jscpd is a source-code copy/paste detector that finds duplicated code blocks across files and reports the results in formats such as SARIF, HTML, and badges. Developers use it for code-quality checks, continuous integration, pre-commit hooks, and agent-assisted reviews across many programming-language formats. Its catalogue skills help coding agents run or interpret duplication checks.
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 kucherenko/jscpd --skill code-migrationgit clone --depth 1 https://github.com/kucherenko/jscpdWrote 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/kucherenko/jscpd/code-migration)<a href="https://agentmods.dev/skills/kucherenko/jscpd/code-migration"><img src="https://agentmods.dev/badge/skills/kucherenko/jscpd/code-migration/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/kucherenko/jscpd/code-migration"><img src="https://agentmods.dev/badge/skills/kucherenko/jscpd/code-migration.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 | $0.00110 | $0.04705 |
| Opus 5.5 | $0.00044 | $0.01882 |
| Sonnet 5.5 | $0.00022 | $0.00941 |
| Haiku 4.5 | $0.00011 | $0.00470 |
Grade A, and why
code-migration 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 14d 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 — 201 lines — stays where its author put it; the contents beside it link to each section on GitHub.
code-migration
jscpd --compare SOURCE TARGET pairs every function of one folder with the function of the other folder that does the same job, in any pair of languages, and lists the functions that have no counterpart. This skill uses it to measure a port: what is ported, what is left, and whether the port you just wrote was recognized.
A port runs in two phases: the tests first, then the code they check. A coverage report of the source's tests tells which tests exercise which function, so each function is ported together with the tests that prove it works. See Plan: tests first, then code.
Two words are used throughout:
- source: the implementation you port from, such as the iOS app, the Python library, or the JavaScript package;
- target: the implementation you port to, such as the Android app, the Rust crate, or the TypeScript rewrite.
Neither has to be old or new. The source may stay in production and keep changing, and the target may already hold features the source lacks. For two implementations that both live on (ios/ and android/), the same report shows parity; see Parity.
jscpd finds functions in JavaScript, TypeScript, JSX, TSX, Vue, Svelte, Astro, Python, Rust, Go, Java, Kotlin, C#, C, C++, PHP, Ruby, Scala and Swift. The compare-codebases skill explains how the comparison pairs functions and how to check its result; the jscpd skill covers the rest of the tool.
Setup
--compare pairs functions with a code embedding model that runs inside jscpd. Download it once (548 MB, CodeRankEmbed). Ask the user before you start the download:
npx jscpd --semantic-download
jscpd caches the vectors, so a repeat run embeds only the functions whose code changed and takes seconds.
Pick the two paths and keep them fixed for the whole port: the source first, the target second. Two paths are required, and they must not overlap (app/ and app/android/ is refused). The target may be empty at the start.
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.
- 14d ago Changed · +27 lines be844a0ce560
- 15d ago Changed 6ebcfdd5ea4f
- 16d ago First seen · 174 lines · 110 tokens per session scan A b4503e042be8
code-migration is a skill published in the GitHub repository kucherenko/jscpd (6,399 stars, last pushed yesterday), licensed MIT. It adds 110 tokens to every session and 4,705 once invoked, about $0.0004 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 2026-09-30.
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