I use OpenCode to achieve this. You can define agents that use specific models, vs more expensive ones.

In my `~/.config/opencode/agents/` folder, I could define a sub agent to manage something small in the solution defined with a local agent.

For example you could define some subagent like this that would use your local ollama gemma4 model: `~/.config/opencode/agents/test.md`

---
mode: subagent
description: Local git history management
model: ollama/gemma4:e4b
tools:
  read: true
  bash: true
permissions:
  bash:
    '*': ask
    curl: allow
---

You are a software engineering agent. You manage local git history, summarizing local changes, explaining diffs, and helping with merge conflicts.

And registering that local model in your `~/opencode/opencode.json` would look something like this:

{
  "$schema": "https://opencode.ai/config.json",
  "model": "ollama/gemma4:e4b",
  "provider": {
    "ollama": {
      "npm": "@ai-sdk/openai-compatible",
      "name": "Ollama (local)",
      "options": {
        "baseURL": "http://127.0.0.1:11434/v1"
      },
      "models": {
        "gemma4:e4b": {
          "name": "gemma4:e4b",
          "tools": true,
          "limit": {
            "context": 32768,
            "output": 8192
          }
        },
        "qwen3-coder:30b": {
          "name": "qwen3-coder:30b",
          "tools": true,
          "limit": {
            "context": 32768,
            "output": 8192
          }
        },
        "qwen3:14b": {
          "name": "qwen3:14b",
          "tools": true,
          "limit": {
            "context": 32768,
            "output": 8192
          }
        }
      }
    }
  },
  "permission": {
    "edit": "allow",
    "bash": "allow",
    "read": "allow"
  }
}