Merge origin/main into the chat encryption work

Both sides landed a breaking MNP change and both called it 2.0, which is right:
the sealed upload, the removal of `stream_seg` and mandatory chat encryption
share one flag day. They are recorded as one version in `__init__.py` rather
than as a race between two.

The resolutions that were decisions rather than mechanics:

* **`MNP_MIN_SUPPORTED` moves to "2.0".** The sealed upload alone was a
  *confined* break — a 1.x peer could still connect, browse, download, stream
  and chat, with only its uploads refused by `upload_not_sealed` — so the floor
  deliberately stayed at "1.0". Mandatory chat encryption ends that
  confinement: a 1.x peer can neither produce a sealed chat message nor read
  one, so it would connect, look fine, and be unable to say anything. Refusing
  it at the handshake is the honest form. The per-message `upload_not_sealed`
  path is untouched and still right if the floor is ever lowered.
* **`sendChat` throws on an `error` reply**, from origin, applied to the sealed
  send. It matters more after this change, not less: the node now refuses a
  stale epoch, a malformed envelope and a device claim that is not the
  connection's own, so there are three new ways for a message to be rejected
  and none of them may look like a message that was sent.
* **`req_id` supersedes the per-type routing** this branch added for
  `chat_keys_resp` and `device_hello_ack`. Both blocks are kept beside the
  existing `chat_hist_resp` one, for the same stated reason — a node too old to
  stamp — and their comments no longer claim to be the mechanism that closes
  the class. `req_id` is.
* **`chat_send_probe.py` is rebuilt on origin's structure**, not beside it: two
  scenarios, a stub that stamps `req_id`, `music_meta_req` as the older pending
  request. The encrypted path is layered on — a real Ed25519 device key
  generated in the page, and a `chat_keys_resp` sealed by the shipped Python,
  because a payload the page built itself would prove only that the page agrees
  with the page.
* **`test_reply_correlation.py` now sends a sealed message.** Its subject is
  which of the two messages leaving that handler carries the id; plaintext chat
  was only the fixture, and the node refuses one now.
* `groupbox` keeps both new purposes (`upload`, `chat_keys`); `protocol.py`
  keeps origin's removal of `STREAM_SEGMENT` and this branch's correction of
  the "Double Ratchet message" comment on `CHAT_MESSAGE`, which was wrong when
  it was written and is wrong differently now.

Full suite on the merged tree: 1993 passed, 11 failed — the same 11 that fail
on a pristine checkout (2 Windows service tests, 1 apps-enabled policy, 7
transcode tests that pass in isolation, and the WebRTC invite test that hangs
on its own).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TZZxYjz8YeWRz13xDi8LJr

8 files changed, 770 insertions, 245 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/crypto.js b/packages/meshbay-hub/src/meshbay_hub/static/crypto.js
index f9cff08..24d1399 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/crypto.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/crypto.js
@@ -111,8 +111,9 @@ async function decryptChunkBin(gek, fileHashHex, chunkIndex, nonce, ct) {
 
 // ── Sealing a payload under the group key ────────────────────────────────────
 //
-// Mirrors meshbay_common/groupbox.py. `index_sync`, `index_delta` and the
-// `handshake_ack` config payload travel sealed under a GEK-derived subkey; the
+// Mirrors meshbay_common/groupbox.py. `index_sync`, `index_delta`, the
+// `handshake_ack` config payload and both halves of an upload travel sealed
+// under a GEK-derived subkey; the
 // routing fields (type, v, group_id) and the ack's own authentication (node_pk,
 // proof, sig) stay in clear, because a receiver must route, version-check and
 // *authenticate* before it would trust a decryption.
@@ -126,6 +127,12 @@ async function decryptChunkBin(gek, fileHashHex, chunkIndex, nonce, ct) {
 const GROUPBOX_INFO = {
   index: new TextEncoder().encode('meshbay:index:v1'),
   ack: new TextEncoder().encode('meshbay:ack:v1'),
+  // MNP 2.0: `file_upload` and `file_upload_ack`. This is the one purpose that
+  // seals *towards* the node — it holds the GEK for its own group — and the one
+  // with real message volume, one per 48 KB chunk. groupbox.py carries the
+  // nonce-collision arithmetic that makes a random 96-bit nonce fine at that rate.
+  upload: new TextEncoder().encode('meshbay:upload:v1'),
+  // The group's chat epoch keys, on their way to a member.
   chat_keys: new TextEncoder().encode('meshbay:chat_keys:v1'),
 };
 
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/transport.js b/packages/meshbay-hub/src/meshbay_hub/static/transport.js
index 927956d..1f6dd8f 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/transport.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/transport.js
@@ -251,7 +251,7 @@ window.addEventListener('hashchange', () => {
 // The `v: '0.1'` on every other message in this file is the historical value
 // and is read by nothing; it is left alone deliberately. The range is
 // negotiated once, at the start, not restated per message.
-const MNP_V = '1.1';
+const MNP_V = '2.0';
 const MNP_V_MIN = '1.0';
 
 // Codes a NODE sends us, in its own vocabulary (meshbay_common/handshake.py's
@@ -290,6 +290,11 @@ class MeshBayTransport {
     this._pc = null;
     this._channel = null;
     this._pending = new Map();
+    // Set the first time this connection sees a reply that names the request
+    // it answers (see _dispatch). A node either stamps every reply or none,
+    // so one is proof for the connection — and once there is proof, the
+    // arrival-order fallback at the bottom of _dispatch is never right again.
+    this._correlates = false;
     this._seqId = 0;
     this._recvBuf = new Uint8Array(0);
     this._connected = false;
@@ -299,10 +304,17 @@ class MeshBayTransport {
     this._onStreamEnd = null;
     this._onStreamError = null;
     this._onIndexSync = null;
-    // filename → the uploader waiting on it. Keyed rather than FIFO because
-    // several uploads may be in flight at once and their acks interleave; the
-    // node names the file in every one.
+    // upload_id → the uploader waiting on it. Keyed rather than FIFO because
+    // several uploads may be in flight at once and their acks interleave.
+    //
+    // It was keyed by filename until MNP 2.0, which is no longer possible: the
+    // name is sealed under the group key, and echoing it in clear so the two
+    // sides could match on it would give back precisely what the seal is for.
+    // `upload_id` is drawn per upload here and is opaque to the node.
     this._uploaders = new Map();
+    // Names, not ids: the "already being uploaded" guard is about the file the
+    // caller passed, and two `uploadFile` calls for one file draw two ids.
+    this._inFlightUploads = new Set();
     // Set once close() runs — stops the automatic reconnect from firing on a
     // connection the caller tore down on purpose (leaving the group, page
     // unload), which would otherwise race back in right as everything else
@@ -379,6 +391,19 @@ class MeshBayTransport {
     if (!m) return false;
     return (Number(m[1]) > 1) || (Number(m[1]) === 1 && Number(m[2]) >= 1);
   }
+  /**
+   * Whether the node opens a sealed upload (MNP 2.0).
+   *
+   * A 1.x node reads `filename` and `data` off the message itself, finds
+   * neither — they are inside the seal — and answers "Missing filename or
+   * data", an error about the wrong thing that names no upload_id and so fails
+   * every upload in flight. Asked before sending rather than discovered after,
+   * for the same reason `supportsAppOps` is.
+   */
+  get supportsSealedUpload() {
+    const m = /^(\d+)\.(\d+)$/.exec(this._nodeVersion || '');
+    return !!m && Number(m[1]) >= 2;
+  }
   set onAppsEnabled(fn) { this._onAppsEnabled = fn; }
   set onAppDirectories(fn) { this._onAppDirectories = fn; }
   set onChatDirectory(fn) { this._onChatDirectory = fn; }
@@ -1456,18 +1481,6 @@ class MeshBayTransport {
     return msg;
   }
 
-  async fetchStreamSegment(fileId, segmentIndex, segmentDuration) {
-    const msg = await this._sendAndWait({
-      type: 'stream_seg',
-      v: '0.1',
-      file_id: fileId,
-      segment_index: segmentIndex,
-      segment_duration: segmentDuration || 4,
-    });
-    if (msg.type === 'error') throw new Error(msg.detail);
-    return _b64decode(msg.data_b64);
-  }
-
   /**
    * A page of chat history, newest first by default.
    *
@@ -1583,7 +1596,7 @@ class MeshBayTransport {
       this._sessionKeys.skEdB64,
       C.chatSigningTranscript(gid, epoch, device, nonce, ct)));
 
-    return this._sendAndWait({
+    const msg = await this._sendAndWait({
       type: 'chat_msg',
       v: '2.0',
       format: 1,
@@ -1596,6 +1609,15 @@ class MeshBayTransport {
       // Deliberately absent: the display name is inside the envelope now.
       sender_name: null,
     });
+    // Every other request in this file refuses an `error` reply; this one
+    // returned it as though the node had accepted the message. It never
+    // mattered while a refusal reached the wrong caller anyway — now that a
+    // reply finds the request that made it, a message the node rejected would
+    // otherwise appear in the conversation as sent. It rejects more of them
+    // than it used to: a stale epoch, an envelope the node dislikes, or a
+    // device claim that is not this connection's all come back as `error`.
+    if (msg.type === 'error') throw new Error(msg.detail || 'chat send refused');
+    return msg;
   }
 
   /**
@@ -2080,10 +2102,21 @@ class MeshBayTransport {
    */
   async uploadFile(file, { chunkSize, onProgress, signal, root, dir } = {}) {
     // The same file twice at once would confuse the node, which keys its own
-    // upload state by name — and would race for the same destination.
-    if (this._uploaders.has(file.name)) {
+    // upload state by name — and would race for the same destination. The guard
+    // is by name for that reason, even though the map below is keyed by id.
+    if (this._inFlightUploads.has(file.name)) {
       throw new Error(`${file.name} is already being uploaded`);
     }
+    if (!this._gekRaw) throw new Error('This group has no key on this device');
+    if (!this.supportsSealedUpload) {
+      throw new Error(
+        'This node is running an older MeshBay and cannot accept an upload '
+        + 'from this page. Its operator has to update it.');
+    }
+    const C = window.MeshBayCrypto;
+    const groupId = (this._connectArgs && this._connectArgs.groupId) || '';
+    this._inFlightUploads.add(file.name);
+    const uploadId = _hex(crypto.getRandomValues(new Uint8Array(16)));
     const size = chunkSize || UPLOAD_CHUNK_SIZE;
     const total = Math.max(1, Math.ceil(file.size / size));
     let acked = 0;
@@ -2091,16 +2124,32 @@ class MeshBayTransport {
     let failure = null;
 
     const acks = [];
-    this._uploaders.set(file.name, (msg) => {
-      if (msg.type === 'error') {
-        failure = new Error(msg.detail || 'Upload refused');
-      } else if (msg.stored_as) {
-        stored = msg;
-      }
+    const wake = () => {
       acked += 1;
       if (onProgress) onProgress(Math.min(file.size, acked * size), file.size);
       const waiter = acks.shift();
       if (waiter) waiter();
+    };
+    this._uploaders.set(uploadId, (msg) => {
+      if (msg.type === 'error') {
+        failure = new Error(msg.detail || 'Upload refused');
+        wake();
+        return;
+      }
+      // The ack is sealed too — `stored_as` and the folder it landed in name
+      // the operator's content. Opening it is what makes the result usable, so
+      // a failure here fails the upload rather than being swallowed: a chat
+      // attachment that cannot learn its stored name would point at nothing.
+      C.openGroup(this._gekRaw, 'upload', 'file_upload_ack', groupId, msg)
+        .then((plain) => {
+          const payload = msgpack_decode(plain);
+          if (payload.stored_as) stored = payload;
+        })
+        .catch((e) => {
+          failure = new Error(
+            `The node's upload reply did not open under the group key (${e.message})`);
+        })
+        .finally(wake);
     });
 
     const nextAck = () => new Promise(r => acks.push(r));
@@ -2122,15 +2171,20 @@ class MeshBayTransport {
 
         const buf = new Uint8Array(
           await file.slice(i * size, (i + 1) * size).arrayBuffer());
+        // The name, the destination and the bytes go inside the seal together.
+        // Mirrors `file_upload_wire` in meshbay_common/protocol.py; only the
+        // fields the node routes on stay outside it.
+        const sealed = await C.sealGroup(
+          this._gekRaw, 'upload', 'file_upload', groupId,
+          msgpack_encode({ filename: file.name, data: buf,
+                           dir: dir || '', root: root || '' }));
         this._send({
           type: 'file_upload',
           v: '0.1',
-          filename: file.name,
+          upload_id: uploadId,
           chunk_index: i,
           total_chunks: total,
-          data: buf,
-          ...(root ? { root } : {}),
-          ...(dir ? { dir } : {}),
+          ...sealed,
         });
       }
       while (acked < total) {
@@ -2138,7 +2192,8 @@ class MeshBayTransport {
         if (failure) throw failure;
       }
     } finally {
-      this._uploaders.delete(file.name);
+      this._uploaders.delete(uploadId);
+      this._inFlightUploads.delete(file.name);
     }
     return stored || {};
   }
@@ -2458,12 +2513,15 @@ class MeshBayTransport {
 
     if (msg.type === 'index_sync') {
       if (this._onIndexSync) this._onIndexSync(opened);
-      for (const [, handler] of this._pending) {
-        if (handler._reqType === 'index_sync') {
-          handler.resolve(opened);
-          break;
-        }
-      }
+      // The node's first push to a newly connected peer is an index_sync
+      // nobody asked for, so there is not always a request to resolve. When
+      // there is, `req_id` says which one — the type match below is what a
+      // node too old to stamp one leaves us, and it is why two fetches in
+      // flight at once used to resolve the wrong one.
+      const handler = opened.req_id !== undefined && opened.req_id !== null
+        ? this._pending.get(opened.req_id)
+        : [...this._pending.values()].find(h => h._reqType === 'index_sync');
+      if (handler) handler.resolve(opened);
       return;
     }
     if (this._onIndexDelta) this._onIndexDelta(opened);
@@ -2550,7 +2608,13 @@ class MeshBayTransport {
         resolve: (msg) => { clearTimeout(timeout); this._pending.delete(id); resolve(msg); },
         reject: (err) => { clearTimeout(timeout); this._pending.delete(id); reject(err); },
       });
-      this._send(obj);
+      // The id goes on the wire (MNP 1.1+): a node that understands it stamps
+      // the reply with it, and _dispatch matches on that alone. It used to be
+      // local to this map, which is why every reply had to be recognised by
+      // some field of its own — and why the ones that carry no such field
+      // reached their caller by luck. An older node ignores the extra key and
+      // is routed by the per-type fallbacks below, exactly as before.
+      this._send({ ...obj, req_id: id });
     });
   }
 
@@ -2590,6 +2654,45 @@ class MeshBayTransport {
   }
 
   _dispatch(msg) {
+    // A reply that names the request it answers. Nothing below this needs to
+    // recognise it, and nothing below this may see it: every remaining branch
+    // exists to identify a reply by some field of its own, which is the job
+    // this makes unnecessary.
+    //
+    // What is left underneath is genuinely unsolicited — a broadcast to every
+    // connected client, a push, a challenge — or a reply from a node too old
+    // to stamp one, which is what the per-type keys are for now.
+    if (msg.req_id !== undefined && msg.req_id !== null) {
+      this._correlates = true;
+      // The one exception, and the only one: an index message is sealed under
+      // the GEK and cannot be handed to its caller until it is opened, which
+      // is not something this synchronous function can do. Resolving it here
+      // would give `fetchIndex` the envelope — nonce and ciphertext, no
+      // entries — and skip `_onIndexSync` entirely. `_queueIndexMessage`
+      // opens it and then resolves, by this same id.
+      const sealed = msg.type === 'index_sync' || msg.type === 'index_delta';
+      if (!sealed) {
+        const handler = this._pending.get(msg.req_id);
+        if (handler) {
+          handler.resolve(msg);
+          // The acks whose *broadcast* half their own requester also needs:
+          // every other client learns the change from the broadcast, and the
+          // one that asked for it is the only one that would not, because its
+          // own request swallowed its copy. Same call the keyed `_ack` branch
+          // below makes, for the same reason.
+          if (BROADCAST_ACK_TYPES.has(msg.type)) _replayBroadcast(this, msg);
+          return;
+        }
+        // Answers a request that is no longer waiting: it gave up at its own
+        // timeout, or a reconnect rejected everything in flight. It belongs to
+        // nobody, and the whole point of this change is that it is not offered
+        // to somebody else instead.
+        console.warn('[MeshBay] late reply to req', msg.req_id, '(', msg.type,
+                     ') — nothing waiting');
+        return;
+      }
+    }
+
     // Two-step admin-op flow (_authorizeAdminOp, ADMIN_OP_TYPES) — resolve
     // by (op) key before anything below gets a chance to steal it via the
     // generic "oldest pending" fallback further down. Returns as soon as a
@@ -2647,21 +2750,21 @@ class MeshBayTransport {
     // While an upload is in flight the acks are its own, and there are many of
     // them: they must not be handed to whatever request happens to be oldest in
     // the pending map.
-    if (msg.type === 'file_upload_ack' && this._uploaders.has(msg.filename)) {
-      this._uploaders.get(msg.filename)(msg);
+    if (msg.type === 'file_upload_ack' && this._uploaders.has(msg.upload_id)) {
+      this._uploaders.get(msg.upload_id)(msg);
       return;
     }
-    // An upload refusal names the file it is about, so only that upload fails.
-    // It did not use to, and there was no way to tell whose error it was, so
-    // every upload in flight was failed together — send a second file whose
-    // name the node dislikes and both died. The broadcast is kept for a node
-    // that does not name it, where guessing wrong is worse than stopping.
+    // An upload refusal names the upload it is about, so only that upload
+    // fails. It did not use to, and there was no way to tell whose error it
+    // was, so every upload in flight was failed together — send a second file
+    // whose name the node dislikes and both died. The broadcast is kept for a
+    // refusal that names none, where guessing wrong is worse than stopping.
     if (msg.type === 'error' && this._uploaders.size) {
-      if (msg.filename && this._uploaders.has(msg.filename)) {
-        this._uploaders.get(msg.filename)(msg);
+      if (msg.upload_id && this._uploaders.has(msg.upload_id)) {
+        this._uploaders.get(msg.upload_id)(msg);
         return;
       }
-      if (!msg.filename) {
+      if (!msg.upload_id) {
         for (const handler of [...this._uploaders.values()]) handler(msg);
         return;
       }
@@ -2955,10 +3058,10 @@ class MeshBayTransport {
       return;
     }
 
-    // device_hello_ack ends in `_ack` but is not an admin op, so the branch
-    // above looks it up under `admin:device_hello`, finds nothing, and drops it
-    // through to the arrival-order guess. Routed by request type instead: a
-    // request type deserves a key, and a reply deserves something to key it by.
+    // device_hello_ack ends in `_ack` but is not an admin op, so the admin
+    // branch looks it up under `admin:device_hello` and finds nothing. A 2.0
+    // node stamps `req_id` and this is never reached; it is the per-type key
+    // for a node that does not, alongside chat_hist_resp above.
     if (msg.type === 'device_hello_ack') {
       for (const [, handler] of this._pending) {
         if (handler._reqType === 'device_hello') { handler.resolve(msg); return; }
@@ -2968,14 +3071,13 @@ class MeshBayTransport {
     }
 
     // Same shape as chat_hist_resp above, and found the same way — by driving
-    // the panel rather than by reading this file. `chat_keys_resp` answers a
-    // `chat_keys_req` under a different type string, so without this it fell
-    // to the arrival-order guess at the end and was handed to whatever was
-    // oldest in `_pending`. `chat_send_probe.py` caught it on its first run:
-    // the Videos tab's unanswered `media_meta_req` swallowed the chat keys,
-    // and the send then waited out its own 30s timeout with the composer
-    // disabled — which is a frozen Chat tab, the exact defect that harness
-    // exists for, reappearing one feature later.
+    // the panel rather than by reading this file. Before `req_id` existed,
+    // `chat_keys_resp` fell to the arrival-order guess and was handed to
+    // whatever was oldest in `_pending`; `chat_send_probe.py` caught it on its
+    // first run, with the Videos tab's unanswered `media_meta_req` swallowing
+    // the chat keys and the send then waiting out its own 30s timeout with the
+    // composer disabled. `req_id` is what closes that class now, and this is
+    // the per-type key for a node that does not stamp one.
     if (msg.type === 'chat_keys_resp') {
       for (const [, handler] of this._pending) {
         if (handler._reqType === 'chat_keys_req') { handler.resolve(msg); return; }
@@ -3020,10 +3122,28 @@ class MeshBayTransport {
       return;
     }
 
-    // Everything above is routed by something in the message. What is left is
-    // matched by arrival order, which is only ever a guess — and a wrong guess
-    // here hands one request's answer to another, which then waits for a reply
-    // that already came. Logged so that guess is visible.
+    // Everything above is routed by something in the message. What is left
+    // used to be matched by arrival order — a guess, and a wrong guess hands
+    // one request's answer to another, which then waits out its own 30s
+    // timeout for a reply that already came and went. That is how the Chat
+    // composer, disabled while a send is in flight, could stay disabled for
+    // thirty seconds on a message the node had already stored.
+    //
+    // A node that stamps its replies (`req_id`, handled at the top) has taken
+    // every one of its answers out of this path, so anything arriving here is
+    // unsolicited and the guess can only ever be wrong. Dropping it loses
+    // nothing and stops the theft.
+    if (this._correlates) {
+      console.warn('[MeshBay] unsolicited', msg.type, '— dropped (pending:',
+                   this._pending.size, ')');
+      return;
+    }
+
+    // Only a node too old to stamp anything reaches here, where arrival order
+    // is still the only thing there is. Kept deliberately, and no wider than
+    // it was: the alternative for such a node is that half the protocol
+    // (device_list_result, join_result, the handshake's own replies) reaches
+    // nobody at all.
     const oldest = this._pending.entries().next();
     if (!oldest.done) {
       const [, handler] = oldest.value;
@@ -3276,11 +3396,8 @@ function _decodeMap(buf, view, offset, count) {
   return [obj, offset];
 }
 
-function _b64decode(b64) {
-  const binary = atob(b64);
-  const bytes = new Uint8Array(binary.length);
-  for (let i = 0; i < binary.length; i++) bytes[i] = binary.charCodeAt(i);
-  return bytes;
+function _hex(bytes) {
+  return [...bytes].map(b => b.toString(16).padStart(2, '0')).join('');
 }
 
 function _extractDtlsFingerprint(sdp) {
diff --git a/packages/meshbay-hub/tests/harness/chat_send_probe.py b/packages/meshbay-hub/tests/harness/chat_send_probe.py
index 1f0557b..5f99beb 100644
--- a/packages/meshbay-hub/tests/harness/chat_send_probe.py
+++ b/packages/meshbay-hub/tests/harness/chat_send_probe.py
@@ -20,8 +20,40 @@ never appeared, while the node had stored it all along.
 
     chat_send_probe.py
 
-Prints JSON: `steps`, the state of the panel at each stage, and `log`, what the
-transport sent and how the deliberately-unanswered request ended up.
+It now drives two shapes of reply, because there were two ways for one to go
+astray and only the first was ever fixed:
+
+  `ack`    the node accepts the message and answers `{"type": "ack"}`, which
+           names no request. Routed by request type since 2026-08-30.
+  `error`  the node *refuses* it — every failure in `_dispatch_message` ends at
+           one catch-all sending `{"type": "error", "detail": "Request failed"}`,
+           and 238 of this module's 240 error sends name nothing either. That
+           reply reached no caller at all: it went to whatever request happened
+           to be waiting, and the send sat out its own 30s timeout with the
+           composer disabled.
+
+Both are run with an older request already pending — the condition that turns
+"guess by arrival order" from usually-right into wrong — and both must come
+back inside a second and a half.
+
+Since MNP 2.0 a send also has to **seal and sign for real** before it goes
+anywhere, so this drives `chatKeys()`, `openGroup`, `sealChat` and a genuine
+Ed25519 signature rather than a model of any of them. The device key is
+generated in the page — `signBytes` imports a pkcs8 key and WebCrypto will not
+be fooled by a stand-in — and the `chat_keys_resp` the stub answers with is
+sealed **by the shipped Python**, because a payload the page built itself would
+prove only that the page agrees with the page.
+
+That path found two defects the moment it first ran, neither visible in any
+source file: `chat_keys_resp` was routed by arrival order and handed to the
+older pending request (this defect, in a message type that did not exist when
+the probe was written), and `_asText` had been deleted along with an unrelated
+helper beside it — its only caller sits inside a promise the panel catches, so
+every conversation rendered empty with nothing in the console.
+
+Prints JSON: `scenarios`, the state of the panel at each stage of each, and
+`log`, what the transport sent and how the deliberately-unanswered request
+ended up.
 """
 import http.server
 import json
@@ -49,9 +81,9 @@ def _page() -> str:
 
     Sealed here, by the shipped Python, rather than assembled in the browser:
     msgpack is private to transport.js and exported to nothing, and a payload
-    the test built itself would prove only that the page agrees with the page.
+    the page built itself would prove only that the page agrees with the page.
     """
-    import msgpack
+    import msgpack  # noqa: F401  (imported for the failure it gives if absent)
 
     from meshbay_common.groupbox import PURPOSE_CHAT_KEYS, seal
 
@@ -73,9 +105,7 @@ PAGE_TEMPLATE = r"""<!doctype html><html><head><meta charset=utf-8>
 </div></div>
 <!-- The two the real page loads and the transport reaches for by global:
      `sealChat`/`openGroup` live in crypto.js, `signBytes` in keyderive.js.
-     Without them a send fails with "cannot read properties of undefined",
-     which is what this probe reported the first time it exercised the
-     encrypted path. -->
+     Without them a send fails with "cannot read properties of undefined". -->
 <script src="/crypto.js"></script>
 <script src="/keyderive.js"></script>
 <script src="/transport.js"></script>
@@ -87,37 +117,16 @@ const log = [];
 window.addEventListener('error', e => log.push('error: ' + e.message));
 window.addEventListener('unhandledrejection',
   e => log.push('rejected: ' + (e.reason && e.reason.message || e.reason)));
-const _warn = console.warn, _err = console.error;
-console.warn = (...a) => { log.push('warn: ' + a.join(' ')); _warn(...a); };
-console.error = (...a) => { log.push('console error: ' + a.join(' ')); _err(...a); };
 
 const hex = (s) => Uint8Array.from(s.match(/../g) || [], b => parseInt(b, 16));
+const b64 = (buf) => btoa(String.fromCharCode(...new Uint8Array(buf)));
 
-// The real transport, with only the channel replaced: _send takes the plain
-// object _sendAndWait built, so the framing and msgpack are the only things
-// skipped — every pending entry, key and dispatch path below is the shipped one.
-const tp = new window.MeshBayTransport('', 'token');
-tp._connected = true;
-tp._channel = { readyState: 'open', send() {} };
-
-// Chat is encrypted (MNP 2.0), so a send that is going to come back has to
-// seal and sign for real. The device key is generated here rather than stubbed
-// — `signBytes` imports a pkcs8 key and WebCrypto will not be fooled — and the
-// group key and epoch keys come from Python, which sealed the `chat_keys_resp`
-// below exactly as the node does. So this exercises `chatKeys()`, `openGroup`,
-// `sealChat` and the real signature, not a model of any of them.
-tp._groupId = '__GROUP_ID__';
-tp._gekRaw = hex('__GEK_HEX__');
-tp.chatEpoch = 1;
-
+// One device key for both scenarios. Real, not stubbed: `signBytes` imports a
+// pkcs8 key, so nothing else gets a signature past `verifyChatSignature`.
 const kp = await crypto.subtle.generateKey({ name: 'Ed25519' }, true,
                                            ['sign', 'verify']);
-const b64 = (buf) => btoa(String.fromCharCode(...new Uint8Array(buf)));
-tp._sessionKeys = {
-  skEdB64: b64(await crypto.subtle.exportKey('pkcs8', kp.privateKey)),
-};
-// What `device_hello` sets on a live connection.
-tp.devicePk = b64(await crypto.subtle.exportKey('raw', kp.publicKey));
+const SK_ED_B64 = b64(await crypto.subtle.exportKey('pkcs8', kp.privateKey));
+const DEVICE_PK_B64 = b64(await crypto.subtle.exportKey('raw', kp.publicKey));
 
 const now = Date.now() / 1000;
 const history = [];
@@ -126,75 +135,72 @@ for (let i = 0; i < 5; i++) {
                  payload: 'message ' + i, timestamp: now - (5 - i) * 60 });
 }
 
-// Stands in for the node, answering exactly what webrtc_server.py answers.
-// media_meta_req is answered with nothing at all, which is what a refusal
-// amounts to for the request that asked: `_do_media_meta_request` sends a bare
-// `error` for a file_id the index does not have, and a bare error names no
-// request, so it reaches none.
-tp._send = (obj) => {
-  log.push('sent ' + obj.type);
-  if (obj.type === 'chat_hist') {
-    setTimeout(() => {
-      log.push('answering chat_hist');
-      tp._dispatch({ type: 'chat_hist_resp', v: '0.2', messages: history,
-                     has_more: false });
-    }, 10);
-  } else if (obj.type === 'chat_keys_req') {
-    // Sealed under the group key, as `_do_chat_keys_req` sends it.
-    setTimeout(() => tp._dispatch({
-      type: 'chat_keys_resp', v: '2.0', group_id: tp._groupId,
-      nonce: hex('__KEYS_NONCE_HEX__'), ct: hex('__KEYS_CT_HEX__'),
-    }), 10);
-  } else if (obj.type === 'chat_msg') {
-    // Recorded so the test can assert the message really was sealed and
-    // signed rather than sent in clear past a composer that let it through.
-    log.push('chat_msg format=' + obj.format + ' epoch=' + obj.epoch
-             + ' ct=' + (obj.ct ? obj.ct.length : 0)
-             + ' sig=' + (obj.sig ? obj.sig.length : 0)
-             + ' plaintextLeak=' + JSON.stringify(obj).includes('hello'));
-    setTimeout(() => tp._dispatch({ type: 'ack', v: '2.0' }), 10);
-  }
-};
+const wait = ms => new Promise(r => setTimeout(r, ms));
 
-// The panel swallows a send failure into `setInput(text)`, which is right for
-// a person and useless for a probe: the symptom is the message not appearing,
-// with no reason anywhere. Surfaced here so a failure names itself.
-const _sendChat = tp.sendChat.bind(tp);
-tp.sendChat = (...a) => _sendChat(...a).catch((e) => {
-  log.push('sendChat failed: ' + (e && e.message || e));
-  throw e;
-});
+// Stands in for the node, answering what webrtc_server.py answers — including
+// stamping the reply with the id of the request it is answering, which is what
+// `_send` does there. `chatReply` is the only difference between the two runs.
+function makeTransport(name, chatReply) {
+  // The real transport, with only the channel replaced: _send takes the plain
+  // object _sendAndWait built, so the framing and msgpack are the only things
+  // skipped — every pending entry, key and dispatch path below is the shipped
+  // one.
+  const tp = new window.MeshBayTransport('', 'token');
+  tp._connected = true;
+  tp._channel = { readyState: 'open', send() {} };
+  // What a completed MNP 2.0 handshake leaves behind: the group and its key
+  // from `connect`, the current epoch from the sealed ack, and the device this
+  // connection identified itself as with `device_hello`.
+  tp._groupId = '__GROUP_ID__';
+  tp._gekRaw = hex('__GEK_HEX__');
+  tp.chatEpoch = 1;
+  tp._sessionKeys = { skEdB64: SK_ED_B64 };
+  tp.devicePk = DEVICE_PK_B64;
+  tp._send = (obj) => {
+    log.push('sent ' + obj.type);
+    const answer = (reply) => setTimeout(
+      () => tp._dispatch({ ...reply, req_id: obj.req_id }), 10);
+    if (obj.type === 'chat_hist') {
+      answer({ type: 'chat_hist_resp', v: '0.2', messages: history, has_more: false });
+    } else if (obj.type === 'chat_keys_req') {
+      // Sealed under the group key, as `_do_chat_keys_req` sends it.
+      answer({ type: 'chat_keys_resp', v: '2.0', group_id: tp._groupId,
+               nonce: hex('__KEYS_NONCE_HEX__'), ct: hex('__KEYS_CT_HEX__') });
+    } else if (obj.type === 'chat_msg') {
+      // Recorded so the test can assert what actually left the browser, rather
+      // than trusting that a composer which accepted the text sealed it.
+      log.push(name + ': chat_msg format=' + obj.format + ' epoch=' + obj.epoch
+               + ' ct=' + (obj.ct ? obj.ct.length : 0)
+               + ' sig=' + (obj.sig ? obj.sig.length : 0)
+               + ' plaintextLeak=' + JSON.stringify(obj).includes('hello'));
+      answer(chatReply);
+    }
+    // music_meta_req is answered by nothing at all, on purpose: the node holds
+    // one open for as long as the third-party lookup behind it takes, which
+    // was measured at over 100 seconds with that service failing. It is the
+    // older pending request every scenario here needs.
+  };
+  // The panel swallows a send failure into `setInput(text)`, which is right for
+  // a person and useless for a probe: the symptom is a message not appearing,
+  // with no reason anywhere. Surfaced here so a failure names itself — the
+  // `error` scenario is *expected* to reach this.
+  const _sendChat = tp.sendChat.bind(tp);
+  tp.sendChat = (...a) => _sendChat(...a).catch((e) => {
+    log.push(name + ': sendChat failed: ' + (e && e.message || e));
+    throw e;
+  });
+  return tp;
+}
 
-function Host() {
+function Host({ tp }) {
   const transportRef = useRef(tp);
   const gekRef = useRef(null);
   return html`<${ChatPanel} transportRef=${transportRef} gekRef=${gekRef}
     username="me" userId="user-me" entries=${[]} status="connected" />`;
 }
-render(html`<${Host} />`, document.getElementById('root'));
 
-const out = { steps: [], log };
-const composer = () => document.querySelector('.chat-input');
-
-function snap(label) {
-  const c = composer();
-  out.steps.push({
-    label,
-    bubbles: document.querySelectorAll('.chat-bubble').length,
-    msgs: document.querySelectorAll('.chat-msg').length,
-    lastText: [...document.querySelectorAll('.chat-text')].pop()?.textContent ?? null,
-    // What a frozen tab actually is: the composer is disabled for as long as
-    // a send is in flight.
-    composerDisabled: c ? c.disabled : null,
-    composerValue: c ? c.value : null,
-    pending: tp._pending.size,
-  });
-}
-
-const wait = ms => new Promise(r => setTimeout(r, ms));
-
-function typeInto(text) {
-  const c = composer();
+function typeInto(root, text) {
+  const c = root.querySelector('.chat-input');
   c.focus();
   // Preact reads e.target.value on input, so the native setter has to run.
   Object.getOwnPropertyDescriptor(window.HTMLTextAreaElement.prototype, 'value')
@@ -202,22 +208,42 @@ function typeInto(text) {
   c.dispatchEvent(new Event('input', { bubbles: true }));
 }
 
-(async () => {
+async function runScenario(name, chatReply) {
+  const root = document.createElement('div');
+  document.getElementById('root').appendChild(root);
+  const tp = makeTransport(name, chatReply);
+  render(html`<${Host} tp=${tp} />`, root);
+
+  const steps = [];
+  const snap = (label) => {
+    const c = root.querySelector('.chat-input');
+    steps.push({
+      label,
+      bubbles: root.querySelectorAll('.chat-bubble').length,
+      lastText: [...root.querySelectorAll('.chat-text')].pop()?.textContent ?? null,
+      // What a frozen tab actually is: the composer is disabled for as long as
+      // a send is in flight.
+      composerDisabled: c ? c.disabled : null,
+      composerValue: c ? c.value : null,
+      pending: tp._pending.size,
+    });
+  };
+
   await wait(500);
   snap('arrived');
 
-  // The Videos tab asked about a file a moment ago and is still waiting. Any
-  // unanswered request will do; this is the one that was live when the defect
-  // was found.
-  tp.fetchMediaMeta('a-file-the-node-refused')
-    .then(m => log.push('media_meta resolved with ' + m.type),
-          e => log.push('media_meta rejected: ' + e.message));
+  // The Music tab asked about a track and is still waiting on the node, which
+  // is waiting on something else. Any older unanswered request will do; this
+  // is the one that was live when the defect was found.
+  tp.fetchMusicMeta('a-track-the-node-is-slow-about')
+    .then(m => log.push(name + ': music_meta resolved with ' + m.type),
+          e => log.push(name + ': music_meta rejected: ' + e.message));
   await wait(100);
-  snap('stale request pending');
+  snap('older request pending');
 
-  typeInto('hello');
+  typeInto(root, 'hello');
   await wait(100);
-  composer().dispatchEvent(new KeyboardEvent('keydown',
+  root.querySelector('.chat-input').dispatchEvent(new KeyboardEvent('keydown',
     { key: 'Enter', bubbles: true, cancelable: true }));
 
   // Far short of _sendAndWait's 30s timeout: a send that has not come back by
@@ -225,6 +251,14 @@ function typeInto(text) {
   await wait(1500);
   snap('after send');
 
+  return { name, steps };
+}
+
+(async () => {
+  const out = { scenarios: [], log };
+  out.scenarios.push(await runScenario('ack', { type: 'ack', v: '0.14' }));
+  out.scenarios.push(await runScenario(
+    'error', { type: 'error', detail: 'Request failed' }));
   fetch('/log', { method: 'POST', body: JSON.stringify(out) });
 })();
 </script></body></html>"""
diff --git a/packages/meshbay-hub/tests/harness/upload_seal_probe.mjs b/packages/meshbay-hub/tests/harness/upload_seal_probe.mjs
new file mode 100644
index 0000000..0b77e42
--- /dev/null
+++ b/packages/meshbay-hub/tests/harness/upload_seal_probe.mjs
@@ -0,0 +1,102 @@
+/**
+ * Does the browser's real `uploadFile` produce frames a real node can open —
+ * and does it read back what that node actually answered?
+ *
+ * Drives **the real `MeshBayTransport` over the real `crypto.js`**. Only the DOM
+ * and the DataChannel are stand-ins; the msgpack encode, the HKDF, the AES-GCM
+ * and the whole upload loop are the shipped code.
+ *
+ * It exists because a source-reading test cannot show either half of MNP 2.0's
+ * upload. `test_transport_contracts` can see that `sealGroup` is called; only
+ * this can show that what comes out opens under `meshbay_common.groupbox` — and
+ * that the caller of `uploadFile` is told the name the *node* chose, which now
+ * arrives sealed and would otherwise be `undefined` with nothing to notice it.
+ *
+ *   node upload_seal_probe.mjs <static-dir> <input.json>
+ *
+ * Two modes, because the node half runs in Python between them:
+ *   "send"    — run the upload, print every frame it emits, answer nothing
+ *   "receive" — run it again, answering with acks Python built. Their
+ *               `upload_id` is retargeted to this run's; it is outside the
+ *               seal, so the ciphertext stays exactly the one Python produced.
+ */
+import fs from 'fs';
+
+const STATIC = process.argv[2];
+const input = JSON.parse(fs.readFileSync(process.argv[3], 'utf8'));
+
+for (const level of ['log', 'warn', 'error', 'info', 'debug']) {
+  console[level] = (...args) => process.stderr.write(args.join(' ') + '\n');
+}
+
+globalThis.window = globalThis;
+globalThis.addEventListener = () => {};
+globalThis.removeEventListener = () => {};
+globalThis.location = { hash: '' };
+globalThis.document = {
+  addEventListener() {}, removeEventListener() {}, visibilityState: 'visible',
+};
+
+new Function(fs.readFileSync(`${STATIC}/crypto.js`, 'utf8'))();
+const transportSrc = fs.readFileSync(`${STATIC}/transport.js`, 'utf8');
+new Function(transportSrc)();
+// The msgpack codec is private to transport.js — pulled out the same way the
+// groupbox parity harness pulls out sealGroup, so this probe encodes and
+// decodes with the codec that is actually shipped rather than a second one.
+const { msgpack_encode, msgpack_decode } =
+  new Function(transportSrc + '\nreturn { msgpack_encode, msgpack_decode };')();
+
+const hex = (s) => Uint8Array.from(s.match(/../g).map((b) => parseInt(b, 16)));
+const toHex = (u8) =>
+  Array.from(u8).map((b) => b.toString(16).padStart(2, '0')).join('');
+
+// Just enough of a File: a name, a size, and slices that yield ArrayBuffers.
+const bytes = hex(input.file.data);
+const file = {
+  name: input.file.name,
+  size: bytes.length,
+  slice(a, b) {
+    const part = bytes.slice(a, b);
+    return { arrayBuffer: async () => part.buffer.slice(
+      part.byteOffset, part.byteOffset + part.byteLength) };
+  },
+};
+
+const tp = new window.MeshBayTransport('', 'token');
+tp._connected = true;
+tp._channel = { readyState: 'open', bufferedAmount: 0, send() {}, close() {} };
+tp._pc = { close() {} };
+tp._gekRaw = hex(input.gek);
+tp._connectArgs = { groupId: input.group_id };
+tp._nodeVersion = input.node_version;
+
+const frames = [];
+let uploadId = null;
+tp._send = (msg) => {
+  frames.push(toHex(msgpack_encode(msg)));
+  if (msg.upload_id) uploadId = msg.upload_id;
+  if (input.mode !== 'receive') return;
+  // Answer as the node did, on the next turn of the loop so the send path
+  // finishes first — which is also how a real ack arrives.
+  const ack = msgpack_decode(hex(input.acks[msg.chunk_index]));
+  ack.upload_id = uploadId;
+  // Through the real `_dispatch`, so the routing under test — matching an
+  // ack to its uploader by `upload_id` — is the shipped one.
+  setImmediate(() => tp._dispatch(ack));
+};
+
+const out = { frames, mode: input.mode };
+const done = tp.uploadFile(file, { chunkSize: input.chunk_size,
+                                   dir: input.dir, root: input.root });
+
+if (input.mode === 'receive') {
+  done.then((stored) => { out.state = 'resolved'; out.stored = stored; })
+      .catch((e) => { out.state = 'rejected'; out.message = e.message; })
+      .finally(() => { out.upload_id = uploadId;
+                       process.stdout.write(JSON.stringify(out)); });
+} else {
+  // Nothing will answer, so let the send loop run itself out and report.
+  done.catch((e) => { out.state = 'rejected'; out.message = e.message; });
+  setTimeout(() => { out.upload_id = uploadId;
+                     process.stdout.write(JSON.stringify(out)); }, 250);
+}
diff --git a/packages/meshbay-hub/tests/test_chat_send.py b/packages/meshbay-hub/tests/test_chat_send.py
index 250c9a3..5db8f26 100644
--- a/packages/meshbay-hub/tests/test_chat_send.py
+++ b/packages/meshbay-hub/tests/test_chat_send.py
@@ -1,38 +1,29 @@
 """
-Sending a chat message must come back — and must go out encrypted.
+Sending a chat message must come back — accepted or refused.
 
-The node answers a chat message with a bare `{"type": "ack"}` — no request id,
-no type of its own — so `_dispatch` had nothing to match it on and left it to
-the arrival-order guess at the end of the function. That guess is wrong as soon
-as anything else this browser asked for is still waiting: the ack was handed to
-*that* request, and the send waited out `_sendAndWait`'s 30s timeout. Since the
-composer is disabled while a send is in flight, the Chat tab stopped taking
-clicks and keys, the message never appeared — and it was there on the next
-visit, because the node had stored it and answered.
+The node's replies to a chat message name no request. The acceptance is a bare
+`{"type": "ack"}`; the refusal is a bare `{"type": "error"}`, and it is not a
+special case — `_dispatch_message`'s catch-all answers *every* failure that
+way, and 238 of webrtc_server.py's 240 error sends name nothing either. So
+`_dispatch` had nothing to match either reply on and left both to the
+arrival-order guess at the end of the function.
 
-An outstanding request is the ordinary case, not a rare one: the node refuses
-an unknown file_id with a bare `error`, which names no request either, so a
-Videos tab that asked about a file the index no longer has leaves a
-`media_meta_req` in `_pending` for a full 30s.
+That guess is wrong as soon as anything else this browser asked for is still
+waiting, which is the ordinary case rather than a rare one: a `music_meta_req`
+sits in `_pending` for as long as the third-party lookup behind it takes, and
+that was measured live at over 100 seconds with the service failing. The reply
+went to *that* request, and the send waited out `_sendAndWait`'s 30s timeout.
+Since the composer is disabled while a send is in flight, the Chat tab stopped
+taking clicks and keys, and the message never appeared.
 
-None of that is visible in `chat-app.js`, where every line is correct, so this
+The ack half was fixed by matching on request type. The refusal half could not
+be: an `error` has no type of its own to match on. `req_id` is what closed it —
+the caller's id, stamped on the reply by the node — so this now drives both
+shapes of answer.
+
+None of it is visible in `chat-app.js`, where every line is correct, so this
 drives the real panel over the real transport in a browser rather than reading
 either source.
-
-Extended for MNP 2.0, where a send seals and signs before it goes anywhere.
-That turned out to matter twice on its first run:
-
-  * `chat_keys_resp` answers a `chat_keys_req` under a different type string,
-    so it fell through to the arrival-order guess and was handed to the very
-    `media_meta_req` this probe leaves outstanding — the original defect, one
-    feature later, in a message type that did not exist when it was written.
-  * `_asText` had been deleted along with an unrelated helper beside it. Its
-    only caller is inside `_openChatMessage`, whose rejection the panel
-    swallows, so the whole conversation rendered empty with nothing in the
-    console and the node answering perfectly.
-
-Neither is visible in any source file, and neither would have been caught by a
-test that reads one.
 """
 import json
 import shutil
@@ -52,7 +43,7 @@ pytestmark = pytest.mark.skipif(
 
 @pytest.fixture(scope="module")
 def probe():
-    # `sys.executable`, not a bare "python3": the harness now imports
+    # `sys.executable`, not a bare "python3": the harness imports
     # `meshbay_common` to seal the chat keys the way the node does, and the
     # system interpreter has neither that nor msgpack. The other probes get
     # away with "python3" because they import nothing from this project.
@@ -60,51 +51,81 @@ def probe():
                          capture_output=True, timeout=180)
     assert run.returncode == 0, run.stderr.decode()[-2000:]
     data = json.loads(run.stdout.decode())
-    return data, {s["label"]: s for s in data["steps"]}
+    steps = {sc["name"]: {s["label"]: s for s in sc["steps"]}
+             for sc in data["scenarios"]}
+    return data, steps
+
 
+@pytest.mark.parametrize("reply", ["ack", "error"])
+def test_the_composer_comes_back(probe, reply):
+    """The one thing a person sees: the tab is usable again.
 
-def test_the_composer_comes_back(probe):
-    """The one thing a person sees: the tab is usable again."""
+    Both answers have to release it. A refusal that reaches nobody leaves the
+    composer disabled exactly as long as an acceptance that reaches nobody —
+    the composer is not waiting for good news, it is waiting for an answer.
+    """
     _, steps = probe
-    assert steps["stale request pending"]["composerDisabled"] is False, (
+    assert steps[reply]["older request pending"]["composerDisabled"] is False, (
         "the composer was already unusable before the send")
-    assert steps["after send"]["composerDisabled"] is False, (
+    assert steps[reply]["after send"]["composerDisabled"] is False, (
         "the composer is still disabled well inside the 30s request timeout -- "
         "the send never came back, which is what reads as a frozen Chat tab")
 
 
-def test_the_message_is_displayed(probe):
+def test_an_accepted_message_is_displayed(probe):
     """A sent message appears at once, not on the next visit to the tab."""
     _, steps = probe
-    before = steps["stale request pending"]["bubbles"]
-    assert steps["after send"]["bubbles"] == before + 1, (
+    before = steps["ack"]["older request pending"]["bubbles"]
+    assert steps["ack"]["after send"]["bubbles"] == before + 1, (
         "the message was not added to the conversation")
-    assert steps["after send"]["lastText"] == "hello"
-    assert steps["after send"]["composerValue"] == "", (
+    assert steps["ack"]["after send"]["lastText"] == "hello"
+    assert steps["ack"]["after send"]["composerValue"] == "", (
         "the text came back into the composer, so the send was treated as failed")
 
 
-def test_the_ack_is_not_handed_to_another_request(probe):
-    """The other half of the same defect: whatever was waiting got the ack and
-    carried on with a reply to a question it never asked."""
+def test_a_refused_message_is_not_displayed_as_sent(probe):
+    """The other direction, and the one routing this correctly makes possible.
+
+    While a refusal reached the wrong caller it did not matter what `sendChat`
+    would have done with it. Now that it arrives, a message the node rejected
+    must not appear in the conversation as though it had been stored — it must
+    come back into the composer, where a person can see it did not go.
+    """
+    _, steps = probe
+    before = steps["error"]["older request pending"]["bubbles"]
+    assert steps["error"]["after send"]["bubbles"] == before, (
+        "a refused message was added to the conversation anyway")
+    assert steps["error"]["after send"]["composerValue"] == "hello", (
+        "the refused text was dropped instead of being handed back")
+
+
+@pytest.mark.parametrize("reply", ["ack", "error"])
+def test_the_reply_is_not_handed_to_another_request(probe, reply):
+    """The other half of the same defect: whatever was waiting got the reply
+    and carried on with an answer to a question it never asked."""
     data, _ = probe
-    assert "media_meta resolved with ack" not in data["log"], (
-        "the chat ack was routed to the pending media_meta_req -- that request "
-        "now believes it has an answer, and the chat send is waiting for a "
-        "reply that already arrived")
+    stolen = [line for line in data["log"] if line.startswith(f"{reply}: music_meta")]
+    assert not stolen, (
+        f"the chat {reply} was routed to the pending music_meta_req ({stolen}) -- "
+        "that request now believes it has an answer, and the chat send is "
+        "waiting for a reply that already arrived")
 
 
-def test_the_message_goes_out_sealed_and_signed(probe):
+@pytest.mark.parametrize("reply", ["ack", "error"])
+def test_the_message_goes_out_sealed_and_signed(probe, reply):
     """
-    What actually left the browser. A composer that let a plaintext message
-    through would be refused by the node, but the refusal arrives after the
-    fact and reads as "the message did not send" — so assert the shape here,
-    where the reason is visible.
+    What actually left the browser (MNP 2.0).
+
+    Asserted for both scenarios because the composer is what decides to send:
+    a client that fell back to plaintext when something went wrong would be
+    refused by the node, but the refusal arrives after the fact and reads as
+    "the message did not send". There is no plaintext form on the wire.
     """
     data, _ = probe
-    sent = [line for line in data["log"] if line.startswith("chat_msg ")]
-    assert sent, ("no chat_msg reached the stand-in node — the send did not "
-                  f"complete. log: {data['log']}")
+    sent = [line for line in data["log"]
+            if line.startswith(f"{reply}: chat_msg ")]
+    assert sent, (f"no chat_msg reached the stand-in node in the {reply} "
+                  f"scenario — the send did not complete. log: {data['log']}")
     assert "format=1" in sent[0], "the message was not sealed"
     assert "sig=64" in sent[0], "the message was not signed"
     assert "ct=" in sent[0] and "ct=0" not in sent[0], "there was no ciphertext"
@@ -115,12 +136,25 @@ def test_the_message_goes_out_sealed_and_signed(probe):
 
 def test_the_chat_keys_answer_is_not_handed_to_another_request(probe):
     """
-    The original defect's shape, in the message type that carries the group's
-    chat keys. An unanswered request is the ordinary case, not a rare one, and
-    the one this probe leaves outstanding swallowed the keys on the first run.
+    The same defect this file exists for, in the message type that carries the
+    group's chat keys — which did not exist when it was written, and which a
+    send now depends on. It went astray on the probe's first encrypted run.
     """
     data, _ = probe
-    assert not any("media_meta resolved with chat_keys_resp" in line
-                   for line in data["log"]), (
-        "chat_keys_resp was routed by arrival order and handed to the stale "
-        "media_meta_req — the send then waits out its own 30s timeout")
+    stolen = [line for line in data["log"] if "music_meta resolved with" in line]
+    assert not stolen, (
+        f"a reply was routed to the pending music_meta_req ({stolen}) — the "
+        "send then waits out its own 30s timeout with the composer disabled")
+
+
+def test_history_still_renders(probe):
+    """
+    Not about sending at all, and here because it broke without a sound:
+    `_asText` was deleted with an unrelated helper beside it, its only caller
+    sits inside a promise the panel catches, and every conversation rendered
+    empty with the node answering perfectly.
+    """
+    _, steps = probe
+    assert steps["ack"]["older request pending"]["bubbles"] == 5, (
+        "the five history messages did not render — the panel swallows a "
+        "failure in the transport's message reader, so this is silent")
diff --git a/packages/meshbay-hub/tests/test_index_seal_client.py b/packages/meshbay-hub/tests/test_index_seal_client.py
index ca2c7a2..e1135da 100644
--- a/packages/meshbay-hub/tests/test_index_seal_client.py
+++ b/packages/meshbay-hub/tests/test_index_seal_client.py
@@ -45,10 +45,15 @@ def _frame(msg: dict) -> str:
     return (struct.pack(">I", len(body)) + body).hex()
 
 
-def _sync_frame(gek: bytes, *names: str, version: int = 3) -> str:
+def _sync_frame(gek: bytes, *names: str, version: int = 3,
+                req_id: int | None = None) -> str:
     payload = {"version": version, "entries": [_entry(n) for n in names],
                "dirs": ["library"], "roots": [{"name": "library"}]}
+    # `req_id` is what a current node stamps on a *reply*; the push it sends a
+    # newly connected peer answers no request and carries none. Both shapes
+    # arrive here, and only one of them may resolve a waiting fetchIndex.
     return _frame({"type": "index_sync", "v": "1.0", "group_id": GROUP,
+                   **({"req_id": req_id} if req_id is not None else {}),
                    **seal(gek, PURPOSE_INDEX, "index_sync", GROUP, payload)})
 
 
@@ -141,3 +146,26 @@ def test_deltas_are_applied_in_arrival_order():
     assert [e["additions"][0] for e in out["events"][1:]] == [
         "added-0.mkv", "added-1.mkv", "added-2.mkv"]
     assert [e["base_version"] for e in out["events"][1:]] == [3, 4, 5]
+
+
+def test_a_sealed_reply_is_opened_before_it_reaches_its_caller():
+    """A stamped index_sync must not be short-circuited by its `req_id`.
+
+    Every other reply a node stamps is resolved straight out of the pending
+    map, which is the whole point of the id. An index message cannot be: it is
+    sealed, opening it is asynchronous, and `_dispatch` is not. Handing it over
+    on the strength of the id alone gives `fetchIndex` the envelope — nonce and
+    ciphertext, no entries — and never calls `onIndexSync` at all.
+
+    `req_id` is 0 here because it is the transport's first request, and a
+    falsy id is exactly the one a presence check gets wrong.
+    """
+    out = _run([_sync_frame(GEK, "a-film.mkv", req_id=0)])
+
+    assert [e["event"] for e in out["events"]] == ["index_sync"], (
+        "the consumer was never told about an index that arrived as a reply")
+    assert out["events"][0]["entries"] == ["a-film.mkv"]
+    assert out["events"][0]["hasCiphertext"] is False
+    assert out["fetchIndex"]["state"] == "resolved"
+    assert out["fetchIndex"]["entries"] == ["a-film.mkv"], (
+        "the caller was handed the sealed envelope instead of the index")
diff --git a/packages/meshbay-hub/tests/test_transport_contracts.py b/packages/meshbay-hub/tests/test_transport_contracts.py
index b462242..879062b 100644
--- a/packages/meshbay-hub/tests/test_transport_contracts.py
+++ b/packages/meshbay-hub/tests/test_transport_contracts.py
@@ -307,26 +307,60 @@ def test_no_setter_survives_the_state_it_belonged_to():
 
 # ── Parallel uploads ──────────────────────────────────────────────────────────
 
-def test_an_upload_refusal_names_the_file_it_is_about(transport):
+def test_an_upload_refusal_names_the_upload_it_is_about(transport):
     """Reported 2026-08-16: a second upload started in parallel killed both.
 
-    An error used to carry no filename, so the client could not tell whose it
-    was and failed every upload in flight — one name the node disliked took the
-    other file with it. The node names the file now, and only that upload stops.
+    An error used to carry nothing identifying, so the client could not tell
+    whose it was and failed every upload in flight — one name the node disliked
+    took the other file with it.
+
+    The node named the *file* until MNP 2.0 and names the `upload_id` now: the
+    filename moved inside the seal, and echoing it in clear so the two sides
+    could match on it would give back precisely what sealing the upload is for.
+    The property is unchanged — one refusal, one failed upload.
     """
     body = transport[transport.index("if (msg.type === 'error' && this._uploaders.size)"):]
     body = body[:body.index("\n    if (msg.type === 'chat_msg'")]
-    assert "this._uploaders.has(msg.filename)" in body, (
+    assert "this._uploaders.has(msg.upload_id)" in body, (
         "a named refusal must reach one uploader, not all of them")
-    assert "if (!msg.filename)" in body, (
+    assert "if (!msg.upload_id)" in body, (
         "an unnamed error from an older node must still stop everything — "
         "guessing which upload it belongs to would be worse")
 
 
-def test_uploads_are_tracked_per_file(transport):
+def test_uploads_are_tracked_per_upload(transport):
     """Acks interleave when two files are in flight."""
     assert "this._uploaders = new Map()" in transport
-    assert "this._uploaders.set(file.name" in transport
+    assert "this._uploaders.set(uploadId" in transport
+    # And the "already being uploaded" guard still speaks in filenames, because
+    # that is what the caller passed and what it would recognise in the error.
+    assert "this._inFlightUploads.has(file.name)" in transport
+
+
+def test_the_upload_itself_is_sealed(transport):
+    """
+    MNP 2.0. The filename, the destination and the bytes go inside the seal
+    together — sealing the content and announcing the name beside it would be
+    theatre — and only what the node routes on stays outside.
+    """
+    start = transport.index("  async uploadFile(file,")
+    body = transport[start:transport.index("\n  /** Create a directory", start)]
+    assert "sealGroup(" in body and "'file_upload'" in body, (
+        "the upload must be sealed under the group key")
+    assert "openGroup(" in body and "'file_upload_ack'" in body, (
+        "the ack carries the stored name and must be opened, not read")
+    # The message the node actually receives: everything between `this._send({`
+    # and its close. Read on its own, because the same field names appear a few
+    # lines above inside `msgpack_encode({...})`, which is the sealed half.
+    sent = body[body.index("this._send({"):]
+    sent = sent[:sent.index("});")]
+    assert "filename" not in sent, "the filename is on the message in clear"
+    assert "data" not in sent, "the bytes are on the message in clear"
+    assert "dir" not in sent and "root" not in sent, (
+        "the destination is on the message in clear")
+    assert "...sealed," in sent, "the message must carry the sealed pair"
+    assert "supportsSealedUpload" in body, (
+        "an older node must be refused before a chunk is sent, not after")
 
 
 # ── MNP 1.0: the sealed handshake ack ────────────────────────────────────────
diff --git a/packages/meshbay-hub/tests/test_upload_seal_client.py b/packages/meshbay-hub/tests/test_upload_seal_client.py
new file mode 100644
index 0000000..d6f9156
--- /dev/null
+++ b/packages/meshbay-hub/tests/test_upload_seal_client.py
@@ -0,0 +1,169 @@
+"""
+The browser half of MNP 2.0's sealed upload, measured rather than read.
+
+`test_upload_sealed.py` (node side) proves the node opens what the shared
+encoder produces and refuses everything else. This proves the *shipped browser
+code* produces it — and, the part that matters more, that a caller of
+`uploadFile` is still told the name the node stored the file under, which now
+arrives sealed and would otherwise be `undefined` with nothing on screen to say
+so: a chat attachment would point at a file that is not there.
+
+Driven through `harness/upload_seal_probe.mjs`, which runs the shipped
+`transport.js` over the shipped `crypto.js`. The node half in between is the
+real `_do_file_upload`, writing to a real directory.
+
+A source-reading test can see that `sealGroup` is called. Only this can see
+whether what comes out of it opens.
+"""
+
+import json
+import shutil
+import subprocess
+import tempfile
+from pathlib import Path
+
+import msgpack
+import pytest
+from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey
+from meshbay_common.crypto import generate_gek
+from meshbay_common.protocol import MNP
+from meshbay_node.indexer.group_index import GroupIndex
+from meshbay_node.roots import RootSet
+from meshbay_node.transport.webrtc_server import WebRTCPeerSession
+
+STATIC = Path(__file__).resolve().parents[1] / "src" / "meshbay_hub" / "static"
+PROBE = Path(__file__).resolve().parent / "harness" / "upload_seal_probe.mjs"
+
+pytestmark = pytest.mark.skipif(
+    shutil.which("node") is None or not PROBE.exists(),
+    reason="node unavailable — the client half cannot be measured",
+)
+
+GROUP = "g-upload-probe"
+CHUNK = 32
+BODY = bytes(range(256)) * 3          # 768 bytes → 24 chunks of 32
+
+
+def _run_probe(payload: dict) -> dict:
+    with tempfile.TemporaryDirectory() as d:
+        f = Path(d) / "input.json"
+        f.write_text(json.dumps(payload))
+        proc = subprocess.run(
+            ["node", str(PROBE), str(STATIC), str(f)],
+            capture_output=True, text=True, timeout=60,
+        )
+    if proc.returncode != 0 or not proc.stdout:
+        pytest.fail(f"upload probe failed:\n{proc.stderr}")
+    return json.loads(proc.stdout)
+
+
+def _node_session(tmp_path: Path, gek: bytes) -> WebRTCPeerSession:
+    root = tmp_path / "library"
+    root.mkdir()
+    index = GroupIndex(group_id=GROUP, sk_node=Ed25519PrivateKey.generate())
+    session = WebRTCPeerSession.__new__(WebRTCPeerSession)
+    session._ctx = {
+        "roots": RootSet.build([{"path": str(root), "name": "library",
+                                 "writable": True}]),
+        "index": index, "sk_node": index.sk_node, "gek": gek,
+    }
+    session._group_id = GROUP
+    session._user_id = "prober"
+    session._pk_user = ""
+    session._uploads = {}
+    session.sent = []
+    session._send = session.sent.append
+    session._audit = lambda *a, **k: None
+    return session
+
+
+def _probe_input(gek: bytes, mode: str, **extra) -> dict:
+    return {
+        "mode": mode, "gek": gek.hex(), "group_id": GROUP,
+        "node_version": "2.0", "chunk_size": CHUNK, "dir": "library",
+        "root": "library",
+        "file": {"name": "holiday.jpg", "data": BODY.hex()},
+        **extra,
+    }
+
+
+@pytest.fixture(scope="module")
+def _gek():
+    return generate_gek()
+
+
+@pytest.fixture(scope="module")
+def _sent(_gek):
+    """Every frame the shipped `uploadFile` puts on the wire, unanswered."""
+    return _run_probe(_probe_input(_gek, "send"))
+
+
+def test_the_browser_puts_no_filename_and_no_content_on_the_wire(_sent):
+    """The whole point, measured on the bytes rather than read off the source."""
+    assert _sent["frames"], "the client sent nothing"
+    for hexframe in _sent["frames"]:
+        raw = bytes.fromhex(hexframe)
+        assert b"holiday.jpg" not in raw, "the filename is on the wire in clear"
+        msg = msgpack.unpackb(raw, raw=False)
+        assert set(msg) == {"type", "v", "upload_id", "chunk_index",
+                            "total_chunks", "nonce", "ct"}
+        assert msg["type"] == MNP.FILE_UPLOAD
+
+
+def test_a_real_node_opens_what_the_real_browser_sealed(tmp_path, _gek, _sent):
+    """
+    End to end: the shipped browser encoder into the shipped node handler, with
+    the file that lands on disk as the assertion. A mismatch in the HKDF salt,
+    the AAD encoding or the payload shape shows up here as "did not open" — and
+    nowhere else until somebody tries to upload something.
+    """
+    session = _node_session(tmp_path, _gek)
+    for hexframe in _sent["frames"]:
+        session._do_file_upload(msgpack.unpackb(bytes.fromhex(hexframe), raw=False))
+
+    errors = [m for m in session.sent if m.get("type") == "error"]
+    assert not errors, f"the node refused a frame the browser built: {errors[:1]}"
+
+    root = session._ctx["roots"].roots[0].path
+    assert (root / "holiday.jpg").read_bytes() == BODY
+    assert not list(root.glob("*.part")), "a temp file was left behind"
+
+
+def test_the_caller_is_told_the_name_the_node_chose(tmp_path, _gek, _sent):
+    """
+    `stored_as` is sealed now, so reading it takes a decrypt that can fail
+    silently. It must not: the node finds a free name rather than replacing
+    anything, and a chat attachment that never learns which name points at
+    nothing.
+
+    The acks below are the ones the node really produced — only their
+    `upload_id`, which is outside the seal, is retargeted to the second probe
+    run's own upload.
+    """
+    session = _node_session(tmp_path, _gek)
+    # A file of that name is already there, so the node has to choose another.
+    (session._ctx["roots"].roots[0].path / "holiday.jpg").write_bytes(b"someone else's")
+
+    for hexframe in _sent["frames"]:
+        session._do_file_upload(msgpack.unpackb(bytes.fromhex(hexframe), raw=False))
+    acks = [msgpack.packb(m, use_bin_type=True).hex()
+            for m in session.sent if m.get("type") == MNP.FILE_UPLOAD_ACK]
+    assert len(acks) == len(_sent["frames"])
+
+    result = _run_probe(_probe_input(_gek, "receive", acks=acks))
+    assert result["state"] == "resolved", result.get("message")
+    assert result["stored"]["stored_as"] == "holiday (2).jpg"
+    assert result["stored"]["dir"] == "library"
+
+
+def test_the_client_refuses_an_older_node_before_sending_a_chunk(_gek):
+    """
+    A 1.x node would answer "Missing filename or data" — an error about the
+    wrong thing, naming no upload, which fails every upload in flight. Asked
+    first instead, and nothing goes on the wire.
+    """
+    result = _run_probe(_probe_input(_gek, "receive", acks=[],
+                                     node_version="1.1"))
+    assert result["state"] == "rejected"
+    assert "older MeshBay" in result["message"]
+    assert result["frames"] == [], "a chunk was sent to a node that cannot open it"