inv = LLMInvocation(provider="openai", request_model="gpt-4o")
# inv is in invalid state now
handler.start_llm(inv)
try:
    inv.output_messages = [...]
    # need to carry both - handler and inv to here
    handler.stop_llm(inv)
except Exception as exc:
   # why not just pass exc ?
    handler.fail_llm(inv, Error(type=type(exc), message=str(exc)))

inv = handler.start_inference("openai", "gpt-4o")
# valid state right away
try:
    inv.output_messages = [...]
    # no need to pass handler here if happens in a different method
    inv.stop()
except Exception as exc:
    # much shorter
    inv.fail(exc); 
    raise

with handler.inference("openai", "gpt-4o") as inv:
    inv.output_messages = [...]