Stale reads
— promised; — above budget.
Reserve spend before parallel agents can promise the same money twice.
SpendTruth holds a maximum across money, tokens and calls before work begins. It then replaces that hold with actual usage attested by a registered server-side verifier, without releasing an ambiguous in-flight effect.
Browser demo available; hosted purchase is unconfirmed and remains disabled.
Before and after
| Concurrent budget check | Stale read | Atomic reservation |
|---|---|---|
| Two workers see €5 | Each approves a €4 maximum | First reservation reduces headroom |
| Maximum promised | €8 against €5 | Never above €5 inside the guard |
| Provider reports €2.20 actual | Accounting reconciles later | Unused €1.80 is released after verification |
Free local simulation
Let two workers race for the same budget.
Values remain in this browser. No provider, wallet or payment call is made.
Atomic reservation
Worker B accepted: —. Headroom after attested usage: —.
Inspect the complete local result
This demo proves only the displayed local arithmetic and transition order. Production requires a durable compare-and-swap store plus a registered server-side verifier. The result is provider-authoritative only when that verifier is controlled by the provider or performs a trustworthy provider readback.
Integration
Reserve the worst case before delegating.
- Create one immutable budget for the parent run.
- Reserve maximum money, tokens and calls with a stable logical reservation identity.
- Begin once, then call the provider with the stable idempotency key when supported.
- Settle from usage attested by the registered verifier; keep the maximum reserved while the outcome is unknown.
curl -X POST "$XYNTHERA_GUARD_PRODUCTS_URL/v1/spend-truth/budgets/$BUDGET_ID/reservations" -H "Authorization: Bearer $XYNTHERA_PAYG_CODE" -H "Content-Type: application/json" --data '{"logical_identity":"run-8842/subagent-3/call-1","agent_id":"subagent-3","provider":"provider-name","operation":"research brief","maximum":{"money":{"amount_atomic":"250000","scale":6,"currency":"EUR"},"tokens_atomic":"50000","calls_atomic":"3"}}'The prepaid MCP exposes the same routes through tool spend_truth: reserve is the only counted product operation and the listed recovery operations are free.
PAYG price
€0.00029 excluding tax for the first successful logical reservation, equivalent to €29 per 100,000 reservations. Exact replay, status, settle, release and attested-outcome reconciliation are free.
The live status above determines whether this product can currently consume the existing €10–€10,000 one-time prepaid budget. There is no automatic recharge.