@bsv/btms-permission-module

The core permission module for BTMS token operations. Framework-agnostic with no UI dependencies.

BSV Desktop and BSV Browser show a spend authorization modal whenever BSV is spent. For a BTMS token output the raw satoshi value is typically 1 sat — not the token's actual denomination. This module gives the wallet enough context to show the correct value to the user and gate authorization appropriately. A USD stablecoin issuer, for example, ships a module that causes the modal to display "$1.00 USD" rather than "1 satoshi."

@bsv/btms-permission-module implements the BRC-98/99 permission hooks interface to intercept BTMS token spend and burn operations, prompt users via a callback, and enforce authorization decisions. Works with any UI framework (React, Vue, Angular, vanilla JS, or no UI at all).

Install

npm install @bsv/btms-permission-module

Quick start

import { createBtmsModule } from '@bsv/btms-permission-module'
import { createWallet } from '@bsv/simple'

const wallet = await createWallet()

const requestTokenAccess = async (app: string, message: string): Promise<boolean> => {
  const details = JSON.parse(message)
  
  const approved = confirm(
    `${app} wants to ${details.operation} ${details.sendAmount || details.burnAmount} of "${details.tokenName}"`
  )
  
  return approved
}

const basicTokenModule = createBtmsModule({
  wallet,
  promptHandler: requestTokenAccess
})

What it provides

• Permission module — BasicTokenModule implementing BRC-98/99 canPerform() and promptUser() hooks
• Factory function — createBtmsModule() for convenient BTMS + module initialization
• Async prompting — PermissionPromptHandler callback pattern for custom UI integration
• JSON message parsing — Standard schema with token details (assetId, operation, amounts, recipient)
• Framework agnostic — No UI dependencies; you control prompt display (modal, alert, web component, etc.)

Common patterns

Simple prompt with confirm dialog (vanilla JS)

import { createBtmsModule } from '@bsv/btms-permission-module'
import { createWallet } from '@bsv/simple'

const wallet = await createWallet()

const requestTokenAccess = async (app: string, message: string): Promise<boolean> => {
  const details = JSON.parse(message)
  
  const approved = confirm(
    `${app} wants to ${details.operation} ${details.sendAmount || details.burnAmount} of "${details.tokenName}"`
  )
  
  return approved
}

const basicTokenModule = createBtmsModule({
  wallet,
  promptHandler: requestTokenAccess
})

Deny-all for programmatic use (no UI needed)

import { createBtmsModule } from '@bsv/btms-permission-module'

// Create module with no prompt handler — all requests denied
const module = createBtmsModule({
  wallet,
  // No promptHandler → defaults to deny all
})

// Useful for server-side or automated workflows

Register with wallet permissions manager

import { WalletPermissionsManager } from '@bsv/wallet-toolbox'
import { createBtmsModule } from '@bsv/btms-permission-module'

const tokenModule = createBtmsModule({
  wallet,
  promptHandler: myPromptHandler
})

const permissionsManager = new WalletPermissionsManager(wallet, appOrigin, {
  permissionModules: {
    btms: tokenModule  // Register under 'btms' key
  }
})

// Now when app tries to spend BTMS tokens, permission system will:
// 1. Check if app has permission for 'btms' protocol
// 2. Call module's promptUser() if permission not cached
// 3. Ask user via your prompt handler
// 4. Cache decision for session

Key concepts

• BRC-98/99 Hooks — Standard permission module interface. Wallets invoke hooks when apps request special operations.
• Permission Caching — Wallet-toolbox's WalletPermissionsManager caches yes/no decisions per (app, protocol) for the session.
• Framework Agnostic — Module is pure TypeScript with no UI dependencies. You control how prompts appear.
• JSON Message Format — Token details are serialized as JSON: { tokenName?, assetId, sendAmount?, burnAmount?, recipientKey?, operation: 'spend' | 'burn' }
• Async Prompt — Handler returns a Promise so you can show UI, wait for user input, then resolve with decision.

When to use this

• You're building a wallet that integrates BTMS token operations
• You need fine-grained permission control over token spending
• You want users to explicitly approve token operations
• You're using @bsv/wallet-toolbox and integrating BTMS

When NOT to use this

• Use @bsv/btms directly if you don't need permission control
• Use @bsv/wallet-toolbox permission system without BTMS if tokens aren't involved

Spec conformance

• BRC-98/99 — Permission module interface (canPerform() and promptUser())
• BRC-100 — Uses standard wallet interface for token validation
• BTMS — Understands BTMS token operations (spend, burn)

Common pitfalls

JSON parse errors — If the message format is wrong, JSON.parse() will throw. Always wrap in try/catch in production handlers.

Async handler blocking — If your prompt handler takes too long, the wallet operation times out. Keep handlers responsive.

Promise never resolving — If your handler never calls resolve(), the wallet operation hangs. Always ensure resolve/reject is called.

Handler called multiple times — For a single token send, handler may be called once per output. Batch prompts if possible in your UI.

No token name available — If asset hasn't been discovered yet, tokenName may be undefined. Use assetId as fallback for display.

Related packages

• @bsv/wallet-toolbox — Wallet that hosts the permission manager
• @bsv/btms — Token protocol that triggers permission checks
• @bsv/sdk — Cryptographic and wallet interface types

Reference

• API reference (TypeDoc)
• Source on GitHub
• npm