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 agentmods add skills/openhands/extensions/mainframe-removalnpx skills add OpenHands/extensions --skill mainframe-removalgit clone --depth 1 https://github.com/OpenHands/extensionsWhat 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 | $0.00033 | $0.00461 |
| Opus 5 | $0.00016 | $0.00230 |
| Sonnet 5 | $0.00007 | $0.00092 |
| Haiku 4.5 | $0.00003 | $0.00046 |
Grade A, and why
mainframe-removal 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 2d 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.
What it actually says
Apply the transformations from a transformation guide to convert mainframe-specific COBOL to standard COBOL.
Prerequisite: A transformation guide must exist (see cobol-mainframe-planning skill).
Transformation Requirements
Data Operations
- Replace each CICS/VSAM construct with its standard COBOL equivalent per the plan
- Add FILE STATUS checks after EVERY file operation:
- Check for success (00) before proceeding
- Handle "not found" (23) distinctly from I/O errors (3x)
- Handle "file not exists" (35) at OPEN time
- Add explicit CLOSE statements in all code paths (including error paths)
UI/Terminal Operations (BMS maps, SEND/RECEIVE)
- Replace with simple stubs or ACCEPT/DISPLAY statements
- Do NOT spend time replicating screen layouts
- Focus on preserving data flow, not UI fidelity
Error Handling
- Replace CICS RESP/RESP2 checks with equivalent FILE STATUS logic
- Replace HANDLE CONDITION with explicit status checking after operations
- Ensure error paths don't leave files open
See references/cics-transformation-examples.md for before/after code examples.
Verification
After transformation:
- Code MUST compile without errors
- Test with valid input → should execute core business logic
- Test with missing/invalid files → should fail gracefully, not crash
Preserve
- All original business logic
- Data transformations and calculations
- Validation rules
Checklist
- All EXEC CICS commands replaced
- FILE STATUS declared for all files
- FILE STATUS checked after every I/O operation
- CLOSE statements in all code paths
- Code compiles successfully
- Basic test execution passes
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 2d ago First seen · 63 lines · 33 tokens per session scan A bf0c95e28074
mainframe-removal is a skill published in the GitHub repository OpenHands/extensions (137 stars, last pushed 4d ago), licensed MIT. It adds 33 tokens to every session and 461 once invoked, about $0.0002 per session on Opus 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 2026-08-30.
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