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• v0.4.0 4ea7463089

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  feat(observe)!: unify journal and trace into single observation pipeline

  swaits released this 2026-04-28 15:24:14 -06:00 | 19 commits to main since this release

  The codegen now emits one __chart_observe! invocation per observable
  atom. The macro fans out at compile time to whichever sinks are enabled:
  the in-memory journal (feature = "journal"), defmt (trace-defmt),
  log (trace-log), and/or tracing (trace-tracing). Trace and
  journal share the same vocabulary by construction — they cannot
  diverge. With no sink feature on, every site expands to () (zero
  overhead). Multiple trace backends now compose; previously they were
  mutually exclusive.

  Trace lines use a logfmt-style format with a [statechart:Name] prefix
  and key=value pairs, machine-parseable and greppable. Twenty verbs
  cover every observable atom — entries/exits with begin/end pairs,
  actions with kind, durings, transitions with the reason that triggered
  them, event lifecycle (received/delivered/dropped/queued/failed),
  timers, and termination.

  BREAKING CHANGES (chart syntax unchanged; observability surface only):

  • TraceEvent::TransitionFired now carries reason: TransitionReason
    showing whether the transition was driven by an event, a timer, or
    internal logic.
  • New TraceEvent variants for phase pairing: EnterBegan, ExitBegan,
    TransitionComplete, EventReceived.
  • Trace prefix changed from [Name] to [statechart:Name].
  • The chart-level trace; keyword is parsed for backwards compatibility
    but no longer gates emission.
  • __chart_trace! / __chart_journal! macros removed (doc-hidden).

  Verification: 159 integration tests pass, 0 missed mutants, miri 68
  tests clean, Creusot 14/14 VCs discharged. Zero overhead confirmed via
  cargo expand — every observation site expands to {} with no sinks
  enabled.

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