Predicates Overview

Predicates are the foundation of Bako Safe vaults. They are smart contracts on Fuel that define the rules for spending assets.

What are Predicates?

In Fuel, a predicate is a stateless program that:

Returns true or false when evaluated
Controls whether a UTXO can be spent
Cannot modify state, only validate conditions

Bako Safe uses predicates to implement multi-signature logic.

How Bako Predicates Work

┌─────────────────────────────────────┐
│           Bako Predicate            │
├─────────────────────────────────────┤
│  Inputs:                            │
│  - Transaction data                 │
│  - Signatures (witnesses)           │
│                                     │
│  Validation:                        │
│  1. Count valid signatures          │
│  2. Verify signers are authorized   │
│  3. Check threshold is met          │
│                                     │
│  Output: true/false                 │
└─────────────────────────────────────┘

Predicate Versions

The SDK includes multiple predicate versions to support different wallet types and features:

Version	Features	Wallet Support
v1	Basic multi-sig	Fuel
v2	WebAuthn support	Fuel, WebAuthn
v3	EVM signatures	Fuel, WebAuthn, EVM

Loading Predicates

Get Latest Version

import { getLatestPredicateVersion } from 'bakosafe';
 
// Get latest for specific wallet type
const version = await getLatestPredicateVersion('fuel');

Load Specific Version

import { loadPredicate } from 'bakosafe';
 
// Load specific version
const predicate = await loadPredicate(provider, 'version-hash');
 
// Load latest compatible
const predicate = await loadPredicate(provider);

Get All Versions

import { getAllPredicateVersions, getAllVersionsDetails } from 'bakosafe';
 
// Get version IDs
const versions = getAllPredicateVersions();
 
// Get detailed info (without bytecode)
const details = getAllVersionsDetails();

Predicate Structure

Each predicate version contains:

interface PredicateVersion {
  id: string;          // Unique identifier (hash)
  name?: string;       // Human-readable name
  description?: string;
  bytes: string;       // Compiled bytecode
  abi: string;         // ABI JSON
  active: boolean;     // Is version active
  walletOrigins: string[];  // Supported wallet types
  deployed: {
    testnet: boolean;
    mainnet: boolean;
  };
}

Version Compatibility

Check if a configuration works with a version:

import { VaultFactory } from 'bakosafe';
 
const isCompatible = VaultFactory.isConfigurationCompatible(
  config,
  versionHash
);

Wallet Origins

Different predicates support different wallet types:

Origin	Description
`fuel`	Native Fuel wallets
`webauthn`	Passkey/biometric authentication
`evm`	Ethereum-compatible wallets
`svm`	Solana-compatible wallets

Next Steps

Status & Monitoring Versions