A freight quote isn't an API call: quote locks, expiry and the x402 challenge
Most x402 examples sell something with a fixed price. A weather lookup costs a fraction of a cent. An image generation costs a few cents. The server knows the price before the request arrives, so the HTTP 402 challenge is easy: here's the amount, pay it, get the thing. Freight doesn't work like that. The price of moving one pallet from Fremont to Reno depends on the day, the carrier, the weight…
In the freight industry, a quote lock system is crucial for managing price fluctuations and preventing double payments. Unlike fixed-price APIs, freight quotes change based on various factors such as day, carrier, weight class, and liftgate requirements. The article walks through Nettrux's agent flow to handle this challenge.
First, the agent shops for rates using POST /v1/rates/shop, which returns ranked options without creating a quote ID. This allows the agent to test different lanes and pickup dates without leaving half-reserved shipments. The second step is to lock the price by calling POST /v1/quotes with the chosen option's details. The response includes the quote ID, locked total price, and status (active, converted, expired, or withdrawn).
The locked total price becomes the fixed amount the agent pays against, preventing any changes in the market price from affecting the payment. The validUntil field specifies the time window for the lock, and the idempotent nature of the lock request ensures that retries don't create duplicate reservations.
Next, the agent checks the quote status to decide whether to pay, read the booking, or start over. An active quote allows the agent to commit, while a converted quote indicates that the shipment has already been booked. An expired quote prompts the agent to shop and lock again, and a withdrawn quote requires the agent to start over.
Finally, the agent commits the booking with a single field, POST /v1/immediate-bookings/commit, which points to the locked quote. This commit does not include any payment information, ensuring that no stale amounts or mistyped totals can slip in. The 402 challenge carries the payment terms, and the agent reads them from the response. Upon successful payment, the agent can retrieve the booking receipt with a GET request.
This quote lock system provides a clear, structured approach for freight agents to navigate the challenges of pricing volatility, minimizing the risk of double payments and ensuring smooth transactions.
Written by urgent.news from Dev.to's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
