diff --git a/apps/api/src/lib/zod-utils.ts b/apps/api/src/lib/zod-utils.ts
new file mode 100644
index 0000000..d2a5ca0
--- /dev/null
+++ b/apps/api/src/lib/zod-utils.ts
@@ -0,0 +1,31 @@
+import { z } from 'zod';
+
+/**
+ * Превращает пустые строки и whitespace-only в null до валидации.
+ * Используется в API-схемах для optional-полей: фронт может слать "" вместо null
+ * (стандартный паттерн controlled inputs), API трактует это как «не задано».
+ */
+const blankToNull = (v: unknown): unknown => {
+  if (typeof v === 'string' && v.trim() === '') return null;
+  return v;
+};
+
+/** Опциональная строка с валидатором — пустая строка трактуется как null. */
+export function optionalString<T extends z.ZodType<string>>(validator: T) {
+  return z.preprocess(blankToNull, validator.nullable());
+}
+
+/** Опциональная строка без дополнительных правил, ограниченная max-длиной. */
+export function optionalText(max = 1000) {
+  return z.preprocess(blankToNull, z.string().max(max).nullable());
+}
+
+/** Опциональный email. */
+export function optionalEmail() {
+  return z.preprocess(blankToNull, z.string().email().nullable());
+}
+
+/** Опциональная строка по regex. */
+export function optionalRegex(re: RegExp) {
+  return z.preprocess(blankToNull, z.string().regex(re).nullable());
+}
diff --git a/apps/api/src/modules/clients/routes.ts b/apps/api/src/modules/clients/routes.ts
index 365751b..a0ea9dc 100644
--- a/apps/api/src/modules/clients/routes.ts
+++ b/apps/api/src/modules/clients/routes.ts
@@ -2,19 +2,18 @@ import type { FastifyInstance } from 'fastify';
 import { z } from 'zod';
 import { prisma } from '../../db.js';
 import { getOrganizationId } from '../../lib/org.js';
+import { optionalEmail, optionalRegex, optionalText } from '../../lib/zod-utils.js';
 
 const ClientUpsert = z.object({
   kind: z.enum(['ul', 'ip', 'fl']),
   name: z.string().min(1).max(500),
-  inn: z
-    .string()
-    .regex(/^\d{10}$|^\d{12}$/)
-    .nullable(),
-  kpp: z.string().regex(/^\d{9}$/).nullable(),
-  address: z.string().max(1000).nullable(),
-  email: z.string().email().nullable(),
-  phone: z.string().max(50).nullable(),
-  contactPerson: z.string().max(200).nullable(),
+  // Все необязательные поля: «пустая строка» → null до валидации (см. zod-utils.ts)
+  inn: optionalRegex(/^\d{10}$|^\d{12}$/),
+  kpp: optionalRegex(/^\d{9}$/),
+  address: optionalText(1000),
+  email: optionalEmail(),
+  phone: optionalText(50),
+  contactPerson: optionalText(200),
 });
 
 const ListQuery = z.object({
diff --git a/apps/api/src/modules/organizations/routes.ts b/apps/api/src/modules/organizations/routes.ts
index 0b85386..f06b1a3 100644
--- a/apps/api/src/modules/organizations/routes.ts
+++ b/apps/api/src/modules/organizations/routes.ts
@@ -2,18 +2,19 @@ import type { FastifyInstance } from 'fastify';
 import { z } from 'zod';
 import { prisma } from '../../db.js';
 import { getOrganizationId } from '../../lib/org.js';
+import { optionalRegex, optionalText } from '../../lib/zod-utils.js';
 
 const OrgUpdate = z.object({
   name: z.string().min(1).max(500),
   inn: z.string().regex(/^\d{10}$|^\d{12}$/),
-  kpp: z.string().regex(/^\d{9}$/).nullable(),
-  ogrn: z.string().regex(/^\d{13}$|^\d{15}$/).nullable(),
-  legalAddress: z.string().max(1000).nullable(),
-  bankName: z.string().max(500).nullable(),
-  bankBik: z.string().regex(/^\d{9}$/).nullable(),
-  bankAccount: z.string().regex(/^\d{20}$/).nullable(),
-  signatoryName: z.string().max(500).nullable(),
-  signatoryPosition: z.string().max(500).nullable(),
+  kpp: optionalRegex(/^\d{9}$/),
+  ogrn: optionalRegex(/^\d{13}$|^\d{15}$/),
+  legalAddress: optionalText(1000),
+  bankName: optionalText(500),
+  bankBik: optionalRegex(/^\d{9}$/),
+  bankAccount: optionalRegex(/^\d{20}$/),
+  signatoryName: optionalText(500),
+  signatoryPosition: optionalText(500),
 });
 
 export async function organizationsRoutes(app: FastifyInstance) {
diff --git a/apps/api/src/modules/services/routes.ts b/apps/api/src/modules/services/routes.ts
index 19d3bef..183e377 100644
--- a/apps/api/src/modules/services/routes.ts
+++ b/apps/api/src/modules/services/routes.ts
@@ -2,6 +2,7 @@ import type { FastifyInstance } from 'fastify';
 import { z } from 'zod';
 import { prisma } from '../../db.js';
 import { getOrganizationId } from '../../lib/org.js';
+import { optionalText } from '../../lib/zod-utils.js';
 
 const VatRate = z.enum(['none', 'vat_0', 'vat_5', 'vat_7', 'vat_10', 'vat_20']);
 
@@ -10,7 +11,7 @@ const ServiceUpsert = z.object({
   unit: z.string().min(1).max(50),
   defaultPriceCents: z.coerce.number().int().nonnegative(),
   defaultVat: VatRate.default('none'),
-  notes: z.string().max(2000).nullable(),
+  notes: optionalText(2000),
 });
 
 const ListQuery = z.object({
diff --git a/apps/web/src/api.ts b/apps/web/src/api.ts
index 978cfec..4b6bc5f 100644
--- a/apps/web/src/api.ts
+++ b/apps/web/src/api.ts
@@ -4,6 +4,21 @@ export class ApiError extends Error {
   constructor(public status: number, public code: string, public details?: unknown) {
     super(`${status} ${code}`);
   }
+
+  /** Удобочитаемое сообщение для UI: разворачивает zod issues если есть. */
+  prettyMessage(): string {
+    if (this.code === 'validation_error' && this.details && typeof this.details === 'object') {
+      const d = this.details as { issues?: { fieldErrors?: Record<string, string[]> } };
+      const fields = d.issues?.fieldErrors;
+      if (fields) {
+        const parts = Object.entries(fields)
+          .filter(([, msgs]) => msgs && msgs.length > 0)
+          .map(([k, msgs]) => `${k}: ${msgs!.join(', ')}`);
+        if (parts.length) return `Ошибка в полях: ${parts.join('; ')}`;
+      }
+    }
+    return `${this.code} (HTTP ${this.status})`;
+  }
 }
 
 async function request<T>(method: string, path: string, body?: unknown): Promise<T> {
diff --git a/apps/web/src/pages/Clients.tsx b/apps/web/src/pages/Clients.tsx
index cfe6767..a3970fd 100644
--- a/apps/web/src/pages/Clients.tsx
+++ b/apps/web/src/pages/Clients.tsx
@@ -64,7 +64,7 @@ export function ClientsPage() {
       setEditing(null);
       await load();
     } catch (e) {
-      setError(e instanceof ApiError ? `${e.code} (${e.status})` : String(e));
+      setError(e instanceof ApiError ? e.prettyMessage() : String(e));
     }
   }
 
diff --git a/apps/web/src/pages/DocumentEdit.tsx b/apps/web/src/pages/DocumentEdit.tsx
index a264ec6..3ca0cdd 100644
--- a/apps/web/src/pages/DocumentEdit.tsx
+++ b/apps/web/src/pages/DocumentEdit.tsx
@@ -162,7 +162,7 @@ export function DocumentEditPage() {
         setSavedAt(new Date());
       }
     } catch (e) {
-      setError(e instanceof ApiError ? `${e.code} (${e.status})` : String(e));
+      setError(e instanceof ApiError ? e.prettyMessage() : String(e));
     } finally {
       setSaving(false);
     }
@@ -185,7 +185,7 @@ export function DocumentEditPage() {
       await api.del(`/api/documents/${savedId}`);
       navigate('/documents');
     } catch (e) {
-      setError(e instanceof ApiError ? `${e.code} (${e.status})` : String(e));
+      setError(e instanceof ApiError ? e.prettyMessage() : String(e));
     }
   }
 
diff --git a/apps/web/src/pages/Organization.tsx b/apps/web/src/pages/Organization.tsx
index 9922fa8..74341fb 100644
--- a/apps/web/src/pages/Organization.tsx
+++ b/apps/web/src/pages/Organization.tsx
@@ -46,7 +46,7 @@ export function OrganizationPage() {
       setDraft(saved);
       setSavedAt(new Date());
     } catch (e) {
-      setError(e instanceof ApiError ? `${e.code} (${e.status})` : String(e));
+      setError(e instanceof ApiError ? e.prettyMessage() : String(e));
     } finally {
       setSaving(false);
     }
diff --git a/apps/web/src/pages/Services.tsx b/apps/web/src/pages/Services.tsx
index 4e0f485..33174dd 100644
--- a/apps/web/src/pages/Services.tsx
+++ b/apps/web/src/pages/Services.tsx
@@ -95,7 +95,7 @@ export function ServicesPage() {
       setEditing(null);
       await load();
     } catch (e) {
-      setError(e instanceof ApiError ? `${e.code} (${e.status})` : String(e));
+      setError(e instanceof ApiError ? e.prettyMessage() : String(e));
     }
   }
 
diff --git a/apps/web/src/pages/TemplateEdit.tsx b/apps/web/src/pages/TemplateEdit.tsx
index 03db8b0..c74cbba 100644
--- a/apps/web/src/pages/TemplateEdit.tsx
+++ b/apps/web/src/pages/TemplateEdit.tsx
@@ -35,7 +35,7 @@ export function TemplateEditPage() {
       await api.put(`/api/templates/${id}`, { name, docType, body });
       setSavedAt(new Date());
     } catch (e) {
-      setError(e instanceof ApiError ? `${e.code} (${e.status})` : String(e));
+      setError(e instanceof ApiError ? e.prettyMessage() : String(e));
     } finally {
       setSaving(false);
     }