cross-environment-semantic-drift

cross-environment-semantic-drift is a skill for Claude Code, Codex from PlamenTSV/plamen. It costs 43 tokens per session (3,803 once invoked), scanned A, original, MIT.

A review guide for finding bugs where software crosses between execution environments, such as an Ethereum-compatible system running on another platform. It covers mismatched assumptions, integer sizes, precompiled operations, and differences in how environments interpret the same behavior.

In plain words
What is it for?
It is for auditing EVM forks, layer-2 systems, EVM-compatible runtimes on other platforms, and precompile implementations written in Go, Rust, Solidity, or C++.
Why use it?
Code that imitates Ethereum can behave differently from Ethereum itself at boundaries, especially when values or built-in operations are translated between systems. This guide helps identify those differences before they cause inconsistent results or security problems.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: positional $N argument.

Good fit It is for auditing EVM forks, layer-2 systems, EVM-compatible runtimes on other platforms, and precompile implementations written in Go, Rust, Solidity, or C++.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/plamentsv/plamen/cross-environment-semantic-drift
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 PlamenTSV/plamen --skill cross-environment-semantic-drift
Clone the repo
git clone --depth 1 https://github.com/PlamenTSV/plamen

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 cross-environment-semantic-drift

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 cross-environment-semantic-drift

Your own site · 80×15
<a href="https://agentmods.dev/skills/plamentsv/plamen/cross-environment-semantic-drift"><img src="https://agentmods.dev/badge/skills/plamentsv/plamen/cross-environment-semantic-drift.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 43 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,803 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. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
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 $0.00043 $0.03803
Opus 5 $0.00022 $0.01902
Sonnet 5 $0.00009 $0.00761
Haiku 4.5 $0.00004 $0.00380

Measured 9d ago against content hash f3ca1d7c659a, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

cross-environment-semantic-drift 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 9d 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.

agents/skills/injectable/l1/cross-environment-semantic-drift/SKILL.md · 213 lines

How it starts

The opening of the file, as written. The whole thing — 213 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Injectable Skill: Cross-Environment Semantic Drift

L1 trigger: L1_PATTERN=true AND (fork of an EVM execution client OR L2-rollup detected OR EVM-on-non-EVM runtime OR precompile implementation in a non-EVM host detected) Inject Into: depth-external or depth-state-trace Language: Go, Rust, Solidity (for precompiles), C++ Finding prefix: [XE-N] Status: v0.1 draft, Round 4 exemplars pending

Orchestrator Decomposition Guide

  • Sections 1, 2: depth-external (boundary enumeration)
  • Section 3: depth-state-trace (semantic diff tracing)
  • Section 4: depth-edge-case (integer width / encoding boundaries)

When This Skill Activates

Recon detects ONE of the following:

  1. Target is a fork of an EVM execution client (op-geth, op-reth, arbitrum-nitro, base-node)
  2. Target is an L2 rollup that re-implements EVM semantics (Optimism OVM, Arbitrum AVM, early zkEVMs)
  3. Target runs EVM on a non-EVM host (Moonbeam on Polkadot-SDK, Frontier on Substrate, Neon on Solana)
  4. Target implements precompiles that wrap native-host functionality
  5. Target has integer-width boundaries between environments (128-bit Substrate balance vs 256-bit EVM value)

This is the most consequential "new class" skill: the most famous L1 bounties (Saurik's Optimism, pwning.eth's Moonbeam and Polkadot Frontier) are all in this category.

1. Boundary Enumeration

Map every semantic boundary in the target. A boundary is any place where code written against one execution model calls into code written against another.

Boundary types

Type Example Risk
EVM ↔ host chain balance Optimism OVM_ETH wraps native ETH Double-counting, wrong-account credit
EVM ↔ precompile Moonbeam ERC-20 precompile wrapping GLMR Call context confusion, allowance abuse
EVM-256 ↔ host-N 256-bit value to 128-bit host balance Truncation, wraparound
Rollup sequencer ↔ L1 inbox Optimism deposit tx Replay, double-credit
Bridge contract ↔ bridge relay Any canonical bridge Message forging, replay
L2 state root ↔ L1 dispute game Arbitrum, Optimism Invalid state root acceptance

Read the full file on GitHub · 213 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. 9d ago First seen · 213 lines · 43 tokens per session scan A f3ca1d7c659a

Subscribe to this mod's changes

cross-environment-semantic-drift is a skill published in the GitHub repository PlamenTSV/plamen (294 stars, last pushed yesterday), licensed MIT. It adds 43 tokens to every session and 3,803 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 2026-08-30.

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