sep41-token-safety

sep41-token-safety is a skill for Claude Code, Codex from PlamenTSV/plamen. It costs 41 tokens per session (2,312 once invoked), scanned A, original, MIT.

A security-audit guide for SEP-41 tokens, Soroban’s token interface standard, similar to ERC-20. It focuses on transfers, balances, allowances, and Stellar Asset Contract bridges.

In plain words
What is it for?
Reviewing `approve`, `transfer`, `transfer_from`, allowance, balance, and asset-bridge logic.
Why use it?
It helps uncover approval races, expiring allowance storage, and accounting differences between Stellar assets and Soroban tokens.

Skill for Claude CodeCodex

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

Good fit Reviewing approve, transfer, transfer_from, allowance, balance, and asset-bridge logic.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/plamentsv/plamen/sep41-token-safety
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 sep41-token-safety
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 sep41-token-safety

README.md
[![agentmods](https://agentmods.dev/badge/skills/plamentsv/plamen/sep41-token-safety/github.svg)](https://agentmods.dev/skills/plamentsv/plamen/sep41-token-safety)
Your own site
<a href="https://agentmods.dev/skills/plamentsv/plamen/sep41-token-safety"><img src="https://agentmods.dev/badge/skills/plamentsv/plamen/sep41-token-safety/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 sep41-token-safety

Your own site · 80×15
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Per session 41 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,312 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 warn 7 Sept 2026
SkillSpector: 1 finding, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium Excessive Agency · line 17
    Skill enables autonomous high-impact decisions without human-in-the-loop verification. Critical operations (destructive commands, financial transactions, data deletion) should require explicit user confirmation.
    Fix: Add human-in-the-loop confirmation for destructive, irreversible, or high-impact operations. Never auto-execute commands that modify files, send data, or alter system state.
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 $0.00041 $0.02312
Opus 5 $0.00020 $0.01156
Sonnet 5 $0.00008 $0.00462
Haiku 4.5 $0.00004 $0.00231

Measured 7d ago against content hash 03416e966a09, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

sep41-token-safety 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 7d 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/soroban/sep41-token-safety/SKILL.md · 147 lines

How it starts

The opening of the file, as written. The whole thing — 147 lines — stays where its author put it; the contents beside it link to each section on GitHub.

SEP41_TOKEN_SAFETY Skill (Soroban)

Trigger Pattern: SEP-41 token patterns detected (approve/transfer/transfer_from/allowance/balance) Inject Into: Breadth agents, depth-token-flow, depth-edge-case Finding prefix: [ST-N] Rules referenced: R4, R5, R10, R11, R13, R15

SEP-41 is Soroban's token interface standard, analogous to ERC-20. It introduces Soroban-specific behaviors that differ from ERC-20: allowances use Temporary storage with expiration_ledger, the approve function can be front-run similarly to ERC-20, and the Stellar Asset Contract (SAC) bridges Stellar classic assets into Soroban with additional accounting complexity.

1. Approve Race Condition

The approve(from, spender, amount, expiration_ledger) function overwrites the current allowance without checking the existing value. This is the ERC-20 approve race condition, present identically in SEP-41:

Token Contract approve Guarded? Guard Type Effective?
{contract} YES/NO require!(current == 0) / none YES/NO

Attack sequence:

  1. Owner approves spender for 100 tokens
  2. Owner submits new approval for 50 tokens
  3. Spender front-runs the new approval and spends the 100-token allowance
  4. New 50-token approval is set
  5. Spender spends 50 more tokens — net: 150 tokens spent, 50 intended

Soroban-specific note: Soroban does not have a traditional mempool — transaction ordering is determined by validators, not fee-based priority. However, multi-operation transactions and DEX routing can create ordering dependencies. The race condition is lower likelihood than on EVM but the vulnerability exists.

Check for:

  • Does approve allow setting non-zero over non-zero without an intermediate zero-set step?
  • Does the protocol documentation warn users about the race condition?
  • Are there any off-chain tools (like increaseAllowance / decreaseAllowance equivalents) to safely adjust allowances?

Read the full file on GitHub · 147 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. 7d ago First seen · 147 lines · 41 tokens per session scan A 03416e966a09

Subscribe to this mod's changes

sep41-token-safety is a skill published in the GitHub repository PlamenTSV/plamen (295 stars, last pushed 2d ago), licensed MIT. It adds 41 tokens to every session and 2,312 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 2026-09-03.

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