Fix TrueNAS system info buildtime decoding

Fixes #1469

docs/release-control/v6/internal/subsystems/monitoring.md

@@ -767,6 +767,12 @@ stopping at disconnected toast notifications.
 That same runtime owner also defines the feature-default contract for TrueNAS:
 the API-backed integration is on by default, and `PULSE_ENABLE_TRUENAS` is an
 explicit opt-out switch rather than a required bootstrap toggle.
+That same TrueNAS monitoring boundary owns system identity compatibility for
+`/system/info`. `internal/truenas/client.go` must tolerate provider-version
+drift in non-identity display fields such as `buildtime`, including structured
+date/value wrappers, and still preserve the canonical hostname, version,
+machine ID, capacity, and poll-health path instead of failing connection tests
+or background refreshes during JSON decoding.
 That same monitoring boundary now also owns live TrueNAS disk temperatures.
 `internal/truenas/client.go` and `internal/truenas/provider.go` must ingest
 `disk.temperatures` from the TrueNAS API, fall back to modern

internal/truenas/client.go

@@ -158,7 +158,7 @@ func (c *Client) GetSystemInfo(ctx context.Context) (*SystemInfo, error) {
 		machineID = strings.TrimSpace(response.Hostname)
 	}
 
-	build := strings.TrimSpace(response.BuildTime)
+	build := strings.TrimSpace(response.BuildTime.String())
 	if build == "" {
 		build = strings.TrimSpace(response.Version)
 	}
@@ -2868,15 +2868,30 @@ func normalizeFingerprint(fingerprint string) (string, error) {
 }
 
 type systemInfoResponse struct {
-	Hostname      string `json:"hostname"`
-	Version       string `json:"version"`
-	BuildTime     string `json:"buildtime"`
-	UptimeSeconds int64  `json:"uptime_seconds"`
-	SystemSerial  string `json:"system_serial"`
-	SystemVendor  string `json:"system_manufacturer"`
-	Cores         int    `json:"cores"`
-	PhysicalCores int    `json:"physical_cores"`
-	Physmem       int64  `json:"physmem"`
+	Hostname      string            `json:"hostname"`
+	Version       string            `json:"version"`
+	BuildTime     textResponseField `json:"buildtime"`
+	UptimeSeconds int64             `json:"uptime_seconds"`
+	SystemSerial  string            `json:"system_serial"`
+	SystemVendor  string            `json:"system_manufacturer"`
+	Cores         int               `json:"cores"`
+	PhysicalCores int               `json:"physical_cores"`
+	Physmem       int64             `json:"physmem"`
+}
+
+type textResponseField string
+
+func (f textResponseField) String() string {
+	return string(f)
+}
+
+func (f *textResponseField) UnmarshalJSON(data []byte) error {
+	value, err := parseTextResponseField(data)
+	if err != nil {
+		return err
+	}
+	*f = textResponseField(value)
+	return nil
 }
 
 type poolResponse struct {
@@ -3068,6 +3083,34 @@ func readStringAny(record map[string]any, keys ...string) string {
 	return ""
 }
 
+func parseTextResponseField(raw json.RawMessage) (string, error) {
+	trimmed := bytes.TrimSpace(raw)
+	if len(trimmed) == 0 || bytes.Equal(trimmed, []byte("null")) {
+		return "", nil
+	}
+
+	var decoded any
+	decoder := json.NewDecoder(bytes.NewReader(trimmed))
+	decoder.UseNumber()
+	if err := decoder.Decode(&decoded); err != nil {
+		return "", err
+	}
+	return textFromDecodedAny(decoded), nil
+}
+
+func textFromDecodedAny(value any) string {
+	switch typed := value.(type) {
+	case string:
+		return strings.TrimSpace(typed)
+	case json.Number:
+		return strings.TrimSpace(typed.String())
+	case map[string]any:
+		return readStringAny(typed, "rawvalue", "value", "parsed", "$date", "date", "datetime", "text", "string")
+	default:
+		return ""
+	}
+}
+
 func readStringSliceAny(record map[string]any, keys ...string) []string {
 	if record == nil {
 		return nil

internal/truenas/client_test.go

@@ -172,6 +172,24 @@ func TestClientAuthHeaderBasic(t *testing.T) {
 	}
 }
 
+func TestGetSystemInfoAcceptsStructuredBuildTime(t *testing.T) {
+	server := newMockServer(t, map[string]apiResponse{
+		"/api/v2.0/system/info": {
+			body: `{"hostname":"nas","version":"TrueNAS-SCALE-25.10.3.1","buildtime":{"$date":"2026-05-14T18:24:01+02:00"},"uptime_seconds":1}`,
+		},
+	}, nil)
+	t.Cleanup(server.Close)
+
+	client := mustClientForServer(t, server.URL, ClientConfig{APIKey: "test-key"})
+	system, err := client.GetSystemInfo(context.Background())
+	if err != nil {
+		t.Fatalf("GetSystemInfo() error = %v", err)
+	}
+	if system.Build != "2026-05-14T18:24:01+02:00" {
+		t.Fatalf("Build = %q, want structured buildtime date", system.Build)
+	}
+}
+
 func TestTestConnectionSuccessAndFailure(t *testing.T) {
 	successServer := newMockServer(t, map[string]apiResponse{
 		"/api/v2.0/system/info": {body: `{"hostname":"nas","version":"v","buildtime":"b","uptime_seconds":1}`},