# Notice — Plumbing Stress Index (PSI) Rulebook v1.2

**Date:** 16 October 2026 · **Administrator:** Radius Technology Systems

## What changes

Rulebook v1.2 was adopted on 16 October 2026 and applies from the print of **17 October 2026** (the 16 October print was already struck under v1.1). The change opens a **new
segment** of the PSI series. No v1.1 print is restated, and the series carries a
segment marker: do not compare levels across the break.

## Why

On 15 September 2026 the administrator decided to score stablecoin reserves the way an
auditor scores a SEC Rule 2a-7 government money market fund. v1.2 implements that rule:

1. **Attested figures, not models.** Every reserve share now comes from the issuer's latest
   independent attestation (USDC: Deloitte, as of 31 July 2026; USDT: BDO, as of 30 June 2026),
   cited line by line in the registry.
2. **Unnamed custody is unverified custody.** A custodian no primary source names now
   scores at full severity, the same as cash at an unnamed bank. The USDT "Cantor
   Fitzgerald" custody edge is removed: Tether names Cantor only for USA₮, not USDT.
3. **Asset quality.** Reserves outside 2a-7 eligible assets (cash, Treasuries,
   Treasury repo) now count as stress. About 25% of USDT's reserves are gold, secured
   loans, bitcoin, equities and other investments.

## Effect on adoption day

Reserve risk moves from 40.7 to 65.4, and PSI from about 17.9 to about 22.9. PSI remains
in the *calm* band. The increase reflects how the reserves are scored, not a change in
the reserves themselves.

Rulebook: [`/methodology`](/methodology) — section P2.1 and the P-Changelog.