sgl-project/sglang · error · ValueError

Unknown channel: {message.channel}

Error message

Unknown channel: {message.channel}

What it means

parse_output_message only converts messages on the 'commentary' and 'final' channels; a message on any other channel (e.g. 'analysis' or a typo) falls through to this ValueError. The channel field is the top-level dispatch key for output formatting.

Source

Thrown at python/sglang/srt/entrypoints/harmony_utils.py:349

        contents = []
        for content in message.content:
            output_text = ResponseOutputText(
                text=content.text,
                annotations=[],  # TODO
                type="output_text",
                logprobs=None,  # TODO
            )
            contents.append(output_text)
        text_item = ResponseOutputMessage(
            id=f"msg_{random_uuid()}",
            content=contents,
            role=message.author.role,
            status="completed",
            type="message",
        )
        output_items.append(text_item)
    else:
        raise ValueError(f"Unknown channel: {message.channel}")
    return output_items


def parse_remaining_state(parser: StreamableParser):
    if not parser.current_content:
        return []
    if parser.current_role != Role.ASSISTANT:
        return []
    current_recipient = parser.current_recipient
    if current_recipient is not None and current_recipient.startswith("browser."):
        return []

    if parser.current_channel == "analysis":
        reasoning_item = ResponseReasoningItem(
            id=f"rs_{random_uuid()}",
            type="reasoning",
            summary=[],
            content=[

View on GitHub (pinned to 0132848349)

Solutions

1. Normalize message.channel to 'commentary' or 'final' before parsing
2. If the model emits a legitimate new channel, add a handling branch in harmony_utils.py
3. Upgrade sglang to match the harmony format version your model was trained on

Example fix

# before
msg = msg.copy_with(channel="analysis")
# after
msg = msg.copy_with(channel="commentary")

assert message.channel in {"commentary", "final"}, f"unexpected channel {message.channel!r}"

def is_supported_channel(message) -> bool:
    return message.channel in {"commentary", "final"}

try:
    items = parse_output_message(message)
except ValueError as e:
    if "Unknown channel" in str(e):
        message = message.copy_with(channel="commentary")
        items = parse_output_message(message)
    else:
        raise

When it happens

Trigger: A parsed harmony Message whose channel is anything other than 'commentary' or 'final' when handed to _make_response_output_items_with_harmony.

Common situations: Malformed model output emitting an unexpected channel token; older/newer harmony format versions using different channel names; custom harmony post-processing setting wrong channel values.

Related errors

• Unknown recipient: {message.recipient}
• No call message found for {call_id}
• Unknown input type: {response_msg['type']}
• Unknown output type: {type(output)}
• Invalid number of contents in browser message

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/885207434c5c5004. Report an issue: GitHub.