diff --git a/firmware/include/msgpack.h b/firmware/include/msgpack.h
index 424d360..dda3aaa 100644
--- a/firmware/include/msgpack.h
+++ b/firmware/include/msgpack.h
@@ -773,6 +773,13 @@ inline result<parser> unpack(const parser &p, std::vector<uint8_t> &out) {
   return p.next();
 }
 
+inline result<parser> unpack(const parser &p, std::span<const uint8_t> &out) {
+  auto v = p.get_binary_view();
+  if (!v) return std::unexpected(v.error());
+  out = std::span<const uint8_t>(reinterpret_cast<const uint8_t*>(v->data()), v->size());
+  return p.next();
+}
+
 template <typename T>
   requires (!std::is_same_v<T, uint8_t>)
 result<parser> unpack(const parser &p, std::vector<T> &out) {
diff --git a/firmware/include/wire.h b/firmware/include/wire.h
index d76f230..15e751d 100644
--- a/firmware/include/wire.h
+++ b/firmware/include/wire.h
@@ -13,7 +13,7 @@ struct Envelope {
     static constexpr int8_t ext_id = 0;
     uint32_t message_id;
     uint32_t checksum;
-    std::vector<uint8_t> payload;
+    std::span<const uint8_t> payload;
     auto as_tuple() const { return std::tie(message_id, checksum, payload); }
     auto as_tuple() { return std::tie(message_id, checksum, payload); }
 };
@@ -94,7 +94,7 @@ static constexpr uint8_t hash_key[8] = {};
 struct DecodedMessage {
     uint32_t message_id;
     int8_t type_id;
-    std::vector<uint8_t> payload;
+    std::span<const uint8_t> payload;
 };
 
 static constexpr size_t ext16_header_len = 4;
@@ -151,8 +151,7 @@ inline msgpack::result<DecodedMessage> try_decode(const uint8_t *data, size_t le
 
     auto& [type_id, ext_data] = *ext;
     return DecodedMessage{env.message_id, type_id,
-        std::vector<uint8_t>(reinterpret_cast<const uint8_t*>(ext_data.data()),
-                             reinterpret_cast<const uint8_t*>(ext_data.data()) + ext_data.size())};
+        std::span<const uint8_t>(reinterpret_cast<const uint8_t*>(ext_data.data()), ext_data.size())};
 }
 
 template <size_t N>
diff --git a/firmware/lib/dispatch.cpp b/firmware/lib/dispatch.cpp
index 5b6ecef..f9f301a 100644
--- a/firmware/lib/dispatch.cpp
+++ b/firmware/lib/dispatch.cpp
@@ -59,12 +59,11 @@ void dispatch_schedule_ms(uint32_t ms, std::function<void()> fn) {
                 continue;
             }
 
-            usb_rx_buf.clear();
-
             auto it = handler_map.find(msg->type_id);
-            if (it == handler_map.end()) continue;
+            if (it == handler_map.end()) { usb_rx_buf.clear(); continue; }
             span_writer out(tx_buf);
             auto resp = it->second(msg->message_id, msg->payload, out);
+            usb_rx_buf.clear();
             if (!resp || *resp == 0) continue;
             size_t resp_len = *resp;
             if (resp_len <= usb.tx.free()) {