The open-source agent harness - the runtime layer that turns an LLM into a working agent

TrueForge

TrueForge runs the agent execution loop for you - model calls, MCP tools, skills, sandboxing, approvals, context management, and session state - and exposes it three ways: a chat UI, an HTTP API with a TypeScript SDK, and an embeddable UI SDK.

Why TrueForge?

Building an agent is easy. Running one well is not - you need streaming, session persistence, tool servers, sandboxing, approvals, and a UI. TrueForge gives you that out of the box:

• Initial setup from catalogs - configure models, MCP servers, skills, and a sandbox once; agents pick from what you connected. Presets come from shipped YAML catalogs you can customize.
• Any model provider - OpenAI, Anthropic, Google Gemini, and other catalog providers, or any OpenAI-compatible endpoint.
• MCP tools - remote MCP servers with header auth or OAuth, including in-chat authorization.
• Skills - git-backed SKILL.md instruction packs, loaded on demand in the sandbox.
• Sandbox as a tool - isolated code/file execution (Daytona today; more providers planned), provisioned only when needed. Secrets stay in the harness.
• Human checkpoints - tool approval, ask-user-questions, and Generative UI in chat.
• Context engineering - subagents, deferred tool loading, Code Mode, large-result offloading, and compaction.
• Chat UI + SDK - use the bundled UI, automate with @truefoundry/trueforge-sdk, or embed @truefoundry/trueforge-ui.

It scales down and up: local mode (one process, SQLite) or hosted mode (Postgres + Redis, Docker Compose or Helm).

Getting started

Run TrueForge (local, Docker Compose, or Kubernetes), connect a model and tools, and build your first reusable agent in the Quickstart.

To work on TrueForge from this repository, see CONTRIBUTING.md.

Architecture

flowchart LR
  ui[Chat UI<br/>@truefoundry/trueforge-ui]
  code[Your code<br/>trueforge-sdk]
  subgraph server [TrueForge server]
    api[HTTP API]
    loop[Agent loop]
    api --> loop
  end
  db[(SQLite / Postgres)]
  subgraph byo [Bring your own]
    llm[Model providers]
    mcp[MCP servers]
    sandbox[Sandbox provider]
  end

  ui --> api
  code --> api
  loop --> db
  loop --> llm
  loop --> mcp
  loop --> sandbox

Loading

Mode	Best for	Storage	Extra infra	How to run
Local	Personal use, trying it out	SQLite	None	npx @truefoundry/trueforge
Hosted	Teams, multi-replica	Postgres	Postgres + Redis	Docker Compose or Helm

Documentation

Section	What you'll find
Introduction	What an agent harness is and how TrueForge fits together
Quickstart	Run local or hosted, build your first agent
Initial Setup	Models, MCP, skills, sandbox - catalogs and overrides
Create an Agent	Select resources; tool approval, questions, Generative UI
Harness Capabilities	Sandbox-as-tool, subagents, deferred tools, Code Mode, compaction
Setup Login	Optional OIDC for shared deployments
Benchmarking	Cost/accuracy vs Claude Managed Agents and deepagents
SDK	TypeScript client: sessions, turns, events
Chat UI	Bundled UI and embedding @truefoundry/trueforge-ui
API Reference	OpenAPI paths and schemas

Benchmarks

We compare TrueForge against Claude Managed Agents and deepagents on the same tasks, tools, and model - same accuracy, lower cost. Reproduce it from benchmark/. Write-up: Benchmarking.

Contributing

We love contributions - bug reports, features, and docs fixes. See CONTRIBUTING.md and our Code of Conduct.

To report a security vulnerability, follow SECURITY.md instead of opening a public issue.

License

TrueForge is released under the MIT License.