Kiln

Kiln, made by Chesterfield Laboratories Inc, is a workbench for the full AI development loop. It combines evals, prompt optimization, RAG, fine-tuning, synthetic data, agents, and tools in one desktop app for macOS, Windows, and Linux, paired with an MIT-licensed Python library for running the same tasks in production. The latest listed release is Kiln Desktop v1.2.0.

What It Is

Kiln is a local-first AI development workbench. A team defines a task and a dataset once, then runs evals, prompt optimization, fine-tuning, RAG, agents, and synthetic data generation against that same dataset. The app runs on your machine; you bring your own API keys or go fully offline with Ollama. Team sync works through Git, and datasets are stored as open JSON.

Workflow and Capabilities

• Evals: an eval builder auto-generates a judge and a synthetic eval dataset, which can be aligned to your preferences. Golden datasets and human ratings are supported.
• Auto-Optimize: searches across prompt, model, tools, skills, subagents, and parameters to tune a task against its evals.
• RAG: documents (PDF, image, video, audio) can be dragged in to create a RAG, with evals generated from your own documents.
• Agents and tools: multi-agent hierarchies with subagents, plus Tools and MCP, Skills, structured output, and reasoning models.
• Fine-tuning: zero-code fine-tuning across 60+ models on Fireworks, Together, and Vertex, with serverless deployment.
• AI Assistant: proposes improvements, runs experiments, and creates evals through conversation.

Team and Developer Model

Product managers, QA, and subject experts can rate outputs, leave feedback, and add data in the app without coding. Engineers and data scientists use the kiln-ai Python library to load Kiln projects, run tasks, build fine-tunes, and work in notebooks, with a REST API also available. Kiln says it has tested 190+ models across major providers.

Licensing and Optional Service

The core Python library and REST server are MIT-licensed. The desktop app is source-available and free to use under a fair-code model. The AI Assistant, Auto-Optimize, and Eval Builder are provided through the opt-in Kiln Pro service; the core app remains functional without it.