This is a Smash Stories submission for the DEV Summer Bug Smash: a debugging story about the gap between "all tests pass" and "it actually works" — and the unlikely hero that closed it.
The setup
The project is a small MCP (Model Context Protocol) server that wraps Google's gemini-3.1-flash-lite-image model. It exposes image generation and stateful image editing as four tools that any MCP-speaking agent can call — Claude Code, a Google ADK agent, and a Rust CLI all consume the same ~300-line Python server. (Full architecture write-up here.)
By every signal a developer normally trusts, it was healthy:
Then I wrote a demo script. It found a production bug in under a minute of runtime.
