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/catwillgh/mainframe/pi-engineernpx skills add CATWILLgh/MAINFRAME --skill pi-engineergit clone --depth 1 https://github.com/CATWILLgh/MAINFRAMEWhat 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 | $0.00073 | $0.00543 |
| Opus 5 | $0.00036 | $0.00271 |
| Sonnet 5 | $0.00015 | $0.00109 |
| Haiku 4.5 | $0.00007 | $0.00054 |
Grade A, and why
pi-engineer 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.
Copies of this mod
1 near-identical copy found in the catalogue:
- mainframe-pi-engineer — 88% identical, 27 lines differ
What it actually says
Pi engineer
Keep architecture, user communication, final review, and the commit in this primary session. Pi implements one already-agreed block in the current Git worktree and returns structured evidence; its internal verifier is a quality gate, not final acceptance.
For a new block, write a short JSON request inside
.agents/runtime/pi/requests/ with this exact shape:
{
"schemaVersion": 1,
"goal": "One observable result",
"writePaths": ["path/or/narrow-glob"],
"excludePaths": [],
"invariants": ["Behavior that must remain true"],
"acceptance": ["Concrete result that can be checked"],
"forbiddenFutureStages": ["Later work that must not begin"],
"checks": [{"argv": ["exact-executable", "arg"], "timeoutMs": 60000}]
}
Keep lists only as detailed as the block requires. Checks must be exact argv,
not inline shell, and cannot invoke Git. Then run mainframe-pi engineer --mode new --request <project-relative-request.json>.
For a correction to the same active block, write a correction packet under the
same runtime directory and run mainframe-pi engineer --mode resume --feedback <project-relative-feedback.json>. The packet contains exactly instructions,
missingEvidence, and failedCheckIds arrays. Omit --feedback only when
resuming interrupted work without new review findings.
Let a run finish unless it reports a real block. Inspect the returned status,
changed paths, checks, acceptance evidence, and verifier verdict against the
actual diff. ready-for-architect-review means only that Pi's internal pass is
complete. If review finds an in-scope defect, send one precise resume
correction. If accepted, create the Conventional Commit here, limited to
accepted task paths and preserving unrelated dirty or staged work. The next
new block reconciles that commit and compacts the persistent Pi session.
Do not copy Pi's internal pipeline into the prompt, pass profile/config/project overrides, ask Pi to commit, or treat its verifier as user acceptance.
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 · 50 lines · 73 tokens per session scan A f74f3ffeb8c1
pi-engineer is a skill published in the GitHub repository CATWILLgh/MAINFRAME (2 stars, last pushed 11d ago), licensed MIT. It adds 73 tokens to every session and 543 once invoked, about $0.0004 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 2026-08-31.
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