system-one-design

system-one-design is a skill for Claude Code, Codex from brcampidelli/chimera-agent. It costs 44 tokens per session (1,123 once invoked), scanned A, original, Apache-2.0.

A guide for turning model questions into typed decisions, such as yes-or-no choices, named options, or ordered scores. It covers how to ask one condition at a time and interpret the returned answer safely.

In plain words
What is it for?
Use it when building an agent workflow that asks models to classify items, choose among options, or assign levels and then reads the result in code.
Why use it?
It reduces unclear questions and prevents a model's score from silently approving, stopping, or skipping work on its own.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it when building an agent workflow that asks models to classify items, choose among options, or assign levels and then reads the result in code.

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Install with agentmods
npx agentmods add skills/brcampidelli/chimera-agent/system-one-design
Install

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.

Any agent
npx skills add brcampidelli/chimera-agent --skill system-one-design
Clone the repo
git clone --depth 1 https://github.com/brcampidelli/chimera-agent

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for system-one-design

README.md
[![agentmods](https://agentmods.dev/badge/skills/brcampidelli/chimera-agent/system-one-design/github.svg)](https://agentmods.dev/skills/brcampidelli/chimera-agent/system-one-design)
Your own site
<a href="https://agentmods.dev/skills/brcampidelli/chimera-agent/system-one-design"><img src="https://agentmods.dev/badge/skills/brcampidelli/chimera-agent/system-one-design/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.

agentmods 80×15 button for system-one-design

Your own site · 80×15
<a href="https://agentmods.dev/skills/brcampidelli/chimera-agent/system-one-design"><img src="https://agentmods.dev/badge/skills/brcampidelli/chimera-agent/system-one-design.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 44 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,123 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00044 $0.01123
Opus 5.5 $0.00018 $0.00449
Sonnet 5.5 $0.00009 $0.00225
Haiku 4.5 $0.00004 $0.00112

Measured 21d ago against content hash 99848d8b85c7, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

system-one-design 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 21d 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.

skills/system-one-design/SKILL.md · 82 lines

How it starts

The opening of the file, as written. The whole thing — 82 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Trigger

A step asks a model a question whose answer is one of a few known values — yes or no, one of five labels, a level from low to high — and then reads that value out of the prose it wrote. Or the same question is asked of hundreds of items. That is a typed decision wearing a chat costume.

Do

  1. Ask it as a typed question (chimera decide, POST /api/decide, or the decide tool): noul for yes/no, choice for one of a set, score for ordered levels. A probability comes back.
  2. One condition per question. "Is it an error and from the database?" is two questions; ask both and combine the answers in code, where the rule is visible.
  3. Give options names that do not carry the verdict (not "yes", "safe", "pass") and put the meaning in the criteria. A catch-all option ("other") is unreliable in both directions — measure it on your items, give it a narrow criterion, or replace it with a noul per candidate when rejection matters. Make the options' first words differ: a local model reads the label from its first token, so coding and coding_agent can never be told apart (24 of 231 public JevBench items went unread this way). On the catch-all, measured on 1,000 commit subjects: a broad "other" took 78% of the items that belonged to a named option and a narrow one 58%; leaving it out lifted named-class F1 from 0.24 to 0.43, at the price that items truly outside the set land on a named option. The catch-all fails in either direction, by model and task: here it absorbed items it should not have, while a hosted decision model picked "None/Other" for only 7% of items whose right answer was missing (arXiv 2609.39496). When rejecting matters, ask a noul per candidate (99% rejected there) or set a threshold on the catch-all's probability from labelled examples (79% rejected, 97% of answerable items kept).
  4. Show the model the thing being judged, alone: not the tool output around it, not a sentence that argues for an answer.
  5. Pick any threshold from labelled examples, never from a guess, and keep the number beside the decision it fed.
  6. Keep arithmetic, dates and counts in code: compute the fact, put it in the state, and ask about it. A decision model reads; it does not calculate (on JevBench's hard tier the local model got 1 of 15 date-and-number items right).

Read the full file on GitHub · 82 lines

Changes

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.

  1. 21d ago Changed · +6 lines 99848d8b85c7
  2. 1mo ago Changed · +14 lines 347bfae9f826
  3. 1mo ago First seen · 62 lines · 44 tokens per session scan A 25fc5a6b7f92

Subscribe to this mod's changes

system-one-design is a skill published in the GitHub repository brcampidelli/chimera-agent (29 stars, last pushed today), licensed Apache-2.0. It adds 44 tokens to every session and 1,123 once invoked, about $0.0002 per session on Opus 5.5. 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 2026-09-24.

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