diff --git a/src/db/locator.ts b/src/db/locator.ts
new file mode 100644
index 0000000..9dcac53
--- /dev/null
+++ b/src/db/locator.ts
@@ -0,0 +1,37 @@
+import type { Database } from 'bun:sqlite';
+
+/**
+ * Error específico cuando se intenta acceder a la DB sin haberla configurado.
+ */
+export class DbNotConfiguredError extends Error {
+  constructor(message: string = 'Database has not been configured. Call setDb(db) before using getDb().') {
+    super(message);
+    this.name = 'DbNotConfiguredError';
+  }
+}
+
+let currentDb: Database | null = null;
+
+/**
+ * Establece la instancia global de DB.
+ * Se permite sobrescribir (útil en tests).
+ */
+export function setDb(db: Database): void {
+  currentDb = db;
+}
+
+/**
+ * Obtiene la instancia global de DB o lanza si no está configurada.
+ */
+export function getDb(): Database {
+  if (currentDb) return currentDb;
+  throw new DbNotConfiguredError('Database has not been configured. Call setDb(db) before using getDb().');
+}
+
+/**
+ * Ejecuta una función con la DB actual (sync o async) y devuelve su resultado.
+ */
+export function withDb<T>(fn: (db: Database) => T | Promise<T>): T | Promise<T> {
+  const db = getDb();
+  return fn(db);
+}
diff --git a/tests/unit/db/locator.test.ts b/tests/unit/db/locator.test.ts
new file mode 100644
index 0000000..6d73758
--- /dev/null
+++ b/tests/unit/db/locator.test.ts
@@ -0,0 +1,50 @@
+import Database from 'bun:sqlite';
+import { describe, it, expect } from 'bun:test';
+import { getDb, setDb, withDb, DbNotConfiguredError } from '../../../src/db/locator';
+
+describe('db/locator', () => {
+  it('getDb lanza si no está configurada', () => {
+    expect(() => getDb()).toThrow(DbNotConfiguredError);
+  });
+
+  it('setDb y getDb devuelven la misma instancia', () => {
+    const db = new Database(':memory:');
+    setDb(db);
+    expect(getDb()).toBe(db);
+    try { db.close(); } catch {}
+  });
+
+  it('withDb soporta callback síncrono', () => {
+    const db = new Database(':memory:');
+    setDb(db);
+    const result = withDb(d => {
+      expect(d).toBe(db);
+      return 42;
+    });
+    expect(result).toBe(42);
+    try { db.close(); } catch {}
+  });
+
+  it('withDb soporta callback asíncrono', async () => {
+    const db = new Database(':memory:');
+    setDb(db);
+    const result = await withDb(async d => {
+      expect(d).toBe(db);
+      await Promise.resolve();
+      return 'ok';
+    });
+    expect(result).toBe('ok');
+    try { db.close(); } catch {}
+  });
+
+  it('permitir sobrescritura de setDb', () => {
+    const db1 = new Database(':memory:');
+    const db2 = new Database(':memory:');
+    setDb(db1);
+    setDb(db2);
+    const got = getDb();
+    expect(got).toBe(db2);
+    try { db1.close(); } catch {}
+    try { db2.close(); } catch {}
+  });
+});