1 files changed, 23 insertions, 2 deletions
diff --git a/packages/meshbay-hub/tests/harness/upload_seal_probe.mjs b/packages/meshbay-hub/tests/harness/upload_seal_probe.mjs
index 0b77e42..a6008c2 100644
--- a/packages/meshbay-hub/tests/harness/upload_seal_probe.mjs
+++ b/packages/meshbay-hub/tests/harness/upload_seal_probe.mjs
@@ -72,13 +72,34 @@ tp._nodeVersion = input.node_version;
 
 const frames = [];
 let uploadId = null;
+let answered = 0;
 tp._send = (msg) => {
   frames.push(toHex(msgpack_encode(msg)));
   if (msg.upload_id) uploadId = msg.upload_id;
-  if (input.mode !== 'receive') return;
+  if (input.mode !== 'receive') {
+    // Nothing answers in this mode -- except the probe, which the client waits
+    // five seconds for. A node that predates it refuses the index, and that
+    // refusal is a plain error rather than a sealed ack, so the harness can
+    // produce it honestly. It is also the degradation path worth exercising.
+    if (msg.chunk_index === -1) {
+      // With `probe_ack`, answer it the way a node holding part of this file
+      // does; without, the way one that predates the probe does.
+      const reply = input.probe_ack
+        ? Object.assign(msgpack_decode(hex(input.probe_ack)),
+                        { upload_id: uploadId })
+        : { type: 'error', upload_id: uploadId,
+            code: 'bad_chunk_index', detail: 'Unexpected chunk index' };
+      setImmediate(() => tp._dispatch(reply));
+    }
+    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]));
+  //
+  // By position, not by `chunk_index`: the node answers every frame including
+  // the probe, whose index is -1, and the two lists are built from the same
+  // sequence of frames.
+  const ack = msgpack_decode(hex(input.acks[answered++]));
   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.