How I Split Work Between Claude Code and Codex in Real Projects

I usually have two terminals open: Claude Code on the left, Codex on the right. Not for benchmarking. Just for work. I'm a Java backend developer working on a supply chain system with 20+ Spring Boot microservices, a lot of business logic, and the usual amount of legacy debt. After using both tools side by side for a few weeks, I stopped thinking of them as competitors. They do different jobs. My Split The short version: Claude Code handles understanding. Codex handles execution. When I'm debugging something messy or reviewing code that touches real business logic, I usually start with Claude Code. It's better at following context through multiple layers and explaining why something is happening. When the task is more mechanical, parallelizable, or just high-volume, I hand it to Codex. Tests, docs, repetitive edits, cleanup work — that's where it fits well. The exact model breakdown I use: Scenario Tool Model Everyday coding, new features Claude Code Sonnet 4.6 Complex bugs, hard probl