Optional replyId on send (API + MCP) — protocol-level threaded replies (#31)

src/mesh/codec.spec.ts

@@ -1,5 +1,7 @@
+import { fromBinary, toBinary } from '@bufbuild/protobuf';
+import * as P from '@meshtastic/protobufs';
 import { describe, expect, it } from 'vitest';
-import { extractFrames, frame } from './codec.js';
+import { buildTextToRadio, extractFrames, frame } from './codec.js';
 
 const F = (payload: number[]) => [
   0x94,
@@ -78,3 +80,25 @@ describe('frame', () => {
     expect(rest.length).toBe(0);
   });
 });
+
+// re-serialize just the nested Data message so its wire bytes are inspectable without the random packet id interfering
+function dataBytes(framed: Uint8Array): Uint8Array {
+  const { packets } = extractFrames(framed); // buildTextToRadio returns framed bytes
+  expect(packets).toHaveLength(1);
+  const tr = fromBinary(P.Mesh.ToRadioSchema, packets[0]);
+  if (tr.payloadVariant?.case !== 'packet') throw new Error('not a packet');
+  const pv = tr.payloadVariant.value.payloadVariant;
+  if (pv?.case !== 'decoded') throw new Error('not decoded');
+  return toBinary(P.Mesh.DataSchema, pv.value);
+}
+
+describe('buildTextToRadio', () => {
+  it('writes wire tag 0x3d (Data.reply_id, field 7) iff replyId is given', async () => {
+    const withReply = await buildTextToRadio(42, 'hi', 3, 42);
+    expect(Array.from(dataBytes(withReply.bytes))).toContain(0x3d);
+
+    // omitting it must leave the field off the wire (proto3 default 0) — snake_case reply_id would be silently dropped here
+    const plain = await buildTextToRadio(42, 'hi', 3);
+    expect(Array.from(dataBytes(plain.bytes))).not.toContain(0x3d);
+  });
+});