Fix BigInt serialization in GET /api/device (500 on real hardware) (#14)

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## v0.7.1 — 2026-09-24 21:10
+
+- Fix `GET /api/device` and MCP `device_info` crashing with `TypeError: Do not know how to serialize a BigInt` on live hardware (fw 2.7.15): protobuf-es decodes proto `uint64` fields as native JS `bigint`, which Express' `res.json`/`JSON.stringify` reject, and `MeshService.deviceInfo()` passed raw decoded proto objects through unconverted. Known affected fields: `Config.PowerConfig.powermonEnables` (in `localConfig.power`) and host-metrics byte counters (`freememBytes`/`diskfree*`).
+- Fix at the single choke point: one small recursive converter (`jsonSafe`, bigint → decimal string, plain objects/arrays/primitives pass through) applied in `deviceInfo()` to everything that comes from raw decoded proto messages — DeviceMetadata plus every localConfig and moduleConfig section. No per-field patching; any uint64 field in those messages is covered generically. Values that were bigint now serialize as strings (e.g. `"powermonEnables": "123"`); no other endpoint/shape changes, redaction logic untouched.
+- Tests: new device-info spec feeds a power config section frame with `powermonEnables` set to a real bigint through the fake bridge and asserts the value comes back as its string form (`"123"`) and that `JSON.stringify(deviceInfo())` succeeds — the old fixtures never set a uint64 field, which is why this slipped past the suite.
+
 ## v0.7.0 — 2026-09-24 20:21
 
 - New `GET /api/device` endpoint (and matching MCP tool `device_info`, now seven tools): device info captured during the initial sync — this device's node number, firmware version and metadata (`meshtastic.DeviceMetadata` as-is; it carries no key material), plus per-section config and module-config messages keyed by section name. In-memory only, reset on every bridge reconnect like channels/nodes.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "mesh-bot",
-  "version": "0.7.0",
+  "version": "0.7.1",
   "description": "",
   "author": "",
   "private": true,

src/mesh/mesh.service.spec.ts

@@ -718,6 +718,32 @@ describe('MeshService device info', () => {
     }
   });
 
+  it('serializes proto uint64 fields as strings (JSON-safe)', async () => {
+    const bridge = await startBridge();
+    process.env.MESH_HOST = '127.0.0.1';
+    process.env.MESH_PORT = String(bridge.port);
+    const svc = new MeshService();
+    try {
+      svc.onModuleInit();
+      await waitFor(
+        () => bridge.sockets.length === 1 && svc.status().connected,
+      );
+
+      // powermonEnables is a proto uint64 — protobuf-es decodes it as native bigint
+      bridge.sockets[0].write(
+        configSectionFrame('power', { powermonEnables: 123n }),
+      );
+
+      await waitFor(() => svc.deviceInfo().localConfig.power !== undefined);
+      const info = svc.deviceInfo();
+      expect(info.localConfig.power?.powermonEnables).toBe('123'); // bigint -> decimal string
+      expect(() => JSON.stringify(info)).not.toThrow(); // no "Do not know how to serialize a BigInt"
+    } finally {
+      svc.onModuleDestroy();
+      bridge.close();
+    }
+  });
+
   it('summarizes NodeInfo snr/hopsAway/viaMqtt when present', async () => {
     const bridge = await startBridge();
     process.env.MESH_HOST = '127.0.0.1';

src/mesh/mesh.service.ts

@@ -76,6 +76,19 @@ export interface DeviceInfo {
   moduleConfig: Record<string, Record<string, unknown>>;
 }
 
+// protobuf-es decodes proto uint64 fields as native bigint, which JSON.stringify rejects;
+// recursively convert so deviceInfo() output is always JSON-safe (bigint -> decimal string)
+function jsonSafe<T>(value: T): T {
+  if (typeof value === 'bigint') return String(value) as T;
+  if (Array.isArray(value)) return value.map(jsonSafe) as T;
+  if (value !== null && typeof value === 'object') {
+    const out: Record<string, unknown> = {};
+    for (const [k, v] of Object.entries(value)) out[k] = jsonSafe(v);
+    return out as T;
+  }
+  return value; // primitives + undefined pass through
+}
+
 // key material must never leave the process — replaced with a marker so callers can see the field exists
 const REDACTED = 'REDACTED';
 /** Config sections that carry secrets: security (PKI keys) and network (wifi psk). */
@@ -170,7 +183,8 @@ export class MeshService implements OnModuleInit, OnModuleDestroy {
    * metadata (DeviceMetadata as-is — it carries no key material), plus per-section config and
    * module-config messages keyed by section name. In-memory only; empty until the sync completes,
    * reset on every bridge reconnect. Key material is redacted: security publicKey/privateKey/adminKey
-   * and network wifiPsk are replaced with "REDACTED" — never exposed over HTTP.
+   * and network wifiPsk are replaced with "REDACTED" — never exposed over HTTP. Proto uint64 fields
+   * (e.g. power.powermonEnables) come back as decimal strings so the output always JSON-serializes.
    */
   deviceInfo(): DeviceInfo {
     const out: DeviceInfo = {
@@ -180,12 +194,12 @@ export class MeshService implements OnModuleInit, OnModuleDestroy {
     };
     if (this.metadata) {
       out.firmwareVersion = this.metadata.firmwareVersion;
-      out.metadata = this.metadata;
+      out.metadata = jsonSafe(this.metadata);
     }
     for (const [name, value] of this.configSections)
-      out.localConfig[name] = redactSection(name, value);
+      out.localConfig[name] = jsonSafe(redactSection(name, value));
     for (const [name, value] of this.moduleConfigSections)
-      out.moduleConfig[name] = value;
+      out.moduleConfig[name] = jsonSafe(value);
     return out;
   }