diff --git a/.gitignore b/.gitignore
index a2a6553cd3..0438549485 100644
--- a/.gitignore
+++ b/.gitignore
@@ -61,4 +61,4 @@ gemini-debug.log
 .genkit
 .gemini-clipboard/
 .eslintcache
-evals/logs/
+evals/logs/
\ No newline at end of file
diff --git a/packages/core/src/config/storage.ts b/packages/core/src/config/storage.ts
index f66d60ef8b..e8530887b3 100644
--- a/packages/core/src/config/storage.ts
+++ b/packages/core/src/config/storage.ts
@@ -289,6 +289,10 @@ export class Storage {
     return path.join(this.getProjectTempDir(), 'plans');
   }
 
+  getProjectTempTrackerDir(): string {
+    return path.join(this.getProjectTempDir(), 'tracker');
+  }
+
   getPlansDir(): string {
     if (this.customPlansDir) {
       const resolvedPath = path.resolve(
diff --git a/packages/core/src/services/trackerService.test.ts b/packages/core/src/services/trackerService.test.ts
new file mode 100644
index 0000000000..70a29d25af
--- /dev/null
+++ b/packages/core/src/services/trackerService.test.ts
@@ -0,0 +1,142 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import * as fs from 'node:fs/promises';
+import * as os from 'node:os';
+import * as path from 'node:path';
+import { TrackerService } from './trackerService.js';
+import { TaskStatus, TaskType, type TrackerTask } from './trackerTypes.js';
+
+describe('TrackerService', () => {
+  let testTrackerDir: string;
+  let service: TrackerService;
+
+  beforeEach(async () => {
+    testTrackerDir = await fs.mkdtemp(
+      path.join(os.tmpdir(), 'tracker-service-test-'),
+    );
+    service = new TrackerService(testTrackerDir);
+  });
+
+  afterEach(async () => {
+    await fs.rm(testTrackerDir, { recursive: true, force: true });
+  });
+
+  it('should create a task with a generated 6-char hex ID', async () => {
+    const taskData: Omit<TrackerTask, 'id'> = {
+      title: 'Test Task',
+      description: 'Test Description',
+      type: TaskType.TASK,
+      status: TaskStatus.OPEN,
+      dependencies: [],
+    };
+
+    const task = await service.createTask(taskData);
+    expect(task.id).toMatch(/^[0-9a-f]{6}$/);
+    expect(task.title).toBe(taskData.title);
+
+    const savedTask = await service.getTask(task.id);
+    expect(savedTask).toEqual(task);
+  });
+
+  it('should list all tasks', async () => {
+    await service.createTask({
+      title: 'Task 1',
+      description: 'Desc 1',
+      type: TaskType.TASK,
+      status: TaskStatus.OPEN,
+      dependencies: [],
+    });
+    await service.createTask({
+      title: 'Task 2',
+      description: 'Desc 2',
+      type: TaskType.TASK,
+      status: TaskStatus.OPEN,
+      dependencies: [],
+    });
+
+    const tasks = await service.listTasks();
+    expect(tasks.length).toBe(2);
+    expect(tasks.map((t) => t.title)).toContain('Task 1');
+    expect(tasks.map((t) => t.title)).toContain('Task 2');
+  });
+
+  it('should update a task', async () => {
+    const task = await service.createTask({
+      title: 'Original Title',
+      description: 'Original Desc',
+      type: TaskType.TASK,
+      status: TaskStatus.OPEN,
+      dependencies: [],
+    });
+
+    const updated = await service.updateTask(task.id, {
+      title: 'New Title',
+      status: TaskStatus.IN_PROGRESS,
+    });
+    expect(updated.title).toBe('New Title');
+    expect(updated.status).toBe('in_progress');
+    expect(updated.description).toBe('Original Desc');
+
+    const retrieved = await service.getTask(task.id);
+    expect(retrieved).toEqual(updated);
+  });
+
+  it('should prevent closing a task if dependencies are not closed', async () => {
+    const dep = await service.createTask({
+      title: 'Dependency',
+      description: 'Must be closed first',
+      type: TaskType.TASK,
+      status: TaskStatus.OPEN,
+      dependencies: [],
+    });
+
+    const task = await service.createTask({
+      title: 'Main Task',
+      description: 'Depends on dep',
+      type: TaskType.TASK,
+      status: TaskStatus.OPEN,
+      dependencies: [dep.id],
+    });
+
+    await expect(
+      service.updateTask(task.id, { status: TaskStatus.CLOSED }),
+    ).rejects.toThrow(/Cannot close task/);
+
+    // Close dependency
+    await service.updateTask(dep.id, { status: TaskStatus.CLOSED });
+
+    // Now it should work
+    const updated = await service.updateTask(task.id, {
+      status: TaskStatus.CLOSED,
+    });
+    expect(updated.status).toBe('closed');
+  });
+
+  it('should detect circular dependencies', async () => {
+    const taskA = await service.createTask({
+      title: 'Task A',
+      description: 'A',
+      type: TaskType.TASK,
+      status: TaskStatus.OPEN,
+      dependencies: [],
+    });
+
+    const taskB = await service.createTask({
+      title: 'Task B',
+      description: 'B',
+      type: TaskType.TASK,
+      status: TaskStatus.OPEN,
+      dependencies: [taskA.id],
+    });
+
+    // Try to make A depend on B
+    await expect(
+      service.updateTask(taskA.id, { dependencies: [taskB.id] }),
+    ).rejects.toThrow(/Circular dependency detected/);
+  });
+});
diff --git a/packages/core/src/services/trackerService.ts b/packages/core/src/services/trackerService.ts
new file mode 100644
index 0000000000..3203b759e1
--- /dev/null
+++ b/packages/core/src/services/trackerService.ts
@@ -0,0 +1,223 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import fs from 'node:fs/promises';
+import path from 'node:path';
+import { randomBytes } from 'node:crypto';
+import { debugLogger } from '../utils/debugLogger.js';
+import { coreEvents } from '../utils/events.js';
+import {
+  TrackerTaskSchema,
+  TaskStatus,
+  type TrackerTask,
+} from './trackerTypes.js';
+import { type z } from 'zod';
+
+export class TrackerService {
+  private readonly tasksDir: string;
+
+  private initialized = false;
+
+  constructor(readonly trackerDir: string) {
+    this.tasksDir = trackerDir;
+  }
+
+  private async ensureInitialized(): Promise<void> {
+    if (!this.initialized) {
+      await fs.mkdir(this.tasksDir, { recursive: true });
+      this.initialized = true;
+    }
+  }
+
+  /**
+   * Generates a 6-character hex ID.
+   */
+  private generateId(): string {
+    return randomBytes(3).toString('hex');
+  }
+
+  /**
+   * Creates a new task and saves it to disk.
+   */
+  async createTask(taskData: Omit<TrackerTask, 'id'>): Promise<TrackerTask> {
+    await this.ensureInitialized();
+    const id = this.generateId();
+    const task: TrackerTask = {
+      ...taskData,
+      id,
+    };
+
+    await this.saveTask(task);
+    return task;
+  }
+
+  /**
+   * Helper to read and validate a JSON file.
+   */
+  private async readJsonFile<T>(
+    filePath: string,
+    schema: z.ZodSchema<T>,
+  ): Promise<T | null> {
+    try {
+      const content = await fs.readFile(filePath, 'utf8');
+      const data: unknown = JSON.parse(content);
+      return schema.parse(data);
+    } catch (error) {
+      if (
+        error &&
+        typeof error === 'object' &&
+        'code' in error &&
+        error.code === 'ENOENT'
+      ) {
+        return null;
+      }
+
+      const fileName = path.basename(filePath);
+      debugLogger.warn(`Failed to read or parse task file ${fileName}:`, error);
+      coreEvents.emitFeedback(
+        'warning',
+        `Task tracker encountered an issue reading ${fileName}. The data might be corrupted.`,
+        error,
+      );
+      throw error;
+    }
+  }
+
+  /**
+   * Reads a task by ID.
+   */
+  async getTask(id: string): Promise<TrackerTask | null> {
+    await this.ensureInitialized();
+    const taskPath = path.join(this.tasksDir, `${id}.json`);
+    return this.readJsonFile(taskPath, TrackerTaskSchema);
+  }
+
+  /**
+   * Lists all tasks in the tracker.
+   */
+  async listTasks(): Promise<TrackerTask[]> {
+    await this.ensureInitialized();
+    try {
+      const files = await fs.readdir(this.tasksDir);
+      const jsonFiles = files.filter((f: string) => f.endsWith('.json'));
+      const tasks = await Promise.all(
+        jsonFiles.map(async (f: string) => {
+          const taskPath = path.join(this.tasksDir, f);
+          return this.readJsonFile(taskPath, TrackerTaskSchema);
+        }),
+      );
+      return tasks.filter((t): t is TrackerTask => t !== null);
+    } catch (error) {
+      if (
+        error &&
+        typeof error === 'object' &&
+        'code' in error &&
+        error.code === 'ENOENT'
+      ) {
+        return [];
+      }
+      throw error;
+    }
+  }
+
+  /**
+   * Updates an existing task and saves it to disk.
+   */
+  async updateTask(
+    id: string,
+    updates: Partial<TrackerTask>,
+  ): Promise<TrackerTask> {
+    const task = await this.getTask(id);
+    if (!task) {
+      throw new Error(`Task with ID ${id} not found.`);
+    }
+
+    const updatedTask = { ...task, ...updates };
+
+    // Validate status transition if closing
+    if (
+      updatedTask.status === TaskStatus.CLOSED &&
+      task.status !== TaskStatus.CLOSED
+    ) {
+      await this.validateCanClose(updatedTask);
+    }
+
+    // Validate circular dependencies if dependencies changed
+    if (updates.dependencies) {
+      await this.validateNoCircularDependencies(updatedTask);
+    }
+
+    await this.saveTask(updatedTask);
+    return updatedTask;
+  }
+
+  /**
+   * Saves a task to disk.
+   */
+  private async saveTask(task: TrackerTask): Promise<void> {
+    const taskPath = path.join(this.tasksDir, `${task.id}.json`);
+    await fs.writeFile(taskPath, JSON.stringify(task, null, 2), 'utf8');
+  }
+
+  /**
+   * Validates that a task can be closed (all dependencies must be closed).
+   */
+  private async validateCanClose(task: TrackerTask): Promise<void> {
+    for (const depId of task.dependencies) {
+      const dep = await this.getTask(depId);
+      if (!dep) {
+        throw new Error(`Dependency ${depId} not found for task ${task.id}.`);
+      }
+      if (dep.status !== TaskStatus.CLOSED) {
+        throw new Error(
+          `Cannot close task ${task.id} because dependency ${depId} is still ${dep.status}.`,
+        );
+      }
+    }
+  }
+
+  /**
+   * Validates that there are no circular dependencies.
+   */
+  private async validateNoCircularDependencies(
+    task: TrackerTask,
+  ): Promise<void> {
+    const allTasks = await this.listTasks();
+    const taskMap = new Map<string, TrackerTask>(
+      allTasks.map((t) => [t.id, t]),
+    );
+    // Ensure the current (possibly unsaved) task state is used
+    taskMap.set(task.id, task);
+
+    const visited = new Set<string>();
+    const stack = new Set<string>();
+
+    const check = (currentId: string) => {
+      if (stack.has(currentId)) {
+        throw new Error(
+          `Circular dependency detected involving task ${currentId}.`,
+        );
+      }
+      if (visited.has(currentId)) {
+        return;
+      }
+
+      visited.add(currentId);
+      stack.add(currentId);
+
+      const currentTask = taskMap.get(currentId);
+      if (currentTask) {
+        for (const depId of currentTask.dependencies) {
+          check(depId);
+        }
+      }
+
+      stack.delete(currentId);
+    };
+
+    check(task.id);
+  }
+}
diff --git a/packages/core/src/services/trackerTypes.ts b/packages/core/src/services/trackerTypes.ts
new file mode 100644
index 0000000000..7c48f5bcd4
--- /dev/null
+++ b/packages/core/src/services/trackerTypes.ts
@@ -0,0 +1,36 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { z } from 'zod';
+
+export enum TaskType {
+  EPIC = 'epic',
+  TASK = 'task',
+  BUG = 'bug',
+}
+export const TaskTypeSchema = z.nativeEnum(TaskType);
+
+export enum TaskStatus {
+  OPEN = 'open',
+  IN_PROGRESS = 'in_progress',
+  BLOCKED = 'blocked',
+  CLOSED = 'closed',
+}
+export const TaskStatusSchema = z.nativeEnum(TaskStatus);
+
+export const TrackerTaskSchema = z.object({
+  id: z.string().length(6),
+  title: z.string(),
+  description: z.string(),
+  type: TaskTypeSchema,
+  status: TaskStatusSchema,
+  parentId: z.string().optional(),
+  dependencies: z.array(z.string()),
+  subagentSessionId: z.string().optional(),
+  metadata: z.record(z.unknown()).optional(),
+});
+
+export type TrackerTask = z.infer<typeof TrackerTaskSchema>;