one-day-build

name	one-day-build
description	Production-ready project foundation in 5-8 hours. Architecture-driven human-AI pair programming workflow for bootstrapping greenfield projects with clean architecture, comprehensive tests, and documentation. Use when (1) starting new projects from scratch, (2) user says "let's build X from scratch", "help me architect", "pair program with me", (3) need structured foundations. NOT for quick fixes, single-file changes, or existing codebase modifications. Use when this capability is needed.
metadata	{"author":"blizhan"}

One Day Build

Production-ready project foundation in a single session (5-8 hours).

Philosophy: Architecture first → Document decisions → Refactor ruthlessly → Test what differs

Quick Reference

Phase	Duration	Focus	Exit Criteria
1. Intent	30 min	What & Why	3-5 user stories documented
2. Architecture	60-90 min	How	AGENTS.md with decisions
3. Foundation	2-3 hrs	Build	1 feature working, >80% coverage
4. Refinement	1-2 hrs	Fix	Bugs fixed, code cleaned
5. Testing	60 min	Verify	Test factories, fast suite
6. Docs	30 min	Record	README + AGENTS.md current

Phase Workflow

1. Intent Clarification

Ask clarifying questions until requirements are concrete:

• Vision, constraints, tech preferences?
• Must-have vs nice-to-have?
• Sample data available?

User: "I want to build a stock price tracker"
→ "Which APIs? Real-time or daily? CLI, web, or both? Alerts needed?"
→ Result: Yahoo Finance API, daily updates, CLI + web dashboard, email alerts

Checklist: [ ] 3-5 user stories [ ] Constraints doc [ ] Priority list

2. Architecture Design

Propose 2-3 approaches with trade-offs. Document in AGENTS.md.

Key decisions:

• Patterns: Template Method (workflows), Strategy (algorithms), Factory (creation)
• Extensibility: How to add new data sources/formats?
• Config: What's configurable vs hardcoded?

Checklist: [ ] AGENTS.md created [ ] Interfaces defined [ ] Config schema

3. Foundation Implementation

1. Setup (15 min) - structure, deps, git
2. Core (45 min) - base classes, error handling
3. First feature (60 min) - complete with real data
4. Tests (30 min) - fixtures, >80% coverage

Checklist: [ ] 1 feature works [ ] Tests pass [ ] Makefile ready

4. Problem-Driven Refinement

Cycle: Discover → Analyze → Design → Implement → Validate

Only refactor when problems emerge. Don't pre-optimize.

Bug: Year 1948 showing as 2025
→ Root cause: No year validation
→ Fix: Add _is_valid_year() + test

Checklist: [ ] Bug fixed [ ] Regression test added [ ] Docs updated

5. Testing Architecture

Goal: Make testing easier than not testing.

# Factory pattern - one line = full test suite
TestStockFetcher = create_fetcher_tests(StockFetcher, sample_data, expected)

Checklist: [ ] Test utilities exist [ ] <5s run time [ ] >80% coverage

6. Documentation Sync

Maintain: AGENTS.md (decisions), TODO.md (backlog), README.md (usage)

Principle: If not documented, it doesn't exist.

Checklist: [ ] Examples work [ ] Decisions recorded [ ] Next steps clear

Roles

Agent	Human
Propose options with trade-offs	Choose direction
Implement and test	Provide domain knowledge
Document decisions	Validate against real use
Challenge assumptions	Accept/reject trade-offs

Variations

Scenario	Use Phases
Greenfield	1-6 (full)
Legacy refactor	3-5
Feature addition	2-5
Bug hunt	4-5

Anti-Patterns

Problem	Fix
Analysis paralysis	Time-box design to 90 min
Premature optimization	Solve today's problems only
Doc debt	Document decisions immediately
Scope creep	Add to TODO.md, stay focused

For detailed role breakdowns and examples, see references/phases.md.

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