defensive-invariants

defensive-invariants is a cursor rule for Cursor from ctxr-dev/llm-wiki-memory. It costs 87 tokens per session, scanned A, original, MIT.

A safety rule about keeping defensive checks in place unless their removal is justified by the project’s required evidence.

In plain words
What is it for?
It guides code reviews and maintenance decisions about whether a defensive validation or invariant check may be removed.
Why use it?
It reduces the risk of deleting a check that protects against unexpected or future invalid states.

Cursor rule for Cursor

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.

agentmods
npx agentmods add rules/ctxr-dev/llm-wiki-memory/defensive-invariants
Clone the repo
git clone --depth 1 https://github.com/ctxr-dev/llm-wiki-memory

Made for: Cursor.

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 defensive-invariants

README.md
[![agentmods](https://agentmods.dev/badge/rules/ctxr-dev/llm-wiki-memory/defensive-invariants.svg)](https://agentmods.dev/rules/ctxr-dev/llm-wiki-memory/defensive-invariants)
Your own site
<a href="https://agentmods.dev/rules/ctxr-dev/llm-wiki-memory/defensive-invariants"><img src="https://agentmods.dev/badge/rules/ctxr-dev/llm-wiki-memory/defensive-invariants.svg" alt="Measured on agentmods" height="20"></a>
Per session 87 This file is loaded in full into every session.
When invoked 87 The same file — it is already loaded in full.
Security scan A 0 findings. Scan, not verified.
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 $0.00087 $0.00087
Opus 5 $0.00044 $0.00044
Sonnet 5 $0.00017 $0.00017
Haiku 4.5 $0.00009 $0.00009

Measured 4d ago against content hash e9075ddfe78a, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

defensive-invariants 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 4d 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.

.cursor/rules/defensive-invariants.mdc · 9 lines

What it actually says

Follow the canonical rule (edit that file, never this shadow):

@.agents/rules/defensive-invariants.md

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. 4d ago First seen · 9 lines · 87 tokens per session scan A e9075ddfe78a

Subscribe to this mod's changes

defensive-invariants is a cursor rule published in the GitHub repository ctxr-dev/llm-wiki-memory (130 stars, last pushed 6d ago), licensed MIT. It adds 87 tokens to every session, 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 2026-08-30.