The new Plan mode doesn't give the LLM access to tools like editing files or running bash commands.
You can also quickly switch between build and plan.
Or define your own mode in the opencode config.
opencode v0.2.23 has modes - ships with a "build" and "plan" mode
but here's the fun part you can add your own
specify what model, prompt and what tools should be enabled and quick switch by hitting tab