The program · TessSeP5…1CQ · Anchor 1.1 · 17 instructions

Five accounts. Everything else is derived.

The one design decision everything rests on

The program trusts a balance, not a message.

/// Permissionless on purpose: the only input it trusts is the vault balance.
pub fn confirm_funded(ctx: Context<ConfirmFunded>) -> Result<()> {
    let vault_balance = ctx.accounts.vault.amount;
    let order = &mut ctx.accounts.order;
    require!(order.state == OrderState::AwaitingPayment, TesseraError::InvalidState);
    require!(vault_balance >= order.amount, TesseraError::VaultUnderfunded);
    order.state = OrderState::Funded;
    ...
}

A facilitator can refuse a payment but cannot redirect one: the buyer's signature fixes recipient, amount and mint. A dishonest merchant server cannot either: the buyer re-derives the escrow address and reads the order from the chain before signing.

programs/tessera/src/lib.rs. A July 2026 study found rule violations in all 15 x402 facilitators it tested (arXiv 2607.19545), which is why nothing here trusts one.

The live network · read from devnet in the browser

Agent to agent, over A2A and x402 · captured from devnet

Choosing who to pay · find_merchants, recorded 2026-10-09

Twelve purchases between real agents, each signed by its own wallet, on a local validator running the real program. Reproduce: npm run build:program && npm run demo:find

Reviews that pay · the airdrop, recorded 2026-10-10

Same pay for any stars; x1.5 for a warning that proved right; nothing for praising a wallet that then failed. Reproduce: npm run build:program && npm run demo:rewards

One formula, three places: program, SDK, browser

let history  = isqrt(credit * 1_000_000 / credit_full).min(1000);
let effective = age_periods.min(active_periods * 3);
let tenure   = (effective * 1000 / tenure_full).min(1000);
let diversity = (points * 1000 / diversity_full).min(1000);

let evidence = (450 * history + 300 * tenure
              + 250 * diversity) / 1000;

let score = evidence * rating * behaviour / (1000 * BPS);

programs/tessera/src/score.rs · packages/sdk/src/score.ts · npm run test:local · npm run test:formula

Stack, and what is not done