
The Prompting Playbook: Debug a Production Prompt
Your production prompt worked, then you moved to a new model and the test cases started failing. This is the repair method, in order. Build a small eval suite of control, edge and capability-boundary cases, so you can tell a real improvement from a feeling. Strip the pasted-website cruft and the untrue persona. Carve the prompt into tagged sections so role, policy, guidelines and tone stop competing. Add an output contract and enforce it in the harness with a stop sequence. Then isolate one failing case at a time and find the instruction that made the wrong answer the compliant one. Worked end to end on a messy customer-support prompt for a fictional telco, then run on a prompt of your own. Based on “The Prompting Playbook” by Margot van Laar, Code with Claude.

