OpenCode: a model-routed team, cheap to plan, strong to build

The Stack

Tested Against

Prerequisites

• OpenCode installed
• A provider logged in to actually run it

Steps

1. 1

   Route models per agent and validate

   Pin build to your strong model, plan and a code-reviewer subagent to a cheap one, and deny edit on the reviewer. Invoke the reviewer with @code-reviewer. CI parses opencode.json and asserts each agent names a provider/model and the reviewer is read-only.

   cat > opencode.json <<'JSON'
   {
     "$schema": "https://opencode.ai/config.json",
     "agent": {
       "build": { "mode": "primary", "model": "provider/your-strong-model" },
       "plan":  { "mode": "primary", "model": "provider/your-cheap-model" },
       "code-reviewer": { "description": "Reviews diffs for bugs, security, and performance", "mode": "subagent", "model": "provider/your-cheap-model", "permission": { "edit": "deny" } }
     }
   }
   JSON
   node -e 'const c=JSON.parse(require("fs").readFileSync("opencode.json","utf8"));const a=c.agent;for(const n of ["build","plan","code-reviewer"]){const m=a[n]&&a[n].model;const parts=m?String(m).split("/"):[];if(parts.length!==2||!parts[0]||!parts[1]){console.log("BAD model for "+n);process.exit(1)}}if(a["code-reviewer"].permission.edit!=="deny"){console.log("BAD: reviewer not read-only");process.exit(1)}console.log("config OK: build/plan/code-reviewer each pin a provider/model, code-reviewer edit=deny")'

2. 2

   Invoke the team (the model step, not checked by CI)

   @code-reviewer in a message runs the cheap reviewer; build delegates to it or you Tab between agents. You can bound a quick agent's cost with `steps`. The reviews and builds run models, so CI never claims them.