Result of a LetItCrash.Async.observe_async/1,2 block.

A Report records the async work that happened inside an observer block: which Tasks/processes were spawned, which completed, which crashed, which exceptions were caught by telemetry, plus timing data. The struct is the API — its fields are public and stable.

Three named assertions consume a Report:

• LetItCrash.Async.assert_no_silent_swallow/1,2
• LetItCrash.Async.assert_all_completed/2

(Idempotency uses a function-form assertion that does not consume a Report; see LetItCrash.Async.assert_idempotent/2.)

Fields

• :spawned — list of {pid, kind, started_at} for processes observed during the block. kind is :task | :unknown. started_at is in monotonic milliseconds.
• :completed — list of {pid, result, finished_at} for spawned work that finished cleanly. For trace-sourced entries (trace: true) result is the process exit reason (:normal / :shutdown / {:shutdown, _}), not the task's return value — tracing observes exits, not return values.
• :crashed — list of {pid, reason, finished_at} for spawned work that exited abnormally. reason is the exit reason, typically {exception, stacktrace} for a raised error.
• :exceptions — list of exception events seen during the block. Each entry is {event_name, measurements, metadata}. Telemetry events keep their upstream shape; trace-observed crashes are synthesized as {[:task, :exit], %{}, %{pid: pid, reason: reason}}.
• :warnings — list of atom hints from the observer. Includes :trace_unavailable when trace: true was requested but the owner was already traced by another tool. Usually empty.
• :duration_ms — wall-clock duration of the block in milliseconds.
• :started_at — monotonic time (ms) when the block started.
• :ended_at — monotonic time (ms) when the block ended.

Reports are pure data: no behavior beyond @type t/0.