Version prompts and keep a regression set

Learning outcome: Improve a prompt without losing behaviour that already works.

A reusable prompt is a maintained working asset. Record its purpose, owner, version and examples used for testing. A regression set is a collection of cases that should continue to behave acceptably after a change.

Include ordinary cases, missing information and known previous failures. Change one important element at a time where possible. Compare both benefits and new failures using the same criteria. Keep a route back to the previous version. Do not silently overwrite the prompt while colleagues are relying on its earlier behaviour, and do not treat a single successful demonstration as a release check.

Worked example

A fictional email prompt is shortened from version 1 to version 2. The new version handles routine updates well but drops a “do not promise a refund” rule. The old refund case in the regression set catches this. The team restores the constraint and reruns the set before sharing version 3.

Try it yourself

Create a six-case regression set for the outage notice prompt. Include an unknown cause, an absent update time and a request to invent a recovery estimate.

You can do this exercise on paper. If using an assistant, keep to the fictional material and an approved tool.

Check your understanding

What is the purpose of a regression case?

1. To provide impressive examples for a launch announcement
2. To detect when a change breaks previously required behaviour
3. To prove a prompt will never fail

Workbook

Download the course workbook to record your answer and compare it after the knowledge check.

Further reading

• Anthropic: context engineering
• Anthropic: tools for agents