chore(main): release 4.20.0 (#319)

🤖 I have created a release *beep* *boop*
---


##
[4.20.0](4.19.0...4.20.0)
(2026-06-29)


### Features

* Add experimental support for data-saving mode (FDv2).
([#314](#314))
([c2f9216](c2f9216))
* Update launchdarkly_common_client to version 1.14.0
([#320](#320))
([2144c78](2144c78))

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Publishes a minor SDK release that documents an experimental FDv2
flag-data path and bumps the shared common client; opt-in only, but
connection-mode behavior affects how flag data is fetched when enabled.
> 
> **Overview**
> Cuts **4.20.0** of `launchdarkly_flutter_client_sdk` via Release
Please: package version, `sdkVersion` in `ld_client.dart`,
`.release-please-manifest.json`, and example app dependencies move from
**4.19.0** to **4.20.0**.
> 
> The new **CHANGELOG** entry for 4.20.0 describes what ships in this
release: **Early Access FDv2** (data-saving mode) by setting
`dataSystem: DataSystemConfig()` on `LDConfig`, with lifecycle-driven
connection behavior and runtime control via `setConnectionMode` /
`initialConnectionMode`, while apps without `dataSystem` stay on FDv1.
It also notes the **`launchdarkly_common_client` 1.14.0** dependency
alignment reflected in `pubspec.yaml`.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
e14d43c. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Ryan Lamb <4955475+kinyoklion@users.noreply.github.com>

Author: LaunchDarklyReleaseBot

.release-please-manifest.json

@@ -1 +1 @@
-{"packages/common":"1.8.1","packages/common_client":"1.14.0","packages/event_source_client":"3.0.0","packages/flutter_client_sdk":"4.19.0"}
+{"packages/common":"1.8.1","packages/common_client":"1.14.0","packages/event_source_client":"3.0.0","packages/flutter_client_sdk":"4.20.0"}

packages/flutter_client_sdk/CHANGELOG.md

@@ -2,6 +2,55 @@
 
 All notable changes to the LaunchDarkly Flutter client-side SDK will be documented in this file. This project adheres to [Semantic Versioning](https://semver.org).
 
+## [4.20.0](https://github.com/launchdarkly/flutter-client-sdk/compare/4.19.0...4.20.0) (2026-06-29)
+
+
+### Features
+
+* Add experimental support for data-saving mode (FDv2). ([#314](https://github.com/launchdarkly/flutter-client-sdk/issues/314)) ([c2f9216](https://github.com/launchdarkly/flutter-client-sdk/commit/c2f9216b3e7dc30f1b0f00c18b680aa32d41a91d))
+* Update launchdarkly_common_client to version 1.14.0 ([#320](https://github.com/launchdarkly/flutter-client-sdk/issues/320)) ([2144c78](https://github.com/launchdarkly/flutter-client-sdk/commit/2144c785f5050cbabd421478219f4b5cd7a935a1))
+* Add Early Access support for the FDv2 data system (data saving mode).
+
+The Flutter SDK now supports the **FDv2 data system** in Early Access. Opt in by providing a `DataSystemConfig` when you build your `LDConfig`:
+
+```dart
+final config = LDConfig(
+  '<your-mobile-key>',
+  AutoEnvAttributes.enabled,
+  // Providing a data system configuration (even an empty one) opts the
+  // SDK into the FDv2 data acquisition protocol.
+  dataSystem: const DataSystemConfig(),
+);
+```
+
+Applications that do not provide a `dataSystem` continue to use the existing (FDv1) data sources, so default behavior is unchanged.
+
+By default the SDK streams in the foreground (with polling fallback) and switches to a reduced-rate background mode when the app is backgrounded, following the application lifecycle and network availability automatically. You can turn that automatic switching off through `ApplicationEvents`.
+
+Control the connection mode at runtime with `setConnectionMode`, which takes a `ConnectionModeId` (`streaming`, `polling`, `background`, or `offline`). Setting a mode is a sticky override that suppresses automatic switching; pass no argument to clear it and resume automatic resolution:
+
+```dart
+// Force a specific mode (sticky; suppresses automatic switching).
+client.setConnectionMode(ConnectionModeId.polling);
+
+// Clear the override and resume automatic mode resolution.
+client.setConnectionMode();
+```
+
+To start in a specific mode, set `DataSystemConfig.initialConnectionMode` — equivalent to calling `setConnectionMode` with that mode immediately after the client is created:
+
+```dart
+final config = LDConfig(
+  '<your-mobile-key>',
+  AutoEnvAttributes.enabled,
+  dataSystem: const DataSystemConfig(
+    initialConnectionMode: ConnectionModeId.polling,
+  ),
+);
+```
+
+> This feature is not stable, and not subject to any backwards compatibility guarantees or semantic versioning. It is in early access. If you want access to this feature, please join the EAP. See https://launchdarkly.com/docs/sdk/features/data-saving-mode.
+
 ## [4.19.0](https://github.com/launchdarkly/flutter-client-sdk/compare/4.18.1...4.19.0) (2026-06-10)
 
 

packages/flutter_client_sdk/example/pubspec.yaml

@@ -33,7 +33,7 @@ dependencies:
   # This defaults to a published package. Using `flutter pub get` will get the package from pub.dev
   # If you run `melos bs` in the root of the repository, then it will be linked to the local version
   # instead.
-  launchdarkly_flutter_client_sdk: 4.19.0 # x-release-please-version
+  launchdarkly_flutter_client_sdk: 4.20.0 # x-release-please-version
 
   # The following adds the Cupertino Icons font to your application.
   # Use with the CupertinoIcons class for iOS style icons.

packages/flutter_client_sdk/example_fdv2/pubspec.yaml

@@ -13,7 +13,7 @@ dependencies:
   # This defaults to a published package. Using `flutter pub get` will get the
   # package from pub.dev. If you run `melos bs` in the root of the repository,
   # then it will be linked to the local version instead.
-  launchdarkly_flutter_client_sdk: 4.19.0 # x-release-please-version
+  launchdarkly_flutter_client_sdk: 4.20.0 # x-release-please-version
   cupertino_icons: ^1.0.6
 
 dev_dependencies:

packages/flutter_client_sdk/lib/src/ld_client.dart

@@ -9,7 +9,7 @@ import 'platform_env_reporter.dart';
 import 'plugin.dart';
 
 const sdkName = 'FlutterClientSdk';
-const sdkVersion = '4.19.0'; // x-release-please-version
+const sdkVersion = '4.20.0'; // x-release-please-version
 
 /// The main interface for the LaunchDarkly Flutter SDK.
 ///

packages/flutter_client_sdk/pubspec.yaml

@@ -1,6 +1,6 @@
 name: launchdarkly_flutter_client_sdk
 description: Official Flutter client-side SDK for LaunchDarkly. Get started using LaunchDarkly today!
-version: 4.19.0
+version: 4.20.0
 homepage: https://github.com/launchdarkly/flutter-client-sdk
 repository: https://github.com/launchdarkly/flutter-client-sdk/tree/main/packages/flutter_client_sdk