diff --git a/litellm/llms/anthropic.py b/litellm/llms/anthropic.py
index d061d63062..5c8c859977 100644
--- a/litellm/llms/anthropic.py
+++ b/litellm/llms/anthropic.py
@@ -131,18 +131,24 @@ def completion(
         )
     else:
         # Separate system prompt from rest of message
-        system_prompt_idx: Optional[int] = None
+        system_prompt_indices = []
+        system_prompt = ""
         for idx, message in enumerate(messages):
             if message["role"] == "system":
-                optional_params["system"] = message["content"]
-                system_prompt_idx = idx
-                break
-        if system_prompt_idx is not None:
-            messages.pop(system_prompt_idx)
+                system_prompt += message["content"]
+                system_prompt_indices.append(idx)
+        if len(system_prompt_indices) > 0:
+            for idx in reversed(system_prompt_indices):
+                messages.pop(idx)
+        if len(system_prompt) > 0:
+            optional_params["system"] = system_prompt
         # Format rest of message according to anthropic guidelines
-        messages = prompt_factory(
-            model=model, messages=messages, custom_llm_provider="anthropic"
-        )
+        try:
+            messages = prompt_factory(
+                model=model, messages=messages, custom_llm_provider="anthropic"
+            )
+        except Exception as e:
+            raise AnthropicError(status_code=400, message=str(e))
 
     ## Load Config
     config = litellm.AnthropicConfig.get_config()
diff --git a/litellm/llms/prompt_templates/factory.py b/litellm/llms/prompt_templates/factory.py
index 62a387e0b3..5e918eb7fd 100644
--- a/litellm/llms/prompt_templates/factory.py
+++ b/litellm/llms/prompt_templates/factory.py
@@ -5,6 +5,7 @@ from jinja2 import Template, exceptions, Environment, meta
 from typing import Optional, Any
 import imghdr, base64
 from typing import List
+import litellm
 
 
 def default_pt(messages):
@@ -642,11 +643,12 @@ def anthropic_messages_pt(messages: list):
     """
     # add role=tool support to allow function call result/error submission
     user_message_types = {"user", "tool"}
-    # reformat messages to ensure user/assistant are alternating, if there's either 2 consecutive 'user' messages or 2 consecutive 'assistant' message, add a blank 'user' or 'assistant' message to ensure compatibility
+    # reformat messages to ensure user/assistant are alternating, if there's either 2 consecutive 'user' messages or 2 consecutive 'assistant' message, merge them.
     new_messages = []
     msg_i = 0
     while msg_i < len(messages):
         user_content = []
+        ## MERGE CONSECUTIVE USER CONTENT ##
         while msg_i < len(messages) and messages[msg_i]["role"] in user_message_types:
             if isinstance(messages[msg_i]["content"], list):
                 for m in messages[msg_i]["content"]:
@@ -680,6 +682,7 @@ def anthropic_messages_pt(messages: list):
             new_messages.append({"role": "user", "content": user_content})
 
         assistant_content = []
+        ## MERGE CONSECUTIVE ASSISTANT CONTENT ##
         while msg_i < len(messages) and messages[msg_i]["role"] == "assistant":
             assistant_text = (
                 messages[msg_i].get("content") or ""
@@ -697,10 +700,22 @@ def anthropic_messages_pt(messages: list):
         if assistant_content:
             new_messages.append({"role": "assistant", "content": assistant_content})
 
+        if (
+            msg_i < len(messages)
+            and messages[msg_i]["role"] != user_message_types
+            and messages[msg_i]["role"] != "assistant"
+        ):
+            raise Exception(f"Invalid role passed in - {messages[msg_i]}")
+
     if new_messages[0]["role"] != "user":
-        new_messages.insert(
-            0, {"role": "user", "content": [{"type": "text", "text": "."}]}
-        )
+        if litellm.modify_params:
+            new_messages.insert(
+                0, {"role": "user", "content": [{"type": "text", "text": "."}]}
+            )
+        else:
+            raise Exception(
+                "Invalid first message. Should always start with 'role'='user' for Anthropic. System prompt is sent separately for Anthropic. set 'litellm.modify_params = True' or 'litellm_settings:modify_params = True' on proxy, to insert a placeholder user message - '.' as the first message, "
+            )
 
     if new_messages[-1]["role"] == "assistant":
         for content in new_messages[-1]["content"]:
diff --git a/litellm/utils.py b/litellm/utils.py
index 1b72ee42ea..8e9b676942 100644
--- a/litellm/utils.py
+++ b/litellm/utils.py
@@ -7223,7 +7223,17 @@ def exception_type(
                             message=f"AnthropicException - {original_exception.message}",
                             llm_provider="anthropic",
                             model=model,
-                            response=original_exception.response,
+                            response=(
+                                original_exception.response
+                                if hasattr(original_exception, "response")
+                                else httpx.Response(
+                                    status_code=500,
+                                    request=httpx.Request(
+                                        method="POST",
+                                        url="https://docs.anthropic.com/claude/reference/messages_post",
+                                    ),
+                                )
+                            ),
                         )
                     else:
                         exception_mapping_worked = True