diff --git a/iios-0.0.0.tgz b/iios-0.0.0.tgz
new file mode 100644
index 0000000..970695d
Binary files /dev/null and b/iios-0.0.0.tgz differ
diff --git a/packages/iios-messaging-ui/insignia-iios-messaging-ui-0.1.0.tgz b/packages/iios-messaging-ui/insignia-iios-messaging-ui-0.1.0.tgz
index c2ff680..9d33aca 100644
Binary files a/packages/iios-messaging-ui/insignia-iios-messaging-ui-0.1.0.tgz and b/packages/iios-messaging-ui/insignia-iios-messaging-ui-0.1.0.tgz differ
diff --git a/packages/iios-messaging-ui/src/adapters/mock-inbox.ts b/packages/iios-messaging-ui/src/adapters/mock-inbox.ts
index fcee29b..c2603e4 100644
--- a/packages/iios-messaging-ui/src/adapters/mock-inbox.ts
+++ b/packages/iios-messaging-ui/src/adapters/mock-inbox.ts
@@ -1,5 +1,5 @@
 import type { InboxAdapter } from '../inbox/adapter';
-import type { InboxItem, InboxState, MailMessage, MailPerson } from '../inbox/types';
+import type { InboxItem, InboxState, MailAttachment, MailMessage, MailPerson } from '../inbox/types';
 
 const PEOPLE: MailPerson[] = [
   { id: 'pp_sofia', name: 'Sofia Ramirez', kind: 'staff' },
@@ -79,26 +79,31 @@ export class MockInboxAdapter implements InboxAdapter {
     return [...(this.threads.get(threadId)?.messages ?? [])];
   }
 
-  async mailReply(threadId: string, content: string): Promise<void> {
+  async mailReply(threadId: string, content: string, attachment?: MailAttachment): Promise<void> {
     const t = this.threads.get(threadId);
-    if (t) t.messages = [...t.messages, { id: `r_${this.seq++}`, actorId: 'me', kind: 'MESSAGE', at: this.now(), html: null, text: content, attachment: null }];
+    if (t) t.messages = [...t.messages, { id: `r_${this.seq++}`, actorId: 'me', kind: 'MESSAGE', at: this.now(), html: null, text: content || null, attachment: attachment ?? null }];
+  }
+
+  async uploadAttachment(file: File): Promise<MailAttachment> {
+    return { contentRef: `mock/${this.seq++}`, mimeType: file.type || 'application/octet-stream', sizeBytes: file.size, filename: file.name };
   }
 
   async directory(): Promise<MailPerson[]> {
     return [...PEOPLE];
   }
 
-  async composeInternal(recipientUserId: string, subject: string, text: string): Promise<void> {
+  async composeInternal(recipientUserId: string, subject: string, text: string, attachments?: MailAttachment[]): Promise<void> {
     const threadId = `mt_${this.seq++}`;
-    this.threads.set(threadId, { subject, messages: [{ id: `m_${this.seq++}`, actorId: 'me', kind: 'EMAIL', at: this.now(), html: `<p>${text}</p>`, text, attachment: null }] });
+    this.threads.set(threadId, { subject, messages: [{ id: `m_${this.seq++}`, actorId: 'me', kind: 'EMAIL', at: this.now(), html: `<p>${text}</p>`, text, attachment: attachments?.[0] ?? null }] });
     this.mailFold.unshift(threadId);
     void recipientUserId;
   }
 
-  async composeExternal(target: string, subject: string, text: string): Promise<void> {
+  async composeExternal(target: string, subject: string, text: string, attachments?: MailAttachment[]): Promise<void> {
     // A mock external send has no in-app thread — no-op beyond acknowledging.
     void target;
     void subject;
     void text;
+    void attachments;
   }
 }
diff --git a/packages/iios-messaging-ui/src/inbox/adapter.ts b/packages/iios-messaging-ui/src/inbox/adapter.ts
index ec976f2..dec547e 100644
--- a/packages/iios-messaging-ui/src/inbox/adapter.ts
+++ b/packages/iios-messaging-ui/src/inbox/adapter.ts
@@ -1,4 +1,4 @@
-import type { InboxItem, InboxState, MailMessage, MailPerson } from './types';
+import type { MailAttachment, InboxItem, InboxState, MailMessage, MailPerson } from './types';
 
 /**
  * The inbox seam. A host implements this; the SDK renders it. Mirrors MessagingAdapter's philosophy:
@@ -15,14 +15,18 @@ export interface InboxAdapter {
   /** Messages of one mail thread (HTML + text parts) for the reader. */
   mailHistory(threadId: string): Promise<MailMessage[]>;
 
-  /** Reply into an existing mail thread. */
-  mailReply(threadId: string, content: string): Promise<void>;
+  /** Reply into an existing mail thread, optionally with one attachment. */
+  mailReply(threadId: string, content: string, attachment?: MailAttachment): Promise<void>;
+
+  // ── Attachments (optional) — absent hides the attach affordance ──
+  /** Upload a file to storage, returning a reference to send with a reply/compose. */
+  uploadAttachment?(file: File): Promise<MailAttachment>;
 
   // ── Compose (optional) — absent hides the "New message" affordance ──
   /** People you can compose an in-app message to. */
   directory?(): Promise<MailPerson[]>;
   /** App-to-app mail (no SMTP) to a registered user's in-app inbox. */
-  composeInternal?(recipientUserId: string, subject: string, text: string): Promise<void>;
+  composeInternal?(recipientUserId: string, subject: string, text: string, attachments?: MailAttachment[]): Promise<void>;
   /** External email (SMTP) to an address. */
-  composeExternal?(target: string, subject: string, text: string): Promise<void>;
+  composeExternal?(target: string, subject: string, text: string, attachments?: MailAttachment[]): Promise<void>;
 }
diff --git a/packages/iios-messaging-ui/src/inbox/hooks.ts b/packages/iios-messaging-ui/src/inbox/hooks.ts
index 8a84464..b9ab6a2 100644
--- a/packages/iios-messaging-ui/src/inbox/hooks.ts
+++ b/packages/iios-messaging-ui/src/inbox/hooks.ts
@@ -1,6 +1,6 @@
 import { useCallback, useEffect, useState } from 'react';
 import { useInboxAdapter } from './provider';
-import type { InboxItem, InboxState, MailMessage, MailPerson } from './types';
+import type { InboxItem, InboxState, MailAttachment, MailMessage, MailPerson } from './types';
 
 export interface InboxData {
   items: InboxItem[];
@@ -57,7 +57,9 @@ export interface MailThreadState {
   messages: MailMessage[];
   loading: boolean;
   error: string | null;
-  reply: (content: string) => Promise<void>;
+  reply: (content: string, attachment?: MailAttachment) => Promise<void>;
+  canAttach: boolean;
+  upload: (file: File) => Promise<MailAttachment>;
   refetch: () => void;
 }
 
@@ -97,22 +99,31 @@ export function useMailThread(threadId: string | null): MailThreadState {
 
   const refetch = useCallback(() => setNonce((n) => n + 1), []);
   const reply = useCallback(
-    async (content: string) => {
+    async (content: string, attachment?: MailAttachment) => {
       if (!threadId) return;
-      await adapter.mailReply(threadId, content);
+      await adapter.mailReply(threadId, content, attachment);
       setNonce((n) => n + 1);
     },
     [adapter, threadId],
   );
+  const upload = useCallback(
+    async (file: File) => {
+      if (!adapter.uploadAttachment) throw new Error('attachments are not supported by this adapter');
+      return adapter.uploadAttachment(file);
+    },
+    [adapter],
+  );
 
-  return { messages, loading, error, reply, refetch };
+  return { messages, loading, error, reply, canAttach: typeof adapter.uploadAttachment === 'function', upload, refetch };
 }
 
 export interface ComposeState {
   supported: boolean;
   directory: MailPerson[];
-  sendInternal: (recipientUserId: string, subject: string, text: string) => Promise<void>;
-  sendExternal: (target: string, subject: string, text: string) => Promise<void>;
+  sendInternal: (recipientUserId: string, subject: string, text: string, attachments?: MailAttachment[]) => Promise<void>;
+  sendExternal: (target: string, subject: string, text: string, attachments?: MailAttachment[]) => Promise<void>;
+  canAttach: boolean;
+  upload: (file: File) => Promise<MailAttachment>;
 }
 
 /** Compose a new message — in-app (to a person) or external (to an email). */
@@ -138,19 +149,26 @@ export function useCompose(): ComposeState {
   }, [adapter]);
 
   const sendInternal = useCallback(
-    async (recipientUserId: string, subject: string, text: string) => {
+    async (recipientUserId: string, subject: string, text: string, attachments?: MailAttachment[]) => {
       if (!adapter.composeInternal) throw new Error('compose is not supported by this adapter');
-      await adapter.composeInternal(recipientUserId, subject, text);
+      await adapter.composeInternal(recipientUserId, subject, text, attachments);
     },
     [adapter],
   );
   const sendExternal = useCallback(
-    async (target: string, subject: string, text: string) => {
+    async (target: string, subject: string, text: string, attachments?: MailAttachment[]) => {
       if (!adapter.composeExternal) throw new Error('compose is not supported by this adapter');
-      await adapter.composeExternal(target, subject, text);
+      await adapter.composeExternal(target, subject, text, attachments);
+    },
+    [adapter],
+  );
+  const upload = useCallback(
+    async (file: File) => {
+      if (!adapter.uploadAttachment) throw new Error('attachments are not supported by this adapter');
+      return adapter.uploadAttachment(file);
     },
     [adapter],
   );
 
-  return { supported, directory, sendInternal, sendExternal };
+  return { supported, directory, sendInternal, sendExternal, canAttach: typeof adapter.uploadAttachment === 'function', upload };
 }
diff --git a/packages/iios-messaging-ui/src/inbox/inbox.test.tsx b/packages/iios-messaging-ui/src/inbox/inbox.test.tsx
index 88318d8..a9193c7 100644
--- a/packages/iios-messaging-ui/src/inbox/inbox.test.tsx
+++ b/packages/iios-messaging-ui/src/inbox/inbox.test.tsx
@@ -34,6 +34,24 @@ describe('mock inbox adapter', () => {
     await a.mailReply('mt_welcome', 'thanks!');
     expect((await a.mailHistory('mt_welcome')).some((m) => m.text === 'thanks!')).toBe(true);
   });
+
+  it('reply carries an uploaded attachment', async () => {
+    const a = new MockInboxAdapter();
+    const ref = await a.uploadAttachment(new File(['x'], 'plan.pdf', { type: 'application/pdf' }));
+    expect(ref).toMatchObject({ filename: 'plan.pdf', mimeType: 'application/pdf' });
+    await a.mailReply('mt_welcome', '', ref);
+    const last = (await a.mailHistory('mt_welcome')).at(-1)!;
+    expect(last.attachment?.filename).toBe('plan.pdf');
+  });
+
+  it('composeInternal carries a first attachment onto the new thread', async () => {
+    const a = new MockInboxAdapter();
+    const ref = await a.uploadAttachment(new File(['x'], 'quote.png', { type: 'image/png' }));
+    await a.composeInternal('pp_sofia', 'Quote', 'see attached', [ref]);
+    const open = await a.listInbox('OPEN');
+    const row = open.find((i) => i.title === 'Quote')!;
+    expect((await a.mailHistory(row.threadId!)).at(-1)?.attachment?.filename).toBe('quote.png');
+  });
 });
 
 describe('<Inbox /> (rendered)', () => {
@@ -55,6 +73,17 @@ describe('<Inbox /> (rendered)', () => {
     await waitFor(() => expect(screen.getByText('got it')).toBeTruthy());
   });
 
+  it('attaches a file into a mail reply', async () => {
+    mount();
+    fireEvent.click(await screen.findByText('Welcome to the Founders Club'));
+    const file = new File(['data'], 'roof.pdf', { type: 'application/pdf' });
+    fireEvent.change(await screen.findByLabelText('Attach file'), { target: { files: [file] } });
+    // The pending chip shows the file, then Reply sends it.
+    await screen.findByText(/roof\.pdf/);
+    fireEvent.click(screen.getByText('Reply'));
+    await waitFor(() => expect(screen.getAllByText(/roof\.pdf/).length).toBeGreaterThan(0));
+  });
+
   it('composes an in-app message and it shows in the inbox', async () => {
     mount();
     fireEvent.click(await screen.findByText('New message'));
diff --git a/packages/iios-messaging-ui/src/inbox/inbox.tsx b/packages/iios-messaging-ui/src/inbox/inbox.tsx
index 4f78892..213e75f 100644
--- a/packages/iios-messaging-ui/src/inbox/inbox.tsx
+++ b/packages/iios-messaging-ui/src/inbox/inbox.tsx
@@ -1,6 +1,13 @@
-import { useEffect, useState, type FormEvent } from 'react';
+import { useEffect, useRef, useState, type FormEvent } from 'react';
 import { useCompose, useInbox, useMailThread } from './hooks';
-import type { InboxItem, InboxState, MailPerson } from './types';
+import type { InboxItem, InboxState, MailAttachment, MailPerson } from './types';
+
+const fmtBytes = (n: number): string => {
+  if (!n) return '';
+  if (n < 1024) return `${n} B`;
+  if (n < 1024 * 1024) return `${Math.round(n / 1024)} KB`;
+  return `${(n / (1024 * 1024)).toFixed(1)} MB`;
+};
 
 const FILTERS: { value: InboxState; label: string }[] = [
   { value: 'OPEN', label: 'Open' },
@@ -109,20 +116,42 @@ function Detail({ item, onTransition }: { item: InboxItem; onTransition: (state:
 
 /** Read a mail thread (HTML in a sandboxed iframe) + reply. */
 export function MailReader({ threadId, subject }: { threadId: string; subject: string }) {
-  const { messages, loading, error, reply } = useMailThread(threadId);
+  const { messages, loading, error, reply, canAttach, upload } = useMailThread(threadId);
   const [draft, setDraft] = useState('');
   const [sending, setSending] = useState(false);
+  const [pending, setPending] = useState<MailAttachment | null>(null);
+  const [attaching, setAttaching] = useState(false);
+  const [attachErr, setAttachErr] = useState<string | null>(null);
+  const fileRef = useRef<HTMLInputElement>(null);
+
+  async function pick(e: React.ChangeEvent<HTMLInputElement>): Promise<void> {
+    const file = e.target.files?.[0];
+    e.target.value = '';
+    if (!file) return;
+    setAttaching(true);
+    setAttachErr(null);
+    try {
+      setPending(await upload(file));
+    } catch (err) {
+      setAttachErr(err instanceof Error ? err.message : String(err));
+    } finally {
+      setAttaching(false);
+    }
+  }
 
   async function submit(e: FormEvent): Promise<void> {
     e.preventDefault();
     const text = draft.trim();
-    if (!text || sending) return;
+    if ((!text && !pending) || sending) return;
+    const att = pending;
     setDraft('');
+    setPending(null);
     setSending(true);
     try {
-      await reply(text);
+      await reply(text, att ?? undefined);
     } catch {
       setDraft(text);
+      setPending(att);
     } finally {
       setSending(false);
     }
@@ -142,16 +171,34 @@ export function MailReader({ threadId, subject }: { threadId: string; subject: s
             </div>
             {m.html ? (
               <iframe sandbox="" srcDoc={m.html} title="mail body" className="miu-mail-frame" />
-            ) : (
+            ) : m.text ? (
               <div className="miu-mail-text">{m.text}</div>
-            )}
+            ) : null}
+            {m.attachment ? (
+              <span className="miu-attach-chip">📎 {m.attachment.filename ?? 'attachment'}{m.attachment.sizeBytes ? ` · ${fmtBytes(m.attachment.sizeBytes)}` : ''}</span>
+            ) : null}
           </article>
         ))}
       </div>
       <form className="miu-composer" onSubmit={submit}>
+        {attachErr ? <div className="miu-empty miu-error">{attachErr}</div> : null}
+        {pending ? (
+          <div className="miu-attach-pending">
+            <span className="miu-attach-chip">📎 {pending.filename ?? 'attachment'}{pending.sizeBytes ? ` · ${fmtBytes(pending.sizeBytes)}` : ''}</span>
+            <button type="button" className="miu-attach-x" onClick={() => setPending(null)} aria-label="Remove attachment">✕</button>
+          </div>
+        ) : null}
         <div className="miu-composer-row">
+          {canAttach ? (
+            <>
+              <input ref={fileRef} type="file" hidden onChange={pick} aria-label="Attach file" />
+              <button type="button" className="miu-attach-btn" onClick={() => fileRef.current?.click()} disabled={attaching || !!pending} title="Attach a file" aria-label="Attach a file">
+                {attaching ? '…' : '📎'}
+              </button>
+            </>
+          ) : null}
           <input className="miu-input" value={draft} onChange={(e) => setDraft(e.target.value)} placeholder="Reply…" aria-label="Reply" />
-          <button type="submit" className="miu-send" disabled={!draft.trim() || sending}>Reply</button>
+          <button type="submit" className="miu-send" disabled={(!draft.trim() && !pending) || sending}>Reply</button>
         </div>
       </form>
     </div>
@@ -167,17 +214,37 @@ function ComposeModal({ onClose, onSent }: { onClose: () => void; onSent: () =>
   const [q, setQ] = useState('');
   const [busy, setBusy] = useState(false);
   const [err, setErr] = useState<string | null>(null);
+  const [attachments, setAttachments] = useState<MailAttachment[]>([]);
+  const [attaching, setAttaching] = useState(false);
+  const fileRef = useRef<HTMLInputElement>(null);
 
   const filtered = compose.directory.filter((p) => p.name.toLowerCase().includes(q.trim().toLowerCase()));
-  const canSend = !!recipient && !!subject.trim() && !!body.trim() && !busy;
+  const canSend = !!recipient && !!subject.trim() && (!!body.trim() || attachments.length > 0) && !busy && !attaching;
+
+  async function pick(e: React.ChangeEvent<HTMLInputElement>): Promise<void> {
+    const file = e.target.files?.[0];
+    e.target.value = '';
+    if (!file || attachments.length >= 10) return;
+    setAttaching(true);
+    setErr(null);
+    try {
+      const ref = await compose.upload(file);
+      setAttachments((a) => [...a, ref]);
+    } catch (e2) {
+      setErr(e2 instanceof Error ? e2.message : String(e2));
+    } finally {
+      setAttaching(false);
+    }
+  }
 
   async function send(): Promise<void> {
     if (!canSend) return;
     setBusy(true);
     setErr(null);
+    const atts = attachments.length > 0 ? attachments : undefined;
     try {
-      if (mode === 'internal') await compose.sendInternal(recipient, subject.trim(), body.trim());
-      else await compose.sendExternal(recipient.trim(), subject.trim(), body.trim());
+      if (mode === 'internal') await compose.sendInternal(recipient, subject.trim(), body.trim(), atts);
+      else await compose.sendExternal(recipient.trim(), subject.trim(), body.trim(), atts);
       onSent();
     } catch (e) {
       setErr(e instanceof Error ? e.message : String(e));
@@ -229,6 +296,23 @@ function ComposeModal({ onClose, onSent }: { onClose: () => void; onSent: () =>
             <span className="miu-field-lbl">Message</span>
             <textarea className="miu-input miu-textarea" value={body} onChange={(e) => setBody(e.target.value)} placeholder="Write your message…" rows={5} aria-label="Message body" />
           </div>
+          {compose.canAttach ? (
+            <div className="miu-field">
+              <span className="miu-field-lbl">Attachments</span>
+              <div className="miu-attach-list">
+                {attachments.map((a, i) => (
+                  <span key={`${a.contentRef}-${i}`} className="miu-attach-pending">
+                    <span className="miu-attach-chip">📎 {a.filename ?? 'attachment'}{a.sizeBytes ? ` · ${fmtBytes(a.sizeBytes)}` : ''}</span>
+                    <button type="button" className="miu-attach-x" onClick={() => setAttachments((prev) => prev.filter((_, j) => j !== i))} aria-label="Remove attachment">✕</button>
+                  </span>
+                ))}
+                <input ref={fileRef} type="file" hidden onChange={pick} aria-label="Attach file" />
+                <button type="button" className="miu-tab" onClick={() => fileRef.current?.click()} disabled={attaching || attachments.length >= 10}>
+                  {attaching ? 'Uploading…' : '📎 Attach'}
+                </button>
+              </div>
+            </div>
+          ) : null}
           {err ? <div className="miu-empty miu-error">{err}</div> : null}
         </div>
         <div className="miu-modal-foot">
diff --git a/packages/iios-messaging-ui/src/styles.css b/packages/iios-messaging-ui/src/styles.css
index a2bae8e..333cad7 100644
--- a/packages/iios-messaging-ui/src/styles.css
+++ b/packages/iios-messaging-ui/src/styles.css
@@ -335,6 +335,46 @@
   padding: 0;
   line-height: 1;
 }
+
+/* inbox mail attachments */
+.miu-attach-chip {
+  display: inline-flex;
+  align-items: center;
+  gap: 6px;
+  padding: 4px 10px;
+  border-radius: 999px;
+  border: 1px solid var(--miu-border);
+  background: var(--miu-panel-2);
+  color: var(--miu-text);
+  font-size: 12.5px;
+  max-width: 100%;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+.miu-mail-msg .miu-attach-chip {
+  margin-top: 6px;
+}
+.miu-attach-pending {
+  display: inline-flex;
+  align-items: center;
+  gap: 6px;
+}
+.miu-attach-x {
+  border: none;
+  background: none;
+  color: var(--miu-muted);
+  cursor: pointer;
+  padding: 0 2px;
+  line-height: 1;
+  font-size: 12px;
+}
+.miu-attach-list {
+  display: flex;
+  flex-wrap: wrap;
+  align-items: center;
+  gap: 8px;
+}
 .miu-suggest {
   position: absolute;
   left: 12px;