Task Decomposition

# ONE big task:
"Add a complete user authentication system including:
 - Login and registration forms
 - Password hashing and verification
 - JWT or session tokens
 - Remember me functionality
 - Password reset via email
 - Role-based access control
 - Admin panel for user management"

# What happens:
- Agent reads 20+ files to understand the codebase
- Context grows to 80,000+ tokens
- Agent tries to hold all requirements in one pass
- Inconsistencies appear between frontend forms and backend logic
- Token cost: very high. Quality: often poor.

# SEVEN focused tasks:
Task 1: Create users table migration and UserModel with password hashing
        Context needed: /config/database.php, existing model template
        Tokens: ~3,000

Task 2: Build login form (POST /auth/login) using AuthController
        Context needed: Task 1 output (UserModel), routes.php
        Tokens: ~2,500

Task 3: Build registration form with validation
        Context needed: UserModel, existing form examples
        Tokens: ~2,000

Task 4: Implement session-based auth with remember_me cookie
        Context needed: AuthController from Task 2, config/app.php
        Tokens: ~2,500

Task 5: Password reset flow (request email + reset form)
        Context needed: UserModel, Mailer class, email templates
        Tokens: ~3,000

Task 6: RBAC - add role column, middleware, @role annotations
        Context needed: UserModel, existing middleware pattern
        Tokens: ~2,500

Task 7: Admin user management panel
        Context needed: UserModel, admin layout template
        Tokens: ~3,000

Total tokens: ~18,500 (vs 80,000+ monolith)
Each task is accurate because it has focused, relevant context only

import anthropic
import concurrent.futures

client = anthropic.Anthropic()

def run_subtask(task: dict) -> dict:
    response = client.messages.create(
        model="claude-sonnet-4-6",
        max_tokens=2048,
        system=task["system"],
        messages=[{"role": "user", "content": task["prompt"]}],
    )
    return {"task": task["name"], "result": response.content[0].text}

# Independent tasks that can run simultaneously
subtasks = [
    {
        "name": "Write UserModel",
        "system": "PHP 8.2 developer. PDO only. No raw SQL.",
        "prompt": f"Write UserModel class with findByEmail(), create(), hashPassword(). Schema: {db_schema}",
    },
    {
        "name": "Write UserModelTest",
        "system": "PHPUnit developer. Mock the DB layer.",
        "prompt": "Write PHPUnit tests for UserModel. Test findByEmail with valid/invalid email.",
    },
    {
        "name": "Write migration",
        "system": "MySQL 8 DBA.",
        "prompt": f"Write CREATE TABLE migration for users: {user_fields}",
    },
]

# Run all three in parallel
with concurrent.futures.ThreadPoolExecutor(max_workers=3) as executor:
    results = list(executor.map(run_subtask, subtasks))

for r in results:
    print(f"[{r['task']}]\n{r['result']}\n")

def chain_tasks(steps: list) -> list:
    results = []
    previous_output = ""

    for step in steps:
        # Only pass the RELEVANT part of the prior output, not everything
        prompt = step["prompt_template"].format(prior=previous_output[:2000])

        response = client.messages.create(
            model="claude-sonnet-4-6",
            max_tokens=1024,
            system=step["system"],
            messages=[{"role": "user", "content": prompt}],
        )
        previous_output = response.content[0].text
        results.append({"step": step["name"], "output": previous_output})

    return results

steps = [
    {
        "name": "Find bug location",
        "system": "PHP developer. Be concise.",
        "prompt_template": f"In auth.php lines 45-90, find the root cause of: session_regenerate_id fails. Report: file:line only. Code: {code_snippet}",
    },
    {
        "name": "Write fix",
        "system": "PHP developer. Show diff only.",
        "prompt_template": "Fix the issue found at {prior}. Show the corrected lines as a diff.",
    },
    {
        "name": "Write test",
        "system": "PHPUnit developer.",
        "prompt_template": "Write one test to verify the fix: {prior} is correct.",
    },
]