From 122d39c4dd1eef86b63fb9a87a3310728a162322 Mon Sep 17 00:00:00 2001
From: Patrik Oldsberg <poldsberg@gmail.com>
Date: Mon, 26 Jan 2026 19:45:51 +0100
Subject: [PATCH] frontend-app-api: remove support for experimental package
 config

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>
---
 .changeset/plenty-dryers-tan.md                          | 7 +++++++
 .../src/modules/build/lib/bundler/packageDetection.ts    | 5 +----
 packages/frontend-app-api/config.d.ts                    | 9 ---------
 packages/frontend-defaults/src/discovery.ts              | 5 +----
 4 files changed, 9 insertions(+), 17 deletions(-)
 create mode 100644 .changeset/plenty-dryers-tan.md

diff --git a/.changeset/plenty-dryers-tan.md b/.changeset/plenty-dryers-tan.md
new file mode 100644
index 0000000000..719e151159
--- /dev/null
+++ b/.changeset/plenty-dryers-tan.md
@@ -0,0 +1,7 @@
+---
+'@backstage/frontend-defaults': patch
+'@backstage/frontend-app-api': patch
+'@backstage/cli': patch
+---
+
+Completely removed support for the deprecated `app.experimental.packages` configuration. Replace existing usage directly with `app.packages`.
diff --git a/packages/cli/src/modules/build/lib/bundler/packageDetection.ts b/packages/cli/src/modules/build/lib/bundler/packageDetection.ts
index 4c283c4a65..8c8a064ab9 100644
--- a/packages/cli/src/modules/build/lib/bundler/packageDetection.ts
+++ b/packages/cli/src/modules/build/lib/bundler/packageDetection.ts
@@ -32,10 +32,7 @@ interface PackageDetectionConfig {
 function readPackageDetectionConfig(
   config: Config,
 ): PackageDetectionConfig | undefined {
-  // The experimental key is deprecated, but supported still for backwards compatibility
-  const packages =
-    config.getOptional('app.packages') ??
-    config.getOptional('app.experimental.packages');
+  const packages = config.getOptional('app.packages');
   if (packages === undefined || packages === null) {
     return undefined;
   }
diff --git a/packages/frontend-app-api/config.d.ts b/packages/frontend-app-api/config.d.ts
index 7032cd378d..2a9197750e 100644
--- a/packages/frontend-app-api/config.d.ts
+++ b/packages/frontend-app-api/config.d.ts
@@ -16,15 +16,6 @@
 
 export interface Config {
   app?: {
-    experimental?: {
-      /**
-       * @visibility frontend
-       * @deepVisibility frontend
-       * @deprecated This is no longer experimental; use `app.packages` instead.
-       */
-      packages?: 'all' | { include?: string[]; exclude?: string[] };
-    };
-
     /**
      * Controls what packages are loaded by the new frontend system.
      *
diff --git a/packages/frontend-defaults/src/discovery.ts b/packages/frontend-defaults/src/discovery.ts
index 71d831b58c..584f202c54 100644
--- a/packages/frontend-defaults/src/discovery.ts
+++ b/packages/frontend-defaults/src/discovery.ts
@@ -26,10 +26,7 @@ interface DiscoveryGlobal {
 }
 
 function readPackageDetectionConfig(config: Config) {
-  // The experimental key is deprecated, but supported still for backwards compatibility
-  const packages =
-    config.getOptional('app.packages') ??
-    config.getOptional('app.experimental.packages');
+  const packages = config.getOptional('app.packages');
   if (packages === undefined || packages === null) {
     return undefined;
   }