The42

Chat with any model. Pay per call in stablecoins. No $20 subscriptions, no lock-ins.

What it is The42 is a conversational client that lets anyone use multiple LLMs on-demand and settle each request with micropayments. We embed a passkey smart wallet, support fiat on-ramp, and stream payments during inference so users can switch models without losing context and without monthly commitments.

Problem Barrier to entry: $20+/mo per model blocks access and experimentation. Inefficiency: Power users juggle multiple subscriptions, strand credits, and lose context when switching.

Solution Pay-as-you-go across many models: Top up a few dollars; spend per call. Stablecoin micropayments: PYUSD via x402 streaming—pay exactly what you use, as tokens are generated. Frictionless onboarding: Dynamic embedded wallet with passkey login + Fern on-ramp. No seed phrases, no exchange hopping. Instant receipts: Itemized cost by model, tokens, and time; exportable ledger.

Why now

Model explosion & price dispersion: Costs/latency/quality vary widely, smart switching matters. Payments are ready: Stablecoins + x402 make true micropayments practical. Wallet UX matured: Embedded, passkey wallets remove crypto setup friction. On-ramps everywhere: Easy fiat → stablecoin top-ups enable global access.

Our goal is to democratize access to intelligence. A student or creator can top up $1 and immediately use best-in-class models with no subscriptions, no lock-ins. AI becomes a public utility you meter, not join.

Architecture. React/Next.js chat client + Node.js API for metering and receipts. On-chain ops on Ethereum Sepolia.

Wallets & funding. Dynamic embedded smart wallets EIP7702 (email login) with ZeroDev gasless UX. Fern on-ramp funds ETH on Sepolia; we immediately swap to PYUSD. We chose PYUSD as the rail for its merchant-friendly stablecoin properties.

Models. OpenRouter to access multiple LLM families; a lightweight router preserves conversation context across providers.

Micropayments & settlement. x402-style streaming in PYUSD: start a stream at token generation, meter usage server-side, then finalize a single on-chain settlement with a prompt hash and model ID. Partial streams settle only what was consumed.

Policy & safety. EIP-7702 policy-gated smart accounts enforce per-call caps, daily limits, and allowed recipients; session keys enable smooth UX without exposing the main key.

Verification & receipts. ethers.js validates chain ID, PYUSD ERC-20 transfers, recipients, and exact metered amounts. We store a signed receipt (usage counters, prompt hash, model, tx hash) with CSV export.

Notable hacks.

x402 in PYUSD on Ethereum Sepolia (custom facilitator to support PYUSD streaming + finalization).

EIP-7702 policy-gated contracts for spend controls with passkey wallets.

Stack. React/Next.js, Node.js, Dynamic, ZeroDev, Fern, Ethereum Sepolia, PYUSD, OpenRouter, ethers.js.