diff --git a/admin/app/controllers/system_controller.ts b/admin/app/controllers/system_controller.ts
index dea0cee..54f89ed 100644
--- a/admin/app/controllers/system_controller.ts
+++ b/admin/app/controllers/system_controller.ts
@@ -488,6 +488,7 @@ export default class SystemController {
             installation_status: 'idle',
             is_dependency_service: false,
             is_custom: true,
+            is_existing: true,
             category: payload.category ?? 'custom',
             display_order: publishedHostPort ? CUSTOM_APP_HOME_DISPLAY_ORDER : null,
             depends_on: null,
@@ -498,7 +499,7 @@ export default class SystemController {
         return response.send({ success: true, message: `Existing app ${payload.friendly_name} added.`, service_name: payload.container_name })
     }
 
-    /** Delete a custom app: stop + remove its container, then delete the DB record. */
+    /** Delete a custom app, or unregister an existing app without touching its container. */
     async deleteCustomApp({ request, response }: HttpContext) {
         const payload = await request.validateUsing(deleteCustomAppValidator)
 
@@ -510,10 +511,13 @@ export default class SystemController {
             return response.status(403).send({ error: 'Only custom apps can be deleted.' })
         }
 
-        await this.dockerService.removeCustomAppContainer(payload.service_name, payload.remove_image ?? false)
+        if (!service.is_existing) {
+            await this.dockerService.removeCustomAppContainer(payload.service_name, payload.remove_image ?? false)
+        }
         await service.delete()
 
-        return response.send({ success: true, message: `Custom app ${payload.service_name} deleted` })
+        const action = service.is_existing ? 'removed from Supply Depot' : 'deleted'
+        return response.send({ success: true, message: `Custom app ${payload.service_name} ${action}` })
     }
 
     /** Uninstall a curated catalog app: stop + remove its container (optionally its image) and
@@ -601,6 +605,9 @@ export default class SystemController {
         if (!service.is_custom) {
             return response.status(403).send({ success: false, message: 'Only custom apps can be updated this way.' })
         }
+        if (service.is_existing) {
+            return response.status(403).send({ success: false, message: 'Existing apps are not recreated or updated by NOMAD.' })
+        }
 
         const result = await this.dockerService.recreateCustomAppContainer(payload.service_name, {
             forcePull: true,
@@ -668,6 +675,37 @@ export default class SystemController {
         if (service.is_dependency_service) {
             return response.status(403).send({ success: false, message: 'This service cannot be edited.' })
         }
+        if (service.is_existing) {
+            service.friendly_name = payload.friendly_name
+            service.container_image = payload.image
+            service.category = payload.category ?? service.category ?? 'custom'
+            if (payload.icon) service.icon = payload.icon
+
+            const inspect = await this.dockerService.inspectContainerByName(payload.service_name)
+            const publishedHostPort = inspect ? DockerService.getFirstPublishedHostPort(inspect) : null
+            service.ui_location = publishedHostPort
+            if (
+                (service.ui_location || service.custom_url) &&
+                (service.display_order === null || service.display_order >= 50)
+            ) {
+                service.display_order = CUSTOM_APP_HOME_DISPLAY_ORDER
+            }
+            if (
+                !service.ui_location &&
+                !service.custom_url &&
+                service.display_order === CUSTOM_APP_HOME_DISPLAY_ORDER
+            ) {
+                service.display_order = null
+            }
+            service.is_user_modified = true
+            await service.save()
+
+            return response.send({
+                success: true,
+                message: `Existing app ${payload.service_name} updated.`,
+                service_name: payload.service_name,
+            })
+        }
 
         // Reject duplicate host ports within the request.
         const hostPorts = (payload.ports ?? []).map((p) => p.host)
@@ -868,6 +906,7 @@ export default class SystemController {
         return {
             service_name: service.service_name,
             friendly_name: service.friendly_name,
+            is_existing: service.is_existing,
             image: service.container_image,
             category: service.category ?? 'custom',
             icon: service.icon ?? 'IconBrandDocker',
diff --git a/admin/app/jobs/check_service_updates_job.ts b/admin/app/jobs/check_service_updates_job.ts
index cdbf68e..1da18ba 100644
--- a/admin/app/jobs/check_service_updates_job.ts
+++ b/admin/app/jobs/check_service_updates_job.ts
@@ -26,7 +26,9 @@ export class CheckServiceUpdatesJob {
     // Determine host architecture
     const hostArch = await this.getHostArch(dockerService)
 
-    const installedServices = await Service.query().where('installed', true)
+    const installedServices = await Service.query()
+      .where('installed', true)
+      .where('is_existing', false)
     let updatesFound = 0
 
     for (const service of installedServices) {
diff --git a/admin/app/models/service.ts b/admin/app/models/service.ts
index 8d192ef..a03abb5 100644
--- a/admin/app/models/service.ts
+++ b/admin/app/models/service.ts
@@ -75,6 +75,15 @@ export default class Service extends BaseModel {
   })
   declare is_custom: boolean
 
+  // True for Docker containers the user registered after creating them outside NOMAD. These
+  // records are metadata-only: NOMAD may start/stop them, but must not recreate or delete them.
+  @column({
+    serialize(value) {
+      return Boolean(value)
+    },
+  })
+  declare is_existing: boolean
+
   @column({
     serialize(value) {
       return Boolean(value)
diff --git a/admin/app/services/app_auto_update_service.ts b/admin/app/services/app_auto_update_service.ts
index c6317b6..9e1fa60 100644
--- a/admin/app/services/app_auto_update_service.ts
+++ b/admin/app/services/app_auto_update_service.ts
@@ -179,7 +179,10 @@ export class AppAutoUpdateService {
 
   /** Installed, opted-in apps that are eligible to update right now. */
   async getEligibleApps(config: AppAutoUpdateConfig, now: DateTime): Promise<AppUpdateTarget[]> {
-    const apps = await Service.query().where('installed', true).where('auto_update_enabled', true)
+    const apps = await Service.query()
+      .where('installed', true)
+      .where('auto_update_enabled', true)
+      .where('is_existing', false)
     const targets: AppUpdateTarget[] = []
     for (const service of apps) {
       const verdict = this.appEligibility(service, config.cooloffHours, now)
@@ -340,7 +343,10 @@ export class AppAutoUpdateService {
     const config = await this.getConfig()
     const now = DateTime.now()
 
-    const apps = await Service.query().where('installed', true).where('auto_update_enabled', true)
+    const apps = await Service.query()
+      .where('installed', true)
+      .where('auto_update_enabled', true)
+      .where('is_existing', false)
     const appStatuses: AppAutoUpdateAppStatus[] = apps.map((service) => {
       const verdict = this.appEligibility(service, config.cooloffHours, now)
       return {
diff --git a/admin/app/services/docker_service.ts b/admin/app/services/docker_service.ts
index 7f59f09..a3809e2 100644
--- a/admin/app/services/docker_service.ts
+++ b/admin/app/services/docker_service.ts
@@ -362,6 +362,12 @@ export class DockerService {
           message: `Service ${serviceName} not found`,
         }
       }
+      if (service.is_existing) {
+        return {
+          success: false,
+          message: `Existing app ${serviceName} is registered only and cannot be force reinstalled by NOMAD`,
+        }
+      }
 
       // Check if installation is already in progress
       if (this.activeInstallations.has(serviceName)) {
@@ -1588,6 +1594,12 @@ export class DockerService {
       if (!service.installed) {
         return { success: false, message: `Service ${serviceName} is not installed` }
       }
+      if (service.is_existing) {
+        return {
+          success: false,
+          message: `Existing app ${serviceName} is registered only and cannot be updated by NOMAD`,
+        }
+      }
       if (this.activeInstallations.has(serviceName)) {
         return { success: false, message: `Service ${serviceName} already has an operation in progress` }
       }
diff --git a/admin/app/services/system_service.ts b/admin/app/services/system_service.ts
index 92798e7..d9d3b2c 100644
--- a/admin/app/services/system_service.ts
+++ b/admin/app/services/system_service.ts
@@ -342,6 +342,7 @@ export class SystemService {
         'available_update_version',
         'auto_update_enabled',
         'is_custom',
+        'is_existing',
         'is_user_modified',
         'is_deprecated',
         'category'
@@ -382,6 +383,7 @@ export class SystemService {
         available_update_version: service.available_update_version,
         auto_update_enabled: service.auto_update_enabled,
         is_custom: service.is_custom,
+        is_existing: service.is_existing,
         is_user_modified: service.is_user_modified,
         is_deprecated: service.is_deprecated,
         category: service.category,
diff --git a/admin/database/migrations/1772000000004_add_existing_app_flag_to_services.ts b/admin/database/migrations/1772000000004_add_existing_app_flag_to_services.ts
new file mode 100644
index 0000000..e982bc8
--- /dev/null
+++ b/admin/database/migrations/1772000000004_add_existing_app_flag_to_services.ts
@@ -0,0 +1,27 @@
+import { BaseSchema } from '@adonisjs/lucid/schema'
+
+export default class extends BaseSchema {
+  protected tableName = 'services'
+
+  async up() {
+    this.schema.alterTable(this.tableName, (table) => {
+      table.boolean('is_existing').notNullable().defaultTo(false)
+    })
+
+    this.defer(async (db) => {
+      // Earlier Add Existing App records were saved as custom apps with no generated
+      // container_config. Backfill those so they keep their external-container semantics.
+      await db
+        .from(this.tableName)
+        .where('is_custom', true)
+        .whereNull('container_config')
+        .update({ is_existing: true })
+    })
+  }
+
+  async down() {
+    this.schema.alterTable(this.tableName, (table) => {
+      table.dropColumn('is_existing')
+    })
+  }
+}
diff --git a/admin/database/seeders/service_seeder.ts b/admin/database/seeders/service_seeder.ts
index 77362b1..68586c8 100644
--- a/admin/database/seeders/service_seeder.ts
+++ b/admin/database/seeders/service_seeder.ts
@@ -13,6 +13,7 @@ type ServiceSeedRecord = Omit<
   | 'available_update_version'
   | 'update_checked_at'
   | 'metadata'
+  | 'is_existing'
   | 'is_user_modified'
   | 'is_deprecated'
   | 'custom_url'
diff --git a/admin/inertia/components/CustomAppModal.tsx b/admin/inertia/components/CustomAppModal.tsx
index 77ada8f..4cd5634 100644
--- a/admin/inertia/components/CustomAppModal.tsx
+++ b/admin/inertia/components/CustomAppModal.tsx
@@ -25,6 +25,7 @@ interface EnvVar {
 export interface CustomAppInitial {
   service_name: string
   friendly_name: string | null
+  is_existing?: boolean
   image: string
   category: string
   icon: string
@@ -84,6 +85,7 @@ export default function CustomAppModal({
   initial = null,
 }: CustomAppModalProps) {
   const isEdit = mode === 'edit'
+  const isExisting = isEdit && Boolean(initial?.is_existing)
   const [friendlyName, setFriendlyName] = useState('')
   const [image, setImage] = useState('')
   const [category, setCategory] = useState('custom')
@@ -132,6 +134,13 @@ export default function CustomAppModal({
   // conflicts, resource/guard warnings and hard blocks so the user gets feedback before submitting.
   useEffect(() => {
     if (!open) return
+    if (isExisting) {
+      setPortConflicts([])
+      setResourceWarnings([])
+      setBlocked([])
+      setCheckingPreflight(false)
+      return
+    }
     const validPorts = ports
       .map((p) => parseInt(p.host, 10))
       .filter((p) => !isNaN(p))
@@ -162,7 +171,7 @@ export default function CustomAppModal({
     }, 400)
 
     return () => clearTimeout(handle)
-  }, [open, ports, volumes, image])
+  }, [open, isExisting, ports, volumes, image])
 
   function resetForm() {
     setFriendlyName('')
@@ -226,7 +235,7 @@ export default function CustomAppModal({
       showError('Name and image are required.')
       return
     }
-    if (blocked.length > 0) {
+    if (!isExisting && blocked.length > 0) {
       showError('Resolve the blocked issues before installing.')
       return
     }
@@ -282,17 +291,19 @@ export default function CustomAppModal({
   const hasWarnings = portConflicts.length > 0 || resourceWarnings.length > 0
   const hasBlocks = blocked.length > 0
   const canSubmit =
-    friendlyName.trim() && image.trim() && !hasBlocks && (!hasWarnings || forceInstall)
+    friendlyName.trim() &&
+    image.trim() &&
+    (isExisting || (!hasBlocks && (!hasWarnings || forceInstall)))
 
   return (
     <StyledModal
-      title={isEdit ? 'Edit App' : 'Add Custom App'}
+      title={isExisting ? 'Edit Existing App' : isEdit ? 'Edit App' : 'Add Custom App'}
       open={open}
       onCancel={handleClose}
       cancelText="Cancel"
       onConfirm={handleSubmit}
       confirmVariant='primary'
-      confirmText={isEdit ? 'Save & Recreate' : 'Install'}
+      confirmText={isExisting ? 'Save' : isEdit ? 'Save & Recreate' : 'Install'}
       confirmIcon="IconBrandDocker"
       confirmLoading={submitting}
       confirmDisabled={!canSubmit}
diff --git a/admin/inertia/lib/api.ts b/admin/inertia/lib/api.ts
index c3ed8b0..67f04cd 100644
--- a/admin/inertia/lib/api.ts
+++ b/admin/inertia/lib/api.ts
@@ -1165,14 +1165,26 @@ class API {
     cpus?: number
     force?: boolean
   }) {
-    return catchInternal(async () => {
+    try {
       const response = await this.client.post<{
         success: boolean
         message: string
         service_name: string
       }>('/system/services/custom', payload)
       return response.data
-    })()
+    } catch (error) {
+      if (error instanceof AxiosError && error.response?.data) {
+        return error.response.data as {
+          success: false
+          message: string
+          warnings?: string[]
+          portConflicts?: Array<{ port: number; usedBy: string }>
+          blocked?: string[]
+        }
+      }
+      console.error('Error creating custom app:', error)
+      return undefined
+    }
   }
 
   async createExistingApp(payload: {
@@ -1181,14 +1193,20 @@ class API {
     category?: string
     icon?: string
   }) {
-    return catchInternal(async () => {
+    try {
       const response = await this.client.post<{
         success: boolean
         message: string
         service_name: string
       }>('/system/services/existing', payload)
       return response.data
-    })()
+    } catch (error) {
+      if (error instanceof AxiosError && error.response?.data) {
+        return error.response.data as { success: false; message: string }
+      }
+      console.error('Error adding existing app:', error)
+      return undefined
+    }
   }
 
   async setServiceCustomUrl(service_name: string, custom_url: string | null) {
@@ -1264,6 +1282,7 @@ class API {
         app: {
           service_name: string
           friendly_name: string | null
+          is_existing: boolean
           image: string
           category: string
           icon: string
@@ -1291,14 +1310,26 @@ class API {
     cpus?: number
     force?: boolean
   }) {
-    return catchInternal(async () => {
+    try {
       const response = await this.client.put<{
         success: boolean
         message: string
         service_name: string
       }>('/system/services/custom', payload)
       return response.data
-    })()
+    } catch (error) {
+      if (error instanceof AxiosError && error.response?.data) {
+        return error.response.data as {
+          success: false
+          message: string
+          warnings?: string[]
+          portConflicts?: Array<{ port: number; usedBy: string }>
+          blocked?: string[]
+        }
+      }
+      console.error('Error updating custom app:', error)
+      return undefined
+    }
   }
 }
 
diff --git a/admin/inertia/pages/supply-depot.tsx b/admin/inertia/pages/supply-depot.tsx
index d932448..6c12533 100644
--- a/admin/inertia/pages/supply-depot.tsx
+++ b/admin/inertia/pages/supply-depot.tsx
@@ -703,7 +703,7 @@ export default function SupplyDepotPage(props: { system: { services: ServiceSlim
       {/* Delete custom app modal */}
       {modal?.type === 'delete' && (
         <StyledModal
-          title={`Delete ${modal.service.friendly_name ?? modal.service.service_name}`}
+          title={`${modal.service.is_existing ? 'Remove' : 'Delete'} ${modal.service.friendly_name ?? modal.service.service_name}`}
           open
           onCancel={() => {
             if (loading) return
@@ -711,24 +711,33 @@ export default function SupplyDepotPage(props: { system: { services: ServiceSlim
             setModal(null)
           }}
           onConfirm={() => handleDelete(modal.service)}
-          confirmText="Delete"
+          confirmText={modal.service.is_existing ? 'Remove' : 'Delete'}
           confirmIcon="IconTrash"
           confirmVariant="danger"
           confirmLoading={loading}
           icon={<IconAlertTriangle className="text-desert-red" size={40} />}
         >
           <div className="space-y-3 text-sm text-text-muted">
-            <p className="font-semibold text-desert-red">This will permanently remove this custom app.</p>
-            <p>The container will be stopped and removed. Host volume data will remain on disk.</p>
-            <label className="flex items-center gap-2 cursor-pointer select-none">
-              <input
-                type="checkbox"
-                checked={removeImage}
-                onChange={(e) => setRemoveImage(e.target.checked)}
-                className="accent-desert-red h-4 w-4 rounded"
-              />
-              <span className="text-text-muted text-xs">Also remove the Docker image to reclaim disk space</span>
-            </label>
+            {modal.service.is_existing ? (
+              <>
+                <p className="font-semibold text-desert-red">This will remove this existing app from Supply Depot.</p>
+                <p>The Docker container and image will not be stopped, removed, or changed.</p>
+              </>
+            ) : (
+              <>
+                <p className="font-semibold text-desert-red">This will permanently remove this custom app.</p>
+                <p>The container will be stopped and removed. Host volume data will remain on disk.</p>
+                <label className="flex items-center gap-2 cursor-pointer select-none">
+                  <input
+                    type="checkbox"
+                    checked={removeImage}
+                    onChange={(e) => setRemoveImage(e.target.checked)}
+                    className="accent-desert-red h-4 w-4 rounded"
+                  />
+                  <span className="text-text-muted text-xs">Also remove the Docker image to reclaim disk space</span>
+                </label>
+              </>
+            )}
           </div>
         </StyledModal>
       )}
@@ -898,6 +907,7 @@ function AppCard({
   const isRunning = service.status === 'running'
   const isStopped = service.installed && !isRunning
   const catColor = service.category ? CATEGORY_COLORS[service.category] ?? CATEGORY_COLORS.custom : CATEGORY_COLORS.custom
+  const customKindLabel = service.is_existing ? 'existing' : 'custom'
   const isDropdownOpen = openDropdown === service.service_name
   // Port pill: an ui_location may carry an explicit scheme ("https:8480") — show just the port,
   // with a lock when it's served over HTTPS, rather than the raw "https:8480" string.
@@ -994,7 +1004,7 @@ function AppCard({
         )}
         {service.is_custom ? (
           <span className="text-xs px-2 py-0.5 rounded-full font-medium bg-surface-secondary text-text-muted border border-surface-secondary">
-            custom
+            {customKindLabel}
           </span>
         ) : null}
         {service.is_user_modified && !service.is_custom ? (
@@ -1132,12 +1142,19 @@ function AppCard({
                       onClick={onUpdateVersion}
                     />
                   ) : null}
-                  {service.is_custom ? (
+                  {service.is_custom && !service.is_existing ? (
                     <DropdownItem icon={<IconCloudDownload className="h-4 w-4" />} label="Update (pull latest)" onClick={onUpdate} />
                   ) : null}
-                  <DropdownItem icon={<IconRefresh className="h-4 w-4 text-desert-orange" />} label="Force Reinstall" onClick={onReinstall} danger />
+                  {!service.is_existing ? (
+                    <DropdownItem icon={<IconRefresh className="h-4 w-4 text-desert-orange" />} label="Force Reinstall" onClick={onReinstall} danger />
+                  ) : null}
                   {service.is_custom ? (
-                    <DropdownItem icon={<IconTrash className="h-4 w-4 text-desert-red" />} label="Delete" onClick={onDelete} danger />
+                    <DropdownItem
+                      icon={<IconTrash className="h-4 w-4 text-desert-red" />}
+                      label={service.is_existing ? 'Remove' : 'Delete'}
+                      onClick={onDelete}
+                      danger
+                    />
                   ) : (
                     <DropdownItem icon={<IconTrash className="h-4 w-4 text-desert-red" />} label="Uninstall" onClick={onUninstall} danger />
                   )}
diff --git a/admin/types/services.ts b/admin/types/services.ts
index 0883c90..6c7dc7b 100644
--- a/admin/types/services.ts
+++ b/admin/types/services.ts
@@ -17,6 +17,7 @@ export type ServiceSlim = Pick<
   | 'available_update_version'
   | 'auto_update_enabled'
   | 'is_custom'
+  | 'is_existing'
   | 'is_user_modified'
   | 'is_deprecated'
   | 'category'