diff --git a/llama-index-core/llama_index/core/agent/legacy/react/base.py b/llama-index-core/llama_index/core/agent/legacy/react/base.py
index 9d70172bcd2dd..04ef72d55e14c 100644
--- a/llama-index-core/llama_index/core/agent/legacy/react/base.py
+++ b/llama-index-core/llama_index/core/agent/legacy/react/base.py
@@ -151,6 +151,7 @@ def _extract_reasoning_step(
         if output.message.content is None:
             raise ValueError("Got empty message.")
         message_content = output.message.content
+
         current_reasoning = []
         try:
             reasoning_step = self._output_parser.parse(message_content, is_streaming)
@@ -268,6 +269,7 @@ def _infer_stream_chunk_is_final(self, chunk: ChatResponse) -> bool:
             bool: Boolean on whether the chunk is the start of the final response
         """
         latest_content = chunk.message.content
+
         if latest_content:
             if not latest_content.startswith(
                 "Thought"
diff --git a/llama-index-core/llama_index/core/agent/react/step.py b/llama-index-core/llama_index/core/agent/react/step.py
index bf4e6e1f0ff10..c43b729029d30 100644
--- a/llama-index-core/llama_index/core/agent/react/step.py
+++ b/llama-index-core/llama_index/core/agent/react/step.py
@@ -237,6 +237,7 @@ def _extract_reasoning_step(
         if output.message.content is None:
             raise ValueError("Got empty message.")
         message_content = output.message.content
+
         current_reasoning = []
         try:
             reasoning_step = self._output_parser.parse(message_content, is_streaming)
diff --git a/llama-index-core/llama_index/core/agent/react_multimodal/step.py b/llama-index-core/llama_index/core/agent/react_multimodal/step.py
index c42104cbfdf44..ff087a3ef0159 100644
--- a/llama-index-core/llama_index/core/agent/react_multimodal/step.py
+++ b/llama-index-core/llama_index/core/agent/react_multimodal/step.py
@@ -244,6 +244,7 @@ def _extract_reasoning_step(
         if output.message.content is None:
             raise ValueError("Got empty message.")
         message_content = output.message.content
+
         current_reasoning = []
         try:
             reasoning_step = self._output_parser.parse(message_content, is_streaming)
diff --git a/llama-index-core/llama_index/core/base/llms/base.py b/llama-index-core/llama_index/core/base/llms/base.py
index cca8a8d78065e..860b31586b461 100644
--- a/llama-index-core/llama_index/core/base/llms/base.py
+++ b/llama-index-core/llama_index/core/base/llms/base.py
@@ -1,6 +1,7 @@
 from abc import abstractmethod
 from typing import (
     Any,
+    List,
     Sequence,
 )
 
@@ -13,6 +14,7 @@
     CompletionResponseAsyncGen,
     CompletionResponseGen,
     LLMMetadata,
+    TextBlock,
 )
 from llama_index.core.base.query_pipeline.query import (
     ChainableMixin,
@@ -46,6 +48,26 @@ def metadata(self) -> LLMMetadata:
             LLMMetadata: LLM metadata containing various information about the LLM.
         """
 
+    def convert_chat_messages(self, messages: Sequence[ChatMessage]) -> List[Any]:
+        """Convert chat messages to an LLM specific message format."""
+        converted_messages = []
+        for message in messages:
+            if isinstance(message.content, str):
+                converted_messages.append(message)
+            elif isinstance(message.content, List):
+                content_string = ""
+                for block in message.content:
+                    if isinstance(block, TextBlock):
+                        content_string += block.text
+                    else:
+                        raise ValueError("LLM only supports text inputs")
+                message.content = content_string
+                converted_messages.append(message)
+            else:
+                raise ValueError(f"Invalid message content: {message.content!s}")
+
+        return converted_messages
+
     @abstractmethod
     def chat(self, messages: Sequence[ChatMessage], **kwargs: Any) -> ChatResponse:
         """Chat endpoint for LLM.
diff --git a/llama-index-core/llama_index/core/base/llms/types.py b/llama-index-core/llama_index/core/base/llms/types.py
index 8c3248e3769f3..971db8e743841 100644
--- a/llama-index-core/llama_index/core/base/llms/types.py
+++ b/llama-index-core/llama_index/core/base/llms/types.py
@@ -1,8 +1,22 @@
+import base64
+import requests
 from enum import Enum
-from typing import Any, AsyncGenerator, Dict, Generator, Optional, Union, List, Any
+from io import BytesIO
+from typing import (
+    Any,
+    AsyncGenerator,
+    Dict,
+    Generator,
+    Literal,
+    Optional,
+    Union,
+    List,
+    Any,
+)
 
 from llama_index.core.bridge.pydantic import BaseModel, Field, ConfigDict
 from llama_index.core.constants import DEFAULT_CONTEXT_WINDOW, DEFAULT_NUM_OUTPUTS
+from llama_index.core.schema import ImageType
 
 try:
     from pydantic import BaseModel as V2BaseModel
@@ -26,6 +40,39 @@ class MessageRole(str, Enum):
 
 
 # ===== Generic Model Input - Chat =====
+class ContentBlockTypes(str, Enum):
+    TEXT = "text"
+    IMAGE = "image"
+
+
+class TextBlock(BaseModel):
+    type: Literal[ContentBlockTypes.TEXT] = ContentBlockTypes.TEXT
+
+    text: str
+
+
+class ImageBlock(BaseModel):
+    type: Literal[ContentBlockTypes.IMAGE] = ContentBlockTypes.IMAGE
+
+    image: Optional[str] = None
+    image_path: Optional[str] = None
+    image_url: Optional[str] = None
+    image_mimetype: Optional[str] = None
+
+    def resolve_image(self) -> ImageType:
+        """Resolve an image such that PIL can read it."""
+        if self.image is not None:
+            return BytesIO(base64.b64decode(self.image))
+        elif self.image_path is not None:
+            return self.image_path
+        elif self.image_url is not None:
+            # load image from URL
+            response = requests.get(self.image_url)
+            return BytesIO(response.content)
+        else:
+            raise ValueError("No image found in the chat message!")
+
+
 class ChatMessage(BaseModel):
     """Chat message."""
 
diff --git a/llama-index-core/llama_index/core/chat_engine/simple.py b/llama-index-core/llama_index/core/chat_engine/simple.py
index 6a35de5570eca..c96b000b32888 100644
--- a/llama-index-core/llama_index/core/chat_engine/simple.py
+++ b/llama-index-core/llama_index/core/chat_engine/simple.py
@@ -80,7 +80,13 @@ def chat(
         if hasattr(self._memory, "tokenizer_fn"):
             initial_token_count = len(
                 self._memory.tokenizer_fn(
-                    " ".join([(m.content or "") for m in self._prefix_messages])
+                    " ".join(
+                        [
+                            (m.content or "")
+                            for m in self._prefix_messages
+                            if isinstance(m.content, str)
+                        ]
+                    )
                 )
             )
         else:
@@ -107,7 +113,13 @@ def stream_chat(
         if hasattr(self._memory, "tokenizer_fn"):
             initial_token_count = len(
                 self._memory.tokenizer_fn(
-                    " ".join([(m.content or "") for m in self._prefix_messages])
+                    " ".join(
+                        [
+                            (m.content or "")
+                            for m in self._prefix_messages
+                            if isinstance(m.content, str)
+                        ]
+                    )
                 )
             )
         else:
@@ -138,7 +150,13 @@ async def achat(
         if hasattr(self._memory, "tokenizer_fn"):
             initial_token_count = len(
                 self._memory.tokenizer_fn(
-                    " ".join([(m.content or "") for m in self._prefix_messages])
+                    " ".join(
+                        [
+                            (m.content or "")
+                            for m in self._prefix_messages
+                            if isinstance(m.content, str)
+                        ]
+                    )
                 )
             )
         else:
@@ -165,7 +183,13 @@ async def astream_chat(
         if hasattr(self._memory, "tokenizer_fn"):
             initial_token_count = len(
                 self._memory.tokenizer_fn(
-                    " ".join([(m.content or "") for m in self._prefix_messages])
+                    " ".join(
+                        [
+                            (m.content or "")
+                            for m in self._prefix_messages
+                            if isinstance(m.content, str)
+                        ]
+                    )
                 )
             )
         else:
diff --git a/llama-index-core/llama_index/core/llms/function_calling.py b/llama-index-core/llama_index/core/llms/function_calling.py
index c4809ef554877..005d676c891ca 100644
--- a/llama-index-core/llama_index/core/llms/function_calling.py
+++ b/llama-index-core/llama_index/core/llms/function_calling.py
@@ -244,6 +244,7 @@ async def apredict_and_call(
             allow_parallel_tool_calls=allow_parallel_tool_calls,
             **kwargs,
         )
+
         tool_calls = self.get_tool_calls_from_response(
             response, error_on_no_tool_call=error_on_no_tool_call
         )
diff --git a/llama-index-core/llama_index/core/llms/llm.py b/llama-index-core/llama_index/core/llms/llm.py
index 813c726e5a0fe..8978f6c162cef 100644
--- a/llama-index-core/llama_index/core/llms/llm.py
+++ b/llama-index-core/llama_index/core/llms/llm.py
@@ -755,11 +755,16 @@ def predict_and_call(
             handle_reasoning_failure_fn=kwargs.get("handle_reasoning_failure_fn", None),
         )
 
-        if isinstance(user_msg, ChatMessage):
+        if isinstance(user_msg, ChatMessage) and isinstance(user_msg.content, str):
             user_msg = user_msg.content
         elif isinstance(user_msg, str):
             pass
-        elif not user_msg and chat_history is not None and len(chat_history) > 0:
+        elif (
+            not user_msg
+            and chat_history is not None
+            and len(chat_history) > 0
+            and isinstance(chat_history[-1].content, str)
+        ):
             user_msg = chat_history[-1].content
         else:
             raise ValueError("No user message provided or found in chat history.")
@@ -813,11 +818,16 @@ async def apredict_and_call(
             handle_reasoning_failure_fn=kwargs.get("handle_reasoning_failure_fn", None),
         )
 
-        if isinstance(user_msg, ChatMessage):
+        if isinstance(user_msg, ChatMessage) and isinstance(user_msg.content, str):
             user_msg = user_msg.content
         elif isinstance(user_msg, str):
             pass
-        elif not user_msg and chat_history is not None and len(chat_history) > 0:
+        elif (
+            not user_msg
+            and chat_history is not None
+            and len(chat_history) > 0
+            and isinstance(chat_history[-1].content, str)
+        ):
             user_msg = chat_history[-1].content
         else:
             raise ValueError("No user message provided or found in chat history.")
diff --git a/llama-index-core/llama_index/core/memory/chat_summary_memory_buffer.py b/llama-index-core/llama_index/core/memory/chat_summary_memory_buffer.py
index 8770e8f1f491b..45f25781d3c4f 100644
--- a/llama-index-core/llama_index/core/memory/chat_summary_memory_buffer.py
+++ b/llama-index-core/llama_index/core/memory/chat_summary_memory_buffer.py
@@ -286,6 +286,9 @@ def _get_prompt_to_summarize(
         # TODO: This probably works better when question/answers are considered together.
         prompt = '"Transcript so far: '
         for msg in chat_history_to_be_summarized:
+            if not isinstance(msg.content, str):
+                continue
+
             prompt += msg.role + ": "
             if msg.content:
                 prompt += msg.content + "\n\n"
diff --git a/llama-index-core/llama_index/core/prompts/base.py b/llama-index-core/llama_index/core/prompts/base.py
index 80982d9f80f60..bf62357a69a76 100644
--- a/llama-index-core/llama_index/core/prompts/base.py
+++ b/llama-index-core/llama_index/core/prompts/base.py
@@ -304,7 +304,9 @@ def format_messages(
 
         messages: List[ChatMessage] = []
         for message_template in self.message_templates:
-            template_vars = get_template_vars(message_template.content or "")
+            message_content = message_template.content or ""
+
+            template_vars = get_template_vars(message_content)
             relevant_kwargs = {
                 k: v for k, v in mapped_all_kwargs.items() if k in template_vars
             }
diff --git a/llama-index-core/llama_index/core/types.py b/llama-index-core/llama_index/core/types.py
index 63cd2365197da..4c7a0d84efc53 100644
--- a/llama-index-core/llama_index/core/types.py
+++ b/llama-index-core/llama_index/core/types.py
@@ -53,9 +53,11 @@ def format_messages(self, messages: List[ChatMessage]) -> List[ChatMessage]:
         #       or the last message
         if messages:
             if messages[0].role == MessageRole.SYSTEM:
-                messages[0].content = self.format(messages[0].content or "")
+                message_content = messages[0].content or ""
+                messages[0].content = self.format(message_content)
             else:
-                messages[-1].content = self.format(messages[-1].content or "")
+                message_content = messages[-1].content or ""
+                messages[-1].content = self.format(message_content)
 
         return messages
 
diff --git a/llama-index-core/llama_index/core/utilities/token_counting.py b/llama-index-core/llama_index/core/utilities/token_counting.py
index a06d0c14c3879..b6ddc9892f200 100644
--- a/llama-index-core/llama_index/core/utilities/token_counting.py
+++ b/llama-index-core/llama_index/core/utilities/token_counting.py
@@ -43,7 +43,7 @@ def estimate_tokens_in_messages(self, messages: List[ChatMessage]) -> int:
             if message.role:
                 tokens += self.get_string_tokens(message.role)
 
-            if message.content:
+            if isinstance(message.content, str):
                 tokens += self.get_string_tokens(message.content)
 
             additional_kwargs = {**message.additional_kwargs}
diff --git a/llama-index-integrations/agent/llama-index-agent-introspective/llama_index/agent/introspective/reflective/self_reflection.py b/llama-index-integrations/agent/llama-index-agent-introspective/llama_index/agent/introspective/reflective/self_reflection.py
index 9df7a8b6f48fc..d4740f13f1063 100644
--- a/llama-index-integrations/agent/llama-index-agent-introspective/llama_index/agent/introspective/reflective/self_reflection.py
+++ b/llama-index-integrations/agent/llama-index-agent-introspective/llama_index/agent/introspective/reflective/self_reflection.py
@@ -269,7 +269,9 @@ def run_step(self, step: TaskStep, task: Task, **kwargs: Any) -> TaskStepOutput:
         reflection, reflection_msg = self._reflect(chat_history=messages)
         is_done = reflection.is_done
 
-        critique_msg = ChatMessage(role=MessageRole.USER, content=reflection_msg)
+        critique_msg = ChatMessage(
+            role=MessageRole.USER, content=reflection_msg.content
+        )
         task.extra_state["new_memory"].put(critique_msg)
 
         # correction phase
@@ -386,7 +388,9 @@ async def arun_step(
         reflection, reflection_msg = await self._areflect(chat_history=messages)
         is_done = reflection.is_done
 
-        critique_msg = ChatMessage(role=MessageRole.USER, content=reflection_msg)
+        critique_msg = ChatMessage(
+            role=MessageRole.USER, content=reflection_msg.content
+        )
         task.extra_state["new_memory"].put(critique_msg)
 
         # correction phase