Work on mainframes and COBOL
Hopper is an agentic development environment for the mainframe systems behind banking, payments, insurance, and airlines.
Done with a custom-built or unnamed agent
- What they did
- Hopper is a desktop app that runs on your laptop and connects to z/OS over TN3270, plus optional FTP. You give the agent plain-English prompts. It reads COBOL and JCL, drives ISPF, submits jobs, decodes spool output and VSAM records, and can NEWCOPY into CICS. Read-only actions run immediately. Any change pauses for your approval.
- How it went
- The page claims it turns hours of SDSF triage into one tag, which returns the abend code, failing step and source line. It gives no measured results or benchmarks.
- Worth knowing
- FTP credentials are optional, but without them the datasets and jobs browsers, builds and most agent tools stay disabled. The free Hobby tier needs your own mainframe.
Try it yourself with Claude Code
I have a legacy COBOL program at [path]. Read it and its copybooks, then write a plain-English explanation of what each paragraph or section does, list the data files and fields it touches, and flag any business rules hidden in the code. Finish with a suggested outline for rewriting it in [target language, e.g. Java]. Don't modify any files.
Discussion on HN · May 12, 2026
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