1. Inventory Race at Accept-Time
Offer signed for qty 2. Live warehouse inventory drops to 1 before buyer acceptance arrives.
Never silently substitute qty 1 or charge buyer. Propose qualified alternative or cleanly expire with zero charge.
2. Offer Tampering (Digit Flip)
Compromised accept request modifies final_price_paise from ₹3,949 to ₹2,949.
Cryptographic HMAC signature check fails immediately, rejecting before any Razorpay API order call.
3. Payment Failure & Method Retry
Razorpay test mode failure card triggered during checkout.
Offers retry with alternative payment method; original price (₹3,949) remains strictly unchanged (no win-back discounts).
4. Buyer Exceeds Mandate Budget
Accept request attempted for an amount exceeding buyer max budget mandate (₹3,949 vs ₹3,000 limit).
Rejected by buyer constraint verifier even if merchant would have honored it.
5. Offer Expiry Window Violation
Acceptance request arrives after the offer expires_at timestamp has elapsed.
Rejected with distinct OFFER_EXPIRED (410) error, clearly separated from signature failure.
6. Delivery Promise SLA Disruption
Warehouse carrier SLA disrupts after offer generation, making delivery promise unreachable.
Caught at accept-time reachability check; does not silently ship late; offers alternative or expires cleanly.
7. LLM Out-of-Policy Interception
Forced hallucinated 50% discount suggestion from LLM.
Deterministic policy engine rejects immediately; proposal NEVER reaches contract signing.
8. Webhook Replay Idempotency
Replay of an already-processed payment.captured Razorpay webhook event.
Idempotency guard short-circuits on event ID, logging duplicate ignored with zero duplicate state transitions.
9. Buyer Priority Actually Wins
Buyer prioritizes lowest price. The genuinely cheapest policy-valid candidate (Candidate C @ ₹3,783) beats higher merchant profit (Candidate A @ ₹3,949).
Buyer stated priority is strictly honored over merchant profit among policy-cleared offers; merchant policy floor is visibly provable.
10. Same Offer, Different Product
Identical buyer budget (₹4,000) sent to slow-moving aged stock vs fast-moving scarce stock.
Engine recommends clearance incentive for aged stock (8.1% discount) and protects list price (0% discount) for fast movers.
11. Reliability Changes the Outcome
Same 3 merchant prices evaluated twice: once with "No preference" (cheapest wins) and once with "4+ stars required" (higher reliability merchant wins instead).
Merchants below buyer-stated reliability floor are excluded before scoring runs; cheaper merchants only lose when buyer explicitly mandates trust.
12. Multi-Protocol Interoperability (ACP vs AP2)
Identical intent submitted in ACP and AP2 formats; both adapt into identical canonical CCO and produce matching signed contracts.
Universal adapter converts heterogeneous agent protocols (ACP, AP2, UCP, x402) into a single canonical CCO with mathematical equivalence.