unclecode/crawl4ai · error · TypeError
.run must be async
Error message
{cls.__name__}.run must be async What it means
Error "{cls.__name__}.run must be async" thrown in unclecode/crawl4ai.
Solutions
- Declare the run method with async def so it can be awaited by the hub.
- Remove blocking synchronous calls from run or wrap them with asyncio.to_thread.
Example fix
async def run(self, url: str, **kwargs): ...
When it happens
Trigger: Thrown at crawl4ai/hub.py:35 when the library encounters an invalid state.
Common situations: See trigger scenarios.
AI-assisted analysis of unclecode/crawl4ai@7e80152142 (2026-08-14).
Data as JSON: /api/errors/6cdb14ab5b5ae1e3.
Report an issue: GitHub.
Appendix: source
Thrown at crawl4ai/hub.py:35
async def run(self, url: str = "", **kwargs) -> str:
"""
Implement this method to return JSON string.
Must accept URL + arbitrary kwargs for flexibility.
"""
pass
def __init_subclass__(cls, **kwargs):
"""Enforce interface validation on subclassing"""
super().__init_subclass__(**kwargs)
# Verify run method signature
run_method = cls.run
if not run_method.__code__.co_argcount >= 2: # self + url
raise TypeError(f"{cls.__name__} must implement 'run(self, url: str, **kwargs)'")
# Verify async nature
if not inspect.iscoroutinefunction(run_method):
raise TypeError(f"{cls.__name__}.run must be async")
class CrawlerHub:
_crawlers: Dict[str, Type[BaseCrawler]] = {}
@classmethod
def _discover_crawlers(cls):
"""Dynamically load crawlers from /crawlers in 3 lines"""
base_path = Path(__file__).parent / "crawlers"
for crawler_dir in base_path.iterdir():
if crawler_dir.is_dir():
try:
module = importlib.import_module(
f"crawl4ai.crawlers.{crawler_dir.name}.crawler"
)
for attr in dir(module):
cls._maybe_register_crawler(
getattr(module, attr), crawler_dir.name
)View on GitHub (pinned to 7e80152142)