refactor(persistence)!: run the web database on WebAssembly

.gitignore

@@ -140,8 +140,8 @@ gradle-wrapper.jar
 
 # Exceptions to the above rules
 !/pubspec.lock
-!**/example/web/sql-wasm.js
-!**/example/web/sql-wasm.wasm
-!/sample_app/web/sql-wasm.js
-!/sample_app/web/sql-wasm.wasm
+!**/example/web/drift_worker.js
+!**/example/web/sqlite3.wasm
+!/sample_app/web/drift_worker.js
+!/sample_app/web/sqlite3.wasm
 !/sample_app/android/app/google-services.json

analysis_options.yaml

@@ -17,6 +17,7 @@ linter:
     - avoid_relative_lib_imports
     - avoid_slow_async_io
     - avoid_types_as_parameter_names
+    - avoid_web_libraries_in_flutter
     - cancel_subscriptions
     - close_sinks
     - control_flow_in_finally

melos.yaml

@@ -43,7 +43,7 @@ command:
       device_preview: ^1.2.0
       diacritic: ^0.1.6
       dio: ^5.11.0
-      drift: ^2.33.0
+      drift: ^2.34.4
       equatable: ^2.0.8
       ezanimation: ^0.6.0
       firebase_core: ^4.0.0
@@ -121,6 +121,7 @@ command:
       url_launcher: ^6.3.2
       uuid: ^4.5.3
       video_player: ^2.11.1
+      web: ^1.1.1
       web_socket_channel: ^3.0.3
 
     # List of all the dev_dependencies used in the project.
@@ -130,7 +131,7 @@ command:
       emojis: ^0.9.9
       substring_highlight: ^1.0.33
       connectivity_plus_platform_interface: ^2.1.0
-      drift_dev: ^2.33.0
+      drift_dev: ^2.34.4
       fake_async: ^1.3.3
       faker_dart: ^0.2.3
       flutter_launcher_icons: ^0.14.4
@@ -203,6 +204,13 @@ scripts:
     run: $MELOS_ROOT_PATH/scripts/generate.sh
     description: Generate the Chat Dart client from the Chat OpenAPI spec.
 
+  web:assets:
+    run: $MELOS_ROOT_PATH/scripts/fetch_web_assets.sh
+    description: >
+      Download the sqlite3.wasm and drift_worker.js files that
+      stream_chat_persistence needs on the web into every web app in this repo.
+      Re-run after bumping `drift` in melos.yaml.
+
   version:update:
     run: dart tools/generate_version.dart
     description: Updates the version.dart file in stream_chat package based on pubspec.yaml version.

migrations/v11-migration.md

@@ -19,6 +19,7 @@ onto Stream's OpenAPI-generated API client.
 - [Error Handling](#error-handling)
     - [The error type changed too](#the-error-type-changed-too)
 - [Feature Areas](#feature-areas)
+    - [Web Persistence](#web-persistence)
 - [Migration Checklist](#migration-checklist)
 - [For AI Agents](#for-ai-agents)
 - [Contributing to this guide](#contributing-to-this-guide)
@@ -58,6 +59,7 @@ from the spec, so don't subclass them or depend on their private constructors.
 | Feature Area | Key Changes |
 | --- | --- |
 | [**Error Handling**](#error-handling) | API calls return `Result<T>` instead of throwing; failures carry `stream_core`'s sealed `StreamException` family instead of `StreamChatNetworkError`; `ChatErrorCode` → `StreamErrorCode` |
+| [**Web Persistence**](#web-persistence) | drift's deprecated sql.js backend replaced by WebAssembly, so `dart2wasm` builds are supported; `sql-wasm.js`/`sql-wasm.wasm` replaced by `sqlite3.wasm`/`drift_worker.js`; `webUseExperimentalIndexedDb` removed in favour of `webOptions`; web caches are refilled once |
 | _(filled in per feature as PRs land)_ | |
 
 ---
@@ -73,6 +75,8 @@ search-and-replace you can apply directly. `Kind` is one of `renamed`, `removed`
 | `StreamChatNetworkError.code` / `.message` / `.statusCode` | `StreamApiException.code` / `.message` / `.statusCode` | `moved` | `code` is now a `StreamErrorCode` |
 | `StreamChatNetworkError.isRequestCancelledError` | `StreamNetworkException.isCancelled` | `moved` | |
 | `ChatErrorCode` | `StreamErrorCode` (`stream_core`) | `removed` | Extension type over `int` with named constants |
+| `StreamChatPersistenceClient(webUseExperimentalIndexedDb:)` | `StreamChatPersistenceClient(webOptions:)` | `removed` | Storage selection is automatic now, so there is no flag to forward |
+| — | `StreamChatPersistenceWebOptions` | `renamed` | New type, exported from `package:stream_chat_persistence/stream_chat_persistence.dart` |
 | _(more added per feature as PRs land)_ | | | |
 
 ---
@@ -157,6 +161,84 @@ counterpart: `code` is now a `StreamErrorCode` (an extension type over `int`, wi
 _Each migrated feature gets a section here. Sections are added by the PR that migrates the feature, using the
 template in [Contributing to this guide](#contributing-to-this-guide)._
 
+### Web Persistence
+
+#### Key Changes:
+
+- `stream_chat_persistence` now runs sqlite3 as WebAssembly instead of through drift's deprecated sql.js
+  backend. Persistence works in apps compiled with `dart2wasm` for the first time; before, those builds fell
+  through to an implementation that threw `UnsupportedError`.
+- The files you copy into `web/` changed: **remove** `sql-wasm.js` and `sql-wasm.wasm`, **add** `sqlite3.wasm`
+  and `drift_worker.js`. Take both from the same [drift release][drift-releases] — that is the only
+  combination guaranteed to be compatible.
+- **Remove the `<script defer src="sql-wasm.js">` tag from `web/index.html`.** Nothing replaces it:
+  `drift_worker.js` is started by drift as a worker at runtime and must not be loaded into the page.
+- `webUseExperimentalIndexedDb` is removed. drift now probes the browser and picks the most reliable storage it
+  supports on its own, which is what the flag was approximating.
+- New `webOptions` parameter, taking a `StreamChatPersistenceWebOptions`, for pointing at the two files when they
+  are not served next to `index.html`.
+- **Existing web caches are not migrated.** The first launch after upgrading starts from an empty offline cache
+  and refills it from the API. Nothing is lost that is not on the server — the local database is a cache — but the
+  first load on web hits the network.
+- The storage drift chose is reported through the client's logger at `Level.INFO`, with a `WARNING` when the
+  browser can only offer storage that two open tabs could corrupt, and a `SEVERE` when it cannot persist at all.
+- A cached database that cannot be opened is discarded and rebuilt from an empty one rather than failing
+  `connect`, so a cache damaged by a killed tab costs one extra sync instead of blocking sign-in.
+
+#### Migration Steps:
+
+**Before:**
+```dart
+final chatPersistentClient = StreamChatPersistenceClient(
+  logLevel: Level.INFO,
+  connectionMode: ConnectionMode.regular,
+  webUseExperimentalIndexedDb: true,
+);
+```
+```html
+<!-- web/index.html -->
+<script defer src="sql-wasm.js"></script>
+```
+
+**After:**
+```dart
+final chatPersistentClient = StreamChatPersistenceClient(
+  logLevel: Level.INFO,
+  connectionMode: ConnectionMode.regular,
+);
+```
+```html
+<!-- web/index.html — no script tag needed -->
+```
+
+Copy `sqlite3.wasm` and `drift_worker.js` into `web/`, and serve your app with
+`Cross-Origin-Opener-Policy: same-origin` and `Cross-Origin-Embedder-Policy: require-corp` so Chrome and Safari
+can use the origin private file system instead of IndexedDB. The
+[package README](https://pub.dev/packages/stream_chat_persistence#flutter-web) has the per-browser table.
+
+If the two files are hosted somewhere other than next to `index.html`:
+
+```dart
+final chatPersistentClient = StreamChatPersistenceClient(
+  webOptions: StreamChatPersistenceWebOptions(
+    sqlite3Uri: Uri.parse('/assets/sqlite3.wasm'),
+    driftWorkerUri: Uri.parse('/assets/drift_worker.js'),
+  ),
+);
+```
+
+The upgrade removes the two `localStorage` keys the old backend wrote (`moor_db_str_db_<userId>` and
+`moor_db_version_db_<userId>`) on the first connect. If you opted into `webUseExperimentalIndexedDb`, its data
+lives in an IndexedDB database named `moor_databases`, which is **not** removed automatically — that name is
+shared with any other database your app opened through drift's legacy web backend, so deleting it is your call.
+
+> **Why:** `package:drift/web.dart` is deprecated upstream and is built on `dart:html`, which does not exist
+> under `dart2wasm` — so the old backend both blocked WebAssembly builds of consumer apps and was on a path to
+> removal. The WebAssembly backend also stores data in the origin private file system or IndexedDB rather than a
+> `localStorage` string, which removes the ~5 MB storage ceiling that came with the sql.js approach.
+
+[drift-releases]: https://github.com/simolus3/drift/releases
+
 ---
 
 ## Migration Checklist

packages/stream_chat/CHANGELOG.md

@@ -13,6 +13,7 @@
 
 - Fixed reconnect state recovery surfacing an uncatchable error when the connection dropped again mid-recovery; it is now logged, and `connection.recovered` still fires. [#2910](https://github.com/GetStream/stream-chat-flutter/issues/2910)
 - Fixed every failed websocket connect leaving an unhandled error in the root zone, which crash reporters listening on `PlatformDispatcher.onError` report as a fatal crash. [#2921](https://github.com/GetStream/stream-chat-flutter/issues/2921)
+- Fixed `CurrentPlatform` throwing `UnimplementedError` on WebAssembly builds.
 
 ⚠️ Deprecated
 

packages/stream_chat/lib/src/core/platform_detector/platform_detector.dart

@@ -1,6 +1,6 @@
 import 'package:meta/meta.dart' show visibleForTesting;
 import 'platform_detector_stub.dart'
-    if (dart.library.html) 'platform_detector_web.dart'
+    if (dart.library.js_interop) 'platform_detector_web.dart'
     if (dart.library.io) 'platform_detector_io.dart';
 
 /// Possible platforms

packages/stream_chat_flutter/CHANGELOG.md

@@ -18,6 +18,7 @@
 - Fixed a crash on web when the message list rebuilt while messages were selectable, for example after opening the attachment picker.
 - Fixed the browser's native context menu reappearing over the message context menu on web after scrolling messages out of view or deleting one.
 - Fixed the SDK re-enabling the browser's native context menu on web in apps that had disabled it themselves.
+- Fixed `StreamAttachmentHandler` throwing `UnimplementedError` on WebAssembly builds.
 
 ## 10.3.0