diff --git a/packages/server/test/federation-handshake-desync.test.ts b/packages/server/test/federation-handshake-desync.test.ts
new file mode 100644
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+++ b/packages/server/test/federation-handshake-desync.test.ts
@@ -0,0 +1,128 @@
+import { describe, it, expect, afterEach } from 'vitest';
+import {
+  bootTwoInstancesForHandshake,
+  registerAdmin,
+  initiatePeering,
+  resetPeer,
+  getPeer,
+  s2sHealthy,
+  simulateReset,
+} from './helpers/realHandshake.js';
+import type { TwoInstanceHarness } from './helpers/twoInstanceHarness.js';
+import { openInspector } from './helpers/dbInspect.js';
+
+/**
+ * Acceptance-gate integration suite for the federation handshake desync bugs.
+ *
+ * These cases drive the REAL cross-instance `/peer/initiate`→`/peer/accept`
+ * handshake (via realHandshake.ts) rather than seeding peer rows. This is the
+ * RED baseline: #1 (control) passes on current code, #2 (BUG-1) and #4 (BUG-2)
+ * are EXPECTED to fail against current (unfixed) code — the fixes in later tasks
+ * turn them green. Do NOT modify product code to make #2/#4 pass here.
+ */
+
+let h: TwoInstanceHarness;
+afterEach(async () => {
+  if (h) await h.cleanup();
+});
+
+describe('federation handshake desync (BUG-1/BUG-2)', () => {
+  it('#1 control: clean handshake activates both sides with matching secret', async () => {
+    h = await bootTwoInstancesForHandshake();
+    const adminI = await registerAdmin(h.home);
+    await registerAdmin(h.remote);
+
+    const { status } = await initiatePeering(h.home, adminI.token, h.remote);
+    expect(status).toBe(200);
+
+    expect(await s2sHealthy(h.home, h.remote)).toBe(true);
+    expect(await s2sHealthy(h.remote, h.home)).toBe(true);
+
+    const homeInsp = openInspector(h.home);
+    const remoteInsp = openInspector(h.remote);
+    try {
+      const iSecret = homeInsp.federationPeer(h.remote.origin)?.hmacSecret;
+      const rSecret = remoteInsp.federationPeer(h.home.origin)?.hmacSecret;
+      expect(iSecret).toBeTruthy();
+      expect(rSecret).toBeTruthy();
+      expect(iSecret).toBe(rSecret);
+    } finally {
+      homeInsp.close();
+      remoteInsp.close();
+    }
+  }, 60_000);
+
+  it('#2 BUG-1: initiator must NOT false-activate against a survivor that holds a row', async () => {
+    h = await bootTwoInstancesForHandshake();
+    const adminI = await registerAdmin(h.home);
+    await registerAdmin(h.remote);
+
+    // Establish peering, then reset home (fresh incarnation, no row).
+    // remote still holds its old active row for home's origin.
+    await initiatePeering(h.home, adminI.token, h.remote);
+    expect(await s2sHealthy(h.home, h.remote)).toBe(true);
+
+    const freshHome = await simulateReset(h.home, h);
+    const adminI2 = await registerAdmin(freshHome);
+
+    // Fresh home re-initiates into the survivor remote (which still holds its old active row).
+    const { status, body } = await initiatePeering(freshHome, adminI2.token, h.remote);
+
+    // FIX (green): remote refuses honestly with 409; fresh home does NOT end up active-but-dead.
+    expect(status).toBe(409);
+    expect(body.code).toBe('PEER_EXISTS_RESET_REQUIRED');
+
+    // Fresh home must hold no false-active row for remote's origin.
+    const insp = openInspector(freshHome);
+    try {
+      const iRow = insp.federationPeer(h.remote.origin);
+      expect(iRow?.status === 'active').toBe(false);
+    } finally {
+      insp.close();
+    }
+  }, 60_000);
+
+  it('#4 BUG-2: one-click Re-peer never reports success on a dead peering; genuinely recovers', async () => {
+    h = await bootTwoInstancesForHandshake();
+    const adminI = await registerAdmin(h.home);
+    const adminR = await registerAdmin(h.remote);
+
+    await initiatePeering(h.home, adminI.token, h.remote);
+    expect(await s2sHealthy(h.home, h.remote)).toBe(true);
+
+    const freshHome = await simulateReset(h.home, h);
+    const adminIf = await registerAdmin(freshHome);
+
+    // Fresh home initiates into remote → triggers detection (remote's row moves to
+    // needs_attention via markPeerReset). On buggy code fresh home ALSO false-activates;
+    // after the fix fresh home gets 409 and stays clean.
+    await initiatePeering(freshHome, adminIf.token, h.remote);
+
+    // One-click Re-peer on the SURVIVOR (remote): detection must have fired.
+    const rPeer = await getPeer(h.remote, adminR.token, freshHome.origin);
+    expect(rPeer).toBeTruthy();
+    expect(rPeer!.status).toBe('needs_attention');
+
+    // Reset remote's stale row, then re-initiate the handshake from remote.
+    await resetPeer(h.remote, adminR.token, rPeer!.id);
+    const rebuilt = await initiatePeering(h.remote, adminR.token, freshHome);
+
+    // GENUINE recovery: 200 + working secret in both directions + matching stored secrets.
+    expect(rebuilt.status).toBe(200);
+    expect(await s2sHealthy(h.remote, freshHome)).toBe(true);
+    expect(await s2sHealthy(freshHome, h.remote)).toBe(true);
+
+    const remoteInsp = openInspector(h.remote);
+    const homeInsp = openInspector(freshHome);
+    try {
+      const rSecret = remoteInsp.federationPeer(freshHome.origin)?.hmacSecret;
+      const iSecret = homeInsp.federationPeer(h.remote.origin)?.hmacSecret;
+      expect(rSecret).toBeTruthy();
+      expect(iSecret).toBeTruthy();
+      expect(rSecret).toBe(iSecret);
+    } finally {
+      remoteInsp.close();
+      homeInsp.close();
+    }
+  }, 60_000);
+});