Contract-First Collaboration

Coordinate frontend/backend or service-to-service work through one authoritative, machine-checkable contract. Consumers state what they need, providers implement that shape, and both sides verify against the same artifact before integration.

This skill governs how teams change a boundary. It complements api-design, which governs what a good API looks like, and ai-regression-testing, which guards fixed bugs from returning.

When to Activate

• Frontend and backend work will proceed in parallel.
• Two or more services exchange API payloads, events, or commands.
• Field names, nullability, enums, or error shapes regularly drift.
• One consumer needs several calls because the provider exposed storage models instead of a task-oriented response.
• A provider change can break consumers maintained by another person or agent.
• Mock responses and production responses no longer have the same shape.