diff --git a/.husky/pre-push b/.husky/pre-push
index 465de7e..8ce4d1d 100755
--- a/.husky/pre-push
+++ b/.husky/pre-push
@@ -1,5 +1,2 @@
-#!/usr/bin/env sh
-. "$(dirname -- "$0")/_/husky.sh"
-
 npm run typecheck
 npm run test:cov
\ No newline at end of file
diff --git a/package.json b/package.json
index 27e8bea..3f2e968 100644
--- a/package.json
+++ b/package.json
@@ -1,14 +1,14 @@
 {
   "name": "@ciscode/scheduler-kit",
   "version": "0.0.0",
-  "description": "Typed job scheduler for NestJS. @Cron and @Interval and @Timeout decorators. Dynamic runtime scheduling. Concurrent execution guard.",
+  "description": "NestJS advanced scheduler wrapper with dynamic control and concurrency guards.",
   "author": "CisCode",
   "publishConfig": {
     "access": "public"
   },
   "repository": {
     "type": "git",
-    "url": "git+https://github.com/CISCODE-MA/SchedulerKit.git"
+    "url": "git+https://github.com/CISCODE-MA/"
   },
   "license": "MIT",
   "files": [
@@ -45,14 +45,10 @@
   "peerDependencies": {
     "@nestjs/common": "^10 || ^11",
     "@nestjs/core": "^10 || ^11",
-    "@nestjs/platform-express": "^10 || ^11",
+    "@nestjs/schedule": "^4 || ^5",
     "reflect-metadata": "^0.2.2",
     "rxjs": "^7"
   },
-  "dependencies": {
-    "class-transformer": "^0.5.1",
-    "class-validator": "^0.14.1"
-  },
   "devDependencies": {
     "@changesets/cli": "^2.27.7",
     "@eslint/js": "^9.18.0",
@@ -60,11 +56,15 @@
     "@nestjs/core": "^10.4.0",
     "@nestjs/mapped-types": "^2.0.0",
     "@nestjs/platform-express": "^10.4.0",
+    "@nestjs/schedule": "^6.1.1",
     "@nestjs/testing": "^10.4.0",
     "@types/jest": "^29.5.14",
     "@types/node": "^22.10.7",
+    "cron": "^4.4.0",
     "eslint": "^9.18.0",
+    "eslint-config-prettier": "^10.1.8",
     "eslint-plugin-import": "^2.32.0",
+    "eslint-plugin-prettier": "^5.5.5",
     "globals": "^16.5.0",
     "husky": "^9.1.7",
     "jest": "^29.7.0",
diff --git a/src/cron-builder.spec.ts b/src/cron-builder.spec.ts
new file mode 100644
index 0000000..5f9d935
--- /dev/null
+++ b/src/cron-builder.spec.ts
@@ -0,0 +1,113 @@
+import { cron } from "./cron-builder";
+
+describe("cron builder", () => {
+  describe("every(n).minutes()", () => {
+    it("should build every-5-minutes expression", () => {
+      expect(cron.every(5).minutes()).toBe("*/5 * * * *");
+    });
+
+    it("should build every-1-minute expression", () => {
+      expect(cron.every(1).minutes()).toBe("*/1 * * * *");
+    });
+
+    it("should build every-30-minutes expression", () => {
+      expect(cron.every(30).minutes()).toBe("*/30 * * * *");
+    });
+  });
+
+  describe("every(n).hours()", () => {
+    it("should build every-2-hours expression", () => {
+      expect(cron.every(2).hours()).toBe("0 */2 * * *");
+    });
+
+    it("should build every-6-hours expression", () => {
+      expect(cron.every(6).hours()).toBe("0 */6 * * *");
+    });
+  });
+
+  describe("dailyAt()", () => {
+    it('should parse "9am" → 09:00', () => {
+      expect(cron.dailyAt("9am")).toBe("0 9 * * *");
+    });
+
+    it('should parse "9pm" → 21:00', () => {
+      expect(cron.dailyAt("9pm")).toBe("0 21 * * *");
+    });
+
+    it('should parse "9:30am" → 09:30', () => {
+      expect(cron.dailyAt("9:30am")).toBe("30 9 * * *");
+    });
+
+    it('should parse "9:30pm" → 21:30', () => {
+      expect(cron.dailyAt("9:30pm")).toBe("30 21 * * *");
+    });
+
+    it('should parse "12am" (midnight) → 00:00', () => {
+      expect(cron.dailyAt("12am")).toBe("0 0 * * *");
+    });
+
+    it('should parse "12pm" (noon) → 12:00', () => {
+      expect(cron.dailyAt("12pm")).toBe("0 12 * * *");
+    });
+
+    it('should parse 24-hour "14:30" → 14:30', () => {
+      expect(cron.dailyAt("14:30")).toBe("30 14 * * *");
+    });
+
+    it('should parse 24-hour "00:00" → midnight', () => {
+      expect(cron.dailyAt("00:00")).toBe("0 0 * * *");
+    });
+
+    it("should throw on invalid time format", () => {
+      expect(() => cron.dailyAt("invalid")).toThrow();
+    });
+  });
+
+  describe("weekdaysAt()", () => {
+    it("should produce Mon–Fri expression", () => {
+      expect(cron.weekdaysAt("9am")).toBe("0 9 * * 1-5");
+    });
+
+    it("should respect time with minutes", () => {
+      expect(cron.weekdaysAt("9:30am")).toBe("30 9 * * 1-5");
+    });
+  });
+
+  describe("weekendsAt()", () => {
+    it("should produce Sat+Sun expression", () => {
+      expect(cron.weekendsAt("10am")).toBe("0 10 * * 6,0");
+    });
+  });
+
+  describe("weeklyOn()", () => {
+    it("should build monday expression", () => {
+      expect(cron.weeklyOn("monday", "9am")).toBe("0 9 * * 1");
+    });
+
+    it("should build friday expression", () => {
+      expect(cron.weeklyOn("friday", "6pm")).toBe("0 18 * * 5");
+    });
+
+    it("should build sunday expression", () => {
+      expect(cron.weeklyOn("sunday", "12am")).toBe("0 0 * * 0");
+    });
+
+    it("should build saturday expression", () => {
+      expect(cron.weeklyOn("saturday", "8am")).toBe("0 8 * * 6");
+    });
+  });
+
+  describe("monthlyOn()", () => {
+    it("should build 1st of month at midnight", () => {
+      expect(cron.monthlyOn(1, "12am")).toBe("0 0 1 * *");
+    });
+
+    it("should build 15th of month at noon", () => {
+      expect(cron.monthlyOn(15, "12pm")).toBe("0 12 15 * *");
+    });
+
+    it("should build last-ish day at 9am", () => {
+      expect(cron.monthlyOn(28, "9am")).toBe("0 9 28 * *");
+    });
+  });
+});
diff --git a/src/cron-builder.ts b/src/cron-builder.ts
new file mode 100644
index 0000000..84eaa20
--- /dev/null
+++ b/src/cron-builder.ts
@@ -0,0 +1,133 @@
+// ─── Types ─────────────────────────────────────────────────────────────────────
+
+export type DayOfWeek =
+  | "monday"
+  | "tuesday"
+  | "wednesday"
+  | "thursday"
+  | "friday"
+  | "saturday"
+  | "sunday";
+
+// ─── Internal helpers ──────────────────────────────────────────────────────────
+
+const DAY_MAP: Record<DayOfWeek, number> = {
+  sunday: 0,
+  monday: 1,
+  tuesday: 2,
+  wednesday: 3,
+  thursday: 4,
+  friday: 5,
+  saturday: 6,
+};
+
+/**
+ * Parse a human-readable time string into { hour, minute }.
+ *
+ * Accepted formats:
+ *   '9am'    → 09:00
+ *   '9pm'    → 21:00
+ *   '9:30am' → 09:30
+ *   '9:30pm' → 21:30
+ *   '09:00'  → 09:00   (24-hour)
+ *   '21:30'  → 21:30   (24-hour)
+ */
+function parseTime(time: string): { hour: number; minute: number } {
+  const ampm = /^(\d{1,2})(?::(\d{2}))?(am|pm)$/i.exec(time.trim());
+  if (ampm) {
+    let hour = parseInt(ampm[1] as string, 10);
+    const minute = ampm[2] ? parseInt(ampm[2], 10) : 0;
+    const period = (ampm[3] as string).toLowerCase();
+    if (period === "pm" && hour !== 12) hour += 12;
+    if (period === "am" && hour === 12) hour = 0;
+    return { hour, minute };
+  }
+  const h24 = /^(\d{1,2}):(\d{2})$/.exec(time.trim());
+  if (h24) {
+    return { hour: parseInt(h24[1] as string, 10), minute: parseInt(h24[2] as string, 10) };
+  }
+  throw new Error(`Cannot parse time: "${time}". ` + `Use "9am", "9:30pm", "14:30", etc.`);
+}
+
+// ─── Public API ────────────────────────────────────────────────────────────────
+
+/**
+ * Fluent cron expression builder — no cron syntax required.
+ *
+ * @example
+ * import { cron } from '@ciscode/scheduler-kit';
+ *
+ * cron.every(5).minutes()           // "* /5 * * * *"
+ * cron.every(2).hours()             // "0 * /2 * * *"
+ * cron.dailyAt('9am')               // "0 9 * * *"
+ * cron.dailyAt('9:30pm')            // "30 21 * * *"
+ * cron.weekdaysAt('9am')            // "0 9 * * 1-5"
+ * cron.weekendsAt('10am')           // "0 10 * * 6,0"
+ * cron.weeklyOn('monday', '9am')    // "0 9 * * 1"
+ * cron.monthlyOn(1, '9am')          // "0 9 1 * *"   (1st of every month)
+ * cron.monthlyOn(15, '12pm')        // "0 12 15 * *"  (15th of every month)
+ */
+export const cron = {
+  /**
+   * Repeat every N minutes or hours.
+   * @example
+   * cron.every(5).minutes()   // every 5 minutes
+   * cron.every(2).hours()     // every 2 hours
+   */
+  every(n: number) {
+    return {
+      minutes: (): string => `*/${n} * * * *`,
+      hours: (): string => `0 */${n} * * *`,
+    };
+  },
+
+  /**
+   * Once a day at the specified time.
+   * @example
+   * cron.dailyAt('9am')     // every day at 09:00
+   * cron.dailyAt('9:30pm')  // every day at 21:30
+   * cron.dailyAt('00:00')   // every day at midnight
+   */
+  dailyAt(time: string): string {
+    const { hour, minute } = parseTime(time);
+    return `${minute} ${hour} * * *`;
+  },
+
+  /**
+   * Monday–Friday only at the specified time.
+   * @example cron.weekdaysAt('9am')
+   */
+  weekdaysAt(time: string): string {
+    const { hour, minute } = parseTime(time);
+    return `${minute} ${hour} * * 1-5`;
+  },
+
+  /**
+   * Saturday + Sunday only at the specified time.
+   * @example cron.weekendsAt('10am')
+   */
+  weekendsAt(time: string): string {
+    const { hour, minute } = parseTime(time);
+    return `${minute} ${hour} * * 6,0`;
+  },
+
+  /**
+   * Once a week on a specific day at the specified time.
+   * @example cron.weeklyOn('monday', '9am')
+   */
+  weeklyOn(day: DayOfWeek, time: string): string {
+    const { hour, minute } = parseTime(time);
+    return `${minute} ${hour} * * ${DAY_MAP[day]}`;
+  },
+
+  /**
+   * Once a month on a specific day-of-month at the specified time.
+   * @example
+   * cron.monthlyOn(1,  '9am')   // 1st  of every month at 09:00
+   * cron.monthlyOn(15, '12pm')  // 15th of every month at 12:00
+   */
+  monthlyOn(dayOfMonth: number, time: string): string {
+    const { hour, minute } = parseTime(time);
+    return `${minute} ${hour} ${dayOfMonth} * *`;
+  },
+} as const;
diff --git a/src/cron-expression.spec.ts b/src/cron-expression.spec.ts
new file mode 100644
index 0000000..fc6ead9
--- /dev/null
+++ b/src/cron-expression.spec.ts
@@ -0,0 +1,75 @@
+import { CronExpression } from "./cron-expression";
+
+describe("CronExpression", () => {
+  it("should export EVERY_MINUTE", () => {
+    expect(CronExpression.EVERY_MINUTE).toBe("* * * * *");
+  });
+
+  it("should export EVERY_5_MINUTES", () => {
+    expect(CronExpression.EVERY_5_MINUTES).toBe("*/5 * * * *");
+  });
+
+  it("should export EVERY_10_MINUTES", () => {
+    expect(CronExpression.EVERY_10_MINUTES).toBe("*/10 * * * *");
+  });
+
+  it("should export EVERY_15_MINUTES", () => {
+    expect(CronExpression.EVERY_15_MINUTES).toBe("*/15 * * * *");
+  });
+
+  it("should export EVERY_30_MINUTES", () => {
+    expect(CronExpression.EVERY_30_MINUTES).toBe("*/30 * * * *");
+  });
+
+  it("should export EVERY_HOUR", () => {
+    expect(CronExpression.EVERY_HOUR).toBe("0 * * * *");
+  });
+
+  it("should export EVERY_2_HOURS", () => {
+    expect(CronExpression.EVERY_2_HOURS).toBe("0 */2 * * *");
+  });
+
+  it("should export EVERY_6_HOURS", () => {
+    expect(CronExpression.EVERY_6_HOURS).toBe("0 */6 * * *");
+  });
+
+  it("should export EVERY_12_HOURS", () => {
+    expect(CronExpression.EVERY_12_HOURS).toBe("0 */12 * * *");
+  });
+
+  it("should export EVERY_DAY_AT_MIDNIGHT", () => {
+    expect(CronExpression.EVERY_DAY_AT_MIDNIGHT).toBe("0 0 * * *");
+  });
+
+  it("should export EVERY_DAY_AT_9AM", () => {
+    expect(CronExpression.EVERY_DAY_AT_9AM).toBe("0 9 * * *");
+  });
+
+  it("should export EVERY_DAY_AT_NOON", () => {
+    expect(CronExpression.EVERY_DAY_AT_NOON).toBe("0 12 * * *");
+  });
+
+  it("should export EVERY_DAY_AT_6PM", () => {
+    expect(CronExpression.EVERY_DAY_AT_6PM).toBe("0 18 * * *");
+  });
+
+  it("should export EVERY_WEEKDAY_9AM", () => {
+    expect(CronExpression.EVERY_WEEKDAY_9AM).toBe("0 9 * * 1-5");
+  });
+
+  it("should export EVERY_WEEKEND_MIDNIGHT", () => {
+    expect(CronExpression.EVERY_WEEKEND_MIDNIGHT).toBe("0 0 * * 6,0");
+  });
+
+  it("should export EVERY_MONDAY_9AM", () => {
+    expect(CronExpression.EVERY_MONDAY_9AM).toBe("0 9 * * 1");
+  });
+
+  it("should export EVERY_SUNDAY_MIDNIGHT", () => {
+    expect(CronExpression.EVERY_SUNDAY_MIDNIGHT).toBe("0 0 * * 0");
+  });
+
+  it("should export FIRST_OF_MONTH", () => {
+    expect(CronExpression.FIRST_OF_MONTH).toBe("0 0 1 * *");
+  });
+});
diff --git a/src/cron-expression.ts b/src/cron-expression.ts
new file mode 100644
index 0000000..3ce5959
--- /dev/null
+++ b/src/cron-expression.ts
@@ -0,0 +1,34 @@
+/**
+ * Human-readable cron expression constants.
+ *
+ * Use these instead of raw cron strings so every developer on the team
+ * can read the schedule at a glance — no cron knowledge required.
+ *
+ * @example
+ * import { CronExpression } from '@ciscode/scheduler-kit';
+ *
+ * @Cron(CronExpression.EVERY_DAY_AT_9AM, 'daily-digest')
+ * async sendDailyDigest() { ... }
+ */
+export const CronExpression = {
+  EVERY_MINUTE: "* * * * *",
+  EVERY_5_MINUTES: "*/5 * * * *",
+  EVERY_10_MINUTES: "*/10 * * * *",
+  EVERY_15_MINUTES: "*/15 * * * *",
+  EVERY_30_MINUTES: "*/30 * * * *",
+  EVERY_HOUR: "0 * * * *",
+  EVERY_2_HOURS: "0 */2 * * *",
+  EVERY_6_HOURS: "0 */6 * * *",
+  EVERY_12_HOURS: "0 */12 * * *",
+  EVERY_DAY_AT_MIDNIGHT: "0 0 * * *",
+  EVERY_DAY_AT_9AM: "0 9 * * *",
+  EVERY_DAY_AT_NOON: "0 12 * * *",
+  EVERY_DAY_AT_6PM: "0 18 * * *",
+  EVERY_WEEKDAY_9AM: "0 9 * * 1-5", // Mon–Fri at 09:00
+  EVERY_WEEKEND_MIDNIGHT: "0 0 * * 6,0", // Sat + Sun at 00:00
+  EVERY_MONDAY_9AM: "0 9 * * 1",
+  EVERY_SUNDAY_MIDNIGHT: "0 0 * * 0",
+  FIRST_OF_MONTH: "0 0 1 * *", // 1st day of every month at midnight
+} as const;
+
+export type CronExpressionKey = keyof typeof CronExpression;
diff --git a/src/errors/duplicate-job.error.spec.ts b/src/errors/duplicate-job.error.spec.ts
new file mode 100644
index 0000000..773702b
--- /dev/null
+++ b/src/errors/duplicate-job.error.spec.ts
@@ -0,0 +1,23 @@
+import { DuplicateJobError } from "./duplicate-job.error";
+
+describe("DuplicateJobError", () => {
+  it("is an instance of Error", () => {
+    expect(new DuplicateJobError("job")).toBeInstanceOf(Error);
+  });
+
+  it("has name DuplicateJobError", () => {
+    expect(new DuplicateJobError("job").name).toBe("DuplicateJobError");
+  });
+
+  it("message contains the job name", () => {
+    expect(new DuplicateJobError("send-report").message).toContain("send-report");
+  });
+
+  it("can be caught with instanceof check", () => {
+    try {
+      throw new DuplicateJobError("my-job");
+    } catch (e) {
+      expect(e).toBeInstanceOf(DuplicateJobError);
+    }
+  });
+});
diff --git a/src/errors/duplicate-job.error.ts b/src/errors/duplicate-job.error.ts
new file mode 100644
index 0000000..088de8a
--- /dev/null
+++ b/src/errors/duplicate-job.error.ts
@@ -0,0 +1,17 @@
+/**
+ * Thrown when trying to schedule a job whose name is already registered.
+ *
+ * @example
+ * ```typescript
+ * throw new DuplicateJobError('send-report');
+ * // → "Job 'send-report' is already registered. Use reschedule() to change its timing."
+ * ```
+ */
+export class DuplicateJobError extends Error {
+  constructor(name: string) {
+    super(`Job '${name}' is already registered. Use reschedule() to change its timing.`);
+    this.name = "DuplicateJobError";
+    // Maintains proper prototype chain in transpiled ES5 targets
+    Object.setPrototypeOf(this, new.target.prototype);
+  }
+}
diff --git a/src/index.ts b/src/index.ts
index 3026198..983d161 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -3,58 +3,28 @@ import "reflect-metadata";
 // ============================================================================
 // PUBLIC API EXPORTS
 // ============================================================================
-// This file defines what consumers of your module can import.
-// ONLY export what is necessary for external use.
-// Keep entities, repositories, and internal implementation details private.
 
 // ============================================================================
-// MODULE
+// INTERFACES & TYPES
 // ============================================================================
-export { ExampleKitModule } from "./example-kit.module";
-export type { ExampleKitOptions, ExampleKitAsyncOptions } from "./example-kit.module";
+export type {
+  IScheduler,
+  ScheduledJob,
+  ScheduleTiming,
+  CronSchedule,
+  IntervalSchedule,
+  TimeoutSchedule,
+} from "./interfaces/scheduler.interface";
 
 // ============================================================================
-// SERVICES (Main API)
+// ERRORS
 // ============================================================================
-// Export services that consumers will interact with
-export { ExampleService } from "./services/example.service";
+export { DuplicateJobError } from "./errors/duplicate-job.error";
 
 // ============================================================================
-// DTOs (Public Contracts)
+// HELPERS
 // ============================================================================
-// DTOs are the public interface for your API
-// Consumers depend on these, so they must be stable
-export { CreateExampleDto } from "./dto/create-example.dto";
-export { UpdateExampleDto } from "./dto/update-example.dto";
-
-// ============================================================================
-// GUARDS (For Route Protection)
-// ============================================================================
-// Export guards so consumers can use them in their apps
-export { ExampleGuard } from "./guards/example.guard";
-
-// ============================================================================
-// DECORATORS (For Dependency Injection & Metadata)
-// ============================================================================
-// Export decorators for use in consumer controllers/services
-export { ExampleData, ExampleParam } from "./decorators/example.decorator";
-
-// ============================================================================
-// TYPES & INTERFACES (For TypeScript Typing)
-// ============================================================================
-// Export types and interfaces for TypeScript consumers
-// export type { YourCustomType } from './types';
-
-// ============================================================================
-// ❌ NEVER EXPORT (Internal Implementation)
-// ============================================================================
-// These should NEVER be exported from a module:
-// - Entities (internal domain models)
-// - Repositories (infrastructure details)
-//
-// Example of what NOT to export:
-// ❌ export { Example } from './entities/example.entity';
-// ❌ export { ExampleRepository } from './repositories/example.repository';
-//
-// Why? These are internal implementation details that can change.
-// Consumers should only work with DTOs and Services.
+export { CronExpression } from "./cron-expression";
+export type { CronExpressionKey } from "./cron-expression";
+export { cron } from "./cron-builder";
+export type { DayOfWeek } from "./cron-builder";
diff --git a/src/interfaces/scheduler.interface.ts b/src/interfaces/scheduler.interface.ts
new file mode 100644
index 0000000..c7813a6
--- /dev/null
+++ b/src/interfaces/scheduler.interface.ts
@@ -0,0 +1,50 @@
+// ─── Timing Options (Discriminated Union) ─────────────────────────────────────
+// Each variant has a unique literal key, so TypeScript enforces that only ONE
+// timing type can be set at a time.  You cannot pass both `cron` and `interval`.
+
+export type CronSchedule = {
+  cron: string;
+  interval?: never;
+  timeout?: never;
+};
+
+export type IntervalSchedule = {
+  interval: number;
+  cron?: never;
+  timeout?: never;
+};
+
+export type TimeoutSchedule = {
+  timeout: number;
+  cron?: never;
+  interval?: never;
+};
+
+export type ScheduleTiming = CronSchedule | IntervalSchedule | TimeoutSchedule;
+
+// ─── ScheduledJob ──────────────────────────────────────────────────────────────
+// A full job definition: name + handler + exactly one timing type.
+
+export type ScheduledJob = {
+  /** Unique identifier for the job. Used for unschedule / reschedule lookups. */
+  name: string;
+  /** The async function that runs when the timer fires. */
+  handler: () => Promise<void> | void;
+} & ScheduleTiming;
+
+// ─── IScheduler ────────────────────────────────────────────────────────────────
+// The public contract that SchedulerService implements.
+
+export interface IScheduler {
+  /** Register and start a new job. Throws DuplicateJobError if name already exists. */
+  schedule(job: ScheduledJob): void;
+
+  /** Stop and remove a job by name. No-op if the job does not exist. */
+  unschedule(name: string): void;
+
+  /** Atomically stop the old schedule and start a new one for the same job name. */
+  reschedule(name: string, newTiming: ScheduleTiming): void;
+
+  /** Return a snapshot of all currently registered job names. */
+  list(): string[];
+}
diff --git a/tsconfig.build.json b/tsconfig.build.json
index 22fa5d9..661fe66 100644
--- a/tsconfig.build.json
+++ b/tsconfig.build.json
@@ -3,8 +3,16 @@
   "compilerOptions": {
     "noEmit": false,
     "emitDeclarationOnly": false,
-    "outDir": "dist"
+    "outDir": "dist",
+    "module": "CommonJS",
+    "moduleResolution": "Node"
   },
-  "include": ["src/**/*.ts"],
-  "exclude": ["test", "**/*.spec.ts", "**/*.test.ts", "dist", "node_modules"]
+  "include": [
+    "src/index.ts",
+    "src/cron-expression.ts",
+    "src/cron-builder.ts",
+    "src/interfaces/scheduler.interface.ts",
+    "src/errors/duplicate-job.error.ts"
+  ],
+  "exclude": ["dist", "node_modules", "**/*.spec.ts", "**/*.test.ts"]
 }