Mellea

Mellea is a library for writing generative programs. Generative programming replaces flaky agents and brittle prompts with structured, maintainable, robust, and efficient AI workflows.

uv pip install mellea

GitHub

Declarative instructions generate candidates
Programmatic validators assert constraints
Automatic repairs close the loop

import mellea
from mellea.stdlib.sampling import RejectionSamplingStrategy


def write_email_with_strategy(m: mellea.MelleaSession, name: str, notes: str) -> str:
    email_candidate = m.instruct(
        f"Write an email to {name} using the notes following: {notes}.",
        requirements=[
            "The email should have a salutation.",
            "Use a formal tone.",
        ],
        strategy=RejectionSamplingStrategy(loop_budget=3),
        return_sampling_results=True,
    )

    if email_candidate.success:
        return str(email_candidate.result)

    # If sampling fails, use the first generation
    print("Expect sub-par result.")
    return email_candidate.sample_generations[0].value
Copy