Legacy Upgrade

    1

    Safe, incremental legacy modernization through seams, characterization tests, and strangler fig migrations.

    $5

    Secure checkout via Stripe

    30-day refund guarantee

    Converts to your local currency at checkout

    0 installsSecurity scanned

    Works with the AI tools you already use

    Claude CodeClaude CodeCursorCursorCodex CLICodex CLIGitHub CopilotGitHub CopilotGemini CLIGemini CLI+20 more

    Legacy Upgrade

    Example session with this skill installed

    We have a 4,000-line legacy payment class. It has no tests and handles 10 currency types. We need to move it to a new service without breaking current billing. where do we start?

    • Read your context and instructions
    • Compiled the legacy upgrade
    • Generated the UI component

    Current state

    4,000-line payment class, no test coverage, supporting 10 currencies.

    Slices

    1. Create a PaymentGateway interface.
    2. Generate characterization tests from 90 days of successful transactions.
    3. Shadow traffic to new service.

    First slice

    Extract the interface to wrap the legacy class.

    legacy-upgrade.tsx

    TSX · React component

    Generated

    Example file from a real run - the skill writes it into your workspace.

    Connects securely to your tools. The creator never sees your data.

    What you get

    Identify seams to isolate legacy code without breaking dependencies.Generate characterization tests to pin load-bearing behavior.Design dual-write and backfill sequences for safe data migrations.Create rollout plans with kill switches and percentage-based cohorts.

    About this skill

    The problem

    Rewrites fail when they attempt to replace a monolith in a single release. Developers lack the tooling to safely sequence changes, leading to stalled migrations, untested edge cases, and catastrophic cutovers.

    What it does

    • Identifies code seams to isolate legacy logic without breaking callers.
    • Generates characterization test scaffolding to pin existing behavior, including bugs.
    • Plans incremental migrations using the Strangler Fig pattern and vertical slicing.
    • Structures data migrations with dual-write, backfill, and reconciliation sequences.
    • Drafts rollout plans with kill switches, cohorts, and clear rollback triggers.

    Why this beats prompting it yourself

    General AI tends to suggest "big bang" rewrites that ignore the reality of production data. These rules enforce a specific, safe sequence that prioritizes shippable increments and verified behavior over risky code replacements.

    Use cases

    • Extracting a complex pricing module from a monolith into a microservice.
    • Modernizing a database schema while keeping the application online.
    • Implementing feature flags to safely test new logic against production traffic.
    • Scoring and prioritizing technical debt based on cost and change frequency.

    Known limitations

    Does not execute migrations, flip feature flags in production, or read live traffic. All actions must be performed by the developer.

    How to install

    Works the same in every agent - Claude, Cursor, Codex, Copilot and 20+ more.

    ~30 seconds
    1. 1

      Download the ZIP

      Free skills download straight away. Paid skills unlock right after purchase.

    2. 2

      Unzip into your skills folder

      Every agent reads skills from one folder on your machine. Drop the unzipped folder in there.

    3. 3

      Ask your agent to use it

      Restart the agent if it was already running. It picks the skill up automatically - no config needed.

    Skills folder by agent

    Click the path to copy it. Create the folder if it does not exist yet.

    Reviews

    No reviews yet

    Be one of the first to try it. Every listed skill passes our trust checks below.

    Security scanned

    Passed our 8-point scan before listing

    Fresh listing

    Recently published to Agensi

    30-day refund

    Not a fit? Get your money back

    Trust & safety

    Security scanned

    Verified clean 27 days ago

    • Passed all security checks, Safe to install

    Listed27 days ago

    Frequently Asked Questions