diff --git a/packages/server/src/ws/events.dmCallRelay.test.ts b/packages/server/src/ws/events.dmCallRelay.test.ts
new file mode 100644
index 00000000..0363d216
--- /dev/null
+++ b/packages/server/src/ws/events.dmCallRelay.test.ts
@@ -0,0 +1,165 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import Database from 'better-sqlite3';
+import { drizzle } from 'drizzle-orm/better-sqlite3';
+import fs from 'node:fs';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+import * as schema from '../db/schema.js';
+import { setWorkerId } from '../utils/snowflake.js';
+
+setWorkerId(1);
+
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+type TestDb = ReturnType<typeof drizzle<typeof schema>>;
+
+let testDb: TestDb;
+
+vi.mock('../db/index.js', () => ({
+  getDb: () => testDb,
+  schema,
+}));
+
+vi.mock('../utils/federationAuth.js', () => ({
+  getOurOrigin: () => 'https://local.example',
+  buildFederationHeaders: () => ({}),
+  generateHmacSecret: () => 'test-secret',
+}));
+
+// Mock sendCallRelay so tests can control relay-result per case.
+const sendCallRelayMock = vi.fn();
+vi.mock('../utils/federationOutbox.js', async () => {
+  const actual = await vi.importActual<typeof import('../utils/federationOutbox.js')>('../utils/federationOutbox.js');
+  return {
+    ...actual,
+    sendCallRelay: (...args: unknown[]) => sendCallRelayMock(...args),
+  };
+});
+
+function applyMigrations(db: Database.Database): void {
+  const migrationsDir = path.resolve(__dirname, '../../drizzle');
+  const files = fs.readdirSync(migrationsDir).filter(f => f.endsWith('.sql')).sort();
+  for (const f of files) {
+    const sql = fs.readFileSync(path.join(migrationsDir, f), 'utf8');
+    const statements = sql.split(/-->\s*statement-breakpoint/);
+    for (const stmt of statements) {
+      const clean = stmt.trim();
+      if (clean) db.exec(clean);
+    }
+  }
+}
+
+function seedPeerLabel(origin: string, instanceName: string): void {
+  testDb.insert(schema.federationPeers).values({
+    id: `peer-${origin}`,
+    origin,
+    hmacSecret: 'secret',
+    status: 'active',
+    instanceName,
+    lastSyncedAt: 0,
+    createdAt: Date.now(),
+  }).run();
+}
+
+function seedLocalUser(id: string, homeUserId: string | null): void {
+  testDb.insert(schema.users).values({
+    id,
+    username: id,
+    passwordHash: 'test',
+    homeUserId,
+    homeInstance: null,
+    createdAt: Date.now(),
+  }).run();
+}
+
+async function importSUT() {
+  // Late import so the module picks up the mocked dependencies.
+  return await import('./events.js');
+}
+
+async function importManager() {
+  const mod = await import('./handler.js');
+  return mod.connectionManager;
+}
+
+type FedCallEntry = import('./handler.js').FederatedCallEntry;
+
+function makeFedCall(partial: Partial<FedCallEntry> = {}): FedCallEntry {
+  return {
+    dmChannelId: 'dm-1',
+    federatedId: `fed-${Math.random().toString(36).slice(2, 10)}`,
+    callerId: 'caller-user',
+    callerHomeUserId: 'caller@pi',
+    federatedCallHost: 'https://pi.example',
+    livekitUrl: 'wss://pi.example/lk',
+    tokens: new Map([['acceptor@vm', 'token']]),
+    ringedUserIds: ['acceptor-user'],
+    state: 'ringing',
+    startedAt: Date.now(),
+    ...partial,
+  };
+}
+
+beforeEach(() => {
+  const sqlite = new Database(':memory:');
+  testDb = drizzle(sqlite, { schema });
+  applyMigrations(sqlite);
+  seedPeerLabel('https://pi.example', 'Pi-Instance');
+  seedLocalUser('acceptor-user', 'acceptor@vm');
+  seedLocalUser('caller-user', 'caller@pi');
+  sendCallRelayMock.mockReset();
+});
+
+afterEach(() => {
+  vi.restoreAllMocks();
+});
+
+describe('handleDmCallAccept Path-2 relay failure', () => {
+  it('emits dm_call_undeliverable { phase:"accept", terminal:true } and clears the fedCall when the relay fails', async () => {
+    const { handleDmCallAcceptForTest } = await importSUT();
+    const connectionManager = await importManager();
+
+    const fedCall = makeFedCall();
+    connectionManager.createFederatedCall(fedCall);
+    const sendToUsersSpy = vi.spyOn(connectionManager, 'sendToFederatedCallUsers');
+    sendCallRelayMock.mockResolvedValue({ ok: false, reason: 'peer_transient_failure', error: 'timeout' });
+
+    await handleDmCallAcceptForTest(
+      { federatedCallId: fedCall.federatedId },
+      fedCall.ringedUserIds[0]!,
+      {} as never,
+    );
+
+    expect(connectionManager.getFederatedCall(fedCall.federatedId)).toBeUndefined();
+    const calls = sendToUsersSpy.mock.calls.filter(([, ev]) =>
+      (ev as { type: string }).type === 'dm_call_undeliverable',
+    );
+    expect(calls).toHaveLength(1);
+    const undeliverable = calls[0]![1] as { phase: string; terminal: boolean; failures: unknown[] };
+    expect(undeliverable.phase).toBe('accept');
+    expect(undeliverable.terminal).toBe(true);
+    expect(undeliverable.failures).toHaveLength(1);
+  });
+
+  it('does not emit undeliverable on relay success', async () => {
+    const { handleDmCallAcceptForTest } = await importSUT();
+    const connectionManager = await importManager();
+
+    const fedCall = makeFedCall();
+    connectionManager.createFederatedCall(fedCall);
+    const sendToUsersSpy = vi.spyOn(connectionManager, 'sendToFederatedCallUsers');
+    sendCallRelayMock.mockResolvedValue({ ok: true });
+
+    await handleDmCallAcceptForTest(
+      { federatedCallId: fedCall.federatedId },
+      fedCall.ringedUserIds[0]!,
+      {} as never,
+    );
+
+    const undelivCalls = sendToUsersSpy.mock.calls.filter(([, ev]) =>
+      (ev as { type: string }).type === 'dm_call_undeliverable',
+    );
+    expect(undelivCalls).toHaveLength(0);
+    expect(connectionManager.getFederatedCall(fedCall.federatedId)?.state).toBe('active');
+    connectionManager.clearFederatedCall(fedCall.federatedId);
+  });
+});
diff --git a/packages/server/src/ws/events.ts b/packages/server/src/ws/events.ts
index 1f483792..ba281890 100644
--- a/packages/server/src/ws/events.ts
+++ b/packages/server/src/ws/events.ts
@@ -196,7 +196,9 @@ export function handleClientEvent(
       handleDmCallStart(event, userId, username, ws);
       break;
     case 'dm_call_accept':
-      handleDmCallAccept(event, userId, ws);
+      handleDmCallAccept(event, userId, ws).catch(err =>
+        console.error('[ws] handleDmCallAccept error:', err),
+      );
       break;
     case 'dm_call_reject':
       handleDmCallReject(event, userId);
@@ -1442,7 +1444,7 @@ function handleDmCallStart(event: Record<string, unknown>, userId: string, usern
     .catch(err => console.error('[federation] sendFederatedCallStart error:', err));
 }
 
-function handleDmCallAccept(event: Record<string, unknown>, userId: string, ws: WebSocket): void {
+async function handleDmCallAccept(event: Record<string, unknown>, userId: string, ws: WebSocket): Promise<void> {
   let dmChannelId = (event.dmChannelId as string) || null;
   const federatedCallId = (event.federatedCallId as string) || null;
   if (!dmChannelId && !federatedCallId) {
@@ -1520,6 +1522,8 @@ function handleDmCallAccept(event: Record<string, unknown>, userId: string, ws:
       : undefined;
 
   if (fedCall) {
+    // Optimistic transition so the acceptor's client flips to active immediately.
+    // Rolled back below if the relay to host fails.
     connectionManager.activateFederatedCall(fedCall.federatedId);
     connectionManager.sendToFederatedCallUsers(fedCall.federatedId, {
       type: 'dm_call_accepted',
@@ -1534,7 +1538,7 @@ function handleDmCallAccept(event: Record<string, unknown>, userId: string, ws:
       .get();
     const homeUserId = user?.homeUserId || userId;
 
-    sendCallRelay(fedCall.federatedCallHost, [{
+    const result = await sendCallRelay(fedCall.federatedCallHost, [{
       eventType: 'dm_call_accept',
       messageId: generateSnowflake(),
       encryptionVersion: 0,
@@ -1543,7 +1547,21 @@ function handleDmCallAccept(event: Record<string, unknown>, userId: string, ws:
       call: {
         acceptor: { homeUserId, homeInstance: getOurOrigin() },
       },
-    }]).catch(err => console.error('[federation] Failed to send dm_call_accept:', err));
+    }]);
+
+    if (!result.ok) {
+      console.error(`[federation] dm_call_accept relay to ${fedCall.federatedCallHost} failed (${result.reason}): ${result.error}`);
+      const failure = buildFailureFromResult(result, fedCall.federatedCallHost, db);
+      connectionManager.sendToFederatedCallUsers(fedCall.federatedId, {
+        type: 'dm_call_undeliverable',
+        dmChannelId: fedCall.dmChannelId,
+        federatedCallId: fedCall.federatedId,
+        terminal: true,
+        phase: 'accept',
+        failures: [failure],
+      });
+      connectionManager.clearFederatedCall(fedCall.federatedId);
+    }
     return;
   }
 
@@ -2333,3 +2351,7 @@ function handleVoiceDisconnect(event: Record<string, unknown>, userId: string):
     channelId,
   });
 }
+
+// ─── Test-only exports ──────────────────────────────────────────────────────
+/** Direct export for unit tests — do not use in production code paths. */
+export const handleDmCallAcceptForTest = handleDmCallAccept;