sgl-project/sglang · error · NotImplementedError

Unknown role: {role}

Error message

Unknown role: {role}

What it means

DSv4 render_message reached the final else branch: the message role matched none of the supported roles (user/developer/assistant/latest_reminder/tool handled earlier).

Source

Thrown at python/sglang/srt/entrypoints/openai/encoding_dsv4.py:438

                    thinking_template.format(reasoning_content=rc) + thinking_end_token
                )
            else:
                thinking_part = ""

        if wo_eos:
            prompt += assistant_msg_wo_eos_template.format(
                reasoning=thinking_part,
                content=summary_content,
                tool_calls=tc_content,
            )
        else:
            prompt += assistant_msg_template.format(
                reasoning=thinking_part,
                content=summary_content,
                tool_calls=tc_content,
            )
    else:
        raise NotImplementedError(f"Unknown role: {role}")

    # Append transition tokens based on what follows
    if index + 1 < len(messages) and messages[index + 1].get("role") not in [
        "assistant",
        "latest_reminder",
    ]:
        return prompt

    task = messages[index].get("task")
    if task is not None:
        # Task special token for internal classification tasks
        assert (
            task in VALID_TASKS
        ), f"Invalid task: '{task}'. Valid tasks are: {list(VALID_TASKS)}"
        task_sp_token = DS_TASK_SP_TOKENS[task]

        if task != "action":
            # Non-action tasks: append task sp token directly after the message

View on GitHub (pinned to 0132848349)

Solutions

1. Check msg['role'] spelling and use a supported role.
2. Map legacy roles: 'system'->'developer', 'function'->tool handling via merge_tool_messages.
3. Log roles before sending to catch bad values early.

Example fix

# before
{"role":"system","content":"You are..."}
# after
{"role":"developer","content":"You are..."}

ALLOWED={'user','developer','assistant','latest_reminder'}
assert all(m['role'] in ALLOWED for m in messages)

def is_dsv4_role(r): return r in {'user','developer','assistant','latest_reminder'}

When it happens

Trigger: A message with an unrecognized role such as 'system' in DSv4 (if unsupported), 'function', or a typo like 'asistant'.

Common situations: Role typos; using legacy roles; roles supported by other templates but not DSv4.

Related errors

• `task` requires at least one message with role='user' or 'de
• DSV4 draft state transfer expects SWA-only NextN layers
• DSV4 target and draft pools must use the same unified-KV mod
• DSV4 target and draft pools must share SWA ring geometry: ta
• DSV4 target and draft pools must share the SWA index mapping

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/9954fbfa8f8b3bd5. Report an issue: GitHub.