feat(validations): merchant (bar/lavazh) ticket validations end-to-end

In-park merchants discharge customers' parking: a merchant user scans the
ticket on their device (/validate; validation:create + program↔user binding)
and applies their program — comp / first-N-minutes free / amount-off (capped,
typed at scan) / percent. All money stays at the booth: the quote folds live
validations in a canonical order (timeCredit → percent → fixed → comp, net
floors at 0, Σ lines ≡ gross − net), the payment records gross/discount and
CONSUMES the validation ids (an overstay's fresh period never re-applies
them), the receipt prints the gross → lines → net story, and the Z/X-report
carries discountTotalMinor leakage. Every apply/void is a signed, attributed
ledger event (refId = append-only void); program config is /setup/site master
data (Bar/Lavazh checkboxes + right-column panel, tabs when both) whose saves
sign config_change. Migration 0024 + reset-db drift-guard entries; 8 route
integration tests + priceSession fold suite.

See wiki/concepts/validation-discounts.md for the full design record.

Claude-Session: https://claude.ai/code/session_01YYkpEsLmoQPaize5ec3oUm

apps/server/src/booth-print.ts

@@ -80,6 +80,8 @@ function receiptFigures(
     currency?: string;
     tender?: "cash" | "card";
     graceExitMin?: number;
+    grossMinor?: number;
+    validationLines?: { label: string; discountMinor: number }[];
   };
   return {
     ticketId,
@@ -89,6 +91,9 @@ function receiptFigures(
     currency: p.currency ?? "ALL",
     tender: p.tender === "card" ? "card" : "cash",
     graceExitMin: typeof p.graceExitMin === "number" ? p.graceExitMin : null,
+    // Merchant validations, as settled on the signed payment (gross → lines → net).
+    grossMinor: typeof p.grossMinor === "number" ? p.grossMinor : null,
+    validationLines: Array.isArray(p.validationLines) ? p.validationLines : undefined,
   };
 }
 

apps/server/src/pay-station.ts

@@ -1,9 +1,10 @@
 import { desc, eq, ledgerEvents, sessions, subscriptions, tariffVersions, tariffs, type Db } from "@parking/db";
-import { priceSession, type TariffStructure, type Tender } from "@parking/shared";
+import { priceSession, type TariffStructure, type Tender, type ValidationLine } from "@parking/shared";
 import type { FastifyBaseLogger } from "fastify";
 import type { EventLog } from "./event-log.js";
 import { plateForIdentity, platesForIdentities } from "./plate-lookup.js";
 import { windowOwedBetween } from "./subscription-window.js";
+import { liveValidations } from "./validations.js";
 
 // The PAY STATION: a customer pays for an open session BEFORE walking back to the
 // car (pay-on-foot — payment is decoupled from exit). Two steps:
@@ -38,8 +39,17 @@ export interface Quote {
    *  is priced as a fresh stay from there → now, with its own daily-cap ladder, NOT
    *  "full stay minus paid" (which a daily cap collapses toward zero). */
   readonly periodStart: string;
-  /** Amount owed now: the fee for [periodStart → now]. */
+  /** Amount owed now: the fee for [periodStart → now], NET of merchant validations. */
   readonly amountMinor: number;
+  /** The pre-validation fee (= amountMinor when no validations apply). */
+  readonly grossMinor: number;
+  /** Total the merchant validations took off (gross − net). */
+  readonly discountMinor: number;
+  /** Per-validation receipt/display lines (empty when none apply). */
+  readonly validationLines: ValidationLine[];
+  /** The validation event ids this quote applied — the payment stamps them as
+   *  CONSUMED so an overstay's fresh period never re-applies them. */
+  readonly validationIds: string[];
   /** True when this quote prices an overstay period (grace lapsed), not the first stay. */
   readonly overstay: boolean;
   readonly currency: string;
@@ -117,6 +127,12 @@ export interface SessionLookup {
   /** Advisory licence plate recognized for this session (ANPR-on-snapshot). Null when
    *  none. Display/audit only — never an access decision. */
   readonly plate: string | null;
+  /** Merchant validations folded into `amountMinor` (which is NET): the pre-discount
+   *  fee, the total taken off, and the per-validation lines for the modal/receipt.
+   *  grossMinor/discountMinor are null when no quote resolved. */
+  readonly grossMinor: number | null;
+  readonly discountMinor: number | null;
+  readonly validationLines: ValidationLine[];
 }
 
 export class PayStation {
@@ -155,19 +171,28 @@ export class PayStation {
     // Pure pricing shared with the Tariff Lab (priceSession). Only the latest payment
     // matters for grace/overstay; pass it through. Overstay → fresh period from
     // grace-expiry; within-grace → settled; unpaid → entry→now running total.
+    // Merchant validations: fold the LIVE ones (applied, unvoided, not consumed by a
+    // prior payment) so the quote is NET — the payment then stamps their ids as
+    // consumed. See wiki/concepts/validation-discounts.md.
     const last = this.#lastPayment(identity);
+    const validations = liveValidations(this.#db, identity);
     const p = priceSession(
       entry.occurredAt,
       new Date().toISOString(),
       structure,
       last ? [last] : [],
       category,
+      validations,
     );
     return {
       identity,
       enteredAt: entry.occurredAt,
       periodStart: p.periodStart,
       amountMinor: p.amountMinor,
+      grossMinor: p.grossMinor,
+      discountMinor: p.discountMinor,
+      validationLines: p.validationLines,
+      validationIds: validations.map((v) => v.eventId),
       overstay: p.overstay,
       currency: tv.currency,
       tariffVersionId: tv.id,
@@ -246,6 +271,18 @@ export class PayStation {
         // The exit flow reads graceExitMin off the payment to validate the
         // walk-back window without re-resolving the tariff.
         graceExitMin: q.graceExitMin,
+        // Merchant validations: record the gross/discount split + CONSUME the applied
+        // validation ids, so reporting sees the leakage and a later overstay period
+        // never re-applies them. A zero-net settlement (full comp) is still a signed
+        // payment — grace/voucher/exit work unchanged. See validation-discounts.md.
+        ...(q.validationIds.length
+          ? {
+              grossMinor: q.grossMinor,
+              discountMinor: q.discountMinor,
+              validationIds: q.validationIds,
+              validationLines: q.validationLines.map((l) => ({ ...l })),
+            }
+          : {}),
         ...(overrideMinor != null ? { reason: "operator-set amount", quotedMinor: q.amountMinor } : {}),
       },
     });
@@ -282,6 +319,7 @@ export class PayStation {
         paidAt: null, amountMinor: null, currency: null, paidMinor: null, paidCurrency: null,
         withinGrace: false, graceExpiresAt: null,
         overstay: false, subscription: false, subscriptionId: null, subscriptionHolder: null, plate: null,
+        grossMinor: null, discountMinor: null, validationLines: [],
       };
     }
     // Subscription occurrence? The entry payload carries permit:true + permitId.
@@ -319,11 +357,17 @@ export class PayStation {
     // exit gate clears. See wiki/entities/subscription.md.
     let amountMinor: number | null = null;
     let currency: string | null = null;
+    let grossMinor: number | null = null;
+    let discountMinor: number | null = null;
+    let validationLines: ValidationLine[] = [];
     if (open && !isSubscription) {
       try {
         const q = this.quote(id);
         amountMinor = q.amountMinor;
         currency = q.currency;
+        grossMinor = q.grossMinor;
+        discountMinor = q.discountMinor;
+        validationLines = q.validationLines;
       } catch {
         /* no active tariff — leave null; modal shows session without a price */
       }
@@ -344,6 +388,7 @@ export class PayStation {
       subscription: isSubscription, subscriptionId,
       subscriptionHolder: this.#holderOf(subscriptionId),
       plate: plateForIdentity(this.#db, id)?.plate ?? null,
+      grossMinor, discountMinor, validationLines,
     };
   }
 

apps/server/src/routes/validations.test.ts

@@ -0,0 +1,272 @@
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { eq, ledgerEvents, users, type Db } from "@parking/db";
+import { createTestDb } from "@parking/db/testing";
+import type { FastifyInstance } from "fastify";
+import { buildServer } from "../server.js";
+import { login, makeLog, minutesAgo, seedTariff, seedUser } from "../test-helpers.js";
+import type { EventLog } from "../event-log.js";
+
+// Merchant validations (bar/lavazh): the merchant user scans a ticket and applies
+// their program (a SIGNED, attributed ledger event); the booth settlement quotes NET
+// and the payment CONSUMES the validation ids. These tests pin the route guards
+// (binding, caps, session state), the signed apply/void events, and the money cycle
+// through /api/pay/quote + /api/pay. See wiki/concepts/validation-discounts.md.
+
+let db: Db;
+let close: () => void;
+let app: FastifyInstance;
+
+beforeEach(async () => {
+  const t = createTestDb();
+  db = t.db;
+  close = t.close;
+  app = await buildServer({ db });
+  await app.ready();
+});
+afterEach(async () => {
+  await app.close();
+  close();
+});
+
+type Auth = { cookie: string; csrf: string };
+const hdrs = (a: Auth) => ({ cookie: a.cookie, "x-csrf-token": a.csrf });
+
+async function seedMerchant(username = "bari"): Promise<{ auth: Auth; userId: string }> {
+  await seedUser(db, { username, password: "pw123456", roleId: "validues", permissions: ["validation:create"] });
+  const auth = await login(app, username, "pw123456");
+  const row = db.select().from(users).where(eq(users.username, username)).get()!;
+  return { auth, userId: row.id };
+}
+
+async function seedAdmin(): Promise<Auth> {
+  await seedUser(db, { username: "admin", password: "pw123456" });
+  return login(app, "admin", "pw123456");
+}
+
+/** Admin-upserts the "bar" program bound to the given user. */
+async function putProgram(auth: Auth, body: Record<string, unknown>, id = "bar") {
+  return app.inject({ method: "PUT", url: `/api/validation/programs/${id}`, headers: hdrs(auth), payload: body });
+}
+
+const fixedProgram = (userId: string, over: Record<string, unknown> = {}) => ({
+  name: "Bar",
+  mode: "fixed",
+  maxAmountMinor: 100000,
+  active: true,
+  userIds: [userId],
+  ...over,
+});
+
+describe("merchant validations", () => {
+  let log: EventLog;
+  beforeEach(() => {
+    log = makeLog(db);
+  });
+
+  const mint = (identity: string, minAgo: number, payload: Record<string, unknown> | null = null) =>
+    log.append({ type: "vehicle_entry", direction: "entry", identity, occurredAt: minutesAgo(minAgo), payload });
+
+  it("program upsert is admin-gated and signs a config_change; a no-op save signs nothing", async () => {
+    const admin = await seedAdmin();
+    const { auth: merchant, userId } = await seedMerchant();
+
+    expect((await putProgram(merchant, fixedProgram(userId))).statusCode).toBe(403);
+
+    const res = await putProgram(admin, fixedProgram(userId));
+    expect(res.statusCode).toBe(200);
+    expect(res.json()).toMatchObject({ id: "bar", mode: "fixed", active: true, userIds: [userId] });
+
+    const changes = () => db.select().from(ledgerEvents).all().filter((r) => r.type === "config_change");
+    expect(changes()).toHaveLength(1);
+    expect(changes()[0].payload).toMatchObject({ setting: "validationProgram.bar", operator: "admin" });
+
+    // Identical second save → no second config_change.
+    await putProgram(admin, fixedProgram(userId));
+    expect(changes()).toHaveLength(1);
+  });
+
+  it("per-mode validation: timeCredit needs minutes, percent needs percent, fixed needs a cap", async () => {
+    const admin = await seedAdmin();
+    expect((await putProgram(admin, { name: "X", mode: "timeCredit", active: true })).statusCode).toBe(400);
+    expect((await putProgram(admin, { name: "X", mode: "percent", active: true })).statusCode).toBe(400);
+    expect((await putProgram(admin, { name: "X", mode: "fixed", active: true })).statusCode).toBe(400);
+    expect((await putProgram(admin, { name: "X", mode: "timeCredit", minutes: 60, active: true })).statusCode).toBe(200);
+  });
+
+  it("GET /mine returns only MY bound, active programs", async () => {
+    const admin = await seedAdmin();
+    const { auth: merchant, userId } = await seedMerchant();
+    await putProgram(admin, fixedProgram(userId));
+    await putProgram(admin, { name: "Lavazh", mode: "comp", active: true, userIds: [] }, "lavazh");
+
+    const res = await app.inject({ method: "GET", url: "/api/validation/mine", headers: hdrs(merchant) });
+    expect(res.statusCode).toBe(200);
+    const programs = res.json().programs as { id: string }[];
+    expect(programs.map((p) => p.id)).toEqual(["bar"]);
+  });
+
+  it("apply: binding, session-state, duplicate and amount guards", async () => {
+    const admin = await seedAdmin();
+    const { auth: merchant, userId } = await seedMerchant();
+    const { auth: other } = await seedMerchant("tjetri");
+    await putProgram(admin, fixedProgram(userId));
+    seedTariff(db);
+    await mint("T1", 120);
+
+    const apply = (auth: Auth, payload: Record<string, unknown>) =>
+      app.inject({ method: "POST", url: "/api/validation/apply", headers: hdrs(auth), payload });
+
+    // Unbound merchant → 403; unknown ticket → 404; missing amount (fixed) → 400;
+    // amount above the cap → 400.
+    expect((await apply(other, { identity: "T1", programId: "bar", amountMinor: 5000 })).statusCode).toBe(403);
+    expect((await apply(merchant, { identity: "NOPE", programId: "bar", amountMinor: 5000 })).statusCode).toBe(404);
+    expect((await apply(merchant, { identity: "T1", programId: "bar" })).statusCode).toBe(400);
+    expect((await apply(merchant, { identity: "T1", programId: "bar", amountMinor: 999999 })).statusCode).toBe(400);
+
+    // Subscriber sessions are never validated (prepaid).
+    await mint("SUB1", 60, { permit: true, permitId: "s-1" });
+    expect((await apply(merchant, { identity: "SUB1", programId: "bar", amountMinor: 5000 })).statusCode).toBe(409);
+
+    // Success → a SIGNED validation event with resolved values + the merchant username.
+    const ok = await apply(merchant, { identity: "T1", programId: "bar", amountMinor: 5000 });
+    expect(ok.statusCode).toBe(201);
+    const ev = db.select().from(ledgerEvents).all().find((r) => r.type === "validation")!;
+    expect(ev.payload).toMatchObject({
+      programId: "bar",
+      programLabel: "Bar",
+      mode: "fixed",
+      amountMinor: 5000,
+      operator: "bari",
+    });
+
+    // Same program twice on one ticket → 409.
+    expect((await apply(merchant, { identity: "T1", programId: "bar", amountMinor: 1000 })).statusCode).toBe(409);
+  });
+
+  it("the money cycle: quote nets the validation, pay records gross/discount and CONSUMES it", async () => {
+    const admin = await seedAdmin();
+    const { auth: merchant, userId } = await seedMerchant();
+    await putProgram(admin, fixedProgram(userId));
+    // 100/h flat; 2h → gross 20000.
+    seedTariff(db, { pricePerIncrementMinor: 10000, incrementMin: 60 });
+    await mint("T1", 119);
+
+    await app.inject({
+      method: "POST",
+      url: "/api/validation/apply",
+      headers: hdrs(merchant),
+      payload: { identity: "T1", programId: "bar", amountMinor: 5000 },
+    });
+
+    const q1 = await app.inject({ method: "GET", url: "/api/pay/quote?identity=T1", headers: hdrs(admin) });
+    expect(q1.json()).toMatchObject({
+      grossMinor: 20000,
+      discountMinor: 5000,
+      amountMinor: 15000,
+    });
+    expect(q1.json().validationLines).toEqual([
+      { programId: "bar", label: "Bar", mode: "fixed", discountMinor: 5000 },
+    ]);
+
+    // Pay (needs an open shift) → the payment carries the split + consumed ids.
+    await app.inject({ method: "POST", url: "/api/shift/open", headers: hdrs(admin) });
+    const pay = await app.inject({ method: "POST", url: "/api/pay", headers: hdrs(admin), payload: { identity: "T1", tender: "cash" } });
+    expect(pay.statusCode).toBe(201);
+    expect(pay.json().amountMinor).toBe(15000);
+
+    const payment = db.select().from(ledgerEvents).all().find((r) => r.type === "payment")!;
+    expect(payment.payload).toMatchObject({ amountMinor: 15000, grossMinor: 20000, discountMinor: 5000 });
+    expect((payment.payload as { validationIds?: string[] }).validationIds).toHaveLength(1);
+
+    // Settled: the follow-up quote owes 0 and applies nothing further.
+    const q2 = await app.inject({ method: "GET", url: "/api/pay/quote?identity=T1", headers: hdrs(admin) });
+    expect(q2.json().amountMinor).toBe(0);
+    expect(q2.json().validationLines).toEqual([]);
+  });
+
+  it("a full comp settles at 0 through the normal pay path (grace starts, chain verifies)", async () => {
+    const admin = await seedAdmin();
+    const { auth: merchant, userId } = await seedMerchant();
+    await putProgram(admin, { name: "Lavazh falas", mode: "comp", active: true, userIds: [userId] }, "lavazh");
+    seedTariff(db, { pricePerIncrementMinor: 10000 });
+    await mint("T1", 90);
+
+    await app.inject({
+      method: "POST",
+      url: "/api/validation/apply",
+      headers: hdrs(merchant),
+      payload: { identity: "T1", programId: "lavazh" },
+    });
+
+    const q = await app.inject({ method: "GET", url: "/api/pay/quote?identity=T1", headers: hdrs(admin) });
+    expect(q.json().amountMinor).toBe(0);
+    expect(q.json().grossMinor).toBeGreaterThan(0);
+
+    await app.inject({ method: "POST", url: "/api/shift/open", headers: hdrs(admin) });
+    const pay = await app.inject({ method: "POST", url: "/api/pay", headers: hdrs(admin), payload: { identity: "T1", tender: "cash" } });
+    expect(pay.statusCode).toBe(201);
+    expect(pay.json().amountMinor).toBe(0);
+
+    // The 0-net settlement still grants walk-back grace (the session reads settled).
+    const view = await app.inject({ method: "GET", url: "/api/session/T1", headers: hdrs(admin) });
+    expect(view.json()).toMatchObject({ withinGrace: true, amountMinor: 0 });
+  });
+
+  it("void: own unused only; a consumed validation is locked", async () => {
+    const admin = await seedAdmin();
+    const { auth: merchant, userId } = await seedMerchant();
+    const { auth: other, userId: otherId } = await seedMerchant("tjetri");
+    await putProgram(admin, fixedProgram(userId, { userIds: [userId, otherId] }));
+    seedTariff(db, { pricePerIncrementMinor: 10000 });
+    await mint("T1", 90);
+
+    const applied = await app.inject({
+      method: "POST",
+      url: "/api/validation/apply",
+      headers: hdrs(merchant),
+      payload: { identity: "T1", programId: "bar", amountMinor: 5000 },
+    });
+    const eventId = applied.json().eventId as string;
+
+    const voidReq = (auth: Auth) =>
+      app.inject({ method: "POST", url: "/api/validation/void", headers: hdrs(auth), payload: { eventId, identity: "T1" } });
+
+    // Someone else's validation → 403. Own → ok, and the quote returns to gross.
+    expect((await voidReq(other)).statusCode).toBe(403);
+    expect((await voidReq(merchant)).statusCode).toBe(200);
+    const q = await app.inject({ method: "GET", url: "/api/pay/quote?identity=T1", headers: hdrs(admin) });
+    expect(q.json().discountMinor).toBe(0);
+
+    // Re-apply (the void freed the per-session slot), consume it with a payment, then
+    // a void must refuse — the settlement already happened.
+    const re = await app.inject({
+      method: "POST",
+      url: "/api/validation/apply",
+      headers: hdrs(merchant),
+      payload: { identity: "T1", programId: "bar", amountMinor: 5000 },
+    });
+    await app.inject({ method: "POST", url: "/api/shift/open", headers: hdrs(admin) });
+    await app.inject({ method: "POST", url: "/api/pay", headers: hdrs(admin), payload: { identity: "T1", tender: "cash" } });
+    const locked = await app.inject({
+      method: "POST",
+      url: "/api/validation/void",
+      headers: hdrs(merchant),
+      payload: { eventId: re.json().eventId, identity: "T1" },
+    });
+    expect(locked.statusCode).toBe(409);
+  });
+
+  it("maxPerDay caps applications across tickets", async () => {
+    const admin = await seedAdmin();
+    const { auth: merchant, userId } = await seedMerchant();
+    await putProgram(admin, { name: "Lavazh", mode: "comp", maxPerDay: 1, active: true, userIds: [userId] }, "lavazh");
+    seedTariff(db);
+    await mint("T1", 60);
+    await mint("T2", 30);
+
+    const apply = (identity: string) =>
+      app.inject({ method: "POST", url: "/api/validation/apply", headers: hdrs(merchant), payload: { identity, programId: "lavazh" } });
+    expect((await apply("T1")).statusCode).toBe(201);
+    expect((await apply("T2")).statusCode).toBe(409);
+  });
+});

apps/server/src/routes/validations.ts

@@ -0,0 +1,360 @@
+import type { FastifyInstance } from "fastify";
+import {
+  and,
+  eq,
+  isNull,
+  inArray,
+  ledgerEvents,
+  users,
+  validationProgramUsers,
+  validationPrograms,
+  type Db,
+} from "@parking/db";
+import { VALIDATION_MODES, type ValidationMode } from "@parking/shared";
+import { requirePermission } from "../auth.js";
+import type { EventLog } from "../event-log.js";
+import { liveValidations, sessionValidations } from "../validations.js";
+
+// Merchant validations (bar / lavazh). The merchant is VALIDATION-ONLY: they scan the
+// customer's ticket on their own device and apply their program — all money and paper
+// stay at the booth, which settles net of these events. Program config is admin-composed
+// on /setup/site (site:read/update — no dedicated permission); applying is the merchant
+// user's `validation:create`, guarded FURTHER by the program↔user binding so a bar user
+// can never apply the lavazh program. Every apply/void is a signed, attributed ledger
+// event. See wiki/concepts/validation-discounts.md.
+//   - GET  /api/validation/programs           : all programs + bound users. (site:read)
+//   - PUT  /api/validation/programs/:id       : upsert config + bindings;   (site:update)
+//                                               signs a config_change.
+//   - GET  /api/validation/mine               : my bound ACTIVE programs.   (validation:create)
+//   - GET  /api/validation/session/:identity  : minimal session view for    (validation:create)
+//                                               the merchant screen (no money data).
+//   - POST /api/validation/apply              : apply my program (signed).  (validation:create)
+//   - POST /api/validation/void               : void my OWN unused apply.   (validation:create)
+
+/** Well-formed program ids: kebab slugs ("bar", "lavazh", a future "hotel-2"). */
+const ID_RE = /^[a-z][a-z0-9-]{1,31}$/;
+
+interface ProgramBody {
+  name?: string;
+  mode?: ValidationMode;
+  minutes?: number | null;
+  percent?: number | null;
+  maxAmountMinor?: number | null;
+  maxPerDay?: number | null;
+  active?: boolean;
+  /** Full replacement set of bound user ids. */
+  userIds?: string[];
+}
+
+interface ApplyBody {
+  identity: string;
+  programId: string;
+  /** fixed mode only: the discount the merchant grants (minor units, ≤ maxAmountMinor). */
+  amountMinor?: number;
+}
+
+interface VoidBody {
+  eventId: string;
+  identity: string;
+}
+
+/** null when valid, else the 400 message. Checks the per-mode parameter. */
+function validateProgram(b: ProgramBody): string | null {
+  if (!b.name || !String(b.name).trim()) return "name is required";
+  if (!VALIDATION_MODES.includes(b.mode as ValidationMode)) return "mode must be comp|timeCredit|fixed|percent";
+  const intOrNull = (v: unknown) => v == null || (Number.isInteger(v) && (v as number) > 0);
+  if (!intOrNull(b.minutes)) return "minutes must be a positive integer";
+  if (!intOrNull(b.maxAmountMinor)) return "maxAmountMinor must be a positive integer";
+  if (!intOrNull(b.maxPerDay)) return "maxPerDay must be a positive integer";
+  if (b.percent != null && (!Number.isInteger(b.percent) || b.percent < 1 || b.percent > 100))
+    return "percent must be 1..100";
+  if (b.mode === "timeCredit" && b.minutes == null) return "timeCredit needs minutes";
+  if (b.mode === "percent" && b.percent == null) return "percent mode needs percent";
+  if (b.mode === "fixed" && b.maxAmountMinor == null) return "fixed mode needs maxAmountMinor";
+  return null;
+}
+
+export async function validationRoutes(app: FastifyInstance, db: Db, eventLog: EventLog): Promise<void> {
+  const siteRead = requirePermission("site:read");
+  const siteWrite = requirePermission("site:update");
+  const applyGuard = requirePermission("validation:create");
+
+  const liveProgram = (id: string) =>
+    db
+      .select()
+      .from(validationPrograms)
+      .where(and(eq(validationPrograms.id, id), isNull(validationPrograms.deletedAt)))
+      .get();
+
+  const boundUserIds = (programId: string): string[] =>
+    db
+      .select({ userId: validationProgramUsers.userId })
+      .from(validationProgramUsers)
+      .where(eq(validationProgramUsers.programId, programId))
+      .all()
+      .map((r) => r.userId);
+
+  // The setup panel's read: every live program with its bound users.
+  app.get("/api/validation/programs", { preHandler: siteRead }, async () => {
+    const programs = db.select().from(validationPrograms).where(isNull(validationPrograms.deletedAt)).all();
+    return {
+      programs: programs.map((p) => ({ ...p, userIds: boundUserIds(p.id) })),
+    };
+  });
+
+  // Upsert a program (the /setup/site checkbox + panel). Creates the well-known row on
+  // first enable; replaces the binding set; signs an attributed config_change when
+  // anything actually changed (the entry-presence-bypass precedent — enabling a discount
+  // program is fraud-relevant config).
+  app.put<{ Params: { id: string }; Body: ProgramBody }>(
+    "/api/validation/programs/:id",
+    { preHandler: siteWrite },
+    async (req, reply) => {
+      const id = (req.params.id ?? "").trim();
+      if (!ID_RE.test(id)) return reply.code(400).send({ error: "invalid program id" });
+      const b = req.body ?? ({} as ProgramBody);
+      const bad = validateProgram(b);
+      if (bad) return reply.code(400).send({ error: bad });
+
+      const userIds = Array.isArray(b.userIds) ? [...new Set(b.userIds)] : [];
+      if (userIds.length) {
+        const found = db
+          .select({ id: users.id })
+          .from(users)
+          .where(and(inArray(users.id, userIds), isNull(users.deletedAt)))
+          .all();
+        if (found.length !== userIds.length) return reply.code(400).send({ error: "unknown user in userIds" });
+      }
+
+      const prev = liveProgram(id);
+      const prevUserIds = prev ? boundUserIds(id).sort() : [];
+      const next = {
+        name: String(b.name).trim(),
+        mode: b.mode as ValidationMode,
+        minutes: b.minutes ?? null,
+        percent: b.percent ?? null,
+        maxAmountMinor: b.maxAmountMinor ?? null,
+        maxPerDay: b.maxPerDay ?? null,
+        active: b.active === true,
+      };
+
+      if (prev) {
+        db.update(validationPrograms).set(next).where(eq(validationPrograms.id, id)).run();
+      } else {
+        db.insert(validationPrograms).values({ id, ...next }).run();
+      }
+      db.delete(validationProgramUsers).where(eq(validationProgramUsers.programId, id)).run();
+      for (const userId of userIds) {
+        db.insert(validationProgramUsers).values({ programId: id, userId }).run();
+      }
+
+      // Sign the change (attributed) — enabling/reshaping a discount program is
+      // fraud-relevant config. Compare against the previous row + binding set so a
+      // no-op save signs nothing.
+      const summary = (row: typeof next, ids: string[]) => JSON.stringify({ ...row, userIds: [...ids].sort() });
+      const prevSummary = prev
+        ? summary(
+            { name: prev.name, mode: prev.mode, minutes: prev.minutes, percent: prev.percent,
+              maxAmountMinor: prev.maxAmountMinor, maxPerDay: prev.maxPerDay, active: prev.active },
+            prevUserIds,
+          )
+        : null;
+      if (prevSummary !== summary(next, userIds)) {
+        await eventLog.append({
+          type: "config_change",
+          source: "manual",
+          identity: `validation-program:${id}`,
+          payload: {
+            setting: `validationProgram.${id}`,
+            value: { ...next, userCount: userIds.length },
+            prev: prev
+              ? { name: prev.name, mode: prev.mode, minutes: prev.minutes, percent: prev.percent,
+                  maxAmountMinor: prev.maxAmountMinor, maxPerDay: prev.maxPerDay, active: prev.active }
+              : null,
+            operator: req.user?.username ?? "unknown",
+          },
+        });
+      }
+
+      const row = liveProgram(id);
+      return { ...row, userIds: boundUserIds(id) };
+    },
+  );
+
+  // The merchant screen's program list: MY bound, active programs.
+  app.get("/api/validation/mine", { preHandler: applyGuard }, async (req) => {
+    const rows = db
+      .select()
+      .from(validationPrograms)
+      .innerJoin(validationProgramUsers, eq(validationProgramUsers.programId, validationPrograms.id))
+      .where(
+        and(
+          eq(validationProgramUsers.userId, req.user.sub),
+          eq(validationPrograms.active, true),
+          isNull(validationPrograms.deletedAt),
+        ),
+      )
+      .all();
+    return { programs: rows.map((r) => r.validation_programs) };
+  });
+
+  // Minimal session view for the merchant screen — deliberately NO money data (the
+  // merchant validates; the booth settles): found/open/entry time + the validations
+  // already on the session (so the UI can show "already validated" and offer void).
+  app.get<{ Params: { identity: string } }>(
+    "/api/validation/session/:identity",
+    { preHandler: applyGuard },
+    async (req, reply) => {
+      const identity = (req.params.identity ?? "").trim();
+      if (!identity) return reply.code(400).send({ error: "identity required" });
+      const rows = db
+        .select({ type: ledgerEvents.type, occurredAt: ledgerEvents.occurredAt, payload: ledgerEvents.payload })
+        .from(ledgerEvents)
+        .where(eq(ledgerEvents.identity, identity))
+        .orderBy(ledgerEvents.index)
+        .all();
+      const entry = rows.find((r) => r.type === "vehicle_entry");
+      if (!entry) return { identity, found: false, open: false, enteredAt: null, subscription: false, validations: [] };
+      const entryPl = (entry.payload ?? {}) as { permit?: boolean; permitId?: string };
+      const subscription = entryPl.permit === true || entryPl.permitId != null;
+      const open = !rows.some((r) => r.type === "vehicle_exit" || r.type === "void");
+      return {
+        identity,
+        found: true,
+        open,
+        enteredAt: entry.occurredAt,
+        subscription,
+        validations: sessionValidations(db, identity),
+      };
+    },
+  );
+
+  // APPLY: the merchant's one action. Guards, in order: program live+active → the
+  // user is BOUND to it → the session is an OPEN TRANSIENT → not already carrying a
+  // live application of this program → per-day cap → fixed-amount bounds. Appends the
+  // signed validation event with the RESOLVED values.
+  app.post<{ Body: ApplyBody }>("/api/validation/apply", { preHandler: applyGuard }, async (req, reply) => {
+    const identity = (req.body?.identity ?? "").trim();
+    const programId = (req.body?.programId ?? "").trim();
+    if (!identity || !programId) return reply.code(400).send({ error: "identity and programId required" });
+
+    const program = liveProgram(programId);
+    if (!program || !program.active) return reply.code(404).send({ error: "program not found or inactive" });
+    if (!boundUserIds(programId).includes(req.user.sub)) {
+      return reply.code(403).send({ error: "you are not bound to this program" });
+    }
+
+    // Session state — an open transient (subscriptions are prepaid; nothing to discount).
+    const rows = db
+      .select({ type: ledgerEvents.type, payload: ledgerEvents.payload })
+      .from(ledgerEvents)
+      .where(eq(ledgerEvents.identity, identity))
+      .orderBy(ledgerEvents.index)
+      .all();
+    const entry = rows.find((r) => r.type === "vehicle_entry");
+    if (!entry) return reply.code(404).send({ error: "no session for ticket" });
+    const entryPl = (entry.payload ?? {}) as { permit?: boolean; permitId?: string };
+    if (entryPl.permit === true || entryPl.permitId != null) {
+      return reply.code(409).send({ error: "subscription sessions cannot be validated" });
+    }
+    if (rows.some((r) => r.type === "vehicle_exit" || r.type === "void")) {
+      return reply.code(409).send({ error: "session is closed" });
+    }
+    if (liveValidations(db, identity).some((v) => v.programId === programId)) {
+      return reply.code(409).send({ error: "this program is already applied to the ticket" });
+    }
+
+    // Per-day cap: unvoided applications of this program since LOCAL midnight (the
+    // appliance runs in site time).
+    if (program.maxPerDay != null) {
+      const midnight = new Date();
+      midnight.setHours(0, 0, 0, 0);
+      const todays = db
+        .select({ id: ledgerEvents.id, occurredAt: ledgerEvents.occurredAt, payload: ledgerEvents.payload, type: ledgerEvents.type })
+        .from(ledgerEvents)
+        .where(eq(ledgerEvents.type, "validation"))
+        .all()
+        .filter((r) => Date.parse(r.occurredAt) >= midnight.getTime());
+      const voidedIds = new Set(
+        todays.map((r) => (r.payload as { refId?: string } | null)?.refId).filter(Boolean) as string[],
+      );
+      const count = todays.filter((r) => {
+        const p = (r.payload ?? {}) as { programId?: string; refId?: string };
+        return p.programId === programId && !p.refId && !voidedIds.has(r.id);
+      }).length;
+      if (count >= program.maxPerDay) {
+        return reply.code(409).send({ error: "daily cap reached for this program" });
+      }
+    }
+
+    // Resolve the values off the program row (frozen into the signed event).
+    let amountMinor: number | undefined;
+    if (program.mode === "fixed") {
+      const a = req.body?.amountMinor;
+      if (a == null || !Number.isInteger(a) || a <= 0) {
+        return reply.code(400).send({ error: "amountMinor (positive integer) required for this program" });
+      }
+      if (program.maxAmountMinor != null && a > program.maxAmountMinor) {
+        return reply.code(400).send({ error: `amount exceeds the program cap (${program.maxAmountMinor})` });
+      }
+      amountMinor = a;
+    }
+
+    const ev = await eventLog.append({
+      type: "validation",
+      source: "manual",
+      identity,
+      payload: {
+        sessionRef: identity,
+        programId,
+        programLabel: program.name,
+        mode: program.mode,
+        ...(program.mode === "timeCredit" && program.minutes != null ? { minutes: program.minutes } : {}),
+        ...(program.mode === "percent" && program.percent != null ? { percent: program.percent } : {}),
+        ...(amountMinor != null ? { amountMinor } : {}),
+        operator: req.user.username,
+      },
+    });
+    return reply.code(201).send({
+      ok: true,
+      eventId: ev.id,
+      programId,
+      label: program.name,
+      mode: program.mode,
+      minutes: program.mode === "timeCredit" ? program.minutes : undefined,
+      percent: program.mode === "percent" ? program.percent : undefined,
+      amountMinor,
+    });
+  });
+
+  // VOID my own UNUSED validation (fat-fingered amount / wrong ticket). Append-only:
+  // a validation event with refId, never a delete. Refused once a payment consumed it
+  // (the settlement already happened — that dispute goes to the booth/admin).
+  app.post<{ Body: VoidBody }>("/api/validation/void", { preHandler: applyGuard }, async (req, reply) => {
+    const eventId = (req.body?.eventId ?? "").trim();
+    const identity = (req.body?.identity ?? "").trim();
+    if (!eventId || !identity) return reply.code(400).send({ error: "eventId and identity required" });
+    const target = sessionValidations(db, identity).find((v) => v.eventId === eventId);
+    if (!target) return reply.code(404).send({ error: "validation not found" });
+    if (target.operator !== req.user.username) {
+      return reply.code(403).send({ error: "you may only void your own validation" });
+    }
+    if (target.voided) return reply.code(409).send({ error: "already voided" });
+    if (target.consumedBy != null) {
+      return reply.code(409).send({ error: "already used in a payment — ask the booth/admin" });
+    }
+    await eventLog.append({
+      type: "validation",
+      source: "manual",
+      identity,
+      payload: {
+        sessionRef: identity,
+        refId: eventId,
+        programId: target.programId,
+        programLabel: target.label,
+        operator: req.user.username,
+      },
+    });
+    return { ok: true };
+  });
+}

apps/server/src/server.ts

@@ -45,6 +45,7 @@ import { shiftRoutes } from "./routes/shift.js";
 import { drawerRoutes } from "./routes/drawer.js";
 import { entryRoutes } from "./routes/entry.js";
 import { siteRoutes } from "./routes/site.js";
+import { validationRoutes } from "./routes/validations.js";
 import { snapshotRoutes } from "./routes/snapshots.js";
 import { tariffRoutes } from "./routes/tariffs.js";
 import { printerRoutes } from "./routes/printers.js";
@@ -292,6 +293,11 @@ export async function buildServer(opts: BuildOptions = {}): Promise<FastifyInsta
   // at capacity) is in the entry flow. See wiki/concepts/capacity-occupancy.md.
   await siteRoutes(app, db, eventLog);
 
+  // Merchant validations (bar / lavazh): setup panel config + the merchant user's
+  // scan-and-apply. The booth settlement folds the applied validations into its
+  // quote (pay-station.ts). See wiki/concepts/validation-discounts.md.
+  await validationRoutes(app, db, eventLog);
+
   // Application logs: ingest frontend errors (POST /api/logs, any signed-in user) +
   // read the store (GET /api/logs, log:read). See wiki/concepts/app-logs.md.
   await logRoutes(app, logService);

apps/server/src/shift-service.ts

@@ -55,6 +55,7 @@ export interface ShiftSummary {
   readonly subscriptionTotalMinor: number;
   readonly subscriptionSalesMinor: number;
   readonly subscriptionWindowMinor: number;
+  readonly discountTotalMinor: number;
   readonly openingFloatMinor: number;
   readonly cashAddedMinor: number;
   readonly cashRemovedMinor: number;
@@ -78,6 +79,9 @@ export interface ShiftReport {
   readonly subscriptionSalesMinor: number;
   /** Subscriber OUT-OF-WINDOW transient-tariff charges only. */
   readonly subscriptionWindowMinor: number;
+  /** Merchant-validation DISCOUNT total given away in the window (leakage — the
+   *  cash/card figures above are already NET of it). See validation-discounts.md. */
+  readonly discountTotalMinor: number;
   // --- Drawer (physical cash till; carries across shifts) ---
   /** Cash in the drawer at shift start = prior shift's expected closing drawer. */
   readonly openingFloatMinor: number;
@@ -220,6 +224,7 @@ export class ShiftService {
         subscriptionTotalMinor?: number;
         subscriptionSalesMinor?: number;
         subscriptionWindowMinor?: number;
+        discountTotalMinor?: number;
         openingFloatMinor?: number;
         cashAddedMinor?: number;
         cashRemovedMinor?: number;
@@ -250,6 +255,8 @@ export class ShiftService {
         ticketTotalMinor:
           pl.ticketTotalMinor ??
           (pl.cashTotalMinor ?? 0) + (pl.cardTotalMinor ?? 0) - (pl.subscriptionTotalMinor ?? 0),
+        // Merchant-validation leakage (added 2026-07-13). Old reports lack it → 0.
+        discountTotalMinor: pl.discountTotalMinor ?? 0,
         openingFloatMinor: pl.openingFloatMinor ?? 0,
         cashAddedMinor: pl.cashAddedMinor ?? 0,
         cashRemovedMinor: pl.cashRemovedMinor ?? 0,
@@ -522,6 +529,9 @@ export class ShiftService {
     // the subscription sale path).
     let subscriptionSalesMinor = 0;
     let subscriptionWindowMinor = 0;
+    // Merchant-validation leakage: Σ discountMinor across the window's payments. The
+    // tender totals are already NET; this is the "given away" figure beside them.
+    let discountTotalMinor = 0;
     let currency: string | null = null;
     for (const p of payments) {
       const pl = (p.payload ?? {}) as LedgerPayload & {
@@ -534,6 +544,7 @@ export class ShiftService {
       if (pl.subscriptionSale === true) subscriptionSalesMinor += amt;
       else if (pl.subscriptionWindowCharge === true) subscriptionWindowMinor += amt;
       // (else → transient ticket; derived below as total − subscription)
+      if (typeof pl.discountMinor === "number") discountTotalMinor += pl.discountMinor;
       if (pl.currency) currency = pl.currency;
     }
     const subscriptionTotalMinor = subscriptionSalesMinor + subscriptionWindowMinor;
@@ -589,6 +600,7 @@ export class ShiftService {
       subscriptionTotalMinor,
       subscriptionSalesMinor,
       subscriptionWindowMinor,
+      discountTotalMinor,
       openingFloatMinor,
       cashAddedMinor,
       cashRemovedMinor,
@@ -627,6 +639,7 @@ export class ShiftService {
       subscriptionTotalMinor,
       subscriptionSalesMinor,
       subscriptionWindowMinor,
+      discountTotalMinor,
       openingFloatMinor,
       cashAddedMinor,
       cashRemovedMinor,
@@ -649,6 +662,7 @@ export class ShiftService {
         subscriptionTotalMinor,
         subscriptionSalesMinor,
         subscriptionWindowMinor,
+        discountTotalMinor,
         openingFloatMinor,
         cashAddedMinor,
         cashRemovedMinor,
@@ -692,6 +706,9 @@ export class ShiftService {
       // (subscriptionSalesMinor stays in the signed payload — it's just not printed.)
       `Abonime:       ${money(r.subscriptionTotalMinor)} ${cur}`,
       `Jashtë orarit: ${money(r.subscriptionWindowMinor)} ${cur}`,
+      // Merchant-validation leakage — printed only when the shift actually gave any
+      // (older slips stay byte-identical). The takings above are already NET of it.
+      ...(r.discountTotalMinor > 0 ? [`Zbritje (validime): ${money(r.discountTotalMinor)} ${cur}`] : []),
       "",
       "-- Arka --",
       `Gjëndje fillestare:    ${money(r.openingFloatMinor)} ${cur}`,

apps/server/src/validations.ts

@@ -0,0 +1,88 @@
+import { eq, ledgerEvents, type Db } from "@parking/db";
+import type { SessionValidation, ValidationMode } from "@parking/shared";
+
+// Merchant-validation ledger folds. A validation is a SIGNED, appended event on the
+// session (never a mutable flag): payload carries the RESOLVED values (programId,
+// label, mode, minutes/amountMinor/percent) + the merchant username. A validation
+// event with `refId` set VOIDS the referenced one; a payment's `validationIds` marks
+// which validations it CONSUMED (so an overstay's fresh period never re-applies
+// them). See wiki/concepts/validation-discounts.md.
+
+/** A validation event folded with its lifecycle state. */
+export interface AppliedValidation extends SessionValidation {
+  readonly eventId: string;
+  readonly occurredAt: string;
+  /** The merchant username who applied it. */
+  readonly operator: string | null;
+  /** Voided by a later validation event referencing it. */
+  readonly voided: boolean;
+  /** The payment event id that consumed it, if settled. */
+  readonly consumedBy: string | null;
+}
+
+/** All validations ever applied to a session (newest last), with voided/consumed
+ *  state folded from the chain. One identity-scoped ledger scan. */
+export function sessionValidations(db: Db, identity: string): AppliedValidation[] {
+  const rows = db
+    .select({
+      id: ledgerEvents.id,
+      type: ledgerEvents.type,
+      occurredAt: ledgerEvents.occurredAt,
+      payload: ledgerEvents.payload,
+    })
+    .from(ledgerEvents)
+    .where(eq(ledgerEvents.identity, identity))
+    .orderBy(ledgerEvents.index)
+    .all();
+
+  const voided = new Set<string>();
+  const consumedBy = new Map<string, string>();
+  const applies: AppliedValidation[] = [];
+
+  for (const r of rows) {
+    const p = (r.payload ?? {}) as {
+      refId?: string;
+      programId?: string;
+      programLabel?: string;
+      mode?: ValidationMode;
+      minutes?: number;
+      amountMinor?: number;
+      percent?: number;
+      operator?: string;
+      validationIds?: string[];
+    };
+    if (r.type === "validation") {
+      if (p.refId) {
+        voided.add(p.refId);
+      } else if (p.programId && p.mode) {
+        applies.push({
+          eventId: r.id,
+          occurredAt: r.occurredAt,
+          programId: p.programId,
+          label: p.programLabel ?? p.programId,
+          mode: p.mode,
+          ...(typeof p.minutes === "number" ? { minutes: p.minutes } : {}),
+          ...(typeof p.amountMinor === "number" ? { amountMinor: p.amountMinor } : {}),
+          ...(typeof p.percent === "number" ? { percent: p.percent } : {}),
+          operator: p.operator ?? null,
+          voided: false,
+          consumedBy: null,
+        });
+      }
+    } else if (r.type === "payment" && Array.isArray(p.validationIds)) {
+      for (const vid of p.validationIds) consumedBy.set(vid, r.id);
+    }
+  }
+
+  return applies.map((a) => ({
+    ...a,
+    voided: voided.has(a.eventId),
+    consumedBy: consumedBy.get(a.eventId) ?? null,
+  }));
+}
+
+/** The LIVE validations for pricing: applied, not voided, not consumed by a prior
+ *  payment. This is exactly what `priceSession(..., validations)` expects. */
+export function liveValidations(db: Db, identity: string): AppliedValidation[] {
+  return sessionValidations(db, identity).filter((v) => !v.voided && v.consumedBy == null);
+}

apps/web/src/BoothPayModal.tsx

@@ -383,6 +383,30 @@ export function BoothPayModal({ identity, onClose }: { identity: string; onClose
                   />
                 </div>
 
+                {/* Merchant validations (bar/lavazh): the gross fee + one line per
+                    discount — the Total below is the NET the customer pays. The lines
+                    ride the quote (SessionLookup.validationLines) and reprint on the
+                    receipt. See wiki/concepts/validation-discounts.md. */}
+                {!isSubscription &&
+                  (s.validationLines ?? []).length > 0 &&
+                  s.currency != null &&
+                  s.amountMinor != null && (
+                    <div className="rounded-term bg-term-panel-2 px-3 py-2 text-[0.75rem]">
+                      <div className="flex justify-between text-term-text">
+                        <span>{t("val.gross")}</span>
+                        <span className="tabular-nums">
+                          {formatMoney(s.grossMinor ?? s.amountMinor, s.currency)}
+                        </span>
+                      </div>
+                      {(s.validationLines ?? []).map((v, i) => (
+                        <div key={i} className="flex justify-between text-term-green">
+                          <span>{v.label}</span>
+                          <span className="tabular-nums">−{formatMoney(v.discountMinor, s.currency!)}</span>
+                        </div>
+                      ))}
+                    </div>
+                  )}
+
                 {/* Total — a subscription is prepaid (no amount) UNLESS it owes an
                     out-of-window window charge; then show that amount. For an overstay the
                     amount is the TOP-UP delta, not the whole stay. */}

apps/web/src/SiteSettings.tsx

@@ -1,6 +1,16 @@
 import { useEffect, useState } from "react";
 import { useTranslation } from "react-i18next";
-import { fetchOccupancy, fetchSiteConfig, saveSiteConfig, type Occupancy, type SiteConfig } from "./api.js";
+import {
+  fetchOccupancy,
+  fetchSiteConfig,
+  fetchValidationPrograms,
+  saveSiteConfig,
+  saveValidationProgram,
+  type Occupancy,
+  type SiteConfig,
+  type ValidationProgramView,
+} from "./api.js";
+import { STATIONS, ValidationStationsPanel, defaultProgram, type StationId } from "./ValidationSetup.js";
 
 // Live occupancy + capacity + park metadata. Occupancy is shown to everyone (it's a
 // fold over the signed ledger); capacity and the metadata fields are admin-editable.
@@ -28,12 +38,21 @@ export function SiteSettings({ canEdit }: { canEdit: boolean }) {
   const [reserveSubs, setReserveSubs] = useState(false);
   const [anprEntry, setAnprEntry] = useState(true);
   const [msg, setMsg] = useState<string | null>(null);
+  // Merchant-validation programs (bar / lavazh). The checkboxes below toggle a
+  // station's `active` (persisted at once — each flip signs a config_change); the
+  // right-column panel edits the enabled stations. See validation-discounts.md.
+  const [programs, setPrograms] = useState<ValidationProgramView[]>([]);
 
   function reload() {
     fetchOccupancy().then(setOcc).catch(() => {});
   }
   useEffect(() => {
     reload();
+    if (canEdit) {
+      fetchValidationPrograms()
+        .then((r) => setPrograms(r.programs))
+        .catch(() => {});
+    }
     fetchSiteConfig()
       .then((c) => {
         setCapInput(c.capacity == null ? "" : String(c.capacity));
@@ -45,7 +64,23 @@ export function SiteSettings({ canEdit }: { canEdit: boolean }) {
         setMeta(m);
       })
       .catch(() => {});
-  }, []);
+  }, [canEdit]);
+
+  /** Flip a merchant station's checkbox: persist `active` at once (a signed
+   *  config_change server-side), creating the well-known row with comp defaults on
+   *  the first enable. Config details are edited in the right-column panel. */
+  async function toggleStation(id: StationId, active: boolean) {
+    const existing = programs.find((p) => p.id === id);
+    const body = existing
+      ? { ...existing, active }
+      : { ...defaultProgram(id, t(id === "bar" ? "val.enableBar" : "val.enableLavazh")), active };
+    try {
+      const saved = await saveValidationProgram(id, body);
+      setPrograms((ps) => [...ps.filter((p) => p.id !== id), saved]);
+    } catch (e) {
+      setMsg((e as Error).message);
+    }
+  }
 
   async function save() {
     setMsg(null);
@@ -68,7 +103,8 @@ export function SiteSettings({ canEdit }: { canEdit: boolean }) {
   }
 
   return (
-    <section className="card mt-6 max-w-md p-4">
+    <div className="mt-6 flex flex-wrap items-start gap-6">
+    <section className="card w-full max-w-md p-4">
       <div className="flex flex-wrap items-center gap-1.5 text-[0.8125rem]">
         <strong className="uppercase tracking-wider text-term-muted">{t("site.occupancy")}</strong>
         {occ == null ? (
@@ -127,6 +163,23 @@ export function SiteSettings({ canEdit }: { canEdit: boolean }) {
               <span className="hint block">{t("site.anprEntryHint")}</span>
             </span>
           </label>
+          <div className="border-t border-term-border pt-3 text-[0.6875rem] uppercase tracking-wider text-term-muted">
+            {t("val.sectionTitle")}
+          </div>
+          <span className="hint -mt-2">{t("val.sectionHint")}</span>
+          <div className="flex gap-6">
+            {STATIONS.map((id) => (
+              <label key={id} className="flex items-center gap-2 text-[0.75rem] text-term-text">
+                <input
+                  type="checkbox"
+                  className="accent-term-amber"
+                  checked={programs.find((p) => p.id === id)?.active ?? false}
+                  onChange={(e) => toggleStation(id, e.target.checked)}
+                />
+                {t(id === "bar" ? "val.enableBar" : "val.enableLavazh")}
+              </label>
+            ))}
+          </div>
           <div className="border-t border-term-border pt-3 text-[0.6875rem] uppercase tracking-wider text-term-muted">
             {t("site.parkDetails")}
           </div>
@@ -158,5 +211,12 @@ export function SiteSettings({ canEdit }: { canEdit: boolean }) {
         </div>
       )}
     </section>
+    {canEdit && (
+      <ValidationStationsPanel
+        programs={programs}
+        onSaved={(p) => setPrograms((ps) => [...ps.filter((x) => x.id !== p.id), p])}
+      />
+    )}
+    </div>
   );
 }

apps/web/src/ValidateScreen.tsx

@@ -0,0 +1,252 @@
+import { useEffect, useRef, useState } from "react";
+import { useTranslation } from "react-i18next";
+import {
+  applyValidation,
+  fetchMyValidationPrograms,
+  fetchValidationSession,
+  voidValidation,
+  type SessionUser,
+  type ValidationProgramView,
+  type ValidationSessionView,
+} from "./api.js";
+import { formatDuration, formatMoney, formatRelativeDateTime } from "./lib/format.js";
+
+// The MERCHANT screen (/validate): the bar/lavazh user's ENTIRE surface. Scan or key
+// the customer's ticket → see the session (deliberately NO money data — the booth
+// settles) → apply the bound program → done. Mobile-friendly: a phone/tablet on the
+// site LAN, or a booth-style USB HID scanner (it types digits + Enter into the
+// focused input). A mistake can be voided while UNUSED (append-only, signed).
+// Gated by validation:create + the server-side program↔user binding.
+// See wiki/concepts/validation-discounts.md.
+
+type Program = Omit<ValidationProgramView, "userIds">;
+
+/** Human line for what a program grants (the params live on the program row). */
+function programSummary(p: Program, t: (k: string, o?: Record<string, unknown>) => string): string {
+  if (p.mode === "comp") return t("val.modeComp");
+  if (p.mode === "timeCredit") return `${t("val.modeTimeCredit")}: ${p.minutes ?? 0} min`;
+  if (p.mode === "percent") return `${t("val.modePercent")}: ${p.percent ?? 0}%`;
+  return t("val.modeFixed");
+}
+
+export function ValidateScreen({ user }: { user: SessionUser }) {
+  const { t } = useTranslation();
+  const [programs, setPrograms] = useState<Program[] | null>(null);
+  const [programId, setProgramId] = useState<string | null>(null);
+  const [ticket, setTicket] = useState("");
+  const [view, setView] = useState<ValidationSessionView | null>(null);
+  const [amount, setAmount] = useState("");
+  const [msg, setMsg] = useState<{ kind: "ok" | "err"; text: string } | null>(null);
+  const [busy, setBusy] = useState(false);
+  const inputRef = useRef<HTMLInputElement>(null);
+
+  useEffect(() => {
+    fetchMyValidationPrograms()
+      .then((r) => {
+        setPrograms(r.programs);
+        if (r.programs.length === 1) setProgramId(r.programs[0]!.id);
+      })
+      .catch(() => setPrograms([]));
+    inputRef.current?.focus();
+  }, []);
+
+  const program = programs?.find((p) => p.id === programId) ?? null;
+
+  async function lookup(id?: string) {
+    const identity = (id ?? ticket).trim();
+    if (!identity) return;
+    setMsg(null);
+    try {
+      setView(await fetchValidationSession(identity));
+    } catch (e) {
+      setMsg({ kind: "err", text: (e as Error).message });
+    }
+  }
+
+  async function apply() {
+    if (!view || !program) return;
+    setBusy(true);
+    setMsg(null);
+    try {
+      const body: { identity: string; programId: string; amountMinor?: number } = {
+        identity: view.identity,
+        programId: program.id,
+      };
+      if (program.mode === "fixed") {
+        const n = Number(amount);
+        body.amountMinor = Number.isFinite(n) ? Math.round(n * 100) : 0;
+      }
+      await applyValidation(body);
+      setMsg({ kind: "ok", text: t("val.applied") });
+      setAmount("");
+      await lookup(view.identity);
+    } catch (e) {
+      setMsg({ kind: "err", text: (e as Error).message });
+    } finally {
+      setBusy(false);
+    }
+  }
+
+  async function voidOne(eventId: string) {
+    if (!view) return;
+    if (!window.confirm(t("val.confirmVoid"))) return;
+    setMsg(null);
+    try {
+      await voidValidation({ eventId, identity: view.identity });
+      await lookup(view.identity);
+    } catch (e) {
+      setMsg({ kind: "err", text: (e as Error).message });
+    }
+  }
+
+  // The session's blocking condition, if any (not found / closed / subscriber).
+  const blocked =
+    view == null
+      ? null
+      : !view.found
+        ? t("val.notFound")
+        : view.subscription
+          ? t("val.subscription")
+          : !view.open
+            ? t("val.closed")
+            : null;
+
+  const alreadyApplied =
+    view != null &&
+    program != null &&
+    view.validations.some((v) => v.programId === program.id && !v.voided && v.consumedBy == null);
+
+  const fixedAmountOk =
+    program?.mode !== "fixed" ||
+    (Number(amount) > 0 &&
+      (program.maxAmountMinor == null || Math.round(Number(amount) * 100) <= program.maxAmountMinor));
+
+  return (
+    <div className="mx-auto mt-6 w-full max-w-md">
+      <section className="card p-4">
+        <div className="text-[0.6875rem] uppercase tracking-wider text-term-muted">{t("val.title")}</div>
+
+        {programs != null && programs.length === 0 && (
+          <p className="mt-3 text-[0.8125rem] text-term-red">{t("val.noPrograms")}</p>
+        )}
+
+        {programs != null && programs.length > 1 && (
+          <div className="mt-3 flex gap-1">
+            {programs.map((p) => (
+              <button
+                key={p.id}
+                type="button"
+                className={`btn btn-sm ${p.id === programId ? "btn-primary" : "btn-ghost"}`}
+                onClick={() => setProgramId(p.id)}
+              >
+                {p.name}
+              </button>
+            ))}
+          </div>
+        )}
+        {program && <p className="mt-1 text-[0.75rem] text-term-muted">{program.name} — {programSummary(program, t)}</p>}
+
+        <form
+          className="mt-3 flex gap-2"
+          onSubmit={(e) => {
+            e.preventDefault();
+            void lookup();
+          }}
+        >
+          <input
+            ref={inputRef}
+            className="input flex-1 tabular-nums"
+            inputMode="numeric"
+            value={ticket}
+            onChange={(e) => setTicket(e.target.value)}
+            placeholder={t("val.scanPrompt")}
+          />
+          <button type="submit" className="btn btn-primary btn-sm">{t("val.lookup")}</button>
+        </form>
+
+        {msg && (
+          <p className={`mt-2 text-[0.8125rem] ${msg.kind === "ok" ? "text-term-green" : "text-term-red"}`}>
+            {msg.text}
+          </p>
+        )}
+
+        {view && (
+          <div className="mt-3 border-t border-term-border pt-3">
+            {blocked ? (
+              <p className="text-[0.8125rem] text-term-red">{blocked}</p>
+            ) : (
+              <>
+                <div className="flex items-baseline justify-between text-[0.8125rem]">
+                  <span className="font-semibold tabular-nums text-term-text">{view.identity}</span>
+                  <span className="text-term-muted">
+                    {t("val.entry")} {formatRelativeDateTime(view.enteredAt, t)}
+                    {view.enteredAt && <> · {formatDuration(view.enteredAt, new Date().toISOString())}</>}
+                  </span>
+                </div>
+
+                {program && !alreadyApplied && (
+                  <div className="mt-3 grid gap-2">
+                    {program.mode === "fixed" && (
+                      <div className="field">
+                        <span className="label">
+                          {t("val.amountLabel")}
+                          {program.maxAmountMinor != null && (
+                            <span className="hint ml-2">
+                              {t("val.amountHint", { max: formatMoney(program.maxAmountMinor, "") })}
+                            </span>
+                          )}
+                        </span>
+                        <input
+                          className="input w-40 tabular-nums"
+                          inputMode="decimal"
+                          value={amount}
+                          onChange={(e) => setAmount(e.target.value)}
+                          placeholder="300"
+                        />
+                      </div>
+                    )}
+                    <button
+                      type="button"
+                      className="btn btn-primary"
+                      disabled={busy || !fixedAmountOk}
+                      onClick={apply}
+                    >
+                      {t("val.apply")}
+                    </button>
+                  </div>
+                )}
+
+                {view.validations.length > 0 && (
+                  <div className="mt-3">
+                    <div className="label">{t("val.existing")}</div>
+                    <ul className="mt-1 grid gap-1">
+                      {view.validations.map((v) => (
+                        <li key={v.eventId} className="flex items-center gap-2 text-[0.75rem] text-term-text">
+                          <span>{v.label}</span>
+                          {v.amountMinor != null && <span className="tabular-nums">−{formatMoney(v.amountMinor, "")}</span>}
+                          {v.minutes != null && <span>{v.minutes} min</span>}
+                          {v.percent != null && <span>{v.percent}%</span>}
+                          {v.voided ? (
+                            <span className="text-term-muted">({t("val.voided")})</span>
+                          ) : v.consumedBy != null ? (
+                            <span className="text-term-muted">({t("val.used")})</span>
+                          ) : (
+                            v.operator === user.username && (
+                              <button type="button" className="btn btn-ghost btn-sm ml-auto" onClick={() => voidOne(v.eventId)}>
+                                {t("val.void")}
+                              </button>
+                            )
+                          )}
+                        </li>
+                      ))}
+                    </ul>
+                  </div>
+                )}
+              </>
+            )}
+          </div>
+        )}
+      </section>
+    </div>
+  );
+}

apps/web/src/ValidationSetup.tsx

@@ -0,0 +1,231 @@
+import { useEffect, useMemo, useState } from "react";
+import { useTranslation } from "react-i18next";
+import {
+  fetchUsers,
+  saveValidationProgram,
+  type ManagedUser,
+  type ValidationMode,
+  type ValidationProgramView,
+} from "./api.js";
+
+// The /setup/site RIGHT panel: per-station merchant-validation config (Bar / Lavazh).
+// The checkboxes on the left card toggle a station's `active`; this panel edits the
+// enabled stations' programs — one panel, tabs when both are on. Storage is generic
+// (validation_programs rows keyed "bar"/"lavazh"); the UI is deliberately these two
+// fixed stations. Amounts are entered in MAJOR units and stored in integer minor
+// units (the tariff-composer convention). See wiki/concepts/validation-discounts.md.
+
+/** The two well-known stations the checkboxes toggle. */
+export const STATIONS = ["bar", "lavazh"] as const;
+export type StationId = (typeof STATIONS)[number];
+
+/** A blank program draft for a station enabled for the first time. */
+export function defaultProgram(id: StationId, label: string): Omit<ValidationProgramView, "id"> {
+  return {
+    name: label,
+    mode: "comp",
+    minutes: null,
+    percent: null,
+    maxAmountMinor: null,
+    maxPerDay: null,
+    active: true,
+    userIds: [],
+  };
+}
+
+const toMinor = (s: string): number | null => {
+  const v = s.trim();
+  if (v === "") return null;
+  const n = Number(v);
+  return Number.isFinite(n) && n > 0 ? Math.round(n * 100) : null;
+};
+const fromMinor = (m: number | null): string => (m == null ? "" : String(m / 100));
+const toInt = (s: string): number | null => {
+  const v = s.trim();
+  if (v === "") return null;
+  const n = Number(v);
+  return Number.isInteger(n) && n > 0 ? n : null;
+};
+
+function StationForm({
+  program,
+  onSaved,
+}: {
+  program: ValidationProgramView;
+  onSaved: (p: ValidationProgramView) => void;
+}) {
+  const { t } = useTranslation();
+  const [name, setName] = useState(program.name);
+  const [mode, setMode] = useState<ValidationMode>(program.mode);
+  const [minutes, setMinutes] = useState(program.minutes == null ? "" : String(program.minutes));
+  const [percent, setPercent] = useState(program.percent == null ? "" : String(program.percent));
+  const [maxAmount, setMaxAmount] = useState(fromMinor(program.maxAmountMinor));
+  const [maxPerDay, setMaxPerDay] = useState(program.maxPerDay == null ? "" : String(program.maxPerDay));
+  const [userIds, setUserIds] = useState<Set<string>>(new Set(program.userIds));
+  const [users, setUsers] = useState<ManagedUser[] | null>(null);
+  const [msg, setMsg] = useState<string | null>(null);
+
+  // Reset the form when the tab switches to another station.
+  useEffect(() => {
+    setName(program.name);
+    setMode(program.mode);
+    setMinutes(program.minutes == null ? "" : String(program.minutes));
+    setPercent(program.percent == null ? "" : String(program.percent));
+    setMaxAmount(fromMinor(program.maxAmountMinor));
+    setMaxPerDay(program.maxPerDay == null ? "" : String(program.maxPerDay));
+    setUserIds(new Set(program.userIds));
+    setMsg(null);
+  }, [program.id]); // eslint-disable-line react-hooks/exhaustive-deps
+
+  useEffect(() => {
+    fetchUsers()
+      .then((r) => setUsers(r.users))
+      .catch(() => setUsers([]));
+  }, []);
+
+  const valid = useMemo(() => {
+    if (!name.trim()) return false;
+    if (mode === "timeCredit") return toInt(minutes) != null;
+    if (mode === "percent") {
+      const p = toInt(percent);
+      return p != null && p <= 100;
+    }
+    if (mode === "fixed") return toMinor(maxAmount) != null;
+    return true;
+  }, [name, mode, minutes, percent, maxAmount]);
+
+  async function save() {
+    setMsg(null);
+    try {
+      const saved = await saveValidationProgram(program.id, {
+        name: name.trim(),
+        mode,
+        minutes: mode === "timeCredit" ? toInt(minutes) : null,
+        percent: mode === "percent" ? toInt(percent) : null,
+        maxAmountMinor: mode === "fixed" ? toMinor(maxAmount) : null,
+        maxPerDay: toInt(maxPerDay),
+        active: program.active,
+        userIds: [...userIds],
+      });
+      onSaved(saved);
+      setMsg(t("val.saved"));
+    } catch (e) {
+      setMsg((e as Error).message);
+    }
+  }
+
+  const toggleUser = (id: string) =>
+    setUserIds((prev) => {
+      const next = new Set(prev);
+      next.has(id) ? next.delete(id) : next.add(id);
+      return next;
+    });
+
+  return (
+    <div className="mt-3 grid gap-3">
+      <div className="field">
+        <span className="label">{t("val.labelName")}</span>
+        <input className="input" value={name} onChange={(e) => setName(e.target.value)} placeholder={t("val.labelNamePh")} />
+      </div>
+      <div className="field">
+        <span className="label">{t("val.mode")}</span>
+        <select className="input w-fit" value={mode} onChange={(e) => setMode(e.target.value as ValidationMode)}>
+          <option value="comp">{t("val.modeComp")}</option>
+          <option value="timeCredit">{t("val.modeTimeCredit")}</option>
+          <option value="fixed">{t("val.modeFixed")}</option>
+          <option value="percent">{t("val.modePercent")}</option>
+        </select>
+      </div>
+      {mode === "timeCredit" && (
+        <div className="field">
+          <span className="label">{t("val.minutes")}</span>
+          <input className="input w-32" value={minutes} onChange={(e) => setMinutes(e.target.value)} placeholder="60" />
+        </div>
+      )}
+      {mode === "percent" && (
+        <div className="field">
+          <span className="label">{t("val.percent")}</span>
+          <input className="input w-32" value={percent} onChange={(e) => setPercent(e.target.value)} placeholder="100" />
+        </div>
+      )}
+      {mode === "fixed" && (
+        <div className="field">
+          <span className="label">{t("val.maxAmount")}</span>
+          <input className="input w-32" value={maxAmount} onChange={(e) => setMaxAmount(e.target.value)} placeholder="1000" />
+        </div>
+      )}
+      <div className="field">
+        <span className="label">{t("val.maxPerDay")}</span>
+        <input className="input w-32" value={maxPerDay} onChange={(e) => setMaxPerDay(e.target.value)} />
+      </div>
+      <div>
+        <div className="label">{t("val.users")}</div>
+        <span className="hint block">{t("val.usersHint")}</span>
+        <div className="mt-1 grid gap-1">
+          {users == null ? (
+            <span className="text-term-muted">…</span>
+          ) : users.length === 0 ? (
+            <span className="text-[0.75rem] text-term-muted">{t("val.noUsers")}</span>
+          ) : (
+            users.map((u) => (
+              <label key={u.id} className="flex items-center gap-2 text-[0.75rem] text-term-text">
+                <input
+                  type="checkbox"
+                  className="accent-term-amber"
+                  checked={userIds.has(u.id)}
+                  onChange={() => toggleUser(u.id)}
+                />
+                {u.username}
+                {u.fullName && <span className="text-term-muted">({u.fullName})</span>}
+              </label>
+            ))
+          )}
+        </div>
+      </div>
+      <div className="flex items-center gap-3">
+        <button type="button" className="btn btn-primary btn-sm" disabled={!valid} onClick={save}>
+          {t("site.save")}
+        </button>
+        {msg && <span className="text-[0.75rem] text-term-muted">{msg}</span>}
+      </div>
+    </div>
+  );
+}
+
+/** The right-column panel: tabs across the ENABLED stations, one form each. */
+export function ValidationStationsPanel({
+  programs,
+  onSaved,
+}: {
+  programs: ValidationProgramView[];
+  onSaved: (p: ValidationProgramView) => void;
+}) {
+  const { t } = useTranslation();
+  const enabled = STATIONS.map((id) => programs.find((p) => p.id === id)).filter(
+    (p): p is ValidationProgramView => p != null && p.active,
+  );
+  const [tab, setTab] = useState<string | null>(null);
+  const current = enabled.find((p) => p.id === tab) ?? enabled[0];
+  if (!current) return null;
+
+  return (
+    <section className="card w-full max-w-md p-4">
+      <div className="text-[0.6875rem] uppercase tracking-wider text-term-muted">{t("val.sectionTitle")}</div>
+      {enabled.length > 1 && (
+        <div className="mt-2 flex gap-1">
+          {enabled.map((p) => (
+            <button
+              key={p.id}
+              type="button"
+              className={`btn btn-sm ${p.id === current.id ? "btn-primary" : "btn-ghost"}`}
+              onClick={() => setTab(p.id)}
+            >
+              {t(p.id === "bar" ? "val.enableBar" : "val.enableLavazh")}
+            </button>
+          ))}
+        </div>
+      )}
+      <StationForm program={current} onSaved={onSaved} />
+    </section>
+  );
+}

apps/web/src/api.ts

@@ -7,7 +7,7 @@
 
 import { logFailedRequest } from "./lib/logger.js";
 import { apiUrl } from "./lib/origin.js";
-import type { AppLogRecord } from "@parking/shared";
+import type { AppLogRecord, ValidationLine, ValidationMode } from "@parking/shared";
 
 const CSRF_COOKIE = "parking_csrf";
 const CSRF_HEADER = "X-CSRF-Token";
@@ -1301,6 +1301,11 @@ export interface SessionLookup {
   subscriptionHolder: string | null;
   /** Advisory licence plate recognized for this session (ANPR). Null when none. */
   plate: string | null;
+  /** Merchant validations folded into `amountMinor` (which is NET): pre-discount fee,
+   *  total taken off, and the per-validation lines. See validation-discounts.md. */
+  grossMinor: number | null;
+  discountMinor: number | null;
+  validationLines: ValidationLine[];
 }
 
 /** Look up a ticket/session for the booth modal (entry/exit, paid, amount owed). */
@@ -1475,3 +1480,88 @@ export function updatePresenceBypass(patch: { radar?: boolean; camera?: boolean
 export function setCapacity(capacity: number | null): Promise<SiteConfig> {
   return saveSiteConfig({ capacity });
 }
+
+// --- Merchant validations (bar / lavazh) -----------------------------------
+// The merchant is VALIDATION-ONLY: they scan the ticket on their device and apply
+// their program; the booth settles NET of the applied validations and prints the
+// detailed receipt. Program config lives on /setup/site. See validation-discounts.md.
+
+export type { ValidationLine, ValidationMode } from "@parking/shared";
+
+/** An admin-composed program (mirrors the server row + its bound users). */
+export interface ValidationProgramView {
+  id: string;
+  name: string;
+  mode: ValidationMode;
+  minutes: number | null;
+  percent: number | null;
+  maxAmountMinor: number | null;
+  maxPerDay: number | null;
+  active: boolean;
+  userIds: string[];
+}
+
+/** A validation applied to a session, with its lifecycle state. */
+export interface AppliedValidationView {
+  eventId: string;
+  occurredAt: string;
+  programId: string;
+  label: string;
+  mode: ValidationMode;
+  minutes?: number;
+  amountMinor?: number;
+  percent?: number;
+  operator: string | null;
+  voided: boolean;
+  consumedBy: string | null;
+}
+
+/** The merchant screen's minimal session view — deliberately no money data. */
+export interface ValidationSessionView {
+  identity: string;
+  found: boolean;
+  open: boolean;
+  enteredAt: string | null;
+  subscription: boolean;
+  validations: AppliedValidationView[];
+}
+
+/** All programs + bound users (the /setup/site panel). site:read. */
+export function fetchValidationPrograms(): Promise<{ programs: ValidationProgramView[] }> {
+  return apiFetch("/api/validation/programs");
+}
+
+/** Upsert a program's config + binding set (site:update; signs a config_change). */
+export function saveValidationProgram(
+  id: string,
+  body: Omit<ValidationProgramView, "id">,
+): Promise<ValidationProgramView> {
+  return apiFetch(`/api/validation/programs/${encodeURIComponent(id)}`, {
+    method: "PUT",
+    body: JSON.stringify(body),
+  });
+}
+
+/** MY bound, active programs (the merchant screen). validation:create. */
+export function fetchMyValidationPrograms(): Promise<{ programs: Omit<ValidationProgramView, "userIds">[] }> {
+  return apiFetch("/api/validation/mine");
+}
+
+/** Merchant lookup of a scanned ticket (no money data). validation:create. */
+export function fetchValidationSession(identity: string): Promise<ValidationSessionView> {
+  return apiFetch(`/api/validation/session/${encodeURIComponent(identity)}`);
+}
+
+/** Apply my program to a ticket (signed, attributed). `amountMinor` only for fixed mode. */
+export function applyValidation(body: {
+  identity: string;
+  programId: string;
+  amountMinor?: number;
+}): Promise<{ ok: true; eventId: string; label: string }> {
+  return apiFetch("/api/validation/apply", { method: "POST", body: JSON.stringify(body) });
+}
+
+/** Void my own UNUSED validation (append-only correction). */
+export function voidValidation(body: { eventId: string; identity: string }): Promise<{ ok: true }> {
+  return apiFetch("/api/validation/void", { method: "POST", body: JSON.stringify(body) });
+}

apps/web/src/lib/i18n/en.ts

@@ -65,6 +65,7 @@ export const en: Catalog = {
     logs: "Logs",
     backup: "Backup",
     profile: "Profile",
+    validate: "Validations",
   },
   drawer: {
     stateTitle: "Drawer now",
@@ -230,6 +231,7 @@ export const en: Catalog = {
     evtCashOut: "PAY-OUT",
     evtCashReview: "REVIEW",
     evtConfigChange: "CONFIG",
+    evtValidation: "VALIDATION",
     decision: { authorize: "authorized", deny: "denied" },
     evtAnomaly: "ANOMALY",
     evtRefused: "REFUSED",
@@ -735,6 +737,51 @@ export const en: Catalog = {
     fieldPhone: "Phone",
     fieldEmail: "Email",
   },
+  // Merchant validations (bar / lavazh) — the /setup/site panel, the merchant's
+  // /validate screen, and the booth-modal discount lines. See validation-discounts.md.
+  val: {
+    // /setup/site
+    sectionTitle: "Merchant validations",
+    sectionHint: "An in-park merchant (bar / car-wash) scans the customer's ticket and grants a parking discount — payment and the receipt always stay at the booth.",
+    enableBar: "Bar",
+    enableLavazh: "Car wash",
+    labelName: "Receipt label",
+    labelNamePh: "e.g. Car wash — first hour free",
+    mode: "Discount type",
+    modeComp: "Parking fully free",
+    modeTimeCredit: "First minutes free",
+    modeFixed: "Amount off (typed at scan)",
+    modePercent: "Percent off",
+    minutes: "Free minutes",
+    percent: "Percent (%)",
+    maxAmount: "Cap per validation",
+    maxPerDay: "Max validations per day (blank = unlimited)",
+    users: "Validating users",
+    usersHint: "Only the selected users (whose role grants validation:create) can apply this program from their device.",
+    noUsers: "No users in the system — create one under Users.",
+    saved: "Saved.",
+    // /validate (the merchant screen)
+    title: "Ticket validation",
+    scanPrompt: "Scan or type the ticket number",
+    lookup: "Look up",
+    entry: "Entry:",
+    notFound: "No ticket found with this number.",
+    closed: "The ticket is closed (exited or voided).",
+    subscription: "This is a subscriber entry — not validatable.",
+    amountLabel: "Discount amount",
+    amountHint: "max {{max}}",
+    apply: "Apply validation",
+    applied: "Validation applied.",
+    existing: "Validations on this ticket",
+    voided: "voided",
+    used: "used in a payment",
+    void: "Void",
+    confirmVoid: "Void this validation?",
+    noPrograms: "You have no validation program bound to you — contact the administrator.",
+    // booth pay modal / receipts
+    gross: "Fee",
+    discount: "Discount",
+  },
   users: {
     title: "Users",
     add: "+ Add user",

apps/web/src/lib/i18n/sq.ts

@@ -68,6 +68,7 @@ export const sq = {
     logs: "Loget",
     backup: "Kopje rezervë",
     profile: "Profili",
+    validate: "Validime",
   },
   drawer: {
     stateTitle: "Arka tani",
@@ -235,6 +236,7 @@ export const sq = {
     evtCashOut: "PAGESË",
     evtCashReview: "SHQYRTIM",
     evtConfigChange: "KONFIG",
+    evtValidation: "VALIDIM",
     decision: { authorize: "autorizuar", deny: "refuzuar" },
     evtAnomaly: "ANOMALI",
     evtRefused: "REFUZUAR",
@@ -748,6 +750,51 @@ export const sq = {
     fieldPhone: "Telefoni",
     fieldEmail: "Email",
   },
+  // Merchant validations (bar / lavazh) — the /setup/site panel, the merchant's
+  // /validate screen, and the booth-modal discount lines. See validation-discounts.md.
+  val: {
+    // /setup/site
+    sectionTitle: "Validime tregtare",
+    sectionHint: "Shërbime të tjera brenda parkut (bar / lavazh) skanojnë biletën e hyrjes dhe bëjnë zbritje — pagesa dhe fatura bëhen në kabinë.",
+    enableBar: "Bar",
+    enableLavazh: "Lavazh",
+    labelName: "Etiketa në faturë",
+    labelNamePh: "p.sh. Lavazh — 1 orë falas",
+    mode: "Lloji i zbritjes",
+    modeComp: "Parkimi falas plotësisht",
+    modeTimeCredit: "Minutat e para falas",
+    modeFixed: "Zbritje shume (shkruhet në skanim)",
+    modePercent: "Zbritje në përqindje",
+    minutes: "Minuta falas",
+    percent: "Përqindja (%)",
+    maxAmount: "Tavani i zbritjes për validim",
+    maxPerDay: "Maks. validime në ditë (bosh = pa kufi)",
+    users: "Përdoruesit që validojnë",
+    usersHint: "Vetëm përdoruesit e zgjedhur (me lejen validation:create në rolin e tyre) mund të aplikojnë këtë program nga pajisja e tyre.",
+    noUsers: "Asnjë përdorues në sistem — krijojeni te Përdoruesit.",
+    saved: "U ruajt.",
+    // /validate (the merchant screen)
+    title: "Validim biletash",
+    scanPrompt: "Skanoni ose shkruani numrin e biletës",
+    lookup: "Kërko",
+    entry: "Hyrja:",
+    notFound: "Nuk u gjet biletë me këtë numër.",
+    closed: "Bileta është e mbyllur (ka dalë ose është anuluar).",
+    subscription: "Kjo është hyrje abonenti — nuk validohet.",
+    amountLabel: "Shuma e zbritjes",
+    amountHint: "maks. {{max}}",
+    apply: "Apliko validimin",
+    applied: "Validimi u aplikua.",
+    existing: "Validime në këtë biletë",
+    voided: "anuluar",
+    used: "përdorur në pagesë",
+    void: "Anulo",
+    confirmVoid: "Të anulohet ky validim?",
+    noPrograms: "Nuk keni asnjë program validimi të lidhur me ju — kontaktoni administratorin.",
+    // booth pay modal / receipts
+    gross: "Tarifa",
+    discount: "Zbritje",
+  },
   users: {
     title: "Përdoruesit",
     add: "+ Shto përdorues",

apps/web/src/router.tsx

@@ -46,6 +46,7 @@ import { DrawerManager } from "./DrawerManager.js";
 import { CARD_PAYMENTS_ENABLED } from "./lib/features.js";
 import { LogsViewer } from "./LogsViewer.js";
 import { BackupSettings } from "./BackupSettings.js";
+import { ValidateScreen } from "./ValidateScreen.js";
 import { RecycleBin } from "./RecycleBin.js";
 import { Profile } from "./Profile.js";
 // Reports pulls in Recharts (~heavy) — lazy-loaded so it stays OUT of the booth's
@@ -458,8 +459,11 @@ function RootLayout() {
       <header className="flex items-center gap-4 border-b border-term-border bg-term-panel px-4 py-2">
         <span className="text-sm font-bold uppercase tracking-widest text-term-amber">▮ Parking</span>
         <nav className="flex items-center gap-1">
-          <NavLink to="/booth" label={t("nav.booth")} />
+          {show("session:read") && <NavLink to="/booth" label={t("nav.booth")} />}
-          <NavLink to="/shifts" label={t("nav.shifts")} />
+          {show("shift:read") && <NavLink to="/shifts" label={t("nav.shifts")} />}
+          {/* The merchant's (bar/lavazh) scan-and-validate screen. Their typical role
+              grants ONLY validation:create, so this is often their whole nav. */}
+          {show("validation:create") && <NavLink to="/validate" label={t("nav.validate")} />}
           {/* Drawer — record cash movements (operator) / review them (admin). Shown if the
               user can do either. See wiki/concepts/shift.md. */}
           {(show("drawer:create") || show("drawer:review")) && (
@@ -523,7 +527,12 @@ function RootLayout() {
 const indexRoute = createRoute({
   getParentRoute: () => rootRoute,
   path: "/",
-  beforeLoad: () => {
+  beforeLoad: ({ context }) => {
+    // A merchant-only user (validation:create without the booth's session:read)
+    // lands on their scan-and-validate screen; everyone else on the booth.
+    if (can(context.user, "validation:create") && !can(context.user, "session:read")) {
+      throw redirect({ to: "/validate" });
+    }
     throw redirect({ to: "/booth" });
   },
 });
@@ -534,6 +543,20 @@ const boothRoute = createRoute({
   component: BoothScreen,
 });
 
+// The merchant (bar/lavazh) scan-and-validate screen — usually the ONLY page a
+// merchant user's role can reach. The server enforces the program↔user binding on
+// apply; this gate is defence in depth. See wiki/concepts/validation-discounts.md.
+const validateRoute = createRoute({
+  getParentRoute: () => rootRoute,
+  path: "/validate",
+  beforeLoad: ({ context }) => requirePerm("validation:create")(context),
+  component: function ValidateRoute() {
+    const { user } = rootRoute.useRouteContext();
+    if (!user) return null;
+    return <ValidateScreen user={user} />;
+  },
+});
+
 // Back-compat redirects for paths that moved. Most config screens live under /setup;
 // Subscriptions/Plans/Tariff-Lab were promoted OUT of /setup into the standalone
 // /subscriptions section (2026-06-21) — redirect the old /setup/* paths too so existing
@@ -779,6 +802,7 @@ const profileRoute = createRoute({
 const routeTree = rootRoute.addChildren([
   indexRoute,
   boothRoute,
+  validateRoute,
   ...legacyRedirects,
   profileRoute,
   shiftRoute,

apps/web/src/ui/event-detail.tsx

@@ -25,6 +25,7 @@ export const EVENT_STYLE: Record<string, { labelKey: string; color: string }> =
   cash_out: { labelKey: "booth.evtCashOut", color: "text-term-amber" },
   cash_review: { labelKey: "booth.evtCashReview", color: "text-term-cyan" },
   config_change: { labelKey: "booth.evtConfigChange", color: "text-term-amber" },
+  validation: { labelKey: "booth.evtValidation", color: "text-term-green" },
   anomaly: { labelKey: "booth.evtAnomaly", color: "text-term-red" },
 };
 

packages/db/drizzle/0024_validation_programs.sql

@@ -0,0 +1,31 @@
+-- Merchant validation programs (2026-07-13). In-park merchants (bar / lavazh) validate a
+-- customer's ticket so the BOOTH settlement discounts the fee — the merchant only
+-- validates, all money and paper stay at the booth. The /setup/site checkboxes toggle the
+-- WELL-KNOWN rows ("bar", "lavazh"); a future merchant is a new row, not a migration.
+-- Config is plainly MUTABLE (no versioning): the applied validation is a signed ledger
+-- event carrying the RESOLVED values, so reproducibility never depends on these rows.
+-- See wiki/concepts/validation-discounts.md.
+CREATE TABLE `validation_programs` (
+	`id` text PRIMARY KEY NOT NULL,
+	`name` text NOT NULL,
+	`mode` text DEFAULT 'comp' NOT NULL,
+	`minutes` integer,
+	`percent` integer,
+	`max_amount_minor` integer,
+	`max_per_day` integer,
+	`active` integer DEFAULT 0 NOT NULL,
+	`created_at` text DEFAULT (current_timestamp) NOT NULL,
+	`deleted_at` text,
+	`deleted_by` text
+);
+--> statement-breakpoint
+-- WHICH users may apply a program: the apply guard is `validation:create` AND a binding
+-- row here — a bar user can never apply the lavazh program.
+CREATE TABLE `validation_program_users` (
+	`program_id` text NOT NULL,
+	`user_id` text NOT NULL,
+	FOREIGN KEY (`program_id`) REFERENCES `validation_programs`(`id`) ON UPDATE no action ON DELETE no action,
+	FOREIGN KEY (`user_id`) REFERENCES `users`(`id`) ON UPDATE no action ON DELETE no action
+);
+--> statement-breakpoint
+CREATE UNIQUE INDEX `validation_program_users_program_id_user_id_unique` ON `validation_program_users` (`program_id`,`user_id`);

packages/db/drizzle/meta/_journal.json

@@ -169,6 +169,13 @@
       "when": 1781886600000,
       "tag": "0023_driver_id_escpos",
       "breakpoints": true
+    },
+    {
+      "idx": 24,
+      "version": "6",
+      "when": 1783948800000,
+      "tag": "0024_validation_programs",
+      "breakpoints": true
     }
   ]
 }

packages/db/scripts/reset-db.mjs

@@ -60,6 +60,11 @@ const CATEGORIES = {
     "tariff_versions",
     "tariffs",
     "subscription_plans",
+    // Merchant validation programs (bar/lavazh) + their user bindings (child first).
+    // A --users reset without --config may orphan a binding row; harmless — a binding
+    // whose user is gone grants nothing.
+    "validation_program_users",
+    "validation_programs",
   ],
   users: ["sessions", "role_permissions", "users", "roles"],
   diagnostics: ["app_logs"],

packages/db/src/schema.ts

@@ -458,6 +458,57 @@ export const subscriptionPlates = sqliteTable("subscription_plates", {
   plate: text("plate").notNull(),
 });
 
+// --- Merchant validation programs (bar / lavazh) --------------------------
+// Admin-composed master data for in-park merchant discounts: the /setup/site
+// checkboxes toggle the WELL-KNOWN rows ("bar", "lavazh") — a future merchant is a
+// new row, not a migration. Config is plainly MUTABLE (no versioning): the applied
+// validation is a signed ledger event carrying the RESOLVED values, so historical
+// reproducibility never depends on this row. Enabling/saving signs a config_change.
+// See wiki/concepts/validation-discounts.md.
+export const validationPrograms = sqliteTable("validation_programs", {
+  // Well-known slug ("bar" | "lavazh"); generic text so future merchants are rows.
+  id: text("id").primaryKey(),
+  // Receipt label printed on the booth settlement line (e.g. "Lavazh — 1 orë falas").
+  name: text("name").notNull(),
+  // How the program discounts — see @parking/shared ValidationMode.
+  mode: text("mode", { enum: ["comp", "timeCredit", "fixed", "percent"] })
+    .notNull()
+    .default("comp"),
+  // timeCredit: the free minutes.
+  minutes: integer("minutes"),
+  // percent: 1..100 off the fee.
+  percent: integer("percent"),
+  // fixed: cap on the amount the merchant may type at scan time (minor units).
+  maxAmountMinor: integer("max_amount_minor"),
+  // Anti-abuse cap: max applications per local day (null = unlimited).
+  maxPerDay: integer("max_per_day"),
+  // The /setup/site checkbox. Inactive = merchants can't apply it (row + history kept).
+  active: integer("active", { mode: "boolean" }).notNull().default(false),
+  createdAt: text("created_at")
+    .notNull()
+    .default(sql`(current_timestamp)`),
+  // Soft delete (recycle bin) — see roles.deletedAt.
+  deletedAt: text("deleted_at"),
+  deletedBy: text("deleted_by"),
+});
+
+// The program↔user binding: WHICH users may apply a program (the guard is
+// `validation:create` AND a binding row — a bar user can never apply lavazh).
+export const validationProgramUsers = sqliteTable(
+  "validation_program_users",
+  {
+    programId: text("program_id")
+      .notNull()
+      .references(() => validationPrograms.id),
+    userId: text("user_id")
+      .notNull()
+      .references(() => users.id),
+  },
+  (t) => ({
+    uniq: unique().on(t.programId, t.userId),
+  }),
+);
+
 // --- Blocklist (banlist) -------------------------------------------------
 // Plates/cards refused at ENTRY (never at exit — never trap a vehicle). A hit appends
 // a signed anomaly/refused-entry ledger event. See wiki/entities/blocklist.md.
@@ -546,5 +597,7 @@ export type SubscriptionPlanRow = typeof subscriptionPlans.$inferSelect;
 export type SubscriptionCredentialRow = typeof subscriptionCredentials.$inferSelect;
 export type SubscriptionPlateRow = typeof subscriptionPlates.$inferSelect;
 export type BlocklistRow = typeof blocklist.$inferSelect;
+export type ValidationProgramRow = typeof validationPrograms.$inferSelect;
+export type ValidationProgramUserRow = typeof validationProgramUsers.$inferSelect;
 export type SessionRow = typeof sessions.$inferSelect;
 export type AppLogRow = typeof appLogs.$inferSelect;

packages/devices/src/drivers/printer-escpos.ts

@@ -202,6 +202,9 @@ const STR = {
   tenderCard: "Kartë",
   /** "Paid:" amount label (precedes the large total). */
   amountLabel: "PAGUAR",
+  /** Merchant-validation lines: the pre-discount fee + one line per discount. */
+  gross: (v: string) => `Tarifa:   ${v}`,
+  discount: (label: string, v: string) => `${label}: -${v}`,
   /** Walk-back grace emphasis (voucher mode) — two short lines that each fit the
    *  80mm width, so neither wraps mid-word. */
   graceLines: (min: number): readonly string[] => [
@@ -413,6 +416,16 @@ export function renderReceipt(data: ReceiptData): Buffer {
     line(
       STR.tender(data.tender === "card" ? STR.tenderCard : STR.tenderCash),
     ),
+    // Merchant validations: gross fee + one line per discount, so the customer sees
+    // the full gross → discounts → net story (the big amount below is the NET).
+    ...(data.validationLines?.length
+      ? [
+          line(STR.gross(money(data.grossMinor ?? data.amountMinor, data.currency))),
+          ...data.validationLines.map((v) =>
+            line(STR.discount(v.label, money(v.discountMinor, data.currency))),
+          ),
+        ]
+      : []),
     line(),
     // The amount, large and centred.
     ALIGN_CENTER,

packages/devices/src/interfaces.ts

@@ -275,6 +275,11 @@ export interface ReceiptData {
   readonly voucher: boolean;
   /** Minutes the customer has to reach the exit after paying (voucher mode only). */
   readonly graceExitMin?: number | null;
+  /** Merchant validations (bar/lavazh): the PRE-discount fee and the per-validation
+   *  lines. When present, `amountMinor` is the NET actually paid and the receipt
+   *  shows the full gross → discounts → net story. See validation-discounts.md. */
+  readonly grossMinor?: number | null;
+  readonly validationLines?: readonly { label: string; discountMinor: number }[];
   readonly header?: TicketHeader;
 }
 

packages/shared/src/index.ts

@@ -20,6 +20,7 @@ export const RESOURCES = [
   "tariff", // read / publish a new version
   "subscription", // the subscription registry
   "site", // site_config + device setup/assign
+  "validation", // merchant validations: apply a discount to a session (bar/lavazh)
   "device", // device status / printers / snapshots / catalog
   "shift", // open/close own shift
   "drawer", // record cash receipts/disbursements (operator); review them (admin)
@@ -54,6 +55,13 @@ export const PERMISSIONS: readonly Permission[] = [
   "subscription:plan", // compose the plan catalog (admin-grade); selling = subscription:create
 
   "site:read", "site:update",
+  // Merchant validations (bar/lavazh): create = APPLY a validation to a session (the
+  // merchant user's one permission — guarded further by the program↔user binding, so a
+  // bar user can never apply the lavazh program) + void their OWN unused validation;
+  // read = see applied validations (reports/history). Program COMPOSITION needs no new
+  // permission — it lives on /setup/site behind site:update. See
+  // wiki/concepts/validation-discounts.md.
+  "validation:create", "validation:read",
   "device:read",
   "shift:read", "shift:create", "shift:cash",
   // Drawer cash movements: create (operator RECORDS a receipt/disbursement — freely, no
@@ -272,6 +280,14 @@ export type LedgerEventType =
   // the admin is NOT the adversary, but weakening an anti-fraud gate must still be
   // attributed + auditable). See wiki/concepts/entry-presence-bypass.md.
   | "config_change"
+  // A merchant validation applied to (or voided from) a transient session: the bar/
+  // lavazh user scanned the customer's ticket, so the booth settlement discounts the
+  // fee. Payload carries the RESOLVED values (programId, label, mode, minutes/
+  // amountMinor/percent) — reproducible even if the program config later changes —
+  // plus `operator` (the merchant username). A payload with `refId` set is a VOID of
+  // the referenced validation event (append-only correction, mirrors cash_review).
+  // See wiki/concepts/validation-discounts.md.
+  | "validation"
   | "anomaly";
 
 /** How money was tendered (for payment events + the shift Z-report). */
@@ -291,9 +307,25 @@ export interface LedgerPayload {
   readonly tender?: Tender;
   /** payment: which tariff_version priced it (reproducible repricing). */
   readonly tariffVersionId?: string;
-  /** payment: gross/discount/net split when a validation applied. */
+  /** payment: gross/discount/net split when a validation applied. `amountMinor` is the
+   *  NET collected; grossMinor the pre-discount fee; discountMinor what validations took
+   *  off. `validationIds` = the validation event ids this payment CONSUMED (so an
+   *  overstay's fresh period never re-applies them). */
   readonly grossMinor?: number;
   readonly discountMinor?: number;
+  readonly validationIds?: string[];
+  /** payment: the per-validation receipt lines as settled (label + amount taken off) —
+   *  stamped so the printed receipt reproduces without re-deriving the fold. */
+  readonly validationLines?: { programId: string; label: string; mode: string; discountMinor: number }[];
+  /** validation: which program (bar/lavazh) + its receipt label, frozen at apply time. */
+  readonly programId?: string;
+  readonly programLabel?: string;
+  /** validation: resolved values by mode — timeCredit's free minutes / percent off.
+   *  A fixed amount rides the shared `amountMinor`. */
+  readonly minutes?: number;
+  readonly percent?: number;
+  /** validation / cash vouchers: the username of the user who recorded it. */
+  readonly operator?: string;
   /** FX-ready, deferred: rate applied (null/absent now). See open-questions #8. */
   readonly fxRate?: number | null;
   /** void / anomaly / override: a human-readable English sentence, signed as the
@@ -326,7 +358,8 @@ export interface LedgerPayload {
    *  cash_review event, so new movements do NOT carry this. Kept so historical events
    *  still verify + display. See wiki/concepts/shift.md. */
   readonly authorizedBy?: string;
-  /** cash_review: the id of the cash_in/cash_out event this review decides on. */
+  /** cash_review: the id of the cash_in/cash_out event this review decides on.
+   *  validation: set = this event VOIDS the referenced validation event. */
   readonly refId?: string;
   /** cash_review: the admin's decision on the referenced movement. A FLAG only —
    *  neither value moves cash or touches the drawer balance. */
@@ -702,6 +735,58 @@ export interface SessionPayment {
   readonly graceExitMin: number | null;
 }
 
+// --- Merchant validations (bar / lavazh discounts) ---------------------------
+// An in-park merchant validates a customer's ticket so the BOOTH settlement charges
+// less or nothing. The program is admin-composed MUTABLE master data (no versioning:
+// the applied validation is a signed ledger event carrying the RESOLVED values, so
+// reproducibility never depends on the row). All money stays at the booth — the
+// merchant only validates. See wiki/concepts/validation-discounts.md.
+
+/** How a program discounts: full comp / first-N-minutes free / a fixed amount (typed
+ *  by the merchant at scan time, capped) / a percentage off. */
+export type ValidationMode = "comp" | "timeCredit" | "fixed" | "percent";
+export const VALIDATION_MODES: readonly ValidationMode[] = ["comp", "timeCredit", "fixed", "percent"];
+
+/** An admin-composed validation program (one per merchant station; `bar` and `lavazh`
+ *  are the well-known ids the /setup/site checkboxes toggle). */
+export interface ValidationProgram {
+  readonly id: string; // well-known slug ("bar" | "lavazh"); generic for future merchants
+  /** Receipt label, e.g. "Lavazh — 1 orë falas". Printed on the booth receipt line. */
+  readonly name: string;
+  readonly mode: ValidationMode;
+  /** timeCredit: the free minutes. */
+  readonly minutes: number | null;
+  /** percent: 1..100 off the fee. */
+  readonly percent: number | null;
+  /** fixed: cap on the amount the merchant may type at scan time (minor units). */
+  readonly maxAmountMinor: number | null;
+  /** Cap: max applications of this program per local day (null = unlimited). */
+  readonly maxPerDay: number | null;
+  readonly active: boolean;
+}
+
+/** An APPLIED validation as pricing cares about it — the RESOLVED values folded off
+ *  the signed validation event (never the mutable program row). */
+export interface SessionValidation {
+  /** The validation event id (payments record which ids they consumed). */
+  readonly eventId?: string;
+  readonly programId: string;
+  readonly label: string;
+  readonly mode: ValidationMode;
+  readonly minutes?: number; // timeCredit
+  readonly amountMinor?: number; // fixed
+  readonly percent?: number; // percent
+}
+
+/** One receipt/display line: what a validation actually saved on this settlement. */
+export interface ValidationLine {
+  readonly programId: string;
+  readonly label: string;
+  readonly mode: ValidationMode;
+  /** The (positive) amount this line took off the fee. */
+  readonly discountMinor: number;
+}
+
 /** The full pricing outcome for a session at a moment in time — what the booth's
  *  `quote()` and the exit flow compute, made PURE so it can be tested or previewed
  *  without a real ledger. See wiki/concepts/booth-exit-flow.md (overstay pricing). */
@@ -709,8 +794,14 @@ export interface SessionPricing {
   /** The window actually billed now: entry→asOf normally, or grace-expiry→asOf for an
    *  overstay (a paid session whose walk-back grace lapsed — a new period began). */
   readonly periodStart: string;
-  /** Fee for [periodStart, asOf]. */
+  /** Amount DUE for [periodStart, asOf] — NET of any merchant validations. */
   readonly amountMinor: number;
+  /** The pre-validation fee for the same period (= amountMinor when no validations). */
+  readonly grossMinor: number;
+  /** Total the validations took off (grossMinor − amountMinor). */
+  readonly discountMinor: number;
+  /** Per-validation receipt lines, in the canonical application order. */
+  readonly validationLines: ValidationLine[];
   /** True when the latest payment's grace has lapsed (overstay = new period). */
   readonly overstay: boolean;
   /** True when paid AND still inside the walk-back window (a settled, exitable stay). */
@@ -732,6 +823,15 @@ export interface SessionPricing {
  * `payments` is the session's payment history (only the LATEST matters for grace);
  * pass [] for an unpaid session. The tariff version is the one frozen at entry — the
  * customer keeps their rate card even across an overstay. See booth-exit-flow.md.
+ *
+ * `validations` are the UNCONSUMED merchant validations on the session (the caller
+ * filters out ids already recorded on a prior payment's `validationIds`, so an
+ * overstay's fresh period never re-applies them). Canonical application order —
+ * deterministic regardless of scan order: timeCredit (shifts the billed period's
+ * start forward, so "first hour free" is literal and windowed/stepped cards price
+ * the remainder correctly) → percent (of the remaining fee) → fixed amounts
+ * (clamped to the remainder) → comp (zeroes whatever is left). Net never goes
+ * below 0. See wiki/concepts/validation-discounts.md.
  */
 export function priceSession(
   enteredAt: string,
@@ -739,6 +839,7 @@ export function priceSession(
   tariff: TariffStructure,
   payments: readonly SessionPayment[] = [],
   category?: string,
+  validations: readonly SessionValidation[] = [],
 ): SessionPricing {
   const last = payments.length ? payments[payments.length - 1] : null;
   const graceExpiryMs =
@@ -748,10 +849,50 @@ export function priceSession(
   const withinGrace = graceExpiryMs != null && asOfMs <= graceExpiryMs;
   const periodStart = overstay ? new Date(graceExpiryMs!).toISOString() : enteredAt;
   // A settled (paid + within grace) session owes nothing more; otherwise bill the period.
-  const amountMinor = withinGrace ? 0 : computeFee(periodStart, asOf, tariff, category);
+  const grossMinor = withinGrace ? 0 : computeFee(periodStart, asOf, tariff, category);
+
+  // Fold the validations (nothing to discount on a settled session or a zero fee is
+  // still folded so the receipt can show "Lavazh — falas" even when gross is 0-adjacent).
+  const lines: ValidationLine[] = [];
+  let net = grossMinor;
+  if (!withinGrace && validations.length) {
+    const byMode = (m: ValidationMode) => validations.filter((v) => v.mode === m);
+    // 1. Time credits: bill as if the period started later (clamped at asOf). The
+    //    marginal saving of each credit is its line amount.
+    let startMs = Date.parse(periodStart);
+    for (const v of byMode("timeCredit")) {
+      const minutes = v.minutes ?? 0;
+      const shiftedMs = Math.min(startMs + minutes * 60_000, asOfMs);
+      const newFee = computeFee(new Date(shiftedMs).toISOString(), asOf, tariff, category);
+      lines.push({ programId: v.programId, label: v.label, mode: v.mode, discountMinor: net - newFee });
+      startMs = shiftedMs;
+      net = newFee;
+    }
+    // 2. Percent of the remaining fee (floor — integer minor units).
+    for (const v of byMode("percent")) {
+      const off = Math.floor((net * Math.min(Math.max(v.percent ?? 0, 0), 100)) / 100);
+      lines.push({ programId: v.programId, label: v.label, mode: v.mode, discountMinor: off });
+      net -= off;
+    }
+    // 3. Fixed amounts, clamped to the remainder so Σ lines ≡ gross − net.
+    for (const v of byMode("fixed")) {
+      const off = Math.min(Math.max(v.amountMinor ?? 0, 0), net);
+      lines.push({ programId: v.programId, label: v.label, mode: v.mode, discountMinor: off });
+      net -= off;
+    }
+    // 4. Comp: zero whatever is left.
+    for (const v of byMode("comp")) {
+      lines.push({ programId: v.programId, label: v.label, mode: v.mode, discountMinor: net });
+      net = 0;
+    }
+  }
+
   return {
     periodStart,
-    amountMinor,
+    amountMinor: net,
+    grossMinor,
+    discountMinor: grossMinor - net,
+    validationLines: lines,
     overstay,
     withinGrace,
     graceExpiresAt: graceExpiryMs != null ? new Date(graceExpiryMs).toISOString() : null,

packages/shared/src/tariff.test.ts

@@ -532,3 +532,104 @@ describe("explainFee — the breakdown IS the fee (2026-07-06)", () => {
     ]);
   });
 });
+
+// ---------------------------------------------------------------------------
+// (i) Merchant validations — the priceSession discount fold (2026-07-13).
+// liveV1: 5-min entry grace, 60-min increment, blocks 20000(1h)/10000(to 3h),
+// daily cap 100000, exit grace 5 min. See wiki/concepts/validation-discounts.md.
+// ---------------------------------------------------------------------------
+describe("priceSession merchant validations", () => {
+  const val = (
+    mode: "comp" | "timeCredit" | "fixed" | "percent",
+    over: Partial<import("./index.js").SessionValidation> = {},
+  ): import("./index.js").SessionValidation => ({
+    programId: "bar",
+    label: "Bar",
+    mode,
+    ...over,
+  });
+
+  it("no validations → gross == net, no lines (back-compat)", () => {
+    const r = priceSession(entered, at(120), liveV1, []);
+    expect(r.grossMinor).toBe(30000);
+    expect(r.amountMinor).toBe(30000);
+    expect(r.discountMinor).toBe(0);
+    expect(r.validationLines).toEqual([]);
+  });
+
+  it("comp zeroes the fee and the line carries the whole gross", () => {
+    const r = priceSession(entered, at(120), liveV1, [], undefined, [val("comp")]);
+    expect(r.grossMinor).toBe(30000);
+    expect(r.amountMinor).toBe(0);
+    expect(r.discountMinor).toBe(30000);
+    expect(r.validationLines).toEqual([{ programId: "bar", label: "Bar", mode: "comp", discountMinor: 30000 }]);
+  });
+
+  it("fixed subtracts, floors at 0, and clamps the line to the remainder", () => {
+    // 2h → 30000 gross; 300-off style: fixed 20000 → net 10000.
+    const r = priceSession(entered, at(120), liveV1, [], undefined, [val("fixed", { amountMinor: 20000 })]);
+    expect(r.amountMinor).toBe(10000);
+    expect(r.discountMinor).toBe(20000);
+    // Bigger than the fee → net 0, line clamped to the gross (Σ lines ≡ gross − net).
+    const r2 = priceSession(entered, at(120), liveV1, [], undefined, [val("fixed", { amountMinor: 99999 })]);
+    expect(r2.amountMinor).toBe(0);
+    expect(r2.validationLines[0]!.discountMinor).toBe(30000);
+  });
+
+  it("timeCredit prices as if entered later — 'first hour free' is literal", () => {
+    // 2h stay, 60 free minutes → bill the remaining 1h at the FIRST block (20000),
+    // exactly what a 1h stay costs.
+    const r = priceSession(entered, at(120), liveV1, [], undefined, [val("timeCredit", { minutes: 60 })]);
+    expect(r.grossMinor).toBe(30000);
+    expect(r.amountMinor).toBe(computeFee(at(60), at(120), liveV1));
+    expect(r.amountMinor).toBe(20000);
+    expect(r.validationLines[0]!.discountMinor).toBe(10000);
+  });
+
+  it("timeCredit covering the whole stay → net 0", () => {
+    const r = priceSession(entered, at(50), liveV1, [], undefined, [val("timeCredit", { minutes: 120 })]);
+    expect(r.amountMinor).toBe(0);
+    expect(r.discountMinor).toBe(r.grossMinor);
+  });
+
+  it("percent takes a floor'd share of the remaining fee", () => {
+    const r = priceSession(entered, at(120), liveV1, [], undefined, [val("percent", { percent: 50 })]);
+    expect(r.amountMinor).toBe(15000);
+    expect(r.discountMinor).toBe(15000);
+  });
+
+  it("stacking is canonical-order (timeCredit → percent → fixed → comp) and Σ lines ≡ gross − net", () => {
+    // Scan order deliberately reversed; the fold must still do time first.
+    const r = priceSession(entered, at(120), liveV1, [], undefined, [
+      val("fixed", { amountMinor: 5000, programId: "bar" }),
+      val("timeCredit", { minutes: 60, programId: "lavazh", label: "Lavazh" }),
+    ]);
+    // gross 30000 → time credit leaves 20000 → fixed 5000 → net 15000.
+    expect(r.grossMinor).toBe(30000);
+    expect(r.amountMinor).toBe(15000);
+    const sum = r.validationLines.reduce((a, l) => a + l.discountMinor, 0);
+    expect(sum).toBe(r.discountMinor);
+    expect(r.validationLines.map((l) => l.mode)).toEqual(["timeCredit", "fixed"]);
+  });
+
+  it("a settled (paid + within grace) session ignores validations", () => {
+    const r = priceSession(entered, at(123), liveV1, [{ paidAt: at(120), graceExitMin: 5 }], undefined, [
+      val("comp"),
+    ]);
+    expect(r.withinGrace).toBe(true);
+    expect(r.amountMinor).toBe(0);
+    expect(r.validationLines).toEqual([]);
+  });
+
+  it("an overstay period applies (unconsumed) validations to the FRESH period", () => {
+    // Paid at 120, grace 5 → overstay period starts at 125. A 60-min credit eats the
+    // overstay's first hour: net = fee(185→245 from period start) = the 1h price… i.e.
+    // fee of (245−125−60)=60 min from the ladder start.
+    const r = priceSession(entered, at(245), liveV1, [{ paidAt: at(120), graceExitMin: 5 }], undefined, [
+      val("timeCredit", { minutes: 60 }),
+    ]);
+    expect(r.overstay).toBe(true);
+    expect(r.grossMinor).toBe(computeFee(at(125), at(245), liveV1));
+    expect(r.amountMinor).toBe(computeFee(at(185), at(245), liveV1));
+  });
+});