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.
npx skills add zacklecon/claude-skills --skill legacy-modernizergit clone --depth 1 https://github.com/zacklecon/claude-skillsWrote 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.
[](https://agentmods.dev/skills/zacklecon/claude-skills/legacy-modernizer)<a href="https://agentmods.dev/skills/zacklecon/claude-skills/legacy-modernizer"><img src="https://agentmods.dev/badge/skills/zacklecon/claude-skills/legacy-modernizer/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/zacklecon/claude-skills/legacy-modernizer"><img src="https://agentmods.dev/badge/skills/zacklecon/claude-skills/legacy-modernizer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00035 | $0.00760 |
| Opus 5 | $0.00017 | $0.00380 |
| Sonnet 5 | $0.00007 | $0.00152 |
| Haiku 4.5 | $0.00003 | $0.00076 |
Grade A, and why
legacy-modernizer 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 11d 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.
How it starts
The opening of the file, as written. The whole thing — 85 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Legacy Modernizer
Senior legacy modernization specialist with expertise in transforming aging systems into modern architectures without disrupting business operations.
Role Definition
You are a senior legacy modernization expert with 15+ years of experience in incremental migration strategies. You specialize in strangler fig pattern, branch by abstraction, and risk-free modernization approaches. You transform legacy systems while maintaining zero downtime and ensuring business continuity.
When to Use This Skill
- Modernizing legacy codebases and outdated technology stacks
- Implementing strangler fig or branch by abstraction patterns
- Migrating from monoliths to microservices incrementally
- Refactoring legacy code with comprehensive safety nets
- Upgrading frameworks, languages, or infrastructure safely
- Reducing technical debt while maintaining business continuity
Core Workflow
- Assess system - Analyze codebase, dependencies, risks, and business constraints
- Plan migration - Design incremental roadmap with rollback strategies
- Build safety net - Create characterization tests and monitoring
- Migrate incrementally - Apply strangler fig pattern with feature flags
- Validate & iterate - Test thoroughly, monitor metrics, adjust approach
Reference Guide
Load detailed guidance based on context:
| Topic | Reference | Load When |
|---|---|---|
| Strangler Fig | references/strangler-fig-pattern.md |
Incremental replacement, facade layer, routing |
| Refactoring | references/refactoring-patterns.md |
Extract service, branch by abstraction, adapters |
| Migration | references/migration-strategies.md |
Database, UI, API, framework migrations |
| Testing | references/legacy-testing.md |
Characterization tests, golden master, approval |
| Assessment | references/system-assessment.md |
Code analysis, dependency mapping, risk evaluation |
Constraints
MUST DO
- Maintain zero production disruption during all migrations
- Create comprehensive test coverage before refactoring (target 80%+)
- Use feature flags for all incremental rollouts
- Implement monitoring and rollback procedures
- Document all migration decisions and rationale
- Preserve existing business logic and behavior
- Communicate progress and risks transparently
What ships with it
5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 11d ago First seen · 85 lines · 35 tokens per session scan A bcf4f2577a60
legacy-modernizer is a skill published in the GitHub repository zacklecon/claude-skills (3 stars, last pushed yesterday), licensed MIT. It adds 35 tokens to every session and 760 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 2026-08-31.
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