diff --git a/src/helpers/ota/MotaSourceSerial.cpp b/src/helpers/ota/MotaSourceSerial.cpp
new file mode 100644
index 00000000..9b302329
--- /dev/null
+++ b/src/helpers/ota/MotaSourceSerial.cpp
@@ -0,0 +1,96 @@
+#include "MotaSourceSerial.h"
+#include "MotaSeederProto.h"
+#include "OtaByteIO.h"
+#include <string.h>
+
+namespace mesh {
+namespace ota {
+
+bool SerialMotaSource::readByteT(uint8_t& b) {
+  uint32_t t0 = millis();
+  while ((millis() - t0) < _to) {
+    int c = _io.read();
+    if (c >= 0) { b = (uint8_t)c; return true; }
+  }
+  return false;
+}
+
+bool SerialMotaSource::readExact(uint8_t* b, uint32_t n) {
+  for (uint32_t i = 0; i < n; i++) if (!readByteT(b[i])) return false;
+  return true;
+}
+
+// One request/response transaction. Resync-safe: drains stale input, frames the request with an XOR
+// checksum, then scans for the response magic and validates op+status+checksum before delivering payload.
+bool SerialMotaSource::txn(uint8_t op, const uint8_t* args, uint8_t arglen,
+                           uint8_t* payload, uint32_t payload_len) {
+  while (_io.read() >= 0) {}                       // drop any stale/partial bytes before a fresh request
+  uint8_t xs = op;
+  for (uint8_t i = 0; i < arglen; i++) xs ^= args[i];
+  _io.write(MOTA_SEEDER_REQ_MAGIC0); _io.write(MOTA_SEEDER_REQ_MAGIC1);
+  _io.write(op);
+  if (arglen) _io.write(args, arglen);
+  _io.write(xs);
+  _io.flush();
+
+  // scan for response magic 'm' 's' (tolerate leading noise)
+  uint32_t t0 = millis(); bool got = false;
+  uint8_t prev = 0;
+  while ((millis() - t0) < _to) {
+    int c = _io.read();
+    if (c < 0) continue;
+    if (prev == MOTA_SEEDER_RSP_MAGIC0 && (uint8_t)c == MOTA_SEEDER_RSP_MAGIC1) { got = true; break; }
+    prev = (uint8_t)c;
+  }
+  if (!got) return false;
+
+  uint8_t hdr[2];
+  if (!readExact(hdr, 2)) return false;            // op, status
+  if (hdr[0] != op) return false;
+  uint8_t rxs = (uint8_t)(MOTA_SEEDER_RSP_MAGIC0 ^ MOTA_SEEDER_RSP_MAGIC1) ^ hdr[0] ^ hdr[1];
+  bool ok = (hdr[1] == MS_STATUS_OK);
+  if (ok && payload_len) {
+    if (!readExact(payload, payload_len)) return false;
+    for (uint32_t i = 0; i < payload_len; i++) rxs ^= payload[i];
+  }
+  uint8_t xsum;
+  if (!readByteT(xsum)) return false;
+  if (xsum != rxs) return false;                   // corrupt frame -> caller retries
+  return ok;
+}
+
+uint8_t SerialMotaSource::count() {
+  uint8_t n = 0;
+  if (!txn(MS_OP_COUNT, nullptr, 0, &n, 1)) return 0;
+  return n;
+}
+
+bool SerialMotaSource::describe(uint8_t idx, MotaDesc& out) {
+  uint8_t args[1] = { idx };
+  uint8_t w[MOTA_DESC_WIRE];
+  if (!txn(MS_OP_DESCRIBE, args, 1, w, MOTA_DESC_WIRE)) return false;
+  memcpy(out.mid, w, 4);
+  out.target_id    = rd_u32le(w + 4);
+  out.fw_version   = rd_u32le(w + 8);
+  out.codec_id     = w[12];
+  out.flags        = w[13];
+  out.total_size   = rd_u32le(w + 14);
+  out.leaves_off   = rd_u32le(w + 18);
+  out.block_count  = rd_u32le(w + 22);
+  out.payload_off  = rd_u32le(w + 26);
+  out.payload_size = rd_u32le(w + 30);
+  // bytes [34,38) reserved (zero) — kept for forward compat without changing MOTA_DESC_WIRE
+  return true;
+}
+
+bool SerialMotaSource::read(uint8_t idx, uint32_t off, uint8_t* buf, uint32_t len) {
+  if (len > 0xFFFF) return false;                  // single transaction caps at 64 KB (a block is <=1 KB)
+  uint8_t args[7];
+  args[0] = idx;
+  wr_u32le(args + 1, off);
+  args[5] = (uint8_t)(len & 0xFF); args[6] = (uint8_t)(len >> 8);
+  return txn(MS_OP_READ, args, 7, buf, len);
+}
+
+} // namespace ota
+} // namespace mesh
diff --git a/src/helpers/ota/MotaSourceSerial.h b/src/helpers/ota/MotaSourceSerial.h
new file mode 100644
index 00000000..26b9e298
--- /dev/null
+++ b/src/helpers/ota/MotaSourceSerial.h
@@ -0,0 +1,35 @@
+#pragma once
+
+#include <Arduino.h>
+#include "OtaSource.h"
+
+// A MotaSource backed by a host "mota-seeder" daemon over a dedicated Stream (a spare UART / USB-UART).
+// The device pulls catalog + bytes on demand (MotaSeederProto.h); the folder image is never held on the
+// device — it streams through. Use a stream that is NOT the text-CLI console so the binary framing never
+// collides with command/log text. Reads block on the Stream up to `timeout_ms` (OTA is lowest priority,
+// so a serial round-trip's latency is acceptable; keep the daemon on a fast link).
+
+namespace mesh {
+namespace ota {
+
+class SerialMotaSource : public MotaSource {
+public:
+  explicit SerialMotaSource(Stream& io, uint32_t timeout_ms = 400) : _io(io), _to(timeout_ms) {}
+
+  uint8_t count() override;
+  bool    describe(uint8_t idx, MotaDesc& out) override;
+  bool    read(uint8_t idx, uint32_t off, uint8_t* buf, uint32_t len) override;
+
+private:
+  // Send a request (op+args) and read its response header; on OK, `payload` (if non-null) receives
+  // `payload_len` bytes. Returns true iff a well-formed OK response for `op` arrived in time.
+  bool txn(uint8_t op, const uint8_t* args, uint8_t arglen, uint8_t* payload, uint32_t payload_len);
+  bool readByteT(uint8_t& b);          // one byte within the timeout
+  bool readExact(uint8_t* b, uint32_t n);
+
+  Stream&  _io;
+  uint32_t _to;
+};
+
+} // namespace ota
+} // namespace mesh