Goldberg Sessions

Goldberg Sessions is a Radius workshop demo for pay-per-buffer audio streaming. The browser only signs payments while it is filling its audio buffer; replaying cached chunks is free, and seeking beyond the buffered range resumes payment.

Browser MediaSource player
  -> signs EIP-712 vouchers per chunk
  -> Cloudflare Worker verifies voucher monotonicity in a Durable Object
  -> SessionEscrow settles the final voucher on Radius testnet

What It Shows

• Two onchain transactions per listening session: open escrow and close settlement.
• Per-chunk EIP-712 vouchers are signed offchain and verified by the Worker before a chunk is served.
• The Worker serves the player, manifest, init segment, and gated fMP4 audio chunks.
• A Durable Object serializes session state so cumulativeAmount can only move forward.
• SBC uses 6 decimals; CHUNK_PRICE = "1000" means 0.001 SBC per chunk.

Repository Layout

Path	Purpose
src/index.ts	Cloudflare Worker routes for /manifest, /session/*, /chunk/:n, and static assets
src/session-do.ts	Durable Object that verifies vouchers and tracks latest session state
src/chain.ts	Radius testnet chain helpers, faucet relay, and SessionEscrow.close submission
assets/index.html	Workshop player UI with an ephemeral viem wallet and Radius transaction links
assets/chunks/	Public-domain audio encoded as an init segment plus fMP4 media chunks
contracts/src/SessionEscrow.sol	Minimal SBC session escrow contract
contracts/script/Deploy.s.sol	Foundry deployment script

Prerequisites

• Node.js 20+
• npm
• Cloudflare Wrangler, installed through npm install
• Foundry, if you want to rebuild or redeploy the escrow contract
• ffmpeg and curl, only if regenerating assets/chunks/

Run Locally

npm install
cp .dev.vars.example .dev.vars
npm run dev

Open http://localhost:8787.

By default, wrangler.toml is configured for the deployed Radius testnet escrow and MOCK_CHAIN = "false". In that mode, set PAYEE_PRIVATE_KEY in .dev.vars so the Worker can submit SessionEscrow.close(...) when a session ends.

For a local-only workshop walkthrough that still exercises voucher verification but skips onchain close submission, set this in wrangler.toml:

MOCK_CHAIN = "true"

Configuration

Var	Purpose
PAYEE_ADDRESS	Wallet receiving settled SBC
TOKEN_ADDRESS	SBC token on Radius testnet
ESCROW_ADDRESS	Deployed SessionEscrow contract
NETWORK	Display/network label
CHAIN_ID	Radius testnet chain ID, 72344
CHUNK_PRICE	Price per chunk in SBC base units
CHUNK_COUNT	Number of media chunks in assets/chunks/
MOCK_CHAIN	When true, skips onchain open/close but keeps voucher verification
PAYEE_PRIVATE_KEY	Wrangler secret used to submit close in real-chain mode

Set production secrets with Wrangler:

npx wrangler secret put PAYEE_PRIVATE_KEY

Rebuild Audio Chunks

The included audio is J.S. Bach's Goldberg Variations BWV 988, Aria, performed by Bradley Lehman and published as public domain through Wikimedia Commons.

npm run prepare-audio

The script prints the generated chunk count. If it changes, update CHUNK_COUNT in wrangler.toml.

Deploy The Escrow Contract

cd contracts
forge install foundry-rs/forge-std --no-commit

export PRIVATE_KEY=0xYourDeployerKey
export SBC_TOKEN=0x33ad9e4BD16B69B5BFdED37D8B5D9fF9aba014Fb

forge script script/Deploy.s.sol \
  --rpc-url https://rpc.testnet.radiustech.xyz \
  --broadcast

After deployment, set ESCROW_ADDRESS in wrangler.toml.

Checks

npm run check
cd contracts && forge build

forge build requires contracts/lib/forge-std, which is intentionally ignored. Install it with the command above before building contracts from a fresh checkout.