leonard_devtools 0.1.1

DevTools extension for Leonard.

leonard_devtools

DevTools extension for Leonard. Surfaces three tabs (Prompt, Thinking, Timeline) inside the connected app's DevTools instance and runs the harness in-panel so trajectories persist via the Dart Tooling Daemon filesystem APIs (no extra IPC, no dart:io). See PRD §22.

Build

The compiled web bundle that DevTools loads is not committed. Every fresh clone (and every rebuild after a change to this package's lib/, web/, or pubspec.yaml) must run:

./tool/build_devtools_extension.sh

The script runs dart run devtools_extensions build_and_copy twice and populates both packages/leonard_devtools/extension/devtools/build/ (used for standalone development) and packages/leonard_flutter/extension/devtools/build/ (the host package whose pubspec dep triggers DevTools auto-discovery in consumer apps such as sample_app).

CI runs the same script before analyze/test, so a PR that breaks the extension build fails at merge time — there is no committed-bundle drift to diff against.

Auto-discovery

The host package leonard_flutter ships extension/devtools/config.yaml, so any app whose pubspec transitively depends on leonard_flutter automatically surfaces the Leonard tab in standalone DevTools, the VS Code DevTools view, and the Android Studio DevTools view. A duplicate extension/devtools/config.yaml is kept inside this package for standalone development against the simulated DevTools environment.

Iterating on the panel

Two ways to run the panel while developing it:

Standalone web (fast iteration)

Use for widget work, layout, and form behavior — anything that does not depend on real DTD or real VM-service traffic. The devtools_extensions simulated environment supplies a fake DTD and a fake VM service, so lib/main.dart runs as a plain flutter run -d chrome web app: hot reload on save and source-level breakpoints both work, with no bundle rebuild (tool/build_devtools_extension.sh) in the loop.

• VS Code: launch the leonard_devtools (standalone web) config (group 4_devtools in .vscode/launch.json).
• CLI equivalent: flutter run -d chrome --dart-define=use_simulated_environment=true from packages/leonard_devtools/.

In-DevTools (real handshake)

Use to verify the real binding handshake, real /v1/models calls, and real session.run end-to-end. This runs the compiled bundle inside a real DevTools instance attached to sample_app.

• VS Code: launch the Dogfood: sample_app + leonard_cli compound (it runs the Build DevTools Extension preLaunchTask first). This starts the target app and CLI; open DevTools separately — click the DevTools URL printed in the Run console (or run dart devtools --vm-service-uri=<uri>) and open the Leonard tab.

Attaching a debugger

• Dart side: launch the leonard_devtools (standalone web) config and set breakpoints in packages/leonard_devtools/lib/** — Dart-Code owns the VM service for this target, so they bind immediately.
• Browser side: open Chrome DevTools on the served tab (the one flutter run -d chrome opened) — debug web builds ship source maps, so you can set breakpoints in the .dart sources from the Sources panel.

Minimum versions

• devtools_extensions: ^0.4.0 — pinned in pubspec.yaml.
• Flutter >= 3.41.0 — required by package:devtools_extensions and enforced via this package's environment constraint.
• DevTools shipped with the above Flutter releases (the IDE plugins follow the same channel).

PRD §22 captures the rationale for the in-panel architecture.

CORS for local MLX inference

The DevTools panel is served from DevTools' own web origin, so any browser-originated HTTP request to a local inference server (mlx-vlm, SGLang, vLLM) crosses an origin boundary and requires permissive CORS headers on the server side:

Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: GET,POST,OPTIONS
Access-Control-Allow-Headers: Content-Type,Authorization

Add these to the inference server's configuration (or the reverse proxy in front of it). Without them the panel's HTTP requests will fail with an opaque CORS error in the browser console even though the server is reachable.

Development

dart pub get -C packages/leonard_devtools
flutter test packages/leonard_devtools
dart analyze packages/leonard_devtools
./tool/check_no_dart_io.sh