diff --git a/internal/catalog/catalog.go b/internal/catalog/catalog.go
index 1b50445..bddb98a 100644
--- a/internal/catalog/catalog.go
+++ b/internal/catalog/catalog.go
@@ -2,8 +2,10 @@ package catalog
 
 import (
 	"errors"
+	"fmt"
 	"io/fs"
 	"log"
+	"math"
 	"net/url"
 	"os"
 	"path"
@@ -276,6 +278,13 @@ type DockerConfig struct {
 	// container health cannot see. For services with no collector it is the only
 	// signal there is.
 	HealthSignals []HealthSignal `json:"healthSignals" yaml:"health_signals"`
+	// HealthProbe is the web catalog's docker.health_probe block: a read-only command
+	// the web worker runs inside a running node, with regex checks on its answer
+	// (Mysterium's monitoring status and recent sessions). Neither schema file
+	// describes it yet. Desktop parses it so the field round-trips and the
+	// strict-decode test passes, and does not act on it. The loader makes it
+	// JSON-safe (see jsonSafe), since the service list crosses the Wails bridge.
+	HealthProbe map[string]any `json:"healthProbe,omitempty" yaml:"health_probe"`
 	// AdvertisedAddressEnv names the ONE env var holding the address the network
 	// dials this service back at, so it can be compared against the machine's
 	// current egress address. Only that variable is ever copied out; the rest may
@@ -516,6 +525,39 @@ func normalize(svc *Service) {
 		svc.SupportURL = ""
 	}
 	svc.Docker.HealthSignals = normalizeSignals(svc.Slug, svc.Docker.HealthSignals)
+	if svc.Docker.HealthProbe != nil {
+		svc.Docker.HealthProbe = jsonSafe(svc.Docker.HealthProbe).(map[string]any)
+	}
+}
+
+// jsonSafe turns the map[any]any that yaml.v3 produces for a nested mapping with a
+// non-string key (an unquoted number, say) into map[string]any, and a .nan, .inf or
+// -.inf into its string form ("NaN", "+Inf", "-Inf"). encoding/json refuses both,
+// and one such value would fail the whole service list on its way to the UI.
+func jsonSafe(v any) any {
+	switch t := v.(type) {
+	case map[string]any:
+		for k, e := range t {
+			t[k] = jsonSafe(e)
+		}
+		return t
+	case map[any]any:
+		m := make(map[string]any, len(t))
+		for k, e := range t {
+			m[fmt.Sprint(k)] = jsonSafe(e)
+		}
+		return m
+	case []any:
+		for i, e := range t {
+			t[i] = jsonSafe(e)
+		}
+		return t
+	case float64:
+		if math.IsNaN(t) || math.IsInf(t, 0) {
+			return fmt.Sprint(t)
+		}
+	}
+	return v
 }
 
 // normalizeSignals lowercases each state and drops the signals the web catalog
diff --git a/internal/catalog/health_probe_test.go b/internal/catalog/health_probe_test.go
new file mode 100644
index 0000000..38bb665
--- /dev/null
+++ b/internal/catalog/health_probe_test.go
@@ -0,0 +1,73 @@
+package catalog
+
+import (
+	"encoding/json"
+	"testing"
+	"testing/fstest"
+)
+
+// TestHealthProbeMarshalsToJSON. yaml.v3 decodes a nested mapping with an unquoted
+// numeric key into map[any]any, which encoding/json refuses; the service list then
+// cannot reach the UI and the app shows nothing.
+func TestHealthProbeMarshalsToJSON(t *testing.T) {
+	fsys := fstest.MapFS{"services/x/a.yml": {Data: []byte(`
+name: A
+slug: a
+docker:
+  image: a:1
+  health_probe:
+    command: [myst, status]
+    checks:
+      - expect:
+          200: ok
+          state: {1: up}
+`)}}
+	cat, err := LoadEmbedded(fsys)
+	if err != nil {
+		t.Fatal(err)
+	}
+	svc := mustGet(t, cat, "a")
+	out, err := json.Marshal(svc)
+	if err != nil {
+		t.Fatalf("service with a numeric-keyed health_probe must marshal to JSON: %v", err)
+	}
+	var back struct {
+		Docker struct {
+			HealthProbe map[string]any `json:"healthProbe"`
+		} `json:"docker"`
+	}
+	if err := json.Unmarshal(out, &back); err != nil {
+		t.Fatal(err)
+	}
+	expect := back.Docker.HealthProbe["checks"].([]any)[0].(map[string]any)["expect"].(map[string]any)
+	if expect["200"] != "ok" || expect["state"].(map[string]any)["1"] != "up" {
+		t.Errorf("probe keys lost on the way through: %v", expect)
+	}
+}
+
+// TestHealthProbeNonFiniteFloatMarshals. YAML .nan, .inf and -.inf decode to
+// float64 NaN and Inf, which encoding/json refuses just like map[any]any.
+func TestHealthProbeNonFiniteFloatMarshals(t *testing.T) {
+	fsys := fstest.MapFS{"services/x/a.yml": {Data: []byte(`
+name: A
+slug: a
+docker:
+  image: a:1
+  health_probe:
+    threshold: .nan
+    checks:
+      - {max: .inf, min: -.inf, ok: 1.5}
+`)}}
+	cat, err := LoadEmbedded(fsys)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := json.Marshal(cat.ListVisible()); err != nil {
+		t.Fatalf("service list with a non-finite health_probe float must marshal to JSON: %v", err)
+	}
+	p := mustGet(t, cat, "a").Docker.HealthProbe
+	c := p["checks"].([]any)[0].(map[string]any)
+	if p["threshold"] != "NaN" || c["max"] != "+Inf" || c["min"] != "-Inf" || c["ok"] != 1.5 {
+		t.Errorf("probe floats not normalised as expected: %v", p)
+	}
+}