Validation-First Design

Validation-First Design

Core Principle: If an Agent Cannot Validate It, It Will Not Be Met

Every spec requirement must include testable acceptance criteria that an agent can automatically verify. This is not optional — it is the foundation that makes SDD work.

Why? AI agents are non-deterministic. Without automated validation, there is no way to know whether an agent's output is correct. Validation gates turn "the agent generated some code" into "the agent generated code that provably meets the specification."

The validation-first rule applies at every level:

• Spec requirements must have testable acceptance criteria
• Plans must define which gates verify each task
• Implementation must pass all applicable gates before being considered complete
• Iterations must show measurable progress through gates

The Validation Gate Sequence

Every implementation must pass through six ordered checkpoints. Each successive gate is more expensive to run, so catching failures early saves significant time.

Gate 1: Compilation Check

What: The project compiles/transpiles without errors.

# Generic pattern — substitute your project's build command
{BUILD_COMMAND}

Why it matters: If the code does not build, nothing else can be validated. This is the cheapest possible check.

What it catches:

• Syntax errors
• Missing imports/dependencies
• Type errors (in typed languages)
• Configuration errors

Acceptance criteria pattern:

- [ ] `{BUILD_COMMAND}` completes with exit code 0