OL Code + Claude: The IDE Layer That Makes COBOL Modernization Real

Anthropic's new COBOL modernization playbook is excellent. But AI can only modernize code it can reach. OL Code is the access layer, a browser-based IDE built for Mainframes and AS/400, that makes the whole thing possible.

The Playbook Dropped. Now What?

On February 23, 2026, Anthropic published a detailed guide on how Claude Code can help organizations tackle COBOL modernization, one of the most expensive, risk-laden problems in enterprise IT. The article makes a compelling case: AI can automate the exploration and analysis phases that once required years of consultant time, mapping dependencies, surfacing hidden risks, and documenting workflows that exist only in production code.

If you haven't read it yet, you should: How AI Helps Break the Cost Barrier to COBOL Modernization. It's one of the clearest framings of the modernization problem we've seen.

But as we read it at OpenLegacy, one thing stood out: the playbook describes what AI can do with your COBOL once someone has access to it. It doesn't talk about the access problem itself.

That problem is real, and it's where most modernization projects quietly stall.

The Access Problem Nobody Talks About

COBOL lives on Mainframes and AS/400 systems. These aren't cloud-native environments where you spin up a dev container and start editing. Getting a developer, let alone an AI tool, productive on legacy code means solving a stack of practical problems first:

• How does a developer browse thousands of COBOL programs without a local mainframe setup?
• How do you search across a codebase when the code is locked behind host access?
• How do you make an edit, recompile, and validate without a dedicated terminal emulator on every machine?
• How do you bring AI assistance to code that can't easily leave the premises?

These aren't edge cases. They're the daily reality of every team working on legacy modernization. And they're the reason the "armies of consultants" model persisted for so long because access and tooling were the bottleneck, not just knowledge.

What OL Code by OpenLegacy Is

OL Code is a free, lightweight, web-based IDE built specifically for legacy environments. It runs as a local server (JAR or Docker) and connects directly to your Mainframe or AS/400 over TCP/IP. No code leaves your environment. No heavy desktop client required. Just a browser.

Once connected, your team gets a modern development experience on top of legacy code:

Browse & Navigate

Explore your full COBOL and RPG codebase from any browser. Search across programs, copybooks, and JCL with full-text filtering. Navigate cross-references and dependencies without a terminal emulator.

Edit & Compile

Syntax highlighting, autocomplete, and smart editing for COBOL, RPG, JCL, and CICS programs. Compile directly from the interface. Download the output. Create and manage compilation templates for repeatable workflows.

AI Assistance — Including Claude

OL Code's built-in AI assistant, powered by models including Claude, sits right next to the code. Ask it to explain a program's logic. Request a refactor. Get documentation generated on the spot. The AI has context for what it's looking at because it's looking at the same thing your developer is.

Connect to OpenLegacy Hub for Deeper Analysis

For teams going further, OL Code integrates with OpenLegacy Hub for dependency mapping, code analysis, testing, and automatic API generation from legacy code exactly the kind of output Anthropic's playbook describes as essential preparation for migration.

How OL Code and Claude Work Together in Practice

Anthropic's playbook describes a modernization approach built around three phases:

• automated exploration and discovery,

• risk analysis and opportunity mapping, and

• incremental implementation.

OL Code slots into this workflow at every stage.

In the exploration phase, a developer uses OL Code to pull up a target program, browse its dependencies, and bring Claude's AI assistant in to annotate and explain the logic without ever copying code to a local machine or a cloud tool.

In the analysis phase, OL Code's cross-reference and dependency views (especially with Hub connected) surface the module-level coupling that Anthropic flags as the primary risk factor in COBOL migration. Teams can see which programs share data structures and which are isolated candidates for early modernization.

In the implementation phase, developers use OL Code to make incremental edits, compile in place, and validate keeping the feedback loop tight while the legacy system stays live and unchanged until the modernized component is ready to replace it.

See It in Action

We've recorded a walkthrough of OL Code showing exactly what this looks like: connecting to a live legacy system, navigating a COBOL program, using the AI assistant to explain and refactor code, compiling from the browser, and downloading the result. Everything in a standard web browser. No specialized setup on the developer's machine.

Watch OL Code by OpenLegacy overview here.

Get Started with OL Code

OL Code is free. No license required for the core IDE. It installs as a single JAR (Java 17+) or Docker image, and connects to your Mainframe or AS/400 with credentials and TCP/IP access.

Everything you need to get started is at community.openlegacy.com/ol-code. Download the JAR, pull the Docker image, and have it running in under an hour.

For questions, context from other teams going through modernization, and deeper discussion of OL Code capabilities, the OpenLegacy Community Forum has a dedicated thread: Modernizing Legacy Development at Scale: Introducing OL Code.

AI can modernize your COBOL. OL Code makes sure your team can actually reach it.