--- a/frontend/p2p-client.js
+++ b/frontend/p2p-client.js
@@ -6,6 +6,9 @@
  *   changed()                           a save/delete happened → re-report soon
  *   device()                            { deviceId, secret } or null
  *   authHeaders()                       { 'X-Device': … } for other P2P calls
+ *   contribute(videoId) / unknownVideos()
+ *                                       hand a saved file the server doesn't
+ *                                       know yet to /api/p2p/intake (plan 016)
  *   onMessage(type, fn) / signal(to, data) / peer()
  *                                       live /ws/p2p socket (plan 014): the
  *                                       device is "online" while it is open
@@ -33,6 +36,7 @@
   let again = false;
   let timer = null;
   let lastSync = 0;
+  let lastUnknown = []; // cids the server did not recognise at the last report
 
   function device() {
     try {
@@ -130,6 +134,7 @@
     if (r.status === 401) { try { localStorage.removeItem(KEY); } catch { /* ignore */ } return null; }
     const j = await r.json();
     if (!j || !j.ok) return null;
+    lastUnknown = Array.isArray(j.unknown) ? j.unknown : [];
     const accepted = new Set(j.accepted || []);
     for (const rec of recs) {
       if (rec.cid && accepted.has(rec.cid) && rec.state !== 'verified') { rec.state = 'verified'; await window.DeviceDB.putFile(rec); }
@@ -151,6 +156,33 @@
     return j;
   }
 
+  // ---- intake (plan 016) ---------------------------------------------------------
+  // Send one saved video to the server so it can hash + validate it and add its
+  // cid to the catalog. Uploads the whole file: only on the user's request
+  // ("Verify & share") or when the server asks for a copy (plan 018).
+  async function contribute(videoId, { cid = null, title = '', channel = '' } = {}) {
+    const dev = await ensureDevice();
+    const rec = await window.DeviceDB.getFile(videoId);
+    const file = window.OPFS.getFileObject ? await window.OPFS.getFileObject(videoId) : null;
+    if (!file) return { ok: false, error: 'not saved on this device' };
+    const h = { 'X-Device': dev.deviceId + '.' + dev.secret };
+    const t = await (await fetch('/api/p2p/intake', {
+      method: 'POST', headers: { ...h, 'Content-Type': 'application/json' },
+      body: JSON.stringify({ videoId, cid: cid || (rec && rec.cid) || undefined, size: file.size, title, channel }),
+    })).json().catch(() => ({ ok: false, error: 'server unreachable' }));
+    if (!t.ok || t.known) { if (t.known) changed(); return t; }
+    const r = await (await fetch(t.url, { method: 'PUT', headers: h, body: file }))
+      .json().catch(() => ({ ok: false, error: 'upload failed' }));
+    if (r.ok) changed();
+    return r;
+  }
+
+  async function unknownVideos() {
+    if (!lastUnknown.length || !window.DeviceDB) return [];
+    const recs = await window.DeviceDB.listFiles();
+    return recs.filter((r) => r.cid && lastUnknown.includes(r.cid)).map((r) => r.videoId);
+  }
+
   // ---- presence socket (/ws/p2p) — plan 014 ------------------------------------
   // Open while sharing OR receiving is on. Credentials go in the first message,
   // never the URL. Reconnects with backoff (5 s … 5 min).
@@ -258,7 +290,7 @@
   }
 
   window.P2PClient = {
-    start, changed, sync, device, authHeaders, config,
+    start, changed, sync, device, authHeaders, config, contribute, unknownVideos,
     onMessage, signal, peer: () => myPeer, isConnected: () => !!(ws && ws.readyState === 1 && myPeer),
   };
 }());
--- a/frontend/opfs.js
+++ b/frontend/opfs.js
@@ -108,6 +108,17 @@
       }
     },
 
+    // The saved File itself (disk-backed, not read into memory) — used as an
+    // upload body by P2P intake. null when not saved.
+    async getFileObject(videoId) {
+      try {
+        const found = await findHandle(videoId);
+        return found ? await found[0].getFile() : null;
+      } catch {
+        return null;
+      }
+    },
+
     // Bytes [offset, offset+length) of a saved video — answers the server's
     // P2P range challenges (p2p-client.js). null when the file is missing.
     async readRange(videoId, offset, length) {