diff --git a/platform/api/resource_handlers.go b/platform/api/resource_handlers.go
index d068381..451d87d 100644
--- a/platform/api/resource_handlers.go
+++ b/platform/api/resource_handlers.go
@@ -1123,14 +1123,13 @@ func (h *coreHandlers) gamePlugins(w http.ResponseWriter, r *http.Request) {
 
 // gamePluginManifestRegistration godoc
 // @Summary Register game management plugin manifest
-// @Description Validates and registers one game management plugin manifest as installed registry metadata.
+// @Description Validates and registers one game management plugin manifest as installed registry metadata, refreshing an existing manifest with the same ID in place.
 // @Tags game-plugins
 // @Accept json
 // @Produce json
 // @Param body body dto.GamePluginManifestRegistrationRequest true "Game plugin manifest registration request"
 // @Success 201 {object} dto.GamePluginResponse
 // @Failure 400 {object} dto.ErrorResponse
-// @Failure 409 {object} dto.ErrorResponse
 // @Failure 405 {object} dto.ErrorResponse
 // @Router /api/v1/game-plugins/register-manifest [post]
 func (h *coreHandlers) gamePluginManifestRegistration(w http.ResponseWriter, r *http.Request) {
diff --git a/platform/api/resource_handlers_test.go b/platform/api/resource_handlers_test.go
index 954fd40..2bb240a 100644
--- a/platform/api/resource_handlers_test.go
+++ b/platform/api/resource_handlers_test.go
@@ -1292,8 +1292,15 @@ func TestGamePluginManifestRegistryAPI(t *testing.T) {
 		t.Fatalf("unexpected plugin detail: %+v", detail)
 	}
 
-	duplicate := performJSON(t, router, http.MethodPost, "/api/v1/game-plugins/register-manifest", registration)
-	assertErrorResponse(t, duplicate, http.StatusConflict, errorCodeDuplicate)
+	registration.Manifest.Version = "0.1.1"
+	registration.Manifest.Description = "Development plugin refreshed"
+	registration.ManifestRef = "artifact://manifests/game.example/0.1.1"
+	refreshed := postJSON[dto.GamePluginResponse](t, router, "/api/v1/game-plugins/register-manifest", registration)
+	if refreshed.ID != created.ID || refreshed.Version != "0.1.1" || refreshed.ManifestRef != "artifact://manifests/game.example/0.1.1" {
+		t.Fatalf("expected manifest registration to refresh existing plugin, got %+v", refreshed)
+	}
+	listed = getJSON[dto.GamePluginListResponse](t, router, "/api/v1/game-plugins?serverType=example&status=installed")
+	assertListCount(t, listed.Count, 1)
 }
 
 func TestPluginMarketplaceAPIListsDetailsAndChangesStateSafely(t *testing.T) {
diff --git a/platform/service/resources.go b/platform/service/resources.go
index fba0d40..9483734 100644
--- a/platform/service/resources.go
+++ b/platform/service/resources.go
@@ -766,7 +766,20 @@ func (svc *CoreService) RegisterGamePluginManifest(registration domain.GamePlugi
 	if err := validator.ValidateGamePluginManifestRegistration(registration); err != nil {
 		return domain.GamePlugin{}, err
 	}
-	return svc.CreateGamePlugin(gamePluginFromManifestRegistration(registration))
+	plugin := gamePluginFromManifestRegistration(registration)
+	plugin.ProductionLifecycle = normalizedProductionLifecycle(plugin.ProductionLifecycle)
+	if err := validator.ValidateGamePlugin(plugin); err != nil {
+		return domain.GamePlugin{}, err
+	}
+	if err := svc.store.GamePlugins().Create(plugin); err != nil {
+		if !errors.Is(err, repo.ErrDuplicate) {
+			return domain.GamePlugin{}, err
+		}
+		if err := svc.store.GamePlugins().Update(plugin); err != nil {
+			return domain.GamePlugin{}, err
+		}
+	}
+	return domain.CopyGamePlugin(plugin), nil
 }
 
 func gamePluginFromManifestRegistration(registration domain.GamePluginManifestRegistration) domain.GamePlugin {
diff --git a/platform/service/resources_test.go b/platform/service/resources_test.go
index 4cfb142..5603fd1 100644
--- a/platform/service/resources_test.go
+++ b/platform/service/resources_test.go
@@ -1605,16 +1605,26 @@ func TestCoreServiceRejectsArbitrarySQLBridgeInputBeforeJob(t *testing.T) {
 	}
 }
 
-func TestCoreServiceRejectsDuplicateGamePluginManifest(t *testing.T) {
+func TestCoreServiceUpsertsDuplicateGamePluginManifest(t *testing.T) {
 	svc := newTestCoreService()
 	registration := validPluginManifestRegistration()
 	if _, err := svc.RegisterGamePluginManifest(registration); err != nil {
 		t.Fatalf("register first manifest: %v", err)
 	}
 
-	_, err := svc.RegisterGamePluginManifest(registration)
-	if !errors.Is(err, repo.ErrDuplicate) {
-		t.Fatalf("expected duplicate plugin registration, got %v", err)
+	registration.Manifest.Version = "0.1.1"
+	registration.Manifest.Description = "Development plugin refreshed"
+	registration.ManifestRef = "artifact://manifests/game.example/0.1.1"
+	updated, err := svc.RegisterGamePluginManifest(registration)
+	if err != nil {
+		t.Fatalf("upsert manifest: %v", err)
+	}
+	if updated.ID != "game.example" || updated.Version != "0.1.1" || updated.ManifestRef != "artifact://manifests/game.example/0.1.1" {
+		t.Fatalf("expected existing plugin to update in place, got %+v", updated)
+	}
+	listed, err := svc.ListGamePlugins(domain.GamePluginFilter{ServerType: "example", Status: domain.GamePluginStatusInstalled})
+	if err != nil || len(listed) != 1 || listed[0].ID != "game.example" || listed[0].Version != "0.1.1" {
+		t.Fatalf("expected one refreshed plugin after upsert, listed=%+v err=%v", listed, err)
 	}
 }