Dependency Patterns

Core Principle

Minimize dependencies, maximize parallelism.

Every blockedBy relationship = serial execution = slower completion.

Dependency Types

1. Data Dependency

Task B needs output from Task A.

Task A: Create user table
Task B: Implement user queries (blockedBy: A)

2. File Conflict Prevention

Tasks modify same file.

Task A: Add auth middleware
Task B: Add logging middleware (same file)
→ One blocks other to prevent merge conflicts

3. Logical Ordering

Makes sense to do A before B.

Task A: Implement core feature
Task B: Add error handling (blockedBy: A)

Parallel Patterns

Fan-Out (Maximum Parallelism)

       ┌── Task B
Task A ├── Task C
       └── Task D

# All of B, C, D can run parallel after A

Pipeline (Sequential)

Task A → Task B → Task C

# Only when each truly depends on previous

Diamond (Converge)

       ┌── Task B ──┐
Task A ┤            ├── Task D
       └── Task C ──┘

# D waits for both B and C

Parallel Tracks

Track 1: A1 → A2 → A3
Track 2: B1 → B2 → B3
Final:   Both tracks → Integration

# Completely independent tracks

Dependency Rules

MUST Add Dependency When:

• Task reads data that another task creates
• Tasks modify the same file
• Task tests code that another task implements
• Integration task combines outputs

MUST NOT Add Dependency When:

• Tasks work on completely different files
• Tasks are conceptually related but not technically dependent
• "It makes sense to do A first" (not enough reason)

Setting Dependencies

# After creating tasks
TaskUpdate(taskId="3", addBlockedBy=["1", "2"])

# This means Task 3 waits for both 1 and 2

Critical Path

The longest chain of dependencies = total minimum time.

A(1) → B(2) → D(1) = 4 units
A(1) → C(3) → D(1) = 5 units  ← Critical path

Optimizing C has more impact than B.

Anti-Patterns

Over-Serialization

❌ A → B → C → D → E (when B, C, D could parallel)

Missing Dependencies

❌ A and B both create migrations (conflict!)
✅ A → B or B → A

Circular Dependencies

❌ A blockedBy B, B blockedBy A
(TaskUpdate will reject this)