nw-legacy-refactoring-ddd

nw-legacy-refactoring-ddd is a skill for Claude Code from nWave-ai/nWave. It costs 45 tokens per session (1,927 once invoked), scanned A, original, MIT.

A guide to gradually restructuring legacy software using Domain-Driven Design, a way to organize code around real business areas and rules. It covers patterns for separating old and new parts while the system continues to evolve.

In plain words
What is it for?
Use it to plan legacy-system refactors, separate business contexts, introduce boundaries, and move parts of a monolith toward independent services.
Why use it?
Replacing or reorganizing a large old system all at once is risky and disruptive. Incremental techniques reduce the size of each change and keep business risk visible.

Skill for Claude Code

Written for Claude Code: disable-model-invocation in frontmatter.

Good fit Use it to plan legacy-system refactors, separate business contexts, introduce boundaries, and move parts of a monolith toward independent services.

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Install with agentmods
npx agentmods add skills/nwave-ai/nwave/nw-legacy-refactoring-ddd
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add nWave-ai/nWave --skill nw-legacy-refactoring-ddd
Clone the repo
git clone --depth 1 https://github.com/nWave-ai/nWave

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

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README.md
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Your own site · 80×15
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Per session 45 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,927 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00045 $0.01927
Opus 5 $0.00023 $0.00963
Sonnet 5 $0.00009 $0.00385
Haiku 4.5 $0.00005 $0.00193

Measured 8d ago against content hash 67c0b290c43d, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

nw-legacy-refactoring-ddd scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 8d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

nWave/skills/nw-legacy-refactoring-ddd/SKILL.md · 188 lines

How it starts

The opening of the file, as written. The whole thing — 188 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Legacy Refactoring with DDD

Refactoring legacy systems using Domain-Driven Design as the strategic compass. DDD tells you WHERE and WHY to refactor; traditional techniques (progressive-refactoring, mikado-method) tell you HOW.

Principle: "Start simple, grow big" -- incremental steps tested at each stage.

Decision Framework: Before Refactoring

Ask three questions before any DDD refactoring:

  1. Business value: what business outcome does refactoring this area enable?
  2. Risk: what breaks if we refactor vs. if we do not?
  3. Cost: time, effort, disruption -- is it justified?

When NOT to Refactor

  • System scheduled for replacement
  • Stable system with no new development
  • Cost exceeds benefit
  • Team lacks DDD experience with no learning budget
  • Domain is genuinely simple (CRUD-dominated)

Cynefin-Refactoring Mapping

Cynefin Domain Refactoring Approach
Clear Apply established patterns directly; standard refactoring catalogs
Complicated Analyze with experts, then apply patterns; multiple valid solutions
Complex Probe with safe-to-fail experiments; EventStorming to discover patterns
Chaotic Act first to stabilize, then refactor; emergency patches acceptable
Confusion Gather information before deciding; avoid premature refactoring

Migration Methodology (4 Phases)

Phase 1: Understand and Stabilize

  1. Run EventStorming to map current system (Big Picture)
  2. Assess complexity using Cynefin framework
  3. Write characterization tests for critical paths (Feathers technique)
  4. Identify bounded contexts in existing codebase via language divergence

Phase 2: Modularize the Monolith

  1. Introduce module structure aligned with bounded contexts
  2. Use mediator pattern for initial decoupling between modules
  3. Apply fitness functions to measure progress (coupling, cohesion, dependency direction)
  4. Refactor database schemas toward context alignment

Phase 3: Introduce Events and CQRS

  1. Replace mediator with event-driven communication
  2. Implement CQRS for contexts benefiting from read/write separation
  3. Split databases per bounded context using expand/contract pattern
  4. Use event-based data synchronization for cross-context data needs

Read the full file on GitHub · 188 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 8d ago First seen · 188 lines · 45 tokens per session scan A 67c0b290c43d

Subscribe to this mod's changes

nw-legacy-refactoring-ddd is a skill published in the GitHub repository nWave-ai/nWave (610 stars, last pushed 5d ago), licensed MIT. It adds 45 tokens to every session and 1,927 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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