I’ve been using a similar workflow, but I’d frame it less as ChatGPT instead of Codex and more as a separation of responsibilities.
For me, ChatGPT Pro Extended is strongest as the planning, architecture, and review layer. It is where I work through intent, scope, sequencing, risk, acceptance criteria, and whether the plan actually makes product sense. Then Codex is strongest as the execution layer: apply the plan, modify the repo, run checks, produce diffs, and surface evidence.
Codex Plan Mode is useful too, especially for execution-adjacent planning. For example, I recently used it to help turn an architecture document into epics, stories, and tasks. That worked well because the task was bounded and close to implementation. But I still would not treat Codex Plan Mode as automatically better than ChatGPT Pro for higher-level planning.
The biggest lesson for me is that Codex can implement a plan incorrectly or satisfy the surface wording while missing the real intent. A separate ChatGPT/human review pass has caught issues for me that I would not want merged blindly.
So, the winning workflow has been:
ChatGPT Pro / Extended for product and architecture planning.
Codex Plan Mode when tactical decomposition is useful.
Codex for implementation.
ChatGPT/human review before accepting the output.
In other words, I don’t see it as ChatGPT vs Codex. I see it as architect/reviewer plus implementer. The leverage comes from not asking one tool to play every role.