diff --git a/README.md b/README.md
index 9e40008..afdac88 100644
--- a/README.md
+++ b/README.md
@@ -186,6 +186,31 @@ premier endpoint à combiner `requireAuth`/`AuthLocals` avec un handler async, c
 a mis au jour une contrainte générique trop stricte, corrigée à la source :
 [specs/backend-architecture.md](specs/backend-architecture.md).
 
+## Données de référence — régimes & allergènes (apps/api)
+
+- `GET /reference/diets` — liste des régimes alimentaires (`Diet`, 5 valeurs seedées).
+- `GET /reference/allergies` — liste des allergènes sélectionnables, `{ id, name }`
+  (le nom vient de `Category.name` — la table `allergy` elle-même ne porte pas de
+  nom, voir `schema.prisma` — chaque allergène = une `Category` + une unique
+  `Allergy` sous cette catégorie).
+
+Les deux sont **publics** (pas de `requireAuth`) : ce sont des données de référence,
+pas des données de foyer, et le wizard d'inscription doit pouvoir les lire avant
+qu'un compte (donc une session) n'existe.
+
+Données seedées via `apps/api/prisma/seed.ts` (`pnpm --filter api prisma:seed`, ou
+automatiquement après `prisma migrate reset` — config `prisma.seed` dans
+`package.json`). La logique réelle (listes + upsert idempotent) vit dans
+`src/db/reference-seed-data.ts`, partagée avec `test-support/reset-db.ts` : chaque
+test repart d'une base **avec** ces données de référence, pas de tables vides —
+nécessaire pour tester `dietId`/`allergyIds` sur de vraies lignes.
+
+`Diet.name` et `Category.name` sont `@unique` — ajouté à ce schéma (pas dans le doc
+spec d'origine) précisément pour permettre cet upsert idempotent par nom.
+
+Liste des 14 allergènes : ceux du règlement UE 1169/2011 (annexe II) — liste
+standard, pas inventée.
+
 ## Page de connexion / inscription (apps/web)
 
 - `src/api/client.ts` — `ApiClient` (classe, instance unique exportée `apiClient`) :
diff --git a/apps/api/features/reference.feature b/apps/api/features/reference.feature
new file mode 100644
index 0000000..10b7718
--- /dev/null
+++ b/apps/api/features/reference.feature
@@ -0,0 +1,14 @@
+Feature: Reference data (diets, allergens)
+  As a visitor filling in the signup wizard, or a signed-in user editing their profile
+  I want to read the list of dietary regimes and allergens
+  So that I can pick from them — before an account necessarily exists
+
+  Scenario: A visitor without a session can read the list of dietary regimes
+    When I send a GET request to "/reference/diets"
+    Then the response status should be 200
+    And the reference list response should include "Végétarien"
+
+  Scenario: A visitor without a session can read the list of allergens
+    When I send a GET request to "/reference/allergies"
+    Then the response status should be 200
+    And the reference list response should include "Arachides"
diff --git a/apps/api/features/step-definitions/reference.steps.ts b/apps/api/features/step-definitions/reference.steps.ts
new file mode 100644
index 0000000..e4e7c1b
--- /dev/null
+++ b/apps/api/features/step-definitions/reference.steps.ts
@@ -0,0 +1,11 @@
+import assert from "node:assert/strict";
+import { Then } from "@cucumber/cucumber";
+import type { CustomWorld } from "../support/world.js";
+
+Then(
+  "the reference list response should include {string}",
+  function (this: CustomWorld, name: string) {
+    const names = (this.response.body as Array<{ name: string }>).map((item) => item.name);
+    assert.ok(names.includes(name), `expected ${JSON.stringify(names)} to include "${name}"`);
+  },
+);
diff --git a/apps/api/package.json b/apps/api/package.json
index c7860cc..ddb49cb 100644
--- a/apps/api/package.json
+++ b/apps/api/package.json
@@ -11,8 +11,12 @@
     "test:bdd": "cross-env NODE_ENV=test NODE_OPTIONS=--import=tsx cucumber-js",
     "prisma:generate": "prisma generate",
     "prisma:migrate": "prisma migrate dev",
+    "prisma:seed": "prisma db seed",
     "postinstall": "prisma generate"
   },
+  "prisma": {
+    "seed": "tsx prisma/seed.ts"
+  },
   "dependencies": {
     "@batch-cooking/error-tools": "workspace:*",
     "@batch-cooking/express-tools": "workspace:*",
diff --git a/apps/api/prisma/migrations/20260816230050_unique_diet_category_name/migration.sql b/apps/api/prisma/migrations/20260816230050_unique_diet_category_name/migration.sql
new file mode 100644
index 0000000..09919e5
--- /dev/null
+++ b/apps/api/prisma/migrations/20260816230050_unique_diet_category_name/migration.sql
@@ -0,0 +1,5 @@
+-- CreateIndex
+CREATE UNIQUE INDEX "category_name_key" ON "category"("name");
+
+-- CreateIndex
+CREATE UNIQUE INDEX "diet_name_key" ON "diet"("name");
diff --git a/apps/api/prisma/schema.prisma b/apps/api/prisma/schema.prisma
index c94073e..2d92313 100644
--- a/apps/api/prisma/schema.prisma
+++ b/apps/api/prisma/schema.prisma
@@ -22,9 +22,13 @@ model House {
   @@map("house")
 }
 
+/// `name` is `@unique` — not in the original spec doc, added so the seed
+/// script (prisma/seed.ts) can `upsert` by name and stay idempotent/safe to
+/// re-run, and so two reference rows can never silently duplicate the same
+/// regime.
 model Diet {
   id   Int    @id @default(autoincrement())
-  name String
+  name String @unique
 
   users UserProfile[]
 
@@ -32,9 +36,10 @@ model Diet {
 }
 
 /// Enumeration-style table, meant to grow over time (e.g. allergy nuances).
+/// `name` is `@unique` for the same reason as `Diet.name` above.
 model Category {
   id   Int    @id @default(autoincrement())
-  name String
+  name String @unique
 
   allergies Allergy[]
 
diff --git a/apps/api/prisma/seed.ts b/apps/api/prisma/seed.ts
new file mode 100644
index 0000000..87534e6
--- /dev/null
+++ b/apps/api/prisma/seed.ts
@@ -0,0 +1,18 @@
+import { PrismaClient } from "@prisma/client";
+import { seedReferenceData } from "../src/db/reference-seed-data.js";
+
+// Standalone CLI entry point (not `src/db/prisma.ts` — that module pulls in
+// the rest of the app's config/env plumbing this doesn't need), run via
+// `prisma db seed` (see the `prisma.seed` entry in package.json) — either
+// directly (`pnpm --filter api prisma:seed`) or automatically after
+// `prisma migrate reset`. The actual data/logic lives in
+// `src/db/reference-seed-data.ts`, shared with `test-support/reset-db.ts`.
+const prisma = new PrismaClient();
+
+seedReferenceData(prisma)
+  .then(() => prisma.$disconnect())
+  .catch(async (err) => {
+    console.error(err);
+    await prisma.$disconnect();
+    process.exit(1);
+  });
diff --git a/apps/api/src/app.ts b/apps/api/src/app.ts
index 63baf0f..6b6e2f7 100644
--- a/apps/api/src/app.ts
+++ b/apps/api/src/app.ts
@@ -5,6 +5,7 @@ import type { Express, Request, Response } from "express";
 import { env } from "./config/env.js";
 import { authRouter } from "./modules/auth/auth.routes.js";
 import { planningRouter } from "./modules/planning/planning.routes.js";
+import { referenceRouter } from "./modules/reference/reference.routes.js";
 
 /**
  * Builds the API's `ExpressServer`: standard middleware, routes, and the
@@ -24,6 +25,7 @@ export function createServer(): ExpressServer {
 
   server.mountRouter("/auth", authRouter);
   server.mountRouter("/planning", planningRouter);
+  server.mountRouter("/reference", referenceRouter);
 
   // No route matched — same shape as every other error response, via the
   // shared ErrorCode contract, so clients never special-case 404s.
diff --git a/apps/api/src/db/reference-seed-data.ts b/apps/api/src/db/reference-seed-data.ts
new file mode 100644
index 0000000..ef0d449
--- /dev/null
+++ b/apps/api/src/db/reference-seed-data.ts
@@ -0,0 +1,55 @@
+import type { PrismaClient } from "@prisma/client";
+
+// Short, optional-to-pick regime list — `UserProfile.dietId` stays
+// nullable, this is not meant to be exhaustive.
+const DIETS = ["Omnivore", "Végétarien", "Végan", "Pescétarien", "Sans gluten"];
+
+// The 14 allergens EU Regulation 1169/2011 (Annex II) requires food
+// businesses to declare — a standard, defensible reference list rather than
+// an invented one.
+const ALLERGENS = [
+  "Gluten",
+  "Crustacés",
+  "Œufs",
+  "Poissons",
+  "Arachides",
+  "Soja",
+  "Lait",
+  "Fruits à coque",
+  "Céleri",
+  "Moutarde",
+  "Graines de sésame",
+  "Sulfites",
+  "Lupin",
+  "Mollusques",
+];
+
+/**
+ * Populates the `Diet`/`Category`/`Allergy` reference tables. Idempotent
+ * (safe to call against a database that already has this data — upserts by
+ * `name`, both `@unique`) — used both by `prisma/seed.ts` (the CLI entry
+ * point, `prisma db seed`) and by `test-support/reset-db.ts` (so every
+ * test starts from the same realistic reference data the real app seeds,
+ * not an empty table).
+ */
+export async function seedReferenceData(prisma: PrismaClient): Promise<void> {
+  for (const name of DIETS) {
+    await prisma.diet.upsert({ where: { name }, update: {}, create: { name } });
+  }
+
+  // `Allergy` itself carries no `name` — it's the selectable instance of a
+  // named `Category` (see schema.prisma) — so seeding an allergen means one
+  // Category (upserted by name) plus exactly one Allergy row under it,
+  // created only the first time.
+  for (const name of ALLERGENS) {
+    const category = await prisma.category.upsert({
+      where: { name },
+      update: {},
+      create: { name },
+    });
+    const existing = await prisma.allergy.findFirst({ where: { categoryId: category.id } });
+    if (!existing) {
+      await prisma.allergy.create({ data: { categoryId: category.id } });
+    }
+  }
+}
diff --git a/apps/api/src/modules/reference/reference.routes.ts b/apps/api/src/modules/reference/reference.routes.ts
new file mode 100644
index 0000000..cd3e02a
--- /dev/null
+++ b/apps/api/src/modules/reference/reference.routes.ts
@@ -0,0 +1,26 @@
+import { wrapAsyncHandler } from "@batch-cooking/express-tools";
+import { Router } from "express";
+import { getAllergies, getDiets } from "./reference.service.js";
+
+/**
+ * Router mounted at `/reference` in app.ts. Both routes are deliberately
+ * public (no `requireAuth`) — this is static reference data, not
+ * per-household state, and the signup wizard (household/regime/allergen
+ * steps) needs to read it before an account — and therefore a session —
+ * exists.
+ */
+export const referenceRouter = Router();
+
+referenceRouter.get(
+  "/diets",
+  wrapAsyncHandler(async (_req, res) => {
+    res.status(200).json(await getDiets());
+  }),
+);
+
+referenceRouter.get(
+  "/allergies",
+  wrapAsyncHandler(async (_req, res) => {
+    res.status(200).json(await getAllergies());
+  }),
+);
diff --git a/apps/api/src/modules/reference/reference.service.ts b/apps/api/src/modules/reference/reference.service.ts
new file mode 100644
index 0000000..699d304
--- /dev/null
+++ b/apps/api/src/modules/reference/reference.service.ts
@@ -0,0 +1,21 @@
+import type { AllergyView, DietView } from "@batch-cooking/shared";
+import { prisma } from "../../db/prisma.js";
+
+/** All reference dietary regimes, alphabetically — small, static list (see prisma/seed.ts). */
+export async function getDiets(): Promise<DietView[]> {
+  return prisma.diet.findMany({ orderBy: { name: "asc" } });
+}
+
+/**
+ * All reference allergens, alphabetically. `Allergy` carries no `name` of
+ * its own — it's the selectable instance of a named `Category` (see
+ * schema.prisma) — so this resolves each allergen's display name from its
+ * category and flattens the split away for callers.
+ */
+export async function getAllergies(): Promise<AllergyView[]> {
+  const allergies = await prisma.allergy.findMany({
+    include: { category: { select: { name: true } } },
+    orderBy: { category: { name: "asc" } },
+  });
+  return allergies.map((allergy) => ({ id: allergy.id, name: allergy.category.name }));
+}
diff --git a/apps/api/test-support/reset-db.ts b/apps/api/test-support/reset-db.ts
index cdbf1f2..9b5b54e 100644
--- a/apps/api/test-support/reset-db.ts
+++ b/apps/api/test-support/reset-db.ts
@@ -1,7 +1,12 @@
 import { prisma } from "../src/db/prisma.js";
+import { seedReferenceData } from "../src/db/reference-seed-data.js";
 
 // Single TRUNCATE ... CASCADE covers FK ordering and resets identity
 // sequences — used between tests/scenarios to start from a clean slate.
+// Re-seeds the Diet/Category/Allergy reference data right after truncating
+// it, so every test starts from the same realistic reference data the real
+// app seeds (`prisma/seed.ts`) rather than empty tables — tests exercising
+// dietId/allergyIds need real rows to reference.
 export async function resetDatabase() {
   await prisma.$executeRawUnsafe(`
     TRUNCATE TABLE
@@ -12,4 +17,5 @@ export async function resetDatabase() {
       "user_profiles", "diet", "house"
     RESTART IDENTITY CASCADE;
   `);
+  await seedReferenceData(prisma);
 }
diff --git a/apps/api/test/reference.test.ts b/apps/api/test/reference.test.ts
new file mode 100644
index 0000000..d8963a3
--- /dev/null
+++ b/apps/api/test/reference.test.ts
@@ -0,0 +1,39 @@
+import { expect } from "chai";
+import request from "supertest";
+import { createApp } from "../src/app.js";
+import { prisma } from "../src/db/prisma.js";
+import { resetDatabase } from "../test-support/reset-db.js";
+
+describe("Reference data", () => {
+  const app = createApp();
+
+  beforeEach(async () => {
+    await resetDatabase();
+  });
+
+  after(async () => {
+    await prisma.$disconnect();
+  });
+
+  describe("GET /reference/diets", () => {
+    it("returns the seeded regimes, no session required", async () => {
+      const res = await request(app).get("/reference/diets");
+
+      expect(res.status).to.equal(200);
+      expect(res.body).to.have.length(5);
+      expect(res.body.map((d: { name: string }) => d.name)).to.include("Végétarien");
+      expect(res.body[0]).to.have.keys(["id", "name"]);
+    });
+  });
+
+  describe("GET /reference/allergies", () => {
+    it("returns the seeded allergens with their name resolved, no session required", async () => {
+      const res = await request(app).get("/reference/allergies");
+
+      expect(res.status).to.equal(200);
+      expect(res.body).to.have.length(14);
+      expect(res.body.map((a: { name: string }) => a.name)).to.include("Arachides");
+      expect(res.body[0]).to.have.keys(["id", "name"]);
+    });
+  });
+});
diff --git a/packages/shared/src/index.ts b/packages/shared/src/index.ts
index f0dc809..c600342 100644
--- a/packages/shared/src/index.ts
+++ b/packages/shared/src/index.ts
@@ -7,4 +7,5 @@ export * from "./errors/error-codes.js";
 export * from "./schemas/auth.js";
 export * from "./tools/assert-is-never.js";
 export * from "./types/planning.js";
+export * from "./types/reference.js";
 export * from "./types/user-profile.js";
diff --git a/packages/shared/src/types/reference.ts b/packages/shared/src/types/reference.ts
new file mode 100644
index 0000000..f02cfe2
--- /dev/null
+++ b/packages/shared/src/types/reference.ts
@@ -0,0 +1,21 @@
+/**
+ * A dietary regime, as returned by `GET /reference/diets` — reference data
+ * (`Diet`, seeded via `apps/api/prisma/seed.ts`), not user-specific.
+ */
+export interface DietView {
+  id: number;
+  name: string;
+}
+
+/**
+ * A selectable allergen, as returned by `GET /reference/allergies`.
+ *
+ * `name` is resolved server-side from the parent `Category` — the `Allergy`
+ * table itself carries no name of its own (see `schema.prisma`), so this
+ * flattens that split away: callers just get `{id, name}` and never need to
+ * know a `Category` exists underneath.
+ */
+export interface AllergyView {
+  id: number;
+  name: string;
+}