diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8c433ad85..d533b593c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,8 @@ Important changes to data models, configuration, and migrations between each
 AppEngine version, listed here to ease deployment and troubleshooting.
 
 ## Next Release (replace with git tag when deployed)
+ * Bump runtimeVersion to `2025.08.12`.
+ * Upgraded stable Dart analysis SDK to `3.9.0`
 
 ## `20250807t091600-all`
  * Bump runtimeVersion to `2025.08.05`.
diff --git a/Dockerfile.worker b/Dockerfile.worker
index c782cb1b2..dd35d1dd6 100644
--- a/Dockerfile.worker
+++ b/Dockerfile.worker
@@ -23,7 +23,7 @@ RUN mkdir -p /home/worker/config/dart-stable
 RUN mkdir -p /home/worker/config/flutter-stable
 
 # Setup Dart SDK into /home/worker/dart/{stable,preview}/
-RUN XDG_CONFIG_HOME=/home/worker/config/dart-stable tool/setup-dart.sh /home/worker/dart/stable 3.8.3
+RUN XDG_CONFIG_HOME=/home/worker/config/dart-stable tool/setup-dart.sh /home/worker/dart/stable stable/raw/hash/54588cb8088890ea08fe1a31b95efe478a4609b5
 
 # Setup Flutter SDK into /home/worker/flutter/{stable,preview}/
 RUN XDG_CONFIG_HOME=/home/worker/config/flutter-stable tool/setup-flutter.sh /home/worker/flutter/stable 3.32.8
diff --git a/app/lib/shared/versions.dart b/app/lib/shared/versions.dart
index ad38a8133..40b651076 100644
--- a/app/lib/shared/versions.dart
+++ b/app/lib/shared/versions.dart
@@ -24,10 +24,10 @@ final RegExp runtimeVersionPattern = RegExp(r'^\d{4}\.\d{2}\.\d{2}$');
 /// when the version switch happens.
 const _acceptedRuntimeVersions = <String>[
   // The current [runtimeVersion].
-  '2025.08.05',
+  '2025.08.12',
   // Fallback runtime versions.
+  '2025.08.05',
   '2025.07.14',
-  '2025.07.04',
 ];
 
 /// Sets the current runtime versions.
@@ -62,7 +62,7 @@ bool shouldGCVersion(String version) =>
 
 // keep in-sync with SDK version in .mono_repo.yml and Dockerfile
 final String runtimeSdkVersion = '3.8.0';
-final String toolStableDartSdkVersion = '3.8.3';
+final String toolStableDartSdkVersion = '3.9.0';
 final String toolStableFlutterSdkVersion = '3.32.8';
 
 final semanticToolStableDartSdkVersion =