OpenCode is an open source agent that helps you write and run code with any AI model, including free (for now although the free tier uses a limited subset of backend models including Big Pickle) use of its own OpenCode Zen model. It’s available as a terminal-based interface, desktop app, or IDE extension.
So OpenCode is similar to Claude Code in that it has agentic abilities, MCP servers, etc. Their Zen model is interesting. You connect to it (so no download or local GPU really required) and it is a curated set of AI models tested and benchmarked for coding agents created by the team behind OpenCode.
OpenCode passes whatever costs are involved in using Zen, straight through without any markup. However, to cover costs, OpenCode adds only a small payment processing fee of $1.23 per $20 balance top-up. The models being used are optimised for coding ability.
What Zen’s real offering is, you are paying this one entity, to pool funds, and get access to various backend models, which would normally be separate subscriptions on their own. You could also connect your own front end AI to the Zen service as well.
With over 195,000 GitHub stars, 950 contributors, and over 13,000 commits, OpenCode is used and trusted by over 16 million developers every month. So this is no small project. That said, it is really for coding and technical troubleshooting, and not really for use as a chat service.
See https://www.xda-developers.com/switched-to-claude-code-open-source-rival-and-stopped-worrying-about-rate-limits or https://opencode.ai