diff --git a/.server-changes/background-worker-version-endpoint-tasks.md b/.server-changes/background-worker-version-endpoint-tasks.md
new file mode 100644
index 0000000000..2499bcc3a0
--- /dev/null
+++ b/.server-changes/background-worker-version-endpoint-tasks.md
@@ -0,0 +1,6 @@
+---
+area: webapp
+type: improvement
+---
+
+Speed up retrieving a background worker by version. The endpoint no longer runs a slow lookup that scanned the full task table for large deployments; it now reuses data it already loads, so the response is the same but returns much faster.
diff --git a/apps/webapp/app/routes/api.v1.projects.$projectRef.background-workers.$envSlug.$version.ts b/apps/webapp/app/routes/api.v1.projects.$projectRef.background-workers.$envSlug.$version.ts
index 72c4549279..99e1dcc9ac 100644
--- a/apps/webapp/app/routes/api.v1.projects.$projectRef.background-workers.$envSlug.$version.ts
+++ b/apps/webapp/app/routes/api.v1.projects.$projectRef.background-workers.$envSlug.$version.ts
@@ -45,15 +45,7 @@ export async function loader({ params, request }: LoaderFunctionArgs) {
       },
       include: {
         tasks: true,
-        files: {
-          include: {
-            tasks: {
-              select: {
-                slug: true,
-              },
-            },
-          },
-        },
+        files: true,
       },
     });
 
@@ -61,6 +53,19 @@ export async function loader({ params, request }: LoaderFunctionArgs) {
       return json({ error: "Background worker not found" }, { status: 404 });
     }
 
+    // Group task slugs by fileId from the already-loaded tasks (which are fetched
+    // via the indexed workerId relation) instead of loading files.tasks, which
+    // queries BackgroundWorkerTask by the unindexed fileId column.
+    const taskSlugsByFileId = new Map<string, Set<string>>();
+    for (const task of backgroundWorker.tasks) {
+      if (!task.fileId) {
+        continue;
+      }
+      const slugs = taskSlugsByFileId.get(task.fileId) ?? new Set<string>();
+      slugs.add(task.slug);
+      taskSlugsByFileId.set(task.fileId, slugs);
+    }
+
     return json({
       id: backgroundWorker.friendlyId,
       version: backgroundWorker.version,
@@ -82,7 +87,7 @@ export async function loader({ params, request }: LoaderFunctionArgs) {
         filePath: file.filePath,
         contentHash: file.contentHash,
         contents: decompressContent(file.contents),
-        tasks: Array.from(new Set(file.tasks.map((task) => task.slug))),
+        tasks: Array.from(taskSlugsByFileId.get(file.id) ?? []),
       })),
     });
   } catch (error) {