OpenCode harness is so good I'm surprised one of the big players hasn't bought them outright. Essentially their harness:

* Removes all the system prompt cruft and bullshit that CC pumps into the prompt and pollutes context and shit like "adaptive thinking"

* Is extremely good at keeping the model aligned with AGENTS.MD and opencode.json and using all the features available there (parallel agents, sub-sub agents, etc)

For example, I'm working on a repo with 5 distinct components and I have a specialized agent for each component. CLAUDE.MD is just a markdown file where I say "Hey Claude always use X agent for X component. X agent has this prompt blah blah" and then pray Claude remembers to use it. opencode.json is a structured file used by the harness and it has ALWAYS coerced the model to use it, including being able for the agents to delegate subagents in parallel etc.

This makes a massive difference. So if I have a feature that touches multiple components, OpenCode rips through it with the specialized subagents while Claude sits their spinning its wheels and occasionally remembering theres a specialized agent and then maybe once in a blue moon it will do it in parallel.

With CC I feel like I need to do all these invocations and coercions. OpenCode, once you've got your opencode.json and agents defined, just works.