diff --git a/src/pyodide/internal/metadata.ts b/src/pyodide/internal/metadata.ts
index 256b2544757..aabdc6356ea 100644
--- a/src/pyodide/internal/metadata.ts
+++ b/src/pyodide/internal/metadata.ts
@@ -65,11 +65,10 @@ const FORCE_NEW_VENDOR_PATH: boolean =
   !!COMPATIBILITY_FLAGS.python_workers_force_new_vendor_path;
 export const IS_DEDICATED_SNAPSHOT_ENABLED: boolean =
   !!COMPATIBILITY_FLAGS.python_dedicated_snapshot;
-const EXTERNAL_SDK = !!COMPATIBILITY_FLAGS.enable_python_external_sdk;
+export const EXTERNAL_SDK = !!COMPATIBILITY_FLAGS.enable_python_external_sdk;
 
 export const LEGACY_GLOBAL_HANDLERS = !NO_GLOBAL_HANDLERS;
 export const LEGACY_VENDOR_PATH = !FORCE_NEW_VENDOR_PATH;
-export const LEGACY_INCLUDE_SDK = !EXTERNAL_SDK;
 export const CHECK_RNG_STATE = !!COMPATIBILITY_FLAGS.python_check_rng_state;
 
 export const setCpuLimitNearlyExceededCallback =
diff --git a/src/pyodide/python-entrypoint-helper.ts b/src/pyodide/python-entrypoint-helper.ts
index 60b29ba6f61..7ade0357359 100644
--- a/src/pyodide/python-entrypoint-helper.ts
+++ b/src/pyodide/python-entrypoint-helper.ts
@@ -13,7 +13,7 @@ import {
   COMPATIBILITY_FLAGS,
   IS_WORKERD,
   LEGACY_GLOBAL_HANDLERS,
-  LEGACY_INCLUDE_SDK,
+  EXTERNAL_SDK,
   LOCKFILE,
   MAIN_MODULE_NAME,
   SHOULD_SNAPSHOT_TO_DISK,
@@ -200,6 +200,24 @@ async function applyPatch(pyodide: Pyodide, patchName: string): Promise<void> {
 }
 
 async function injectWorkersApi(pyodide: Pyodide): Promise<void> {
+  if (EXTERNAL_SDK) {
+    pyodide.FS.mkdir(`${pyodide.FS.sitePackages}/workers`);
+    const template = [
+      `err = ModuleNotFoundError("No module named '$MODNAME'", name="$MODNAME")`,
+      `err.add_note("You need to update to workers-py >= 1.90 or to pass disable_python_external_sdk")`,
+      `raise err`,
+    ].join('\n');
+    pyodide.FS.writeFile(
+      `${pyodide.FS.sitePackages}/workers/__init__.py`,
+      template.replaceAll('$MODNAME', 'workers')
+    );
+    pyodide.FS.writeFile(
+      `${pyodide.FS.sitePackages}/asgi.py`,
+      template.replaceAll('$MODNAME', 'asgi')
+    );
+    return;
+  }
+
   const sitePackages = pyodide.FS.sitePackages;
   if (pyodide.version === PyodideVersion.V0_26_0a2) {
     // Inject at cloudflare.workers for backwards compatibility
@@ -250,9 +268,7 @@ async function setupPatches(pyodide: Pyodide): Promise<void> {
     pyodide.registerJsModule('_cloudflare_compat_flags', COMPATIBILITY_FLAGS);
 
     // Inject modules that enable JS features to be used idiomatically from Python.
-    if (LEGACY_INCLUDE_SDK) {
-      await injectWorkersApi(pyodide);
-    }
+    await injectWorkersApi(pyodide);
 
     // Install patches as needed
     if (TRANSITIVE_REQUIREMENTS.has('aiohttp')) {
diff --git a/src/pyodide/types/filesystem.d.ts b/src/pyodide/types/filesystem.d.ts
index 0eeae73b76b..1aac126188f 100644
--- a/src/pyodide/types/filesystem.d.ts
+++ b/src/pyodide/types/filesystem.d.ts
@@ -29,7 +29,11 @@ interface FSLookupResult<Info> {
 interface FS {
   mkdir: (dirname: string) => void;
   mkdirTree: (dirname: string) => void;
-  writeFile: (fname: string, contents: Uint8Array, options: object) => void;
+  writeFile: (
+    fname: string,
+    contents: Uint8Array | string,
+    options?: { canOwn: boolean }
+  ) => void;
   readFile: (fname: string, options?: { encoding?: string }) => Uint8Array;
   mount(fs: object, options: { info?: any }, path: string): void;
   createNode<Info>(
diff --git a/src/workerd/io/compatibility-date.capnp b/src/workerd/io/compatibility-date.capnp
index 98dfaa3901c..5bf8242fb33 100644
--- a/src/workerd/io/compatibility-date.capnp
+++ b/src/workerd/io/compatibility-date.capnp
@@ -1191,7 +1191,7 @@ struct CompatibilityFlags @0x8f8c1b68151b6cef {
   pythonExternalSDK @140 :Bool
     $compatEnableFlag("enable_python_external_sdk")
     $compatDisableFlag("disable_python_external_sdk")
-    $experimental;
+    $compatEnableDate("2026-04-21");
   # Don't include the Python sdk from the runtime, use a vendored copy.
 
   fastJsgStruct @141 :Bool
diff --git a/src/workerd/server/tests/python/vendor_pkg_tests/BUILD b/src/workerd/server/tests/python/vendor_pkg_tests/BUILD
index 7974f0e4536..2a2f82aaa71 100644
--- a/src/workerd/server/tests/python/vendor_pkg_tests/BUILD
+++ b/src/workerd/server/tests/python/vendor_pkg_tests/BUILD
@@ -9,6 +9,15 @@ vendored_py_wd_test("beautifulsoup4")
 
 vendored_py_wd_test(
     "python-workers-runtime-sdk",
+    feature_flags = ["enable_python_external_sdk"],
+)
+
+vendored_py_wd_test(
+    "python-workers-runtime-sdk-override",
+    feature_flags = ["disable_python_external_sdk"],
+    main_py_file = "python-workers-runtime-sdk.py",
+    test_template = "python-workers-runtime-sdk_vendor.wd-test",
+    vendored_package_name = "python-workers-runtime-sdk",
 )
 
 # vendored_py_wd_test("scipy")
diff --git a/src/workerd/server/tests/python/vendor_pkg_tests/python-workers-runtime-sdk_vendor.wd-test b/src/workerd/server/tests/python/vendor_pkg_tests/python-workers-runtime-sdk_vendor.wd-test
index a7fe0aed92b..28ee0ea9c64 100644
--- a/src/workerd/server/tests/python/vendor_pkg_tests/python-workers-runtime-sdk_vendor.wd-test
+++ b/src/workerd/server/tests/python/vendor_pkg_tests/python-workers-runtime-sdk_vendor.wd-test
@@ -8,7 +8,7 @@ const unitTests :Workerd.Config = (
           (name = "main.py", pythonModule = embed "python-workers-runtime-sdk.py"),
           %PYTHON_VENDORED_MODULES%
         ],
-        compatibilityFlags = [%PYTHON_FEATURE_FLAGS, "enable_python_external_sdk", "disable_python_no_global_handlers"],
+        compatibilityFlags = [%PYTHON_FEATURE_FLAGS, "disable_python_no_global_handlers"],
       )
     ),
   ],