The Specify, Plan, Tasks, Implement Cycle
The SDD Workflow
Specify, Plan, Tasks, Implement — the four-phase cycle
The SDD workflow follows a deliberate four-phase cycle. Each phase produces a specific artifact, and each artifact is reviewed before moving to the next phase. This structure transforms AI-assisted development from chaotic conversation into a repeatable engineering process.
The Four Phases
Specify
Start with a high-level prompt. The AI generates a complete specification document (requirements.md). You focus on the WHAT and WHY — not the HOW.
Plan
Feed the approved spec to the AI and ask it to create an implementation plan. The plan breaks the spec into architectural decisions, component designs, and a technical roadmap.
Tasks
The AI converts the plan into a concrete task list. Each task is small enough to implement in one session, has clear acceptance criteria, and can be tested independently.
Implement
Execute tasks one by one. For each task: generate code, review, test, commit. Never skip testing or review — this is where quality is ensured.
Phase 1: Specify — in Detail
/specify I need a REST API for managing a book library. Users can browse, search, borrow, and return books. Librarians can add, edit, and remove books. Must track borrowing history and send overdue notifications.
The AI expands this into structured user stories with acceptance criteria, non-functional requirements, and explicit constraints. You review, adjust, and approve before moving on.
Phase 2: Plan
The approved spec becomes input for planning. The AI produces an architecture document covering technology choices, component structure, data models, and API design. This is your chance to catch architectural mistakes before any code is written.
Phase 3: Tasks
The plan gets decomposed into ordered, dependent tasks. Each task has a clear scope, expected output, and definition of done.
Task 1: Set up project scaffold Task 2: Implement Book model and migrations Task 3: Create CRUD endpoints for books Task 4: Add search functionality with filters Task 5: Implement borrowing workflow Task 6: Add overdue notification system Task 7: Write integration tests Task 8: API documentation
Phase 4: Implement
Generate
Ask the AI to implement one task at a time. Provide the task description, relevant spec sections, and context file.
Review
Read the generated code. Does it match the spec? Does it follow your coding standards? Does it handle edge cases?
Test
Run existing tests. Write new tests for the generated code. Verify acceptance criteria are met.
Commit
Commit with a descriptive message referencing the task. This creates a clean audit trail.
The Golden Rule
Never combine multiple tasks in one AI session. Each task gets its own generate-review-test-commit cycle. This keeps changes small, reviewable, and reversible.
The Cycle Repeats
After implementing all tasks, review the results against the original spec. If new requirements emerge, start a new cycle: re-specify, re-plan, create new tasks, implement. SDD is iterative by design.
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