HCS-12: HashLinks SDK

Build interactive, decentralized experiences on Hedera without smart contracts. HashLinks combines WebAssembly logic, Gutenberg UI blocks, and a composition layer to create powerful applications with minimal fees.

What HashLinks Does

HashLinks enables you to:

• Execute business logic deterministically through WebAssembly modules
• Create rich UI components using WordPress Gutenberg blocks
• Compose applications by binding actions to blocks via assemblies
• Store everything on-chain using Hedera Consensus Service topics
• Run anywhere with both server-side and browser-based clients

Quick Start

Installation

npm install @hashgraphonline/standards-sdk

Basic Setup

import { HCS12Client, Logger } from '@hashgraphonline/standards-sdk';

const client = new HCS12Client({
  network: 'testnet',
  logger: new Logger({ module: 'HCS12' }),
  operatorId: '0.0.123456',
  operatorPrivateKey: 'your-private-key',
});

client.initializeRegistries();

🟦 TypeScript

import { HCS12Client } from '@hashgraphonline/standards-sdk';

const client = new HCS12Client({
  network: 'testnet',
  operatorId: process.env.HEDERA_ACCOUNT_ID!,
  operatorPrivateKey: process.env.HEDERA_PRIVATE_KEY!,
});

🐹 Go

import (
	"context"
	"log"

	"github.com/hashgraph-online/standards-sdk-go/pkg/hcs12"
)

client, err := hcs12.NewClient(hcs12.ClientConfig{
	OperatorAccountID:  "0.0.123456",
	OperatorPrivateKey: "<private-key>",
	Network:            "testnet",
})
if err != nil {
	log.Fatal(err)
}

registry, err := client.CreateRegistryTopic(context.Background(), hcs12.CreateRegistryTopicOptions{
	RegistryType:       hcs12.RegistryTypeAction,
	TTL:                86400,
	UseOperatorAsAdmin: true,
	UseOperatorAsSubmit: true,
})
if err != nil {
	log.Fatal(err)
}

_ = registry

Browser Setup

import { HCS12BrowserClient } from '@hashgraphonline/standards-sdk';

const browserClient = new HCS12BrowserClient({
  network: 'testnet',
  hwc: hashinalsWalletConnectSDK,
});

API Surface & Modules

The HCS-12 SDK exports:

• Clients: HCS12BaseClient, HCS12Client, HCS12BrowserClient
• Composition & UI: builders (Action/Block/Assembly), rendering
• Registries & Types: discovery/catalogue helpers, canonical types
• Validation & WASM: zod schemas, WasmValidator, wasm utilities

See dedicated pages for actions, blocks, assembly, rendering, registries, wasm and security.

Core Architecture

Actions (WebAssembly Logic)

interface WasmInterface {
  INFO(): string;
  POST(...): Promise<string>;
  GET(...): Promise<string>;
}

Blocks (UI Components)

const block = {
  name: 'hashlink/counter',
  template_t_id: '0.0.789',
  attributes: { count: { type: 'number', default: 0 } },
};

Assemblies (Composition Layer)

const assembly = {
  blocks: [blockId],
  actions: { increment: actionId },
  attributes: { count: 10 },
};