fix: the app head is the tail of app.versions, not the newest timestamp

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

backend/.sqlx/query-1461a023390f674b0d2e286b506c0838c7cad23619984f44fb4c88d377acffc7.json

@@ -0,0 +1,47 @@
+{
+  "db_name": "PostgreSQL",
+  "query": "SELECT a.id as app_id, av.id as version_id, dm.deployment_msg as deployment_msg,\n                av.created_by as created_by, av.created_at as created_at\n        FROM app a JOIN app_version av ON av.id = a.versions[array_upper(a.versions, 1)]\n        LEFT JOIN deployment_metadata dm ON av.id = dm.app_version\n        WHERE a.workspace_id = $1 AND a.path = $2",
+  "describe": {
+    "columns": [
+      {
+        "ordinal": 0,
+        "name": "app_id",
+        "type_info": "Int8"
+      },
+      {
+        "ordinal": 1,
+        "name": "version_id",
+        "type_info": "Int8"
+      },
+      {
+        "ordinal": 2,
+        "name": "deployment_msg",
+        "type_info": "Text"
+      },
+      {
+        "ordinal": 3,
+        "name": "created_by",
+        "type_info": "Varchar"
+      },
+      {
+        "ordinal": 4,
+        "name": "created_at",
+        "type_info": "Timestamptz"
+      }
+    ],
+    "parameters": {
+      "Left": [
+        "Text",
+        "Text"
+      ]
+    },
+    "nullable": [
+      false,
+      false,
+      true,
+      false,
+      false
+    ]
+  },
+  "hash": "1461a023390f674b0d2e286b506c0838c7cad23619984f44fb4c88d377acffc7"
+}

backend/windmill-api/src/apps.rs

@@ -1273,15 +1273,21 @@ async fn get_latest_version(
     let path = path.to_path();
     check_scopes(&authed, || format!("apps:read:{}", path))?;
     let mut tx = user_db.begin(&authed).await?;
+    // The head is the tail of `app.versions` — the version the runtime serves. Deploys
+    // append to it under the app row's lock, whereas `app_version.created_at` is the
+    // deploying transaction's start time, so two that overlap can carry it in either
+    // order and the newest timestamp is then not the one that landed last.
     let row = sqlx::query!(
         "SELECT a.id as app_id, av.id as version_id, dm.deployment_msg as deployment_msg,
                 av.created_by as created_by, av.created_at as created_at
-        FROM app a LEFT JOIN app_version av ON a.id = av.app_id LEFT JOIN deployment_metadata dm ON av.id = dm.app_version
-        WHERE a.workspace_id = $1 AND a.path = $2
-        ORDER BY av.created_at DESC",
+        FROM app a JOIN app_version av ON av.id = a.versions[array_upper(a.versions, 1)]
+        LEFT JOIN deployment_metadata dm ON av.id = dm.app_version
+        WHERE a.workspace_id = $1 AND a.path = $2",
         w_id,
         path,
-    ).fetch_optional(&mut *tx).await?;
+    )
+    .fetch_optional(&mut *tx)
+    .await?;
     tx.commit().await?;
 
     if let Some(row) = row {

frontend/src/lib/components/apps/editor/AppEditorHeader.svelte

@@ -393,13 +393,13 @@
 			custom_path: customPath,
 			labels: $state.snapshot(labels)
 		}
-		const appHistory = await AppService.getAppHistoryByPath({
+		const head = await AppService.getAppLatestVersion({
 			workspace: $workspaceStore!,
 			path: npath
 		})
 		// `version` is what is deployed now, which is the deploy guard's fallback head; the
 		// deploy's own answer is the base, and the two differ when another landed beside it.
-		version = appHistory[0]?.version
+		version = head?.version
 		// Re-pin the fork base to the version just written: the editor stays open, so a
 		// follow-up deploy (or a new edit) would otherwise compare against the now-
 		// superseded base and falsely warn. parent_version is in
@@ -410,8 +410,8 @@
 		onDeploy?.({
 			version: deployed.version,
 			head: version,
-			headBy: appHistory[0]?.created_by,
-			headAt: appHistory[0]?.created_at
+			headBy: head?.created_by,
+			headAt: head?.created_at
 		})
 
 		closeSaveDrawer()

frontend/src/lib/components/raw_apps/RawAppEditorHeader.svelte

@@ -548,14 +548,14 @@
 			custom_path: customPath,
 			labels: $state.snapshot(labels)
 		}
-		const appHistory = await AppService.getAppHistoryByPath({
+		const head = await AppService.getAppLatestVersion({
 			workspace: opWorkspace!,
 			path: npath
 		})
 		// The deploy's own answer is the next draft's base; `version` is what is deployed
 		// now, and the two differ when another deploy landed beside this one. The route
 		// owns this prop and re-pushes `parentVersion ?? head` as soon as `onDeploy` returns.
-		version = appHistory[0]?.version
+		version = head?.version
 
 		closeSaveDrawer()
 		sendUserToast('App deployed successfully')
@@ -574,8 +574,8 @@
 			path: npath,
 			version: deployed.version,
 			head: version,
-			headBy: appHistory[0]?.created_by,
-			headAt: appHistory[0]?.created_at
+			headBy: head?.created_by,
+			headAt: head?.created_at
 		})
 	}