diff --git a/internal/api/handlers.go b/internal/api/handlers.go
index cf251a3..e9af556 100644
--- a/internal/api/handlers.go
+++ b/internal/api/handlers.go
@@ -86,6 +86,7 @@ func (h *Handlers) Update(w http.ResponseWriter, r *http.Request) {
 			Project:     res.Job.Project,
 			Service:     res.Job.Service,
 			ComposeFile: composeFile,
+			ServiceID:   res.Job.ServiceID,
 			Status:      string(res.Status),
 			Error:       res.Error,
 			DurationMs:  res.DurationMs,
diff --git a/internal/api/swarm_result_test.go b/internal/api/swarm_result_test.go
new file mode 100644
index 0000000..e6d978b
--- /dev/null
+++ b/internal/api/swarm_result_test.go
@@ -0,0 +1,48 @@
+package api_test
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/docker/docker/api/types"
+	"github.com/shcizo/package-updater/internal/api"
+	"github.com/shcizo/package-updater/internal/discovery"
+	"github.com/shcizo/package-updater/internal/updater"
+	"github.com/stretchr/testify/require"
+)
+
+type swarmResultFinder struct{ jobs []discovery.Job }
+
+func (f *swarmResultFinder) FindJobs(_ context.Context, _ string) ([]discovery.Job, error) {
+	return f.jobs, nil
+}
+
+type swarmResultSubmitter struct{ results []updater.Result }
+
+func (s *swarmResultSubmitter) Submit(_ context.Context, _ []discovery.Job) []updater.Result {
+	return s.results
+}
+
+type swarmResultPinger struct{}
+
+func (swarmResultPinger) Ping(_ context.Context) (types.Ping, error) { return types.Ping{}, nil }
+
+func TestUpdate_SwarmJobPopulatesServiceID(t *testing.T) {
+	job := discovery.Job{Service: "myapp_web", ServiceID: "svc123", Image: "registry.example.com/myapp:v2"}
+	finder := &swarmResultFinder{jobs: []discovery.Job{job}}
+	submitter := &swarmResultSubmitter{results: []updater.Result{
+		{Job: job, Status: updater.StatusUpdated, DurationMs: 42},
+	}}
+	h := api.NewHandlers(finder, submitter, swarmResultPinger{}, "v", "c", "b", nil)
+
+	req := httptest.NewRequest(http.MethodPost, "/update", strings.NewReader(`{"image":"registry.example.com/myapp"}`))
+	rec := httptest.NewRecorder()
+	h.Update(rec, req)
+
+	require.Equal(t, http.StatusOK, rec.Code)
+	require.Contains(t, rec.Body.String(), `"service_id":"svc123"`)
+	require.Contains(t, rec.Body.String(), `"service":"myapp_web"`)
+}
diff --git a/internal/api/types.go b/internal/api/types.go
index fc3cf51..02f1f63 100644
--- a/internal/api/types.go
+++ b/internal/api/types.go
@@ -20,6 +20,7 @@ type ResultDTO struct {
 	Project     string `json:"project"`
 	Service     string `json:"service"`
 	ComposeFile string `json:"compose_file"`
+	ServiceID   string `json:"service_id,omitempty"`
 	Status      string `json:"status"`
 	Error       string `json:"error,omitempty"`
 	DurationMs  int64  `json:"duration_ms"`