walras — abstract

One-page summary of the litepaper. Testnet pre-build; citations resolve in FACTS.md, DECISIONS.md, and EVIDENCE.md.

x402 turns HTTP 402 into a machine-native payment flow: a client requests a resource, the server answers with payment terms, the client signs an authorization, and a facilitator verifies and settles it on-chain. The buyer is software — an agent paying per request with no account and no API key. Stellar fits this well: a settlement costs the operator a measured 22 973 stroops ≈ 0.0023 XLM (F-069), USDC is a first-class SEP-41 asset with 7-decimal base units (F-008, F-052), and Soroban's authorization model lets the buyer sign exactly one bounded contract call — transfer(from, to, amount) with a ledger-bounded expiry — rather than a whole transaction (F-033, F-034).

walras is an x402 facilitator for Stellar plus the piece the ecosystem lacks: a native Bazaar. Any paid HTTP endpoint or MCP tool whose payment settles through walras is automatically cataloged and searchable — settlement is registration, a deliberate anti-spam policy documented as policy, not spec conformance (F-023, D-004). The facilitator is non-custodial by verified construction: it may not be the payer, the source, or an auth participant in any payment it settles (F-035), and network fees are sponsored so buyers hold only the payment asset (F-006).

What is demonstrated, all live on stellar:testnet and transcribed in evidence: an unmodified stock x402 client completing 402 → sign → verify → settle through walras with the transaction verifiable on-chain (F-066, S2-2); the protocol repository's own e2e suite passing 4/4 against walras (F-067, S2-4); automatic cataloging with hostile payloads soft-dropped by machine-readable reason while their settlements succeeded (F-075, S3-4) — including a real settled payment that could not overwrite another seller's listing (D-024); ranked natural-language search with a published evaluation harness (recall@5 0.93, MRR@10 0.91 on a 28-query labeled set, S4-3) and honest partialResults + cursor pagination that no reference operator implements (F-013, D-003); and a generic MCP client completing discover→pay using only two tools — search_resources and paid_call — including paying a live MCP tool that its own settlement then cataloged (S6-3). Every rejection on every path carries a stable machine code and a non-null human reason (D-007, D-028).

The design paper also states what does not exist yet, plainly: the system is unaudited; every proof is testnet; search is a labeled lexical baseline; the upto scheme for Stellar is a design (SEP-41 allowances alone cannot bind a recipient or enforce single settlement — a contract-backed scheme is proposed, with the contract-free variant documented as a weaker trust model); and caller authentication, rate limiting, and catalog retention are planned operator-configurable surface. There is no token.

Apache-2.0, with a copyleft-free shipped dependency path enforced in CI (F-060, D-031). The hosted instance is operated by us; the decentralization claim is that anyone can leave it — the same code self-hosts with one required secret (runbook).