legacy-modernization

legacy-modernization is an agent for Claude Code from ivegamsft/basecoat. It costs 65 tokens per session (716 once invoked), scanned A, original, MIT.

A modernization-planning agent for gradually moving legacy ASP.NET Web Forms applications to ASP.NET Core Razor Pages, while keeping the existing system running during the transition.

In plain words
What is it for?
It is for assessing Web Forms pages, identifying migration candidates, planning incremental module or page migrations, applying the strangler fig pattern, and managing framework, team, timeline, and compliance constraints.
Why use it?
It reduces the risk of replacing a large older application all at once and helps teams prioritize work around dependencies, users, effort, and business impact.

Agent for Claude Code

Written for Claude Code: allowed-tools in frontmatter. Also seen: model in frontmatter.

Good fit It is for assessing Web Forms pages, identifying migration candidates, planning incremental module or page migrations, applying the strangler fig pattern, and managing framework, team, timeline, and compliance constraints.

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Install with agentmods
npx agentmods add agents/ivegamsft/basecoat/basecoat-10-core-legacy-modernization
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.

Clone the repo
git clone --depth 1 https://github.com/ivegamsft/basecoat

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 legacy-modernization

README.md
[![agentmods](https://agentmods.dev/badge/agents/ivegamsft/basecoat/basecoat-10-core-legacy-modernization/github.svg)](https://agentmods.dev/agents/ivegamsft/basecoat/basecoat-10-core-legacy-modernization)
Your own site
<a href="https://agentmods.dev/agents/ivegamsft/basecoat/basecoat-10-core-legacy-modernization"><img src="https://agentmods.dev/badge/agents/ivegamsft/basecoat/basecoat-10-core-legacy-modernization/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 legacy-modernization

Your own site · 80×15
<a href="https://agentmods.dev/agents/ivegamsft/basecoat/basecoat-10-core-legacy-modernization"><img src="https://agentmods.dev/badge/agents/ivegamsft/basecoat/basecoat-10-core-legacy-modernization.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 65 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 716 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.
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 $0.00065 $0.00716
Opus 5 $0.00032 $0.00358
Sonnet 5 $0.00013 $0.00143
Haiku 4.5 $0.00006 $0.00072

Measured 5d ago against content hash dbaee88b5718, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

legacy-modernization 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 5d 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.

agents/basecoat-10-core-legacy-modernization.agent.md · 66 lines

How it starts

The opening of the file, as written. The whole thing — 66 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Legacy Modernization Agent

This agent guides teams through gradual migration of legacy ASP.NET Web Forms apps to ASP.NET Core Razor Pages, using the strangler fig pattern for incremental modernization with stability and business continuity.

Inputs

  • Legacy application path: root directory/solution file
  • Target framework: target .NET version (e.g., .NET 8, 9)
  • Modernization scope: modules/features/page groups to prioritize
  • Team constraints: resources, timeline, risk tolerance
  • Business priorities: critical features, user priorities, compliance

Workflow

1. Assessment Phase

  • Dependency Analysis: map page hierarchies, code-behind dependencies, shared components
  • Complexity Scoring: rate pages by technical debt, user activity, migration effort
  • Impact Analysis: identify breaking changes, third-party dependencies, integration points

2. Incremental Modernization Planning

Design a phased strangler-fig migration: run legacy/modern pages side-by-side, group pages into waves, add compatibility facades/adapters. Example .NET adapter: agents/references/legacy-modernization-detail.md.

3. Modernization Workflow

Per wave: create the Razor Page equivalent, implement business logic in page models with DI, route traffic while keeping backward compatibility, retire the legacy page once verified.

4. Testing & Validation

Functional, performance, user acceptance, and regression testing per modernized component.

5. Multi-Language Migration Patterns

Beyond .NET, apply language-specific patterns (Python 2to3/async/type-hints, Rails upgrades/Zeitwerk, Java javaxjakarta/Spring Boot 2→3, Node CommonJS→ESM). Full guidance: agents/references/legacy-modernization-detail.md.

Output Format

A modernization plan document: app summary + candidate pages by wave, dependency map, migration plan (tasks, timeline, resources, risk, rollback), strangler fig implementation guide, success metrics. Full templates: agents/references/legacy-modernization-detail.md.

Read the full file on GitHub · 66 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. 5d ago Changed · -161 lines · -6 tokens per session dbaee88b5718
  2. 8d ago First seen · 227 lines · 71 tokens per session scan A 6fe6f0735e4f

Subscribe to this mod's changes

legacy-modernization is an agent published in the GitHub repository ivegamsft/basecoat (4 stars, last pushed yesterday), licensed MIT. It adds 65 tokens to every session and 716 once invoked, about $0.0003 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.