Validate Sibling Dependency Law (ADR-020)

Purpose

Enforces the Sibling Dependency Law — a critical architectural constraint that prevents dependency spaghetti in the Xentri documentation hierarchy.

Core Rules

1. Single-Parent Inheritance: Every entity has exactly ONE parent, encoded in its requirement ID
2. Sibling-Only Dependencies: requires_interfaces can only reference siblings (nodes with same parent)
3. Inherited Access: Cross-branch dependencies must be declared at the common ancestor level
4. Violation = Redesign: If validation fails, STOP and redesign — do not create workarounds

Quick Validation

Run this command to check for violations:

pnpm exec tsx scripts/validation/validate-dependencies.ts --path docs

Decision Tree

Is Target a sibling of Source? (same direct parent)
│
├─ YES → ✅ VALID: Declare requires_interfaces directly
│
└─ NO → Find common ancestor
        │
        ├─ Ancestor already has access? → ✅ Use inherited_interfaces
        │
        └─ Ancestor lacks access?
            │
            ├─ Can ancestor declare it? → Bubble up the dependency
            │
            └─ Structural problem? → Redesign required (or ADR exception)

Examples

✅ Valid: Sibling Dependency

# God-View depends on KPI-Center (both children of Pulse)
Source: docs/strategy/pulse/god-view/
Target: docs/strategy/pulse/kpi-center/
Result: VALID — same parent (Pulse)

❌ Invalid: Cross-Branch Dependency

# God-View trying to depend directly on Shell
Source: docs/strategy/pulse/god-view/
Target: docs/platform/shell/
Result: INVALID — different branches (Strategy vs Platform)
Resolution: Strategy must declare dependency on Shell; God-View inherits

✅ Valid: Inherited Access

# God-View using Core-API via Constitution-level declaration
Source: docs/strategy/pulse/god-view/
Target: docs/platform/core-api/
Context: Constitution (docs/platform/) declares IC-API-001
Result: VALID via inheritance

When to Use This Skill

Claude will automatically invoke this skill when you:

• Ask about module dependencies
• Create new requires_interfaces declarations
• Review architecture for dependency violations
• Add interfaces between entities
• Mention "ADR-020", "sibling dependency", or "cross-module dependency"

Resolution Options

When a violation is detected:

1. Bubble Up: Declare the dependency at the common ancestor level
2. Redesign: Restructure entities to be siblings, or use events instead
3. Exception (last resort): Create ADR documenting the exception with remediation plan

Full Documentation

See docs/platform/architecture/adr-020-sibling-dependency-law.md for complete specification including:

• Requirement file format
• Dependency resolution algorithm
• Escape hatch for exceptions
• Enforcement mechanisms (CI, pre-commit, review)