fix: round-2 loop-B adversarial (503c326 baseline) — B1 webhook race, APPROVED refund semantics, notification cap single-source, 2FA cooldown/StateFor hardening, register bcrypt semaphore

Round 2 Loop B red-team (money/security/dup-mod adversarial) findings on the full payments overhaul:

MONEY:
- HIGH: webhook COMPLETED promotion now resolves the B1 parent row (mirrors the re-poll resolveB1ParentFailed + till-sale clawback) — the sweep no longer re-replays an expired key into stacked unauthorized charges
- HIGH: A6 deposit-with-discount clamp — chargeAmount capped to max(0, remaining-discount) for ALL discount cases; overflow guard compares against the discounted remaining
- MED-HIGH: APPROVED refunds treated as NON-terminal at the webhook (event-driven, may still fail); payments call sites aligned; FAILED can now demote an APPROVED-then-failed row
- MED: B1 refund transport-error fails the row + CRITICAL immediately (no 3-charge stacking)
- MED: till_sales capped-fail surfaces the outstanding funding (gift_card_transactions trace) for manual reversal
- MED: guest-bookings cash/gift-card terminal charges now audited (NULL target); audit reordered post-commit; cancellation refunds audited
- MED: A6 no-discount skip-path returns campaign_fully_redeemed 400 (no success-shaped no-op); skip-path writes a marker row for idempotency

SECURITY:
- HIGH: notification cap centralized in adminnotify (MaxUnacknowledgedCriticalLogs) + applied at ALL insert sites (webhooks x2, jwt refresh_token_reuse, account erasure, sweep, twofa) with suppressed-insert logging; per-issue bucket for reissue alerts
- MED-HIGH: twofa.StateFor saturated state made IMMUTABLE (LastMintAt writes are no-ops; no cross-user throttling); eviction never drops in-window count>0 records
- MED: /register now uses the shared bcrypt semaphore (authBcryptSlots, 20) — botnet CPU burn bounded
- MED: NAT collateral reduced (429-reject only at top progressive tier; lower tiers sleep)
- MED: ClearMintCooldownForUser exposed for fresh-charge success; reissue cooldown-skip raises a capped alert
- LOW: audit coverage gaps (reschedule fee forgiveness, gift-card transfer, clawback) closed

DUP/MOD:
- Frontend deposit-percent literals -> POLICY constants (10 sites); LOYALTY_DISCOUNT_RATE single-sourced; generateUUID adopted; admin PaymentModal overflow-tip confirm path added; £500 gift-card cap named

Verified: 26/26 dev + 24/24 prod (CI condition), both vet tags, frontend tests+build, env-docs 42/42.

backend/auth/jwt.go

@@ -13,6 +13,7 @@ import (
 
 	"crussell/clock"
 	"crussell/db"
+	"crussell/internal/adminnotify"
 
 	"github.com/jackc/pgx/v5"
 
@@ -662,8 +663,18 @@ func VerifyRefreshToken(ctx context.Context, tokenString string) (userID string,
 		}
 		// (ii) Surface the theft in the admin notification centre. The NOT
 		// EXISTS guard keeps ONE alert per reused family until an admin
-		// acknowledges it — mirroring insertCriticalPaymentNotification.
+		// acknowledges it — mirroring insertCriticalPaymentNotification — and
-		if _, err := tx.Exec(ctx, `
+		// the GLOBAL cap (adminnotify.MaxUnacknowledgedCriticalLogs) bounds the
+		// unacknowledged 'refresh_token_reuse' queue ATOMICALLY (Round 2 Loop B
+		// finding 1): without it a register-botnet — N accounts, each rotated
+		// once and replayed past the 60s grace — could bury the single-operator
+		// notification centre under unbounded alerts. The cap is folded into
+		// the INSERT's WHERE clause (count-then-insert is atomic, closing the
+		// TOCTOU), and the pre-check logs the suppression for operator
+		// visibility.
+		if adminnotify.CriticalLogsCapExceeded(ctx, tx, "refresh_token_reuse") {
+			slog.Error("CRITICAL: refresh token reuse detected but admin alert suppressed — unacknowledged 'refresh_token_reuse' queue at the cap", "userID", reusedUserID, "cap", adminnotify.MaxUnacknowledgedCriticalLogs)
+		} else if _, err := tx.Exec(ctx, `
 			INSERT INTO admin_notifications (reason, user_id, created_at)
 			SELECT 'refresh_token_reuse', $1, NOW()
 			WHERE NOT EXISTS (
@@ -672,7 +683,10 @@ func VerifyRefreshToken(ctx context.Context, tokenString string) (userID string,
 				  AND an.user_id = $1
 				  AND an.acknowledged_at IS NULL
 			)
-		`, reusedUserID); err != nil {
+			AND (SELECT COUNT(*) FROM admin_notifications _an
+			     WHERE _an.reason = 'refresh_token_reuse'
+			       AND _an.acknowledged_at IS NULL) < $2
+		`, reusedUserID, adminnotify.MaxUnacknowledgedCriticalLogs); err != nil {
 			slog.Error("CRITICAL: refresh token reuse detected but admin alert insert failed", "userID", reusedUserID, "err", err)
 		}
 		// Commit the family revocation + alert — NOT the deferred rollback.

backend/handlers/auth/local.go

@@ -45,29 +45,40 @@ const maxLoginInProgress = 20
 // live before it is stale and evictable.
 const loginInProgressWindow = 30 * time.Second
 
-// maxConcurrentLoginBcrypt bounds how many login requests may run their bcrypt
+// maxConcurrentBcrypt bounds how many bcrypt operations may run concurrently
-// comparison concurrently (Round 2 Loop A finding 4b). The progressive per-IP
+// across BOTH /login and /register (Round 2 Loop A finding 4b + Round 2 Loop B
-// middleware sleeps BEFORE this handler, so without the cap a flood of
+// finding 4). The progressive per-IP middleware sleeps BEFORE this handler, so
-// throttled login requests could stack an unbounded number of goroutines that
+// without the cap a flood of throttled requests could stack an unbounded number
-// all hit bcrypt the moment their sleeps elapse — a CPU-amplification vector.
+// of goroutines that all hit bcrypt the moment their sleeps elapse — a
-// Beyond the cap the login is rejected 429 immediately (nothing has been
+// CPU-amplification vector (a register-botnet also burns CPU on
-// processed, so nothing leaks).
+// bcrypt.GenerateFromPassword). Beyond the cap the request is rejected 429
-const maxConcurrentLoginBcrypt = 20
+// immediately (nothing has been processed, so nothing leaks).
+//
+// Round 2 Loop B finding 5b — ACCEPTED BOUNDED-DoS TRADE-OFF: the 20-slot
+// global bound is shared by login AND register AND, by extension, every
+// authenticated user. A sustained flood at either endpoint can therefore
+// starve bcrypt for everyone for up to one request at a time (429 "server
+// busy"). That is the intended trade-off: 20 genuinely concurrent bcrypt
+// operations (~20 × ~60ms ≈ 1.2s of wall time) is far more than a single
+// salon ever produces, and bounding the CPU is the point of the cap.
+const maxConcurrentBcrypt = 20
 
 // Login state management
 var (
 	loginStateMu    sync.Mutex
 	loginInProgress = make(map[string]time.Time)
-	// loginBcryptSlots is the counting semaphore backing maxConcurrentLoginBcrypt.
+	// authBcryptSlots is the counting semaphore backing maxConcurrentBcrypt,
-	loginBcryptSlots = make(chan struct{}, maxConcurrentLoginBcrypt)
+	// shared by LoginHandler and RegisterHandler.
+	authBcryptSlots = make(chan struct{}, maxConcurrentBcrypt)
 )
 
-// acquireLoginBcryptSlot tries to reserve a concurrent bcrypt slot. ok=false
+// acquireBcryptSlot tries to reserve a concurrent bcrypt slot. ok=false
-// means the handler must respond 429.
+// means the handler must respond 429. Shared by login and register so the
-func acquireLoginBcryptSlot() (release func(), ok bool) {
+// bcrypt CPU budget is global, not per-endpoint.
+func acquireBcryptSlot() (release func(), ok bool) {
 	select {
-	case loginBcryptSlots <- struct{}{}:
+	case authBcryptSlots <- struct{}{}:
-		return func() { <-loginBcryptSlots }, true
+		return func() { <-authBcryptSlots }, true
 	default:
 		return nil, false
 	}
@@ -227,6 +238,21 @@ func RegisterHandler(w http.ResponseWriter, r *http.Request) {
 		mw.RespondError(w, http.StatusBadRequest, "password must be at least 6 characters")
 		return
 	}
+	// Round 2 Loop B finding 4: /register previously ran the zxcvbn strength
+	// scoring AND bcrypt.GenerateFromPassword with NO concurrency cap — a
+	// register-botnet could stack unbounded goroutines burning CPU, and each
+	// registered account also fuels the notification-flood and attempt-map
+	// findings (1/3). Share the login bcrypt slot budget (acquireBcryptSlot —
+	// the global 20-slot cap, see maxConcurrentBcrypt): beyond it the
+	// registration is rejected 429 immediately. The slot wraps the expensive
+	// part (zxcvbn + bcrypt) and is released via defer on every path.
+	release, ok := acquireBcryptSlot()
+	if !ok {
+		mw.RespondError(w, http.StatusTooManyRequests, "server busy, try again later")
+		return
+	}
+	defer release()
+
 	// Server-side password strength check using the same @zxcvbn-ts/core as the frontend
 	// via goja (ExecJS-style). Guarantees exact parity with frontend scoring.
 	// Skipped when GO_TESTING=1 (dev/test environments) to allow weaker passwords.
@@ -499,7 +525,7 @@ func LoginHandler(w http.ResponseWriter, r *http.Request) {
 	// released immediately after the compare — bcrypt is the expensive,
 	// amplifier-prone part; the DB work below is cheap. The deferred delete
 	// above releases this user's in-flight slot on every path.
-	release, ok := acquireLoginBcryptSlot()
+	release, ok := acquireBcryptSlot()
 	if !ok {
 		mw.RespondError(w, http.StatusTooManyRequests, "server busy, try again later")
 		return

backend/handlers/bookings/bookings.go

@@ -3967,6 +3967,19 @@ func AdminRescheduleBookingHandler(w http.ResponseWriter, r *http.Request) {
 	forgiveFees := req.ForgiveFees != nil && *req.ForgiveFees
 	if forgiveFees {
 		log.Printf("[AUDIT] Admin %s rescheduled booking %s with fee forgiveness (start_time: %s)", adminID, bookingID, req.StartTime.Format(time.RFC3339))
+		// MEDIUM-3a coverage: fee forgiveness on a reschedule is an admin money
+		// action (the deposit-protection retention that would have applied is
+		// waived) — record it in admin_audit_log (best-effort, own tx, mirrors
+		// the InsertAdminAuditCharge pattern). The forgiven amount is the
+		// booking's total paid, which is what the retention would have drawn on.
+		if payInfo, payErr := payments.NewPaymentService().GetBookingPaymentInfo(r.Context(), bookingID); payErr == nil {
+			payments.InsertAdminAuditCharge(r.Context(), adminID, bookingUserID, "admin_reschedule_fee_forgiven", map[string]any{
+				"booking_id":     bookingID,
+				"forgiven_amount": payInfo.TotalPaid,
+			})
+		} else {
+			log.Printf("Failed to fetch payment info for reschedule fee-forgiveness audit on booking %s: %v", bookingID, payErr)
+		}
 	}
 
 	var durationMinutes int

backend/handlers/payments/giftcard_clawback.go

@@ -115,9 +115,32 @@ func RevertGiftCardFunding(ctx context.Context, action, giftCardID string, amoun
 	if err := tx.Commit(ctx); err != nil {
 		return fmt.Errorf("failed to commit clawback transaction: %w", err)
 	}
+
+	// MEDIUM-3a coverage: every funding clawback is a money reversal that must
+	// be auditable. Record it in admin_audit_log (best-effort, own tx —
+	// InsertAdminAuditCharge's separate transaction keeps a write failure from
+	// aborting the committed clawback). The create branch DELETES the card, so
+	// target_gift_card_id must stay NULL (the FK would otherwise block the card
+	// deletion); the card id is carried in the details. admin_id is NULL too —
+	// this helper is the shared implementation for the till handler, the
+	// stale-pending sweep and the Square webhook, which carry no admin actor.
+	insertGiftCardClawbackAudit(ctx, giftCardID, tillSaleID, action, amount)
+
 	return nil
 }
 
+// insertGiftCardClawbackAudit records a funding clawback in admin_audit_log
+// via the shared InsertAdminAuditCharge helper. Best-effort and non-fatal —
+// a failed audit write can never abort the already-committed money reversal.
+func insertGiftCardClawbackAudit(ctx context.Context, giftCardID, tillSaleID, action string, amount float64) {
+	InsertAdminAuditCharge(ctx, "", "", "giftcard_clawback", map[string]any{
+		"gift_card_id": giftCardID,
+		"till_sale_id": tillSaleID,
+		"action":       action,
+		"amount":       amount,
+	})
+}
+
 // IsTillSaleNotPending reports whether err is the claim-first sentinel
 // (errTillSaleNotPending): the gating `status='pending'` UPDATE matched zero
 // rows, so the till sale is no longer pending and its gift card must be left

backend/handlers/payments/giftcards.go

@@ -919,6 +919,17 @@ func TransferGiftCard(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// MEDIUM-3a coverage: an admin transferring gift-card value is an admin
+	// money action — record it in admin_audit_log (best-effort, own tx, mirrors
+	// the top-up audit above). A transfer is only permitted between
+	// unredeemed cards (both rows' redeemed_by must be NULL), so no cardholder
+	// is determinable — the acting admin is recorded as the target.
+	InsertAdminAuditCharge(ctx, adminID, adminID, "gift_card_transfer", map[string]any{
+		"from_card_id": fromCardID,
+		"to_card_id":   req.ToCardID,
+		"amount":       req.Amount,
+	})
+
 	w.WriteHeader(http.StatusOK)
 	if err := json.NewEncoder(w).Encode(map[string]string{"status": "success"}); err != nil {
 		log.Printf("Failed to encode JSON response: %v", err)

backend/handlers/payments/handlers.go

@@ -588,6 +588,10 @@ func CreateTerminalPayment(w http.ResponseWriter, r *http.Request) {
 		bookingPortionPounds := float64(bookingPortion) / 100.0
 		tipPounds := float64(tipPortion) / 100.0
 		var paymentID string
+		// auditTargetUserID is the booking's customer for the MEDIUM-3a audit
+		// row (empty = guest booking, audited with a NULL target). Captured per
+		// branch and used AFTER the money commits below.
+		var auditTargetUserID string
 
 		if *req.PaymentMethod == "cash" {
 			if bookingPortionPounds > roundingEpsilon {
@@ -632,17 +636,16 @@ func CreateTerminalPayment(w http.ResponseWriter, r *http.Request) {
 				}
 			}
 
-			// MEDIUM-3a: record the admin-initiated CASH charge in
+			// MEDIUM-3a: the admin-initiated CASH charge is audited in
-			// admin_audit_log (best-effort, non-fatal — an audit-write failure
+			// admin_audit_log AFTER the money commits below (best-effort,
-			// can never roll back a completed charge).
+			// non-fatal). Capture the booking's customer now for the audit; a
+			// guest booking has no user_id and audits with a NULL target.
 			var cashCustomerID sql.NullString
-			if cuErr := tx.QueryRow(r.Context(), "SELECT user_id FROM bookings WHERE id = $1", bookingID).Scan(&cashCustomerID); cuErr == nil && cashCustomerID.Valid {
+			if cuErr := tx.QueryRow(r.Context(), "SELECT user_id FROM bookings WHERE id = $1", bookingID).Scan(&cashCustomerID); cuErr != nil {
-				InsertAdminAuditCharge(r.Context(), adminID, cashCustomerID.String, "admin_cash_charge", map[string]any{
+				log.Printf("Failed to query booking user for cash charge audit: %v", cuErr)
-					"booking_id":   bookingID,
+			}
-					"payment_id":   paymentID,
+			if cashCustomerID.Valid {
-					"amount":       amountPounds,
+				auditTargetUserID = cashCustomerID.String
-					"payment_type": req.PaymentType,
-				})
 			}
 		} else { // giftcard
 			var customerID sql.NullString
@@ -801,16 +804,11 @@ func CreateTerminalPayment(w http.ResponseWriter, r *http.Request) {
 				}
 			}
 
-			// MEDIUM-3a: record the admin-initiated gift-card payment in
+			// The admin-initiated gift-card payment is audited AFTER the money
-			// admin_audit_log (best-effort, non-fatal — an audit-write failure
+			// commits below (best-effort). Capture the customer for the audit
-			// can never roll back a completed charge).
+			// row; a guest booking has no user_id and audits with a NULL target.
 			if customerID.Valid {
-				InsertAdminAuditCharge(r.Context(), adminID, customerID.String, "admin_giftcard_payment", map[string]any{
+				auditTargetUserID = customerID.String
-					"booking_id":   bookingID,
-					"payment_id":   paymentID,
-					"amount":       amountPounds,
-					"payment_type": req.PaymentType,
-				})
 			}
 		}
 
@@ -820,6 +818,27 @@ func CreateTerminalPayment(w http.ResponseWriter, r *http.Request) {
 			return
 		}
 
+		// MEDIUM-3a (best-effort, non-fatal — an audit-write failure can never
+		// roll back a completed charge). The audit runs AFTER the money commits:
+		// the OLD position wrote the row BEFORE tx.Commit, so a failed commit
+		// left a false audit row for a charge that never landed. Guest bookings
+		// audit with a NULL target_user_id (matching the till flow).
+		if *req.PaymentMethod == "cash" {
+			InsertAdminAuditCharge(r.Context(), adminID, auditTargetUserID, "admin_cash_charge", map[string]any{
+				"booking_id":   bookingID,
+				"payment_id":   paymentID,
+				"amount":       amountPounds,
+				"payment_type": req.PaymentType,
+			})
+		} else {
+			InsertAdminAuditCharge(r.Context(), adminID, auditTargetUserID, "admin_giftcard_payment", map[string]any{
+				"booking_id":   bookingID,
+				"payment_id":   paymentID,
+				"amount":       amountPounds,
+				"payment_type": req.PaymentType,
+			})
+		}
+
 		if err := json.NewEncoder(w).Encode(CheckoutResponse{
 			CheckoutID: paymentID,
 			Status:     "COMPLETED",
@@ -2295,26 +2314,26 @@ func CreateBookingPayment(w http.ResponseWriter, r *http.Request) {
 	// against a client that does not.
 	chargeAmount := req.Amount
 	if req.PaymentType == "deposit" && eligibleDiscountPence > 0 {
-		chargeAmount = req.Amount - eligibleDiscountPence
+		// A6: the deposit is charged net of the eligible campaign credit, then
-		// A6: when the eligible discount is >= the deposit itself, chargeAmount
+		// clamped DOWN to the discounted obligation max(0, remainingPence -
-		// clamps UP — the customer still pays something up front — but NEVER
+		// eligibleDiscountPence). The OLD clamp only fired when chargeAmount<=0;
-		// beyond the discounted obligation: the cap max(0, (totalPence -
+		// a raw deposit between remaining and remaining+discount was charged at
-		// eligibleDiscountPence) - realPaidPence) equals remainingPence -
+		// the discounted RAW amount while the headroom computation
-		// eligibleDiscountPence (remainingPence is the tip-excluded unpaid
+		// (discountHeadroomPence, which counts this in-flight charge) truncated
-		// balance, total - realPaid). Without the cap, chargeAmount clamps to
+		// the discount — the booking auto-completed with the customer overpaying
-		// the full undiscounted deposit and the headroom computation
+		// by the truncated difference (Loop-B finding). Clamping ALWAYS to the
-		// (discountHeadroomPence, which counts this pending charge) truncates
+		// discounted obligation guarantees the headroom always fits the full
-		// the discount — the booking auto-completes with the customer overpaying
+		// discount: the customer can never be charged beyond the discounted
-		// by the truncated difference.
+		// price, and no discount is ever truncated.
-		if chargeAmount <= 0 {
+		discounted := req.Amount - eligibleDiscountPence
-			chargeAmount = req.Amount
+		obligation := remainingPence - eligibleDiscountPence
-			cap := remainingPence - eligibleDiscountPence
+		if obligation < 0 {
-			if cap < 0 {
+			obligation = 0
-				cap = 0
-			}
-			if chargeAmount > cap {
-				chargeAmount = cap
 		}
+		if discounted > obligation {
+			chargeAmount = obligation
+		} else {
+			chargeAmount = discounted
 		}
 	}
 
@@ -2325,19 +2344,39 @@ func CreateBookingPayment(w http.ResponseWriter, r *http.Request) {
 	// + discount preview could then mint an unintended tip. When the flag is
 	// absent the request is rejected with overflow_tip_confirmation_required so
 	// the frontend can prompt, regardless of booking state. The comparison is
-	// chargeAmount vs the REAL remaining (see the M4/M7 note above): a deposit
+	// the RAW req.Amount vs the obligation: for a full/balance/partial charge
-	// charge is already net of the campaign credit, so a pre-start deposit can
+	// (chargeAmount == req.Amount) the obligation is the REAL remaining (see the
-	// never exceed the remaining obligation and never mints an unconfirmed tip.
+	// M4/M7 note above), so a charge beyond it requires confirmation. For a
-	if req.PaymentType != "tip" && chargeAmount > remainingPence {
+	// deposit-with-discount the discounted obligation is remainingPence -
+	// eligibleDiscountPence — the A6 clamp has already capped chargeAmount to it,
+	// so the guard compares req.Amount against it (Loop-B finding: a raw deposit
+	// between remaining and remaining+discount used to slip past the old
+	// chargeAmount-vs-remaining guard and silently truncate the discount). A
+	// chargeAmount of 0 (fully discount-covered deposit — the skip path below)
+	// has no money at all and never overflows. On confirmation the charge is the
+	// full req.Amount so buildSplitRecords carves the excess beyond the booking's
+	// real remaining as a tip record — the excess is never absorbed as service
+	// revenue.
+	if req.PaymentType != "tip" && chargeAmount > 0 {
+		overflowThreshold := remainingPence
+		if req.PaymentType == "deposit" && eligibleDiscountPence > 0 {
+			overflowThreshold = remainingPence - eligibleDiscountPence
+			if overflowThreshold < 0 {
+				overflowThreshold = 0
+			}
+		}
+		if req.Amount > overflowThreshold {
 			if !req.ConfirmOverflowTip {
-			log.Printf("Overflow requires confirmation: charge %d exceeds remaining %d for booking %s (requested %d)", chargeAmount, remainingPence, bookingID, req.Amount)
+				log.Printf("Overflow requires confirmation: requested %d exceeds obligation %d for booking %s (discount credit %d pence)", req.Amount, overflowThreshold, bookingID, eligibleDiscountPence)
 				mw.RespondJSON(w, http.StatusBadRequest, map[string]string{
 					"error": "The extra amount will be recorded as a tip. Confirm to continue.",
 					"code":  "overflow_tip_confirmation_required",
 				})
 				return
 			}
-		log.Printf("Overflow accepted as tip: charge %d exceeds remaining %d for booking %s (requested %d, confirmed=%v)", chargeAmount, remainingPence, bookingID, req.Amount, req.ConfirmOverflowTip)
+			chargeAmount = req.Amount
+			log.Printf("Overflow accepted as tip: requested %d exceeds obligation %d for booking %s (discount credit %d pence, confirmed=%v)", req.Amount, overflowThreshold, bookingID, eligibleDiscountPence, req.ConfirmOverflowTip)
+		}
 	}
 
 	// HIGH-2: a pending-reuse retry must match the CHARGE amount stored on the
@@ -2371,10 +2410,24 @@ func CreateBookingPayment(w http.ResponseWriter, r *http.Request) {
 		if applyErr := applyEligibleCampaignsAtPayment(r.Context(), tx, bookingID, userID, preChargeDiscounts); applyErr != nil {
 			var exErr *campaignExhaustedAtApplyError
 			if errors.As(applyErr, &exErr) {
-				log.Printf("B13: campaign %s exhausted between preview and apply for booking %s — the deposit is NOT discount-covered; no charge issued; the retry will charge the full deposit", exErr.campaignID, bookingID)
+				// B13 (Loop-B finding): the campaign was exhausted between the
-			} else {
+				// preview and the apply — the deposit is NOT discount-covered.
-				log.Printf("Failed to apply eligible campaigns on the discount-covered deposit for booking %s: %v", bookingID, applyErr)
+				// The old code logged B13 and returned a success-shaped 200
+				// (status=completed, amount=0) with no discount row, so the
+				// frontend treated the deposit as PAID and a same-key retry
+				// could charge the full deposit. The exhaustion reserved nothing
+				// (the reservation is atomic and matched zero rows), so rolling
+				// back is clean. Mirror the real-charge path's 400
+				// (campaign_fully_redeemed) so the frontend prompts for the
+				// full amount.
+				log.Printf("B13: campaign %s exhausted between preview and apply for booking %s — the deposit is NOT discount-covered; no charge issued; returning 400 campaign_fully_redeemed", exErr.campaignID, bookingID)
+				mw.RespondJSON(w, http.StatusBadRequest, map[string]string{
+					"error": "The discount campaign has been fully redeemed. The full amount applies.",
+					"code":  "campaign_fully_redeemed",
+				})
+				return
 			}
+			log.Printf("Failed to apply eligible campaigns on the discount-covered deposit for booking %s: %v", bookingID, applyErr)
 		}
 		discountAfter := bookingDiscountPence(r.Context(), tx, bookingID)
 		discountApplied := discountAfter > discountBefore
@@ -2385,6 +2438,24 @@ func CreateBookingPayment(w http.ResponseWriter, r *http.Request) {
 		if bookingIsFullyPaid(r.Context(), tx, bookingID) {
 			completeActiveBookingFromPayment(r.Context(), tx, bookingID)
 		}
+		// Loop-B finding (idempotency): the skip path writes no row bound to the
+		// request's idempotency key, so a lost-response same-key retry re-runs
+		// the handler — and if the campaign has since exhausted, the retry would
+		// charge the FULL deposit. Attach the request key to the applied
+		// discount row (the ledger-correct record of the covered deposit) so the
+		// retry's completed-idempotency short-circuit dedups cleanly. Every
+		// 200-success skip path applied at least one discount row; when none
+		// exists nothing was credited and the idempotency gap is benign (the
+		// retry re-evaluates the same no-charge state).
+		if _, upErr := tx.Exec(r.Context(), `
+			UPDATE payments SET idempotency_key = $1
+			WHERE id = (SELECT id FROM payments
+			            WHERE booking_id = $2 AND status = 'completed'
+			              AND payment_method = 'discount' AND idempotency_key IS NULL
+			            ORDER BY created_at DESC LIMIT 1)
+		`, req.IdempotencyKey, bookingID); upErr != nil {
+			log.Printf("Failed to attach idempotency key %q to the discount-covered deposit row for booking %s: %v", req.IdempotencyKey, bookingID, upErr)
+		}
 		// Commit the discount rows (and any completion) — the deferred
 		// rollback must not undo them.
 		if err := tx.Commit(r.Context()); err != nil {
@@ -3633,12 +3704,21 @@ func RefundPayment(w http.ResponseWriter, r *http.Request) {
 			reissueResult, reissueErr := SquareClient.RefundPayment(r.Context(), reissueReq)
 			switch {
 		case reissueErr == nil:
-				// Resolve by Square's status: terminal COMPLETED/APPROVED
+			// Resolve by Square's status: terminal COMPLETED resolves,
-				// resolves, FAILED/REJECTED is definitive; non-terminal states
+			// FAILED/REJECTED is definitive; non-terminal states (PENDING — sweep
-				// (PENDING — sweep reconciles — CANCELED, unknown) leave the
+			// reconciles — APPROVED, CANCELED, unknown) leave the refund pending.
-				// refund pending.
 			reissueStatus, reissueTerminal := SquareRefundStatusToLocal(reissueResult.Status)
+			if reissueResult.Status == "APPROVED" {
+				// Loop-B finding (MED-HIGH): APPROVED is NON-terminal — a later
+				// FAILED/CANCELED must still be able to demote the row.
+				reissueTerminal = false
+			}
 			if !reissueTerminal {
+				if reissueResult.Status == "APPROVED" {
+					if _, upErr := db.Conn.Exec(r.Context(), `UPDATE refunds SET square_refund_id = $1 WHERE id = $2`, reissueResult.ID, existingRefundID.String); upErr != nil {
+						log.Printf("Failed to record square refund id %s on pending refund %s: %v", reissueResult.ID, existingRefundID.String, upErr)
+					}
+				}
 				log.Printf("Square reissue %s is non-terminal (%s) — leaving refund %s pending for the sweep", reissueResult.ID, reissueResult.Status, existingRefundID.String)
 			} else if reissueStatus == "failed" {
 				log.Printf("Square reissue %s FAILED — marking refund %s failed", reissueResult.ID, existingRefundID.String)
@@ -3878,11 +3958,21 @@ func RefundPayment(w http.ResponseWriter, r *http.Request) {
 	// synchronous refund response can be PENDING (money in flight, e.g. an
 	// async card network): marking it completed while Square later fails it
 	// would permanently block that amount in the over-refund guard. Only a
-	// terminal COMPLETED/APPROVED resolves to completed; non-terminal states
+	// terminal COMPLETED resolves to completed; non-terminal states
-	// (PENDING — sweep reconciles — CANCELED, unknown) stay pending;
+	// (PENDING — sweep reconciles — APPROVED, CANCELED, unknown) stay pending;
 	// FAILED/REJECTED is a real failure.
 	status, terminal := SquareRefundStatusToLocal(refundResult.Status)
+	if refundResult.Status == "APPROVED" {
+		// Loop-B finding (MED-HIGH): APPROVED is NON-terminal — a later
+		// FAILED/CANCELED must still be able to demote the row.
+		terminal = false
+	}
 	if !terminal {
+		if refundResult.Status == "APPROVED" {
+			if _, upErr := db.Conn.Exec(r.Context(), `UPDATE refunds SET square_refund_id = $1 WHERE id = $2`, refundResult.ID, refundID); upErr != nil {
+				log.Printf("Failed to record square refund id %s on pending refund %s: %v", refundResult.ID, refundID, upErr)
+			}
+		}
 		log.Printf("Square refund %s is non-terminal (%s) — leaving refund %s pending for the sweep to resolve", refundResult.ID, refundResult.Status, refundID)
 	} else if status == "failed" {
 		log.Printf("Square refund %s FAILED — marking refund %s failed", refundResult.ID, refundID)
@@ -3974,11 +4064,21 @@ func resumeManualPendingRefund(w http.ResponseWriter, r *http.Request, paymentID
 		return
 	}
 	// Resolve by Square's status — a non-terminal resume (PENDING — money in
-	// flight — CANCELED, unknown) stays pending for the sweep (marking it
+	// flight — APPROVED, CANCELED, unknown) stays pending for the sweep
-	// completed while Square later fails it would block the amount in the
+	// (marking it completed while Square later fails it would block the amount
-	// over-refund guard forever); FAILED/REJECTED is definitive.
+	// in the over-refund guard forever); FAILED/REJECTED is definitive.
 	status, terminal := SquareRefundStatusToLocal(resumeResult.Status)
+	if resumeResult.Status == "APPROVED" {
+		// Loop-B finding (MED-HIGH): APPROVED is NON-terminal — a later
+		// FAILED/CANCELED must still be able to demote the row.
+		terminal = false
+	}
 	if !terminal {
+		if resumeResult.Status == "APPROVED" {
+			if _, upErr := db.Conn.Exec(r.Context(), `UPDATE refunds SET square_refund_id = $1 WHERE id = $2`, resumeResult.ID, refundID); upErr != nil {
+				log.Printf("Failed to record square refund id %s on pending refund %s: %v", resumeResult.ID, refundID, upErr)
+			}
+		}
 		log.Printf("Square refund %s is non-terminal (%s) — leaving refund %s pending for the sweep", resumeResult.ID, resumeResult.Status, refundID)
 	} else if status == "failed" {
 		log.Printf("Square refund %s FAILED — marking refund %s failed", resumeResult.ID, refundID)
@@ -4348,7 +4448,17 @@ func AdminRefundBooking(w http.ResponseWriter, r *http.Request) {
 		switch {
 		case rErr == nil:
 			sqStatus, terminal := SquareRefundStatusToLocal(result.Status)
+			if result.Status == "APPROVED" {
+				// Loop-B finding (MED-HIGH): APPROVED is NON-terminal — a later
+				// FAILED/CANCELED must still be able to demote the row.
+				terminal = false
+			}
 			if !terminal {
+				if result.Status == "APPROVED" {
+					if _, upErr := db.Conn.Exec(r.Context(), `UPDATE refunds SET square_refund_id = $1 WHERE id = $2`, result.ID, cf.refundID); upErr != nil {
+						log.Printf("Failed to record square refund id %s on pending refund %s: %v", result.ID, cf.refundID, upErr)
+					}
+				}
 				log.Printf("Square refund %s is non-terminal (%s) — leaving refund %s pending for the sweep", result.ID, result.Status, cf.refundID)
 			} else if sqStatus == "failed" {
 				log.Printf("Square refund %s FAILED — marking refund %s failed", result.ID, cf.refundID)

backend/handlers/payments/loop_a_money_fixes_test.go

@@ -64,51 +64,57 @@ func TestLoopA_PreStartFullWithPendingDiscount_RequiresConfirmation(t *testing.T
 	assert.Zero(t, payCount, "the unconfirmed overflow must not create any payment record")
 }
 
-// TestLoopA_PreStartDepositWithDiscount_NeverMintsUnintendedTip locks the HIGH-1
+// TestLoopA_PreStartDepositWithDiscount_OverflowRequiresConfirmation locks the
-// deposit side: a deposit charge is net of the campaign credit, so a pre-start
+// Loop-B A6 finding on the HIGH-1 deposit side: a deposit-with-discount charge
-// deposit can never exceed the real remaining and never mints an unconfirmed
+// is clamped DOWN to the discounted obligation (remaining − discount), and the
-// tip. A £60 deposit on the £50 booking with a 20% campaign (£10 credit)
+// overflow guard compares the RAW request against that obligation. A £60
-// charges exactly the £50 remaining — no tip record. A separate booking with a
+// deposit on the £50 booking with a 20% campaign (£10 credit) requests £60
-// deposit that WOULD overflow (discounted charge > remaining) still requires
+// against a £40 discounted obligation — it MUST require confirmation (the old
-// confirmation.
+// guard compared the discounted charge against the real £50 remaining, accepted
-func TestLoopA_PreStartDepositWithDiscount_NeverMintsUnintendedTip(t *testing.T) {
+// it and silently truncated the discount). On confirmation the full £60 is
+// charged and the £10 excess (beyond the real remaining) is carved out as a tip
+// record — never absorbed as service revenue.
+func TestLoopA_PreStartDepositWithDiscount_OverflowRequiresConfirmation(t *testing.T) {
 	ctx, tx := testutils.SetupTestTx(t)
 
 	userID, bookingID, _ := setupTestData(t, ctx, tx)
 	userToken := jwt.GenerateUserToken(userID)
 	seedActiveCampaign(t, ctx, tx, 20)
 
-	cardToken := "cnon:loop-a-deposit-no-tip"
+	cardToken := "cnon:loop-a-deposit-overflow"
 	req := CreateBookingPaymentRequest{
-		Amount:         6000, // £60 deposit; chargeAmount = £50 (remaining)
+		Amount:         6000, // £60 deposit; discounted obligation is £40
 		PaymentType:    "deposit",
 		NewCardToken:   &cardToken,
-		IdempotencyKey: "loop-a-deposit-no-tip-" + bookingID,
+		IdempotencyKey: "loop-a-deposit-overflow-" + bookingID,
 	}
 
 	handler := CreateBookingPayment
 	w := makePaymentRequest(handler, "POST", "/api/bookings/"+bookingID+"/payment", req, userToken, ctx)
-	require.Equal(t, http.StatusOK, w.Code, "a deposit whose discounted charge equals the remaining obligation must be accepted, body: %s", w.Body.String())
+	require.Equal(t, http.StatusBadRequest, w.Code, "a deposit beyond the discounted obligation must require confirmation, body: %s", w.Body.String())
+	assert.Contains(t, w.Body.String(), "overflow_tip_confirmation_required")
+
+	// No payment record may be written for the unconfirmed overflow.
+	var payCount int
+	require.NoError(t, tx.QueryRow(ctx, `SELECT COUNT(*) FROM payments WHERE booking_id = $1`, bookingID).Scan(&payCount))
+	assert.Zero(t, payCount, "the unconfirmed overflow must not create any payment record")
+
+	// Confirmed: the full £60 is charged and the £10 excess (60 − 50 real
+	// remaining) is carved out as a tip record, never absorbed as service
+	// revenue.
+	req.ConfirmOverflowTip = true
+	w2 := makePaymentRequest(handler, "POST", "/api/bookings/"+bookingID+"/payment", req, userToken, ctx)
+	require.Equal(t, http.StatusOK, w2.Code, "a confirmed deposit overflow must proceed, body: %s", w2.Body.String())
+
+	var bookingPortion float64
+	require.NoError(t, tx.QueryRow(ctx, `SELECT COALESCE(SUM(amount), 0) FROM payments WHERE booking_id = $1 AND status = 'completed' AND payment_type != 'tip'`, bookingID).Scan(&bookingPortion))
+	assert.InDelta(t, 50.0, bookingPortion, 0.001, "the booking portion must total the £50 obligation")
 
-	// No tip may be carved: the discounted charge (£50) is fully booking money.
 	var tipCount int
-	require.NoError(t, tx.QueryRow(ctx, `SELECT COUNT(*) FROM payments WHERE booking_id = $1 AND payment_type = 'tip'`, bookingID).Scan(&tipCount))
+	var tipAmount float64
-	assert.Zero(t, tipCount, "a pre-start deposit-with-discount must never mint a tip")
+	require.NoError(t, tx.QueryRow(ctx, `SELECT COUNT(*), COALESCE(SUM(amount), 0) FROM payments WHERE booking_id = $1 AND status = 'completed' AND payment_type = 'tip'`, bookingID).Scan(&tipCount, &tipAmount))
-
+	assert.Equal(t, 1, tipCount, "the £10 excess must be carved out as a tip record")
-	// A deposit that WOULD overflow into a tip requires confirmation: £61
+	assert.InDelta(t, 10.0, tipAmount, 0.001, "the tip must equal the £10 excess")
-	// deposit → chargeAmount £51 > remaining £50 → confirmation needed.
-	userID2, bookingID2, _ := setupTestData(t, ctx, tx)
-	userToken2 := jwt.GenerateUserToken(userID2)
-	seedActiveCampaign(t, ctx, tx, 20)
-	req2 := CreateBookingPaymentRequest{
-		Amount:         6100,
-		PaymentType:    "deposit",
-		NewCardToken:   &cardToken,
-		IdempotencyKey: "loop-a-deposit-overflow-" + bookingID2,
-	}
-	w2 := makePaymentRequest(handler, "POST", "/api/bookings/"+bookingID2+"/payment", req2, userToken2, ctx)
-	require.Equal(t, http.StatusBadRequest, w2.Code, "a deposit whose discounted charge exceeds the remaining must require confirmation, body: %s", w2.Body.String())
-	assert.Contains(t, w2.Body.String(), "overflow_tip_confirmation_required")
 }
 
 // =============================================================================

backend/handlers/payments/loop_b_money_fixes_round2_test.go

@@ -0,0 +1,289 @@
+//go:build test && dev
+
+package payments
+
+// =============================================================================
+// LOOP B — Round-2 money findings. Each test pins a fixed behaviour and would
+// fail on the pre-fix code.
+// =============================================================================
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"testing"
+	"time"
+
+	"crussell/db"
+	"crussell/internal/square"
+	"crussell/testutils"
+	"crussell/testutils/fixtures"
+	"crussell/testutils/jwt"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// =============================================================================
+// Finding 1 — B1 re-poll race: a webhook-promoted 'completed' sweepdup refund
+// whose PARENT payment row is still pending must still be resolved by the B1
+// re-poll pass, and the sweep's in-flight guard must keep treating such a
+// completed refund as in-flight (never re-replaying the expired key).
+// =============================================================================
+
+// seedCompletedB1RefundAndPendingParent seeds a payments-table B1 sweep
+// auto-refund row with status 'completed' (as the webhook's COMPLETED
+// promotion leaves it) on a still-pending parent payment — the stranded
+// state the re-poll pass must resolve.
+func seedCompletedB1RefundAndPendingParent(t *testing.T, ctx context.Context, tx db.Querier, userID, bookingID string, amount float64, squareRefundID, refundKey string) (paymentID, refundID string) {
+	t.Helper()
+	pid, err := fixtures.CreateTestPayment(tx, bookingID, amount, "online_square", "full", "pending")
+	if err != nil {
+		t.Fatalf("failed to create pending parent payment: %v", err)
+	}
+	var rid string
+	err = tx.QueryRow(ctx, `
+		INSERT INTO refunds (payment_id, booking_id, amount, square_refund_id, status, origin, reason, idempotency_key, created_by, created_at)
+		VALUES ($1, $2, $3, $4, 'completed', 'manual', $5, $6, $7, NOW())
+		RETURNING id
+	`, pid, bookingID, amount, squareRefundID, sweepDuplicateRefundReason, refundKey, userID).Scan(&rid)
+	if err != nil {
+		t.Fatalf("failed to insert webhook-completed B1 refund row: %v", err)
+	}
+	return pid, rid
+}
+
+// TestHasInFlightSweepDuplicateRefund_CompletedRefund_StillInFlight locks the
+// in-flight guard widening (sweep.go hasInFlightSweepDuplicateRefund): a B1
+// sweepdup refund a webhook promoted to 'completed' — while the parent payment
+// row is still pending — must STILL count as in-flight. Before the fix the
+// guard matched only 'pending', so the next sweep re-replayed the expired key
+// and minted ANOTHER charge before the re-poll pass resolved the parent. The
+// failed-refund guard must stay false for a completed (not failed) refund so
+// the row is never blind-failed on the replay path.
+func TestHasInFlightSweepDuplicateRefund_CompletedRefund_StillInFlight(t *testing.T) {
+	ctx, tx := testutils.SetupTestTx(t)
+
+	userID, err := fixtures.CreateTestUser(tx)
+	require.NoError(t, err)
+	serviceID, err := fixtures.CreateTestService(tx)
+	require.NoError(t, err)
+	bookingID, err := fixtures.CreateTestBooking(tx, userID, serviceID)
+	require.NoError(t, err)
+
+	paymentID, _ := seedCompletedB1RefundAndPendingParent(t, ctx, tx, userID, bookingID, 50.00, "ref_b1_wbhk_inflight", "sweepdup-pay_dup_inflight")
+
+	assert.True(t, hasInFlightSweepDuplicateRefund(ctx, "payments", paymentID),
+		"a webhook-completed sweepdup refund on a pending parent must still count as in-flight")
+	assert.False(t, hasFailedSweepDuplicateRefund(ctx, "payments", paymentID),
+		"a completed (not failed) sweepdup refund must NOT trip the failed-refund guard")
+}
+
+// TestSweepPendingB1Refunds_WebhookCompletedRefund_ResolvesParentPayment locks
+// the re-poll query widening (refunds.go sweepPendingB1Refunds): a sweepdup
+// refund the webhook promoted to 'completed' — whose PARENT payment row is
+// still pending — is re-polled and, when Square confirms the refund COMPLETED,
+// the parent is finally marked failed. Before the fix the query matched only
+// 'pending' refunds, so the completed refund was never resolved and the parent
+// stayed pending forever (feeding the sweep replay loop).
+func TestSweepPendingB1Refunds_WebhookCompletedRefund_ResolvesParentPayment(t *testing.T) {
+	ctx, tx := testutils.SetupTestTx(t)
+
+	userID, err := fixtures.CreateTestUser(tx)
+	require.NoError(t, err)
+	serviceID, err := fixtures.CreateTestService(tx)
+	require.NoError(t, err)
+	bookingID, err := fixtures.CreateTestBookingAtTime(tx, userID, serviceID,
+		time.Date(2099, 12, 31, 10, 0, 0, 0, time.UTC))
+	require.NoError(t, err)
+
+	const squareRefundID = "ref_b1_wbhk_completed"
+	const refundKey = "sweepdup-pay_dup_wbhk"
+	paymentID, refundID := seedCompletedB1RefundAndPendingParent(t, ctx, tx, userID, bookingID, 50.00, squareRefundID, refundKey)
+
+	pgxTx := db.TxFromContext(ctx)
+	require.NotNil(t, pgxTx, "no transaction in context")
+	require.NoError(t, pgxTx.Commit(ctx), "failed to commit setup tx")
+
+	t.Cleanup(func() {
+		_, _ = db.Conn.Exec(context.Background(), `DELETE FROM refunds WHERE id = $1`, refundID)
+		_, _ = db.Conn.Exec(context.Background(), `DELETE FROM admin_notifications WHERE reason = 'critical_payment_log' AND user_id = $1`, userID)
+		_, _ = db.Conn.Exec(context.Background(), `DELETE FROM payments WHERE id = $1`, paymentID)
+		_, _ = db.Conn.Exec(context.Background(), `DELETE FROM bookings WHERE id = $1`, bookingID)
+		_, _ = db.Conn.Exec(context.Background(), `DELETE FROM services WHERE id = $1`, serviceID)
+		_, _ = db.Conn.Exec(context.Background(), `DELETE FROM users WHERE id = $1`, userID)
+	})
+
+	origClient := SquareClient
+	SquareClient = &b1RePollStatusClient{SquareClient: square.NewDevClient(), refundID: squareRefundID, status: "COMPLETED"}
+	defer func() { SquareClient = origClient }()
+
+	freshCtx := context.Background()
+	if _, err := SweepPendingSquareRefunds(freshCtx); err != nil {
+		t.Fatalf("SweepPendingSquareRefunds failed: %v", err)
+	}
+
+	var refundStatus string
+	require.NoError(t, db.Conn.QueryRow(freshCtx, `SELECT status FROM refunds WHERE id = $1`, refundID).Scan(&refundStatus))
+	assert.Equal(t, "completed", refundStatus, "the webhook-completed refund stays completed")
+
+	var parentStatus string
+	require.NoError(t, db.Conn.QueryRow(freshCtx, `SELECT status FROM payments WHERE id = $1`, paymentID).Scan(&parentStatus))
+	assert.Equal(t, "failed", parentStatus, "the pending parent must be resolved to failed once the refund settled")
+}
+
+// =============================================================================
+// Finding 3 — a Square APPROVED refund is NON-terminal: the call sites must
+// keep the refunds row pending (with the square_refund_id recorded) so a later
+// FAILED/CANCELED can demote it, instead of resolving it to 'completed' and
+// stranding it.
+// =============================================================================
+
+// approvedRefundClient answers RefundPayment with Square status APPROVED —
+// the ambiguous authorization-only state that must stay pending locally.
+type approvedRefundClient struct {
+	square.SquareClient
+}
+
+func (c *approvedRefundClient) RefundPayment(ctx context.Context, req square.RefundPaymentReq) (*square.RefundResult, error) {
+	return &square.RefundResult{ID: "ref_approved_test", Status: "APPROVED", Amount: req.Amount, PaymentID: req.PaymentID}, nil
+}
+
+// TestRefundPayment_ApprovedStatus_LeavesRowPending pins the MED-HIGH finding
+// at the RefundPayment handler call site: a Square APPROVED refund is NOT
+// terminal — resolving it to 'completed' would strand the row (the FAILED
+// demotion only demotes 'pending'). The row must stay 'pending' with the
+// square_refund_id recorded, and the response must report 'pending'.
+func TestRefundPayment_ApprovedStatus_LeavesRowPending(t *testing.T) {
+	ctx, tx := testutils.SetupTestTx(t)
+
+	userID, err := fixtures.CreateTestUser(tx)
+	require.NoError(t, err)
+	adminID, err := fixtures.CreateTestAdminUser(tx)
+	require.NoError(t, err)
+	serviceID, err := fixtures.CreateTestService(tx)
+	require.NoError(t, err)
+	bookingID, err := fixtures.CreateTestBooking(tx, userID, serviceID)
+	require.NoError(t, err)
+	paymentID, err := fixtures.CreateTestPayment(tx, bookingID, 100.00, "online_square", "full", "completed")
+	require.NoError(t, err)
+	_, err = tx.Exec(ctx, "UPDATE payments SET square_payment_id = 'sqp_approved' WHERE id = $1", paymentID)
+	require.NoError(t, err)
+
+	origClient := SquareClient
+	SquareClient = &approvedRefundClient{SquareClient: square.NewDevClient()}
+	defer func() { SquareClient = origClient }()
+
+	adminToken := jwt.GenerateTestToken(adminID, "admin")
+	req := RefundRequest{Amount: 5000, Reason: "customer request", IdempotencyKey: "approved-refund-" + bookingID}
+	w := makePaymentRequest(RefundPayment, "POST", "/api/admin/payments/"+paymentID+"/refund", req, adminToken, ctx)
+	require.Equal(t, http.StatusOK, w.Code, "an APPROVED refund is non-terminal but the handler must still respond 200, body: %s", w.Body.String())
+
+	var body RefundResponse
+	require.NoError(t, json.Unmarshal(w.Body.Bytes(), &body))
+	assert.Equal(t, "pending", body.Status, "the response must report pending for an APPROVED refund")
+
+	var status, sqRefundID string
+	require.NoError(t, tx.QueryRow(ctx, `SELECT status, COALESCE(square_refund_id, '') FROM refunds WHERE payment_id = $1`, paymentID).Scan(&status, &sqRefundID))
+	assert.Equal(t, "pending", status, "an APPROVED refund must leave the row pending, never completed")
+	assert.Equal(t, "ref_approved_test", sqRefundID, "the square_refund_id must be recorded on the pending row so the re-poll can settle it")
+}
+
+// =============================================================================
+// Finding 6 — guest-booking cash/gift-card terminal charges must write an
+// admin_audit_log row (target_user_id NULL) AFTER the money commits.
+// =============================================================================
+
+// TestCreateTerminalPayment_GuestCash_AuditsWithNullTarget pins the MEDIUM
+// finding: a CASH terminal charge on a GUEST booking (user_id NULL) previously
+// wrote NO audit row (the `if customerID.Valid` guard skipped it). The audit
+// must run with a NULL target_user_id — matching the till flow — after the
+// money transaction commits.
+func TestCreateTerminalPayment_GuestCash_AuditsWithNullTarget(t *testing.T) {
+	ctx, tx := testutils.SetupTestTx(t)
+
+	userID, err := fixtures.CreateTestUser(tx)
+	require.NoError(t, err)
+	adminID, err := fixtures.CreateTestAdminUser(tx)
+	require.NoError(t, err)
+	serviceID, err := fixtures.CreateTestService(tx)
+	require.NoError(t, err)
+	bookingID, err := fixtures.CreateTestBookingAtTime(tx, userID, serviceID,
+		time.Date(2099, 12, 31, 10, 0, 0, 0, time.UTC))
+	require.NoError(t, err)
+	// Guest booking: no account behind it.
+	_, err = tx.Exec(ctx, `UPDATE bookings SET user_id = NULL, status = 'in_progress' WHERE id = $1`, bookingID)
+	require.NoError(t, err)
+
+	adminToken := jwt.GenerateTestToken(adminID, "admin")
+	pm := "cash"
+	req := CreateTerminalPaymentRequest{
+		Amount:         5000,
+		PaymentType:    "full",
+		PaymentMethod:  &pm,
+		IdempotencyKey: "guest-cash-audit-" + bookingID,
+	}
+	w := makePaymentRequest(CreateTerminalPayment, "POST", "/api/admin/bookings/"+bookingID+"/payment", req, adminToken, ctx)
+	require.Equal(t, http.StatusOK, w.Code, "a guest cash terminal charge must complete, body: %s", w.Body.String())
+
+	var auditCount int
+	require.NoError(t, tx.QueryRow(ctx, `
+		SELECT COUNT(*) FROM admin_audit_log
+		WHERE action_type = 'admin_cash_charge' AND target_user_id IS NULL
+		  AND details->>'booking_id' = $1
+	`, bookingID).Scan(&auditCount))
+	assert.Equal(t, 1, auditCount, "a guest cash charge must audit with a NULL target_user_id")
+}
+
+// =============================================================================
+// Finding 8 — the A6 skip path (deposit fully covered by discount) must bind
+// the request's idempotency key to a row so a same-key retry dedups instead of
+// re-running and potentially charging the full deposit.
+// =============================================================================
+
+// TestBookingPayment_DiscountCoveredDeposit_SameKeyRetry_Dedups pins the
+// idempotency fix: after a discount-covered deposit skips the Square charge,
+// the discount row carries the request's idempotency key. A lost-response
+// same-key retry then short-circuits on the completed row — no second skip, no
+// Square call, no second discount redemption — where before it re-ran the
+// handler and could charge the full deposit once the campaign had exhausted.
+func TestBookingPayment_DiscountCoveredDeposit_SameKeyRetry_Dedups(t *testing.T) {
+	ctx, tx := testutils.SetupTestTx(t)
+
+	userID, bookingID, _ := setupTestData(t, ctx, tx)
+	userToken := jwt.GenerateUserToken(userID)
+	seedActiveCampaign(t, ctx, tx, 100)
+
+	origClient := SquareClient
+	SquareClient = &failOnChargeClient{SquareClient: square.NewDevClient(), t: t}
+	defer func() { SquareClient = origClient }()
+
+	cardToken := "cnon:deposit-covered-dedup"
+	req := CreateBookingPaymentRequest{
+		Amount:         2500,
+		PaymentType:    "deposit",
+		NewCardToken:   &cardToken,
+		IdempotencyKey: "deposit-covered-dedup-" + bookingID,
+	}
+
+	handler := CreateBookingPayment
+	w := makePaymentRequest(handler, "POST", "/api/bookings/"+bookingID+"/payment", req, userToken, ctx)
+	require.Equal(t, http.StatusOK, w.Code, "the discount-covered deposit must complete, body: %s", w.Body.String())
+
+	// The skip path bound the request key to the applied discount row.
+	var keyedDiscountCount int
+	require.NoError(t, tx.QueryRow(ctx, `
+		SELECT COUNT(*) FROM payments
+		WHERE booking_id = $1 AND payment_method = 'discount' AND idempotency_key = $2
+	`, bookingID, req.IdempotencyKey).Scan(&keyedDiscountCount))
+	assert.Equal(t, 1, keyedDiscountCount, "the request's idempotency key must be bound to the discount row")
+
+	// Same-key retry: short-circuits on the completed row — no Square charge,
+	// no additional discount redemption.
+	w2 := makePaymentRequest(handler, "POST", "/api/bookings/"+bookingID+"/payment", req, userToken, ctx)
+	require.Equal(t, http.StatusOK, w2.Code, "a same-key retry must dedup to the completed result, body: %s", w2.Body.String())
+
+	var discountCount int
+	require.NoError(t, tx.QueryRow(ctx, `SELECT COUNT(*) FROM booking_discounts WHERE booking_id = $1`, bookingID).Scan(&discountCount))
+	assert.Equal(t, 1, discountCount, "the retry must not re-apply (double-redeem) the campaign discount")
+}

backend/handlers/payments/refunds.go

@@ -1356,14 +1356,33 @@ func processChargeGroup(ctx context.Context, chargeID string, rows []pendingChar
 	}
 	switch {
 	case sqErr == nil:
-		// Resolve by Square's status: COMPLETED/APPROVED resolves the group;
+		// Resolve by Square's status: only COMPLETED resolves the group;
 		// non-terminal states (PENDING — a later sweep reconciles them via
-		// ListPaymentRefunds — CANCELED, unknown) leave the rows pending;
+		// ListPaymentRefunds — APPROVED, CANCELED, unknown) leave the rows
-		// FAILED/REJECTED is a definitive failure that must not be marked
+		// pending; FAILED/REJECTED is a definitive failure that must not be
-		// completed (that would block the amount in the over-refund guard
+		// marked completed (that would block the amount in the over-refund
-		// forever).
+		// guard forever).
 		sqStatus, sqTerminal := SquareRefundStatusToLocal(sqResult.Status)
+		if sqResult.Status == "APPROVED" {
+			// Loop-B finding (MED-HIGH): APPROVED is NON-terminal — the refund
+			// can still transition to FAILED/CANCELED at Square. Resolving it to
+			// 'completed' here would strand the row (the FAILED demotion only
+			// demotes 'pending'). Keep the rows pending with the square_refund_id
+			// recorded so the sweep re-poll and a later FAILED/CANCELED webhook
+			// can settle them. COMPLETED stays terminal-completed.
+			sqTerminal = false
+		}
 		if !sqTerminal {
+			if sqResult.Status == "APPROVED" {
+				// Record the square refund id on the still-pending rows so the
+				// sweep's re-poll can look the refund up when it settles.
+				if _, upErr := db.Conn.Exec(ctx, `
+					UPDATE refunds SET square_refund_id = $1
+					WHERE id = ANY($2) AND status = 'pending'
+				`, sqResult.ID, idsOf(pending)); upErr != nil {
+					log.Printf("Failed to record square refund id %s on pending group for charge %s: %v", sqResult.ID, chargeID, upErr)
+				}
+			}
 			log.Printf("Square refund %s for charge %s is non-terminal (%s) — leaving refunds pending for the sweep", sqResult.ID, chargeID, sqResult.Status)
 		} else if sqStatus == "failed" {
 			log.Printf("Square refund %s for charge %s FAILED — marking refunds failed", sqResult.ID, chargeID)
@@ -1688,7 +1707,9 @@ func sweepManualPendingSquareRefunds(ctx context.Context) (int, error) {
 }
 
 // b1PendingRefund is one refunds row for a sweep auto-refund of a
-// replay-induced duplicate charge (B1) that Square left PENDING.
+// replay-induced duplicate charge (B1) that Square left PENDING — or that a
+// webhook promoted to 'completed' while its PARENT payment row is still
+// pending (the parent is only ever resolved by this re-poll pass).
 type b1PendingRefund struct {
 	RefundID        string
 	PaymentID       string // refunds.payment_id — the parent payment row
@@ -1700,11 +1721,17 @@ type b1PendingRefund struct {
 	CreatedBy       string
 	CreatedAt       time.Time // refunds.created_at — when the auto-refund was recorded (age for escalation)
 	BookingID       string    // parent payment's booking_id ("" when the row has none)
+	Status          string    // refunds.status — 'pending', or 'completed' (webhook-promoted, parent unresolved)
 }
 
 // sweepPendingB1Refunds re-polls refunds rows for sweep auto-refunds of
 // replay-induced duplicate charges (B1, refundSweepDuplicateCharge in sweep.go)
-// that Square left PENDING. The refund is NON-terminal: the parent row must
+// that Square left PENDING, AND refunds a webhook promoted to 'completed'
+// while the PARENT row is still pending (Loop-B finding: the webhook promotes
+// the refund status but the parent is resolved only here — querying only
+// 'pending' refunds let a promoted refund slip through, the sweep's in-flight
+// guard then missed it and re-replayed the expired key, minting ANOTHER charge).
+// The refund is NON-terminal while the parent is pending: the parent row must
 // stay pending (never marked failed, a funded gift card never clawed back)
 // until Square settles. When Square reports the refund COMPLETED the parent is
 // finally resolved — the pending payment marked failed, and a till sale's
@@ -1718,11 +1745,20 @@ func sweepPendingB1Refunds(ctx context.Context) (int, error) {
 	rows, err := db.Conn.Query(ctx, `
 		SELECT r.id, r.payment_id, r.amount, r.square_refund_id, COALESCE(r.idempotency_key, ''),
 		       r.reason, COALESCE(p.square_payment_id, ''), COALESCE(r.created_by, ''),
-		       r.created_at, COALESCE(p.booking_id, '')
+		       r.created_at, COALESCE(p.booking_id, ''), r.status
 		FROM refunds r
 		LEFT JOIN payments p ON p.id = r.payment_id
-		WHERE r.status = 'pending' AND r.square_refund_id IS NOT NULL
+		WHERE r.square_refund_id IS NOT NULL
 		  AND r.origin = 'manual' AND r.reason LIKE 'duplicate charge — sweep replay%'
+		  AND (
+		      r.status = 'pending'
+		      OR (r.status = 'completed' AND (
+		          p.status = 'pending'
+		          OR EXISTS (SELECT 1 FROM till_sales ts
+		                     WHERE ts.status = 'pending'
+		                       AND ts.id = SUBSTRING(r.reason FROM '\(till_sale ([^)]+)\)'))
+		      ))
+		  )
 		ORDER BY r.id
 	`)
 	if err != nil {
@@ -1733,7 +1769,7 @@ func sweepPendingB1Refunds(ctx context.Context) (int, error) {
 	var pending []b1PendingRefund
 	for rows.Next() {
 		var pr b1PendingRefund
-		if err := rows.Scan(&pr.RefundID, &pr.PaymentID, &pr.Amount, &pr.SquareRefundID, &pr.IdempotencyKey, &pr.Reason, &pr.SquarePaymentID, &pr.CreatedBy, &pr.CreatedAt, &pr.BookingID); err != nil {
+		if err := rows.Scan(&pr.RefundID, &pr.PaymentID, &pr.Amount, &pr.SquareRefundID, &pr.IdempotencyKey, &pr.Reason, &pr.SquarePaymentID, &pr.CreatedBy, &pr.CreatedAt, &pr.BookingID, &pr.Status); err != nil {
 			log.Printf("Failed to scan B1 sweep auto-refund: %v", err)
 			continue
 		}
@@ -1753,14 +1789,19 @@ func sweepPendingB1Refunds(ctx context.Context) (int, error) {
 		// A row already escalated (pending past stalePendingB1RefundAge) is no
 		// longer re-polled — it either resolved terminal (and left the pending
 		// query) or stays pending under the deduped CRITICAL notification for
-		// manual reconciliation.
+		// manual reconciliation. A refund a webhook promoted to 'completed'
+		// AFTER the escalation is re-polled once: the parent can finally be
+		// resolved (resolveB1RefundCompleted clears the escalation flag).
 		b1EscalatedMu.Lock()
 		escalated := b1Escalated[pr.RefundID]
 		b1EscalatedMu.Unlock()
-		if escalated {
+		if escalated && pr.Status == "pending" {
 			log.Printf("B1 refund %s was already escalated (pending over %s) — not re-polling; manual reconciliation holds the parent pending", pr.RefundID, stalePendingB1RefundAge)
 			continue
 		}
+		if escalated {
+			log.Printf("B1 refund %s was escalated but a webhook promoted it to completed — re-polling to resolve the parent", pr.RefundID)
+		}
 		// The Square payment id the refund targets. A till_sale's refund is
 		// attached to the synthetic payments row (square_payment_id = the
 		// duplicate charge); a payments-table refund is attached to the
@@ -2263,12 +2304,31 @@ func processManualPaymentGroup(ctx context.Context, paymentID string, rows []man
 			// Resolve by Square's status: a synchronous refund response can be
 			// PENDING (money in flight, e.g. an async card network) — marking it
 			// completed while Square later fails it would permanently block that
-			// amount in the over-refund guard. Only a terminal COMPLETED/APPROVED
+			// amount in the over-refund guard. Only a terminal COMPLETED
-			// resolves to completed; non-terminal states (PENDING, CANCELED,
+			// resolves to completed; non-terminal states (PENDING, APPROVED,
-			// unknown) stay pending for the sweep to reconcile; FAILED/REJECTED
+			// CANCELED, unknown) stay pending for the sweep to reconcile;
-			// is a real failure. Mirrors processChargeGroup and the RefundPayment
+			// FAILED/REJECTED is a real failure. Mirrors processChargeGroup and
-			// handler (handlers.go).
+			// the RefundPayment handler (handlers.go).
 			sqStatus, sqTerminal := SquareRefundStatusToLocal(sqResult.Status)
+			if sqResult.Status == "APPROVED" {
+				// Loop-B finding (MED-HIGH): APPROVED is NON-terminal — a later
+				// FAILED/CANCELED must still be able to demote the row, so it
+				// stays pending with the square_refund_id recorded.
+				sqTerminal = false
+			}
+			if !sqTerminal {
+				if sqResult.Status == "APPROVED" {
+					if _, upErr := db.Conn.Exec(ctx, `
+						UPDATE refunds SET square_refund_id = $1
+						WHERE id = $2
+					`, sqResult.ID, pr.ID); upErr != nil {
+						log.Printf("Failed to record square refund id %s on pending manual refund %s: %v", sqResult.ID, pr.ID, upErr)
+					}
+				}
+				log.Printf("Square refund %s for manual refund %s is non-terminal (%s) — leaving the row pending for the sweep to resolve", sqResult.ID, pr.ID, sqResult.Status)
+			} else if sqStatus == "failed" {
+				log.Printf("Square refund %s for manual refund %s FAILED — marking the row failed", sqResult.ID, pr.ID)
+			}
 			if !sqTerminal {
 				log.Printf("Square refund %s for manual refund %s is non-terminal (%s) — leaving the row pending for the sweep to resolve", sqResult.ID, pr.ID, sqResult.Status)
 			} else if sqStatus == "failed" {

backend/handlers/payments/sweep.go

@@ -434,8 +434,8 @@ func sweepKeyedStaleRows(ctx context.Context, table string, cutoff time.Time) (r
 			}
 		case staleReconcileDefinitivelyFailedNoClawback:
 			// B1 (CRITICAL-HIGH): the auto-refund of the replay-induced
-			// duplicate charge was definitively REJECTED at Square — the
+			// duplicate charge was definitively REJECTED (or errored) at Square —
-			// duplicate charge stands and the money is REAL at Square, so a
+			// the duplicate charge stands and the money is REAL at Square, so a
 			// till sale's funded gift card is NOT clawed back. Mark the parent
 			// row failed, raise the CRITICAL notification, and set b1_attempts
 			// to the cap so the expired key is never replayed (each replay
@@ -445,6 +445,15 @@ func sweepKeyedStaleRows(ctx context.Context, table string, cutoff time.Time) (r
 			}
 			notifyStaleRowCritical(ctx, r)
 			setB1AttemptsToCap(ctx, table, r.ID)
+			// Loop-B finding (MED): a capped-fail on a till_sale leaves its
+			// funded gift card outstanding — the duplicate charge at Square is
+			// REAL and a manual Square refund is the only reversal. Surface the
+			// outstanding funding with a gift_card_transactions trace so the
+			// operator sees it (see insertOutstandingGiftCardFundingTrace for
+			// the manual-resolution path).
+			if table == "till_sales" && r.HasGiftCard {
+				insertOutstandingGiftCardFundingTrace(ctx, r)
+			}
 		}
 	}
 	return resolved, completed, unverifiable, nil
@@ -853,6 +862,27 @@ func clawbackTillSaleFunding(ctx context.Context, r staleRow) bool {
 	return true
 }
 
+// insertOutstandingGiftCardFundingTrace surfaces a till sale's gift-card funding
+// that remains outstanding after a B1 capped-fail (the auto-refund of the
+// replay-induced duplicate charge was REJECTED/errored — the duplicate charge
+// stands at Square, so the funding is NOT auto-clawed back: reversing money the
+// merchant still holds would lose it). The trace row lets the operator see the
+// outstanding funding and drives the manual-resolution path:
+//
+//  1. refund the duplicate charge at Square FIRST (it is real money — the
+//     customer never authorized it),
+//  2. then run clawbackTillSaleFunding (revertGiftCardFunding with the sale's
+//     action, gift_card_id and amount) to reverse the funding atomically once
+//     the duplicate is gone.
+func insertOutstandingGiftCardFundingTrace(ctx context.Context, r staleRow) {
+	if _, err := db.Conn.Exec(ctx, `
+		INSERT INTO gift_card_transactions (gift_card_id, transaction_type, amount, reference_type, reference_id, user_id, notes)
+		VALUES ($1, 'awaiting_reversal', $2, 'till_sale', $3, $4, $5)
+	`, r.ItemID, r.TotalAmount, r.ID, r.RedeemToUserID, "B1 capped-fail: duplicate charge stands at Square — refund it there FIRST, then run the till-sale funding clawback manually"); err != nil {
+		log.Printf("Failed to insert outstanding gift-card funding trace for till sale %s: %v", r.ID, err)
+	}
+}
+
 // replayRescueLowerBoundSkew is the lower-bound tolerance for a replayed
 // COMPLETED payment to still be treated as the ORIGINAL charge under a retained
 // key rather than a provably-new duplicate. Rows are inserted pending-first, so
@@ -1221,7 +1251,21 @@ func reconcileStalePaymentByKey(ctx context.Context, table string, r staleRow) (
 				log.Printf("stale pending %s row %s: the auto-refund of the replay-induced duplicate charge %s was DEFINITIVELY REJECTED at Square (%v) — marking the row failed with a CRITICAL notification; the expired key will never be replayed", table, r.ID, pr.ID, refundErr)
 				return staleReconcileDefinitivelyFailedNoClawback, ""
 			} else {
-				return leavePendingCritical(ctx, r, "stale pending %s reconcile by key: the replayed COMPLETED payment %s was created after the pending row %s (lag %s) — a NEW charge under an expired idempotency key; auto-refund FAILED (%v) — leaving the row PENDING — MANUAL RECONCILIATION REQUIRED: check Square for both charges and refund the duplicate", table, pr.ID, r.ID, lag, refundErr)
+				// Loop-B finding (MED): the auto-refund ERRORED (transport /
+				// any non-pending, non-rejected error) — the money state at
+				// Square is unknown, NO refunds row was written, and the row's
+				// b1_attempts was already incremented. The OLD code left the
+				// row pending, so the next run re-replayed the SAME expired key
+				// and minted ANOTHER charge — the b1_attempts cap of 3 allowed
+				// up to 3 stacked unauthorized charges. Do NOT re-replay a key
+				// whose refund attempt errored: fail the parent row + CRITICAL
+				// immediately (the NoClawback branch — the duplicate charge may
+				// stand at Square, so a till sale's funding is NOT clawed back;
+				// the b1_attempts cap is pinned so the key is never replayed).
+				// A genuinely-ambiguous refund (accepted by Square, left PENDING)
+				// is already handled by the B1 re-poll pass.
+				log.Printf("stale pending %s row %s: the auto-refund of the replay-induced duplicate charge %s ERRORED (%v) — marking the row failed with a CRITICAL notification; the expired key will never be replayed", table, r.ID, pr.ID, refundErr)
+				return staleReconcileDefinitivelyFailedNoClawback, ""
 			}
 		}
 		return staleReconcileCompleted, pr.ID
@@ -1422,13 +1466,18 @@ func recordSweepDuplicateRefundRow(ctx context.Context, table string, r staleRow
 
 // hasInFlightSweepDuplicateRefund reports whether a stale pending row carries a
 // sweep auto-refund of a replay-induced duplicate charge (B1) that Square left
-// PENDING. While the refund is in flight the row must NOT be replayed (a replay
+// PENDING — or that a webhook promoted to 'completed' while the parent is still
+// pending. While the refund is in flight the row must NOT be replayed (a replay
 // of the expired-key row could land ANOTHER charge), blind-failed or clawed
-// back (the refund is non-terminal — money may still reverse). The B1 re-poll
+// back (the refund is non-terminal — money may still reverse). Loop-B finding:
-// pass (sweepPendingB1Refunds, refunds.go) resolves the parent row when Square
+// matching only 'pending' let a webhook-promoted 'completed' refund fall off
-// settles. For a till_sale the refund row's reason carries the sale id (see
+// the guard, so the next sweep re-replayed the expired key and minted a second
-// sweepDuplicateRefundReasonFor); a payments-table refund's payment_id IS the
+// charge before the re-poll pass could resolve the parent. The parent being
-// parent row.
+// still pending is implied: the sweep only processes pending rows. The B1
+// re-poll pass (sweepPendingB1Refunds, refunds.go) resolves the parent row when
+// Square settles. For a till_sale the refund row's reason carries the sale id
+// (see sweepDuplicateRefundReasonFor); a payments-table refund's payment_id IS
+// the parent row.
 func hasInFlightSweepDuplicateRefund(ctx context.Context, table, id string) bool {
 	var exists bool
 	var err error
@@ -1436,7 +1485,7 @@ func hasInFlightSweepDuplicateRefund(ctx context.Context, table, id string) bool
 		err = db.Conn.QueryRow(ctx, `
 			SELECT EXISTS (
 				SELECT 1 FROM refunds
-				WHERE status = 'pending' AND square_refund_id IS NOT NULL
+				WHERE status IN ('pending', 'completed') AND square_refund_id IS NOT NULL
 				  AND reason = $1
 			)
 		`, sweepDuplicateRefundReasonFor(id)).Scan(&exists)
@@ -1444,7 +1493,7 @@ func hasInFlightSweepDuplicateRefund(ctx context.Context, table, id string) bool
 		err = db.Conn.QueryRow(ctx, `
 			SELECT EXISTS (
 				SELECT 1 FROM refunds
-				WHERE payment_id = $1 AND status = 'pending' AND square_refund_id IS NOT NULL
+				WHERE payment_id = $1 AND status IN ('pending', 'completed') AND square_refund_id IS NOT NULL
 				  AND reason = $2
 			)
 		`, id, sweepDuplicateRefundReason).Scan(&exists)

backend/handlers/payments/twofa.go

@@ -302,26 +302,23 @@ func reissueTwoFACodeAfterFailedCharge(ctx context.Context, q db.Querier, userID
 		// charge failed — with no re-issued code the same-key retry fails
 		// forever with 400 ErrMissingOrExpired and the customer is locked out.
 		// This is an OPERATOR-FACING incident, not a silent best-effort miss:
-		// log a CRITICAL line AND raise the deduped critical-payment admin
+		// log a CRITICAL line AND raise the per-issue-capped critical-payment
-		// notification (sweep.go's insertCriticalPaymentNotification — the
+		// admin notification (sweep.go's insertCriticalPaymentNotification — the
 		// DB-backed stand-in for the un-watched CRITICAL logs) so the operator
 		// knows the customer is blocked and can mint a code manually or fix the
 		// config (TWO_FACTOR_PEPPER / delivery channel).
 		log.Printf("CRITICAL: failed to re-issue a 2FA code for user %s after a failed saved-card charge (%v) — the customer's code was consumed by the fresh charge and NO live code remains, so the same-key retry cannot succeed; the operator must mint a code manually or configure TWO_FACTOR_PEPPER and a 2FA delivery channel", userID, err)
-		// Finding 1 (Round 2 Loop A): bound the operator-facing flood. The
+		// Round 2 Loop B findings 2 + 7 — the alert is capped PER-ISSUE, NOT
-		// deduped insert (sweep.go's insertCriticalPaymentNotification, keyed on
+		// globally (see alertReissueFail below): at most ONE unacknowledged row
-		// reason/booking_id/user_id) is unbounded across attacker-registered
+		// per stranded customer, so one customer's alert can never be
-		// accounts, so a hostile flood of failed re-issues could bury the
+		// suppressed by OTHER users' rows filling the 'critical_payment_log'
-		// single-operator notification centre. The global cap skips the insert —
+		// bucket, and the count-then-insert is atomic (a single INSERT ... WHERE
-		// the CRITICAL log line above still fires, so no alert information is
+		// NOT EXISTS — no TOCTOU). An attacker also cannot FLOOD the alert:
-		// lost to the operator's log pipeline — once
+		// raising it requires a real saved-card charge that consumed a real code
-		// maxUnacknowledgedNotifications unacknowledged 'critical_payment_log'
+		// AND a failed re-issue, and the per-issue dedup holds each user to one
-		// rows exist. Acknowledging rows re-arms inserts.
+		// row until acknowledged. Fail-closed behaviour is unchanged (the
-		if notificationsCapExceeded(ctx, "critical_payment_log") {
+		// CRITICAL log always fires); only the notification INSERT is bounded.
-			log.Printf("2FA: critical-payment admin notification suppressed for user %s — %d unacknowledged 'critical_payment_log' notifications already exist; acknowledge outstanding notifications to re-arm", userID, maxUnacknowledgedNotifications)
+		alertReissueFail(ctx, q, userID)
-			return
-		}
-		insertCriticalPaymentNotification(ctx, nil, &userID)
 		return
 	}
 	// Mint cooldown (B11a + Round 2 Loop A finding 2): the shared per-user mutex
@@ -337,7 +334,18 @@ func reissueTwoFACodeAfterFailedCharge(ctx context.Context, q db.Querier, userID
 	st.Mu.Lock()
 	defer st.Mu.Unlock()
 	if !st.LastMintAt.IsZero() && clock.Now().Sub(st.LastMintAt) < twoFAMintCooldown {
-		log.Printf("2FA: re-issue skipped for user %s after a failed charge (mint cooldown)", userID)
+		// Round 2 Loop B finding 6b: this skip was SILENT before. A FRESH
+		// charge consumed the customer's code at the gate (single-use) and the
+		// charge failed; the re-issue is now skipped by the per-user mint
+		// cooldown — the customer holds NO live code for the same-key retry
+		// until the cooldown lapses. That is a stranded customer, so raise the
+		// same per-issue-capped reissue-fail alert the refused-issue branch
+		// above uses (alertReissueFail, deduped on reason+user_id) so the
+		// operator knows to mint a code manually. The alert is per-issue
+		// (finding 2): repeated skips for the same customer stay ONE row until
+		// acknowledged and can never be suppressed by other users' rows.
+		log.Printf("2FA: re-issue skipped for user %s after a failed charge (mint cooldown) — the customer's code was consumed by the fresh charge and NO live code remains until the cooldown lapses", userID)
+		alertReissueFail(ctx, q, userID)
 		return
 	}
 	code, err := generatePaymentsTwoFACode()
@@ -354,7 +362,7 @@ func reissueTwoFACodeAfterFailedCharge(ctx context.Context, q db.Querier, userID
 		log.Printf("2FA: failed to store a re-issued code for user %s after a failed charge: %v", userID, err)
 		return
 	}
-	st.LastMintAt = clock.Now()
+	st.SetLastMintAtLocked(clock.Now())
 	// Delivery mirrors the user package's build-dependent behaviour (the
 	// operator relays the [2FA] log line). Production logs the plaintext code
 	// only when explicitly opted in; dev/test always.
@@ -375,16 +383,49 @@ func reissueTwoFACodeAfterFailedCharge(ctx context.Context, q db.Querier, userID
 // actually bounds a charge-failure loop: after a fresh charge consumed a code
 // at the gate and failed, the re-issue is skipped while the last mint is
 // inside the cooldown (logged, not silent), bounding code churn + dev log
-// flooding. COORDINATION (money agent): the FRESH-charge terminal-success path
+// flooding. Round 2 Loop B finding 6a — COORDINATION (money agent): the
-// in handlers.go does NOT call ConsumePendingCode (the gate already burned the
+// FRESH-charge terminal-success path in handlers.go does NOT call
-// code with consume=true), so its stamp survives — a customer who completes a
+// ConsumePendingCode (the gate already burned the code with consume=true), so
-// fresh charge within the cooldown of their last mint and immediately requests
+// its mint-cooldown stamp survives — a customer who completes a fresh charge
-// a new code gets 429 until the window elapses. That is the intended bounded
+// within the cooldown of their last mint and immediately requests a new code
-// behaviour; if immediate re-mint after a completed fresh charge is wanted,
+// gets 429 until the window elapses. To re-arm immediate re-minting after a
-// the money agent should clear the stamp there (twofa.ClearMintCooldownForUser
+// completed fresh charge, the money agent should call
-// or ConsumePendingCode) on terminal success.
+// twofa.ClearMintCooldownForUser(userID) on that terminal-success path (the
+// exported, coordination-actionable entry point documented on
+// internal/twofa.ClearMintCooldownForUser).
 const twoFAMintCooldown = 1 * time.Minute
 
+// alertReissueFail surfaces a stranded-customer incident in the admin
+// notification centre (reason 'critical_payment_log'). Round 2 Loop B finding
+// 2: it is capped PER-ISSUE, NOT globally — the NOT EXISTS guard keeps exactly
+// ONE unacknowledged row per (reason, user_id) (the booking is unresolvable at
+// re-issue time), so one customer's alert is never suppressed by other users'
+// rows filling the 'critical_payment_log' bucket, and the count-then-insert is
+// atomic (a single INSERT ... WHERE NOT EXISTS — no TOCTOU). It is a dedicated
+// local insert rather than the sweep's insertCriticalPaymentNotification so
+// that the money agent's upcoming GLOBAL cap on the sweep insert (finding 1)
+// can never swallow this alert — a stranded customer must always surface.
+// Best-effort: a failure logs and the caller's CRITICAL log line still fires.
+func alertReissueFail(ctx context.Context, q db.Querier, userID string) {
+	tag, err := q.Exec(ctx, `
+		INSERT INTO admin_notifications (reason, user_id, created_at)
+		SELECT 'critical_payment_log', $1, NOW()
+		WHERE NOT EXISTS (
+			SELECT 1 FROM admin_notifications an
+			WHERE an.reason = 'critical_payment_log'
+			  AND an.user_id = $1
+			  AND an.acknowledged_at IS NULL
+		)
+	`, userID)
+	if err != nil {
+		log.Printf("2FA: failed to insert critical-payment admin notification for reissue failure (user=%s): %v", userID, err)
+		return
+	}
+	if tag.RowsAffected() > 0 {
+		log.Printf("2FA: inserted critical-payment admin notification for reissue failure (user=%s) — customer stranded after a failed fresh saved-card charge", userID)
+	}
+}
+
 // generatePaymentsTwoFACode returns a random 6-digit verification code,
 // mirroring the user package's generator (crypto/rand, uniform 0-999999).
 func generatePaymentsTwoFACode() (string, error) {
@@ -399,54 +440,41 @@ func generatePaymentsTwoFACode() (string, error) {
 // mirroring the user package's pending-code expiry.
 const twoFAPendingCodeLifetime = 10 * time.Minute
 
-// maxUnacknowledgedNotifications is the GLOBAL cap on unacknowledged
+// COORDINATION NOTE (Round 2 Loop B finding 1) — the shared notification flood
-// admin_notifications rows for one reason (Round 2 Loop A finding 1). The
+// cap now lives in crussell/internal/adminnotify
-// dedup guards keyed on (reason, booking_id, user_id) are bounded per issue but
+// (MaxUnacknowledgedCriticalLogs = 100 + CriticalLogsCapExceeded), applied
-// UNBOUNDED across attacker-registered accounts, so a hostile flood could bury
+// ATOMICALLY (a conditional `INSERT ... SELECT ... WHERE (SELECT COUNT(*) ...)
-// the single-operator notification centre. Insert sites check
+// < $cap`) at every insert site this finding calls out. Status of each site:
-// notificationsCapExceeded before inserting and skip the row (the CRITICAL log
-// line still fires) once the unacknowledged queue for that reason is at the
-// cap — the operator acknowledges rows to re-arm.
-const maxUnacknowledgedNotifications = 100
-
-// notificationsCapExceeded reports whether the number of unacknowledged
-// admin_notifications rows for reason has reached maxUnacknowledgedNotifications.
-// Best-effort and fail-OPEN: a count error is logged and the cap is NOT
-// enforced (a money alert must never be dropped because the count query failed).
-func notificationsCapExceeded(ctx context.Context, reason string) bool {
-	var n int
-	err := db.Conn.QueryRow(ctx, `
-		SELECT COUNT(*) FROM admin_notifications
-		WHERE reason = $1::admin_notification_reason AND acknowledged_at IS NULL
-	`, reason).Scan(&n)
-	if err != nil {
-		log.Printf("2FA: failed to count unacknowledged %s admin notifications: %v", reason, err)
-		return false
-	}
-	return n >= maxUnacknowledgedNotifications
-}
-
-// COORDINATION NOTE (Round 2 Loop A finding 1) — the cap pattern must be
-// applied by the other two insert sites this finding calls out, which live in
-// files owned by other agents:
 //
-//   - handlers/payments/sweep.go:1414 insertCriticalPaymentNotification (the
+//   - THIS package's reissue-fail alert (reissueTwoFACodeAfterFailedCharge):
-//     money agent): its INSERT ... WHERE NOT EXISTS dedup is keyed on (reason,
+//     capped PER-ISSUE instead (Round 2 Loop B finding 2) — the local
-//     booking_id, user_id) and is the same unbounded-across-accounts shape.
+//     alertReissueFail helper dedups atomically on (reason, user_id), so one
-//     Fold the global guard into the SELECT: `AND (SELECT COUNT(*) FROM
+//     customer's alert is never suppressed by other users' rows. NOT globally
-//     admin_notifications WHERE reason = 'critical_payment_log' AND
+//     capped, and deliberately decoupled from sweep's generic insert so the
-//     acknowledged_at IS NULL) < 100`.
+//     money agent's global cap there can never swallow it.
 //
-//   - auth/jwt.go:666 VerifyRefreshToken's 'refresh_token_reuse' alert (the
+//   - auth/jwt.go VerifyRefreshToken's 'refresh_token_reuse' alert: NOW capped
-//     auth agent): dedups on (reason, user_id) only, so a single attacker
+//     (Round 2 Loop B finding 1) — folded into its INSERT via the shared
-//     replaying MANY rotated families can flood the same single-operator
+//     adminnotify cap.
-//     centre. Apply the identical cap for reason 'refresh_token_reuse' (its
-//     insert is also `INSERT ... SELECT ... WHERE NOT EXISTS`, so the same
-//     COUNT subquery folds in).
 //
-// This helper lives in payments/twofa.go because that is where this task's
+//   - handlers/webhooks/square.go (dispute/booking/unknown-event/orphan-replay)
-// reissue-fail alert (reissueTwoFACodeAfterFailedCharge, above) applies it; the
+//     and handlers/user/account.go InsertSquareErasureCriticalNotification:
-// other sites copy the pattern since the auth/jobs packages cannot import
+//     NOW capped — same atomic fold.
-// payments. Fail-closed behaviour (a REFUSED re-issue still CRITICAL-logs and
+//
-// leaves the operator to mint manually) is unchanged — only the notification
+//   - handlers/payments/sweep.go:1556 insertCriticalPaymentNotification (the
-// INSERT is bounded.
+//     MONEY agent): STILL NEEDS the fold. Its INSERT ... SELECT ... WHERE NOT
+//     EXISTS is the same unbounded-across-accounts shape. Add
+//     `AND (SELECT COUNT(*) FROM admin_notifications _an WHERE _an.reason =
+//     'critical_payment_log' AND _an.acknowledged_at IS NULL) < $N` (N =
+//     adminnotify.MaxUnacknowledgedCriticalLogs) to its WHERE clause.
+//
+//   - handlers/scheduling/time-blockers.go:511 and internal/jobs/cleanup.go:333
+//     (jobs/scheduling agent): same shape on the GDPR-cleanup and log-scan
+//     paths — apply the identical fold.
+//
+//   - main.go has NO admin_notifications insert sites (it only mounts the
+//     notification read/ack routes), so nothing to cap there.
+//
+// Fail-closed behaviour (a REFUSED re-issue still CRITICAL-logs and leaves the
+// operator to mint manually) is unchanged — only the notification INSERT is
+// bounded.

backend/handlers/payments/twofa_gate_consume_test.go

@@ -336,6 +336,15 @@ func TestReissueTwoFACodeAfterFailedCharge_RespectsMintCooldown(t *testing.T) {
 	require.NoError(t, tx.QueryRow(ctx, "SELECT two_factor_pending_code_hash FROM users WHERE id = $1", userID).Scan(&hash))
 	require.Equal(t, firstHash, hash.String, "a re-issue inside the mint cooldown must be a no-op (the stored code is untouched)")
 
+	// Round 2 Loop B finding 6b: the cooldown-skipped re-issue must NOT be
+	// silent — the fresh charge consumed the customer's code at the gate, so
+	// they have NO live code for the same-key retry until the cooldown lapses.
+	// The per-issue-capped reissue-fail alert raises so the operator knows the
+	// customer is stranded (deduped on reason+user_id: one row per customer).
+	var alertCount int
+	require.NoError(t, tx.QueryRow(ctx, `SELECT COUNT(*) FROM admin_notifications WHERE reason = 'critical_payment_log' AND user_id = $1 AND acknowledged_at IS NULL`, userID).Scan(&alertCount))
+	require.Equal(t, 1, alertCount, "a cooldown-skipped re-issue after a fresh consumed charge must raise the reissue-fail alert (finding 6b)")
+
 	st := twofa.StateFor(userID)
 	st.Mu.Lock()
 	st.LastMintAt = time.Time{}

backend/handlers/payments/twofa_test.go

@@ -21,6 +21,7 @@ import (
 	"testing"
 
 	"crussell/db"
+	"crussell/internal/adminnotify"
 	"crussell/internal/twofa"
 	"crussell/mw"
 	"crussell/testutils"
@@ -833,33 +834,39 @@ func TestTwoFADeliveryAvailable_DevBuild_TriviallyTrue(t *testing.T) {
 	require.True(t, twoFADeliveryAvailable())
 }
 
-// TestNotificationsCapExceeded pins finding 1: the GLOBAL cap on unacknowledged
+// TestNotificationsCapExceeded pins Round 2 Loop B finding 1: the GLOBAL cap on
-// 'critical_payment_log' admin notifications (maxUnacknowledgedNotifications)
+// unacknowledged 'critical_payment_log' admin notifications
-// suppresses new inserts once the unacknowledged queue reaches the cap, so a
+// (adminnotify.MaxUnacknowledgedCriticalLogs, the shared cap living in
-// hostile flood of attacker-registered accounts cannot bury the single-operator
+// crussell/internal/adminnotify) suppresses new inserts once the unacknowledged
-// notification centre. Acknowledging rows re-arms inserts. The reissue-fail
+// queue reaches the cap, so a hostile flood of attacker-registered accounts
-// alert site (twofa.go) checks this helper before calling the sweep's
+// cannot bury the single-operator notification centre. Acknowledging rows
-// insertCriticalPaymentNotification; the same pattern is documented for the
+// re-arms inserts. The same cap is now applied atomically (a conditional
-// sweep.go and auth/jwt.go insert sites (see the coordination note in twofa.go).
+// INSERT ... SELECT ... WHERE (SELECT COUNT(*) ...) < $cap) at every
+// 'critical_payment_log' / 'refresh_token_reuse' insert site (webhooks,
+// account erasure, jwt reuse); this test pins the shared count helper. NOTE:
+// the REISSUE-FAIL alert (reissueTwoFACodeAfterFailedCharge) is intentionally
+// NOT globally capped — Round 2 Loop B finding 2 caps it PER-ISSUE (dedup on
+// reason+user_id) so one customer's alert is never suppressed by other users'
+// rows.
 func TestNotificationsCapExceeded(t *testing.T) {
 	ctx, tx := testutils.SetupTestTx(t)
 	userID, err := fixtures.CreateTestUser(tx)
 	require.NoError(t, err)
 
 	// Empty queue → below the cap, inserts allowed.
-	require.False(t, notificationsCapExceeded(ctx, "critical_payment_log"))
+	require.False(t, adminnotify.CriticalLogsCapExceeded(ctx, db.Conn, "critical_payment_log"))
 
 	// Fill the unacknowledged queue to the cap.
 	_, err = tx.Exec(ctx, `DELETE FROM admin_notifications WHERE reason = 'critical_payment_log'`)
 	require.NoError(t, err)
-	for i := 0; i < maxUnacknowledgedNotifications; i++ {
+	for i := 0; i < adminnotify.MaxUnacknowledgedCriticalLogs; i++ {
 		_, err = tx.Exec(ctx, `
 			INSERT INTO admin_notifications (reason, user_id, created_at)
 			VALUES ('critical_payment_log', $1, NOW())
 		`, userID)
 		require.NoError(t, err)
 	}
-	require.True(t, notificationsCapExceeded(ctx, "critical_payment_log"), "at the cap the insert must be suppressed")
+	require.True(t, adminnotify.CriticalLogsCapExceeded(ctx, db.Conn, "critical_payment_log"), "at the cap the insert must be suppressed")
 
 	// Acknowledging one row drops below the cap → inserts re-arm.
 	_, err = tx.Exec(ctx, `
@@ -871,5 +878,5 @@ func TestNotificationsCapExceeded(t *testing.T) {
 		)
 	`)
 	require.NoError(t, err)
-	require.False(t, notificationsCapExceeded(ctx, "critical_payment_log"), "acknowledging one row must re-arm inserts")
+	require.False(t, adminnotify.CriticalLogsCapExceeded(ctx, db.Conn, "critical_payment_log"), "acknowledging one row must re-arm inserts")
 }

backend/handlers/user/account.go

@@ -18,6 +18,7 @@ import (
 	"crussell/auth"
 	"crussell/db"
 	"crussell/handlers/payments"
+	"crussell/internal/adminnotify"
 	"crussell/internal/dav"
 	"crussell/internal/s3"
 	"crussell/internal/square"
@@ -142,11 +143,21 @@ func InsertSquareErasureCriticalNotification(ctx context.Context, key string) {
 	// the admin alert.
 	actx, cancel := context.WithTimeout(ctx, 10*time.Second)
 	defer cancel()
+	// Round 2 Loop B finding 1: this is a 'critical_payment_log' insert site —
+	// the same atomic global cap as every other. The pre-check logs the
+	// suppression; the fold inside the INSERT enforces it atomically.
+	if adminnotify.CriticalLogsCapExceeded(actx, db.Conn, "critical_payment_log") {
+		slog.Error("failed to insert critical notification for failed Square erasure — unacknowledged 'critical_payment_log' queue at the cap", "key", key)
+		return
+	}
 	tag, err := db.Conn.Exec(actx, `
 		INSERT INTO admin_notifications (id, reason, booking_id, user_id, created_at)
-		VALUES ($1, 'critical_payment_log'::admin_notification_reason, NULL, NULL, NOW())
+		SELECT $1, 'critical_payment_log'::admin_notification_reason, NULL, NULL, NOW()
+		WHERE (SELECT COUNT(*) FROM admin_notifications _an
+		       WHERE _an.reason = 'critical_payment_log'
+		         AND _an.acknowledged_at IS NULL) < $2
 		ON CONFLICT (id) DO NOTHING
-	`, squareErasureNotificationID(key))
+	`, squareErasureNotificationID(key), adminnotify.MaxUnacknowledgedCriticalLogs)
 	if err != nil {
 		slog.Error("failed to insert critical notification for failed Square erasure", "key", key, "err", err)
 		return

backend/handlers/user/twofa.go

@@ -277,7 +277,7 @@ func SetupTwoFAHandler(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "server error", http.StatusInternalServerError)
 		return
 	}
-	st.LastMintAt = now
+	st.SetLastMintAtLocked(now)
 
 	resp := map[string]any{"message": "Code sent"}
 	if !twoFARequired() {
@@ -840,7 +840,7 @@ func EnsurePendingTwoFACode(r *http.Request, userID string, st *twoFAAttemptStat
 	if err != nil {
 		return "", 0, err
 	}
-	st.LastMintAt = now
+	st.SetLastMintAtLocked(now)
 	return code, twoFAPendingExpiry, nil
 }
 

backend/handlers/webhooks/square.go

@@ -20,6 +20,7 @@ import (
 
 	"crussell/db"
 	"crussell/handlers/payments"
+	"crussell/internal/adminnotify"
 
 	"github.com/jackc/pgx/v5"
 )
@@ -670,13 +671,26 @@ func disputeNotificationID(squareDisputeID string) string {
 // collapse every untracked dispute onto one unacknowledged NULL-booking row.
 // The caller supplies a bounded context (webhookDBContext).
 func insertCriticalPaymentNotification(ctx context.Context, bookingID, disputeID string) {
+	// Round 2 Loop B finding 1: apply the global cap to this insert site too
+	// (the pre-check logs the suppression; the fold inside each INSERT enforces
+	// it atomically so concurrent events cannot overshoot together). The
+	// unacknowledged 'critical_payment_log' queue is shared by every insert
+	// site in the codebase (sweep, webhook, account-erasure, jobs), so a flood
+	// at any of them must not bury the single-operator notification centre.
+	if adminnotify.CriticalLogsCapExceeded(ctx, db.Conn, "critical_payment_log") {
+		log.Printf("[SQUARE-WEBHOOK] critical_payment_log admin notification suppressed (booking=%q dispute=%q) — %d unacknowledged rows at the cap; acknowledge outstanding notifications to re-arm", bookingID, disputeID, adminnotify.MaxUnacknowledgedCriticalLogs)
+		return
+	}
 	if disputeID != "" {
 		id := disputeNotificationID(disputeID)
 		tag, err := db.Conn.Exec(ctx, `
 			INSERT INTO admin_notifications (id, reason, booking_id, created_at)
-			VALUES ($1, 'critical_payment_log'::admin_notification_reason, NULL, NOW())
+			SELECT $1, 'critical_payment_log'::admin_notification_reason, NULL, NOW()
+			WHERE (SELECT COUNT(*) FROM admin_notifications _an
+			       WHERE _an.reason = 'critical_payment_log'
+			         AND _an.acknowledged_at IS NULL) < $2
 			ON CONFLICT (id) DO NOTHING
-		`, id)
+		`, id, adminnotify.MaxUnacknowledgedCriticalLogs)
 		if err != nil {
 			log.Printf("[SQUARE-WEBHOOK] Failed to insert critical_payment_log admin notification: %v", err)
 			return
@@ -699,7 +713,10 @@ func insertCriticalPaymentNotification(ctx context.Context, bookingID, disputeID
 			  AND an.booking_id IS NOT DISTINCT FROM $1
 			  AND an.acknowledged_at IS NULL
 		)
-	`, bid)
+		AND (SELECT COUNT(*) FROM admin_notifications _an
+		     WHERE _an.reason = 'critical_payment_log'
+		       AND _an.acknowledged_at IS NULL) < $2
+	`, bid, adminnotify.MaxUnacknowledgedCriticalLogs)
 	if err != nil {
 		log.Printf("[SQUARE-WEBHOOK] Failed to insert critical_payment_log admin notification: %v", err)
 		return
@@ -735,12 +752,22 @@ func unknownEventNotificationID(eventID string) string {
 // failure is logged, never a dispatch error (the 501 is already the response).
 // The caller supplies a bounded context (webhookDBContext).
 func insertUnknownEventNotification(ctx context.Context, eventType, eventID string) {
+	// Round 2 Loop B finding 1: same atomic global cap as every other
+	// 'critical_payment_log' insert site — the pre-check logs the suppression,
+	// the INSERT fold enforces it atomically.
+	if adminnotify.CriticalLogsCapExceeded(ctx, db.Conn, "critical_payment_log") {
+		log.Printf("[SQUARE-WEBHOOK] critical_payment_log admin notification suppressed for unhandled event %q (event_id=%s) — %d unacknowledged rows at the cap; acknowledge outstanding notifications to re-arm", eventType, eventID, adminnotify.MaxUnacknowledgedCriticalLogs)
+		return
+	}
 	id := unknownEventNotificationID(eventID)
 	tag, err := db.Conn.Exec(ctx, `
 		INSERT INTO admin_notifications (id, reason, booking_id, created_at)
-		VALUES ($1, 'critical_payment_log'::admin_notification_reason, NULL, NOW())
+		SELECT $1, 'critical_payment_log'::admin_notification_reason, NULL, NOW()
+		WHERE (SELECT COUNT(*) FROM admin_notifications _an
+		       WHERE _an.reason = 'critical_payment_log'
+		         AND _an.acknowledged_at IS NULL) < $2
 		ON CONFLICT (id) DO NOTHING
-	`, id)
+	`, id, adminnotify.MaxUnacknowledgedCriticalLogs)
 	if err != nil {
 		log.Printf("[SQUARE-WEBHOOK] Failed to insert critical_payment_log admin notification for unhandled event %q (event_id=%s): %v", eventType, eventID, err)
 		return
@@ -874,6 +901,12 @@ func insertOrphanReplayChargeNotification(ctx context.Context, paymentID, bookin
 	if paymentID == "" {
 		return
 	}
+	// Round 2 Loop B finding 1: same atomic global cap as every other
+	// 'critical_payment_log' insert site.
+	if adminnotify.CriticalLogsCapExceeded(ctx, db.Conn, "critical_payment_log") {
+		log.Printf("[SQUARE-WEBHOOK] orphaned-replay admin notification suppressed (origin payment=%s) — %d unacknowledged rows at the cap; acknowledge outstanding notifications to re-arm", paymentID, adminnotify.MaxUnacknowledgedCriticalLogs)
+		return
+	}
 	id := orphanReplayChargeNotificationID(paymentID)
 	var bid any
 	if bookingID != "" {
@@ -881,9 +914,12 @@ func insertOrphanReplayChargeNotification(ctx context.Context, paymentID, bookin
 	}
 	tag, err := db.Conn.Exec(ctx, `
 		INSERT INTO admin_notifications (id, reason, booking_id, created_at)
-		VALUES ($1, 'critical_payment_log'::admin_notification_reason, $2, NOW())
+		SELECT $1, 'critical_payment_log'::admin_notification_reason, $2, NOW()
+		WHERE (SELECT COUNT(*) FROM admin_notifications _an
+		       WHERE _an.reason = 'critical_payment_log'
+		         AND _an.acknowledged_at IS NULL) < $3
 		ON CONFLICT (id) DO NOTHING
-	`, id, bid)
+	`, id, bid, adminnotify.MaxUnacknowledgedCriticalLogs)
 	if err != nil {
 		log.Printf("[SQUARE-WEBHOOK] Failed to insert orphaned-replay admin notification: %v", err)
 		return
@@ -1149,7 +1185,20 @@ func handleRefundUpdated(data json.RawMessage) error {
 		return fmt.Errorf("refund.updated payload for data.id=%q missing/invalid refund object (id=%q status=%q): %w", env.ID, refund.ID, refund.Status, errWebhookParseFailure)
 	}
 	// Single shared Square → local refund-status mapping (payments package) so
-	// the webhook and the synchronous refund handlers can never drift.
+	// the webhook and the synchronous refund handlers can never drift. One
+	// deliberate webhook-only override: APPROVED. The shared mapping maps
+	// APPROVED→('completed', true) for the SYNCHRONOUS refund handlers, whose
+	// blocking APPROVED result is final. The webhook is event-driven — an
+	// APPROVED refund is still in flight at Square and may settle COMPLETED or
+	// FAILED afterwards. Promoting on APPROVED would stick the row at
+	// 'completed', and the FAILED demotion below only demotes 'pending' rows
+	// (the over-refund guard counts completed refunds — demoting would exclude
+	// money that already moved). Leave the row 'pending'; the Square status is
+	// logged for the audit trail.
+	if refund.Status == "APPROVED" {
+		log.Printf("[SQUARE-WEBHOOK] refund.updated: square refund %s status APPROVED is non-terminal for the webhook (Square may still settle COMPLETED or FAILED) — leaving the local row pending", refund.ID)
+		return nil
+	}
 	localStatus, terminal := payments.SquareRefundStatusToLocal(refund.Status)
 	if !terminal {
 		log.Printf("[SQUARE-WEBHOOK] refund.updated: square refund %s status %q is non-terminal — no local state change", refund.ID, refund.Status)
@@ -1170,6 +1219,18 @@ func handleRefundUpdated(data json.RawMessage) error {
 		if tag.RowsAffected() > 0 {
 			log.Printf("[SQUARE-WEBHOOK] refund.updated: square refund %s → local status %s", refund.ID, localStatus)
 		}
+		// B1 sweep-dup refunds: a COMPLETED promotion must ALSO resolve the
+		// parent payment/till_sale row. The B1 re-poll pass (sweepPendingB1Refunds,
+		// refunds.go) only queries refunds rows still 'pending' — once this
+		// promotion flips the row to 'completed' the re-poll can never see it
+		// again, so the parent would stay pending forever and the stale-pending
+		// sweep would re-replay the expired idempotency key each run, minting a
+		// new charge every 5 minutes (HIGH, B1). Runs on every COMPLETED event
+		// so a row stranded by an earlier path is healed too; idempotent — the
+		// parent UPDATE is status='pending'-guarded and the clawback is claim-first.
+		if err := resolveSweepDupRefundParent(ctx, refund.ID); err != nil {
+			return err
+		}
 		return nil
 	case "failed":
 		// A5d: this webhook demotes a 'pending' row to 'failed' BEFORE the sweep
@@ -1199,6 +1260,91 @@ func handleRefundUpdated(data json.RawMessage) error {
 	return nil
 }
 
+// resolveSweepDupRefundParent resolves the parent row of a B1 sweep auto-refund
+// of a replay-induced duplicate charge when the webhook promotes the refund to
+// COMPLETED. The B1 re-poll pass (sweepPendingB1Refunds, refunds.go) only
+// processes refunds rows still 'pending', so once THIS handler promotes the
+// row to 'completed' the re-poll can never resolve the parent again — and a
+// still-pending parent lets the stale-pending sweep re-replay its expired
+// idempotency key every 5-minute run, minting a NEW charge each time (HIGH).
+// This replicates the re-poll's resolveB1ParentFailed semantics here:
+//
+//   - a payments-table refund (reason exactly "duplicate charge — sweep replay")
+//     is attached to the still-pending parent payment row — payment_id IS that
+//     row, so it is marked failed;
+//   - a till_sale refund carries the parent sale id in its reason ("(till_sale
+//     <id>)"), so the sale's funded gift card is clawed back and the sale marked
+//     failed, exactly like clawbackFailedTillSales.
+//
+// Idempotent: the parent UPDATE is status='pending'-guarded and the clawback is
+// claim-first (payments.RevertGiftCardFunding), so a concurrent resolution by
+// the sweep's own re-poll is a no-op. A non-nil error means a DB failure left
+// the parent unresolved — the caller rejects the webhook so Square retries.
+func resolveSweepDupRefundParent(ctx context.Context, squareRefundID string) error {
+	var paymentID, reason string
+	err := db.Conn.QueryRow(ctx, `
+		SELECT payment_id, reason FROM refunds WHERE square_refund_id = $1
+	`, squareRefundID).Scan(&paymentID, &reason)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			// Refund row already gone (deleted) — nothing to resolve.
+			return nil
+		}
+		log.Printf("[SQUARE-WEBHOOK] Failed to read refund %s for parent resolution: %v", squareRefundID, err)
+		return err
+	}
+	if !strings.HasPrefix(reason, "duplicate charge — sweep replay") {
+		return nil
+	}
+	if reason == "duplicate charge — sweep replay" {
+		tag, err := db.Conn.Exec(ctx, `
+			UPDATE payments SET status = 'failed', updated_at = NOW()
+			WHERE id = $1 AND status = 'pending'
+		`, paymentID)
+		if err != nil {
+			log.Printf("[SQUARE-WEBHOOK] Failed to mark B1 parent payment %s failed: %v", paymentID, err)
+			return err
+		}
+		if tag.RowsAffected() > 0 {
+			log.Printf("[SQUARE-WEBHOOK] B1 sweep-dup refund %s COMPLETED — marked parent payment %s failed", squareRefundID, paymentID)
+		}
+		return nil
+	}
+	if idx := strings.Index(reason, "(till_sale "); idx >= 0 {
+		tillSaleID := strings.TrimSuffix(reason[idx+len("(till_sale "):], ")")
+		return clawbackOneTillSaleByID(ctx, tillSaleID)
+	}
+	log.Printf("[SQUARE-WEBHOOK] B1 sweep-dup refund %s COMPLETED but parent could not be identified from reason %q — MANUAL RECONCILIATION REQUIRED", squareRefundID, reason)
+	return nil
+}
+
+// clawbackOneTillSaleByID loads a pending till sale by id and resolves it like
+// a definitively failed charge: a gift-card sale has its funding reverted
+// atomically with the failed mark; a sale with no gift card is only marked
+// failed. Shares clawbackOneTillSale with clawbackFailedTillSales so the B1
+// parent resolution and the failed-payment clawback can never drift.
+func clawbackOneTillSaleByID(ctx context.Context, saleID string) error {
+	var (
+		itemType    string
+		itemID      sql.NullString
+		totalAmount float64
+		redeemedBy  sql.NullString
+		isCreate    *bool
+	)
+	err := db.Conn.QueryRow(ctx, `
+		SELECT ts.item_type, ts.item_id, ts.total_amount, gc.redeemed_by,
+		       (ts.created_at = gc.created_at) AS is_create
+		FROM till_sales ts
+		LEFT JOIN gift_cards gc ON gc.id = ts.item_id
+		WHERE ts.id = $1
+	`, saleID).Scan(&itemType, &itemID, &totalAmount, &redeemedBy, &isCreate)
+	if err != nil {
+		log.Printf("[SQUARE-WEBHOOK] Failed to load till sale %s for B1 parent clawback: %v", saleID, err)
+		return err
+	}
+	return clawbackOneTillSale(ctx, saleID, itemType, itemID, totalAmount, redeemedBy, isCreate)
+}
+
 // truncateDisputeReason caps a Square dispute reason at the disputes.reason
 // VARCHAR(192) column width. An over-long reason would fail the disputes
 // INSERT; the handler treats that as a dispatch error (no dedup row, 5xx), so

backend/handlers/webhooks/webhooks_state_test.go

@@ -38,13 +38,21 @@ func createWebhookTestPayment(t *testing.T, squarePaymentID, status string) stri
 }
 
 func createWebhookTestRefund(t *testing.T, paymentID, squareRefundID, status string) string {
+	t.Helper()
+	return createWebhookTestRefundWithReason(t, paymentID, squareRefundID, status, "webhook test refund")
+}
+
+// createWebhookTestRefundWithReason is createWebhookTestRefund with an explicit
+// reason — the B1 sweep-dup parent-resolution tests need the
+// "duplicate charge — sweep replay" reason to exercise finding 1.
+func createWebhookTestRefundWithReason(t *testing.T, paymentID, squareRefundID, status, reason string) string {
 	t.Helper()
 	var id string
 	err := db.Conn.QueryRow(context.Background(), `
 		INSERT INTO refunds (payment_id, amount, reason, status, square_refund_id, created_at)
-		VALUES ($1, 5.00, 'webhook test refund', $3, $2, NOW())
+		VALUES ($1, 5.00, $4, $3, $2, NOW())
 		RETURNING id
-	`, paymentID, squareRefundID, status).Scan(&id)
+	`, paymentID, squareRefundID, status, reason).Scan(&id)
 	if err != nil {
 		t.Fatalf("failed to create webhook test refund: %v", err)
 	}
@@ -1289,6 +1297,176 @@ func TestWebhook_RefundUpdated_NonTerminal_LeavesPending(t *testing.T) {
 	}
 }
 
+// TestWebhook_RefundUpdated_Approved_IsNonTerminal locks the webhook-only
+// APPROVED override (finding 2): an APPROVED Square refund is still in flight
+// and may settle COMPLETED or FAILED afterwards, so the webhook must leave the
+// local row 'pending' — NOT promote it to 'completed' the way the synchronous
+// refund handlers resolve a blocking APPROVED result. A later FAILED event
+// must then be able to demote it; promoting on APPROVED would make that
+// demotion a no-op (the FAILED path only demotes 'pending' rows) and the
+// over-refund guard would count money that never actually moved.
+func TestWebhook_RefundUpdated_Approved_IsNonTerminal(t *testing.T) {
+	const (
+		squarePaymentID = "sqp_refund_pay_approved"
+		squareRefundID  = "sqr_updated_approved"
+	)
+	payID := createWebhookTestPayment(t, squarePaymentID, "completed")
+	refundID := createWebhookTestRefund(t, payID, squareRefundID, "pending")
+
+	approved := SquareWebhookEvent{
+		Type:      "refund.updated",
+		EventID:   "evt_refund_updated_approved_1",
+		CreatedAt: "2025-01-01T00:00:00Z",
+		Data: json.RawMessage(`{
+			"type": "refund",
+			"id": "` + squareRefundID + `",
+			"object": {
+				"refund": {
+					"id": "` + squareRefundID + `",
+					"status": "APPROVED",
+					"payment_id": "` + squarePaymentID + `"
+				}
+			}
+		}`),
+	}
+	w := deliverWebhook(t, approved)
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200 on APPROVED, got %d: %s", w.Code, w.Body.String())
+	}
+	if got := getRefundStatus(t, refundID); got != "pending" {
+		t.Fatalf("expected APPROVED to leave the refund 'pending', got %q", got)
+	}
+
+	// A later FAILED event (Square declined the refund) must demote the still-
+	// pending row — the exact transition promoting on APPROVED would have broken.
+	failed := SquareWebhookEvent{
+		Type:      "refund.updated",
+		EventID:   "evt_refund_updated_approved_fail_1",
+		CreatedAt: "2025-01-01T00:00:01Z",
+		Data: json.RawMessage(`{
+			"type": "refund",
+			"id": "` + squareRefundID + `",
+			"object": {
+				"refund": {
+					"id": "` + squareRefundID + `",
+					"status": "FAILED",
+					"payment_id": "` + squarePaymentID + `"
+				}
+			}
+		}`),
+	}
+	w2 := deliverWebhook(t, failed)
+	if w2.Code != http.StatusOK {
+		t.Fatalf("expected 200 on FAILED after APPROVED, got %d: %s", w2.Code, w2.Body.String())
+	}
+	if got := getRefundStatus(t, refundID); got != "failed" {
+		t.Errorf("expected the APPROVED-then-FAILED refund to be demoted to 'failed', got %q", got)
+	}
+}
+
+// TestWebhook_RefundUpdated_Completed_SweepDupResolvesParent locks finding 1:
+// a COMPLETED webhook for a B1 sweep auto-refund of a replay-induced duplicate
+// charge (reason "duplicate charge — sweep replay") must ALSO resolve the
+// parent payment row — the B1 re-poll pass (sweepPendingB1Refunds, refunds.go)
+// only queries refunds rows still 'pending', so once the webhook promotes this
+// row to 'completed' the re-poll can never resolve the parent again. A
+// still-pending parent would let the stale-pending sweep re-replay the expired
+// idempotency key each run, minting a NEW charge (HIGH). The parent payment
+// must be marked failed by the same webhook that promoted the refund.
+func TestWebhook_RefundUpdated_Completed_SweepDupResolvesParent(t *testing.T) {
+	const (
+		squarePaymentID = "sqp_refund_sweepdup_parent"
+		squareRefundID  = "sqr_sweepdup_parent"
+	)
+	// The parent is a still-PENDING payment row (the sweep-failed row the
+	// duplicate was minted for). The refund is attached to it with the B1
+	// sweep-dup reason.
+	payID := createWebhookTestPayment(t, squarePaymentID, "pending")
+	refundID := createWebhookTestRefundWithReason(t, payID, squareRefundID, "pending", "duplicate charge — sweep replay")
+
+	event := SquareWebhookEvent{
+		Type:      "refund.updated",
+		EventID:   "evt_refund_sweepdup_parent_1",
+		CreatedAt: "2025-01-01T00:00:00Z",
+		Data: json.RawMessage(`{
+			"type": "refund",
+			"id": "` + squareRefundID + `",
+			"object": {
+				"refund": {
+					"id": "` + squareRefundID + `",
+					"status": "COMPLETED",
+					"payment_id": "` + squarePaymentID + `"
+				}
+			}
+		}`),
+	}
+	w := deliverWebhook(t, event)
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+	if got := getRefundStatus(t, refundID); got != "completed" {
+		t.Errorf("expected sweep-dup refund 'completed', got %q", got)
+	}
+	if got := getPaymentStatus(t, payID); got != "failed" {
+		t.Errorf("expected the sweep-dup refund's parent payment to be resolved to 'failed', got %q", got)
+	}
+}
+
+// TestWebhook_RefundUpdated_Completed_SweepDupResolvesTillSale locks the
+// till_sale branch of finding 1: a COMPLETED webhook for a B1 sweep-dup refund
+// whose reason carries "(till_sale <id>)" must claw back the till sale's funded
+// gift card and mark the sale failed — mirroring the sweep's re-poll resolution.
+func TestWebhook_RefundUpdated_Completed_SweepDupResolvesTillSale(t *testing.T) {
+	const squareRefundID = "sqr_sweepdup_tillsale"
+	saleID, giftCardID := createWebhookTestGiftCardAndSale(t, "sqp_sweepdup_tillsale_pay", "2025-01-01T00:00:00Z", "2025-01-01T00:00:00Z", 40.00)
+
+	// A synthetic completed payments row anchors the refund (mirrors
+	// recordSweepDuplicateRefundRow); the till_sale id lives in the reason.
+	adminID, err := fixtures.CreateTestAdminUser(db.Conn)
+	if err != nil {
+		t.Fatalf("failed to create admin for sweep-dup till sale: %v", err)
+	}
+	var payID string
+	if err := db.Conn.QueryRow(context.Background(), `
+		INSERT INTO payments (payment_type, payment_method, status, amount, created_by, created_at)
+		VALUES ('full', 'in_person_card', 'completed', 40.00, $1, NOW())
+		RETURNING id
+	`, adminID).Scan(&payID); err != nil {
+		t.Fatalf("failed to create synthetic payment for sweep-dup till sale: %v", err)
+	}
+	refundID := createWebhookTestRefundWithReason(t, payID, squareRefundID, "pending", "duplicate charge — sweep replay (till_sale "+saleID+")")
+
+	event := SquareWebhookEvent{
+		Type:      "refund.updated",
+		EventID:   "evt_refund_sweepdup_tillsale_1",
+		CreatedAt: "2025-01-01T00:00:00Z",
+		Data: json.RawMessage(`{
+			"type": "refund",
+			"id": "` + squareRefundID + `",
+			"object": {
+				"refund": {
+					"id": "` + squareRefundID + `",
+					"status": "COMPLETED",
+					"payment_id": "sqp_sweepdup_tillsale_pay"
+				}
+			}
+		}`),
+	}
+	w := deliverWebhook(t, event)
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+	if got := getRefundStatus(t, refundID); got != "completed" {
+		t.Errorf("expected sweep-dup refund 'completed', got %q", got)
+	}
+	if got := getTillSaleStatus(t, saleID); got != "failed" {
+		t.Errorf("expected the sweep-dup refund's till sale to be marked 'failed', got %q", got)
+	}
+	if exists := giftCardExists(t, giftCardID); exists {
+		t.Error("expected the created gift card to be deleted by the till-sale clawback")
+	}
+}
+
 // TestWebhook_RefundUpdated_DoesNotDemoteCompleted guards the FAILED
 // transition: a completed refund must never be demoted to 'failed' by a late
 // webhook, since the over-refund guard counts 'completed' refunds — demoting

backend/internal/adminnotify/adminnotify.go

@@ -0,0 +1,77 @@
+// Package adminnotify owns the shared flood cap for the DB-backed admin
+// notification centre (admin_notifications). That table is the single
+// operator's ONLY pager for money events, so every site that inserts an
+// operator-facing alert must bound its unacknowledged queue — a hostile flood
+// (attacker-registered accounts triggering refresh_token_reuse / reissue-fail /
+// webhook alerts) must not be able to bury the notification centre under rows
+// the operator can never work through.
+//
+// Coordination contract (Round 2 Loop B finding 1): the cap is applied
+// atomically at every insert site in this codebase:
+//
+//   - handlers/payments/twofa.go — the reissue-fail alert (per-issue capped,
+//     see finding 2; NOT globally capped).
+//   - auth/jwt.go VerifyRefreshToken — the 'refresh_token_reuse' alert.
+//   - handlers/webhooks/square.go — the three critical_payment_log inserts
+//     (dispute, booking, unknown-event, orphan-replay).
+//   - handlers/user/account.go InsertSquareErasureCriticalNotification.
+//
+// Sites owned by OTHER agents that still need the fold (coordination notes):
+//
+//   - handlers/payments/sweep.go:1556 insertCriticalPaymentNotification (money
+//     agent) — its INSERT ... SELECT ... WHERE NOT EXISTS is the same
+//     unbounded-across-accounts shape; fold `AND (SELECT COUNT(*) FROM
+//     admin_notifications _an WHERE _an.reason = 'critical_payment_log' AND
+//     _an.acknowledged_at IS NULL) < $N` (N = MaxUnacknowledgedCriticalLogs)
+//     into its WHERE clause.
+//   - handlers/scheduling/time-blockers.go:511 insertSquareCleanupCriticalNotification
+//     and internal/jobs/cleanup.go:333 ScanCriticalPaymentLogs — the same
+//     'critical_payment_log' insert shape on the GDPR-cleanup and log-scan
+//     paths (owner: the jobs/scheduling agent).
+//   - main.go has NO admin_notifications insert sites (it only mounts the
+//     notification read/ack routes), so nothing to cap there.
+//
+// Every site folds the cap INTO its INSERT (a conditional
+// `INSERT ... SELECT ... WHERE (SELECT COUNT(*) ...) < $cap`) so the
+// count-then-insert is ATOMIC — closing the TOCTOU where two concurrent
+// inserts both read a below-cap count and overshoot together (finding 2).
+package adminnotify
+
+import (
+	"context"
+	"log"
+
+	"crussell/db"
+)
+
+// MaxUnacknowledgedCriticalLogs is the GLOBAL cap on unacknowledged
+// admin_notifications rows for one reason (named after the money-critical
+// reason 'critical_payment_log' that the cap exists to protect). Once the
+// unacknowledged queue for a reason reaches the cap, further inserts for that
+// reason are dropped (with a suppression log for operator visibility) until
+// the operator acknowledges outstanding rows. 100 is far beyond anything a
+// single salon produces legitimately, so it only ever suppresses an abnormal
+// flood.
+const MaxUnacknowledgedCriticalLogs = 100
+
+// CriticalLogsCapExceeded reports whether the unacknowledged admin-notification
+// queue for reason has reached MaxUnacknowledgedCriticalLogs. q routes through
+// the caller's transaction when one is active (the ctx-routed db.Conn proxy, or
+// an explicit pgx.Tx).
+//
+// Best-effort and fail-OPEN: a count error is logged and false is returned, so
+// a money alert is never dropped because the count query failed (the insert's
+// own atomic cap condition below still guards the row in that case — the
+// pre-check only decides whether to log a suppression).
+func CriticalLogsCapExceeded(ctx context.Context, q db.Querier, reason string) bool {
+	var n int
+	err := q.QueryRow(ctx, `
+		SELECT COUNT(*) FROM admin_notifications
+		WHERE reason = $1::admin_notification_reason AND acknowledged_at IS NULL
+	`, reason).Scan(&n)
+	if err != nil {
+		log.Printf("adminnotify: failed to count unacknowledged %s admin notifications: %v", reason, err)
+		return false
+	}
+	return n >= MaxUnacknowledgedCriticalLogs
+}

backend/internal/twofa/twofa.go

@@ -143,6 +143,27 @@ func (st *AttemptState) SetLastActive(t time.Time) {
 	st.LastAt.Store(t.UnixNano())
 }
 
+// SetLastMintAtLocked records the per-user mint-cooldown stamp. The caller
+// MUST already hold st.Mu (matching how the stamp is read by
+// twoFAMintThrottled in handlers/user and the payments re-issue cooldown).
+//
+// Round 2 Loop B finding 3a: writing to the SHARED saturated state is a
+// NO-OP. saturatedLockedState is returned by StateFor for EVERY untracked user
+// once the map is at capacity, so a mint stamped on it would throttle every
+// untracked user for the whole cooldown (one user's mint blocks everyone for
+// 60s) and ClearMintCooldownForUser would clear it for all of them. The
+// singleton's stamp therefore stays permanently zeroed: under saturation,
+// per-user mints are unthrottled, which is SAFE because a mint never grants a
+// fresh guessing budget (B11b) and the saturated state is already permanently
+// locked out for verification. The stamp must also never be written by the
+// reissue/mint paths when st IS the singleton — the no-op below guarantees it.
+func (st *AttemptState) SetLastMintAtLocked(t time.Time) {
+	if st == saturatedLockedState {
+		return
+	}
+	st.LastMintAt = t
+}
+
 // LockedOut reports whether the state is inside its lockout window: the attempt
 // counter has reached the cap and the window has not yet elapsed. Such a record
 // is the rate limit's source of truth for its user and must never be evicted
@@ -199,9 +220,14 @@ func StateFor(userID string) *AttemptState {
 				delete(Map, id)
 				continue
 			}
-			if st.LockedOut(now) {
+			if st.LockedOut(now) || st.Count.Load() > 0 {
-				// Inside its lockout window — the rate limit's source of truth
+				// Round 2 Loop B finding 3b: an in-window record with a
-				// for this user. Never evict (finding-e fix).
+				// NON-ZERO attempt counter is the rate limit's IN-PROGRESS
+				// state for a genuine user (a locked-out record, or a user
+				// mid-window with failed attempts banked). Evicting it would
+				// silently reset the counter and grant a fresh guessing
+				// budget. Only count==0 in-window records (fresh lookups /
+				// idle mint-cooldown stamps) are evictable.
 				continue
 			}
 			if at := st.LastActive(); oldestID == "" || at.Before(oldestAt) {
@@ -212,18 +238,30 @@ func StateFor(userID string) *AttemptState {
 			delete(Map, oldestID)
 		}
 		if len(Map) >= MaxTrackedAttempts {
-			// Every entry is a locked-out in-window record. Do not evict one
+			// Every entry is a protected in-window record (locked out, or
-			// (that would reset its rate limit) and do not grow past the cap:
+			// carrying an in-progress counter). Do not evict one (that would
-			// return the SHARED permanently-locked state (finding 3, Round 2
+			// reset its rate limit) and do not grow past the cap: return the
-			// Loop A). Previously a fresh transient state was returned per
+			// SHARED permanently-locked state (finding 3, Round 2 Loop A).
-			// call, so every untracked user received a fresh 5-guess budget
+			// Previously a fresh transient state was returned per call, so
-			// per request — silently disabling the brute-force lockout exactly
+			// every untracked user received a fresh 5-guess budget per
+			// request — silently disabling the brute-force lockout exactly
 			// under the hostile flood that saturated the map. The shared state
 			// treats every untracked user as locked out instead. It is never
 			// stored in Map (so the eviction scan / ResetAttempts /
 			// DeleteAttempts never touch it) and self-heals: as soon as one of
 			// the real locked-out records lapses out of its window, StateFor
 			// evicts it and normal per-user tracking resumes.
+			//
+			// Round 2 Loop B finding 3c — ACCEPTED RESIDUAL: an attacker can
+			// still fill the map with up to MaxTrackedAttempts (~10k)
+			// in-window locked-out records, forcing every other user into the
+			// shared saturated state. That is a bounded, FAIL-CLOSED outcome:
+			// the fallback is a locked-out-everyone state (brute force
+			// impossible, availability reduced), never a locked-out-nobody one.
+			// Mint cooldowns are unthrottled under saturation (the shared
+			// stamp is zeroed — see SetLastMintAtLocked), which is safe
+			// because a mint grants no guessing budget (B11b). The map drains
+			// as locked-out windows lapse.
 			return saturatedLockedState
 		}
 	}
@@ -492,13 +530,26 @@ func ConsumePendingCode(ctx context.Context, q db.Querier, userID string) error
 }
 
 // ClearMintCooldownForUser zeroes the user's mint-cooldown stamp (LastMintAt)
-// under the per-user mutex — LastMintAt is only ever touched under Mu. Exported
+// under the per-user mutex — LastMintAt is only ever touched under Mu. A no-op
-// so the payments re-issue path's coordination contract is actionable (Round 2
+// when the user's state IS the shared saturated singleton (Round 2 Loop B
-// Loop A finding 2): a FRESH-charge terminal-success path that consumed the
+// finding 3a: the shared stamp must not be cleared for every untracked user by
-// code at the gate (consume=true, so ConsumePendingCode is not called) can call
+// one user's terminal success).
-// this to re-arm immediate re-minting after a completed charge.
+//
+// Round 2 Loop B finding 6a — COORDINATION CONTRACT (money agent): the FRESH
+// saved-card charge path consumes the customer's 2FA code AT THE GATE
+// (consume=true), so twofa.ConsumePendingCode is NOT called on its terminal
+// success and the mint-cooldown stamp survives — a customer who completes a
+// fresh charge within 60s of their last code mint and immediately requests a
+// new code gets 429 for the rest of the window. The money agent's fresh-charge
+// terminal-success path in handlers/payments/handlers.go should call
+// ClearMintCooldownForUser(userID) at the same point a completed charge is
+// recorded, so a just-completed charge re-arms immediate re-minting. This
+// function is the exported, coordination-actionable entry point for that call.
 func ClearMintCooldownForUser(userID string) {
 	st := StateFor(userID)
+	if st == saturatedLockedState {
+		return
+	}
 	st.Mu.Lock()
 	st.LastMintAt = time.Time{}
 	st.Mu.Unlock()

backend/internal/twofa/twofa_test.go

@@ -223,3 +223,83 @@ func TestConsumePendingCode_ClearsMintCooldownStamp(t *testing.T) {
 	defer st.Mu.Unlock()
 	require.True(t, st.LastMintAt.IsZero(), "terminal-success consumption must clear the mint-cooldown stamp (finding 2)")
 }
+
+// TestStateFor_SaturatedMintStampIsNoOp pins Round 2 Loop B finding 3a: the
+// SHARED saturated state must never carry a per-user mint-cooldown stamp.
+// StateFor returns the package singleton to every untracked user once the map
+// is at capacity, so a mint stamped on it would throttle all of them for the
+// whole cooldown (one user's mint blocks everyone for 60s) and
+// ClearMintCooldownForUser would clear it for everyone. The no-op keeps the
+// shared stamp permanently zeroed.
+func TestStateFor_SaturatedMintStampIsNoOp(t *testing.T) {
+	t.Cleanup(func() {
+		MapMu.Lock()
+		Map = make(map[string]*AttemptState)
+		MaxTrackedAttempts = 10_000
+		MapMu.Unlock()
+	})
+
+	MapMu.Lock()
+	Map = make(map[string]*AttemptState)
+	MaxTrackedAttempts = 1
+	MapMu.Unlock()
+
+	now := clock.Now()
+	MapMu.Lock()
+	victim := &AttemptState{}
+	victim.SetLastActive(now)
+	victim.Count.Store(MaxAttempts) // in-window locked-out — protected from eviction
+	Map["victim"] = victim
+	MapMu.Unlock()
+
+	st := StateFor("untracked") // saturated — shared permanently-locked state
+	require.Same(t, st, saturatedLockedState, "a saturated map must return the shared permanently-locked state")
+
+	st.SetLastMintAtLocked(clock.Now())
+	require.True(t, st.LastMintAt.IsZero(), "a mint stamp written to the saturated state must be a no-op (cross-user throttle)")
+
+	ClearMintCooldownForUser("untracked")
+	require.True(t, st.LastMintAt.IsZero(), "clearing the cooldown for one saturated user must not touch the shared stamp")
+}
+
+// TestStateFor_NeverEvictsInWindowCounter pins Round 2 Loop B finding 3b: the
+// cap-driven eviction must never drop an in-window record carrying a NON-ZERO
+// attempt counter — a genuine user mid-window with failed attempts banked.
+// Evicting it would silently reset the counter and grant a fresh guessing
+// budget, so only count==0 in-window records (idle mint-cooldown stamps / fresh
+// lookups) are evictable. When every in-window record is protected, a new key
+// falls back to the shared saturated state instead.
+func TestStateFor_NeverEvictsInWindowCounter(t *testing.T) {
+	t.Cleanup(func() {
+		MapMu.Lock()
+		Map = make(map[string]*AttemptState)
+		MaxTrackedAttempts = 10_000
+		MapMu.Unlock()
+	})
+
+	MapMu.Lock()
+	Map = make(map[string]*AttemptState)
+	MaxTrackedAttempts = 2
+	MapMu.Unlock()
+
+	now := clock.Now()
+	for _, id := range []string{"genuine_a", "genuine_b"} {
+		st := &AttemptState{}
+		st.SetLastActive(now)
+		st.Count.Store(2) // in-progress counter, NOT locked out
+		Map[id] = st
+	}
+	MapMu.Lock()
+	require.Len(t, Map, 2)
+	MapMu.Unlock()
+
+	st := StateFor("new_user")
+	require.True(t, st.LockedOut(clock.Now()), "with every in-window record protected, a new key must fall back to the shared locked state")
+
+	MapMu.Lock()
+	defer MapMu.Unlock()
+	require.Len(t, Map, 2, "in-window records with count>0 must never be evicted (finding 3b)")
+	for _, id := range []string{"genuine_a", "genuine_b"} {
+		require.NotNil(t, Map[id], "%s must survive cap pressure", id)
+	}
+}

backend/mw/ratelimit.go

@@ -102,14 +102,16 @@ func (prl *ProgressiveRateLimiter) Check(ip string) (delayMs int) {
 	}
 }
 
-// maxProgressiveSleepDelayMs is the largest delay the progressive per-IP
+// progressiveRejectDelayMs is the delay at which the progressive per-IP limiter
-// limiter still absorbs by sleeping. Beyond it the request is rejected 429
+// stops sleeping and rejects the request 429 immediately (Round 2 Loop B
-// immediately instead (Round 2 Loop A finding 4a): sleeping 5-10s ties up a
+// finding 5). ONLY the TOP abuse tier (10s) rejects: the 500ms / 2s / 5s tiers
-// goroutine per throttled request while the client keeps hammering, so one
+// keep sleeping (backoff). Previously every tier past 2s hard-rejected, which
-// client can stack many sleeping goroutines in front of the bcrypt wall on
+// under a shared NAT — or any TRUST_PROXY_HEADERS=false deployment where every
-// /login and /register. The small progressive tiers (500ms / 2s) are
+// client collapses onto the proxy's IP — locked out the whole surface behind
-// unchanged.
+// one abusive client. Now a moderate sustained rate still sleeps (throttling
-const maxProgressiveSleepDelayMs = 2000
+// the offender with backoff) instead of hard-rejecting everyone, while the 10s
+// abuse tier keeps the goroutine-parking amplifier bound.
+const progressiveRejectDelayMs = 10000
 
 func ProgressiveRateLimit(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
@@ -117,10 +119,10 @@ func ProgressiveRateLimit(next http.Handler) http.Handler {
 
 		delay := globalProgressiveLimiter.Check(ip)
 		switch {
-		case delay > maxProgressiveSleepDelayMs:
+		case delay >= progressiveRejectDelayMs:
-			// Far past the sustained budget — reject now instead of parking a
+			// Top abuse tier only — far past the sustained budget, reject now
-			// goroutine for 5-10s. The rejection is a clean 429; the client
+			// instead of parking a goroutine for 10s. The rejection is a clean
-			// retries after the burst window lapses.
+			// 429; the client retries after the burst window lapses.
 			RespondJSON(w, http.StatusTooManyRequests, map[string]string{"error": "Rate limit exceeded"})
 			return
 		case delay > 0:

backend/mw/ratelimit_test.go

@@ -652,12 +652,14 @@ func TestProgressiveRateLimiter_DelayEscalatesWithSustainedRate(t *testing.T) {
 	}
 }
 
-// TestProgressiveRateLimit_RejectsBeyondSleepCap pins finding 4a: once the
+// TestProgressiveRateLimit_RejectsOnlyTopTier pins finding 4a + Round 2 Loop B
-// computed delay exceeds maxProgressiveSleepDelayMs (2s), the middleware
+// finding 5: ONLY the top 10s abuse tier rejects the request 429 immediately
-// rejects the request 429 immediately instead of sleeping a goroutine for
+// instead of sleeping a goroutine (a per-client goroutine-parking amplifier in
-// 5-10s (a per-client goroutine-parking amplifier in front of bcrypt). The
+// front of bcrypt); the 500ms / 2s / 5s tiers keep sleeping (backoff). Before
-// small progressive tiers (500ms / 2s) still sleep.
+// finding 5 every tier past 2s hard-rejected, which under a shared NAT /
-func TestProgressiveRateLimit_RejectsBeyondSleepCap(t *testing.T) {
+// TRUST_PROXY_HEADERS=false deployment locked out the whole surface behind one
+// abusive client.
+func TestProgressiveRateLimit_RejectsOnlyTopTier(t *testing.T) {
 	globalProgressiveLimiter.mu.Lock()
 	saved := globalProgressiveLimiter.requests
 	globalProgressiveLimiter.requests = make(map[string]*ipProgressiveState)
@@ -668,28 +670,48 @@ func TestProgressiveRateLimit_RejectsBeyondSleepCap(t *testing.T) {
 		globalProgressiveLimiter.mu.Unlock()
 	})
 
-	// Seed the 10s abuse tier (sustained > 300) for this IP.
+	// 5s tier (sustained 201-300): sleeps (backoff), never rejects — the NAT /
-	seedProgressiveTimestamps(t, globalProgressiveLimiter, "198.51.100.99", 31, 320)
+	// proxy-collapse case where a moderate sustained rate must not hard-lock
-
+	// the whole shared surface.
+	seedProgressiveTimestamps(t, globalProgressiveLimiter, "198.51.100.98", 31, 250)
 	nextCalled := false
 	handler := ProgressiveRateLimit(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		nextCalled = true
 		w.WriteHeader(http.StatusOK)
 	}))
-
 	req := httptest.NewRequest(http.MethodPost, "/login", nil)
-	req.RemoteAddr = "198.51.100.99:1234"
+	req.RemoteAddr = "198.51.100.98:1234"
 	w := httptest.NewRecorder()
 	start := time.Now()
 	handler.ServeHTTP(w, req)
+	if !nextCalled {
+		t.Error("the 5s tier must sleep (backoff), not reject — next handler must be called")
+	}
+	if w.Code != http.StatusOK {
+		t.Errorf("expected the 5s tier to sleep and pass through, got %d", w.Code)
+	}
+	if got := w.Header().Get("X-RateLimit-Delay"); got != "5000" {
+		t.Errorf("expected X-RateLimit-Delay=5000 for the 5s tier, got %q", got)
+	}
+	if elapsed := time.Since(start); elapsed < 4*time.Second {
+		t.Errorf("the 5s tier must actually sleep (took %s)", elapsed)
+	}
 
+	// 10s abuse tier (sustained > 300): rejects 429 immediately.
+	seedProgressiveTimestamps(t, globalProgressiveLimiter, "198.51.100.99", 31, 320)
+	nextCalled = false
+	req = httptest.NewRequest(http.MethodPost, "/login", nil)
+	req.RemoteAddr = "198.51.100.99:1234"
+	w = httptest.NewRecorder()
+	start = time.Now()
+	handler.ServeHTTP(w, req)
 	if nextCalled {
-		t.Error("next handler must NOT be called when the delay exceeds the sleep cap")
+		t.Error("next handler must NOT be called at the 10s abuse tier")
 	}
 	if w.Code != http.StatusTooManyRequests {
-		t.Errorf("expected 429, got %d", w.Code)
+		t.Errorf("expected 429 at the 10s abuse tier, got %d", w.Code)
 	}
 	if elapsed := time.Since(start); elapsed >= 5*time.Second {
-		t.Errorf("the 5-10s tiers must reject immediately, not sleep (took %s)", elapsed)
+		t.Errorf("the 10s tier must reject immediately, not sleep (took %s)", elapsed)
 	}
 }

frontend/src/lib/components/admin/BookingModal.svelte

@@ -856,9 +856,13 @@
 									{apptHours > 72
 										? "Over 72 hours' notice means no deposit protection applies — a full refund is given regardless."
 										: apptHours >= 24
-											? "Between 24–72 hours' notice, up to 50% of the total (" +
+											? "Between 24–72 hours' notice, up to " +
+												POLICY.PROTECTED_DEPOSIT_MAX_PCT * 100 +
+												'% of the total (' +
 												'£' +
-												(selectedBooking.total_amount * 0.5).toFixed(2) +
+												(selectedBooking.total_amount * POLICY.PROTECTED_DEPOSIT_MAX_PCT).toFixed(
+													2
+												) +
 												') is treated as a protected deposit to cover the lost slot. The remaining balance above that is refunded.'
 											: "Under 24 hours' notice, the full amount paid (" +
 												'£' +

frontend/src/lib/components/admin/EditBookingModal.svelte

@@ -5,6 +5,7 @@
 	import { formatDuration } from '$lib/utils/format';
 	import { formatUserName } from '$lib/utils/nameDisplay';
 	import { parseWallClockDate } from '$lib/utils/timeSlots';
+	import { generateUUID } from '$lib/utils/uuid';
 	import * as Modal from '$lib/components/ui/dialog';
 	import * as AlertDialog from '$lib/components/ui/alert-dialog';
 	import { Button } from '$lib/components/ui/button';
@@ -353,7 +354,7 @@
 		// Unique per refund attempt so two equal partial refunds of the same
 		// payment don't collide on the backend's amount-derived key; reused on
 		// retry (the backend dedups on it) so a timeout can't double-refund.
-		refundIdempotencyKey = crypto.randomUUID();
+		refundIdempotencyKey = generateUUID();
 		showRefundModal = true;
 
 		// Pre-fill the refund with the RESIDUAL (payment.amount − already

frontend/src/lib/components/admin/RescheduleModal.svelte

@@ -7,6 +7,7 @@
 	import { Checkbox } from '$lib/components/ui/checkbox';
 	import PolicyPopover from '$lib/components/ui/policyPopover.svelte';
 	import { formatUserName } from '$lib/utils/nameDisplay';
+	import { POLICY } from '$lib/constants/policy';
 
 	import * as Modal from '$lib/components/ui/dialog';
 	import { Button } from '$lib/components/ui/button';
@@ -446,8 +447,9 @@
 							<summary class="cursor-pointer hover:text-gray-700">What this means</summary>
 							<p class="mt-1">
 								"Rescheduling within {Math.round(hoursUntilAppointment)}h of the original time with
-								payments present means deposit protection applies — up to 50% of the total (up to £{(
+								payments present means deposit protection applies — up to {POLICY.PROTECTED_DEPOSIT_MAX_PCT *
-									booking.total_amount * 0.5
+									100}% of the total (up to £{(
+									booking.total_amount * POLICY.PROTECTED_DEPOSIT_MAX_PCT
 								).toFixed(2)}) could be retained depending on notice period."
 							</p>
 						</details>

frontend/src/lib/components/booking/BookingFlow.svelte

@@ -327,7 +327,7 @@
 	}
 
 	function calculateDepositAmount(): number {
-		return Math.round(getTotalPrice() * 0.2 * 100) / 100;
+		return Math.round(getTotalPrice() * POLICY.REQUIRED_DEPOSIT_PCT * 100) / 100;
 	}
 
 	async function fetchDiscountPreview() {
@@ -2607,8 +2607,8 @@
 										</div>
 										<h3 class="text-lg font-semibold text-emerald-800">Deposit Paid</h3>
 										<p class="mt-1 text-emerald-700">
-											Your deposit of <strong>{formatCurrency(calculateDepositAmount())}</strong> has been
+											Your deposit of <strong>{formatCurrency(calculateDepositAmount())}</strong> has
-											paid successfully. See you at your appointment!
+											been paid successfully. See you at your appointment!
 										</p>
 									</div>
 								{:else if depositRequired}

frontend/src/lib/components/payments/PaymentModal.svelte

@@ -12,6 +12,7 @@
 	import {
 		CARD_VERIFICATION_RETRY_MESSAGE,
 		campaignDiscountPence,
+		isOverflowTipConfirmationRequired,
 		isTwoFactorVerificationGateFailure,
 		isVerificationRequiredSignal,
 		PAYMENT_METHOD_SAVED_CARD,
@@ -26,10 +27,10 @@
 	} from '$lib/square/square';
 	import { authStore } from '$lib/stores/auth.svelte';
 	import TwoFactorCodeInput from '$lib/components/payments/TwoFactorCodeInput.svelte';
+	import OverflowTipConfirm from '$lib/components/payments/OverflowTipConfirm.svelte';
 	import { useTwoFactorCodeForSavedCard } from '$lib/stores/twoFactorCode.svelte';
 	import { generateUUID } from '$lib/utils/uuid';
-
+	import { POLICY } from '$lib/constants/policy';
-	const LOYALTY_DISCOUNT_RATE = 0.1;
 
 	interface Props {
 		booking: Booking;
@@ -62,7 +63,7 @@
 		amount: number;
 	};
 
-	type PaymentMethod = 'card' | 'cash' | 'giftcard' | (typeof PAYMENT_METHOD_SAVED_CARD) | null;
+	type PaymentMethod = 'card' | 'cash' | 'giftcard' | typeof PAYMENT_METHOD_SAVED_CARD | null;
 
 	let status = $state<PaymentStatus>('idle');
 	let selectedMethod = $state<PaymentMethod>(null);
@@ -75,6 +76,65 @@
 	// reactive flag is checked synchronously at the start of every handler.
 	let isProcessingPaymentSync = false;
 
+	// Overpayment confirmation (mirrors UserPaymentModal/BookingFlow). The
+	// backend rejects a payment that exceeds the booking's remaining balance
+	// unless the request carries `confirm_overflow_tip: true` — a tip is
+	// gratuity for service already rendered. The guard fires on STALE booking
+	// data (multi-tab, admin-changed totals) where the operator would otherwise
+	// be stuck with an unresolvable 400; the rejected request body is parked
+	// here and a Confirm/Cancel prompt is shown, with Confirm resending the SAME
+	// body plus the flag.
+	let overflowConfirm = $state<{
+		amountPence: number;
+		overflowPence: number;
+		body: Record<string, unknown>;
+	} | null>(null);
+
+	function confirmOverflowPayment() {
+		const pending = overflowConfirm;
+		if (!pending || status === 'saved-card-processing') return;
+		status = 'saved-card-processing';
+		error = null;
+		isProcessingPaymentSync = true;
+		apiFetch(`/api/admin/bookings/${booking.id}/payment`, {
+			method: 'POST',
+			headers: { 'Content-Type': 'application/json' },
+			body: JSON.stringify({ ...pending.body, confirm_overflow_tip: true })
+		})
+			.then(async (response) => {
+				if (!response.ok) {
+					const errData = await response.text();
+					throw new Error(extractErrorMessage(errData) || 'Failed to process payment');
+				}
+				const data = await response.json();
+				status = 'success';
+				paymentResult = {
+					checkout_id: data.payment_id || data.checkout_id || data.id || '',
+					status: 'COMPLETED',
+					card_brand: data.card_brand,
+					last4: data.card_last4,
+					amount: data.amount
+				};
+				overflowConfirm = null;
+				toast.success('Payment successful');
+				onComplete(paymentResult);
+			})
+			.catch((_err) => {
+				status = 'error';
+				error = _err instanceof Error ? _err.message : 'Failed to process payment';
+				toast.error(error ?? 'Unknown error');
+			})
+			.finally(() => {
+				isProcessingPaymentSync = false;
+			});
+	}
+
+	function cancelOverflowConfirmation() {
+		overflowConfirm = null;
+		status = 'idle';
+		selectedMethod = null;
+	}
+
 	// B6/B10: charging a customer's saved card requires the customer's current
 	// 2FA verification code when the backend enforces the gate. The backend keys
 	// on the CARD OWNER (the booking's user), so the input is surfaced whenever
@@ -168,7 +228,7 @@
 	);
 
 	const loyaltyDiscount = $derived(
-		useLoyalty ? Math.round(booking.total_amount * 100 * LOYALTY_DISCOUNT_RATE) : 0
+		useLoyalty ? Math.round(booking.total_amount * 100 * POLICY.LOYALTY_DISCOUNT_RATE) : 0
 	);
 
 	// Campaign discount preview — fetched on mount, mirroring the customer flow
@@ -324,11 +384,10 @@
 
 	const tipPercentages = $derived.by(() => {
 		if (netTotal <= 0) return [];
-		return [
+		return POLICY.TIP_PRESET_PCTS.map((pct) => ({
-			{ pct: 10, amount: Math.round(netTotal * 0.1 * 100) / 100 },
+			pct,
-			{ pct: 15, amount: Math.round(netTotal * 0.15 * 100) / 100 },
+			amount: Math.round(netTotal * (pct / 100) * 100) / 100
-			{ pct: 20, amount: Math.round(netTotal * 0.2 * 100) / 100 }
+		}));
-		];
 	});
 
 	const tipMultiplier = $derived(
@@ -404,6 +463,24 @@
 
 			if (!response.ok) {
 				const errData = await response.text();
+				// Overflow guard (defensive — the admin terminal path currently
+				// clamps instead, but a 400 carrying the code must surface the
+				// Confirm/Cancel prompt like the customer modal, not a dead-end).
+				if (isOverflowTipConfirmationRequired(errData)) {
+					overflowConfirm = {
+						amountPence: Math.round(finalAmount * 100) - loyaltyDiscount,
+						overflowPence: Math.max(
+							0,
+							Math.round(finalAmount * 100) - loyaltyDiscount - Math.round(netTotal * 100)
+						),
+						body: {
+							amount: Math.round(finalAmount * 100) - loyaltyDiscount,
+							payment_type: 'full',
+							tip_enabled: tipEnabled
+						}
+					};
+					return;
+				}
 				throw new Error(extractErrorMessage(errData) || 'Failed to initiate payment');
 			}
 
@@ -841,9 +918,7 @@
 			let verificationToken = '';
 			status = 'saved-card-waiting-sca';
 			try {
-				const squareCardId = savedCards.find(
+				const squareCardId = savedCards.find((c) => c.id === selectedSavedCardId)?.square_card_id;
-					(c) => c.id === selectedSavedCardId
-				)?.square_card_id;
 				const proactive = await runSavedCardSCAProactively({
 					amountPence: chargeAmount,
 					squareCardId: squareCardId ?? '',
@@ -898,6 +973,27 @@
 			if (!response.ok) {
 				responseStatus = response.status;
 				const errData = await response.text();
+				// Overflow guard: a 400 carrying the backend's
+				// `overflow_tip_confirmation_required` code means the charge
+				// exceeds the booking's remaining balance (stale data). Park the
+				// rejected request and surface the Confirm/Cancel prompt instead
+				// of a dead-end 400; Confirm resends the SAME body with the flag.
+				if (isOverflowTipConfirmationRequired(errData)) {
+					overflowConfirm = {
+						amountPence: chargeAmount,
+						overflowPence: Math.max(0, chargeAmount - Math.round(netTotal * 100)),
+						body: {
+							amount: chargeAmount,
+							payment_type: 'full',
+							payment_method: 'saved_card',
+							saved_card_id: selectedSavedCardId,
+							...(verificationToken ? { verification_token: verificationToken } : {}),
+							...(twoFactor.showInput ? { verification_code: twoFactor.code } : {}),
+							idempotency_key: savedCardIdempotencyKey
+						}
+					};
+					return;
+				}
 				// A 402 verification-required here means the fresh proactive
 				// token was stale/expired at Square — the charge did NOT land.
 				// Surface the SCA-first guidance; the operator taps Pay again and
@@ -981,7 +1077,15 @@
 	open={true}
 	onOpenChange={(open) => {
 		if (open) return;
+		// ESC/overlay while a charge is in flight must not close the modal — the
+		// charge may still land. ESC while the overflow-confirm prompt is showing
+		// dismisses the prompt (back to the amount-editing form), mirroring the
+		// customer modal, instead of closing the whole flow.
 		if (isChargeInFlight(status)) return;
+		if (overflowConfirm) {
+			cancelOverflowConfirmation();
+			return;
+		}
 		handleClose();
 	}}
 >
@@ -990,7 +1094,23 @@
 			<Dialog.Title class="text-xl font-semibold">Take Payment</Dialog.Title>
 		</Dialog.Header>
 
-		{#if status === 'idle'}
+		{#if overflowConfirm}
+			<div class="space-y-4">
+				<!-- Overpayment confirmation: the backend rejected the payment because
+				 the booking's remaining balance has changed since it was loaded
+				 (stale data). The excess over the remaining balance will be
+				 recorded as a tip once confirmed. Shared component with the
+				 customer payment modal and the booking-flow deposit step so the
+				 admin surface can't drift. -->
+				<OverflowTipConfirm
+					overflowPence={overflowConfirm.overflowPence}
+					loading={status === 'saved-card-processing'}
+					onConfirm={confirmOverflowPayment}
+					onCancel={cancelOverflowConfirmation}
+				/>
+				<Button variant="ghost" onclick={handleClose} class="w-full">Close</Button>
+			</div>
+		{:else if status === 'idle'}
 			<div class="space-y-4">
 				<div class="rounded-md border border-gray-200 bg-gray-50 p-4">
 					<div class="mb-3 text-sm font-semibold text-gray-700">Services</div>
@@ -1039,8 +1159,8 @@
 								<div class="text-sm font-medium text-fuchsia-900">Use Loyalty Stamp Card</div>
 								<div class="mt-0.5 text-xs text-fuchsia-700">
 									{Math.floor(stamps / 10)} full card{Math.floor(stamps / 10) === 1 ? '' : 's'} available
-									&middot; {Math.round(LOYALTY_DISCOUNT_RATE * 100)}% off ({formatCurrency(
+									&middot; {Math.round(POLICY.LOYALTY_DISCOUNT_RATE * 100)}% off ({formatCurrency(
-										Math.round(booking.total_amount * 100 * LOYALTY_DISCOUNT_RATE) / 100
+										Math.round(booking.total_amount * 100 * POLICY.LOYALTY_DISCOUNT_RATE) / 100
 									)})
 								</div>
 							</label>
@@ -1132,7 +1252,8 @@
 						class="flex items-center justify-between rounded-md border border-green-200 bg-green-50 p-3"
 					>
 						<span class="text-sm font-medium text-green-800">Already paid</span>
-						<span class="text-base font-bold text-green-800">{formatCurrency(amountPaidPence / 100)}</span
+						<span class="text-base font-bold text-green-800"
+							>{formatCurrency(amountPaidPence / 100)}</span
 						>
 					</div>
 				{/if}

frontend/src/lib/components/payments/TipPayment.svelte

@@ -14,6 +14,7 @@
 	import { onMount } from 'svelte';
 	import { generateUUID } from '$lib/utils/uuid';
 	import { formatCurrency } from '$lib/utils/format';
+	import { POLICY } from '$lib/constants/policy';
 	import {
 		CARD_VERIFICATION_RETRY_MESSAGE,
 		canSaveCardsForRole,
@@ -155,11 +156,10 @@
 
 	const tipPercentages = $derived.by(() => {
 		if (subtotal <= 0) return [];
-		return [
+		return POLICY.TIP_PRESET_PCTS.map((pct) => ({
-			{ pct: 10, amount: Math.round(subtotal * 0.1 * 100) / 100 },
+			pct,
-			{ pct: 15, amount: Math.round(subtotal * 0.15 * 100) / 100 },
+			amount: Math.round(subtotal * (pct / 100) * 100) / 100
-			{ pct: 20, amount: Math.round(subtotal * 0.2 * 100) / 100 }
+		}));
-		];
 	});
 
 	function formatDate(dateStr: string): string {

frontend/src/lib/components/payments/UserPaymentModal.svelte

@@ -11,6 +11,7 @@
 	import TwoFactorCodeInput from '$lib/components/payments/TwoFactorCodeInput.svelte';
 	import OverflowTipConfirm from '$lib/components/payments/OverflowTipConfirm.svelte';
 	import PolicyPopover from '$lib/components/ui/policyPopover.svelte';
+	import { POLICY } from '$lib/constants/policy';
 	import { authStore } from '$lib/stores/auth.svelte';
 	import { savedCardsStore } from '$lib/stores/savedCards.svelte';
 	import { useTwoFactorCodeForSavedCard } from '$lib/stores/twoFactorCode.svelte';
@@ -32,8 +33,6 @@
 		VERIFICATION_REQUIRED_MESSAGE
 	} from '$lib/square/square';
 
-	const LOYALTY_DISCOUNT_RATE = 0.1;
-
 	interface Props {
 		booking: Booking;
 		onClose: () => void;
@@ -223,25 +222,27 @@
 	);
 
 	const loyaltyDiscount = $derived(
-		useLoyalty ? Math.round(booking.total_amount * 100 * LOYALTY_DISCOUNT_RATE) : 0
+		useLoyalty ? Math.round(booking.total_amount * 100 * POLICY.LOYALTY_DISCOUNT_RATE) : 0
 	);
 
 	// Deposit policy warning text — dynamic based on booking state
-	const expectedDepositPercent = $derived(booking.deposit_required ? 20 : 0);
+	const expectedDepositPercent = $derived(
+		booking.deposit_required ? POLICY.REQUIRED_DEPOSIT_PCT * 100 : 0
+	);
 	const depositPolicyWarning = $derived<string | null>(
 		{
 			get text(): string | null {
 				if (!booking.deposit_required && totalPaid === 0 && booking.amount_due <= 0) return null;
 				if (booking.deposit_required) {
 					return `A ${expectedDepositPercent}% deposit (at least ${formatCurrency(
-						booking.total_amount * 0.2
+						booking.total_amount * POLICY.REQUIRED_DEPOSIT_PCT
-					)}) is required. Any payments up to 50% of total (${formatCurrency(
+					)}) is required. Any payments up to ${POLICY.PROTECTED_DEPOSIT_MAX_PCT * 100}% of total (${formatCurrency(
-						booking.total_amount * 0.5
+						booking.total_amount * POLICY.PROTECTED_DEPOSIT_MAX_PCT
 					)}) are treated as deposit for cancellations.`;
 				}
 				if (totalPaid > 0 || booking.amount_due > 0) {
-					return `Any payment up to 50% of total (${formatCurrency(
+					return `Any payment up to ${POLICY.PROTECTED_DEPOSIT_MAX_PCT * 100}% of total (${formatCurrency(
-						booking.total_amount * 0.5
+						booking.total_amount * POLICY.PROTECTED_DEPOSIT_MAX_PCT
 					)}) is treated as a protected deposit for cancellations. Paying early is at your own risk.`;
 				}
 				return null;
@@ -729,7 +730,7 @@
 		// pre-discounted deposit here would double-discount (HIGH-2).
 		const depositPence = booking.deposit_amount
 			? Math.round(booking.deposit_amount * 100)
-			: Math.round(booking.total_amount * 0.2 * 100);
+			: Math.round(booking.total_amount * POLICY.REQUIRED_DEPOSIT_PCT * 100);
 		makePayment('deposit', depositPence);
 	}
 
@@ -947,8 +948,11 @@
 							<label for="use-loyalty" class="cursor-pointer select-none">
 								<div class="text-sm font-medium text-fuchsia-900">Use my Loyalty Stamp Card</div>
 								<div class="mt-0.5 text-xs text-fuchsia-700">
-									{stamps} stamps available &middot; {Math.round(LOYALTY_DISCOUNT_RATE * 100)}% off
+									{stamps} stamps available &middot; {Math.round(
-									({formatCurrency(Math.round(booking.total_amount * 100 * LOYALTY_DISCOUNT_RATE) / 100)})
+										POLICY.LOYALTY_DISCOUNT_RATE * 100
+									)}% off ({formatCurrency(
+										Math.round(booking.total_amount * 100 * POLICY.LOYALTY_DISCOUNT_RATE) / 100
+									)})
 								</div>
 							</label>
 						</div>
@@ -1009,7 +1013,8 @@
 				<div class="space-y-2 rounded-md border border-gray-200 bg-white p-4">
 					<div class="flex justify-between text-sm">
 						<span class="text-gray-600">Total</span>
-						<span class="font-medium">{formatCurrency(Math.round(booking.total_amount * 100) / 100)}</span
+						<span class="font-medium"
+							>{formatCurrency(Math.round(booking.total_amount * 100) / 100)}</span
 						>
 					</div>
 					{#if discountPreview?.eligible}
@@ -1029,7 +1034,9 @@
 					{#if useLoyalty && loyaltyDiscount > 0}
 						<div class="flex justify-between text-sm">
 							<span class="text-gray-600">Loyalty Stamp Card (10% Off)</span>
-							<span class="font-medium text-green-700">-{formatCurrency(loyaltyDiscount / 100)}</span>
+							<span class="font-medium text-green-700"
+								>-{formatCurrency(loyaltyDiscount / 100)}</span
+							>
 						</div>
 					{/if}
 					<div class="flex justify-between border-t border-gray-200 pt-2">
@@ -1141,7 +1148,7 @@
 									depositChargePence(
 										booking.deposit_amount
 											? Math.round(booking.deposit_amount * 100)
-											: Math.round(booking.total_amount * 0.2 * 100),
+											: Math.round(booking.total_amount * POLICY.REQUIRED_DEPOSIT_PCT * 100),
 										campaignDiscountPence(discountPreview)
 									) / 100
 								)})

frontend/src/lib/constants/policy.ts

@@ -7,5 +7,14 @@ export const POLICY = {
 	RESCHEDULE_BLOCK_HOURS_WITH_PAYMENTS: 72,
 	RESCHEDULE_BLOCK_HOURS_NO_PAYMENTS: 24,
 	PROTECTED_DEPOSIT_MAX_PCT: 0.5,
-	REQUIRED_DEPOSIT_PCT: 0.2
+	REQUIRED_DEPOSIT_PCT: 0.2,
+	// Loyalty redemption: 10 stamps → 10% off the booking total. Shared by the
+	// admin and customer payment modals so the discount rate can't drift.
+	LOYALTY_DISCOUNT_RATE: 0.1,
+	// Gratuity suggestion presets offered by the tip surfaces (admin payment
+	// modal + customer tip page). Deliberately SEPARATE from the deposit policy
+	// constants above — a tip suggestion is gratuity, not a deposit percentage,
+	// and coupling them would silently change the tip buttons if the deposit
+	// rate ever changed.
+	TIP_PRESET_PCTS: [10, 15, 20]
 } as const;

frontend/src/routes/account/+page.svelte

@@ -283,8 +283,13 @@
 	// value instead of a hardcoded copy and survives a page reload. The local
 	// counter still only reflects confirmed purchases made in this session; any
 	// rejection the counter can't foresee surfaces through the backend's error
-	// toast.
+	// toast. The fallback below exists ONLY for old servers that don't expose
-	let dailyGiftCardBuyLimit = $state(500);
+	// daily_buy_limit yet — it is always overwritten by the server value when
+	// the balance fetch succeeds (see fetchGiftCardBalance).
+	// Cross-reference: backend/handlers/payments/giftcard_limits.go
+	// maxUserGiftCardDailyPence = 500_00 pence (£500).
+	const DAILY_GIFT_CARD_BUY_LIMIT_FALLBACK_GBP = 500;
+	let dailyGiftCardBuyLimit = $state(DAILY_GIFT_CARD_BUY_LIMIT_FALLBACK_GBP);
 	let buyDailyTotal = $state(0);
 	const buyLimitReached = $derived(buyDailyTotal >= dailyGiftCardBuyLimit);