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 skills add austin-starks/Public-Portfolio-Challenge --skill engine-sanitygit clone --depth 1 https://github.com/austin-starks/Public-Portfolio-ChallengeWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/austin-starks/public-portfolio-challenge/engine-sanity)<a href="https://agentmods.dev/skills/austin-starks/public-portfolio-challenge/engine-sanity"><img src="https://agentmods.dev/badge/skills/austin-starks/public-portfolio-challenge/engine-sanity/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/austin-starks/public-portfolio-challenge/engine-sanity"><img src="https://agentmods.dev/badge/skills/austin-starks/public-portfolio-challenge/engine-sanity.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
What 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 5.1 | $0.00094 | $0.00705 |
| Opus 5 | $0.00047 | $0.00352 |
| Sonnet 5 | $0.00019 | $0.00141 |
| Haiku 4.5 | $0.00009 | $0.00071 |
Grade A, and why
engine-sanity 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 11d 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.
How it starts
The opening of the file, as written. The whole thing — 53 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Engine Sanity Checks (Stage S0)
MANDATORY; blocks everything. Four contract checks that prove the certification engine is trustworthy before any design work. Each has a STOP-and-report failure mode — a failure here means the engine itself is broken (bug-protocol), and no downstream number can be trusted. These S0 runs (and S1 baseline scoring) explicitly DO NOT COUNT toward the certification-body minimum — they are contract checks and benchmarks, not candidate certifications.
The four checks
-
Walk-forward sweep smoke.
create_portfolioa trivial book (e.g.SPY > SMA50). Runrun_walk_forward_studywithmode:"validation",fold_count:2,engine_kind:"sweep", onegene_intent× 3 values,certification:false. It must start and complete with per-fold OOS + aggregate. Proves: the certification engine actually runs end-to-end. -
Window fidelity (one fold). Backtest the materialized fold winner on its validation and OOS windows; the fold's
validationStatistics/oosStatisticsmust match standalone backtests within rounding. Confirm disjointness: train∩validation, train∩OOS, validation∩OOS all empty, and OOS starts after validation ends. Proves: the walk-forward windowing isn't leaking. -
Persistence.
get_walk_forward_study_resultsreturns a realselectedChatPortfolioIdfor every completed fold. Proves: fold winners materialize as real objects you can inspect/deploy. -
Dead-name handling. Tiny 2022-window backtest on the full universe including a name not yet listed then (e.g. SNDK). Pass: the name is absent, or appears in a not-yet-listed reject list with no fabricated price/indicator values. Fail: the engine errors, or returns any non-null reading for a name that didn't trade. Proves: the engine doesn't fabricate data on not-yet-listed names.
On failure
Any failed S0 check → STOP, file the bug-protocol hand-off doc, and do not proceed to design work. A broken engine invalidates everything downstream; there is no point certifying strategies on it.
What ships with it
3 files 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.
- 11d ago First seen · 53 lines · 94 tokens per session scan A 14936357e501
engine-sanity is a skill published in the GitHub repository austin-starks/Public-Portfolio-Challenge (44 stars, last pushed 3d ago), licensed MIT. It adds 94 tokens to every session and 705 once invoked, about $0.0005 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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