diff --git a/src/google/adk/flows/llm_flows/contents.py b/src/google/adk/flows/llm_flows/contents.py
index 425ed9b3..2ce917ba 100644
--- a/src/google/adk/flows/llm_flows/contents.py
+++ b/src/google/adk/flows/llm_flows/contents.py
@@ -41,6 +41,10 @@ class _ContentLlmRequestProcessor(BaseLlmRequestProcessor):
 
     agent = invocation_context.agent
 
+    # Preserve all contents that were added by instruction processor
+    # (since llm_request.contents will be completely reassigned below)
+    instruction_related_contents = llm_request.contents
+
     if agent.include_contents == 'default':
       # Include full conversation history
       llm_request.contents = _get_contents(
@@ -56,9 +60,9 @@ class _ContentLlmRequestProcessor(BaseLlmRequestProcessor):
           agent.name,
       )
 
-    # Add dynamic instructions to the last user content if static instructions exist
-    await _add_dynamic_instructions_to_user_content(
-        invocation_context, llm_request
+    # Add instruction-related contents to proper position in conversation
+    await _add_instructions_to_user_content(
+        invocation_context, llm_request, instruction_related_contents
     )
 
     # Maintain async generator behavior
@@ -562,47 +566,41 @@ def _is_live_model_audio_event(event: Event) -> bool:
   return False
 
 
-async def _add_dynamic_instructions_to_user_content(
-    invocation_context: InvocationContext, llm_request: LlmRequest
+async def _add_instructions_to_user_content(
+    invocation_context: InvocationContext,
+    llm_request: LlmRequest,
+    instruction_contents: list,
 ) -> None:
-  """Add dynamic instructions to the last user content when static instructions exist."""
-  from ...agents.readonly_context import ReadonlyContext
-  from ...utils import instructions_utils
+  """Insert instruction-related contents at proper position in conversation.
 
-  agent = invocation_context.agent
+  This function inserts instruction-related contents (passed as parameter) at the
+  proper position in the conversation flow, specifically before the last continuous
+  batch of user content to maintain conversation context.
 
-  dynamic_instructions = []
-
-  # Handle agent dynamic instructions if static instruction exists
-  if agent.static_instruction and agent.instruction:
-    # Static instruction exists, so add dynamic instruction to content
-    raw_si, bypass_state_injection = await agent.canonical_instruction(
-        ReadonlyContext(invocation_context)
-    )
-    si = raw_si
-    if not bypass_state_injection:
-      si = await instructions_utils.inject_session_state(
-          raw_si, ReadonlyContext(invocation_context)
-      )
-    if si:  # Only add if not empty
-      dynamic_instructions.append(si)
-
-  if not dynamic_instructions:
+  Args:
+    invocation_context: The invocation context
+    llm_request: The LLM request to modify
+    instruction_contents: List of instruction-related contents to insert
+  """
+  if not instruction_contents:
     return
 
-  # Find the start of the last continuous batch of user content
-  # Walk backwards to find the first non-user content, then insert before next user content
+  # Find the insertion point: before the last continuous batch of user content
+  # Walk backwards to find the first non-user content, then insert after it
   insert_index = len(llm_request.contents)
-  for i in range(len(llm_request.contents) - 1, -1, -1):
-    if llm_request.contents[i].role != 'user':
-      insert_index = i + 1
-      break
-    elif i == 0:
-      # All content from start is user content
-      insert_index = 0
-      break
 
-  # Create new user content with dynamic instructions
-  instruction_parts = [types.Part(text=instr) for instr in dynamic_instructions]
-  new_content = types.Content(role='user', parts=instruction_parts)
-  llm_request.contents.insert(insert_index, new_content)
+  if llm_request.contents:
+    for i in range(len(llm_request.contents) - 1, -1, -1):
+      if llm_request.contents[i].role != 'user':
+        insert_index = i + 1
+        break
+      elif i == 0:
+        # All content from start is user content
+        insert_index = 0
+        break
+  else:
+    # No contents remaining, just append at the end
+    insert_index = 0
+
+  # Insert all instruction contents at the proper position using efficient slicing
+  llm_request.contents[insert_index:insert_index] = instruction_contents
diff --git a/src/google/adk/flows/llm_flows/instructions.py b/src/google/adk/flows/llm_flows/instructions.py
index 70c307d6..bcdc6f56 100644
--- a/src/google/adk/flows/llm_flows/instructions.py
+++ b/src/google/adk/flows/llm_flows/instructions.py
@@ -34,6 +34,28 @@ if TYPE_CHECKING:
 class _InstructionsLlmRequestProcessor(BaseLlmRequestProcessor):
   """Handles instructions and global instructions for LLM flow."""
 
+  async def _process_agent_instruction(
+      self, agent, invocation_context: InvocationContext
+  ) -> str:
+    """Process agent instruction with state injection.
+
+    Args:
+      agent: The agent with instruction to process
+      invocation_context: The invocation context
+
+    Returns:
+      The processed instruction text
+    """
+    raw_si, bypass_state_injection = await agent.canonical_instruction(
+        ReadonlyContext(invocation_context)
+    )
+    si = raw_si
+    if not bypass_state_injection:
+      si = await instructions_utils.inject_session_state(
+          raw_si, ReadonlyContext(invocation_context)
+      )
+    return si
+
   @override
   async def run_async(
       self, invocation_context: InvocationContext, llm_request: LlmRequest
@@ -66,16 +88,16 @@ class _InstructionsLlmRequestProcessor(BaseLlmRequestProcessor):
     # Handle instruction based on whether static_instruction exists
     if agent.instruction and not agent.static_instruction:
       # Only add to system instructions if no static instruction exists
-      # If static instruction exists, content processor will handle it
-      raw_si, bypass_state_injection = await agent.canonical_instruction(
-          ReadonlyContext(invocation_context)
-      )
-      si = raw_si
-      if not bypass_state_injection:
-        si = await instructions_utils.inject_session_state(
-            raw_si, ReadonlyContext(invocation_context)
-        )
+      si = await self._process_agent_instruction(agent, invocation_context)
       llm_request.append_instructions([si])
+    elif agent.instruction and agent.static_instruction:
+      # Static instruction exists, so add dynamic instruction to content
+      from google.genai import types
+
+      si = await self._process_agent_instruction(agent, invocation_context)
+      # Create user content for dynamic instruction
+      dynamic_content = types.Content(role='user', parts=[types.Part(text=si)])
+      llm_request.contents.append(dynamic_content)
 
     # Maintain async generator behavior
     return
diff --git a/src/google/adk/models/llm_request.py b/src/google/adk/models/llm_request.py
index aa898ef7..814e0dbe 100644
--- a/src/google/adk/models/llm_request.py
+++ b/src/google/adk/models/llm_request.py
@@ -90,7 +90,7 @@ class LlmRequest(BaseModel):
 
   def append_instructions(
       self, instructions: Union[list[str], types.Content]
-  ) -> None:
+  ) -> list[types.Content]:
     """Appends instructions to the system instruction.
 
     Args:
@@ -98,46 +98,120 @@ class LlmRequest(BaseModel):
         - list[str]: Strings to append/concatenate to system instruction
         - types.Content: Content object to append to system instruction
 
-    Note: Only text content is supported. Model API requires system_instruction
-    to be a string. Non-text parts in Content will be handled differently.
+    Returns:
+      List of user contents from non-text parts (when instructions is types.Content
+      with non-text parts). Empty list otherwise.
+
+    Note: Model API requires system_instruction to be a string. Non-text parts
+    in Content are processed with references in system_instruction and returned
+    as user contents.
 
     Behavior:
       - list[str]: concatenates with existing system_instruction using \\n\\n
-      - types.Content: extracts text from parts and concatenates
+      - types.Content: extracts text parts with references to non-text parts,
+        returns non-text parts as user contents
     """
 
-    # Handle Content object - extract only text parts
+    # Handle Content object
     if isinstance(instructions, types.Content):
-      # TODO: Handle non-text contents in instruction by putting non-text parts
-      # into llm_request.contents and adding a reference in the system instruction
-      # that references the contents.
+      text_parts = []
+      user_contents = []
 
-      # Extract text from all text parts
-      text_parts = [part.text for part in instructions.parts if part.text]
+      # Process all parts, creating references for non-text parts
+      non_text_count = 0
+      for part in instructions.parts:
+        if part.text:
+          # Text part - add to system instruction
+          text_parts.append(part.text)
+        elif part.inline_data:
+          # Inline data part - create reference and user content
+          reference_id = f"inline_data_{non_text_count}"
+          non_text_count += 1
 
-      if not text_parts:
-        return  # No text content to append
+          # Create descriptive reference based on mime_type and display_name
+          display_info = []
+          if part.inline_data.display_name:
+            display_info.append(f"'{part.inline_data.display_name}'")
+          if part.inline_data.mime_type:
+            display_info.append(f"type: {part.inline_data.mime_type}")
 
-      new_text = "\n\n".join(text_parts)
-      if not self.config.system_instruction:
-        self.config.system_instruction = new_text
-      elif isinstance(self.config.system_instruction, str):
-        self.config.system_instruction += "\n\n" + new_text
-      else:
-        # Log warning for unsupported system_instruction types
-        logging.warning(
-            "Cannot append to system_instruction of unsupported type: %s. "
-            "Only string system_instruction is supported.",
-            type(self.config.system_instruction),
-        )
-      return
+          display_text = f" ({', '.join(display_info)})" if display_info else ""
+          reference_text = (
+              f"[Reference to inline binary data: {reference_id}{display_text}]"
+          )
+          text_parts.append(reference_text)
+
+          # Create user content with reference and data
+          user_content = types.Content(
+              role="user",
+              parts=[
+                  types.Part.from_text(
+                      text=f"Referenced inline data: {reference_id}"
+                  ),
+                  types.Part(inline_data=part.inline_data),
+              ],
+          )
+          user_contents.append(user_content)
+
+        elif part.file_data:
+          # File data part - create reference and user content
+          reference_id = f"file_data_{non_text_count}"
+          non_text_count += 1
+
+          # Create descriptive reference based on file_uri and display_name
+          display_info = []
+          if part.file_data.display_name:
+            display_info.append(f"'{part.file_data.display_name}'")
+          if part.file_data.file_uri:
+            display_info.append(f"URI: {part.file_data.file_uri}")
+          if part.file_data.mime_type:
+            display_info.append(f"type: {part.file_data.mime_type}")
+
+          display_text = f" ({', '.join(display_info)})" if display_info else ""
+          reference_text = (
+              f"[Reference to file data: {reference_id}{display_text}]"
+          )
+          text_parts.append(reference_text)
+
+          # Create user content with reference and file data
+          user_content = types.Content(
+              role="user",
+              parts=[
+                  types.Part.from_text(
+                      text=f"Referenced file data: {reference_id}"
+                  ),
+                  types.Part(file_data=part.file_data),
+              ],
+          )
+          user_contents.append(user_content)
+
+      # Handle text parts for system instruction
+      if text_parts:
+        new_text = "\n\n".join(text_parts)
+        if not self.config.system_instruction:
+          self.config.system_instruction = new_text
+        elif isinstance(self.config.system_instruction, str):
+          self.config.system_instruction += "\n\n" + new_text
+        else:
+          # Log warning for unsupported system_instruction types
+          logging.warning(
+              "Cannot append to system_instruction of unsupported type: %s. "
+              "Only string system_instruction is supported.",
+              type(self.config.system_instruction),
+          )
+
+      # Add user contents directly to llm_request.contents
+      if user_contents:
+        self.contents.extend(user_contents)
+
+      return user_contents
 
     # Handle list of strings
     if isinstance(instructions, list) and all(
         isinstance(inst, str) for inst in instructions
     ):
       if not instructions:  # Handle empty list
-        return
+        return []
 
       new_text = "\n\n".join(instructions)
       if not self.config.system_instruction:
@@ -151,7 +225,7 @@ class LlmRequest(BaseModel):
             "Only string system_instruction is supported.",
             type(self.config.system_instruction),
         )
-      return
+      return []
 
     # Invalid input
     raise TypeError("instructions must be list[str] or types.Content")
diff --git a/tests/unittests/agents/test_static_instructions.py b/tests/unittests/agents/test_static_instructions.py
index 912a062b..3d20e5cf 100644
--- a/tests/unittests/agents/test_static_instructions.py
+++ b/tests/unittests/agents/test_static_instructions.py
@@ -17,7 +17,8 @@
 from google.adk.agents.invocation_context import InvocationContext
 from google.adk.agents.llm_agent import LlmAgent
 from google.adk.agents.run_config import RunConfig
-from google.adk.flows.llm_flows.contents import _add_dynamic_instructions_to_user_content
+from google.adk.flows.llm_flows.contents import _add_instructions_to_user_content
+from google.adk.flows.llm_flows.contents import request_processor as contents_processor
 from google.adk.flows.llm_flows.instructions import request_processor
 from google.adk.models.llm_request import LlmRequest
 from google.adk.sessions.in_memory_session_service import InMemorySessionService
@@ -148,9 +149,17 @@ class TestStaticInstructions:
       pass
 
     # Static instruction should be in system instructions
-    assert len(llm_request.contents) == 0
+    # Dynamic instruction should be added as user content by instruction processor
+    assert len(llm_request.contents) == 1
     assert llm_request.config.system_instruction == 'Static instruction content'
 
+    # Check that dynamic instruction was added as user content
+    assert llm_request.contents[0].role == 'user'
+    assert len(llm_request.contents[0].parts) == 1
+    assert (
+        llm_request.contents[0].parts[0].text == 'Dynamic instruction content'
+    )
+
   @pytest.mark.asyncio
   async def test_dynamic_instructions_added_to_user_content(self, llm_backend):
     """Test that dynamic instructions are added to user content when static exists."""
@@ -166,16 +175,22 @@ class TestStaticInstructions:
     invocation_context = await _create_invocation_context(agent)
 
     llm_request = LlmRequest()
-    # Add some existing user content
-    llm_request.contents = [
-        types.Content(role='user', parts=[types.Part(text='Hello world')])
-    ]
 
-    # Run the content processor function
-    await _add_dynamic_instructions_to_user_content(
-        invocation_context, llm_request
+    # Run the instruction processor to add dynamic instruction
+    async for _ in request_processor.run_async(invocation_context, llm_request):
+      pass
+
+    # Add some existing user content to simulate conversation history
+    llm_request.contents.append(
+        types.Content(role='user', parts=[types.Part(text='Hello world')])
     )
 
+    # Run the content processor to move instructions to proper position
+    async for _ in contents_processor.run_async(
+        invocation_context, llm_request
+    ):
+      pass
+
     # Dynamic instruction should be inserted before the last continuous batch of user content
     assert len(llm_request.contents) == 2
     assert llm_request.contents[0].role == 'user'
@@ -204,10 +219,15 @@ class TestStaticInstructions:
     llm_request = LlmRequest()
     # No existing content
 
-    # Run the content processor function
-    await _add_dynamic_instructions_to_user_content(
+    # Run the instruction processor to add dynamic instruction
+    async for _ in request_processor.run_async(invocation_context, llm_request):
+      pass
+
+    # Run the content processor to handle any positioning (no change expected for single content)
+    async for _ in contents_processor.run_async(
         invocation_context, llm_request
-    )
+    ):
+      pass
 
     # Dynamic instruction should create new user content
     assert len(llm_request.contents) == 1
@@ -230,9 +250,7 @@ class TestStaticInstructions:
     llm_request.contents = [original_content]
 
     # Run the content processor function
-    await _add_dynamic_instructions_to_user_content(
-        invocation_context, llm_request
-    )
+    await _add_instructions_to_user_content(invocation_context, llm_request, [])
 
     # Content should remain unchanged
     assert len(llm_request.contents) == 1
@@ -264,9 +282,216 @@ class TestStaticInstructions:
     async for _ in request_processor.run_async(invocation_context, llm_request):
       pass
 
-    # Static instruction should extract only text parts and concatenate them
-    assert len(llm_request.contents) == 0
+    # Static instruction should contain text parts with references to non-text parts
+    assert len(llm_request.contents) == 1
     assert (
         llm_request.config.system_instruction
-        == 'Analyze this image:\n\nFocus on the key elements.'
+        == 'Analyze this image:\n\n[Reference to inline binary data:'
+        ' inline_data_0 (type: image/png)]\n\nFocus on the key elements.'
     )
+
+    # The non-text part should be in user content
+    assert llm_request.contents[0].role == 'user'
+    assert len(llm_request.contents[0].parts) == 2
+    assert (
+        llm_request.contents[0].parts[0].text
+        == 'Referenced inline data: inline_data_0'
+    )
+    assert llm_request.contents[0].parts[1].inline_data
+    assert (
+        llm_request.contents[0].parts[1].inline_data.data == b'fake_image_data'
+    )
+
+  @pytest.mark.asyncio
+  async def test_static_instruction_non_text_parts_moved_to_user_content(
+      self, llm_backend
+  ):
+    """Test that non-text parts from static instruction are moved to user content."""
+    static_content = types.Content(
+        role='user',
+        parts=[
+            types.Part(text='Analyze this image:'),
+            types.Part(
+                inline_data=types.Blob(
+                    data=b'fake_image_data',
+                    mime_type='image/png',
+                    display_name='test_image.png',
+                )
+            ),
+            types.Part(
+                file_data=types.FileData(
+                    file_uri='files/test123',
+                    mime_type='text/plain',
+                    display_name='test_file.txt',
+                )
+            ),
+            types.Part(text='Focus on the key elements.'),
+        ],
+    )
+    agent = LlmAgent(name='test_agent', static_instruction=static_content)
+
+    invocation_context = await _create_invocation_context(agent)
+    llm_request = LlmRequest()
+
+    # Run the instruction processor
+    async for _ in request_processor.run_async(invocation_context, llm_request):
+      pass
+
+    # Run the contents processor to move non-text parts
+    async for _ in contents_processor.run_async(
+        invocation_context, llm_request
+    ):
+      pass
+
+    # System instruction should contain text with references
+    expected_system = (
+        'Analyze this image:\n\n[Reference to inline binary data: inline_data_0'
+        " ('test_image.png', type: image/png)]\n\n[Reference to file data:"
+        " file_data_1 ('test_file.txt', URI: files/test123, type:"
+        ' text/plain)]\n\nFocus on the key elements.'
+    )
+    assert llm_request.config.system_instruction == expected_system
+
+    # Non-text parts should be moved to user content
+    assert len(llm_request.contents) == 2
+
+    # Check first content object (inline_data)
+    inline_content = llm_request.contents[0]
+    assert inline_content.role == 'user'
+    assert len(inline_content.parts) == 2
+    assert (
+        inline_content.parts[0].text == 'Referenced inline data: inline_data_0'
+    )
+    assert inline_content.parts[1].inline_data
+    assert inline_content.parts[1].inline_data.data == b'fake_image_data'
+    assert inline_content.parts[1].inline_data.mime_type == 'image/png'
+    assert inline_content.parts[1].inline_data.display_name == 'test_image.png'
+
+    # Check second content object (file_data)
+    file_content = llm_request.contents[1]
+    assert file_content.role == 'user'
+    assert len(file_content.parts) == 2
+    assert file_content.parts[0].text == 'Referenced file data: file_data_1'
+    assert file_content.parts[1].file_data
+    assert file_content.parts[1].file_data.file_uri == 'files/test123'
+    assert file_content.parts[1].file_data.mime_type == 'text/plain'
+    assert file_content.parts[1].file_data.display_name == 'test_file.txt'
+
+  @pytest.mark.asyncio
+  async def test_static_instruction_reference_id_generation(self, llm_backend):
+    """Test that reference IDs are generated correctly for non-text parts."""
+    static_content = types.Content(
+        role='user',
+        parts=[
+            types.Part(text='Multiple files:'),
+            types.Part(
+                inline_data=types.Blob(data=b'data1', mime_type='image/png')
+            ),
+            types.Part(
+                file_data=types.FileData(
+                    file_uri='files/test1', mime_type='text/plain'
+                )
+            ),
+            types.Part(
+                inline_data=types.Blob(data=b'data2', mime_type='image/jpeg')
+            ),
+        ],
+    )
+    agent = LlmAgent(name='test_agent', static_instruction=static_content)
+
+    invocation_context = await _create_invocation_context(agent)
+    llm_request = LlmRequest()
+
+    # Run the instruction processor
+    async for _ in request_processor.run_async(invocation_context, llm_request):
+      pass
+
+    # Run the contents processor to move non-text parts
+    async for _ in contents_processor.run_async(
+        invocation_context, llm_request
+    ):
+      pass
+
+    # System instruction should contain sequential reference IDs
+    expected_system = (
+        'Multiple files:\n\n[Reference to inline binary data: inline_data_0'
+        ' (type: image/png)]\n\n[Reference to file data: file_data_1 (URI:'
+        ' files/test1, type: text/plain)]\n\n[Reference to inline binary data:'
+        ' inline_data_2 (type: image/jpeg)]'
+    )
+    assert llm_request.config.system_instruction == expected_system
+
+    # All non-text parts should be in user content
+    assert len(llm_request.contents) == 3
+    # Each non-text part gets its own content object with 2 parts (text description + actual part)
+    for content in llm_request.contents:
+      assert len(content.parts) == 2
+
+  @pytest.mark.asyncio
+  async def test_static_instruction_only_text_parts(self, llm_backend):
+    """Test that static instruction with only text parts works normally."""
+    static_content = types.Content(
+        role='user',
+        parts=[
+            types.Part(text='First part'),
+            types.Part(text='Second part'),
+        ],
+    )
+    agent = LlmAgent(name='test_agent', static_instruction=static_content)
+
+    invocation_context = await _create_invocation_context(agent)
+    llm_request = LlmRequest()
+
+    # Run the instruction processor
+    async for _ in request_processor.run_async(invocation_context, llm_request):
+      pass
+
+    # Only text should be in system instruction
+    assert llm_request.config.system_instruction == 'First part\n\nSecond part'
+    # No user content should be created
+    assert len(llm_request.contents) == 0
+
+  @pytest.mark.asyncio
+  async def test_static_instruction_only_non_text_parts(self, llm_backend):
+    """Test that static instruction with only non-text parts works correctly."""
+    static_content = types.Content(
+        role='user',
+        parts=[
+            types.Part(
+                inline_data=types.Blob(data=b'data', mime_type='image/png')
+            ),
+            types.Part(
+                file_data=types.FileData(
+                    file_uri='files/test', mime_type='text/plain'
+                )
+            ),
+        ],
+    )
+    agent = LlmAgent(name='test_agent', static_instruction=static_content)
+
+    invocation_context = await _create_invocation_context(agent)
+    llm_request = LlmRequest()
+
+    # Run the instruction processor
+    async for _ in request_processor.run_async(invocation_context, llm_request):
+      pass
+
+    # Run the contents processor to move non-text parts
+    async for _ in contents_processor.run_async(
+        invocation_context, llm_request
+    ):
+      pass
+
+    # System instruction should contain only references
+    expected_system = (
+        '[Reference to inline binary data: inline_data_0 (type:'
+        ' image/png)]\n\n[Reference to file data: file_data_1 (URI: files/test,'
+        ' type: text/plain)]'
+    )
+    assert llm_request.config.system_instruction == expected_system
+
+    # All parts should be in user content
+    assert len(llm_request.contents) == 2
+    # Each non-text part gets its own content object with 2 parts (text description + actual part)
+    for content in llm_request.contents:
+      assert len(content.parts) == 2
diff --git a/tests/unittests/models/test_llm_request.py b/tests/unittests/models/test_llm_request.py
index b0722291..2c2f6a0a 100644
--- a/tests/unittests/models/test_llm_request.py
+++ b/tests/unittests/models/test_llm_request.py
@@ -625,7 +625,7 @@ def test_append_instructions_content_extracts_text_only():
 
 
 def test_append_instructions_content_with_non_text_parts():
-  """Test that non-text parts in Content are ignored."""
+  """Test that non-text parts in Content are processed with references."""
   request = LlmRequest()
 
   # Create Content with text and non-text parts
@@ -640,14 +640,28 @@ def test_append_instructions_content_with_non_text_parts():
       ],
   )
 
-  request.append_instructions(content)
+  user_contents = request.append_instructions(content)
 
-  # Only text parts should be extracted
-  assert request.config.system_instruction == 'Text instruction\n\nMore text'
+  # Text parts should be extracted with references to non-text parts
+  expected_system = (
+      'Text instruction\n\n'
+      '[Reference to inline binary data: inline_data_0 (type: text/plain)]\n\n'
+      'More text'
+  )
+  assert request.config.system_instruction == expected_system
+
+  # Should return user content for the non-text part
+  assert len(user_contents) == 1
+  assert user_contents[0].role == 'user'
+  assert len(user_contents[0].parts) == 2
+  assert (
+      user_contents[0].parts[0].text == 'Referenced inline data: inline_data_0'
+  )
+  assert user_contents[0].parts[1].inline_data.data == b'file_data'
 
 
 def test_append_instructions_content_no_text_parts():
-  """Test that Content with no text parts does nothing."""
+  """Test that Content with no text parts processes non-text parts with references."""
   request = LlmRequest()
 
   # Set initial system instruction
@@ -663,10 +677,23 @@ def test_append_instructions_content_no_text_parts():
       ],
   )
 
-  request.append_instructions(content)
+  user_contents = request.append_instructions(content)
 
-  # Should remain unchanged since no text to extract
-  assert request.config.system_instruction == 'Initial'
+  # Should add reference to non-text part to system instruction
+  expected_system = (
+      'Initial\n\n[Reference to inline binary data: inline_data_0 (type:'
+      ' text/plain)]'
+  )
+  assert request.config.system_instruction == expected_system
+
+  # Should return user content for the non-text part
+  assert len(user_contents) == 1
+  assert user_contents[0].role == 'user'
+  assert len(user_contents[0].parts) == 2
+  assert (
+      user_contents[0].parts[0].text == 'Referenced inline data: inline_data_0'
+  )
+  assert user_contents[0].parts[1].inline_data.data == b'file_data'
 
 
 def test_append_instructions_content_empty_text_parts():
@@ -725,3 +752,87 @@ def test_append_instructions_warning_unsupported_system_instruction_type(
   assert (
       'Cannot append to system_instruction of unsupported type' in caplog.text
   )
+
+
+@pytest.mark.parametrize('llm_backend', ['GOOGLE_AI', 'VERTEX'])
+def test_append_instructions_with_mixed_content(llm_backend):
+  """Test append_instructions with mixed text and non-text content."""
+  request = LlmRequest()
+
+  # Create static instruction with mixed content
+  static_content = types.Content(
+      role='user',
+      parts=[
+          types.Part(text='Analyze this:'),
+          types.Part(
+              inline_data=types.Blob(
+                  data=b'test_data',
+                  mime_type='image/png',
+                  display_name='test.png',
+              )
+          ),
+          types.Part(text='Focus on details.'),
+          types.Part(
+              file_data=types.FileData(
+                  file_uri='files/doc123',
+                  mime_type='text/plain',
+                  display_name='document.txt',
+              )
+          ),
+      ],
+  )
+
+  user_contents = request.append_instructions(static_content)
+
+  # System instruction should contain text with references
+  expected_system = (
+      'Analyze this:\n\n[Reference to inline binary data: inline_data_0'
+      " ('test.png', type: image/png)]\n\nFocus on details.\n\n[Reference to"
+      " file data: file_data_1 ('document.txt', URI: files/doc123, type:"
+      ' text/plain)]'
+  )
+  assert request.config.system_instruction == expected_system
+
+  # Should return user contents for non-text parts
+  assert len(user_contents) == 2
+
+  # Check inline_data content
+  assert user_contents[0].role == 'user'
+  assert len(user_contents[0].parts) == 2
+  assert (
+      user_contents[0].parts[0].text == 'Referenced inline data: inline_data_0'
+  )
+  assert user_contents[0].parts[1].inline_data.data == b'test_data'
+  assert user_contents[0].parts[1].inline_data.display_name == 'test.png'
+
+  # Check file_data content
+  assert user_contents[1].role == 'user'
+  assert len(user_contents[1].parts) == 2
+  assert user_contents[1].parts[0].text == 'Referenced file data: file_data_1'
+  assert user_contents[1].parts[1].file_data.file_uri == 'files/doc123'
+  assert user_contents[1].parts[1].file_data.display_name == 'document.txt'
+
+
+@pytest.mark.parametrize('llm_backend', ['GOOGLE_AI', 'VERTEX'])
+def test_append_instructions_with_only_text_parts(llm_backend):
+  """Test append_instructions with only text parts."""
+  request = LlmRequest()
+
+  static_content = types.Content(
+      role='user',
+      parts=[
+          types.Part(text='First instruction'),
+          types.Part(text='Second instruction'),
+      ],
+  )
+
+  user_contents = request.append_instructions(static_content)
+
+  # Should only have text in system instruction
+  assert (
+      request.config.system_instruction
+      == 'First instruction\n\nSecond instruction'
+  )
+
+  # Should return empty list since no non-text parts
+  assert user_contents == []