diff --git a/packages/rfw/CHANGELOG.md b/packages/rfw/CHANGELOG.md
index 65db8bc2c480..412f7505d2d1 100644
--- a/packages/rfw/CHANGELOG.md
+++ b/packages/rfw/CHANGELOG.md
@@ -1,7 +1,11 @@
+## 1.0.21
+
+* Adds support for subscribing to the root of a `DynamicContent` object.
+
 ## 1.0.20
 
-* Adds OverflowBox material widget.
-* Updates ButtonBar material widget implementation.
+* Adds `OverflowBox` material widget.
+* Updates `ButtonBar` material widget implementation.
 
 ## 1.0.19
 
diff --git a/packages/rfw/lib/src/flutter/content.dart b/packages/rfw/lib/src/flutter/content.dart
index 84a1eab1ade1..4689eae3fa93 100644
--- a/packages/rfw/lib/src/flutter/content.dart
+++ b/packages/rfw/lib/src/flutter/content.dart
@@ -12,6 +12,9 @@ import 'package:flutter/foundation.dart' show objectRuntimeType;
 import '../dart/model.dart';
 
 /// Signature for the callback passed to [DynamicContent.subscribe].
+///
+/// Do not modify the provided value (e.g. if it is a map or list). Doing so
+/// would leave the [DynamicContent] in an inconsistent state.
 typedef SubscriptionCallback = void Function(Object value);
 
 /// Returns a copy of a data structure if it consists of only [DynamicMap]s,
@@ -116,9 +119,12 @@ Object? deepClone(Object? template) {
 /// [missing] as the new value. It is not an error to subscribe to missing data.
 /// It _is_ an error to add [missing] values to the data model, however.
 ///
+/// To subscribe to the root of the [DynamicContent], use an empty list as the
+/// key when subscribing.
+///
 /// The [LocalWidgetBuilder]s passed to a [LocalWidgetLibrary] use a
 /// [DataSource] as their interface into the [DynamicContent]. To ensure the
-/// integrity of the update mechanism, that interface only allows access to
+/// integrity of the update mechanism, _that_ interface only allows access to
 /// leaves, not intermediate nodes (maps and lists).
 ///
 /// It is an error to subscribe to the same key multiple times with the same
@@ -143,6 +149,13 @@ class DynamicContent {
   /// key.
   ///
   /// Existing keys that are not present in the given map are left unmodified.
+  ///
+  /// If the root node has subscribers (see [subscribe]), they are called once
+  /// per key in `initialData`, not just a single time.
+  ///
+  /// Collections (maps and lists) in `initialData` must not be mutated after
+  /// calling this method; doing so would leave the [DynamicContent] in an
+  /// inconsistent state.
   void updateAll(DynamicMap initialData) {
     for (final String key in initialData.keys) {
       final Object value = initialData[key] ?? missing;
@@ -156,6 +169,10 @@ class DynamicContent {
   ///
   /// The `value` must consist exclusively of [DynamicMap], [DynamicList], [int],
   /// [double], [bool], and [String] objects.
+  ///
+  /// Collections (maps and lists) in `value` must not be mutated after calling
+  /// this method; doing so would leave the [DynamicContent] in an inconsistent
+  /// state.
   void update(String rootKey, Object value) {
     _root.updateKey(rootKey, deepClone(value)!);
     _scheduleCleanup();
@@ -167,7 +184,14 @@ class DynamicContent {
   /// The value is always non-null; if the value is missing, the [missing]
   /// object is used instead.
   ///
+  /// The empty key refers to the root of the [DynamicContent] object (i.e.
+  /// the map manipulated by [updateAll] and [update]).
+  ///
   /// Use [unsubscribe] when the subscription is no longer needed.
+  ///
+  /// Do not modify the value returned by this method or passed to the given
+  /// `callback` (e.g. if it is a map or list). Changes made in this manner will
+  /// leave the [DynamicContent] in an inconsistent state.
   Object subscribe(List<Object> key, SubscriptionCallback callback) {
     return _root.subscribe(key, 0, callback);
   }
@@ -329,12 +353,6 @@ class _DynamicNode {
     _sendUpdates(value);
   }
 
-  void _sendUpdates(Object value) {
-    for (final SubscriptionCallback callback in _callbacks) {
-      callback(value);
-    }
-  }
-
   void updateKey(String rootKey, Object value) {
     assert(_value is DynamicMap);
     assert(_hasValidType(value));
@@ -345,6 +363,13 @@ class _DynamicNode {
     if (_children.containsKey(rootKey)) {
       _children[rootKey]!.update(value);
     }
+    _sendUpdates(_value);
+  }
+
+  void _sendUpdates(Object value) {
+    for (final SubscriptionCallback callback in _callbacks) {
+      callback(value);
+    }
   }
 
   @override
diff --git a/packages/rfw/pubspec.yaml b/packages/rfw/pubspec.yaml
index f2f8c72ab929..af77f3482000 100644
--- a/packages/rfw/pubspec.yaml
+++ b/packages/rfw/pubspec.yaml
@@ -2,7 +2,7 @@ name: rfw
 description: "Remote Flutter widgets: a library for rendering declarative widget description files at runtime."
 repository: https://github.com/flutter/packages/tree/main/packages/rfw
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+rfw%22
-version: 1.0.20
+version: 1.0.21
 
 environment:
   sdk: ">=3.0.0 <4.0.0"
diff --git a/packages/rfw/test/runtime_test.dart b/packages/rfw/test/runtime_test.dart
index 476c472af953..89cb96d62d51 100644
--- a/packages/rfw/test/runtime_test.dart
+++ b/packages/rfw/test/runtime_test.dart
@@ -1074,4 +1074,18 @@ void main() {
     });
     expect(tested, isTrue);
   });
+
+  testWidgets('DynamicContent subscriptions', (WidgetTester tester) async {
+    final List<String> log = <String>[];
+    final DynamicContent data = DynamicContent(<String, Object?>{
+      'a': <Object>[0, 1],
+      'b': <Object>['q', 'r'],
+    });
+    data.subscribe(<Object>[], (Object value) { log.add('root: $value'); });
+    data.subscribe(<Object>['a', 0], (Object value) { log.add('leaf: $value'); });
+    data.update('a', <Object>[2, 3]);
+    expect(log, <String>['leaf: 2', 'root: {a: [2, 3], b: [q, r]}']);
+    data.update('c', 'test');
+    expect(log, <String>['leaf: 2', 'root: {a: [2, 3], b: [q, r]}', 'root: {a: [2, 3], b: [q, r], c: test}']);
+  });
 }
diff --git a/packages/rfw/test_coverage/bin/test_coverage.dart b/packages/rfw/test_coverage/bin/test_coverage.dart
index e925d98cd0e3..f5f0dcdc9cd4 100644
--- a/packages/rfw/test_coverage/bin/test_coverage.dart
+++ b/packages/rfw/test_coverage/bin/test_coverage.dart
@@ -20,9 +20,10 @@ import 'package:meta/meta.dart';
 
 // Please update these targets when you update this package.
 // Please ensure that test coverage continues to be 100%.
-const int targetLines = 3223;
+// Don't forget to update the lastUpdate date too!
+const int targetLines = 3273;
 const String targetPercent = '100';
-const String lastUpdate = '2023-06-29';
+const String lastUpdate = '2024-01-30';
 
 @immutable
 /* final */ class LcovLine {
@@ -196,14 +197,14 @@ Future<void> main(List<String> arguments) async {
       print(
         'Total lines of covered code has increased, and coverage script is now out of date.\n'
         'Coverage is now $coveredPercent%, $coveredLines/$totalLines lines, whereas previously there were only $targetLines lines.\n'
-        'Update the "\$targetLines" constant at the top of rfw/test_coverage/bin/test_coverage.dart (to $coveredLines).',
+        'Update the "targetLines" constant at the top of rfw/test_coverage/bin/test_coverage.dart (to $coveredLines).',
       );
     }
     if (targetLines > totalLines) {
       print(
         'Total lines of code has reduced, and coverage script is now out of date.\n'
         'Coverage is now $coveredPercent%, $coveredLines/$totalLines lines, but previously there were $targetLines lines.\n'
-        'Update the "\$targetLines" constant at the top of rfw/test_coverage/bin/test_coverage.dart (to $totalLines).',
+        'Update the "targetLines" constant at the top of rfw/test_coverage/bin/test_coverage.dart (to $totalLines).',
       );
       exit(1);
     }