diff --git a/src/core/counter.ts b/src/core/counter.ts
new file mode 100644
index 0000000..f14bdd1
--- /dev/null
+++ b/src/core/counter.ts
@@ -0,0 +1,27 @@
+import { readFileSync, writeFileSync, existsSync, mkdirSync } from 'fs';
+import { getAgentHubDir, getCounterPath } from './paths.js';
+
+const prefixes: Record<string, string> = {
+  task: 'TSK',
+  handoff: 'HOF',
+  decision: 'DEC',
+  memory: 'MEM',
+};
+
+export type CounterType = keyof typeof prefixes;
+
+export function getNextId(cwd: string, type: CounterType): string {
+  const path = getCounterPath(cwd);
+  const counters: Record<string, number> = existsSync(path)
+    ? JSON.parse(readFileSync(path, 'utf-8'))
+    : {};
+
+  const current = counters[type] ?? 0;
+  const next = current + 1;
+  counters[type] = next;
+
+  mkdirSync(getAgentHubDir(cwd), { recursive: true });
+  writeFileSync(path, JSON.stringify(counters, null, 2));
+
+  return `${prefixes[type]}-${String(next).padStart(4, '0')}`;
+}
diff --git a/tests/counter.test.ts b/tests/counter.test.ts
new file mode 100644
index 0000000..195c2bf
--- /dev/null
+++ b/tests/counter.test.ts
@@ -0,0 +1,28 @@
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import { mkdtempSync, rmSync } from 'fs';
+import { tmpdir } from 'os';
+import { join } from 'path';
+import { getNextId } from '../src/core/counter.js';
+
+describe('counter', () => {
+  let cwd: string;
+
+  beforeEach(() => {
+    cwd = mkdtempSync(join(tmpdir(), 'agenthub-'));
+  });
+
+  afterEach(() => {
+    rmSync(cwd, { recursive: true, force: true });
+  });
+
+  it('generates sequential task ids', () => {
+    expect(getNextId(cwd, 'task')).toBe('TSK-0001');
+    expect(getNextId(cwd, 'task')).toBe('TSK-0002');
+  });
+
+  it('keeps counters separate by type', () => {
+    expect(getNextId(cwd, 'handoff')).toBe('HOF-0001');
+    expect(getNextId(cwd, 'task')).toBe('TSK-0001');
+    expect(getNextId(cwd, 'handoff')).toBe('HOF-0002');
+  });
+});