sgl-project/sglang · error · ValueError

Unknown browser action: {recipient}

Error message

Unknown browser action: {recipient}

What it means

The recipient string starts with 'browser.' but is not one of the recognized browser actions (browser.search, browser.find/open as handled above), so parse_output_message cannot map it to an ActionSearch/ActionFind and rejects it.

Source

Thrown at python/sglang/srt/entrypoints/harmony_utils.py:277

        content = message.content[0]
        browser_call = orjson.loads(content.text)
        # TODO: translate to url properly!
        if recipient == "browser.search":
            action = ActionSearch(
                query=f"cursor:{browser_call.get('query', '')}", type="search"
            )
        elif recipient == "browser.open":
            action = ActionOpenPage(
                url=f"cursor:{browser_call.get('url', '')}", type="open_page"
            )
        elif recipient == "browser.find":
            action = ActionFind(
                pattern=browser_call["pattern"],
                url=f"cursor:{browser_call.get('url', '')}",
                type="find",
            )
        else:
            raise ValueError(f"Unknown browser action: {recipient}")
        web_search_item = ResponseFunctionWebSearch(
            id=f"ws_{random_uuid()}",
            action=action,
            status="completed",
            type="web_search_call",
        )
        output_items.append(web_search_item)
    elif message.channel == "analysis":
        for content in message.content:
            reasoning_item = ResponseReasoningItem(
                id=f"rs_{random_uuid()}",
                type="reasoning",
                summary=[],
                content=[
                    ResponseReasoningTextContent(
                        text=content.text, type="reasoning_text"
                    )
                ],

View on GitHub (pinned to 0132848349)

Solutions

1. Restrict the advertised browser tools to browser.search/browser.find so the model only emits supported recipients
2. Add a parser branch in harmony_utils.py for the new browser action if you genuinely need it
3. Sanitize/normalize unknown browser.* recipients to a supported action or drop the message before parsing

Example fix

# before
msg.with_recipient("browser.click")
# after
msg.with_recipient("browser.search")  # only supported browser actions

SUPPORTED_BROWSER_ACTIONS = {"browser.search", "browser.find", "browser.open"}
if message.recipient in {None} | SUPPORTED_BROWSER_ACTIONS or not message.recipient.startswith("browser."):
    ...  # proceed

def is_supported_browser_action(recipient: str) -> bool:
    return not recipient.startswith("browser.") or recipient in {"browser.search", "browser.find", "browser.open"}

try:
    items = parse_output_message(message)
except ValueError as e:
    if "Unknown browser action" in str(e):
        return []  # ignore unsupported action
    raise

When it happens

Trigger: A message with recipient 'browser.click', 'browser.navigate', or any 'browser.<anything>' outside the supported action set reaching the parsing stage.

Common situations: Prompting the model to use browser tools the runtime doesn't implement; a new browser action added to the tool schema without a corresponding parser branch; model hallucinating tool names.

Related errors

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

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/30e721a0cc4fe7c1. Report an issue: GitHub.