NiXium: Instructions file for Codex

AGENTS.md

NiXium AGENTS.md is an instructions file for Codex, OpenCode from Arcanyx-org/NiXium. It costs 10,927 tokens per session, scanned B, original, EUPL-1.2.

A set of coding-agent instructions for the NiXium project, including its folder guidance, approval expectations, and use of Nix flakes. A Nix flake is a reproducible way to define software packages and development environments.

In plain words
What is it for?
Use it when planning or changing NiXium, keeping its instruction file current, getting agreement before implementation, and following its flake-parts architecture.
Why use it?
It tells an agent how the project is organized and highlights rules that could otherwise lead to incorrect changes, such as treating it like a standard NixOS project.

Instructions file for CodexOpenCode

Written for Codex and OpenCode: the file is AGENTS.md.

This is Arcanyx-org/NiXium's own configuration. It tells Codex and OpenCode how to work on NiXium itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything NiXium configures →

Reuse

Borrowing it

Nothing to install: this file belongs to Arcanyx-org/NiXium. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/Arcanyx-org/NiXium/experimental/AGENTS.md
Clone the repo
git clone --depth 1 https://github.com/Arcanyx-org/NiXium

Made for: Codex, OpenCode.

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.

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README.md
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Your own site
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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 NiXium AGENTS.md

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Per session 10,927 This file is loaded in full into every session.
When invoked 10,927 The same file — it is already loaded in full.
Security scan B 2 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin unknown 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 $0.10927 $0.10927
Opus 5.5 $0.04371 $0.04371
Sonnet 5.5 $0.02185 $0.02185
Haiku 4.5 $0.01093 $0.01093

Measured 2mo ago against content hash 4ef4028dc554, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade B, and why

NiXium AGENTS.md scanned grade B with 2 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 2mo 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.

Asks for rootmediumPrivilege escalation

A mod that escalates privileges can change anything on the machine, not only the project.

The `kira` user in `src/nixos/users/users/kira/kira.nix` had `"wheel"` in `extraGroups` granting sudo access. Remove `"wheel"` from the list to revoke admin privileges while keeping other groups (docker, dialout).

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

runtimeInputs = [ pkgs.curl ];
AGENTS.md · 942 lines

The source is not reproduced here

Licensed EUPL-1.2

The repository is licensed EUPL-1.2, which this catalogue does not treat as permission to reproduce the file. Read it at the source.

Read it on GitHub

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. 2mo ago First seen · 942 lines · 10,927 tokens per session scan B 4ef4028dc554

Subscribe to this mod's changes

NiXium AGENTS.md is an instructions file published in the GitHub repository Arcanyx-org/NiXium (49 stars, last pushed 3mo ago), licensed EUPL-1.2. It adds 10,927 tokens to every session, about $0.0437 per session on Opus 5.5. A static security scan graded it B with 2 findings (asks for root, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Related

NiXium AGENTS.md compared with instructions from other repositories

NiXium AGENTS.md next to 6 instructions from other repositories
ModTypeStarsLast pushLicenceScanTokensWorks with
NiXium AGENTS.mdArcanyx-org/NiXiumInstructions file493mo agoEUPL-1.2B10,927Codex, OpenCode
vscode buildNext.instructions.mdmicrosoft/vscodeInstructions file195kyesterdayMITA9,719GitHub Copilot
next.js AGENTS.mdvercel/next.jsInstructions file143kyesterdayMITA7,461Codex, OpenCode
langchain AGENTS.mdlangchain-ai/langchainInstructions file149kyesterdayMITA4,680Codex, OpenCode
vscode oss-third-party-notices.instructions.mdmicrosoft/vscodeInstructions file195kyesterdayMITA5,516GitHub Copilot
vscode copilot-instructions.mdmicrosoft/vscodeInstructions file195kyesterdayMITA3,093GitHub Copilot
deepseek-harness AGENTS.mddeepseek-ai/deepseek-harnessInstructions file274k2d agoMITA4,313Codex, OpenCode