diff --git a/apps/api/prisma/migrations/20260820100000_recipe_source_linking/migration.sql b/apps/api/prisma/migrations/20260820100000_recipe_source_linking/migration.sql
new file mode 100644
index 0000000..877c7a4
--- /dev/null
+++ b/apps/api/prisma/migrations/20260820100000_recipe_source_linking/migration.sql
@@ -0,0 +1,24 @@
+-- Adds `Source.key` (`key String @unique`) — the catalog of implemented
+-- recipe sources is now kept in sync with the adapter registry
+-- (recipe-source-registry.ts) by key, same "stable English camelCase uid"
+-- convention as Diet/Unit/TechStep, rather than hand-maintained. `sources`
+-- has never been seeded (no rows exist pre-launch), so a plain NOT NULL
+-- column with no backfill is safe.
+--
+-- Adds `Recipe.external_id` — the item's identifier on `source`, `null`
+-- for a manually-authored recipe. `@@unique([sourceId, externalId])`
+-- prevents importing the same source recipe twice; Postgres treats each
+-- NULL as distinct, so manually-authored recipes (both columns null) never
+-- collide with each other or with one another here.
+
+-- AlterTable
+ALTER TABLE "sources" ADD COLUMN "key" TEXT NOT NULL;
+
+-- CreateIndex
+CREATE UNIQUE INDEX "sources_key_key" ON "sources"("key");
+
+-- AlterTable
+ALTER TABLE "recipe" ADD COLUMN "external_id" TEXT;
+
+-- CreateIndex
+CREATE UNIQUE INDEX "recipe_source_id_external_id_key" ON "recipe"("source_id", "external_id");
diff --git a/apps/api/prisma/schema.prisma b/apps/api/prisma/schema.prisma
index 9eddd26..12849fa 100644
--- a/apps/api/prisma/schema.prisma
+++ b/apps/api/prisma/schema.prisma
@@ -211,8 +211,20 @@ model PlanningItem {
 // Recipes
 // -----------------------------------------------------------------------------
 
+/// Catalog of implemented recipe sources (specific websites/APIs the
+/// import pipeline knows how to talk to) — one row per adapter registered
+/// in `apps/api/src/lib/recipe-source-registry.ts`, kept in sync by
+/// `syncRecipeSources` (`apps/api/src/db/recipe-source-sync.ts`) rather
+/// than hand-maintained like `DIETS`/`UNITS` (`reference-seed-data.ts`):
+/// the adapter registry is the actual source of truth for "which sources
+/// exist", this table just mirrors it so `Recipe.sourceId` has something
+/// to point at. `key` matches `RecipeSourceAdapter.key` — same stable
+/// English camelCase uid convention as `Diet.key`/`Unit.key`/`TechStep.key`.
+/// Empty until a concrete adapter is registered (none exists yet, see
+/// recipe-source-adapter.ts).
 model Source {
   id   Int     @id @default(autoincrement())
+  key  String  @unique
   name String
   url  String?
 
@@ -239,6 +251,17 @@ model Recipe {
   id            Int              @id @default(autoincrement())
   name          String
   sourceId      Int?             @map("source_id")
+  /// The item's identifier on `source` (`RecipeSourceListItem.externalId`,
+  /// recipe-source-adapter.ts) — `null` for a manually-authored recipe,
+  /// alongside `sourceId` being `null`. Together with `sourceId`, this is
+  /// what `findImportedExternalIds` (recipe-source-sync.ts) checks against
+  /// to tell an already-imported source item apart from a new one when
+  /// browsing (see `markAlreadyImported`, recipe-source-adapter.ts) — the
+  /// `@@unique([sourceId, externalId])` below is what actually prevents
+  /// importing the same source recipe twice (Postgres treats each `NULL`
+  /// as distinct, so manually-authored recipes never collide with each
+  /// other here).
+  externalId    String?          @map("external_id")
   description   String?
   picture       String?
   /// How many portions this recipe yields as written (its ingredient
@@ -267,6 +290,7 @@ model Recipe {
   favoritedBy   RecipeFavorite[]
   diets         RecipeDiet[]
 
+  @@unique([sourceId, externalId])
   @@map("recipe")
 }
 
diff --git a/apps/api/prisma/seed.ts b/apps/api/prisma/seed.ts
index 87534e6..6bc8ea6 100644
--- a/apps/api/prisma/seed.ts
+++ b/apps/api/prisma/seed.ts
@@ -1,4 +1,5 @@
 import { PrismaClient } from "@prisma/client";
+import { syncRecipeSources } from "../src/db/recipe-source-sync.js";
 import { seedReferenceData } from "../src/db/reference-seed-data.js";
 
 // Standalone CLI entry point (not `src/db/prisma.ts` — that module pulls in
@@ -10,6 +11,7 @@ import { seedReferenceData } from "../src/db/reference-seed-data.js";
 const prisma = new PrismaClient();
 
 seedReferenceData(prisma)
+  .then(() => syncRecipeSources(prisma))
   .then(() => prisma.$disconnect())
   .catch(async (err) => {
     console.error(err);
diff --git a/apps/api/src/db/recipe-source-sync.ts b/apps/api/src/db/recipe-source-sync.ts
new file mode 100644
index 0000000..3ff0eb2
--- /dev/null
+++ b/apps/api/src/db/recipe-source-sync.ts
@@ -0,0 +1,61 @@
+import type { PrismaClient } from "@prisma/client";
+import { listRecipeSources } from "../lib/recipe-source-registry.js";
+
+/**
+ * Upserts one `Source` row (schema.prisma) per adapter currently in
+ * `recipe-source-registry.ts`, keyed by `adapter.key` — keeps the
+ * `sources` catalog an exact mirror of "which sources are actually
+ * implemented in code", rather than a hand-maintained list that can drift
+ * out of sync the way `DIETS`/`UNITS` (`reference-seed-data.ts`) would if
+ * copy-pasted here. Call once at startup (`prisma/seed.ts`) and in test
+ * setup (`test-support/reset-db.ts`), the same place `seedReferenceData`
+ * runs — kept as its own function rather than folded into that one, since
+ * it reads from the adapter registry instead of a static array.
+ *
+ * Never deletes a `Source` row whose key fell out of the registry (e.g. an
+ * adapter temporarily removed from code) — a recipe already imported from
+ * it should keep citing it rather than having `sourceId` silently nulled
+ * out from under it (see `onDelete: SetNull` on `Recipe.source` in
+ * schema.prisma, which is what *would* happen on an actual delete).
+ *
+ * Safe to call with an empty registry — currently always the case, since
+ * no concrete adapter exists yet (see recipe-source-adapter.ts) — leaves
+ * the `sources` table untouched.
+ */
+export async function syncRecipeSources(prisma: PrismaClient): Promise<void> {
+  for (const adapter of listRecipeSources()) {
+    await prisma.source.upsert({
+      where: { key: adapter.key },
+      update: { name: adapter.name },
+      create: { key: adapter.key, name: adapter.name },
+    });
+  }
+}
+
+/**
+ * Which of `externalIds` already have a `Recipe` imported from the source
+ * registered under `sourceKey` — the DB-touching counterpart to
+ * `markAlreadyImported` (recipe-source-adapter.ts), which stays pure and
+ * takes this set as a plain argument rather than querying itself. Returns
+ * an empty set (not an error) for a `sourceKey` with no matching `Source`
+ * row — nothing can have been imported from a source we don't even have a
+ * catalog entry for.
+ */
+export async function findImportedExternalIds(
+  prisma: PrismaClient,
+  sourceKey: string,
+  externalIds: string[],
+): Promise<Set<string>> {
+  if (externalIds.length === 0) return new Set();
+
+  const source = await prisma.source.findUnique({ where: { key: sourceKey } });
+  if (!source) return new Set();
+
+  const imported = await prisma.recipe.findMany({
+    where: { sourceId: source.id, externalId: { in: externalIds } },
+    select: { externalId: true },
+  });
+  return new Set(
+    imported.flatMap((recipe) => (recipe.externalId !== null ? [recipe.externalId] : [])),
+  );
+}
diff --git a/apps/api/src/lib/recipe-source-adapter.ts b/apps/api/src/lib/recipe-source-adapter.ts
new file mode 100644
index 0000000..2475ce8
--- /dev/null
+++ b/apps/api/src/lib/recipe-source-adapter.ts
@@ -0,0 +1,162 @@
+/**
+ * The generic contract every recipe source (a specific website, an API, …)
+ * implements — groundwork for the "Import d'une recette" pipeline described
+ * in specs/batch-cooking-architecture.md (import depuis source → traduction
+ * en étapes → sauvegarde). This file only defines the shapes; no concrete
+ * source exists yet (see `recipe-source-registry.ts` for where one would be
+ * registered) and nothing here talks to the database or an HTTP route —
+ * that wiring (persisting an imported recipe, resolving `sourceId`) is
+ * deliberately out of scope until a real source needs it.
+ *
+ * The flow a caller drives against one adapter:
+ *   1. `list()` — browse what's available from the source (paginated,
+ *      optionally filtered by `query`), like flipping through a catalog.
+ *   2. {@link markAlreadyImported} — flag which of those items we've
+ *      already imported, so browsing a source doesn't dangle recipes the
+ *      user has already brought in as if they were new. A separate, pure
+ *      step rather than something `list()` itself does: an adapter only
+ *      knows its source, never our database — same reasoning as
+ *      `tech-step-matcher.ts`'s split between pure `matchTechStep` and its
+ *      DB-touching `loadTechStepMappingRules`. Whichever future layer
+ *      queries "which externalIds from this source do we already have"
+ *      (not yet decided — it needs a place to persist that link,
+ *      see {@link RecipeSourceListItem.externalId}) calls this to annotate
+ *      the page before returning it.
+ *   3. `fetchDetail(externalId)` — once the user picks one item from that
+ *      list, fetch its full raw content.
+ *   4. `parse(raw)` — turn that raw content into a {@link ParsedRecipe},
+ *      pure and synchronous so it's unit-testable without any network
+ *      access (same split as step 2 above).
+ */
+
+/** Search/pagination input for {@link RecipeSourceAdapter.list}. */
+export interface RecipeSourceListParams {
+  /** Free-text search, if the source supports it. Omitted means "browse everything". */
+  query?: string;
+  /**
+   * Opaque continuation token from a previous {@link RecipeSourceListResult.nextCursor}
+   * — omitted (or `null`) means "start from the first page". Deliberately
+   * opaque (not a page number) so an adapter can back it with whatever its
+   * source actually supports (page number, offset, an API-provided token).
+   */
+  cursor?: string | null;
+}
+
+/** One entry in a {@link RecipeSourceAdapter.list} result — enough to show in a browsing UI and to fetch the full recipe once selected. */
+export interface RecipeSourceListItem {
+  /**
+   * Source-specific identifier, opaque to callers — passed back verbatim
+   * to {@link RecipeSourceAdapter.fetchDetail}, and the key
+   * {@link markAlreadyImported} matches against to tell an already-imported
+   * item apart from a new one.
+   */
+  externalId: string;
+  title: string;
+  picture: string | null;
+  /** Canonical URL of the recipe on the source, kept for attribution even before it's imported. */
+  url: string;
+}
+
+export interface RecipeSourceListResult {
+  items: RecipeSourceListItem[];
+  /** Pass back as `cursor` to fetch the next page — `null` means this was the last page. */
+  nextCursor: string | null;
+}
+
+/** A browsed {@link RecipeSourceListItem}, after {@link markAlreadyImported} has flagged whether we already imported it. What a browsing UI actually renders — e.g. to grey it out or offer "already added" instead of "import". */
+export interface BrowsableRecipeItem extends RecipeSourceListItem {
+  alreadyImported: boolean;
+}
+
+/**
+ * Splits a page of {@link RecipeSourceListItem}s into already-imported vs.
+ * new, purely by checking each item's `externalId` against
+ * `importedExternalIds` — no I/O here, the caller is responsible for
+ * gathering that set (from wherever we end up persisting the link between
+ * an imported `Recipe` and the source item it came from) before calling
+ * this. Kept as a tiny, dedicated, easily-testable step rather than folded
+ * into `list()` itself, so an adapter never needs to know our database
+ * exists.
+ */
+export function markAlreadyImported(
+  items: RecipeSourceListItem[],
+  importedExternalIds: ReadonlySet<string>,
+): BrowsableRecipeItem[] {
+  return items.map((item) => ({
+    ...item,
+    alreadyImported: importedExternalIds.has(item.externalId),
+  }));
+}
+
+/**
+ * One ingredient line as lifted from a source, before it's resolved against
+ * our own `Ingredient`/`Unit` reference catalogs (that resolution —
+ * matching free text to a `key`, the way `tech-step-matcher.ts` matches
+ * step text to a `TechStep` — is a separate, not-yet-built concern; this
+ * type only carries what a source's raw text actually says). `rawText` is
+ * kept alongside the (best-effort) parsed fields so a failed/partial parse
+ * is still traceable back to what the source originally wrote.
+ */
+export interface ParsedRecipeIngredient {
+  rawText: string;
+  quantity: number | null;
+  /** Free-text unit exactly as written by the source (e.g. `"cuillère à soupe"`, `"g"`) — not yet resolved to a `Unit.key`. */
+  unit: string | null;
+  /** Free-text ingredient name exactly as written by the source — not yet resolved to an `Ingredient.key`. */
+  name: string;
+}
+
+export interface ParsedRecipeStep {
+  description: string;
+  picture: string | null;
+}
+
+/**
+ * The normalized shape every adapter's {@link RecipeSourceAdapter.parse}
+ * produces, regardless of the source. Intentionally *not*
+ * `CreateRecipeInput` (packages/shared/src/schemas/recipe.ts): ingredients
+ * are still free text (no `ingredientId`/`unitId` — that catalog-matching
+ * step doesn't exist yet), and there's no `dietIds`/`visibility` since a
+ * source can't know those. Turning a `ParsedRecipe` into a saved `Recipe`
+ * is future work for whichever module ends up driving this pipeline.
+ */
+export interface ParsedRecipe {
+  name: string;
+  description: string | null;
+  picture: string | null;
+  /** `null` when the source doesn't state a serving size. */
+  portions: number | null;
+  /** Canonical URL of the recipe on the source — the eventual `Source`/`Recipe.sourceId` link (schema.prisma) is populated from this once the import pipeline saves the recipe. */
+  sourceUrl: string;
+  ingredients: ParsedRecipeIngredient[];
+  steps: ParsedRecipeStep[];
+}
+
+/**
+ * A single recipe source — a specific website or API, plus the two pieces
+ * of source-specific logic needed to pull a recipe out of it. `TRawDetail`
+ * is whatever shape `fetchDetail` naturally returns for this source (an
+ * HTML string, a parsed JSON body, …); `parse` is the only thing that needs
+ * to understand it.
+ *
+ * @example
+ * ```ts
+ * const myAdapter: RecipeSourceAdapter<{ html: string }> = {
+ *   key: "someRecipeSite",
+ *   name: "Some Recipe Site",
+ *   async list(params) { ... },
+ *   async fetchDetail(externalId) { ... },
+ *   parse(raw) { ... },
+ * };
+ * registerRecipeSource(myAdapter);
+ * ```
+ */
+export interface RecipeSourceAdapter<TRawDetail = unknown> {
+  /** Stable identifier used to look this adapter up in the registry — same "English camelCase uid" convention as `Diet.key`/`Unit.key`/`TechStep.key`. */
+  key: string;
+  /** Human-readable name, for display in a source picker. */
+  name: string;
+  list(params: RecipeSourceListParams): Promise<RecipeSourceListResult>;
+  fetchDetail(externalId: string): Promise<TRawDetail>;
+  parse(raw: TRawDetail): ParsedRecipe;
+}
diff --git a/apps/api/src/lib/recipe-source-errors.ts b/apps/api/src/lib/recipe-source-errors.ts
new file mode 100644
index 0000000..256c898
--- /dev/null
+++ b/apps/api/src/lib/recipe-source-errors.ts
@@ -0,0 +1,37 @@
+/**
+ * Error vocabulary a {@link RecipeSourceAdapter} (recipe-source-adapter.ts)
+ * implementation throws when talking to its source fails — kept separate
+ * from `@batch-cooking/error-tools`'s `HttpError`/`ErrorCode` (used for
+ * *this API's* HTTP responses) since no route drives this module yet. A
+ * future import route would catch these and translate them into an
+ * `HttpError` with a dedicated `ErrorCode` the same way any other service
+ * error is; this module only needs a consistent shape to throw in the
+ * meantime, not that translation.
+ */
+
+/** Base class for every error a {@link RecipeSourceAdapter} can throw — lets a caller `catch (err) { if (err instanceof RecipeSourceError) ... }` regardless of which stage failed. */
+export class RecipeSourceError extends Error {
+  /** The failing adapter's `key` (recipe-source-adapter.ts's `RecipeSourceAdapter.key`) — which source this error came from. */
+  readonly sourceKey: string;
+
+  constructor(sourceKey: string, message: string, options?: { cause?: unknown }) {
+    super(message, options);
+    this.sourceKey = sourceKey;
+  }
+}
+
+/** The source's `list`/`fetchDetail` failed — network error, non-2xx response, source unreachable, etc. */
+export class RecipeSourceFetchError extends RecipeSourceError {
+  constructor(sourceKey: string, message: string, options?: { cause?: unknown }) {
+    super(sourceKey, message, options);
+    this.name = "RecipeSourceFetchError";
+  }
+}
+
+/** The source responded, but `parse` couldn't make sense of the raw payload (unexpected shape, missing required field, …). */
+export class RecipeSourceParseError extends RecipeSourceError {
+  constructor(sourceKey: string, message: string, options?: { cause?: unknown }) {
+    super(sourceKey, message, options);
+    this.name = "RecipeSourceParseError";
+  }
+}
diff --git a/apps/api/src/lib/recipe-source-registry.ts b/apps/api/src/lib/recipe-source-registry.ts
new file mode 100644
index 0000000..f12e682
--- /dev/null
+++ b/apps/api/src/lib/recipe-source-registry.ts
@@ -0,0 +1,56 @@
+import type { RecipeSourceAdapter } from "./recipe-source-adapter.js";
+
+/**
+ * In-memory registry of every {@link RecipeSourceAdapter} (recipe-source-adapter.ts)
+ * this process knows about, keyed by `adapter.key`. Deliberately not
+ * DB-backed — an adapter *is* code (a website's fetch/parse logic can't
+ * live in a database row) — but the `Source` table (schema.prisma) is kept
+ * in sync with it (see `syncRecipeSources`, recipe-source-sync.ts) so a
+ * saved `Recipe.sourceId` has a row to point at. Actually saving an
+ * imported recipe (setting `Recipe.sourceId`/`externalId`) is still future
+ * work for whichever module ends up driving the import pipeline — this
+ * registry only answers "which sources can we import from right now".
+ *
+ * No adapter is registered here yet — this file only provides the
+ * mechanism; `registerRecipeSource` is meant to be called once per adapter
+ * module, at whatever point a concrete source is added.
+ */
+const adapters = new Map<string, RecipeSourceAdapter>();
+
+/**
+ * Registers `adapter` under its own `key`. Throws if that key is already
+ * taken — two adapters silently overwriting each other would be a bug (a
+ * caller reaching for "marmiton" should never get a different adapter than
+ * the one it registered), not a case to swallow.
+ */
+export function registerRecipeSource<TRawDetail>(adapter: RecipeSourceAdapter<TRawDetail>): void {
+  if (adapters.has(adapter.key)) {
+    throw new Error(`Recipe source "${adapter.key}" is already registered`);
+  }
+  // `TRawDetail` only matters within one adapter's own list/fetchDetail/parse
+  // trio — once stored, callers look adapters up by key and drive the same
+  // three methods generically, so the registry itself doesn't need to know
+  // each adapter's raw type. This cast is the standard way to store a
+  // heterogeneous collection of otherwise-identically-shaped generics.
+  adapters.set(adapter.key, adapter as RecipeSourceAdapter);
+}
+
+/** The adapter registered under `key`, or `undefined` if none is. */
+export function getRecipeSource(key: string): RecipeSourceAdapter | undefined {
+  return adapters.get(key);
+}
+
+/** Every registered adapter — e.g. to offer a source picker. */
+export function listRecipeSources(): RecipeSourceAdapter[] {
+  return [...adapters.values()];
+}
+
+/**
+ * Empties the registry. Not meant for application code — `apps/api/src`
+ * never calls this — only for test isolation, the same role
+ * `test-support/reset-db.ts` plays for the database: without it, adapters
+ * registered by one test file would leak into the next.
+ */
+export function clearRecipeSources(): void {
+  adapters.clear();
+}
diff --git a/apps/api/test-support/reset-db.ts b/apps/api/test-support/reset-db.ts
index 3efcc0a..81f235a 100644
--- a/apps/api/test-support/reset-db.ts
+++ b/apps/api/test-support/reset-db.ts
@@ -1,4 +1,5 @@
 import { prisma } from "../src/db/prisma.js";
+import { syncRecipeSources } from "../src/db/recipe-source-sync.js";
 import { seedReferenceData } from "../src/db/reference-seed-data.js";
 
 // Single TRUNCATE ... CASCADE covers FK ordering and resets identity
@@ -7,6 +8,9 @@ import { seedReferenceData } from "../src/db/reference-seed-data.js";
 // 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/unitId need real rows to reference.
+// `syncRecipeSources` runs last, for the same reason: `sources` should
+// reflect whatever adapters this test run happens to have registered
+// (usually none — see recipe-source-registry.ts).
 export async function resetDatabase() {
   await prisma.$executeRawUnsafe(`
     TRUNCATE TABLE
@@ -18,4 +22,5 @@ export async function resetDatabase() {
     RESTART IDENTITY CASCADE;
   `);
   await seedReferenceData(prisma);
+  await syncRecipeSources(prisma);
 }
diff --git a/apps/api/test/recipe-source-sync.test.ts b/apps/api/test/recipe-source-sync.test.ts
new file mode 100644
index 0000000..0eefee3
--- /dev/null
+++ b/apps/api/test/recipe-source-sync.test.ts
@@ -0,0 +1,204 @@
+import type { SignupInput } from "@batch-cooking/shared";
+import { faker } from "@faker-js/faker";
+import { expect } from "chai";
+import request from "supertest";
+import { createApp } from "../src/app.js";
+import { prisma } from "../src/db/prisma.js";
+import { findImportedExternalIds, syncRecipeSources } from "../src/db/recipe-source-sync.js";
+import type { RecipeSourceAdapter } from "../src/lib/recipe-source-adapter.js";
+import { clearRecipeSources, registerRecipeSource } from "../src/lib/recipe-source-registry.js";
+import { resetDatabase } from "../test-support/reset-db.js";
+
+/** See `recipe.test.ts` — generated rather than hardcoded, no test fixture looks like a real person's data. */
+function buildSignupPayload(): SignupInput {
+  const firstName = faker.person.firstName();
+  const lastName = faker.person.lastName();
+  return {
+    firstName,
+    lastName,
+    email: faker.internet.email({ firstName, lastName }).toLowerCase(),
+    password: faker.internet.password({ length: 16 }),
+  };
+}
+
+/** A minimal `RecipeSourceAdapter` whose list/fetchDetail/parse are never actually called here — only `key`/`name` matter for exercising `syncRecipeSources`. */
+function buildFakeAdapter(key: string, name: string): RecipeSourceAdapter {
+  return {
+    key,
+    name,
+    async list() {
+      return { items: [], nextCursor: null };
+    },
+    async fetchDetail() {
+      throw new Error("not implemented");
+    },
+    parse() {
+      throw new Error("not implemented");
+    },
+  };
+}
+
+describe("recipe-source-sync", () => {
+  const app = createApp();
+
+  async function signup(): Promise<{ profileId: number }> {
+    const res = await request.agent(app).post("/auth/signup").send(buildSignupPayload());
+    return { profileId: res.body.id };
+  }
+
+  beforeEach(async () => {
+    await resetDatabase();
+    clearRecipeSources();
+  });
+
+  afterEach(() => {
+    clearRecipeSources();
+  });
+
+  after(async () => {
+    await prisma.$disconnect();
+  });
+
+  describe("syncRecipeSources", () => {
+    it("does nothing when the registry is empty", async () => {
+      await syncRecipeSources(prisma);
+      expect(await prisma.source.count()).to.equal(0);
+    });
+
+    it("creates a Source row per registered adapter", async () => {
+      registerRecipeSource(buildFakeAdapter("fakeSource", "Fake Source"));
+
+      await syncRecipeSources(prisma);
+
+      const source = await prisma.source.findUniqueOrThrow({ where: { key: "fakeSource" } });
+      expect(source.name).to.equal("Fake Source");
+    });
+
+    it("is idempotent — running it twice doesn't duplicate rows", async () => {
+      registerRecipeSource(buildFakeAdapter("fakeSource", "Fake Source"));
+
+      await syncRecipeSources(prisma);
+      await syncRecipeSources(prisma);
+
+      expect(await prisma.source.count()).to.equal(1);
+    });
+
+    it("updates the name when the adapter's own name changes between syncs", async () => {
+      registerRecipeSource(buildFakeAdapter("fakeSource", "Old Name"));
+      await syncRecipeSources(prisma);
+      clearRecipeSources();
+      registerRecipeSource(buildFakeAdapter("fakeSource", "New Name"));
+
+      await syncRecipeSources(prisma);
+
+      const source = await prisma.source.findUniqueOrThrow({ where: { key: "fakeSource" } });
+      expect(source.name).to.equal("New Name");
+    });
+
+    it("never deletes a Source row whose key fell out of the registry", async () => {
+      registerRecipeSource(buildFakeAdapter("fakeSource", "Fake Source"));
+      await syncRecipeSources(prisma);
+      clearRecipeSources();
+
+      await syncRecipeSources(prisma);
+
+      expect(await prisma.source.count()).to.equal(1);
+    });
+  });
+
+  describe("findImportedExternalIds", () => {
+    it("returns an empty set for a sourceKey with no matching Source row", async () => {
+      expect(await findImportedExternalIds(prisma, "unknown", ["1", "2"])).to.deep.equal(new Set());
+    });
+
+    it("returns an empty set for an empty externalIds list", async () => {
+      expect(await findImportedExternalIds(prisma, "fakeSource", [])).to.deep.equal(new Set());
+    });
+
+    it("returns exactly the externalIds already imported from that source", async () => {
+      const { profileId } = await signup();
+      registerRecipeSource(buildFakeAdapter("fakeSource", "Fake Source"));
+      await syncRecipeSources(prisma);
+      const source = await prisma.source.findUniqueOrThrow({ where: { key: "fakeSource" } });
+
+      await prisma.recipe.create({
+        data: {
+          name: "Tarte",
+          authorId: profileId,
+          portions: 4,
+          sourceId: source.id,
+          externalId: "1",
+        },
+      });
+      // Manually-authored, not tied to any source — shouldn't ever show up as "imported".
+      await prisma.recipe.create({ data: { name: "Salade", authorId: profileId, portions: 2 } });
+
+      const result = await findImportedExternalIds(prisma, "fakeSource", ["1", "2", "3"]);
+      expect(result).to.deep.equal(new Set(["1"]));
+    });
+
+    it("scopes matches to the given source — the same externalId from a different source doesn't count", async () => {
+      const { profileId } = await signup();
+      registerRecipeSource(buildFakeAdapter("fakeSource", "Fake Source"));
+      registerRecipeSource(buildFakeAdapter("otherSource", "Other Source"));
+      await syncRecipeSources(prisma);
+      const otherSource = await prisma.source.findUniqueOrThrow({ where: { key: "otherSource" } });
+
+      await prisma.recipe.create({
+        data: {
+          name: "Tarte",
+          authorId: profileId,
+          portions: 4,
+          sourceId: otherSource.id,
+          externalId: "1",
+        },
+      });
+
+      expect(await findImportedExternalIds(prisma, "fakeSource", ["1"])).to.deep.equal(new Set());
+    });
+  });
+
+  describe("Recipe(sourceId, externalId) uniqueness", () => {
+    it("rejects importing the same source recipe twice", async () => {
+      const { profileId } = await signup();
+      registerRecipeSource(buildFakeAdapter("fakeSource", "Fake Source"));
+      await syncRecipeSources(prisma);
+      const source = await prisma.source.findUniqueOrThrow({ where: { key: "fakeSource" } });
+
+      await prisma.recipe.create({
+        data: {
+          name: "Tarte",
+          authorId: profileId,
+          portions: 4,
+          sourceId: source.id,
+          externalId: "1",
+        },
+      });
+
+      let rejected = false;
+      try {
+        await prisma.recipe.create({
+          data: {
+            name: "Tarte (again)",
+            authorId: profileId,
+            portions: 4,
+            sourceId: source.id,
+            externalId: "1",
+          },
+        });
+      } catch {
+        rejected = true;
+      }
+      expect(rejected).to.be.true;
+    });
+
+    it("allows any number of manually-authored recipes (both columns null)", async () => {
+      const { profileId } = await signup();
+
+      await prisma.recipe.create({ data: { name: "Une", authorId: profileId, portions: 4 } });
+      await prisma.recipe.create({ data: { name: "Deux", authorId: profileId, portions: 4 } });
+
+      expect(await prisma.recipe.count()).to.equal(2);
+    });
+  });
+});
diff --git a/apps/api/test/recipe-source.test.ts b/apps/api/test/recipe-source.test.ts
new file mode 100644
index 0000000..ff04e86
--- /dev/null
+++ b/apps/api/test/recipe-source.test.ts
@@ -0,0 +1,270 @@
+import { expect } from "chai";
+import type {
+  ParsedRecipe,
+  RecipeSourceAdapter,
+  RecipeSourceListItem,
+  RecipeSourceListParams,
+  RecipeSourceListResult,
+} from "../src/lib/recipe-source-adapter.js";
+import { markAlreadyImported } from "../src/lib/recipe-source-adapter.js";
+import {
+  RecipeSourceError,
+  RecipeSourceFetchError,
+  RecipeSourceParseError,
+} from "../src/lib/recipe-source-errors.js";
+import {
+  clearRecipeSources,
+  getRecipeSource,
+  listRecipeSources,
+  registerRecipeSource,
+} from "../src/lib/recipe-source-registry.js";
+
+interface FakeRawRecipe {
+  externalId: string;
+  title: string;
+  servings: number;
+  ingredientLines: string[];
+  instructionLines: string[];
+}
+
+const FAKE_CATALOG: FakeRawRecipe[] = [
+  {
+    externalId: "1",
+    title: "Tarte aux pommes",
+    servings: 6,
+    ingredientLines: ["3 pommes", "200 g de farine"],
+    instructionLines: ["Éplucher les pommes", "Cuire 30 minutes"],
+  },
+  {
+    externalId: "2",
+    title: "Soupe de légumes",
+    servings: 4,
+    ingredientLines: ["2 carottes"],
+    instructionLines: ["Mijoter 20 minutes"],
+  },
+  {
+    externalId: "3",
+    title: "Salade César",
+    servings: 2,
+    ingredientLines: ["1 salade"],
+    instructionLines: ["Mélanger"],
+  },
+];
+
+const PAGE_SIZE = 2;
+
+/** A minimal in-memory `RecipeSourceAdapter`, standing in for a real website/API — proves the interface (recipe-source-adapter.ts) is actually implementable end to end. */
+function buildFakeAdapter(key = "fakeSource"): RecipeSourceAdapter<FakeRawRecipe> {
+  return {
+    key,
+    name: "Fake Source",
+    async list(params: RecipeSourceListParams): Promise<RecipeSourceListResult> {
+      const start = params.cursor ? Number(params.cursor) : 0;
+      const page = FAKE_CATALOG.slice(start, start + PAGE_SIZE);
+      const nextStart = start + PAGE_SIZE;
+      return {
+        items: page.map((recipe) => ({
+          externalId: recipe.externalId,
+          title: recipe.title,
+          picture: null,
+          url: `https://fake.test/recipes/${recipe.externalId}`,
+        })),
+        nextCursor: nextStart < FAKE_CATALOG.length ? String(nextStart) : null,
+      };
+    },
+    async fetchDetail(externalId: string): Promise<FakeRawRecipe> {
+      const found = FAKE_CATALOG.find((recipe) => recipe.externalId === externalId);
+      if (!found) throw new RecipeSourceFetchError(key, `Unknown recipe ${externalId}`);
+      return found;
+    },
+    parse(raw: FakeRawRecipe): ParsedRecipe {
+      return {
+        name: raw.title,
+        description: null,
+        picture: null,
+        portions: raw.servings,
+        sourceUrl: `https://fake.test/recipes/${raw.externalId}`,
+        ingredients: raw.ingredientLines.map((line) => ({
+          rawText: line,
+          quantity: null,
+          unit: null,
+          name: line,
+        })),
+        steps: raw.instructionLines.map((line) => ({ description: line, picture: null })),
+      };
+    },
+  };
+}
+
+describe("recipe-source", () => {
+  afterEach(() => {
+    clearRecipeSources();
+  });
+
+  describe("registry", () => {
+    it("registers and retrieves an adapter by key", () => {
+      const adapter = buildFakeAdapter();
+      registerRecipeSource(adapter);
+      expect(getRecipeSource("fakeSource")).to.equal(adapter);
+    });
+
+    it("returns undefined for an unregistered key", () => {
+      expect(getRecipeSource("unknown")).to.be.undefined;
+    });
+
+    it("lists every registered adapter", () => {
+      registerRecipeSource(buildFakeAdapter("fakeSource"));
+      registerRecipeSource(buildFakeAdapter("otherSource"));
+
+      expect(
+        listRecipeSources()
+          .map((adapter) => adapter.key)
+          .sort(),
+      ).to.deep.equal(["fakeSource", "otherSource"]);
+    });
+
+    it("rejects registering the same key twice", () => {
+      registerRecipeSource(buildFakeAdapter());
+      expect(() => registerRecipeSource(buildFakeAdapter())).to.throw(/already registered/);
+    });
+
+    it("clearRecipeSources empties the registry", () => {
+      registerRecipeSource(buildFakeAdapter());
+      clearRecipeSources();
+      expect(listRecipeSources()).to.deep.equal([]);
+    });
+  });
+
+  describe("adapter contract (via a fake adapter)", () => {
+    it("browses in pages until nextCursor is null", async () => {
+      const adapter = buildFakeAdapter();
+
+      const firstPage = await adapter.list({});
+      expect(firstPage.items.map((item) => item.externalId)).to.deep.equal(["1", "2"]);
+      expect(firstPage.nextCursor).to.equal("2");
+
+      const secondPage = await adapter.list({ cursor: firstPage.nextCursor });
+      expect(secondPage.items.map((item) => item.externalId)).to.deep.equal(["3"]);
+      expect(secondPage.nextCursor).to.be.null;
+    });
+
+    it("filters by query the same way, when the source supports it (fake adapter ignores it — only pagination is exercised here)", async () => {
+      const adapter = buildFakeAdapter();
+      const res = await adapter.list({ query: "tarte" });
+      // Documents that `query` is a valid, optional param even though this
+      // particular fake doesn't act on it — a real adapter would filter.
+      expect(res.items).to.have.length(2);
+    });
+
+    it("fetches the detail for a selected item, then parses it into a ParsedRecipe", async () => {
+      const adapter = buildFakeAdapter();
+
+      const raw = await adapter.fetchDetail("1");
+      const parsed = adapter.parse(raw);
+
+      expect(parsed.name).to.equal("Tarte aux pommes");
+      expect(parsed.description).to.be.null;
+      expect(parsed.portions).to.equal(6);
+      expect(parsed.sourceUrl).to.equal("https://fake.test/recipes/1");
+      expect(parsed.ingredients).to.have.length(2);
+      expect(parsed.ingredients[0]).to.deep.equal({
+        rawText: "3 pommes",
+        quantity: null,
+        unit: null,
+        name: "3 pommes",
+      });
+      expect(parsed.steps).to.deep.equal([
+        { description: "Éplucher les pommes", picture: null },
+        { description: "Cuire 30 minutes", picture: null },
+      ]);
+    });
+
+    it("throws RecipeSourceFetchError for an unknown externalId", async () => {
+      const adapter = buildFakeAdapter();
+
+      try {
+        await adapter.fetchDetail("does-not-exist");
+        expect.fail("expected fetchDetail to throw");
+      } catch (err) {
+        expect(err).to.be.instanceOf(RecipeSourceFetchError);
+        expect((err as RecipeSourceFetchError).sourceKey).to.equal("fakeSource");
+      }
+    });
+  });
+
+  describe("markAlreadyImported", () => {
+    const items: RecipeSourceListItem[] = [
+      {
+        externalId: "1",
+        title: "Tarte aux pommes",
+        picture: null,
+        url: "https://fake.test/recipes/1",
+      },
+      {
+        externalId: "2",
+        title: "Soupe de légumes",
+        picture: null,
+        url: "https://fake.test/recipes/2",
+      },
+      { externalId: "3", title: "Salade César", picture: null, url: "https://fake.test/recipes/3" },
+    ];
+
+    it("flags items whose externalId is in the imported set, leaves the rest false", () => {
+      const result = markAlreadyImported(items, new Set(["1", "3"]));
+
+      expect(
+        result.map((item) => ({
+          externalId: item.externalId,
+          alreadyImported: item.alreadyImported,
+        })),
+      ).to.deep.equal([
+        { externalId: "1", alreadyImported: true },
+        { externalId: "2", alreadyImported: false },
+        { externalId: "3", alreadyImported: true },
+      ]);
+    });
+
+    it("flags nothing when the imported set is empty", () => {
+      const result = markAlreadyImported(items, new Set());
+      expect(result.every((item) => item.alreadyImported === false)).to.be.true;
+    });
+
+    it("returns an empty list unchanged", () => {
+      expect(markAlreadyImported([], new Set(["1"]))).to.deep.equal([]);
+    });
+
+    it("preserves every field from the original item alongside the new flag", () => {
+      const [first] = markAlreadyImported([items[0]], new Set(["1"]));
+      expect(first).to.deep.equal({ ...items[0], alreadyImported: true });
+    });
+
+    it("doesn't mutate the input items", () => {
+      const snapshot = structuredClone(items);
+      markAlreadyImported(items, new Set(["1"]));
+      expect(items).to.deep.equal(snapshot);
+    });
+  });
+
+  describe("RecipeSourceError hierarchy", () => {
+    it("RecipeSourceFetchError carries the source key, a message and an optional cause, and is a RecipeSourceError", () => {
+      const cause = new Error("network down");
+      const err = new RecipeSourceFetchError("fakeSource", "could not reach source", { cause });
+
+      expect(err).to.be.instanceOf(Error);
+      expect(err).to.be.instanceOf(RecipeSourceError);
+      expect(err.name).to.equal("RecipeSourceFetchError");
+      expect(err.sourceKey).to.equal("fakeSource");
+      expect(err.message).to.equal("could not reach source");
+      expect(err.cause).to.equal(cause);
+    });
+
+    it("RecipeSourceParseError carries the source key and works without a cause", () => {
+      const err = new RecipeSourceParseError("fakeSource", "unexpected shape");
+
+      expect(err).to.be.instanceOf(RecipeSourceError);
+      expect(err.name).to.equal("RecipeSourceParseError");
+      expect(err.sourceKey).to.equal("fakeSource");
+      expect(err.cause).to.be.undefined;
+    });
+  });
+});