same-source-twice

same-source-twice is a skill for Claude Code, Codex from arunveersingh/ai. It costs 93 tokens per session (785 once invoked), scanned A, original, Apache-2.0.

A research method for checking whether sources really come from different original systems or pages, rather than repeating the same information.

In plain words
What is it for?
Use it to trace claims to their origins and confirm critical claims with an independent source, including output from the real system when possible.
Why use it?
Several documents can copy one incorrect source, so agreement between them is not independent confirmation. This matters especially for premises involving money, data destinations, or deletion.

Skill for Claude CodeCodex

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

Good fit Use it to trace claims to their origins and confirm critical claims with an independent source, including output from the real system when possible.

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Install with agentmods
npx agentmods add skills/arunveersingh/ai/day-12-same-source-twice
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 arunveersingh/ai --skill day-12-same-source-twice
Clone the repo
git clone --depth 1 https://github.com/arunveersingh/ai

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 same-source-twice

README.md
[![agentmods](https://agentmods.dev/badge/skills/arunveersingh/ai/day-12-same-source-twice/github.svg)](https://agentmods.dev/skills/arunveersingh/ai/day-12-same-source-twice)
Your own site
<a href="https://agentmods.dev/skills/arunveersingh/ai/day-12-same-source-twice"><img src="https://agentmods.dev/badge/skills/arunveersingh/ai/day-12-same-source-twice/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 same-source-twice

Your own site · 80×15
<a href="https://agentmods.dev/skills/arunveersingh/ai/day-12-same-source-twice"><img src="https://agentmods.dev/badge/skills/arunveersingh/ai/day-12-same-source-twice.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 93 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 785 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.
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 $0.00093 $0.00785
Opus 5.5 $0.00037 $0.00314
Sonnet 5.5 $0.00019 $0.00157
Haiku 4.5 $0.00009 $0.00078

Measured 11d ago against content hash 7b4b525d8374, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

same-source-twice 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 11d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (corroborate.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

courses/make-ai-fail-safely/practice/day-12-same-source-twice/SKILL.md · 47 lines

How it starts

The opening of the file, as written. The whole thing — 47 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Same source twice

A payout integration assumes "amount is in minor units, divide by 100". Three sources agree: the payouts page ("e.g. 1000 = 10.00 EUR"), the SDK docstring, the integration guide. All three copy the payouts page; the Currencies page listing zero-decimal currencies was never cited. When JPY is enabled later, 5,000 yen arrives as amount: 5000 and is booked as 50 yen, and every JPY payout is booked at 1/100.

Copied is not corroborated. Same origin, one vote; and one vote must come from the real system.

Part A — Ask (paste after your ticket)

For each premise, list its sources as: ref | origin | doc or system.
Origin is the page or system the text or value first came from, not where you read it.
Mark critical any premise that decides an amount, a destination or a deletion.
A critical premise is confirmed only with two different origins, one of them system output
(a sandbox call, a recorded response or a query) on the case most likely to differ.
If the system can't be checked safely, say so and name who must accept the risk.
Until then, don't start tasks that need it. Reply:
BLOCKED: critical premise has one origin | found: <premise, sources, origin> | need: <the system check>

In an orchestrated flow (spec → plan → tasks → implement): add origin and doc/system columns to the premise table in the plan; mark critical premises in the spec; make the system check a small first task and save its output next to the plan.

Part B — Check (you do this)

corroborate.py has no dependencies. Put the premises in JSON (see plan.example.json):

python3 corroborate.py plan.json       # every premise
python3 corroborate.py plan.json P1    # one; exit 0 passes, 1 blocked or unknown id

On the example: P1: BLOCKED: critical premise has one origin | found: P1: 3 source(s), origin: payouts page | need: a source with a different origin. Add one system source (a sandbox JPY payout) and P1 passes. If the system can't be checked safely, "risk_accepted_by": "<name>" records who accepted the risk.

Read the full file on GitHub · 47 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 11d ago First seen · 47 lines · 93 tokens per session scan A 7b4b525d8374

Subscribe to this mod's changes

same-source-twice is a skill published in the GitHub repository arunveersingh/ai (3 stars, last pushed 3d ago), licensed Apache-2.0. It adds 93 tokens to every session and 785 once invoked, about $0.0004 per session on Opus 5.5. 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 2026-10-14.

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