fix(oci): accept default n=1 on Cohere instead of hard-failing (#29705)

* fix(oci): accept default n=1 on Cohere instead of hard-failing

Cohere on OCI has no numGenerations field, so n was mapped to False and
map_openai_params raised "param `n` is not supported on OCI" whenever a client
sent n. But n=1 (and None) is the OpenAI default single-generation request,
which every OCI model produces anyway, so standard clients that always send
n=1 (such as the MLflow gateway) were rejected with a 500.

Drop n=1/None silently for Cohere; only n>1 is genuinely unsupported and still
raises (or drops under drop_params). Generic models are unaffected and keep
numGenerations, including n>1.

* docs(oci): explain why n is not advertised for Cohere despite tolerating n=1

* test(oci): gateway integration test for Cohere default n=1

Added to tests/integration/ (the real-network integration suite) reusing the
existing OCI proxy harness, not tests/llm_translation/ which is mock-only.

---------

Co-authored-by: Sameer Kankute <sameer@berri.ai>

litellm/llms/oci/chat/transformation.py

@@ -333,6 +333,11 @@ class OCIChatConfig(BaseConfig):
             if get_vendor_from_model(model) == OCIVendors.COHERE
             else self.openai_to_oci_generic_param_map
         )
+        # `n` is intentionally not advertised for Cohere even though n=1 is
+        # tolerated: Cohere has no numGenerations field, so n>1 cannot be
+        # honoured and advertising it would be misleading. Callers that gate on
+        # this list strip n=1 (a no-op, matching what map_openai_params does);
+        # callers that bypass it have n=1 dropped there. Both paths converge.
         return [key for key, value in param_map.items() if value]
 
     def map_openai_params(
@@ -353,6 +358,13 @@ class OCIChatConfig(BaseConfig):
         for key, value in {**non_default_params, **optional_params}.items():
             alias = param_map.get(key)
             if alias is False:
+                # n=1 (or None) is the OpenAI default: a single generation, which
+                # every OCI model produces anyway. Drop it silently so standard
+                # clients that always send n=1 (e.g. the MLflow gateway) are not
+                # rejected; only n>1 is genuinely unsupported on Cohere, which
+                # has no numGenerations field.
+                if key == "n" and (value is None or value == 1):
+                    continue
                 if drop_params or litellm.drop_params:
                     continue
                 raise OCIError(

tests/integration/test_oci_proxy_integration.py

@@ -260,7 +260,6 @@ def test_embedding_via_proxy(proxy_url: str) -> None:
     assert len(embedding) >= 64
     assert all(isinstance(x, (int, float)) for x in embedding)
 
-
 def test_model_list_advertises_oci_models(proxy_url: str) -> None:
     """The /v1/models registry advertises every OCI alias from the config."""
     r = httpx.get(
@@ -274,6 +273,26 @@ def test_model_list_advertises_oci_models(proxy_url: str) -> None:
         assert expected in advertised, f"{expected} missing from /v1/models: {advertised}"
 
 
+def test_cohere_default_n_via_proxy(proxy_url: str) -> None:
+    """A Cohere request carrying the default n=1 succeeds through the gateway.
+
+    Regression for the HTTP 500 ``param `n` is not supported on OCI`` that
+    rejected every client which always sends n=1 (e.g. the MLflow gateway),
+    since OCI Cohere has no numGenerations field.
+    """
+    payload = {**_chat_payload("oci-cohere-command"), "n": 1}
+    r = httpx.post(
+        f"{proxy_url}/v1/chat/completions",
+        headers=_auth_headers(),
+        json=payload,
+        timeout=REQUEST_TIMEOUT_S,
+    )
+    assert r.status_code == 200, f"n=1 -> {r.status_code}: {r.text}"
+    body = r.json()
+    assert body["object"] == "chat.completion"
+    assert body["choices"][0]["message"].get("content") is not None
+
+
 @pytest.mark.parametrize("model", ["oci-cohere-command", "oci-llama"])
 def test_response_format_json_schema_via_proxy(proxy_url: str, model: str) -> None:
     """A response_format json_schema succeeds through the gateway for both a
@@ -353,4 +372,4 @@ def test_omitted_max_tokens_not_truncated(proxy_url: str) -> None:
     assert content.strip(), f"empty content: {choice}"
     # The ~20-token server default truncated well before this; a complete
     # four-to-five sentence answer comfortably exceeds it.
-    assert body["usage"]["completion_tokens"] > 50, body["usage"]
+    assert body["usage"]["completion_tokens"] > 50, body["usage"]

tests/test_litellm/llms/oci/chat/test_oci_chat_transformation.py

@@ -1464,6 +1464,53 @@ class TestOCIChatConfigErrorPaths:
         )
         assert "audio" not in result
 
+    def test_map_openai_params_cohere_n_default_dropped(self):
+        """Cohere has no numGenerations field, but n=1 (and None) is the OpenAI
+        default single-generation request. It must be dropped silently rather
+        than raising, so standard clients that always send n=1 (e.g. the MLflow
+        gateway) are not rejected."""
+        config = OCIChatConfig()
+        for n in (1, None):
+            result = config.map_openai_params(
+                non_default_params={"n": n},
+                optional_params={},
+                model="cohere.command-latest",
+                drop_params=False,
+            )
+            assert "n" not in result and "numGenerations" not in result
+
+    def test_map_openai_params_cohere_n_gt_1_raises_without_drop(self):
+        """n>1 is genuinely unsupported on Cohere and must raise without drop."""
+        config = OCIChatConfig()
+        with pytest.raises(Exception, match="not supported on OCI"):
+            config.map_openai_params(
+                non_default_params={"n": 3},
+                optional_params={},
+                model="cohere.command-latest",
+                drop_params=False,
+            )
+
+    def test_map_openai_params_cohere_n_gt_1_dropped_with_drop(self):
+        config = OCIChatConfig()
+        result = config.map_openai_params(
+            non_default_params={"n": 3},
+            optional_params={},
+            model="cohere.command-latest",
+            drop_params=True,
+        )
+        assert "n" not in result and "numGenerations" not in result
+
+    def test_map_openai_params_generic_n_maps_to_num_generations(self):
+        """Generic models keep numGenerations, including n>1."""
+        config = OCIChatConfig()
+        result = config.map_openai_params(
+            non_default_params={"n": 2},
+            optional_params={},
+            model=TEST_MODEL_NAME,
+            drop_params=False,
+        )
+        assert result["numGenerations"] == 2
+
     def test_transform_request_tool_choice_string_mapped(self):
         config = OCIChatConfig()
         result = config.transform_request(