no-cfg-not-verus-keep-ghost

no-cfg-not-verus-keep-ghost is a cursor rule for Cursor from briangmilnes/APAS-VERUS. It costs 577 tokens per session, scanned A, original, MIT.

A Verus coding rule that forbids verus_keep_ghost gates and duplicate implementations in lib.rs.

In plain words
What is it for?
Use it when structuring verified Rust code: keep the implementation and specifications together inside verus! blocks.
Why use it?
Duplicate or conditional versions of the same function can drift apart and create unnecessary maintenance work.

Cursor rule for Cursor

Written for Cursor: installed under .cursor/.

Good fit Use it when structuring verified Rust code: keep the implementation and specifications together inside verus! blocks.

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Install with agentmods
npx agentmods add rules/briangmilnes/apas-verus/no-cfg-not-verus-keep-ghost
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.

Clone the repo
git clone --depth 1 https://github.com/briangmilnes/APAS-VERUS

Made for: Cursor.

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README.md
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<a href="https://agentmods.dev/rules/briangmilnes/apas-verus/no-cfg-not-verus-keep-ghost"><img src="https://agentmods.dev/badge/rules/briangmilnes/apas-verus/no-cfg-not-verus-keep-ghost.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 577 This file is loaded in full into every session.
When invoked 577 The same file — it is already loaded in full.
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 $0.00577 $0.00577
Opus 5 $0.00289 $0.00289
Sonnet 5 $0.00115 $0.00115
Haiku 4.5 $0.00058 $0.00058

Measured 8d ago against content hash 89bccdbf6c0c, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

no-cfg-not-verus-keep-ghost 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 8d 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/verus/no-cfg-not-verus-keep-ghost.mdc · 48 lines

How it starts

The opening of the file, as written. The whole thing — 48 lines — stays where its author put it; the contents beside it link to each section on GitHub.

No verus_keep_ghost Antipatterns

There must be no use of verus_keep_ghost in lib.rs. Period.

Antipattern 1: Duplicate function implementations

NEVER create #[cfg(not(verus_keep_ghost))] duplicate implementations of functions that already exist inside verus! {} blocks.

This is an old antipattern from before the codebase was fully verusified. It duplicated every function — once inside verus! {} with specs, and once outside with #[cfg(not(verus_keep_ghost))] for cargo test compatibility.

Why it's wrong

  • The duplicate drifts out of sync with the verified version
  • It doubles maintenance burden
  • It's no longer needed — the verusified code compiles and runs under both Verus and cargo

What to do instead

  • Put the implementation inside verus! {} with its specs
  • That's it. No duplicate needed.

Antipattern 2: Nightly feature gates

NEVER add #![cfg_attr(verus_keep_ghost, feature(...))] to lib.rs.

Lines like #![cfg_attr(verus_keep_ghost, feature(sized_hierarchy))] are cargo-cult copies from vstd's own vstd.rs. vstd needs nightly features for deep Rust intrinsics work. User crates do not — Verus links vstd as a precompiled dependency.

Antipattern 3: Module gating in lib.rs

NEVER use verus_keep_ghost or not(verus_keep_ghost) to conditionally compile module blocks in lib.rs. This includes:

  • #[cfg(all(..., not(verus_keep_ghost)))] pub mod ChapNN { ... } — hiding a chapter from Verus
  • Split declarations — two pub mod ChapNN blocks, one gated verus_keep_ghost, one not(verus_keep_ghost), with different file lists

If a chapter doesn't verify, that's the project's current state (PBOGH). Every chapter gets one unconditional pub mod ChapNN block containing all its files. Verus reports errors on unverified code until it's fixed.

If you see it

If you encounter any of these antipatterns, remove them:

  • Duplicate function bodies: delete the #[cfg(not(verus_keep_ghost))] block.
  • Nightly feature gates: delete the #![cfg_attr(verus_keep_ghost, ...)] line.
  • Module gating: merge split pub mod blocks into one unconditional block with all files.

Read the full file on GitHub · 48 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. 8d ago First seen · 48 lines · 577 tokens per session scan A 89bccdbf6c0c

Subscribe to this mod's changes

no-cfg-not-verus-keep-ghost is a cursor rule published in the GitHub repository briangmilnes/APAS-VERUS (10 stars, last pushed 1mo ago), licensed MIT. It adds 577 tokens to every session, about $0.0029 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 2026-09-03.