🚀 What is Promptolution?

Promptolution is a unified, modular framework for prompt optimization built for researchers and advanced practitioners who want full control over their experimental setup. Unlike end-to-end application frameworks with high abstraction, promptolution focuses exclusively on the optimization stage, providing a clean, transparent, and extensible API. It allows for simple prompt optimization for one task up to large-scale reproducible benchmark experiments.

Key Features

• Implementation of many current prompt optimizers out of the box.
• Unified LLM backend supporting API-based models, Local LLMs, and vLLM clusters.
• Built-in response caching to save costs and parallelized inference for speed.
• Detailed logging and token usage tracking for granular post-hoc analysis.

Have a look at our Release Notes for the latest updates to promptolution.

📚 Scientific Publications Powered by Promptolution

• CANTANTE: Optimizing Agentic Systems via Contrastive Credit Attribution — Zehle, 2026. arXiv
• MO-CAPO: Multi-Objective Cost-Aware Prompt Optimization — Büssing et al., 2026. arXiv
• promptolution: A Unified, Modular Framework for Prompt Optimization — Zehle et al., 2026. EACL 2026
• Can Calibration of Positional Encodings Enhance Long Context Utilization? — Zehle & Aßenmacher, 2026. EACL 2026
• Disambiguation-Centric Finetuning Makes Enterprise Tool-Calling LLMs More Realistic and Less Risky — Hathidara et al., 2025. arXiv
• CAPO: Cost-Aware Prompt Optimization — Zehle et al., 2025. AutoML 2025

🔧 Installation and Quickstart

pip install promptolution[api]

For local inference, add [transformers] (HuggingFace) or [vllm] (vLLM serving), or both.

import pandas as pd
from promptolution.utils import ExperimentConfig
from promptolution.helpers import run_experiment

# DataFrame with columns "x" (input) and "y" (label)
df = pd.read_csv("your_data.csv")

config = ExperimentConfig(
    optimizer="capo",
    task_description="Classify each sentence as subjective or objective.",
    prompts=["Classify the text as objective or subjective."],
    n_steps=10,
    api_url="https://api.openai.com/v1",
    model_id="gpt-4o-mini",
    api_key="YOUR_API_KEY",
)

best_prompts = run_experiment(df, config)
print(best_prompts)

Full tutorial: Getting Started notebook · Docs

🧠 Featured Optimizers

Name	Paper	Init prompts	Exploration	Costs	Parallelizable	Few-shot
CAPO	Zehle et al., 2025	required	👍	💲	✅	✅
EvoPromptDE	Guo et al., 2023	required	👍	💲💲	✅	❌
EvoPromptGA	Guo et al., 2023	required	👍	💲💲	✅	❌
OPRO	Yang et al., 2023	optional	👎	💲💲	❌	❌

🏗 Components

• Task – Manages the dataset, evaluation metrics, and subsampling.
• Predictor – Defines how to extract the answer from the model's response.
• LLM – A unified interface handling inference, token counting, and concurrency.
• Optimizer – The core component that implements the algorithms that refine prompts.
• ExperimentConfig – A configuration abstraction to streamline and parametrize large-scale scientific experiments.

🤝 Contributing

Contributions are welcome! See CONTRIBUTING.md for the workflow, code quality guidelines, and how to run tests.

📄 Citation

If you use Promptolution in your research, please cite:

@inproceedings{zehle2026promptolution,
  title={promptolution: A unified, modular framework for prompt optimization},
  author={Zehle, Tom and Hei{\ss}, Timo and Schlager, Moritz and A{\ss}enmacher, Matthias and Feurer, Matthias},
  booktitle={Proceedings of the 19th Conference of the European Chapter of the Association for Computational Linguistics (Volume 3: System Demonstrations)},
  pages={282--296},
  year={2026}
}

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Developed by Timo Heiß, Moritz Schlager, Tom Zehle, and Henri Oberpaur (LMU Munich, MCML, ELLIS, TUM, Uni Freiburg).