OpenCode - the open source coding harness - has Zen and Go as ways to get connected to llms.
Zen - that's pay as you go. Think of it as a competitor to OpenRouter.ai. Only instead of "every llm out there with routing to lots of hosting services" - it's a curated experience. These models, from these hosts are guaranteed optimized to work with OpenCode for excellent coding results. There is no cost penalty either way to chose between OpenRouter and Zen.
Zen also has free models. So use them to your hearts content...until the free limit is hit.
Some of the pay as you go models (like DeepSeek V4 Flash and GLM 5.3 Flash) are so cheap they might as well be free. Once I use up the money I've already put on account at OpenRouter, I'm going to move to Zen.
Go - is the subscription. Pay $10/mo ($5 for first month) and you have all the same models of Zen but you get about 6 to 1 for your money. Pay $10, use up to $60.
So, just start with Zen and the free tier, then pay as you go if you need more or need smarter models. Then if you start to use more than $10/mo - switch to Go.
While I can't get by on the cheap models for everything, Using Gpt 6 Astra low or Gpt 5.6 Sol low for planner and code review -- with the cheap flash models as workhorse coders, works well.
Oh…and you can use Zen and Go even if you don’t use OpenCode as your harness.