fix(federation): include own instanceName in /peer/accept response body

Bidirectional handshake exchange. Today the responder learns the initiator's instance name from request body but the initiator never learns the responder's. Adding {instanceName} to the response body lets the initiator persist it on its side (next commit). Field is optional so older peers omitting it cause no ill effect.

packages/server/src/routes/federation.peerAccept.test.ts

@@ -227,3 +227,74 @@ describe('POST /api/federation/peer/accept — instance_name persistence', () =>
     expect(row?.instanceName).toBeNull();
   });
 });
+
+describe('POST /api/federation/peer/accept — response body carries instanceName', () => {
+  let app: FastifyInstance;
+
+  beforeEach(async () => {
+    sqlite = new Database(':memory:');
+    testDb = drizzle(sqlite, { schema });
+    applyMigrations(sqlite);
+    seedInstanceSettings('Local Backspace');
+    app = await buildApp();
+  });
+
+  it('returns our own instanceName in the response body on new-peer accept', async () => {
+    const response = await app.inject({
+      method: 'POST',
+      url: '/api/federation/peer/accept',
+      payload: {
+        sourceOrigin: 'https://remote.example',
+        hmacSecret: 'remote-secret',
+        instanceName: 'Remote Backspace',
+      },
+    });
+
+    expect(response.statusCode).toBe(200);
+    const body = response.json() as { accepted: boolean; instanceName?: string | null };
+    expect(body.accepted).toBe(true);
+    expect(body.instanceName).toBe('Local Backspace');
+  });
+
+  it('returns our instanceName on the active idempotent path too', async () => {
+    testDb.insert(schema.federationPeers).values({
+      id: 'peer-active',
+      origin: 'https://remote.example',
+      hmacSecret: 'existing-secret',
+      status: 'active',
+      instanceName: 'Original Name',
+      createdAt: Date.now(),
+    }).run();
+
+    const response = await app.inject({
+      method: 'POST',
+      url: '/api/federation/peer/accept',
+      payload: {
+        sourceOrigin: 'https://remote.example',
+        hmacSecret: 'remote-secret',
+        instanceName: 'Remote Backspace',
+      },
+    });
+
+    expect(response.statusCode).toBe(200);
+    const body = response.json() as { accepted: boolean; instanceName?: string | null };
+    expect(body.instanceName).toBe('Local Backspace');
+  });
+
+  it('returns instanceName: null when instanceSettings table is empty', async () => {
+    testDb.delete(schema.instanceSettings).run();
+
+    const response = await app.inject({
+      method: 'POST',
+      url: '/api/federation/peer/accept',
+      payload: {
+        sourceOrigin: 'https://remote.example',
+        hmacSecret: 'remote-secret',
+      },
+    });
+
+    expect(response.statusCode).toBe(200);
+    const body = response.json() as { accepted: boolean; instanceName?: string | null };
+    expect(body.instanceName).toBeNull();
+  });
+});

packages/server/src/routes/federation.ts

@@ -421,16 +421,22 @@ export async function federationRoutes(app: FastifyInstance): Promise<void> {
 
       const db = getDb();
 
+      const settings = db
+        .select({
+          instanceName: schema.instanceSettings.instanceName,
+          autoAcceptPeering: schema.instanceSettings.autoAcceptPeering,
+        })
+        .from(schema.instanceSettings)
+        .where(eq(schema.instanceSettings.id, 1))
+        .get();
+
+      const ourInstanceName = settings?.instanceName ?? null;
+      const autoAccept = settings?.autoAcceptPeering ?? 1;
+
       // ── autoAcceptPeering gate ──────────────────────────────────────────
       // When auto-accept is disabled, only allow incoming accept requests
       // that correspond to a local pending peer (i.e., a local admin
       // initiated the handshake). Unsolicited requests are rejected.
-      const settings = db
-        .select({ autoAcceptPeering: schema.instanceSettings.autoAcceptPeering })
-        .from(schema.instanceSettings)
-        .where(eq(schema.instanceSettings.id, 1))
-        .get();
-      const autoAccept = settings?.autoAcceptPeering ?? 1;
 
       if (autoAccept === 0) {
         // Check if the local admin already initiated or approved peering with this origin.
@@ -536,7 +542,7 @@ export async function federationRoutes(app: FastifyInstance): Promise<void> {
           // Legitimate recovery path: local admin clicks "Reset peering" →
           // row is deleted → remote's /peer/accept then lands on a
           // non-existent row and the normal handshake path runs.
-          return reply.code(200).send({ accepted: true });
+          return reply.code(200).send({ accepted: true, instanceName: ourInstanceName });
         }
         if (existing.status === 'revoked') {
           return reply.code(403).send({
@@ -570,7 +576,7 @@ export async function federationRoutes(app: FastifyInstance): Promise<void> {
             console.error('[federation] onPeerActivated from /peer/accept (rejected override) failed:', err)
           );
 
-          return reply.code(200).send({ accepted: true });
+          return reply.code(200).send({ accepted: true, instanceName: ourInstanceName });
         }
         if (existing.status === 'awaiting_approval') {
           // Remote admin approved — this is a fresh handshake from them.
@@ -597,7 +603,7 @@ export async function federationRoutes(app: FastifyInstance): Promise<void> {
             console.error('[federation] onPeerActivated from /peer/accept (awaiting_approval) failed:', err)
           );
 
-          return reply.code(200).send({ accepted: true });
+          return reply.code(200).send({ accepted: true, instanceName: ourInstanceName });
         }
         // Pending — update with new secret and activate
         db.update(schema.federationPeers)
@@ -615,7 +621,7 @@ export async function federationRoutes(app: FastifyInstance): Promise<void> {
           console.error('[federation] onPeerActivated from /peer/accept (pending) failed:', err)
         );
 
-        return reply.code(200).send({ accepted: true });
+        return reply.code(200).send({ accepted: true, instanceName: ourInstanceName });
       }
 
       // New peer — create and activate
@@ -635,7 +641,7 @@ export async function federationRoutes(app: FastifyInstance): Promise<void> {
         console.error('[federation] onPeerActivated from /peer/accept (new) failed:', err)
       );
 
-      return reply.code(200).send({ accepted: true });
+      return reply.code(200).send({ accepted: true, instanceName: ourInstanceName });
     },
   );