fix(bedrock): drop stop sequences for GPT 5.6 and newer instead of forwarding them to a 400 (#45664)

Co-authored-by: kerry <kerry@berri.ai>
Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

litellm/llms/bedrock/common_utils.py

@@ -896,11 +896,11 @@ def bedrock_runtime_chat_completions_is_default(model: str) -> bool:
 def bedrock_rejects_stop_sequences(model: str) -> bool:
     """Whether AWS refuses stop sequences for this model on every Bedrock route.
 
-    Grok answers ``stopSequences`` on Converse and ``stop`` on native Chat Completions alike with
-    ``This model doesn't support the stopSequences field`` (Grok 4.6 and 4.7 checked live on 2026-10-09),
-    so litellm drops ``stop`` for it instead of forwarding it to a 400.
+    Grok and GPT 5.6 and newer answer ``stopSequences`` on Converse and ``stop`` on native Chat Completions
+    alike with ``This model doesn't support the stopSequences field`` (Grok 4.6 and 4.7, GPT 5.6 and GPT 6.1
+    checked live on 2026-10-09), so litellm drops ``stop`` for them instead of forwarding it to a 400.
     """
-    return _XAI_GROK_MODEL_RE.search(model) is not None
+    return _bedrock_runtime_chat_completions_default_family(model)
 
 
 def bedrock_runtime_chat_completions_serves_tools_with_reasoning(model: str) -> bool:

tests/integration/providers/test_bedrock_runtime_chat_completions_wire.py

@@ -354,19 +354,14 @@ def test_model_id_application_inference_profile_keeps_converse_at_the_profile_ur
         )
 
 
-def test_stop_sequences_keep_converse(gateway: Gateway) -> None:
+def test_stop_sequences_are_dropped_and_the_request_stays_native(gateway: Gateway) -> None:
     marker: Final = uuid.uuid4().hex
     with wire_server(respond) as wire, gateway.scenario() as scenario:
         model: Final = _deployment(scenario, wire)
         response: Final = _chat(gateway, model, marker, stop=["END"])
-        payload: Final = _payload(response)
-        assert payload["choices"] == [
-            {"finish_reason": "stop", "index": 0, "message": {"content": answer(marker), "role": "assistant"}}
-        ], response.text
-        body: Final = _body(_converse_request(wire))
-        assert body["messages"] == _converse_messages(marker), body
-        assert body["inferenceConfig"] == {"stopSequences": ["END"]}, body
-        assert _spend_row(str(payload["id"])) == _success_row(model, f"{wire.url}{CONVERSE_TARGET}")
+        assert _payload(response)["id"] == f"chatcmpl-{marker}", response.text
+        assert _body(_native_request(wire)) == _native_body(GPT, marker)
+        assert _spend_row(f"chatcmpl-{marker}") == _success_row(model, f"{wire.url}{NATIVE_TARGET}")
 
 
 def test_json_object_response_format_keeps_converse(gateway: Gateway) -> None:

tests/unit/llms/bedrock/chat/chat_completions/test_bedrock_chat_completions_transformation.py

@@ -451,17 +451,24 @@ def test_converse_extension_params_fall_back_to_converse(local_cost_map, model,
     assert BedrockModelInfo.get_bedrock_route(model, {key: None for key in request_params}) == "chat_completions"
 
 
-@pytest.mark.parametrize(
-    "model",
-    ["chat_completions/openai.gpt-oss-20b-1:0", "bedrock/global.openai.gpt-5.6-sol", "bedrock/us.openai.gpt-6.1-sol"],
-)
-def test_stop_keeps_other_models_on_converse(local_cost_map, model):
+def test_stop_keeps_gpt_oss_on_converse(local_cost_map):
+    model = "chat_completions/openai.gpt-oss-20b-1:0"
     assert bedrock_request_needs_converse(model, {"stop": ["END"]}) is True
     assert BedrockModelInfo.get_bedrock_route(model, {"stop": ["END"]}) == "converse"
 
 
-@pytest.mark.parametrize("model", ["bedrock/global.xai.grok-4.7", "bedrock/us.xai.grok-4.6"])
-def test_stop_is_dropped_on_chat_completions_for_grok(local_cost_map, fake_aws_env, model):
+@pytest.mark.parametrize(
+    "model",
+    [
+        "bedrock/global.xai.grok-4.7",
+        "bedrock/us.xai.grok-4.6",
+        "bedrock/global.openai.gpt-5.6-sol",
+        "bedrock/us.openai.gpt-5.6-terra",
+        "bedrock/global.openai.gpt-6-sol",
+        "bedrock/us.openai.gpt-6.1-sol",
+    ],
+)
+def test_stop_is_dropped_on_chat_completions_for_models_rejecting_stop_sequences(local_cost_map, fake_aws_env, model):
     requests, client = _recording_client(json=_chat_completion_json("ok", model.removeprefix("bedrock/")))
     response = litellm.completion(
         model=model, messages=[{"role": "user", "content": "hello"}], stop=["</block>"], max_tokens=64, client=client
@@ -474,17 +481,18 @@ def test_stop_is_dropped_on_chat_completions_for_grok(local_cost_map, fake_aws_e
     assert response.choices[0].message.content == "ok"
 
 
-def test_stop_is_dropped_on_converse_for_grok(local_cost_map, fake_aws_env):
+@pytest.mark.parametrize("model_id", ["global.xai.grok-4.7", "global.openai.gpt-5.6-sol", "us.openai.gpt-6.1-sol"])
+def test_stop_is_dropped_on_converse_for_models_rejecting_stop_sequences(local_cost_map, fake_aws_env, model_id):
     requests, client = _recording_client(json=CONVERSE_JSON)
     litellm.completion(
-        model="bedrock/converse/global.xai.grok-4.7",
+        model=f"bedrock/converse/{model_id}",
         messages=[{"role": "user", "content": "hello"}],
         stop=["</block>"],
         max_tokens=64,
         client=client,
     )
 
-    assert requests[0].url.raw_path == b"/model/global.xai.grok-4.7/converse"
+    assert requests[0].url.raw_path == f"/model/{model_id}/converse".encode()
     assert json.loads(requests[0].content)["inferenceConfig"] == {"maxTokens": 64}