Step 2: Backend Implementation

Prerequisites

□ GATE 1 PASSED (spec complete)
□ Spec exists: specs/{type}/{feature-name}.md

Process

1. Load Context

cat specs/{type}/{feature-name}.md     # Spec (source of truth)
cat .claude/project.md                 # Project patterns

2. Dependency Mapping (BEFORE any code)

Load dependency-map skill and map ALL needed items:

cat skills/dependency-map.md

Extract from spec:

Service	Purpose	Exists?	Action
{service}	{purpose}	?	CREATE/REUSE

Utility	Purpose	Exists?	Action
{utility}	{purpose}	?	CREATE/REUSE

Quick existence check:

ls src/services/ 2>/dev/null
ls src/utils/ src/lib/ 2>/dev/null
grep -r "{function-name}" src/utils/ 2>/dev/null

Create stubs for ALL missing items FIRST:

// Create stub files with throw new Error('Not implemented')
// This ensures no "module not found" during implementation

3. Implementation Order

Based on dependency map:

1. Create stubs for all missing
2. Implement services (no dependencies first)
3. Implement services (with dependencies)
4. Implement routes (uses services)

4. Delegate to Implementer

Use Task tool with implementer agent:

Implement backend for {feature-name}:
- Dependency map: .claude/deps/{feature-name}.md
- All endpoints from spec
- All validation rules from spec
- All error responses from spec
- Follow project patterns

5. Key Requirements

From spec:

• Every endpoint implemented
• Every validation rule
• Every error response (400, 401, 403, 404, 409, 500)

Quality:

• No TODO/FIXME
• Small functions (≤30 lines)
• Fail fast (validations at top)
• Max 3 levels nesting

6. Spec Gap Protocol

If you discover gaps during implementation:

Use AskUserQuestion:
"Found gap in spec: {issue}
Options:
1. Update spec to {A}
2. Update spec to {B}"

Update spec first, then implement.

7. Validate Gate

Use Task tool with gate-keeper agent:

Validate GATE 2 for {feature-name}

See gate-2-backend skill for all 17 criteria.

Output

• Implementation in src/
• Migrations in migrations/ (if needed)