Directory prices are claims, not market-clearing prices. This extension lets a seller explicitly advertise a side-effect-free quote-only negotiation handshake; settlement still uses ordinary x402 once a price is accepted.
"extensions": { "negotiation": { "version": 1, "header": "PAYMENT-OFFER", "quote_only": true, "max_rounds": 3 } }
POST /your-endpoint PAYMENT-OFFER: 30000 X-AGENTREEVE-QUOTE-ONLY: 1 Idempotency-Key: route-quote-... // no API side effect; quote only
402 → "accepts":[{ "amount":"30000", ... }],
"extensions":{"negotiation":{"status":"accepted","list_amount":"50000"}}
Accepted = the quote's amount EQUALS the offer; the buyer pays that exact quote and the facilitator settles it as normal x402. Below the seller's hidden floor = "rejected" with the list quote. The seller may advertise up to three bounded rounds; every round remains quote-only, and the router never settles during negotiation.
A percentage-fee router earns more when prices land higher — you can't let it bid for you. AgentReeve's fee is a flat $0.003 whichever price clears, so it is financially indifferent: set negotiate: {enabled:true, target_ratio:0.8, max_rounds:3, on_reject:"best_quote"} on POST /api/route and it bids on your behalf across a compatible shortlist of sellers that advertise quote_only:true, then re-ranks on the accepted effective prices.
Advertise quote_only:true in your 402, honour PAYMENT-OFFER only as a no-side-effect quote request when X-AGENTREEVE-QUOTE-ONLY: 1 is present, and re-quote at the matched amount. The router only negotiates when that safety capability has been observed.
Implementation status: quote-only multi-seller negotiation, re-ranking, exact-quote reconfirmation, durable route nonces, and buyer-direct handoff locking are wired. Production settlement requires payments to be enabled for AgentReeve fees; provider payments remain entirely in the buyer client. Discuss: hello@agentreeve.com