ChatGPT Projects: give each workstream its own instructions and memory
Project instructions override your global custom instructions inside that project, and project-only memory keeps context from leaking across.
ChatGPT tips & tricks
OpenAI API: tune reasoning effort and verbosity separately
reasoning_effort controls how hard the model thinks; verbosity controls how long the answer is. Adjust them instead of rewriting prompts.
Treat production prompts like application code
OpenAI recommends versioning prompts in your repo, using typed variables, reviewing them in PRs and running evals on every change.