{%- macro render_content(content) -%}
    {%- if content is string -%}
        {{- content -}}
    {%- elif content is iterable and content is not mapping -%}
        {%- for item in content -%}
            {%- if 'image' in item or 'image_url' in item or item.type == 'image' -%}
                {{- '<|vision_start|><|image_pad|><|vision_end|>' -}}
            {%- elif 'video' in item or 'video_url' in item or item.type == 'video' -%}
                {{- '<|vision_start|><|video_pad|><|vision_end|>' -}}
            {%- elif 'text' in item -%}
                {{- item.text -}}
            {%- else -%}
                {{- raise_exception('Unexpected item type in content.') -}}
            {%- endif -%}
        {%- endfor -%}
    {%- elif content is none or content is undefined -%}
        {{- '' -}}
    {%- else -%}
        {{- raise_exception('Unexpected content type.') -}}
    {%- endif -%}
{%- endmacro -%}

A chat between a user and an artificial intelligence assistant. The assistant gives helpful, detailed, and polite answers to the user's questions.
{%- set merged = namespace(user='', asst='') -%}
{%- for message in messages -%}
    {%- set raw_role = message['role'] -%}
    {%- set role = 'user' if raw_role in ['user','system'] else 'assistant' -%}
    {%- set content = render_content(message['content']) -%}

    {%- if role == 'user' -%}
        {%- set merged.user = merged.user + ('\n\n' if merged.user else '') + content -%}
    {%- else -%}
        {%- set merged.asst = merged.asst + ('\n\n' if merged.asst else '') + content -%}
    {%- endif -%}

    {%- set next_role = role -%}
    {%- if not loop.last -%}
        {%- set next_raw = messages[loop.index0+1]['role'] -%}
        {%- set next_role = 'user' if next_raw in ['user','system'] else 'assistant' -%}
    {%- endif -%}

    {%- if loop.last or next_role != role -%}
        {%- if role == 'user' -%}
            {{- '\n<|User|>\n' + merged.user + '\n<|Assistant|>\n' -}}
            {%- set merged.user = '' -%}
        {%- else -%}
            {{- merged.asst + '<|endoftext|>' -}}
            {%- set merged.asst = '' -%}
        {%- endif -%}
    {%- endif -%}
{%- endfor -%}