I have been using Opencode to work on a couple of ESP32 projects that are of a more “Maker” nature. At some point I realised that I also needed a case and decided to set Opencode loose on it too.

The workflow for this is simple, but awful:

• describe the case in words
• Opencode (using Big Pickle because FREE) creates an OpenSCAD model
• Render the OpenSCAD model
• Wonder what the hell Opencode was thinking
• GOTO 10 and the cycle continues ad nauseam

What you need is some way for Opencode to verify what it has done and iterate.

I use Opencode with oh-my-openagent which, amongst other things, gives you sub-agents. One of those sub-agents is the “multimodal-looker” which can look at images and provide feedback. I thought I could use this to create a feedback loop for Opencode to verify its own work.

The idea is simple:

• I describe the case in words
• Opencode creates an OpenSCAD model and renders it
• The multimodal-looker “looks” at the rendered image and provides feedback.
• Opencode uses the feedback to iterate on the design

This is great in theory, but falls apart in practice because Big Pickle does not support visual analysis. So, I needed to do two things:

• route visual analysis to another model
• decide which model to use

I decided to use gemma4:e4b because it has the feature I need and is not only free, but I can run it on my own hardware with reasonable performance. The performance isn’t interactive-speed, but it is good enough that I can set the agent working while I go away and have a meal or chat with my wife for a bit.