I’ve been looking through your BTSL playground source code. To make this work seamlessly with the Blind Relay reference implementation (Signing Room), it would be great if the BTSL parser and validator were available as a standalone, versioned NPM package.

If we had an @btsl/validator package that was environment-agnostic (no internal fetch calls to Blockstream, just pure PSBT/Schema validation and minimal dependencies), I could potentially integrate it directly into the Signing Room client. This would allow 'Signing Room' to automatically detect an attached schema, run the ASSERT logic locally, and provide the user with a 'Verified by BTSL' green-check before they sign.

The STATE_SYNC payload could be modified to something like this to pass a schema and type:

{

On Thursday, 26 March 2026 at 14:21:41 UTC Thomas Suau wrote:

Hello,
The transport layer problem is well addressed here. The complementary piece — ensuring signers can independently validate transaction invariants before signing, regardless of how the PSBT was relayed — is what I've been exploring with BTSL: https://delvingbitcoin.org/t/btsl-bitcoin-transaction-schema-language-a-declarative-validation-schema-for-psbt-workflows/2338

Best regards,
Thomas Suau

Le mercredi 25 mars 2026 à 13:21:39 UTC+1, Sean Carlin a écrit :
Hi everyone,

I'd like to propose a new BIP for real-time, trust-minimized coordination of multi-signature PSBTs.

The Problem
Coordinating N-of-M Bitcoin transactions currently forces users into a binary choice:
- Manual out-of-band transfers (USB drives, secure messengers) that preserve privacy but introduce high friction and error risk, or
- Stateful coordination servers that offer good UX but act as privacy honeypots, logging metadata, signer relationships, and often storing PSBTs on disk.

The Proposal: Blind Relay
This BIP introduces a "Blind Relay" - an ephemeral, stateless, zero-knowledge WebSocket relay. All payloads are encrypted client-side with AES-GCM-256, with decryption keys held exclusively in client-side URL fragments (never sent to the server). The relay operates entirely in RAM with a strict 24-hour TTL and self-destructs upon completion, providing real-time coordination without persistent metadata or disk storage.

A reference implementation has been running in production for three months, successfully facilitating real multisig ceremonies.

Links
- BIP Draft: https://github.com/scarlin90/bip-stateless-psbt-coordination/blob/main/bip-draft.md
- Source Code: https://github.com/scarlin90/signingroom
- Live Client: https://signingroom.io
- Related Research Paper: https://arxiv.org/abs/2601.17875

I look forward to your technical feedback - especially on the specification, security model, edge cases, and any suggested improvements.

Best regards,
Sean Carlin