diff --git a/litellm/llms/oci/chat/transformation.py b/litellm/llms/oci/chat/transformation.py
index b1af7ed2ec3..aaeb553c176 100644
--- a/litellm/llms/oci/chat/transformation.py
+++ b/litellm/llms/oci/chat/transformation.py
@@ -60,10 +60,12 @@ from litellm.types.utils import (
     ModelResponseStream,
     StreamingChoices,
 )
+from litellm.constants import DEFAULT_MAX_TOKENS
 from litellm.utils import (
     ChatCompletionMessageToolCall,
     CustomStreamWrapper,
     Usage,
+    get_max_tokens,
 )
 
 if TYPE_CHECKING:
@@ -661,7 +663,28 @@ class OCIChatConfig(BaseConfig):
         oci_region = optional_params.get("oci_region", "us-ashburn-1")
         return f"https://inference.generativeai.{oci_region}.oci.oraclecloud.com/20231130/actions/chat"
 
-    def _get_optional_params(self, vendor: OCIVendors, optional_params: dict) -> Dict:
+    @staticmethod
+    def _get_max_tokens_for_model(model: Optional[str] = None) -> int:
+        """
+        Get the max output tokens for a given OCI model.
+
+        Uses litellm's model cost map for a dynamic lookup, falling back to
+        DEFAULT_MAX_TOKENS (configurable via the DEFAULT_MAX_TOKENS env var)
+        when the model is not found.
+        """
+        if model is None:
+            return DEFAULT_MAX_TOKENS
+        try:
+            max_tokens = get_max_tokens(model)
+            if max_tokens is not None:
+                return max_tokens
+        except Exception:
+            pass
+        return DEFAULT_MAX_TOKENS
+
+    def _get_optional_params(
+        self, vendor: OCIVendors, optional_params: dict, model: Optional[str] = None
+    ) -> Dict:
         selected_params = {}
         if vendor == OCIVendors.COHERE:
             open_ai_to_oci_param_map = self.openai_to_oci_cohere_param_map
@@ -669,7 +692,7 @@ class OCIChatConfig(BaseConfig):
             open_ai_to_oci_param_map.pop("tool_choice")
             # Add default values for Cohere API
             selected_params = {
-                "maxTokens": 600,
+                "maxTokens": self._get_max_tokens_for_model(model),
                 "temperature": 1,
                 "topK": 0,
                 "topP": 0.75,
@@ -781,6 +804,13 @@ class OCIChatConfig(BaseConfig):
                         )
                     )
 
+            # Cohere requires all chat history elements to have a non-empty
+            # message.  Upstream callers (e.g. Open WebUI) may include
+            # assistant placeholders or empty system messages.  Skip them
+            # to avoid a 400 "all elements in history must have a message".
+            if not content and not tool_calls:
+                continue
+
             if role == "user":
                 chat_history.append(CohereMessage(role="USER", message=content))
             elif role == "assistant":
@@ -895,7 +925,7 @@ class OCIChatConfig(BaseConfig):
 
             # Create Cohere-specific chat request
             optional_cohere_params = self._get_optional_params(
-                OCIVendors.COHERE, optional_params
+                OCIVendors.COHERE, optional_params, model=model
             )
             chat_request = CohereChatRequest(
                 apiFormat="COHERE",
@@ -918,7 +948,7 @@ class OCIChatConfig(BaseConfig):
                 chatRequest=OCIChatRequestPayload(
                     apiFormat=vendor.value,
                     messages=adapt_messages_to_generic_oci_standard(messages),
-                    **self._get_optional_params(vendor, optional_params),
+                    **self._get_optional_params(vendor, optional_params, model=model),
                 ),
             )