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Agent skill

Cobol Modernization

by OpenHands in OpenHands/extensions

End-to-end COBOL to Java migration workflow. An agent skill from OpenHands/extensions.

MITAuto-check passedDevelopment

Install Cobol Modernization

skills CLI
$ npx skills add OpenHands/extensions --skill cobol-modernization -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install OpenHands/extensions cobol-modernization --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/OpenHands/extensions.git skills-src && mkdir -p .claude/skills && cp -r skills-src/plugins/cobol-modernization/skills/cobol-modernization .claude/skills/cobol-modernization && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
cobol-modernization
GitHub stars
158
Token cost
~820 tokens
SKILL.md length
243 words
Files
1
Skills in repo
78
Repo updated
First seen
Licence
MIT

At a glance

End-to-end COBOL to Java migration workflow. An agent skill from OpenHands/extensions.

  • Works in 4 steps: Build Setup → Mainframe Planning → Mainframe Removal → …
  • Tasks that involve Legacy modernization
  • SKILL.md covers Overview, Prerequisites, Quick Start and Workflow Phases, plus 2 more sections
  • Calls uv; needs LLM_API_KEY

What it does

Cobol Modernization is an agent skill from OpenHands/extensions. End-to-end COBOL to Java migration workflow. Handles build setup, mainframe dependency removal, and code migration with test validation.

Its SKILL.md is about 820 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts. Compatibility notes: Requires GnuCOBOL, Java 11+, Maven/Gradle, Python 3.13 with uv

It sits in Development, covering Legacy modernization and Code migrations. It works with Java and JUnit. The repository describes itself as: Public registry for OpenHands extensions. The licence is MIT.

When your agent uses it

  • Tasks that involve Legacy modernization
  • Tasks that involve Code migrations

Example prompts

  • “/cobol-modernization”

Requirements

  • Python 3
  • A credential in LLM_API_KEY
  • Compatibility (from SKILL.md): Requires GnuCOBOL, Java 11+, Maven/Gradle, Python 3.13 with uv

Workflow steps

4 steps, taken from the step headings in SKILL.md.

  1. Build Setup
  2. Mainframe Planning
  3. Mainframe Removal
  4. Java Migration

What it can do on your machine

Read from SKILL.md and the folder at commit d008b81. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Shell commands in SKILL.md call:

    • uv

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md. Its commands use uv, which can reach the network depending on how they are called.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names these keys or tokens, usually read from environment variables:

    • LLM_API_KEY

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

  • Compatibility

    Requires GnuCOBOL, Java 11+, Maven/Gradle, Python 3.13 with uv

    From compatibility in the SKILL.md frontmatter.

Context cost

Cobol Modernization loads about 820 tokens when it runs. Until then it costs about 39 tokens; SKILL.md has 243 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~39
When it runs · the whole SKILL.md, loaded when a task matches
~820

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from OpenHands/extensions at commit d008b81, republished under its MIT licence (© OpenHands). 243 words, ~820 tokens.

Download SKILL.mdSave it as .claude/skills/cobol-modernization/SKILL.md (or your agent's skills folder).
name
cobol-modernization
description
End-to-end COBOL to Java migration workflow. Handles build setup, mainframe dependency removal, and code migration with test validation.
compatibility
Requires GnuCOBOL, Java 11+, Maven/Gradle, Python 3.13 with uv
license
MIT
triggers
cobol modernization, cobol to java, cobol migration, mainframe migration

End-to-end workflow for migrating COBOL codebases to Java.

Overview

This plugin orchestrates a multi-phase COBOL modernization project:

  1. Build Setup — Configure compilation for both COBOL and Java, create test fixtures
  2. Mainframe Planning — Document transformations needed to remove mainframe dependencies
  3. Mainframe Removal — Convert CICS/VSAM code to standard COBOL
  4. Java Migration — Translate standardized COBOL to idiomatic Java

Prerequisites

  • GnuCOBOL compiler (cobc)
  • Java 11+ with Maven or Gradle
  • Python 3.13 with uv
  • LLM API key (Anthropic or OpenAI)

Quick Start

bash
export LLM_API_KEY="your-api-key"
export LLM_MODEL="anthropic/claude-3-5-sonnet-20241022"

uv run python -m lc_sdk_examples.cobol_modernization --src-path /path/to/cobol/project

PowerShell equivalent for the environment setup:

powershell
$env:LLM_API_KEY = "your-api-key"
$env:LLM_MODEL = "anthropic/claude-3-5-sonnet-20241022"

uv run python -m lc_sdk_examples.cobol_modernization --src-path C:\path\to\cobol\project

Workflow Phases

Phase 1: Build Setup

See ../build-setup/SKILL.md

Creates the foundation for the migration:

  • COBOL compilation environment (GnuCOBOL)
  • Java project structure (Maven/Gradle + JUnit 5)
  • Test fixtures with golden outputs from COBOL execution

Outputs:

  • build_notes.md — Build instructions
  • test-fixtures/ — Input/output test data
  • test_manifest.json — Test case mapping
Phase 2: Mainframe Planning

See ../mainframe-planning/SKILL.md

Creates a transformation guide without modifying code:

  • Maps CICS/VSAM constructs to standard COBOL equivalents
  • Documents error handling replacements
  • Identifies UI operations to stub

Output:

  • mainframe_dependency_removal_plan.md
Phase 3: Mainframe Removal

See ../mainframe-removal/SKILL.md

Applies the transformation guide:

  • Replaces EXEC CICS commands with file I/O
  • Adds FILE STATUS checking
  • Stubs BMS/screen operations

Verification:

  • Code compiles with GnuCOBOL
  • Runs with test fixtures
Phase 4: Java Migration

See ../to-java-migration/SKILL.md

Translates to idiomatic Java:

  • Proper Java conventions (not literal translations)
  • JUnit tests using golden outputs
  • COBOL references in comments

Done when:

  • All code compiles
  • All JUnit tests pass
  • No TODOs or stubs remain

Output Structure

your-project/
├── .lc-sdk/
│   ├── initial_batch_graph.json
│   ├── fixed_batch_graph.json
│   └── mainframe_dependency_removal_plan.md
├── test-fixtures/
│   ├── inputs/
│   └── expected_outputs/
├── test_manifest.json
├── src/main/java/
└── src/test/java/

Troubleshooting

See ../../references/troubleshooting.md for common issues and solutions.

© OpenHands, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in plugins/cobol-modernization/skills/cobol-modernization of OpenHands/extensions.

Open the folder on GitHubat commit d008b81

Compare with similar skills

Cobol Modernization next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Cobol Modernization compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Cobol Modernization this skillOpenHands/extensions158—~820Automated safety check: PassMIT
Java 21 Developer Guide for Grailsapache/grails-core2.9k—~1.9kAutomated safety check: PassApache-2.0
Convert Internal Package to TypeScriptTryGhost/Ghost55k—~1.2kAutomated safety check: PassMIT
jscpd Code Migration Trackerkucherenko/jscpd6.4k—~5kAutomated safety check: PassMIT
Code Qualitypiomin/claude-ai-spring-boot1.3k—~2.2kAutomated safety check: PassApache-2.0
Rails Upgrade Assistantombulabs/claude-code_rails-upgrade-skill389—~2.7kAutomated safety check: PassMIT

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Works with

Categories

Questions about Cobol Modernization

What does Cobol Modernization do?

End-to-end COBOL to Java migration workflow. An agent skill from OpenHands/extensions. Cobol Modernization is an agent skill from OpenHands/extensions. End-to-end COBOL to Java migration workflow.

When should I use Cobol Modernization?

Cobol Modernization fits situations like: tasks that involve Legacy modernization; tasks that involve Code migrations.

How do I install Cobol Modernization in Claude Code?

Run `npx skills add OpenHands/extensions --skill cobol-modernization -a claude-code`. Or copy the skill folder (plugins/cobol-modernization/skills/cobol-modernization in OpenHands/extensions) into .claude/skills/cobol-modernization in your project. Claude Code loads it when a task matches its description.

How do I install Cobol Modernization in Codex?

Run `npx skills add OpenHands/extensions --skill cobol-modernization -a codex`. Or copy the skill folder (plugins/cobol-modernization/skills/cobol-modernization in OpenHands/extensions) into .agents/skills/cobol-modernization in your project. Codex loads it when a task matches its description.

Can I use Cobol Modernization in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add OpenHands/extensions --skill cobol-modernization -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/cobol-modernization, .gemini/skills/cobol-modernization, .github/skills/cobol-modernization and .opencode/skills/cobol-modernization in your project.

What does Cobol Modernization need to run?

Going by SKILL.md and its folder, Cobol Modernization needs the command-line tools its instructions call (uv) and credentials named LLM_API_KEY. Our summary lists: Python 3; A credential in LLM_API_KEY. Compatibility (from SKILL.md): Requires GnuCOBOL, Java 11+, Maven/Gradle, Python 3.13 with uv.

Does Cobol Modernization access the network?

SKILL.md contains no URLs. Its commands use uv, which can reach the network depending on how they are called. This is read from the text; nothing was executed.

Is Cobol Modernization safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Cobol Modernization use?

Cobol Modernization is published under the MIT licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Cobol Modernization use?

About 820 tokens (SKILL.md is roughly 3.3k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Cobol Modernization?

Skills that share tags, products or a category with Cobol Modernization: Java 21 Developer Guide for Grails (apache/grails-core, 2.9k stars), Convert Internal Package to TypeScript (TryGhost/Ghost, 55k stars), jscpd Code Migration Tracker (kucherenko/jscpd, 6.4k stars) and Code Quality (piomin/claude-ai-spring-boot, 1.3k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Cobol Modernization?

OpenHands (a GitHub organization) maintains it in OpenHands/extensions, which has 158 GitHub stars. The repository holds 78 skills in this directory. The repository was last updated on October 7, 2026.

Source: OpenHands/extensions on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.