The engine is open.
Build on it.
Felix CLI is fully open source — the agent engine, backpressure system, plugin architecture, and spec-driven workflow. Free to use, fork, and extend.
What's included
Everything you need to run autonomous agents on your codebase.
Felix CLI
Cross-platform command-line tool. Run agents, manage specs, validate output — all from your terminal.
Agent Engine
The PowerShell execution core — plan-driven phases, mode enforcement, iteration management, and state persistence.
Backpressure System
Test-gated progress. No code lands unless tests pass, builds succeed, and lint is clean. Non-negotiable quality gates.
Plugin Architecture
Extensible plugin system for sync, metrics, prompt enhancement, and custom integrations. Build your own or use built-in ones.
Spec-Driven Workflow
Markdown specs define requirements, acceptance criteria, and validation commands. Human-readable, git-trackable, auditable.
Artifact System
Durable file-based state — specs, plans, run logs, and status all persist as files, not chat history. Full audit trail.
How it works
Three steps. No Felix Cloud account required for local specs.
Install
Download the CLI binary or build from source. Works on Windows, macOS, and Linux.
Setup
Configure Felix 3 in your project. Creates a separate .felix3 config for your selected harness.
Run
Run a named spec or let Felix pick a ready spec. Felix coordinates plan, build, validation, and review.
Open Source vs Felix Cloud
The CLI is fully functional standalone. Felix Cloud adds team visibility and orchestration for teams that need it.
| Feature | Open Source CLI | Felix Cloud |
|---|---|---|
| Agent execution | check | check |
| Backpressure validation | check | check |
| Spec-driven workflow | check | check |
| Plugin system | check | check |
| Local file-based state | check | check |
| Offline execution | check | check |
| Team dashboard | — | check |
| Run visualization | — | check |
| Multi-machine orchestration | — | check |
| Spec sync (push/pull) | — | check |
| Desktop tray manager | — | check |
| Team agent coordination | — | check |
Built for contributors
Felix's plugin architecture means you can extend the agent engine without touching core code. Build custom sync targets, add metrics collectors, or create entirely new command workflows.
Plugins
Drop a PowerShell module into .felix/plugins/ and it's automatically loaded. No registration, no ceremony.
Commands
Add custom CLI commands by creating scripts in .felix/commands/. First-class support for your workflow.
Issues & PRs
Report bugs, request features, or submit pull requests on GitHub. Every contribution makes the engine better.
MIT Licensed
Use it commercially, modify it, distribute it. No restrictions beyond the standard MIT terms. Your code stays yours.
Start shipping with Felix.
Run it locally, extend it freely, or connect to Felix Cloud for team features.