{#- ─────────────────────────────────────────────────────────────────────────
    Proteus Chat Template
    ─────────────────────────────────────────────────────────────────────────

    Token legend
    ────────────
    <|BOS|>           – begins every sequence
    <|SYSTEM_START|>  / <|SYSTEM_END|>  – system prompt wrapper (optional)
    <|USER_START|>    / <|USER_END|>    – user turn wrapper
    <|AGENT_START|>   / <|AGENT_END|>   – assistant turn wrapper
    <|EOS|>           – ends every assistant turn

    Wire format (no extra whitespace between special tokens)
    ─────────────────────────────────────────────────────────
    <|BOS|>
    [<|SYSTEM_START|>{system}<|SYSTEM_END|>]   ← optional, at most once
    <|USER_START|>{user}<|USER_END|>
    <|AGENT_START|>{reply}<|AGENT_END|><|EOS|>
    ... repeated for further turns ...
    <|USER_START|>{user}<|USER_END|>
    <|AGENT_START|>                            ← generation prompt only
    ───────────────────────────────────────────────────────────────────────── -#}

{{- bos_token -}}

{#- ── System message (at most once, from the first role="system" entry) ── -#}
{%- if messages[0]['role'] == 'system' -%}
    {{- '<|SYSTEM_START|>' + messages[0]['content'] | trim + '<|SYSTEM_END|>' -}}
    {%- set messages = messages[1:] -%}
{%- endif -%}

{#- ── Conversation turns ──────────────────────────────────────────────── -#}
{%- for message in messages -%}

    {%- if message['role'] == 'user' -%}
        {{- '<|USER_START|>' + message['content'] | trim + '<|USER_END|>' -}}

    {%- elif message['role'] == 'assistant' -%}
        {{- '<|AGENT_START|>' + message['content'] | trim + '<|AGENT_END|>' + eos_token -}}

    {%- else -%}
        {{- raise_exception("Unsupported role: " + message['role']) -}}
    {%- endif -%}

{%- endfor -%}

{#- ── Generation prompt ───────────────────────────────────────────────── -#}
{%- if add_generation_prompt -%}
    {{- '<|AGENT_START|>' -}}
{%- endif -%}