fix(tariff): reject stepped base combined with time/seasonal tiers

A stepped ("up-to") default card prices the whole stay as one total, so the V2
engine short-circuits to steppedFee and NEVER consults windowed cards — any
time/seasonal tiers would silently never fire. Found live: an active tariff had a
stepped base plus weekday-night + weekend tiers, and every 3h stay priced 600 ALL
regardless of hour/day because the tiers were dead.

- validateTariffV2 now rejects a stepped defaultCard combined with windowedCards,
  with an actionable message (switch the base to ladder/flat, or remove the tiers).
- Composer shows an inline red warning the moment base mode is stepped and tiers
  exist; publishing is blocked server-side regardless.
- ApiError now carries the server's problems[], so the publish error surfaces the
  SPECIFIC reason instead of a generic "invalid tariff structure".
- 2 new validation tests (55 pass).

Wiki: tariff, log.

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V

apps/web/src/TariffComposer.tsx

@@ -341,8 +341,8 @@ export function TariffComposer() {
       setMsg({ kind: "ok", text: t("tariff.publishedOk") });
     } catch (e) {
       const text =
-        e instanceof ApiError && (e as ApiError & { problems?: string[] }).problems
-          ? `${e.message}: ${((e as ApiError & { problems?: string[] }).problems ?? []).join("; ")}`
+        e instanceof ApiError && e.problems?.length
+          ? `${e.message}: ${e.problems.join("; ")}`
           : (e as Error).message;
       setMsg({ kind: "err", text });
     } finally {
@@ -404,6 +404,13 @@ export function TariffComposer() {
       <details className="mt-6" open={form.tiers.length > 0}>
         <summary className="cursor-pointer text-h6 font-semibold uppercase tracking-wider text-term-text">{t("tariff.tiersAdvanced")}</summary>
         <p className="hint mt-1.5 mb-2">{t("tariff.tiersHint")}</p>
+        {/* A stepped ("up-to") base rate cannot be combined with time tiers — the
+            engine would ignore them. Warn up-front; publishing is also blocked server-side. */}
+        {form.base.mode === "stepped" && form.tiers.length > 0 && (
+          <p className="mb-3 rounded-term border border-term-red/50 bg-term-red/10 px-3 py-2 text-[12px] text-term-red">
+            {t("tariff.steppedTiersConflict")}
+          </p>
+        )}
         {form.tiers.map((tr, i) => (
           <fieldset key={i} className="card mb-3 p-4">
             <legend className="flex items-center gap-2 px-1">

apps/web/src/api.ts

@@ -29,7 +29,7 @@ export async function apiFetch<T>(path: string, init: RequestInit = {}): Promise
   }
   const res = await fetch(path, { ...init, headers, credentials: "include" });
   if (!res.ok) {
-    const msg = (await res.json().catch(() => ({}))) as { error?: string };
+    const msg = (await res.json().catch(() => ({}))) as { error?: string; problems?: string[] };
     const error = msg.error ?? `${path}: ${res.status}`;
     // Ship the failed request to the backend log store (best-effort, loop-safe — the
     // logger itself never logs the /api/logs call). 401s are normal pre-login churn,
@@ -37,7 +37,7 @@ export async function apiFetch<T>(path: string, init: RequestInit = {}): Promise
     if (res.status !== 401) {
       logFailedRequest({ path, method, status: res.status, error });
     }
-    throw new ApiError(error, res.status);
+    throw new ApiError(error, res.status, msg.problems);
   }
   if (res.status === 204) return undefined as T;
   return res.json() as Promise<T>;
@@ -47,6 +47,8 @@ export class ApiError extends Error {
   constructor(
     message: string,
     readonly status: number,
+    /** Field-level problems from a validation error (e.g. tariff publish), if any. */
+    readonly problems?: string[],
   ) {
     super(message);
   }

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

@@ -243,6 +243,8 @@ export const en: Catalog = {
     stepUpTo: "Up to",
     stepTotal: "Total price",
     addStep: "+ Add row",
+    steppedTiersConflict:
+      "⚠ Time/seasonal tiers do NOT apply when the base rate is 'By duration (up-to)' — the engine ignores them entirely. Remove the tiers, or switch the base rate to 'Hourly ladder' or 'Flat price'. Publishing is blocked until this is fixed.",
     tiersAdvanced: "Advanced: time & seasonal tiers",
     tiersHint: "Optional. Add tiers that apply only at certain hours/days/dates or for a category (e.g. happy hour, night rate, weekend, bus). With no tiers, just the base rate is published.",
     tierName: "Name",

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

@@ -246,6 +246,8 @@ export const sq = {
     stepUpTo: "Deri në",
     stepTotal: "Çmimi total",
     addStep: "+ Shto rresht",
+    steppedTiersConflict:
+      "⚠ Nivelet kohore/sezonale NUK zbatohen kur tarifa bazë është 'Sipas kohëzgjatjes (deri-në)' — motori i shpërfill plotësisht. Hiqi nivelet, ose ndrysho tarifën bazë në 'Shkallë orësh' a 'Çmim fiks'. Publikimi bllokohet derisa kjo të rregullohet.",
     tiersAdvanced: "Të avancuara: nivele kohore & sezonale",
     tiersHint: "Opsionale. Shto nivele tarifore që vlejnë vetëm në orë/ditë/data ose kategori të caktuara (p.sh. orë e lirë, tarifë nate, fundjavë, autobus). Pa nivele, publikohet vetëm tarifa bazë.",
     tierName: "Emri",

packages/shared/src/index.ts

@@ -833,6 +833,17 @@ function validateTariffV2(t: Partial<TariffStructureV2>): string[] {
     cards.forEach((c, i) => validateCard(c, `windowedCards[${i}]`, false, errs));
   }
 
+  // A STEPPED base (an "up-to" total-by-duration table) prices the WHOLE stay as one
+  // number — it cannot be sliced per-increment, so windowed (time/seasonal) tiers have
+  // nothing to override and the engine ignores them entirely. Forbid the combination
+  // rather than let an operator publish tiers that silently never fire. (Switch the base
+  // to an hourly ladder / flat rate to use tiers, or remove the tiers.)
+  if (t.defaultCard != null && hasSteps(t.defaultCard) && cards.length > 0) {
+    errs.push(
+      "time/seasonal tiers do not apply to an up-to-duration (stepped) base rate — remove the tiers, or switch the base rate to an hourly ladder or flat price",
+    );
+  }
+
   // Precedence determinism: reject two cards (same category bucket) that tie on
   // (specificity, priority) with overlapping windows — the operator must break the
   // tie with priority rather than relying silently on the name tiebreak.

packages/shared/src/tariff.test.ts

@@ -229,6 +229,19 @@ describe("validate V2", () => {
     const errs = validateTariffStructure({ ...base, defaultCard: { ...okDefault, window: { dow: [1] } } });
     expect(errs).toContain("defaultCard must not have a window (it is the always-active fallback)");
   });
+  it("rejects a STEPPED base card combined with windowed tiers (they would be ignored)", () => {
+    const steppedDefault: TariffCard = { name: "d", priority: 0, steps: [{ uptoMin: 60, totalMinor: 200 }] };
+    const errs = validateTariffStructure({
+      ...base,
+      defaultCard: steppedDefault,
+      windowedCards: [{ name: "night", priority: 1, window: { dow: [1] }, blocks: ladder(5000) }],
+    });
+    expect(errs.some((e) => /up-to-duration \(stepped\) base/.test(e))).toBe(true);
+  });
+  it("accepts a STEPPED base card with NO tiers", () => {
+    const steppedDefault: TariffCard = { name: "d", priority: 0, steps: [{ uptoMin: 60, totalMinor: 200 }] };
+    expect(validateTariffStructure({ ...base, defaultCard: steppedDefault })).toEqual([]);
+  });
   it("rejects a bad hour format", () => {
     const errs = validateTariffStructure({ ...base, defaultCard: okDefault, windowedCards: [{ name: "w", priority: 1, window: { fromHour: "25:00", toHour: "26:00" }, blocks: ladder(5000) }] });
     expect(errs.some((e) => e.includes("fromHour"))).toBe(true);

wiki/concepts/tariff.md

@@ -94,6 +94,14 @@ A card's body is **one of three mutually-exclusive shapes** — `flatMinor`, `bl
 - A `steps` table **replaces** the `blocks` ladder and **forbids `dailyCapMinor`** (the top tier IS
   the per-day cap). In V2 it is allowed **only on the `defaultCard`** — a whole-stay total can't be
   sliced per-increment by a windowed card, so windowed/stepped don't compose.
+- **A stepped base + time/seasonal tiers is REJECTED** (`validateTariffV2`, 2026-06-20). The engine
+  short-circuits to `steppedFee` on a stepped default card and never consults windowed cards, so any
+  tiers would **silently never fire**. Rather than publish dead tiers, validation refuses the combo
+  ("time/seasonal tiers do not apply to an up-to-duration (stepped) base rate — remove the tiers, or
+  switch the base rate to an hourly ladder or flat price"); the composer also shows an inline red
+  warning the moment both are present. (Discovered live: an active version had a stepped base AND
+  weekday-night + weekend tiers; the tiers priced nothing — every 3h stay was the stepped 600
+  regardless of time. The `problems[]` array now surfaces through `ApiError` to the publish message.)
 - Validation: ≥1 row, strictly-ascending positive `uptoMin`, non-negative integer totals (totals
   need not be monotonic — an owner *may* price a longer stay cheaper).
 

wiki/log.md

@@ -1040,3 +1040,16 @@ addStep (sq+en). 8 new unit tests incl. the exact owner matrix + multi-day + ove
 + validation (53 pass). VERIFIED end-to-end via the real UI: authored the matrix in the
 composer, published, Tariff Lab priced it exactly (3h->500, 6h->800, 12h->1000,
 2d->2000). Build+lint green. Updated [[tariff]].
+
+## [2026-06-20] fix | Reject stepped base + time tiers (silently-ignored tiers)
+
+Found live: the active tariff had a STEPPED ("up-to") base card AND two windowed tiers
+(weekday-night "Nata gjate javes", weekend "Fundjava"). computeFeeV2 short-circuits to
+steppedFee on a stepped default card, so the tiers NEVER fired — a 3h stay was 600 ALL
+at every hour/day. The composer happily let this contradictory combo be built + published.
+Fix: validateTariffV2 now rejects a stepped defaultCard combined with windowedCards
+(clear message: switch base to ladder/flat or remove tiers); the composer shows an inline
+red warning when base.mode==="stepped" && tiers>0. Also: ApiError now carries the
+server's problems[] so the publish error shows the SPECIFIC reason (was generic "invalid
+tariff structure"). 2 new validation tests (55 pass). Verified live: warning renders +
+publish blocked with the full message. Build+lint green. Updated [[tariff]].