diff --git a/docs/systems/api.md b/docs/systems/api.md
index adcbc9b8..bb15eaf3 100644
--- a/docs/systems/api.md
+++ b/docs/systems/api.md
@@ -14,7 +14,7 @@ POST /auth/login             { username, password } → { token, user }
 POST /auth/attach-proof      (JWT, rate-limited 5/15min)  { targetDomain } → { token }   (AttachProofResponse)
 ```
 
-**`POST /auth/attach-proof`** — JWT-authenticated. Mints a one-time 256-bit token (`randomBytes(32).toString('hex')`) for the logged-in **native** user, stored in `federation_attach_proofs` bound to `{ homeUserId, targetDomain, expiresAt = now+60s }`; expired/used rows are janitored on each mint. The token is handed to the peer named by `targetDomain`, which redeems it via `POST /federation/verify-attach-proof` to re-attach the caller's detached account there. See `federation.md` "S2S Detached-Account Re-Attach Proof" and re-attach spec §3.1.
+**`POST /auth/attach-proof`** — JWT-authenticated. Mints a one-time 256-bit token (`randomBytes(32).toString('hex')`) for the logged-in **native** user, stored in `federation_attach_proofs` bound to `{ homeUserId, targetDomain, expiresAt = now+60s }`; expired rows are janitored on each mint (the delete targets `expires_at < now`; a used-but-unexpired row lingers until it expires). The token is handed to the peer named by `targetDomain`, which redeems it via `POST /federation/verify-attach-proof` to re-attach the caller's detached account there. See `federation.md` "S2S Detached-Account Re-Attach Proof" and re-attach spec §3.1.
 
 **`POST /auth/login`** — request/response shape unchanged, but two internal controls from instance-epoch self-healing gate the flow: (1) an account with `federationHomeOrphaned = 1` (home instance factory-reset) is **detached** — a sovereign local account whose local password hash is the sole authority; it logs in normally with that local password (the detach pivot removed the old pre-verification freeze), and the flag's only login effect is to permanently disable self-heal (step 7); (2) for non-detached federated accounts, the password self-heal runs an **epoch guard** — it re-hashes the stale local password only if the home instance's authenticated epoch (`fetchPeerEpoch`) matches the trusted baseline, failing closed when the epoch differs or can't be determined. A detached account can be re-bound to the owner's new home identity via `POST /users/@me/reattach` (re-attach spec §3.2), which clears the flag and re-enables normal federated semantics. No wire-shape change. See `auth.md` §4.
 
diff --git a/packages/server/src/routes/auth.attachProof.test.ts b/packages/server/src/routes/auth.attachProof.test.ts
index 2e8a1d0c..7b5f09da 100644
--- a/packages/server/src/routes/auth.attachProof.test.ts
+++ b/packages/server/src/routes/auth.attachProof.test.ts
@@ -112,6 +112,19 @@ describe('POST /api/auth/attach-proof', () => {
     expect(res.statusCode).toBe(400);
   });
 
+  it('rejects a targetDomain that normalizes to empty and inserts no row', async () => {
+    // "https://" passes the pre-normalization length check but collapses to ""
+    // after protocol/slash stripping — must 400, never persist an inert row.
+    const res = await app.inject({
+      method: 'POST',
+      url: '/api/auth/attach-proof',
+      headers: { authorization: `Bearer ${signJwt({ userId: 'native-1', username: 'youruser' })}` },
+      payload: { targetDomain: 'https://' },
+    });
+    expect(res.statusCode).toBe(400);
+    expect(testDb.select().from(schema.federationAttachProofs).all()).toHaveLength(0);
+  });
+
   it('rejects unauthenticated requests', async () => {
     const res = await app.inject({ method: 'POST', url: '/api/auth/attach-proof', payload: { targetDomain: 'nova.ddns.net' } });
     expect(res.statusCode).toBe(401);
diff --git a/packages/server/src/routes/auth.ts b/packages/server/src/routes/auth.ts
index dfb426ec..732fa6e1 100644
--- a/packages/server/src/routes/auth.ts
+++ b/packages/server/src/routes/auth.ts
@@ -504,6 +504,12 @@ export async function authRoutes(app: FastifyInstance): Promise<void> {
       return reply.code(400).send({ error: 'targetDomain is required (string)', statusCode: 400 });
     }
     const targetDomain = rawTarget.trim().toLowerCase().replace(/^https?:\/\//, '').replace(/\/+$/, '');
+    // Re-check emptiness AFTER normalization: inputs like "https://" or "/"
+    // pass the pre-normalization guard but collapse to "" — never persist an
+    // inert target_domain='' proof row.
+    if (targetDomain.length === 0) {
+      return reply.code(400).send({ error: 'targetDomain is required (string)', statusCode: 400 });
+    }
 
     // Native accounts only — a federated/replicated account has no authority
     // to mint proofs for this domain's identities.
diff --git a/packages/server/src/routes/federation.reattach.test.ts b/packages/server/src/routes/federation.reattach.test.ts
index 04287a86..2f96b166 100644
--- a/packages/server/src/routes/federation.reattach.test.ts
+++ b/packages/server/src/routes/federation.reattach.test.ts
@@ -226,6 +226,13 @@ describe('POST /api/users/@me/reattach — stub merge', () => {
     testDb.insert(schema.dmMessages).values({
       id: 'm-stub', dmChannelId: 'ch-1', userId: 'stub-new', content: 'from new incarnation', createdAt: 3,
     }).run();
+    // An attachment the stub uploaded onto its DM message — uploader_id is a
+    // plain text column (no FK), so it must be repointed explicitly or attribution
+    // dangles at the deleted stub's id.
+    testDb.insert(schema.attachments).values({
+      id: 'att-stub', dmMessageId: 'm-stub', uploaderId: 'stub-new',
+      filename: 'f.webp', originalName: 'f.webp', mimetype: 'image/webp', size: 100, createdAt: 3,
+    }).run();
     testDb.insert(schema.friends).values([
       { userId: 'alice', friendId: 'detached-1', createdAt: 1 },
       { userId: 'alice', friendId: 'stub-new', createdAt: 2 },
@@ -240,6 +247,9 @@ describe('POST /api/users/@me/reattach — stub merge', () => {
     // Message repointed.
     const msg = testDb.select().from(schema.dmMessages).where(eq(schema.dmMessages.id, 'm-stub')).get()!;
     expect(msg.userId).toBe('detached-1');
+    // Attachment attribution repointed off the deleted stub.
+    const att = testDb.select().from(schema.attachments).where(eq(schema.attachments.id, 'att-stub')).get()!;
+    expect(att.uploaderId).toBe('detached-1');
     // Membership deduped (detached row already a member).
     const members = testDb.select().from(schema.dmMembers).all().filter(m => m.dmChannelId === 'ch-1');
     expect(members.map(m => m.userId).sort()).toEqual(['alice', 'detached-1']);
diff --git a/packages/server/src/routes/federation.ts b/packages/server/src/routes/federation.ts
index 2a6b0323..d2f85862 100644
--- a/packages/server/src/routes/federation.ts
+++ b/packages/server/src/routes/federation.ts
@@ -2959,6 +2959,11 @@ export async function federationRoutes(app: FastifyInstance): Promise<void> {
         // dm_messages / messages (RESTRICT FK, no unique on user_id → straight repoint).
         rawDb.prepare(`UPDATE dm_messages SET user_id = ? WHERE user_id = ?`).run(targetId, stubId);
         rawDb.prepare(`UPDATE messages SET user_id = ? WHERE user_id = ?`).run(targetId, stubId);
+        // attachments.uploader_id (plain text column, NO FK, no unique → straight
+        // repoint). A replicated stub that uploaded a DM/channel attachment would
+        // otherwise leave uploader_id dangling at the deleted stub's id — broken
+        // attribution.
+        rawDb.prepare(`UPDATE attachments SET uploader_id = ? WHERE uploader_id = ?`).run(targetId, stubId);
         // dm_reactions (dedupe on dm_message_id+emoji per user).
         rawDb.prepare(`DELETE FROM dm_reactions WHERE user_id = ? AND EXISTS (SELECT 1 FROM dm_reactions r2 WHERE r2.user_id = ? AND r2.dm_message_id = dm_reactions.dm_message_id AND r2.emoji = dm_reactions.emoji)`).run(stubId, targetId);
         rawDb.prepare(`UPDATE dm_reactions SET user_id = ? WHERE user_id = ?`).run(targetId, stubId);
diff --git a/packages/server/src/utils/federationAttach.test.ts b/packages/server/src/utils/federationAttach.test.ts
index a76a45d0..e0e51c7c 100644
--- a/packages/server/src/utils/federationAttach.test.ts
+++ b/packages/server/src/utils/federationAttach.test.ts
@@ -37,6 +37,30 @@ describe('verifyAttachProofWithPeer', () => {
     expect(await verifyAttachProofWithPeer(PEER, 'a'.repeat(64))).toEqual({ valid: false });
   });
 
+  it('treats a PRESENT-but-INVALID signature as valid:false (signature must verify against the peer secret)', async () => {
+    // A 200 response with a well-formed signature header that was computed with
+    // the WRONG secret — it must NOT verify against the peer's real secret. This
+    // hardens the core "never trust unauthenticated bodies" gate: a malicious or
+    // misconfigured peer that returns valid:true with a bogus signature is rejected.
+    const wrongSignedResponse = (bodyObj: object): Response => {
+      const body = JSON.stringify(bodyObj);
+      const ts = Date.now();
+      const nonce = 'resp-nonce';
+      const sig = signRequest(body, 'c'.repeat(64) /* wrong secret */, ts, nonce);
+      return new Response(body, {
+        status: 200,
+        headers: {
+          'x-federation-signature': `sha256=${sig}`,
+          'x-federation-timestamp': String(ts),
+          'x-federation-nonce': nonce,
+        },
+      });
+    };
+    vi.stubGlobal('fetch', vi.fn(async () => wrongSignedResponse({ valid: true, homeUserId: 'h1', username: 'youruser' })));
+    const { verifyAttachProofWithPeer } = await import('./federationAttach.js');
+    expect(await verifyAttachProofWithPeer(PEER, 'a'.repeat(64))).toEqual({ valid: false });
+  });
+
   it('network error → valid:false', async () => {
     vi.stubGlobal('fetch', vi.fn(async () => { throw new Error('ECONNREFUSED'); }));
     const { verifyAttachProofWithPeer } = await import('./federationAttach.js');
@@ -56,9 +80,15 @@ describe('fetchHomeProfileByHomeId', () => {
     expect(result?.profile.avatar).toBe('a.webp');
   });
 
-  it('found:false or network error → null', async () => {
+  it('found:false → null', async () => {
     vi.stubGlobal('fetch', vi.fn(async () => new Response(JSON.stringify({ found: false }), { status: 200 })));
     const { fetchHomeProfileByHomeId } = await import('./federationAttach.js');
     expect(await fetchHomeProfileByHomeId(PEER, 'h1')).toBeNull();
   });
+
+  it('network error → null', async () => {
+    vi.stubGlobal('fetch', vi.fn(async () => { throw new Error('ECONNREFUSED'); }));
+    const { fetchHomeProfileByHomeId } = await import('./federationAttach.js');
+    expect(await fetchHomeProfileByHomeId(PEER, 'h1')).toBeNull();
+  });
 });
diff --git a/packages/web/src/components/modals/settingsPanels/AccountPanel.tsx b/packages/web/src/components/modals/settingsPanels/AccountPanel.tsx
index 084a0d29..434b45e9 100644
--- a/packages/web/src/components/modals/settingsPanels/AccountPanel.tsx
+++ b/packages/web/src/components/modals/settingsPanels/AccountPanel.tsx
@@ -90,7 +90,9 @@ export function AccountPanel() {
     const homeDomain = user.homeInstance.replace(/^https?:\/\//, '').replace(/\/+$/, '').toLowerCase();
     return instances.find(
       (i) => i.status === 'connected'
-        && i.origin.replace(/^https?:\/\//, '').replace(/\/+$/, '').toLowerCase() === homeDomain,
+        // Portless hostname — must agree with the server's extractDomain
+        // (new URL(origin).hostname) so a ported home instance still matches.
+        && new URL(i.origin).hostname.toLowerCase() === homeDomain,
     ) ?? null;
   }, [instances, user?.homeInstance]);
 
@@ -104,7 +106,8 @@ export function AccountPanel() {
     setReattachError(null);
     try {
       // Target domain = THIS instance (where the detached account lives).
-      const { token } = await homeConnection.api.auth.attachProof(window.location.host);
+      // Portless hostname to match the server's extractDomain contract.
+      const { token } = await homeConnection.api.auth.attachProof(window.location.hostname);
       const res = await api.users.reattach({ token });
       useAuthStore.getState().setUser(res.user);
       addToast(`Account re-linked with ${homeConnection.username}`, 'success', 3000);
diff --git a/packages/web/src/stores/instanceStore.autoReattach.test.ts b/packages/web/src/stores/instanceStore.autoReattach.test.ts
index ef2b25b9..d77ea06e 100644
--- a/packages/web/src/stores/instanceStore.autoReattach.test.ts
+++ b/packages/web/src/stores/instanceStore.autoReattach.test.ts
@@ -80,6 +80,38 @@ describe('maybeAutoReattach', () => {
     useInstanceStore.setState({ instances: [homeConn, detachedConn] });
     await maybeAutoReattach(detachedConn);
     expect((homeConn.api as unknown as { auth: { attachProof: ReturnType<typeof vi.fn> } }).auth.attachProof).not.toHaveBeenCalled();
+    expect((detachedConn.api as unknown as { users: { reattach: ReturnType<typeof vi.fn> } }).users.reattach).not.toHaveBeenCalled();
+  });
+
+  it('mints the PORTLESS target host for a ported instance origin (matches server extractDomain)', async () => {
+    // Both instances served on a non-443 port. The server binds/verifies the
+    // proof against extractDomain(peer.origin) = new URL(origin).hostname, which
+    // is portless — so the client must mint the portless host too, or the
+    // exchange 401s forever. homeInstance is stored bare (portless hostname).
+    const homeConn = makeInstance({
+      origin: 'https://orbit.test:8443',
+      username: 'youruser',
+      user: { id: 'new-home-1', username: 'youruser' } as User,
+    });
+    const attachProof = vi.fn().mockResolvedValue({ token: 'a'.repeat(64) });
+    (homeConn.api as unknown as { auth: { attachProof: typeof attachProof } }).auth.attachProof = attachProof;
+
+    const updatedUser = { id: 'detached-1', username: 'youruser@orbit.test', federationHomeOrphaned: false, homeInstance: 'orbit.test' } as User;
+    const reattach = vi.fn().mockResolvedValue({ success: true, user: updatedUser });
+    const detachedConn = makeInstance({
+      origin: 'https://nova.test:8443',
+      user: { id: 'detached-1', username: 'youruser@orbit.test', federationHomeOrphaned: true, homeInstance: 'orbit.test' } as User,
+    });
+    (detachedConn.api as unknown as { users: { reattach: typeof reattach } }).users.reattach = reattach;
+
+    useInstanceStore.setState({ instances: [homeConn, detachedConn] });
+    await maybeAutoReattach(detachedConn);
+
+    // Portless — 'nova.test', NOT 'nova.test:8443'.
+    expect(attachProof).toHaveBeenCalledWith('nova.test');
+    expect(reattach).toHaveBeenCalledWith({ token: 'a'.repeat(64) });
+    const stored = useInstanceStore.getState().instances.find(i => i.origin === 'https://nova.test:8443')!;
+    expect(stored.user.federationHomeOrphaned).toBe(false);
   });
 
   it('skips when the account is not detached', async () => {
diff --git a/packages/web/src/stores/instanceStore.ts b/packages/web/src/stores/instanceStore.ts
index 8afc90a1..266bd6cb 100644
--- a/packages/web/src/stores/instanceStore.ts
+++ b/packages/web/src/stores/instanceStore.ts
@@ -155,12 +155,12 @@ export async function maybeAutoReattach(instance: ConnectedInstance): Promise<vo
   const primaryUser = useAuthStore.getState().user;
   let homeApi: BackspaceApiClient | null = null;
   let homeUsername: string | null = null;
-  if (primaryUser && !primaryUser.homeInstance && window.location.host.toLowerCase() === homeDomain) {
+  if (primaryUser && !primaryUser.homeInstance && window.location.hostname.toLowerCase() === homeDomain) {
     homeApi = api;
     homeUsername = primaryUser.username;
   } else {
     const conn = useInstanceStore.getState().instances.find(
-      (i) => i.status === 'connected' && new URL(i.origin).host.toLowerCase() === homeDomain,
+      (i) => i.status === 'connected' && new URL(i.origin).hostname.toLowerCase() === homeDomain,
     );
     if (conn) {
       homeApi = conn.api;
@@ -175,7 +175,10 @@ export async function maybeAutoReattach(instance: ConnectedInstance): Promise<vo
   if (!detachedBase || detachedBase !== homeBase) return;
 
   try {
-    const targetHost = new URL(instance.origin).host;
+    // Portless hostname — must match the server's extractDomain(peer.origin)
+    // (new URL(origin).hostname) so the proof's targetDomain binds/verifies on
+    // a non-443 port too. .host would carry the port and 401 forever.
+    const targetHost = new URL(instance.origin).hostname;
     const { token } = await homeApi.auth.attachProof(targetHost);
     const res = await instance.api.users.reattach({ token });
     useInstanceStore.setState((state) => ({