Phoenix Context Boundary Validation

Analyze module dependencies to ensure clean context separation and proper architectural boundaries.

Usage

/phx:boundaries              # Check for violations
/phx:boundaries --assess     # Score context health (0-100)
/phx:boundaries --fix        # Suggest fixes for violations

--assess Mode: Context Health Score

Evaluate overall boundary health with a quantified score.

Metrics Calculated

Commands for Assessment

Use Glob to count .ex files per context directory under lib/my_app/*/. Use Grep to count public function definitions per context file under lib/my_app/*.ex. Run mix xref graph --format stats for dependency analysis. Run mix xref graph --format cycles --label compile for compile-time circular dependencies.

Output Format

## Context Health Assessment

### Overall Score: 82/100 (Good)

| Context | Modules | API | Fan-Out | Fan-In | Score |
|---------|---------|-----|---------|--------|-------|
| Accounts | 5 | 12 | 2 | 4 | 95 |
| Orders | 18 | 45 | 8 | 3 | 62 |
| Shared | 2 | 8 | 0 | 12 | 78 |

### Issues Found

1. **Orders** - Too large (18 modules, 45 funcs)
   - Consider: Extract Fulfillment, Invoicing sub-contexts

2. **Orders** - High fan-out (8 contexts)
   - Consider: Review if all dependencies necessary

### Recommendations

- Split Orders into Orders + Fulfillment
- Review Accounts ← Billing dependency

Iron Laws - Never Violate These

1. Controllers call only contexts - No direct Repo access from web layer
2. Schemas are pure data - No side effects, no Repo calls in schema modules
3. Contexts own their schemas - Don't import schemas from other contexts
4. Explicit dependencies only - Cross-context calls must be intentional
5. DO NOT refactor context boundaries without running mix xref first — Refactoring without dependency data creates new violations; always map the dependency graph before moving modules

Dependency Rules

Analysis Commands

Check Compile Dependencies

Run mix xref graph --label compile-connected.

Find What Depends on a Context

Run mix xref graph --sink MyApp.Accounts --label compile.

Find What a Module Calls

Run mix xref callers MyApp.Accounts.get_user!/1.

Check for Circular Dependencies

Run mix xref graph --format cycles --label compile.

Red Flags to Detect

Boundary Verification Process

1. Run mix xref graph --label compile-connected for overview
2. Check for context cross-contamination
3. Verify no direct Repo calls from web layer
4. Ensure schemas have no side effects
5. Validate explicit cross-context dependencies

Next Steps

Always end with actionable follow-up — findings without a plan get lost:

- `/phx:plan` — Create a plan to fix violations (recommended for 3+ issues)
- `/phx:quick` — Fix a single boundary violation directly
- `/phx:review` — Review specific modules for deeper issues

References

For detailed patterns, see:

• ${CLAUDE_SKILL_DIR}/references/context-design.md - Context design principles
• ${CLAUDE_SKILL_DIR}/references/refactoring-boundaries.md - Fixing boundary violations