Requires juice ^1.10.0 (LevelAwareJuiceLogger).

Changed — DevtoolsJuiceLogger: the cost follows the listener #

• Payloads are built and posted only while the VM's Extension stream has a listener (dart:developer extensionStreamHasListener). postEvent already dropped events nobody would receive; the logger built each payload first — including the state's toString() on every emission. Now it builds nothing for nobody. The inner logger still receives every call, errors included.
• It declares its level to the framework (LevelAwareJuiceLogger): Level.all while a listener is attached, otherwise what the inner logger declares. With the default inner logger, a release build or an app launched without tooling builds no per-event telemetry at all; attaching DevTools mid-run turns it on live. Under flutter run the tooling daemon is a listener, so nothing changes there.
• New test seam hasListener: beside post:. Injecting post alone keeps the listener present, so existing captures are unaffected.

Changed — every builder now declares its EventConcurrency mode #

• 0.2.0 made RecordError / AddBreadcrumb sequential and left four builders bare. Now explicit: InitializeObservabilityEvent → droppable; SetUserEvent, SetContextEvent, SetEnabledEvent → sequential (the two that fan out to reporters await them; they now complete in the order the calls were made — the analytics precedent).
• DevTools extension config.yaml version aligned to the package (the panel header read "v0.1.0" on 0.4.0).

Tests #

• Gated-reporter coverage: a second setUser does not start its fan-out until the first completes.

New Features #

DevTools extension — Juice telemetry, visualized

Ships a DevTools extension (extension/devtools/) that consumes the juice:<type> events DevtoolsJuiceLogger posts and renders four views: Timeline (every transition, newest last), Spans (use-case executions paired by executionId — honest durations even under concurrent overlap, running/failed/elapsed), Blocs (per-bloc emission count with the rebuild GROUPS each emission targeted — the rebuild inspector groups make explainable), and Problems (errors, unhandled events, leak detection). Loads automatically when a Juice app using DevtoolsJuiceLogger connects to DevTools; a live-filter box and clear across all four.

Source: packages/juice_observability_devtools_extension (publish_to: none). The model is a pure TelemetryModel (7 unit tests, no VM); the live TelemetryStore adds the VM wiring, split because devtools_extensions is web-only.

• Docs: README now actually introduces DevtoolsJuiceLogger (0.3.0's headline was missing from the pub.flutter-io.cn page) and the install snippet is current. Requires juice ^1.7.0 so the span pairing documented here is structural, not aspirational.
• Example: demonstrates the mirror IN FULL — a Juice-pure TelemetryFeedBloc fed through the injectable post seam (teeing to the real VM post and an in-app panel), so every tap shows its use_case_execution → use_case_completed pair with executionId and elapsed time, no DevTools required. Teaches the self-loop guard (isSelfTelemetry): a bloc that consumes telemetry must filter out its own. Example tests cover the formatter, the guard, and a real start/end pair.

New Features #

DevtoolsJuiceLogger — the framework's telemetry, live in DevTools

A JuiceLogger decorator that mirrors Juice's existing structured log entries (use-case executions, state emissions, bloc lifecycle, event subscriptions, unhandled events, leak detection, and all error types) to the VM's extension-event stream via dart:developer postEvent, as juice:<type> events — consumable live by DevTools and any VM-service listener. A mirror on the existing logger seam, not new instrumentation:

• Typed entries (context['type']) post as juice:<type>; untyped chatter stays console-only; errors without a type always post as juice:error.
• Wire-safe payloads: primitives pass through; live objects (states, blocs, group sets) cross as toString capped at 512 chars.
• Decorates any inner logger (default DefaultJuiceLogger) — console logging keeps working; the post function is an injectable seam for tests.
• Phase 1 is instant events by design; duration spans await a use_case_completed entry in core (ROADMAP: BlocSignal tee-up, item 1).

One line to adopt: JuiceLoggerConfig.configureLogger(DevtoolsJuiceLogger()).

Changed #

• Requires juice ^1.5.0.
• Adopt EventConcurrency.sequential for RecordErrorEvent and AddBreadcrumbEvent. The breadcrumb ring and error counter now live in state with a natural read-modify-write; the bloc-side accumulator workaround (_breadcrumbs/_errorCount + helpers) is removed. Behavior unchanged — rapid breadcrumbs/errors stay race-free, now via the framework mode.

Added #

• Initial release.
• ObservabilityBloc — crash reporting + breadcrumbs, fanned out to one or more reporters.
• Global capture — installs FlutterError.onError + PlatformDispatcher.onError (chaining any existing handlers; restored on close) so uncaught errors are reported automatically.
• CrashReporter — vendor seam (recordError/addBreadcrumb/setUser/ setContext). Ship a Sentry/Crashlytics adapter; ConsoleCrashReporter and NoopCrashReporter included.
• Breadcrumb ring — bounded trail (maxBreadcrumbs) attached to each report.
• Fan-out with isolation — a throwing reporter can't break the others.
• API — recordError, breadcrumb, setUser, setContext, setEnabled.
• Rebuild group — observability:status.