diff --git a/migrations/202605111155.ts b/migrations/202605111155.ts
new file mode 100644
index 0000000..9d7446b
--- /dev/null
+++ b/migrations/202605111155.ts
@@ -0,0 +1,97 @@
+import { Pool } from "mariadb/*";
+import { MigrationParams } from "umzug";
+
+/**
+ * Migration pour permettre plusieurs catégories par stack via une table de liaison.
+ * - Crée la table stack_category.
+ * - Migre les valeurs existantes de stack.category_id vers stack_category.
+ * - Ajoute un index pour les recherches par catégorie.
+ */
+export async function up({ context: pool }: MigrationParams<Pool>) {
+  const conn = await pool.getConnection();
+  try {
+    await conn.query(`
+      CREATE TABLE IF NOT EXISTS stack_category (
+        stack_id VARCHAR(255) NOT NULL,
+        category_id VARCHAR(255) NOT NULL,
+        PRIMARY KEY (stack_id, category_id),
+        FOREIGN KEY (stack_id) REFERENCES stack(id) ON DELETE CASCADE,
+        FOREIGN KEY (category_id) REFERENCES category(id) ON DELETE CASCADE
+      );
+    `);
+
+    await conn.query(`
+      INSERT IGNORE INTO stack_category (stack_id, category_id)
+      SELECT id, category_id
+      FROM stack
+      WHERE category_id IS NOT NULL;
+    `);
+
+    await conn.query(
+      `CREATE INDEX IF NOT EXISTS idx_stack_category_category_id ON stack_category(category_id)`,
+    );
+
+    const fkRows = await conn.query(
+      `SELECT CONSTRAINT_NAME
+       FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE
+       WHERE TABLE_SCHEMA = DATABASE()
+         AND TABLE_NAME = 'stack'
+         AND COLUMN_NAME = 'category_id'
+         AND REFERENCED_TABLE_NAME = 'category'`,
+    );
+    for (const row of fkRows as { CONSTRAINT_NAME: string }[]) {
+      await conn.query(
+        `ALTER TABLE stack DROP FOREIGN KEY \`${row.CONSTRAINT_NAME}\``,
+      );
+    }
+
+    await conn.query(
+      `ALTER TABLE IF EXISTS stack DROP COLUMN IF EXISTS category_id;`,
+    );
+
+    // Nettoyage défensif : si un index explicite subsiste, on le supprime.
+    await conn.query(`DROP INDEX IF EXISTS idx_stack_category_id ON stack`);
+  } finally {
+    conn.release();
+  }
+}
+
+export async function down({ context: pool }: MigrationParams<Pool>) {
+  const conn = await pool.getConnection();
+  try {
+    await conn.query(
+      `ALTER TABLE IF EXISTS stack ADD COLUMN IF NOT EXISTS category_id VARCHAR(255) NULL;`,
+    );
+
+    await conn.query(`
+      UPDATE stack s
+      LEFT JOIN (
+        SELECT stack_id, MIN(category_id) AS category_id
+        FROM stack_category
+        GROUP BY stack_id
+      ) sc ON sc.stack_id = s.id
+      SET s.category_id = sc.category_id;
+    `);
+
+    await conn.query(
+      `CREATE INDEX IF NOT EXISTS idx_stack_category_id ON stack(category_id)`,
+    );
+
+    await conn
+      .query(
+        `
+      ALTER TABLE IF EXISTS stack
+      ADD CONSTRAINT fk_stack_category_id
+      FOREIGN KEY (category_id) REFERENCES category(id) ON DELETE SET NULL;
+    `,
+      )
+      .catch(() => undefined);
+
+    await conn.query(
+      `DROP INDEX IF EXISTS idx_stack_category_category_id ON stack_category`,
+    );
+    await conn.query("DROP TABLE IF EXISTS stack_category");
+  } finally {
+    conn.release();
+  }
+}
diff --git a/src/graphql/resolvers/stackResolver.ts b/src/graphql/resolvers/stackResolver.ts
index 4b10fb1..0077bfe 100644
--- a/src/graphql/resolvers/stackResolver.ts
+++ b/src/graphql/resolvers/stackResolver.ts
@@ -22,8 +22,11 @@ function sanitizeStackInput(input: Partial<Omit<Stack, "id">>) {
   if (input.description) input.description = sanitizeString(input.description);
   if (input.versions) input.versions = input.versions.map((v) => sanitizeString(v));
   if (input.skills) input.skills = input.skills.map((s) => sanitizeString(s));
-  if (input.category && !validator.isUUID(input.category as string))
-    delete input.category;
+  if (input.categories) {
+    input.categories = input.categories.filter((category) =>
+      validator.isUUID(category as string),
+    );
+  }
 }
 
 // Résolveur GraphQL pour les opérations liées aux stacks
diff --git a/src/graphql/schemas/stackSchema.ts b/src/graphql/schemas/stackSchema.ts
index 0ec5573..43a1869 100644
--- a/src/graphql/schemas/stackSchema.ts
+++ b/src/graphql/schemas/stackSchema.ts
@@ -7,7 +7,7 @@ export const stackTypes = `
     description: String
     versions: [String!]
     skills: [String!]
-    category: ID
+    categories: [ID!]
   }
 `;
 export const stackInputs = `
@@ -17,7 +17,7 @@ export const stackInputs = `
     description: String
     versions: [String!]
     skills: [String!]
-    category: ID
+    categories: [ID!]
   }
 `;
 
diff --git a/src/repositories/StackRepository.ts b/src/repositories/StackRepository.ts
index d1af946..1fee9a6 100644
--- a/src/repositories/StackRepository.ts
+++ b/src/repositories/StackRepository.ts
@@ -20,10 +20,11 @@ export default class StackRepository extends BaseRepository {
   async getAll(): Promise<Stack[]> {
     return withConnection(this.pool, async (conn) => {
       const rows = await conn.query(`
-        SELECT s.*, v.version, ss.skill
+        SELECT s.*, v.version, ss.skill, sc.category_id
         FROM stack s
         LEFT JOIN stack_version v ON v.stack_id = s.id
         LEFT JOIN stack_skill ss ON ss.stack_id = s.id
+        LEFT JOIN stack_category sc ON sc.stack_id = s.id
         ORDER BY s.label
       `);
       const stackMap = new Map();
@@ -36,16 +37,18 @@ export default class StackRepository extends BaseRepository {
             description: row.description,
             versions: [],
             skills: [],
-            category: row.category_id,
+            categories: [],
           });
         }
         if (row.version) stackMap.get(row.id).versions.push(row.version);
         if (row.skill) stackMap.get(row.id).skills.push(row.skill);
+        if (row.category_id) stackMap.get(row.id).categories.push(row.category_id);
       }
       // Dédupliquer les versions et skills
       for (const stack of stackMap.values()) {
         stack.versions = Array.from(new Set(stack.versions));
         stack.skills = Array.from(new Set(stack.skills));
+        stack.categories = Array.from(new Set(stack.categories));
       }
       return Array.from(stackMap.values());
     });
@@ -62,14 +65,8 @@ export default class StackRepository extends BaseRepository {
     const id = this.generateId();
     await withTransaction(this.pool, async (conn) => {
       await conn.query(
-        `INSERT INTO stack (id, label, icon_id, description, category_id) VALUES (?, ?, ?, ?, ?);`,
-        [
-          id,
-          stack.label,
-          stack.icon,
-          stack.description || null,
-          stack.category || null,
-        ],
+        `INSERT INTO stack (id, label, icon_id, description) VALUES (?, ?, ?, ?);`,
+        [id, stack.label, stack.icon, stack.description || null],
       );
       if (stack.versions && stack.versions.length > 0) {
         await conn.query(
@@ -83,6 +80,12 @@ export default class StackRepository extends BaseRepository {
           stack.skills.flatMap((skill) => [id, skill]),
         );
       }
+      if (stack.categories && stack.categories.length > 0) {
+        await conn.query(
+          `INSERT INTO stack_category (stack_id, category_id) VALUES ${stack.categories.map(() => "(?, ?)").join(", ")};`,
+          stack.categories.flatMap((category) => [id, category]),
+        );
+      }
     });
     return true;
   }
@@ -103,8 +106,6 @@ export default class StackRepository extends BaseRepository {
         label: stack.label || undefined,
         icon_id: stack.icon ? (stack.icon as string) : undefined,
         description: stack.description,
-        category_id:
-          stack.category !== undefined ? stack.category || null : undefined,
       });
       if (set) {
         await conn.query(`UPDATE stack SET ${set.sql} WHERE id = ?`, [
@@ -161,7 +162,31 @@ export default class StackRepository extends BaseRepository {
         }
       }
 
-      if (!set && !stack.versions && !stack.skills) {
+      if (stack.categories) {
+        const existingRows = await conn.query(
+          "SELECT category_id FROM stack_category WHERE stack_id = ?",
+          [stack.id],
+        );
+        const existing: string[] = existingRows.map(
+          (r: { category_id: string }) => r.category_id,
+        );
+        const toAdd = stack.categories.filter((c) => !existing.includes(c));
+        const toRemove = existing.filter((c) => !stack.categories!.includes(c));
+        if (toRemove.length) {
+          await conn.batch(
+            "DELETE FROM stack_category WHERE stack_id = ? AND category_id = ?",
+            toRemove.map((c) => [stack.id, c]),
+          );
+        }
+        if (toAdd.length) {
+          await conn.batch(
+            "INSERT INTO stack_category (stack_id, category_id) VALUES (?, ?)",
+            toAdd.map((c) => [stack.id, c]),
+          );
+        }
+      }
+
+      if (!set && !stack.versions && !stack.skills && !stack.categories) {
         return false;
       }
       return true;
diff --git a/src/types/stackTypes.ts b/src/types/stackTypes.ts
index 5c88b06..c7372db 100644
--- a/src/types/stackTypes.ts
+++ b/src/types/stackTypes.ts
@@ -6,5 +6,5 @@ export interface Stack {
   description?: string;
   versions: string[];
   skills: string[];
-  category?: string | null;
+  categories?: string[];
 }