leonard_flutter

Host WidgetsBinding for Leonard.

A plain leonard_flutter dependency automatically discovers one Leonard DevTools extension with Conversation and Diagnostics modes. Diagnostics requests a Genesis diagnostics contract 1 projection (ext.leonard.core.get_diagnostics_tree) only while its panel is open; no adopter dependency on leonard_devtools or genesis_foundation is required.

Usage

void main() => LeonardBinding.run(MyApp());

class MyApp implements LeonardApp {
  @override
  LeonardAppConfig build(LeonardAppContext ctx) {
    // Construct Router, ProviderContainer, Dio, etc. *here* — by the
    // time this callback runs, LeonardBinding has already claimed
    // the WidgetsBinding slot, so any WidgetsFlutterBinding.ensureInitialized()
    // call inside (e.g. from go_router 14.x) is an idempotent no-op.
    return LeonardAppConfig(
      extensions: <LeonardExtension>[/* extensions */],
      app: const MaterialApp(home: SizedBox.shrink()),
    );
  }
}

LeonardBinding.run(app) claims the WidgetsBinding slot first, then hands an LeonardAppContext to app.build(ctx) and calls runApp inside the binding's stability zone. Outside debug/profile (kReleaseMode), no binding is installed and no extensions are registered, but app.build and runApp still run.

The lower-level LeonardBinding.ensureInitialized(extensions: [...]) remains for tests, headless agents, and advanced cases that need to own the install ordering themselves. It throws StateError if a foreign WidgetsBinding (e.g. IntegrationTestWidgetsFlutterBinding) is already installed.

Native Android accessibility projection

When the same Flutter app is driven externally through Android's native accessibility channel, Semantics(identifier:) is not a directly tappable accessibility id. See Selecting Flutter widgets through the native channel on Android for the versioned engine fixture, projected tree, and NativeSelector.flutterIdentifier convention.

VM service extension namespace

leonard_flutter reserves ext.leonard.* for all host- and extension-owned VM service extensions. Format:

ext.leonard.<namespace>.<suffix>

• <namespace> is core for host-owned extensions, or an extension's namespace (matching ^[a-z][a-z0-9_]*$).
• <suffix> is the extension's local name.

The host registers ext.leonard.core.handshake from LeonardBinding.ensureInitialized(...). The harness uses it to confirm the binding is live and read protocol/version metadata. Extensions register through ExtensionContext, which auto-prefixes.

DevTools panel

This package ships extension/devtools/config.yaml so any app that transitively depends on leonard_flutter automatically surfaces the Leonard tab in DevTools. The compiled web bundle lives at extension/devtools/build/ and is not committed — rebuild it from the repo root with:

./tool/build_devtools_extension.sh

See packages/leonard_devtools/README.md for the full build workflow.

Libraries

contract

Public surface of the v1 extension contract (PRD §7).

leonard_flutter