt-6 names as the gpt-5 request family in OpenAI and Azure configs (#39631)

Adapted for stable/1.98.x: requires_max_completion_tokens and its test are not on this line (added upstream by #36857), so that hunk is dropped. The Responses parametrize cases target a test class this line does not have, so the two gpt-6-astra cases are kept as a standalone test in the same file.

(cherry picked from commit 025a3ca42f)

litellm/llms/azure/chat/gpt_5_transformation.py

@@ -7,6 +7,7 @@ from litellm.exceptions import UnsupportedParamsError
 from litellm.llms.openai.chat.gpt_5_transformation import (
     OpenAIGPT5Config,
     _get_effort_level,
+    is_gpt_reasoning_series_name,
 )
 from litellm.types.llms.openai import AllMessageValues
 
@@ -35,26 +36,7 @@ class AzureOpenAIGPT5Config(AzureOpenAIConfig, OpenAIGPT5Config):
 
     @classmethod
     def is_model_gpt_5_model(cls, model: str) -> bool:
-        """Check if the Azure model string refers to a gpt-5 variant.
-
-        Accepts both explicit gpt-5 model names and the ``gpt5_series/`` prefix
-        used for manual routing.
-        """
-        # The gpt-5-chat* family (gpt-5-chat, gpt-5-chat-latest, gpt-5-chat-2025-08-07,
-        # …) are regular chat models: they support temperature and tool_choice but NOT
-        # reasoning_effort.  They must NOT be routed through the GPT-5 reasoning path.
-        #
-        # Versioned chat models such as gpt-5.3-chat and gpt-5.1-chat ARE reasoning
-        # models and must stay on the GPT-5 path.  The distinguishing feature is that
-        # the gpt-5-chat family has a literal "-chat" immediately after "gpt-5"
-        # (i.e. "gpt-5-chat…"), while versioned chat models interpose a minor version
-        # number (i.e. "gpt-5.<digit>-chat").
-        #
-        # Using a startswith("gpt-5-chat") prefix check on the normalized name (rather
-        # than a substring check) makes this boundary explicit and avoids any ambiguity
-        # if future model names coincidentally contain "gpt-5-chat" as an interior run.
-        _normalized: Final = model.split("/")[-1]  # strip provider prefix, e.g. "azure/"
-        return ("gpt-5" in model and not _normalized.startswith("gpt-5-chat")) or "gpt5_series" in model
+        return is_gpt_reasoning_series_name(model) or "gpt5_series" in model
 
     def get_supported_openai_params(self, model: str) -> list[str]:
         """Get supported parameters for Azure OpenAI GPT-5 models.

litellm/llms/openai/chat/gpt_5_transformation.py

@@ -44,6 +44,14 @@ def _get_effort_level(value: str | dict | None) -> str | None:
     return None
 
 
+GPT_REASONING_SERIES_MARKERS: Final = ("gpt-5", "gpt-6")
+
+
+def is_gpt_reasoning_series_name(model: str) -> bool:
+    normalized: Final = model.split("/")[-1]
+    return any(marker in model for marker in GPT_REASONING_SERIES_MARKERS) and not normalized.startswith("gpt-5-chat")
+
+
 class OpenAIGPT5Config(OpenAIGPTConfig):
     """Configuration for gpt-5 models including GPT-5-Codex variants.
 
@@ -56,21 +64,7 @@ class OpenAIGPT5Config(OpenAIGPTConfig):
 
     @classmethod
     def is_model_gpt_5_model(cls, model: str) -> bool:
-        # The gpt-5-chat* family (gpt-5-chat, gpt-5-chat-latest, gpt-5-chat-2025-08-07,
-        # …) are regular chat models: they support temperature and tool_choice but NOT
-        # reasoning_effort.  They must NOT be routed through the GPT-5 reasoning path.
-        #
-        # Versioned chat models such as gpt-5.3-chat and gpt-5.1-chat ARE reasoning
-        # models and must stay on the GPT-5 path.  The distinguishing feature is that
-        # the gpt-5-chat family has a literal "-chat" immediately after "gpt-5"
-        # (i.e. "gpt-5-chat…"), while versioned chat models interpose a minor version
-        # number (i.e. "gpt-5.<digit>-chat").
-        #
-        # Using a startswith("gpt-5-chat") prefix check on the normalized name (rather
-        # than a substring check) makes this boundary explicit and avoids any ambiguity
-        # if future model names coincidentally contain "gpt-5-chat" as an interior run.
-        _normalized: Final = model.split("/")[-1]  # strip provider prefix, e.g. "openai/"
-        return "gpt-5" in model and not _normalized.startswith("gpt-5-chat")
+        return is_gpt_reasoning_series_name(model)
 
     @classmethod
     def is_model_gpt_5_search_model(cls, model: str) -> bool:
@@ -105,6 +99,8 @@ class OpenAIGPT5Config(OpenAIGPTConfig):
     def is_model_gpt_5_4_plus_model(cls, model: str) -> bool:
         """Check if the model is gpt-5.4 or newer (5.4, 5.5, 5.6, etc., including pro)."""
         model_name: Final = model.split("/")[-1]
+        if model_name.startswith("gpt-6"):
+            return True
         if not model_name.startswith("gpt-5."):
             return False
         try:

litellm/llms/openai/responses/transformation.py

@@ -12,6 +12,7 @@ from litellm.litellm_core_utils.llm_response_utils.convert_dict_to_response impo
 )
 from litellm.litellm_core_utils.url_utils import encode_url_path_segment
 from litellm.llms.base_llm.responses.transformation import BaseResponsesAPIConfig
+from litellm.llms.openai.chat.gpt_5_transformation import is_gpt_reasoning_series_name
 from litellm.secret_managers.main import get_secret_str
 from litellm.types.llms.openai import *
 from litellm.types.responses.main import *
@@ -48,7 +49,7 @@ class OpenAIResponsesAPIConfig(BaseResponsesAPIConfig):
         parts: Final = model.split("/")
         if len(parts) > 1 and parts[0] not in ("openai",):
             return False
-        return "gpt-5" in model and "gpt-5-chat" not in model
+        return is_gpt_reasoning_series_name(model)
 
     @staticmethod
     def _supports_reasoning_effort_none(model: str) -> bool:

tests/test_litellm/llms/azure/chat/test_azure_gpt5_transformation.py

@@ -299,3 +299,15 @@ def test_azure_gpt5_1_does_not_support_logprobs(config: AzureOpenAIGPT5Config):
     supported_params = config.get_supported_openai_params(model="gpt-5.1")
     assert "logprobs" not in supported_params
     assert "top_logprobs" not in supported_params
+
+
+def test_azure_gpt_6_astra_takes_the_reasoning_series_request_shape():
+    params = litellm.get_optional_params(
+        model="gpt-6-astra",
+        custom_llm_provider="azure",
+        max_tokens=100,
+        reasoning_effort="max",
+    )
+    assert params["max_completion_tokens"] == 100
+    assert "max_tokens" not in params
+    assert params["reasoning_effort"] == "max"

tests/test_litellm/llms/openai/responses/test_openai_responses_transformation.py

@@ -1540,3 +1540,13 @@ class TestPhaseParameter:
         assert validated[0]["phase"] == "commentary"
         assert validated[1]["phase"] == "final_answer"
         assert "phase" not in validated[2]
+
+
+@pytest.mark.parametrize("effort", [None, "low"])
+def test_gpt_6_astra_drops_temperature_on_the_responses_path(effort):
+    mapped = OpenAIResponsesAPIConfig().map_openai_params(
+        response_api_optional_params={"temperature": 0, **({"reasoning": {"effort": effort}} if effort else {})},
+        model="gpt-6-astra",
+        drop_params=True,
+    )
+    assert "temperature" not in mapped

tests/test_litellm/llms/openai/test_gpt5_transformation.py

@@ -1309,3 +1309,17 @@ def test_responses_gpt54_allow_temperature_effort_none(
         drop_params=False,
     )
     assert params["temperature"] == 0.7
+
+
+def test_gpt_6_astra_takes_the_reasoning_series_request_shape():
+    params = litellm.get_optional_params(
+        model="gpt-6-astra",
+        custom_llm_provider="openai",
+        max_tokens=100,
+        reasoning_effort="max",
+        verbosity="low",
+    )
+    assert params["max_completion_tokens"] == 100
+    assert "max_tokens" not in params
+    assert params["reasoning_effort"] == "max"
+    assert params["verbosity"] == "low"

tests/test_litellm/llms/openai/test_is_model_gpt_5_model.py

@@ -41,6 +41,8 @@ from litellm.llms.azure.chat.gpt_5_transformation import AzureOpenAIGPT5Config
 
 # Models that MUST be classified as GPT-5 (routed through GPT-5 reasoning path)
 GPT5_MODELS = [
+    "gpt-6-astra",
+    "openai/gpt-6-astra",
     "gpt-5",
     "gpt-5.1",
     "gpt-5.2",
@@ -120,6 +122,8 @@ class TestOpenAIGPT5ConfigIsModelGpt5Model:
 # /v1/responses bridge (when reasoning_effort is set and tools are passed) on
 # is_model_gpt_5_4_plus_model, so the gpt-5.6 family must land on the True side.
 GPT5_4_PLUS_MODELS = [
+    "gpt-6-astra",
+    "openai/gpt-6-astra",
     "gpt-5.4",
     "gpt-5.5",
     "gpt-5.5-pro",

tests/test_litellm/test_main.py

@@ -778,6 +778,19 @@ def test_responses_api_bridge_check_gpt_5_4_tools_plus_reasoning_routes_to_respo
     assert model_info.get("mode") == "responses"
 
 
+def test_responses_api_bridge_check_gpt_6_astra_tools_with_default_reasoning_routes_to_responses():
+    from litellm.main import responses_api_bridge_check
+
+    model_info, model = responses_api_bridge_check(
+        model="gpt-6-astra",
+        custom_llm_provider="openai",
+        tools=[{"type": "function", "function": {"name": "get_capital"}}],
+    )
+
+    assert model == "gpt-6-astra"
+    assert model_info.get("mode") == "responses"
+
+
 def test_responses_api_bridge_check_gpt_5_5_tools_plus_reasoning_routes_to_responses():
     """gpt-5.5+ with both tools and reasoning_effort should route to Responses API."""
     from litellm.main import responses_api_bridge_check