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/nrdxp/predicate/lowynpx skills add nrdxp/predicate --skill lowygit clone --depth 1 https://github.com/nrdxp/predicateWhat 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 | $0.00044 | $0.03151 |
| Opus 5 | $0.00022 | $0.01576 |
| Sonnet 5 | $0.00009 | $0.00630 |
| Haiku 4.5 | $0.00004 | $0.00315 |
Grade A, and why
lowy 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.
How it starts
The opening of the file, as written. The whole thing — 158 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Volatility Decomposition Review
Evaluate module boundaries and decomposition decisions using Juval Löwy's volatility-based decomposition framework. The core question: do your boundaries encapsulate axes of change, or do they just group related functionality?
[!NOTE] This workflow is the temporal half of the code-spacetime review pair. It reads code as a world-line — what will pull apart, and when? For the spatial half — what's tangled right now? — see
/hickey. Run both for full coverage. Seeengineering.md§8.1.
Attribution: Adapted from Juval Löwy's Righting Software (2019), building on David Parnas, "On the Criteria to Be Used in Decomposing Systems into Modules" (1972). Workflow structure adapted from Srid Ratnakumar's implementation. See also: Volatility-Based Decomposition (book excerpt).
Core Distinction
Functional decomposition groups code by what it does (UserService, PaymentController, AuthModule). Volatility-based decomposition groups code by what is likely to change — and encapsulates each axis of change behind a stable interface.
"This principle governs the design of all practical systems, from houses, to laptops, to jumbo planes, to your own body. To survive and thrive they all encapsulate the volatility of their constituent components." — Löwy
Löwy's electricity analogy: a house's power supply has enormous volatility (AC/DC, 110v/220v, 50/60Hz, solar/grid/generator, wire gauges). All of it is encapsulated behind a receptacle. Without that encapsulation, you'd need an oscilloscope every time you plugged something in. The receptacle is the stable interface; the volatility behind it can change without affecting consumers.
Functional decomposition maximizes the blast radius of change. When boundaries track functionality rather than volatility, a single change cuts across multiple modules. "Functional decomposition is as diverse as the required functionality across all customers and points in time. The resulting huge diversity in the architecture leads directly to out-of-control complexity." Volatility-based decomposition contains the grenade in the vault.
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 · 158 lines · 44 tokens per session scan A c15ee14d166a
lowy is a skill published in the GitHub repository nrdxp/predicate (10 stars, last pushed 8d ago), licensed MIT. It adds 44 tokens to every session and 3,151 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 2026-08-31.
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