test(oci): add tests for dynamic max_tokens and empty message filtering

12 mocked tests covering:
- Dynamic maxTokens lookup from model cost map
- Fallback to DEFAULT_MAX_TOKENS for unknown models
- User-provided max_tokens override
- Filtering of empty/None assistant, system messages from Cohere chat history
- Preservation of non-empty messages

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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

@@ -0,0 +1,194 @@
+"""
+Tests for OCI Cohere chat fixes:
+1. Dynamic maxTokens default via model cost map lookup
+2. Filtering empty messages from Cohere chat history
+"""
+
+import os
+import sys
+
+import pytest
+
+# Adds the parent directory to the system path
+sys.path.insert(0, os.path.abspath("../../../../.."))
+
+import litellm
+from litellm.llms.oci.chat.transformation import OCIChatConfig
+from litellm.types.llms.oci import OCIVendors
+from litellm.constants import DEFAULT_MAX_TOKENS
+
+
+TEST_COMPARTMENT_ID = "ocid1.compartment.oc1..xxxxxx"
+BASE_OCI_PARAMS = {
+    "oci_region": "us-ashburn-1",
+    "oci_user": "ocid1.user.oc1..xxxxxxEXAMPLExxxxxx",
+    "oci_fingerprint": "4f:29:77:cc:b1:3e:55:ab:61:2a:de:47:f1:38:4c:90",
+    "oci_tenancy": "ocid1.tenancy.oc1..xxxxxxEXAMPLExxxxxx",
+    "oci_compartment_id": TEST_COMPARTMENT_ID,
+    "oci_key": "<private_key.pem as string>",
+}
+
+
+class TestOCICohereMaxTokens:
+    """Tests for dynamic maxTokens default lookup."""
+
+    def test_max_tokens_uses_model_cost_map(self):
+        """When a model is in the cost map, maxTokens should use its max_output_tokens."""
+        config = OCIChatConfig()
+
+        # oci/cohere.command-a-03-2025 has max_output_tokens=4000 in the cost map
+        params = config._get_optional_params(
+            OCIVendors.COHERE, BASE_OCI_PARAMS, model="oci/cohere.command-a-03-2025"
+        )
+
+        assert params["maxTokens"] == 4000
+
+    def test_max_tokens_falls_back_to_default(self):
+        """When a model is NOT in the cost map, maxTokens should fall back to DEFAULT_MAX_TOKENS."""
+        config = OCIChatConfig()
+
+        params = config._get_optional_params(
+            OCIVendors.COHERE, BASE_OCI_PARAMS, model="oci/cohere.nonexistent-model"
+        )
+
+        assert params["maxTokens"] == DEFAULT_MAX_TOKENS
+
+    def test_max_tokens_falls_back_when_model_is_none(self):
+        """When model is None, maxTokens should fall back to DEFAULT_MAX_TOKENS."""
+        config = OCIChatConfig()
+
+        params = config._get_optional_params(
+            OCIVendors.COHERE, BASE_OCI_PARAMS, model=None
+        )
+
+        assert params["maxTokens"] == DEFAULT_MAX_TOKENS
+
+    def test_user_provided_max_tokens_overrides_default(self):
+        """User-provided max_tokens should override the dynamic default."""
+        config = OCIChatConfig()
+
+        params_with_override = {**BASE_OCI_PARAMS, "max_tokens": 1024}
+        params = config._get_optional_params(
+            OCIVendors.COHERE, params_with_override, model="oci/cohere.command-a-03-2025"
+        )
+
+        assert params["maxTokens"] == 1024
+
+    def test_get_max_tokens_for_model_known_model(self):
+        """_get_max_tokens_for_model should return the correct value for a known model."""
+        result = OCIChatConfig._get_max_tokens_for_model("oci/cohere.command-a-03-2025")
+        assert result == 4000
+
+    def test_get_max_tokens_for_model_unknown_model(self):
+        """_get_max_tokens_for_model should return DEFAULT_MAX_TOKENS for an unknown model."""
+        result = OCIChatConfig._get_max_tokens_for_model("oci/unknown-model-xyz")
+        assert result == DEFAULT_MAX_TOKENS
+
+    def test_get_max_tokens_for_model_none(self):
+        """_get_max_tokens_for_model should return DEFAULT_MAX_TOKENS when model is None."""
+        result = OCIChatConfig._get_max_tokens_for_model(None)
+        assert result == DEFAULT_MAX_TOKENS
+
+
+class TestOCICohereEmptyMessages:
+    """Tests for filtering empty messages from Cohere chat history.
+
+    Note: adapt_messages_to_cohere_standard() processes messages[:-1]
+    (all messages except the last one, which is the current user message).
+    The returned CohereMessage objects are Pydantic models with .role and
+    .message attributes.
+    """
+
+    def test_empty_assistant_message_is_filtered(self):
+        """An assistant message with empty content should be excluded from chat history."""
+        config = OCIChatConfig()
+        messages = [
+            {"role": "user", "content": "Hello"},
+            {"role": "assistant", "content": ""},
+            {"role": "user", "content": "How are you?"},
+        ]
+
+        # messages[:-1] = ["Hello" (user), "" (assistant)]
+        # Empty assistant is filtered, so only "Hello" remains
+        history = config.adapt_messages_to_cohere_standard(messages)
+
+        assert len(history) == 1
+        assert history[0].role == "USER"
+        assert history[0].message == "Hello"
+
+    def test_empty_system_message_is_filtered(self):
+        """A system message with empty content should be excluded from chat history."""
+        config = OCIChatConfig()
+        messages = [
+            {"role": "system", "content": ""},
+            {"role": "user", "content": "Hello"},
+            {"role": "user", "content": "Last message"},
+        ]
+
+        # messages[:-1] = ["" (system), "Hello" (user)]
+        # Empty system is filtered, so only "Hello" remains
+        history = config.adapt_messages_to_cohere_standard(messages)
+
+        assert len(history) == 1
+        assert history[0].role == "USER"
+        assert history[0].message == "Hello"
+
+    def test_none_content_message_is_filtered(self):
+        """A message with None content should be excluded from chat history."""
+        config = OCIChatConfig()
+        messages = [
+            {"role": "user", "content": "Hello"},
+            {"role": "assistant", "content": None},
+            {"role": "user", "content": "Last message"},
+        ]
+
+        # messages[:-1] = ["Hello" (user), None (assistant)]
+        # None assistant is filtered, so only "Hello" remains
+        history = config.adapt_messages_to_cohere_standard(messages)
+
+        assert len(history) == 1
+        assert history[0].role == "USER"
+        assert history[0].message == "Hello"
+
+    def test_non_empty_messages_are_preserved(self):
+        """Non-empty messages should be included in chat history normally."""
+        config = OCIChatConfig()
+        messages = [
+            {"role": "user", "content": "Hello"},
+            {"role": "assistant", "content": "Hi there!"},
+            {"role": "user", "content": "Last message"},
+        ]
+
+        # messages[:-1] = ["Hello" (user), "Hi there!" (assistant)]
+        history = config.adapt_messages_to_cohere_standard(messages)
+
+        assert len(history) == 2
+        assert history[0].role == "USER"
+        assert history[0].message == "Hello"
+        assert history[1].role == "CHATBOT"
+        assert history[1].message == "Hi there!"
+
+    def test_mixed_empty_and_nonempty_messages(self):
+        """Only empty messages should be filtered; non-empty ones kept."""
+        config = OCIChatConfig()
+        messages = [
+            {"role": "system", "content": ""},
+            {"role": "user", "content": "First question"},
+            {"role": "assistant", "content": ""},
+            {"role": "user", "content": "Second question"},
+            {"role": "assistant", "content": "A real answer"},
+            {"role": "user", "content": "Last message"},
+        ]
+
+        # messages[:-1] excludes "Last message"
+        # Empty system and empty assistant are filtered
+        # Remaining: "First question" (user), "Second question" (user), "A real answer" (chatbot)
+        history = config.adapt_messages_to_cohere_standard(messages)
+
+        assert len(history) == 3
+        assert history[0].role == "USER"
+        assert history[0].message == "First question"
+        assert history[1].role == "USER"
+        assert history[1].message == "Second question"
+        assert history[2].role == "CHATBOT"
+        assert history[2].message == "A real answer"