diff --git a/src/core/services/taskService.ts b/src/core/services/taskService.ts
new file mode 100644
index 0000000..e48138e
--- /dev/null
+++ b/src/core/services/taskService.ts
@@ -0,0 +1,79 @@
+import { join } from 'path';
+import { getEntityDir } from '../paths.js';
+import { getNextId } from '../counter.js';
+import { readEntity, writeEntity } from '../files.js';
+import { TaskSchema, type Task } from '../schema.js';
+import { Index } from '../index.js';
+
+export function createTask(cwd: string, options: Partial<Task> = {}): Task {
+  const now = new Date().toISOString();
+  const task: Task = TaskSchema.parse({
+    id: getNextId(cwd, 'task'),
+    title: options.title ?? 'Untitled',
+    description: options.description ?? '',
+    status: 'open',
+    priority: options.priority ?? 'medium',
+    role: options.role,
+    assignedTo: options.assignedTo,
+    createdAt: now,
+    updatedAt: now,
+  });
+
+  const filePath = join(getEntityDir(cwd, 'tasks'), `${task.id}.md`);
+  writeEntity(filePath, task, `# ${task.title}\n\n${task.description}`);
+
+  const index = new Index(cwd);
+  index.upsert(toIndexEntry(task, filePath));
+  index.close();
+
+  return task;
+}
+
+export function listTasks(cwd: string, filters?: { status?: string; role?: string }): ReturnType<Index['list']> {
+  const index = new Index(cwd);
+  const tasks = index.list('task', filters);
+  index.close();
+  return tasks;
+}
+
+export function getTask(cwd: string, id: string): { task: Task; body: string; filePath: string } {
+  const filePath = join(getEntityDir(cwd, 'tasks'), `${id}.md`);
+  const { frontmatter, body } = readEntity(filePath);
+  return { task: TaskSchema.parse(frontmatter), body, filePath };
+}
+
+export function updateTask(cwd: string, id: string, patch: Partial<Task>): Task {
+  const { task, body, filePath } = getTask(cwd, id);
+  const updated: Task = TaskSchema.parse({ ...task, ...patch, updatedAt: new Date().toISOString() });
+  writeEntity(filePath, updated, body);
+
+  const index = new Index(cwd);
+  index.upsert(toIndexEntry(updated, filePath));
+  index.close();
+
+  return updated;
+}
+
+export function claimTask(cwd: string, id: string, agentName: string): Task {
+  return updateTask(cwd, id, { status: 'in_progress', assignedTo: agentName });
+}
+
+export function doneTask(cwd: string, id: string): Task {
+  return updateTask(cwd, id, { status: 'done' });
+}
+
+function toIndexEntry(task: Task, filePath: string) {
+  return {
+    id: task.id,
+    type: 'task',
+    title: task.title,
+    content: `${task.description} ${task.tags.join(' ')}`,
+    filePath,
+    createdAt: task.createdAt,
+    updatedAt: task.updatedAt,
+    status: task.status,
+    role: task.role,
+    assignedTo: task.assignedTo,
+    tags: JSON.stringify(task.tags),
+  };
+}
diff --git a/tests/taskService.test.ts b/tests/taskService.test.ts
new file mode 100644
index 0000000..fd13673
--- /dev/null
+++ b/tests/taskService.test.ts
@@ -0,0 +1,38 @@
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import { mkdtempSync, rmSync } from 'fs';
+import { tmpdir } from 'os';
+import { join } from 'path';
+import { createTask, listTasks, getTask, claimTask, doneTask } from '../src/core/services/taskService.js';
+
+describe('taskService', () => {
+  let cwd: string;
+
+  beforeEach(() => {
+    cwd = mkdtempSync(join(tmpdir(), 'ah-task-'));
+  });
+
+  afterEach(() => {
+    rmSync(cwd, { recursive: true, force: true });
+  });
+
+  it('creates a task', () => {
+    const task = createTask(cwd, { title: 'Test', role: 'implementer' });
+    expect(task.id).toBe('TSK-0001');
+    expect(task.title).toBe('Test');
+    expect(task.status).toBe('open');
+  });
+
+  it('lists tasks', () => {
+    createTask(cwd, { title: 'A', role: 'implementer' });
+    expect(listTasks(cwd)).toHaveLength(1);
+  });
+
+  it('claims and completes a task', () => {
+    const task = createTask(cwd, { title: 'B', role: 'implementer' });
+    const claimed = claimTask(cwd, task.id, 'codex');
+    expect(claimed.status).toBe('in_progress');
+    expect(claimed.assignedTo).toBe('codex');
+    const done = doneTask(cwd, task.id);
+    expect(done.status).toBe('done');
+  });
+});