Demo: Requirements-Driven Development¶

You're building a feature from scratch. Instead of jumping into code, you define requirements first — then the AI implements with full context of what needs to be built and why.

Scenario Setup¶

You're adding a notification system to your SaaS app.

cd my-saas-app
fcontext init
fcontext enable copilot

Step 1 — Define the Requirement Hierarchy¶

# High-level epic
fcontext req add "Notification System" -t epic

# Break into stories
fcontext req add "Email notifications for account events" -t story --parent EPIC-001
fcontext req add "In-app notification center" -t story --parent EPIC-001
fcontext req add "Notification preferences page" -t story --parent EPIC-001

# Break a story into tasks
fcontext req add "SendGrid integration" -t task --parent STORY-001
fcontext req add "Welcome email template" -t task --parent STORY-001
fcontext req add "Password reset email" -t task --parent STORY-001

View the hierarchy:

fcontext req tree

EPIC-001  Notification System
├── STORY-001  Email notifications for account events
│   ├── TASK-001  SendGrid integration
│   ├── TASK-002  Welcome email template
│   └── TASK-003  Password reset email
├── STORY-002  In-app notification center
└── STORY-003  Notification preferences page

Step 2 — AI Implements With Context¶

You start working on TASK-001:

fcontext req set TASK-001 status in-progress

You ask the AI:

"Implement the SendGrid integration for TASK-001"

The AI reads _requirements/TASK-001.yaml and knows:

This task belongs to STORY-001 (email notifications)
Which belongs to EPIC-001 (notification system)
Sibling tasks include email templates (so the integration needs to support template rendering)
There are 3 stories total (so the integration should be generic enough for in-app notifications later)

It generates a better implementation because it understands the full scope, not just the isolated task.

Step 3 — Track Progress¶

fcontext req set TASK-001 status done
fcontext req set TASK-002 status in-progress

fcontext req board

┌─────────────┬─────────────┬───────────┐
│   Backlog   │ In Progress │   Done    │
├─────────────┼─────────────┼───────────┤
│ TASK-003    │ TASK-002    │ TASK-001  │
│ STORY-002   │             │           │
│ STORY-003   │             │           │
└─────────────┴─────────────┴───────────┘

Step 4 — Requirements Evolve¶

After launch, users want SMS notifications too. Requirements evolve:

fcontext req add "SMS + Email notifications for account events" -t story
fcontext req link STORY-004 supersedes STORY-001

# See the evolution
fcontext req trace STORY-004

STORY-001  Email notifications for account events
  └── superseded by → STORY-004  SMS + Email notifications for account events

The AI sees this evolution chain and understands: STORY-004 extends the original email-only scope to include SMS. When implementing, it knows to keep the existing email code and add SMS alongside it, not replace.

Why This Matters¶

graph LR subgraph "Without fcontext req" A1["Vague ask"] --> A2["AI guesses scope"] A2 --> A3["Rework"] end subgraph "With fcontext req" B1["Structured<br/>requirements"] --> B2["AI knows scope +<br/>hierarchy + history"] B2 --> B3["Right implementation<br/>first time"] end

Key takeaway: The AI doesn't just implement what you say — it implements what you say in the context of the full requirement tree, sibling tasks, parent stories, and evolution history.

Try It Yourself¶

pip install fcontext
cd your-project
fcontext init
fcontext enable copilot

# Define your feature
fcontext req add "My Feature" -t epic
fcontext req add "First story" -t story --parent EPIC-001

# Start implementing — the AI reads requirements automatically