1 · Quote & accept

Phase 1 of the flow. Felix asks Tesser (via Slack) for GTQ; Tesser asks Nexa for a price, shows it to Felix, and locks it when Felix says yes. Both operations are [N] Nexa-hosted, and Tesser calls them.

Step 1 · Create the quote [N]

Operation: POST /v1/quotes: Create quote (op 1) · hosted by Nexa, called by Tesser.

Tesser mints tesser_quote_id (UUIDv4) before the call. It is both the identifier every later call and webhook uses, and the idempotency key. The request carries the customer (FELIX at launch) and desired_gtq, the GTQ Felix wants to end up with.

Nexa replies with the price and with usdc_amount, the USDC Felix must deliver, computed as quoted_gtq / usdc_gtq_price, rounded up at 6dp so that delivering exactly usdc_amount always covers quoted_gtq. Tesser echoes that number and never derives it locally: with two calculators the sides can disagree in the sixth decimal.

• quoted_gtq may be less than desired_gtq. That is a partial fill from limited liquidity. Accepting accepts quoted_gtq; the remainder is a new quote.
• expires_at is the acceptance deadline. Unaccepted quotes expire silently: there is no expiry webhook. Tesser knows expires_at and times out locally.
• Retrying with the same tesser_quote_id and an equivalent body returns 201 with the quote's current state. The same ID with a different body is 409 QUOTE_CONFLICT.

How long a window Nexa can offer, and whether it is fixed or liquidity-dependent, is open question 1.

Step 2 · Accept the quote [N]

Operation: POST /v1/quotes/{tesser_quote_id}/accept: Accept quote (op 2) · hosted by Nexa, called by Tesser.

The body is empty ({}): the path identifies the quote, and acceptance is of quoted_gtq by definition. Accepting locks the rate and starts the deposit_deadline clock.

• deposit_deadline is how long Nexa holds the locked rate waiting for the first deposit report. After the deadline with nothing reported, the quote is EXPIRED and later calls get 409 QUOTE_EXPIRED.
• Re-accepting an already-ACCEPTED (or later-state) quote returns 200 with the quote's current object. It is idempotent, not an error, so a retry after a network blip can never false-fail.
• An unknown tesser_quote_id is 404 QUOTE_NOT_FOUND.

The deadline length, and whether an additional-funds request extends it, is open question 2.

Recovering state

If Tesser loses track of a quote, the optional GET /v1/quotes/{tesser_quote_id} [N] answers "what state do you think it's in?" in one call.

Next: 2 · Deposit reporting.