W&B Weave

• Trace and collect metrics about your agents built with popular SDKs and harnesses using Weave OTel-compatible SDK
• Manually instrument your application’s LLM calls and arbitrary functions to trace, version, and collect feedback about your application
• Evaluate your agent’s or application’s responses using LLM judges and custom scorers

​

Get started

​

Install Weave

pip install weave

npm install weave

​

Limits and expected behaviors

• For retryable requests, Weave retries requests starting at 1 second after receiving the first error and then doubles the amount of time between attempts up to 5 minutes. Requests time out after 36 hours.
• Instead of raising exceptions, .call() captures exceptions and stores them in the call.exception. If you need to raise exceptions during execution, set the __should_raise parameter, like this:
  showLineNumbers

  # This raises exceptions
  result, call = foo.call(__should_raise=True)
  
• Dedicated Weave instances use a different OpenTelemetry ingress URL. For more information about authoritative endpoints, see Send OpenTelemetry traces.
• Weave sometimes truncates large trace data objects. This occurs because the default trace output is a raw, custom Python object that Weave can’t serialize automatically. To return all of your trace data, define a dictionary of strings, like this:
  import weave
  
  class MyObj:
      """An object with a large string attribute."""
      def __init__(self, x: int):
          self.x = x
  
      def __repr__(self):
          return f"MyObj(x={self.x})"
  
      def to_dict(self):
          return {"x": self.x}
  
  @weave.op()
  def make_my_obj():
      x = "a" * 10_000
      return MyObj(x)
  
  def main():
      weave.init("<entity/project>")
  
      # Define a traceable operation that processes MyObj
      @weave.op()
      def process_obj(obj: MyObj) -> int:
          return len(obj.x)
  
      # Create and process a large MyObj instance
      large_obj = make_my_obj()
      length = process_obj(large_obj)
      print(f"Length of x in MyObj: {length}")
      print("dict:", large_obj.to_dict())
  
  if __name__ == "__main__":
      main()