{%- set has_system = messages and messages[0].role == 'system' and messages[0].content is string %}
{%- if has_system %}
    {{- '<|im_start|>system\n' + messages[0].content + '<|im_end|>\n' }}
{%- endif %}
{%- if messages and messages[-1].role == 'assistant' %}
    {# Find the user message immediately before the last assistant (scan backwards skipping last). #}
    {%- set ns = namespace(seen_last=false, user_before_last_asst=none) %}
    {%- for m in messages[::-1] %}
        {%- if not ns.seen_last %}
            {%- set ns.seen_last = true %}
        {%- elif ns.user_before_last_asst is none and m.role == 'user' and m.content is string %}
            {%- set ns.user_before_last_asst = m.content %}
        {%- endif %}
    {%- endfor %}
    {%- if ns.user_before_last_asst is not none %}
        {{- '<|im_start|>user\n' + ns.user_before_last_asst + '<|im_end|>\n' }}
    {%- endif %}

    {%- set content = '' %}
    {%- if messages[-1].content is string %}
        {%- set content = messages[-1].content %}
    {%- endif %}
    {%- set reasoning_content = '' %}
    {%- if messages[-1].reasoning_content is string %}
        {%- set reasoning_content = messages[-1].reasoning_content %}
    {%- else %}
        {%- if '</think>' in content %}
            {%- set reasoning_content = content.split('</think>')[0].rstrip('\n').split('<think>')[-1].lstrip('\n') %}
            {%- set content = content.split('</think>')[-1].lstrip('\n') %}
        {%- endif %}
    {%- endif %}
    {%- if reasoning_content %}
        {{- '<|im_start|>assistant\n<think>\n' + reasoning_content.strip('\n') + '\n</think>\n\n' + content.lstrip('\n') + '<|im_end|>\n' }}
    {%- else %}
        {{- '<|im_start|>assistant\n' + content + '<|im_end|>\n' }}
    {%- endif %}
{%- elif messages and messages[-1].role == 'user' and messages[-1].content is string %}
    {{- '<|im_start|>user\n' + messages[-1].content + '<|im_end|>\n' }}
{%- endif %}
{%- if add_generation_prompt %}
    {{- '<|im_start|>assistant\n' }}
{%- endif %}