diff --git a/src/models/converter/brand.converter.ts b/src/models/converter/brand.converter.ts
new file mode 100644
index 0000000..d77270d
--- /dev/null
+++ b/src/models/converter/brand.converter.ts
@@ -0,0 +1,19 @@
+import { Injectable } from '@nestjs/common';
+import { Converter } from './converter';
+import { BrandHiboutikDto } from '../hiboutikDTO/brand.hiboutik.dto';
+import { BrandCreateInput } from '../../../prisma/generated/models/Brand';
+
+@Injectable()
+export class BrandConverter extends Converter<BrandCreateInput, BrandHiboutikDto> {
+  fromHiboutik(dto: BrandHiboutikDto): BrandCreateInput {
+    return {
+      hiboutikId: dto.brand_id,
+      name: dto.brand_name,
+      enabled: dto.brand_enabled == 1,
+    };
+  }
+
+  toHiboutik(): BrandHiboutikDto {
+    throw new Error('Method not implemented.');
+  }
+}
diff --git a/src/models/converter/category.converter.ts b/src/models/converter/category.converter.ts
new file mode 100644
index 0000000..5661b03
--- /dev/null
+++ b/src/models/converter/category.converter.ts
@@ -0,0 +1,22 @@
+import { Injectable } from '@nestjs/common';
+import { CategoryHiboutikDto } from '../hiboutikDTO/category.hiboutik.dto';
+import { Converter } from './converter';
+import { CategoryCreateInput } from '../../../prisma/generated/models/Category';
+
+@Injectable()
+export class CategoryConverter extends Converter<CategoryCreateInput, CategoryHiboutikDto> {
+  /** The parent is not set here: it is linked afterwards, once every category exists (see CategoryHiboutikService). */
+  fromHiboutik(hiboutikDto: CategoryHiboutikDto): CategoryCreateInput {
+    return {
+      hiboutikId: hiboutikDto.category_id,
+      name: hiboutikDto.category_name,
+      enabled: hiboutikDto.category_enabled == 1,
+      position: Number(hiboutikDto.category_position) || 0,
+      webEnabled: hiboutikDto.category_enabled_www == 1,
+    };
+  }
+
+  toHiboutik(): CategoryHiboutikDto {
+    throw new Error('Method not implemented.');
+  }
+}
diff --git a/src/models/converter/converter.ts b/src/models/converter/converter.ts
new file mode 100644
index 0000000..b9b6a6d
--- /dev/null
+++ b/src/models/converter/converter.ts
@@ -0,0 +1,29 @@
+/**
+ * Maps a Hiboutik DTO to a Prisma input, and back. One implementation per synced entity.
+ * @typeParam Model Prisma `*CreateInput` of the entity.
+ * @typeParam Dto Hiboutik payload of the entity.
+ */
+export abstract class Converter<Model, Dto> {
+  /**
+   * Builds the Prisma input from a Hiboutik DTO. It is used for both create and update (upsert):
+   * a field set to `undefined` keeps its stored value on update, `null` erases it.
+   */
+  abstract fromHiboutik(dto: Dto): Model;
+
+  /** Not implemented yet: nothing is written back to Hiboutik. */
+  abstract toHiboutik(model: Model): Dto;
+
+  /** Returns [] for a missing or non-array input. */
+  toHiboutikList(models: Model[]): Dto[] {
+    if (!models || !Array.isArray(models)) return [];
+
+    return models.map((model) => this.toHiboutik(model));
+  }
+
+  /** Returns [] for a missing or non-array input. */
+  fromHiboutikList(hiboutikDtos: Dto[]): Model[] {
+    if (!hiboutikDtos || !Array.isArray(hiboutikDtos)) return [];
+
+    return hiboutikDtos.map((hiboutikDto) => this.fromHiboutik(hiboutikDto));
+  }
+}
diff --git a/src/models/converter/customer.converter.spec.ts b/src/models/converter/customer.converter.spec.ts
new file mode 100644
index 0000000..5329eab
--- /dev/null
+++ b/src/models/converter/customer.converter.spec.ts
@@ -0,0 +1,44 @@
+import { CustomerConverter } from './customer.converter';
+import { FullCustomerHiboutikDto } from '../hiboutikDTO/customer.hiboutik.dto';
+
+const hiboutikCustomer = (overrides: Partial<FullCustomerHiboutikDto> = {}): FullCustomerHiboutikDto =>
+  ({
+    customers_id: 42,
+    first_name: 'Jane',
+    last_name: 'Doe',
+    email: 'jane@example.com',
+    phone: '0600000000',
+    date_of_birth: '1990-05-12',
+    updated_at: '2026-06-28 17:02:55',
+    ...overrides,
+  }) as FullCustomerHiboutikDto;
+
+describe('CustomerConverter', () => {
+  const converter = new CustomerConverter();
+
+  it('maps a Hiboutik customer', () => {
+    expect(converter.fromHiboutik(hiboutikCustomer())).toEqual({
+      dateOfBirth: new Date('1990-05-12'),
+      email: 'jane@example.com',
+      firstName: 'Jane',
+      hiboutikId: 42,
+      hiboutikUpdatedAt: new Date('2026-06-28T17:02:55'),
+      lastName: 'Doe',
+      phone: '0600000000',
+    });
+  });
+
+  it('ignores an invalid date of birth', () => {
+    expect(converter.fromHiboutik(hiboutikCustomer({ date_of_birth: '0000-00-00' })).dateOfBirth).toBeUndefined();
+  });
+
+  it('keeps the stored email when Hiboutik has none (undefined)', () => {
+    expect(converter.fromHiboutik(hiboutikCustomer({ email: '' })).email).toBeUndefined();
+    expect(converter.fromHiboutik(hiboutikCustomer({ email: null as unknown as string })).email).toBeUndefined();
+  });
+
+  it('erases the phone when Hiboutik has none (null)', () => {
+    expect(converter.fromHiboutik(hiboutikCustomer({ phone: '' })).phone).toBeNull();
+    expect(converter.fromHiboutik(hiboutikCustomer({ phone: null as unknown as string })).phone).toBeNull();
+  });
+});
diff --git a/src/models/converter/customer.converter.ts b/src/models/converter/customer.converter.ts
new file mode 100644
index 0000000..1c6fb4a
--- /dev/null
+++ b/src/models/converter/customer.converter.ts
@@ -0,0 +1,25 @@
+import { Injectable } from '@nestjs/common';
+import { Converter } from './converter';
+import { CustomerCreateInput } from '../../../prisma/generated/models/Customer';
+import { FullCustomerHiboutikDto } from '../hiboutikDTO/customer.hiboutik.dto';
+import { parseHiboutikDate } from '../../utils/date';
+
+@Injectable()
+export class CustomerConverter extends Converter<CustomerCreateInput, FullCustomerHiboutikDto> {
+  fromHiboutik(dto: FullCustomerHiboutikDto): CustomerCreateInput {
+    return {
+      dateOfBirth: parseHiboutikDate(dto.date_of_birth),
+      // undefined (not null) on purpose: an email removed in Hiboutik must not erase the one stored in database
+      email: dto.email?.trim() || undefined,
+      firstName: dto.first_name,
+      hiboutikId: dto.customers_id,
+      hiboutikUpdatedAt: parseHiboutikDate(dto.updated_at),
+      lastName: dto.last_name,
+      // null (not undefined) so that a phone removed in Hiboutik is also removed in database
+      phone: dto.phone?.trim() || null,
+    };
+  }
+  toHiboutik(): FullCustomerHiboutikDto {
+    throw new Error('Method not implemented.');
+  }
+}
diff --git a/src/models/converter/product.converter.spec.ts b/src/models/converter/product.converter.spec.ts
new file mode 100644
index 0000000..24ebd64
--- /dev/null
+++ b/src/models/converter/product.converter.spec.ts
@@ -0,0 +1,59 @@
+import { ProductConverter } from './product.converter';
+import { ProductHiboutikDto } from '../hiboutikDTO/product.hiboutik.dto';
+
+const hiboutikProduct = (overrides: Partial<ProductHiboutikDto> = {}): ProductHiboutikDto => ({
+  product_id: 1,
+  product_model: 'BOUTEILLE MÉTAL ISOTHERME 260ML BT21',
+  product_barcode: '8435497280048',
+  product_brand: 1,
+  product_supplier: 2,
+  product_price: '13.99',
+  product_discount_price: '0.00',
+  product_supply_price: '7.49',
+  product_category: 19,
+  product_display_www: 0,
+  product_arch: 0,
+  products_desc: '',
+  updated_at: '2026-06-28 17:02:55',
+  product_specific_rules: [],
+  ...overrides,
+});
+
+describe('ProductConverter', () => {
+  const converter = new ProductConverter();
+
+  it('maps a Hiboutik product', () => {
+    expect(converter.fromHiboutik(hiboutikProduct())).toEqual({
+      archived: false,
+      barcode: '8435497280048',
+      brand: { connect: { hiboutikId: 1 } },
+      category: { connect: { hiboutikId: 19 } },
+      description: '',
+      discountPrice: null,
+      hiboutikId: 1,
+      hiboutikUpdatedAt: new Date('2026-06-28T17:02:55'),
+      name: 'BOUTEILLE MÉTAL ISOTHERME 260ML BT21',
+      price: '13.99',
+      enabled: false,
+      supplier: { connect: { hiboutikId: 2 } },
+    });
+  });
+
+  it('maps archived, web display and discount price', () => {
+    const product = converter.fromHiboutik(hiboutikProduct({ product_arch: 1, product_display_www: 1, product_discount_price: '9.99' }));
+    expect(product.archived).toBe(true);
+    expect(product.enabled).toBe(true);
+    expect(product.discountPrice).toBe('9.99');
+  });
+
+  it('stores an empty barcode as null', () => {
+    expect(converter.fromHiboutik(hiboutikProduct({ product_barcode: '' })).barcode).toBeNull();
+  });
+
+  it('does not link missing relations', () => {
+    const product = converter.fromHiboutik(hiboutikProduct({ product_brand: 0, product_category: 0, product_supplier: 0 }));
+    expect(product.brand).toBeUndefined();
+    expect(product.category).toBeUndefined();
+    expect(product.supplier).toBeUndefined();
+  });
+});
diff --git a/src/models/converter/product.converter.ts b/src/models/converter/product.converter.ts
new file mode 100644
index 0000000..650d649
--- /dev/null
+++ b/src/models/converter/product.converter.ts
@@ -0,0 +1,31 @@
+import { Injectable } from '@nestjs/common';
+import { Converter } from './converter';
+import { ProductHiboutikDto } from '../hiboutikDTO/product.hiboutik.dto';
+import { ProductCreateInput } from '../../../prisma/generated/models/Product';
+import { parseHiboutikDate } from '../../utils/date';
+import { parseOptionalHiboutikPrice } from '../../utils/price';
+
+@Injectable()
+export class ProductConverter extends Converter<ProductCreateInput, ProductHiboutikDto> {
+  /** `globalStock` and versions are not set here: they depend on the stocks endpoint (see ProductHiboutikService). */
+  fromHiboutik(dto: ProductHiboutikDto): ProductCreateInput {
+    return {
+      archived: dto.product_arch == 1,
+      barcode: dto.product_barcode || null,
+      brand: dto.product_brand ? { connect: { hiboutikId: dto.product_brand } } : undefined,
+      category: dto.product_category ? { connect: { hiboutikId: dto.product_category } } : undefined,
+      description: dto.products_desc,
+      discountPrice: parseOptionalHiboutikPrice(dto.product_discount_price),
+      hiboutikId: dto.product_id,
+      hiboutikUpdatedAt: parseHiboutikDate(dto.updated_at),
+      name: dto.product_model,
+      price: dto.product_price,
+      enabled: dto.product_display_www == 1,
+      supplier: dto.product_supplier ? { connect: { hiboutikId: dto.product_supplier } } : undefined,
+    };
+  }
+
+  toHiboutik(): ProductHiboutikDto {
+    throw new Error('Method not implemented.');
+  }
+}
diff --git a/src/models/converter/supplier.converter.ts b/src/models/converter/supplier.converter.ts
new file mode 100644
index 0000000..0aec1e2
--- /dev/null
+++ b/src/models/converter/supplier.converter.ts
@@ -0,0 +1,19 @@
+import { Injectable } from '@nestjs/common';
+import { SupplierHiboutikDto } from '../hiboutikDTO/supplier.hiboutik.dto';
+import { Converter } from './converter';
+import { SupplierCreateInput } from '../../../prisma/generated/models/Supplier';
+
+@Injectable()
+export class SupplierConverter extends Converter<SupplierCreateInput, SupplierHiboutikDto> {
+  fromHiboutik(dto: SupplierHiboutikDto): SupplierCreateInput {
+    return {
+      hiboutikId: dto.supplier_id,
+      name: dto.supplier_name,
+      enabled: dto.supplier_enabled == 1,
+    };
+  }
+
+  toHiboutik(): SupplierHiboutikDto {
+    throw new Error('Method not implemented.');
+  }
+}
diff --git a/src/utils/date.spec.ts b/src/utils/date.spec.ts
new file mode 100644
index 0000000..58f4198
--- /dev/null
+++ b/src/utils/date.spec.ts
@@ -0,0 +1,15 @@
+import { parseHiboutikDate } from './date';
+
+describe('parseHiboutikDate', () => {
+  it('parses a Hiboutik datetime', () => {
+    expect(parseHiboutikDate('2026-06-28 17:02:55')).toEqual(new Date('2026-06-28T17:02:55'));
+  });
+
+  it('parses a date without time', () => {
+    expect(parseHiboutikDate('1990-05-12')).toEqual(new Date('1990-05-12'));
+  });
+
+  it.each(['', '0000-00-00', '0000-00-00 00:00:00', 'not a date', null, undefined])('returns undefined for %p', (value) => {
+    expect(parseHiboutikDate(value)).toBeUndefined();
+  });
+});
diff --git a/src/utils/date.ts b/src/utils/date.ts
new file mode 100644
index 0000000..34bf91a
--- /dev/null
+++ b/src/utils/date.ts
@@ -0,0 +1,10 @@
+/**
+ * Parses a Hiboutik date ("YYYY-MM-DD HH:mm:ss" or "YYYY-MM-DD").
+ * Returns undefined for empty or invalid dates (e.g. "0000-00-00").
+ */
+export function parseHiboutikDate(value: string | null | undefined): Date | undefined {
+  if (!value) return undefined;
+
+  const date = new Date(value.trim().replace(' ', 'T'));
+  return isNaN(date.getTime()) ? undefined : date;
+}
diff --git a/src/utils/price.spec.ts b/src/utils/price.spec.ts
new file mode 100644
index 0000000..385b58d
--- /dev/null
+++ b/src/utils/price.spec.ts
@@ -0,0 +1,11 @@
+import { parseOptionalHiboutikPrice } from './price';
+
+describe('parseOptionalHiboutikPrice', () => {
+  it('keeps a positive price', () => {
+    expect(parseOptionalHiboutikPrice('12.50')).toBe('12.50');
+  });
+
+  it.each(['0.00', '0', '', 'abc', '-1.00', null, undefined])('returns null for %p', (value) => {
+    expect(parseOptionalHiboutikPrice(value)).toBeNull();
+  });
+});
diff --git a/src/utils/price.ts b/src/utils/price.ts
new file mode 100644
index 0000000..2e7060d
--- /dev/null
+++ b/src/utils/price.ts
@@ -0,0 +1,10 @@
+/**
+ * Parses an optional Hiboutik price (discount price, size price override).
+ * Hiboutik sends "0.00" when the value is not set: returns null for empty, zero or invalid values.
+ */
+export function parseOptionalHiboutikPrice(value: string | null | undefined): string | null {
+  if (!value) return null;
+
+  const price = Number(value);
+  return Number.isFinite(price) && price > 0 ? value : null;
+}