What is legacy-modernise?

A step-by-step approach for moving the business rules in an old web application into a cleaner service, such as one built with FastAPI. It includes tests that describe current behaviour and checks that the new service matches it.

Use it to analyse, refactor, or port a legacy web application while preserving its behaviour and organising the replacement into four layers.

It reduces the risk of changing an old system before its existing behaviour is understood. It also defines when the old code can be retired.

legacy-modernise — Skill for Claude Code by marcus-ant

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 marcus-ant/cc-agents-workshop-fleetos --skill legacy-modernise

Clone the repo

git clone --depth 1 https://github.com/marcus-ant/cc-agents-workshop-fleetos

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/marcus-ant/cc-agents-workshop-fleetos/legacy-modernise/github.svg)](https://agentmods.dev/skills/marcus-ant/cc-agents-workshop-fleetos/legacy-modernise)

Your own site

<a href="https://agentmods.dev/skills/marcus-ant/cc-agents-workshop-fleetos/legacy-modernise"><img src="https://agentmods.dev/badge/skills/marcus-ant/cc-agents-workshop-fleetos/legacy-modernise/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/marcus-ant/cc-agents-workshop-fleetos/legacy-modernise"><img src="https://agentmods.dev/badge/skills/marcus-ant/cc-agents-workshop-fleetos/legacy-modernise.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 66 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 785 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 unknown 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.

Model	Per session	Once invoked
Fable 5.1	$0.00066	$0.00785
Opus 5.5	$0.00026	$0.00314
Sonnet 5.5	$0.00013	$0.00157
Haiku 4.5	$0.00007	$0.00078

Measured 2mo ago against content hash acf1977c8c16, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

legacy-modernise 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 2mo 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.

solutions/2_code_modernisation/solution/.claude/skills/legacy-modernise/SKILL.md · 54 lines

The source is not reproduced here

No licence file

Read it on GitHub

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.

2mo ago First seen · 54 lines · 66 tokens per session scan A acf1977c8c16

Subscribe to this mod's changes

legacy-modernise is a skill published in the GitHub repository marcus-ant/cc-agents-workshop-fleetos (5 stars, last pushed 6mo ago), with no licence file. It adds 66 tokens to every session and 785 once invoked, about $0.0003 per session on Opus 5.5. 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.

Backend and APIs

legacy-modernise next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
legacy-modernisemarcus-ant/cc-agents-workshop-fleetos	Skill	5	6mo ago	none	A	66	Claude Code
mem0-oss-to-platformmem0ai/mem0	Skill	69k	today	Apache-2.0	A	217	Claude Code, Codex
azure-mgmt-botservice-dotnetmicrosoft/skills	Skill	3.2k	today	MIT	A	78	Claude Code
fastapi-router-pymicrosoft/skills	Skill	3.2k	today	MIT	A	46	Claude Code
api-designericrisco/rsc-harness	Skill	503	2d ago	MIT	A	105	Claude Code, Codex
migrate-segw-to-raparc-mcp/arc-1	Skill	252	yesterday	MIT	A	106	Claude Code
telnyx-messaging-hosted-curlteam-telnyx/ai	Skill	224	2d ago	MIT	A	45	Claude Code