# USDT-direct custodial settlement with pending-balance collateral

Nodes are paid directly in USDT — 90% of inference fees, with 10% retained as the protocol cut. TAI (ADR-0002) is **deferred, not cancelled**: the reward token, revenue-backed floor, and halving curve remain the roadmap once volume exists, and the accumulated protocol cut is the future TAI liquidity source. Nothing in this design blocks minting TAI later (an SPL mint is a one-command operation); this ADR amends ADR-0002's settlement mechanics only.

## The design

**Custodial treasury.** A single project-owned Solana wallet holds all funds. Clients deposit USDT into it; a deposit watcher credits their API-key ledger balance off-chain. Node payouts are batched SPL transfers from the treasury. No Anchor/Rust programs are required — the entire on-chain surface is plain SPL token transfers, extending ADR-0007's contract-boundary approach with a real Solana adapter behind the same interface.

**Off-chain ledger, periodic on-chain settlement.** Trackers meter every request against the client's ledger balance and accrue node earnings as a pending balance. Settlement follows the mining-pool standard — pay a node when `pending ≥ payout_threshold` OR `time_since_last_payout ≥ max_period`, whichever fires first, with a dust floor. Dev defaults: period 60s, threshold ≈ 0 (so every run is verifiable on-chain). Prod defaults: period 24h, threshold a few USDT. Both are dynamic config so the period can grow with volume to avoid chain overhead.

**Raft leader settles.** In the tracker hive, only the current Raft leader runs the settlement loop; followers replicate the ledger. The treasury keypair is loaded only on settlement-capable trackers (operator-designated). Third-party trackers can join the mesh for routing but never hold the key.

**Pricing.** Clients are charged a per-1K-tokens USDT price set per model in tracker config. Revenue per request is split among the nodes that served it proportional to work units (layers × tokens), reusing existing attribution.

**Penalty = pending-balance forfeiture (amends ADR-0003).** The validator still re-runs ~5% of jobs. A caught cheater forfeits their entire pending balance to the treasury and receives a strike; three strikes bans the wallet. Because settlement is periodic, the pending balance itself is the collateral — no upfront stake deposit, preserving zero-friction node onboarding. With daily settlement, pending ≈ a day's earnings ≫ 20× the per-job gain at a 5% check rate, so cheating has negative expected value. The probationary period (ADR-0003 / issue 08) is retained as the anti-sybil re-entry cost.

**Cluster.** Development targets **devnet** (supersedes the "testnet, never devnet" note in issue 06 — both are free; devnet is the ecosystem standard for app development with reliable faucets). Real USDT exists only on mainnet, so devnet uses a self-created mock-USDT SPL mint (6 decimals); the mint address is config, making mainnet cutover a config change. CI uses `solana-test-validator` or the local deterministic adapter.

## Considered options

- **Anchor escrow program now**: trustless, but requires the Rust/Anchor toolchain and can't ship today; the custodial trust assumption is acceptable pre-mainnet — deferred.
- **Any tracker settles via lease**: most decentralized, but every mesh member would need the treasury key — rejected while custodial.
- **USDT stake deposits for nodes**: stronger collateral, but adds onboarding friction that contradicts the mining-style UX; may return later as optional stake-for-priority — deferred.
- **Keep TAI settlement (ADR-0002 as written)**: backing-price calc and buyback endpoint are too much machinery before there is volume — deferred.
- **USDT-direct custodial settlement with pending-balance collateral**: shippable immediately, verifiable on-chain end-to-end on devnet — **chosen**.

## Consequences

- The entire payment system works with zero smart contracts; the first Anchor program can replace the custodial treasury later behind the same `packages/contracts` boundary.
- Clients and nodes must trust the treasury key until then; this is explicit and acceptable pre-mainnet.
- Node collateral scales with the settlement period: shortening the period in prod weakens the fraud deterrent, so period changes must consider both chain overhead and collateral size.
- A node caught cheating immediately after a payout has little pending balance to forfeit — the strike/ban system covers this window.
- The 10% protocol cut accumulates in the treasury as the future TAI liquidity reserve.
