diff --git a/packages/keystore/src/__tests__/encrypted-file.test.ts b/packages/keystore/src/__tests__/encrypted-file.test.ts
index a2196b6..41ec5f9 100644
--- a/packages/keystore/src/__tests__/encrypted-file.test.ts
+++ b/packages/keystore/src/__tests__/encrypted-file.test.ts
@@ -157,6 +157,34 @@ describe('EncryptedFileKeyStore', () => {
     });
   });
 
+  describe('key overwrite (re-init)', () => {
+    it('generateAndStore twice with same ID uses the new key', async () => {
+      const store = new EncryptedFileKeyStore(tempDir, PASSPHRASE);
+      const { publicKey: pk1 } = await store.generateAndStore(DEVICE_ID);
+      const { publicKey: pk2 } = await store.generateAndStore(DEVICE_ID);
+
+      // Keys should differ
+      expect(pk1).not.toEqual(pk2);
+
+      // Sign with the store — must use the NEW key
+      const msg = new TextEncoder().encode('test overwrite');
+      const sig = await store.sign(DEVICE_ID, msg);
+
+      // Signature must verify against the NEW public key
+      expect(verifyMessage(sig, msg, pk2)).toBe(true);
+      // Signature must NOT verify against the OLD public key
+      expect(verifyMessage(sig, msg, pk1)).toBe(false);
+    });
+
+    it('getPublicKey returns the new key after overwrite', async () => {
+      const store = new EncryptedFileKeyStore(tempDir, PASSPHRASE);
+      await store.generateAndStore(DEVICE_ID);
+      const { publicKey: pk2 } = await store.generateAndStore(DEVICE_ID);
+
+      expect(await store.getPublicKey(DEVICE_ID)).toEqual(pk2);
+    });
+  });
+
   describe('adversarial: tampered key file', () => {
     it('fails to decrypt if ciphertext is modified', async () => {
       const store = new EncryptedFileKeyStore(tempDir, PASSPHRASE);
diff --git a/packages/keystore/src/__tests__/macos-keychain.test.ts b/packages/keystore/src/__tests__/macos-keychain.test.ts
new file mode 100644
index 0000000..15fe87b
--- /dev/null
+++ b/packages/keystore/src/__tests__/macos-keychain.test.ts
@@ -0,0 +1,105 @@
+import { describe, it, expect, afterEach, setDefaultTimeout } from 'bun:test';
+import { verifyMessage } from '@authmesh/core';
+
+setDefaultTimeout(30_000);
+
+// These tests require the macOS Keychain Swift helper and only run on macOS.
+// They use a unique tag prefix to avoid colliding with real amesh keys.
+const TEST_DEVICE_ID = 'am_test_keychain_ci';
+
+const isMacOS = process.platform === 'darwin';
+
+// Skip all tests on non-macOS platforms
+const describeOnMac = isMacOS ? describe : describe.skip;
+
+// Dynamic import to avoid errors on non-macOS
+async function getKeychainStore() {
+  const { MacOSKeychainKeyStore, isMacOSKeychainAvailable } =
+    await import('../drivers/macos-keychain.js');
+  const { available } = await isMacOSKeychainAvailable();
+  return { MacOSKeychainKeyStore, available };
+}
+
+describeOnMac('MacOSKeychainKeyStore', () => {
+  afterEach(async () => {
+    // Clean up test keys from keychain
+    try {
+      const { MacOSKeychainKeyStore } = await getKeychainStore();
+      const store = new MacOSKeychainKeyStore('/tmp');
+      await store.delete(TEST_DEVICE_ID);
+    } catch {
+      // ignore cleanup errors
+    }
+  });
+
+  it('generates a 33-byte compressed P-256 public key', async () => {
+    const { MacOSKeychainKeyStore, available } = await getKeychainStore();
+    if (!available) return;
+    const store = new MacOSKeychainKeyStore('/tmp');
+    const { publicKey } = await store.generateAndStore(TEST_DEVICE_ID);
+
+    expect(publicKey).toBeInstanceOf(Uint8Array);
+    expect(publicKey.length).toBe(33);
+    expect([0x02, 0x03]).toContain(publicKey[0]);
+  });
+
+  it('sign produces a verifiable 64-byte signature', async () => {
+    const { MacOSKeychainKeyStore, available } = await getKeychainStore();
+    if (!available) return;
+    const store = new MacOSKeychainKeyStore('/tmp');
+    const { publicKey } = await store.generateAndStore(TEST_DEVICE_ID);
+
+    const msg = new TextEncoder().encode('test message');
+    const sig = await store.sign(TEST_DEVICE_ID, msg);
+
+    expect(sig.length).toBe(64);
+    expect(verifyMessage(sig, msg, publicKey)).toBe(true);
+  });
+
+  it('generateAndStore twice with same ID uses the new key (stale key regression)', async () => {
+    const { MacOSKeychainKeyStore, available } = await getKeychainStore();
+    if (!available) return;
+    const store = new MacOSKeychainKeyStore('/tmp');
+
+    // First generate
+    const { publicKey: pk1 } = await store.generateAndStore(TEST_DEVICE_ID);
+
+    // Second generate — same device ID (simulates `amesh init --force`)
+    const { publicKey: pk2 } = await store.generateAndStore(TEST_DEVICE_ID);
+
+    // Keys should differ
+    expect(pk1).not.toEqual(pk2);
+
+    // Sign must use the NEW key
+    const msg = new TextEncoder().encode('stale key regression test');
+    const sig = await store.sign(TEST_DEVICE_ID, msg);
+
+    // Must verify against the NEW public key
+    expect(verifyMessage(sig, msg, pk2)).toBe(true);
+    // Must NOT verify against the OLD public key
+    expect(verifyMessage(sig, msg, pk1)).toBe(false);
+  });
+
+  it('getPublicKey returns the new key after overwrite', async () => {
+    const { MacOSKeychainKeyStore, available } = await getKeychainStore();
+    if (!available) return;
+    const store = new MacOSKeychainKeyStore('/tmp');
+
+    await store.generateAndStore(TEST_DEVICE_ID);
+    const { publicKey: pk2 } = await store.generateAndStore(TEST_DEVICE_ID);
+
+    const retrieved = await store.getPublicKey(TEST_DEVICE_ID);
+    expect(retrieved).toEqual(pk2);
+  });
+
+  it('delete removes the key', async () => {
+    const { MacOSKeychainKeyStore, available } = await getKeychainStore();
+    if (!available) return;
+    const store = new MacOSKeychainKeyStore('/tmp');
+
+    await store.generateAndStore(TEST_DEVICE_ID);
+    await store.delete(TEST_DEVICE_ID);
+
+    await expect(store.sign(TEST_DEVICE_ID, new TextEncoder().encode('test'))).rejects.toThrow();
+  });
+});
diff --git a/packages/keystore/swift/main.swift b/packages/keystore/swift/main.swift
index 06f8783..c405226 100644
--- a/packages/keystore/swift/main.swift
+++ b/packages/keystore/swift/main.swift
@@ -105,6 +105,13 @@ case "check":
 
 case "generate":
     guard let id = cmd.deviceId else { fail("missing_device_id") }
+    // Delete ALL existing keys with this tag to avoid stale key shadowing.
+    // SecItemDelete may only remove one item per call, so loop until clean.
+    let delQuery: [String: Any] = [
+        kSecClass as String: kSecClassKey,
+        kSecAttrApplicationTag as String: tagFor(id),
+    ]
+    while SecItemDelete(delQuery as CFDictionary) == errSecSuccess {}
     // Try Secure Enclave first, fall back to software keychain
     if let key = trySecureEnclaveGenerate(id) {
         guard let pub = exportPubKey(key) else { fail("export_failed") }
@@ -134,10 +141,11 @@ case "get-public-key":
 
 case "delete":
     guard let id = cmd.deviceId else { fail("missing_device_id") }
-    SecItemDelete([
+    let delQ: [String: Any] = [
         kSecClass as String: kSecClassKey,
         kSecAttrApplicationTag as String: tagFor(id),
-    ] as CFDictionary)
+    ]
+    while SecItemDelete(delQ as CFDictionary) == errSecSuccess {}
     ok()
 
 default: