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README
<a href="https://kiln.tech">









        <img width="205" alt="Kiln AI Logo" src="https://github.com/user-attachments/assets/4ca9b69f-1c90-43a4-8d2e-13de4eb2ee9c">



</a>

A free app and open-source library to build better AI products.

Kiln AI Animated Preview

Download Kiln Read the Docs

HighlightsEvalsAuto-OptimizeRAGAgentsFine-TuningSynthetic DataAll Docs

Build and Test PyPI Discord

What is Kiln?

Kiln is a workbench for the full AI development loop: evals, optimization, prompts, RAG, fine-tuning, synthetic data, agents, and tools - all working together. The desktop app lets your whole team contribute (PMs, subject-experts, and QA can rate outputs and add data without writing code). The MIT-licensed Python library ships the same tasks to production. Runs locally - bring your own API keys, or go fully offline with Ollama.

Highlights

Iterate, optimize, and collaborate

  • 🖥️ Intuitive app - Easy-to-use apps for Mac, Windows, and Linux. One-click install.
  • 📊 Eval Builder - Auto-generate evals (judge + synthetic eval dataset), and align to your preference in ~10 minutes.
  • 🚀 Auto-Optimize - Automatically find the best way to run your AI task, optimizing prompt, model selection, tools, skills, subagents, parameters, and more.
  • 💬 AI Assistant - Your AI data-science partner. Kiln Assistant proposes improvements, optimizes prompts, runs experiments, creates evals, and more.
  • 🤝 Git-native collaboration - The app syncs to Git automatically — even for teammates who don't know what Git is.

Build & ship agents

  • 🔍 RAG - Drag-and-drop docs (PDF, image, video, audio) to create a RAG. Auto-generated RAG evals from your own documents.
  • 🤖 Subagents - Compose multi-agent hierarchies. Each runs in its own focused context window.
  • 🪄 Synthetic Data Generation - Generate data for evals or fine-tuning in minutes.
  • 🎛️ Fine-Tuning - Zero-code fine-tuning across 60+ models (Qwen, Llama, GPT, Gemini, …) on Fireworks, Together, and Vertex. Serverless deployment included.
  • 🐍 Open Python library - Agents built in the app can be deployed to production. MIT open-source.
  • 🧰 …and more - Tools & MCP, Skills, structured outputs, reasoning models, model library (190+ tested).

App Quickstart

Get started in minutes - one-click install.

Download Kiln Desktop for macOS, Windows, or Linux, then follow the 5-minute quickstart to run your first task.

MacOS Windows Linux

Prefer to start in code? See the Python library quickstart.

Demo

Watch a 2-minute overview, or our end-to-end project demo (20 minutes).

Why Kiln?

Most AI tooling forces a tradeoff: a code-only framework that covers one slice (orchestration or evals or RAG), or a paid SaaS that locks in your data and can't be extended. Kiln is a free, local-first workbench where a single task and dataset flow through evals, prompt optimization, fine-tuning, RAG, agents, and synthetic data — all in one tool.

  • One dataset, every technique. Define a task once. Eval it, optimize the prompt, fine-tune a model, generate synthetic data, add RAG — all against the same dataset, with results that compound across stages.

  • Track every axis. Move fast. Don't regress. Keeping agents running well is hard — a prompt change quietly regresses behavior three steps downstream; a model upgrade improves five things and breaks two. Kiln tracks quality across every dimension you care about, so you iterate without breaking what already works.

    Kiln optimization across iterations

  • Optimization, not just evaluation. Other tools tell you how a prompt scores, but not how to fix it. Kiln's Auto-Optimize searches across hundreds of prompt mutations and models to find what works best for every eval dimension.

  • GUI for the whole team, library for engineers. Kiln's desktop app lets PMs rate outputs, SMEs add training examples, and QA flag regressions — without a terminal. Engineers ship the same tasks via an MIT-licensed Python library. Data scientists can use the library in notebooks and experiments.

  • Local-first. Most AI platforms are SaaS-only. Kiln runs entirely on your machine. Bring your own API keys, or go fully offline with Ollama. Your data never leaves your control. Team-sync is provided via Git infrastructure you already own.

  • 190+ models tested across every provider. Skip the guesswork — we've tested every model's capabilities across all major providers. OpenAI, Anthropic, Gemini, Bedrock, Ollama, OpenRouter, Fireworks, Groq, any OpenAI-compatible endpoint, and more. Swap models with confidence.

Open-source Python Library

Build AI tasks in the app. Deploy with the open-source library. Same engine, same project files, no rewrite. The MIT-licensed kiln-ai library is the same library used in the app. Load Kiln projects, run tasks, build fine-tunes, work in notebooks, integrate Pandas/Polars dataframes, and more.

pip install kiln-ai

📚 Library docs · REST API · PyPI

Docs

Full docs at docs.kiln.tech. Common starting points:

Community

  • Chat with the community on Discord.
  • Subscribe to the newsletter for new features.
  • File issues, request features, or open a discussion on GitHub.

Contributing

See CONTRIBUTING.md for development setup and contribution guidelines.

License & Trademarks

Kiln's core Python library and REST server are MIT-licensed. The desktop app is source-available, free to use, and built on the fair-code model — so Kiln stays free for individuals while remaining sustainable.

Datasets are open JSON. You own and control your datasets.

Kiln Pro is our service that adds the AI Assistant, Auto-Optimize, and the Eval Builder. It's opt-in, and the core Kiln app remains fully functional without it.

The Kiln name and logos are trademarks of Chesterfield Laboratories Inc.

Copyright 2024 — Chesterfield Laboratories Inc.

Extension points exported contracts — how you extend this code

StreamEvent (Interface)
SSE event from backend (AI SDK stream event shape)
app/web_ui/src/lib/chat/streaming_chat.ts
paths (Interface)
(no doc)
app/web_ui/api_schema.d.ts
components (Interface)
(no doc)
app/web_ui/api_schema.d.ts
operations (Interface)
(no doc)
app/web_ui/api_schema.d.ts
Locals (Interface)
(no doc)
app/web_ui/src/app.d.ts

Core symbols most depended-on inside this repo

patch
called by 1894
app/web_ui/src/lib/git_sync/api.ts
get
called by 1136
libs/core/kiln_ai/utils/filesystem_cache.py
save_to_file
called by 1041
libs/core/kiln_ai/datamodel/basemodel.py
set
called by 274
libs/core/kiln_ai/utils/filesystem_cache.py
load_from_file
called by 196
libs/core/kiln_ai/datamodel/basemodel.py
model_dump
called by 161
libs/core/kiln_ai/adapters/model_adapters/stream_events.py
next
called by 124
app/web_ui/src/lib/utils/limiter.ts
shared
called by 121
libs/core/kiln_ai/utils/config.py

Shape

Function 4,696
Method 3,980
Class 1,253
Route 491
Interface 42
Enum 1

Languages

Python95%
TypeScript5%

Modules by API surface

app/desktop/studio_server/test_provider_api.py189 symbols
libs/server/kiln_server/test_document_api.py174 symbols
libs/core/kiln_ai/adapters/rag/test_rag_runners.py155 symbols
libs/core/kiln_ai/adapters/model_adapters/test_litellm_adapter.py139 symbols
libs/core/kiln_ai/cli/commands/test_package_project.py137 symbols
libs/server/kiln_server/document_api.py131 symbols
libs/core/kiln_ai/tools/test_mcp_session_manager.py119 symbols
libs/core/kiln_ai/adapters/test_provider_tools.py113 symbols
app/desktop/studio_server/test_tool_api.py113 symbols
libs/core/kiln_ai/adapters/model_adapters/test_base_adapter.py103 symbols
libs/core/kiln_ai/datamodel/test_basemodel.py84 symbols
app/desktop/studio_server/test_eval_api.py84 symbols

Dependencies from manifests, versioned

@floating-ui/dom1.7.2 · 1×
@kinde-oss/kinde-auth-pkce-js4.3.0 · 1×
@playwright/test1.60.0 · 1×
@redocly/cli2.11.1 · 1×
@sentry/sveltekit10.50.0 · 1×
@sveltejs/adapter-static3.0.2 · 1×
@sveltejs/kit2.20.6 · 1×
@sveltejs/vite-plugin-svelte3.1.1 · 1×
@tailwindcss/typography0.5.13 · 1×
@types/dompurify3.0.5 · 1×

For agents

$ claude mcp add Kiln \
  -- python -m otcore.mcp_server <graph>

⬇ download graph artifact