framework-migration-legacy-modernize

framework-migration-legacy-modernize is a skill for Claude Code from rmyndharis/antigravity-skills. It costs 36 tokens per session (1,994 once invoked), scanned A, original, MIT.

A workflow for gradually replacing an outdated software system while keeping the existing system running. It uses the strangler fig pattern, where new parts take over from old parts in stages.

In plain words
What is it for?
Use it to assess old code, plan modernization phases, coordinate testing and security checks, and introduce replacement components incrementally.
Why use it?
It reduces the risk and disruption of replacing a large legacy system all at once.

Skill for Claude Code

Written for Claude Code: $ARGUMENTS substitution.

Good fit Use it to assess old code, plan modernization phases, coordinate testing and security checks, and introduce replacement components incrementally.

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Install with agentmods
npx agentmods add skills/rmyndharis/antigravity-skills/framework-migration-legacy-modernize
About the project

Antigravity Skill Vault is a collection of reusable Agent Skills for Google Antigravity, covering software development, operations, security, and business work. It is for people who want Antigravity agents to follow specialized expertise, personas, and structured workflows. The catalogue skills are entries from this collection.

rmyndharis/antigravity-skills · 1,522 stars · on GitHub

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 rmyndharis/antigravity-skills --skill framework-migration-legacy-modernize
Clone the repo
git clone --depth 1 https://github.com/rmyndharis/antigravity-skills

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.

agentmods badge for framework-migration-legacy-modernize

README.md
[![agentmods](https://agentmods.dev/badge/skills/rmyndharis/antigravity-skills/framework-migration-legacy-modernize/github.svg)](https://agentmods.dev/skills/rmyndharis/antigravity-skills/framework-migration-legacy-modernize)
Your own site
<a href="https://agentmods.dev/skills/rmyndharis/antigravity-skills/framework-migration-legacy-modernize"><img src="https://agentmods.dev/badge/skills/rmyndharis/antigravity-skills/framework-migration-legacy-modernize/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.

agentmods 80×15 button for framework-migration-legacy-modernize

Your own site · 80×15
<a href="https://agentmods.dev/skills/rmyndharis/antigravity-skills/framework-migration-legacy-modernize"><img src="https://agentmods.dev/badge/skills/rmyndharis/antigravity-skills/framework-migration-legacy-modernize.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 36 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,994 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 $0.00036 $0.01994
Opus 5 $0.00018 $0.00997
Sonnet 5 $0.00007 $0.00399
Haiku 4.5 $0.00004 $0.00199

Measured 7d ago against content hash babde8806c5a, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

framework-migration-legacy-modernize 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 7d 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.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

skills/framework-migration-legacy-modernize/SKILL.md · 132 lines

How it starts

The opening of the file, as written. The whole thing — 132 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Legacy Code Modernization Workflow

Orchestrate a comprehensive legacy system modernization using the strangler fig pattern, enabling gradual replacement of outdated components while maintaining continuous business operations through expert agent coordination.

[Extended thinking: The strangler fig pattern, named after the tropical fig tree that gradually envelops and replaces its host, represents the gold standard for risk-managed legacy modernization. This workflow implements a systematic approach where new functionality gradually replaces legacy components, allowing both systems to coexist during transition. By orchestrating specialized agents for assessment, testing, security, and implementation, we ensure each migration phase is validated before proceeding, minimizing disruption while maximizing modernization velocity.]

Use this skill when

  • Working on legacy code modernization workflow tasks or workflows
  • Needing guidance, best practices, or checklists for legacy code modernization workflow

Do not use this skill when

  • The task is unrelated to legacy code modernization workflow
  • You need a different domain or tool outside this scope

Instructions

  • Clarify goals, constraints, and required inputs.
  • Apply relevant best practices and validate outcomes.
  • Provide actionable steps and verification.

Phase 1: Legacy Assessment and Risk Analysis

1. Comprehensive Legacy System Analysis

  • Use Task tool with subagent_type="legacy-modernizer"
  • Prompt: "Analyze the legacy codebase at $ARGUMENTS. Document technical debt inventory including: outdated dependencies, deprecated APIs, security vulnerabilities, performance bottlenecks, and architectural anti-patterns. Generate a modernization readiness report with component complexity scores (1-10), dependency mapping, and database coupling analysis. Identify quick wins vs complex refactoring targets."
  • Expected output: Detailed assessment report with risk matrix and modernization priorities

2. Dependency and Integration Mapping

  • Use Task tool with subagent_type="architect-review"
  • Prompt: "Based on the legacy assessment report, create a comprehensive dependency graph showing: internal module dependencies, external service integrations, shared database schemas, and cross-system data flows. Identify integration points that will require facade patterns or adapter layers during migration. Highlight circular dependencies and tight coupling that need resolution."
  • Context from previous: Legacy assessment report, component complexity scores
  • Expected output: Visual dependency map and integration point catalog

Read the full file on GitHub · 132 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. 7d ago First seen · 132 lines · 36 tokens per session scan A babde8806c5a

Subscribe to this mod's changes

framework-migration-legacy-modernize is a skill published in the GitHub repository rmyndharis/antigravity-skills (1,522 stars, last pushed 1mo ago), licensed MIT. It adds 36 tokens to every session and 1,994 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.