Steps 5-6: The Build

What your agent does

Builds the entire application phase by phase, following the implementation plan exactly. Each phase is built on a feature branch, tested, and committed before moving to the next.

Why this matters

The agent never tries to build everything at once. This is the #1 mistake in AI-assisted development — giving the AI your whole spec and saying "build it." The result is always a mess: hallucinated APIs, inconsistent patterns, missing features, and a debugging nightmare.

Phase-by-phase building means:

• Each phase is small enough to fit in context

• Tests run after every phase

• If something breaks, you know exactly which phase caused it

• The agent can be interrupted and resumed without losing progress

What happens during the build

Phase 1: Foundation

The agent:

1. Scaffolds the project (framework, config, dependencies)

2. Sets up the database schema

3. Implements authentication (if applicable)

4. Builds core API routes

5. Creates the main UI pages

6. Creates environment variable template

7. Initialises the database

8. Verifies the build passes

9. Commits

Remaining phases

For each subsequent phase, the agent:

1. Checks its context usage — if high, it spawns a sub-agent

2. Creates a feature branch

3. Builds the features specified in the implementation plan

4. Runs npm run build to verify

5. Tests key endpoints

6. Commits

Parallel phases

If the implementation plan marks phases as parallelisable (no dependencies between them), the agent can build them simultaneously using sub-agents. Each sub-agent gets:

• The implementation plan

• Its specific phase

• The current codebase

What you see

Your agent will report progress as it goes:

• "Phase 1 complete — auth + monitor CRUD. Build passes."

• "Phase 2 complete — scheduler + pinging. 2 endpoints tested."

• "Phase 3 complete — charts + uptime stats."

Your role

Watch. The agent handles everything. If you want to intervene:

• "Use a different component library"

• "That API shape doesn't match what I need"

• "Skip email notifications for now"

Next: Testing everything →