Reject bad optional metadata without dropping the core event

When a provider adds optional timing or diagnostic fields to an otherwise valid event, validate those fields separately from the event's required protocol contract. If the optional values are missing, malformed, reversed, or overflow during unit conversion, discard only the derived evidence and preserve the usable event. Record a content-free rejection status for audit. Required identity and sequence violations must still fail normally; this rule applies only to ancillary evidence. Otherwise an observability feature can silently become a live-call outage path.

Applies when: enriching streaming events with optional provenance fields used by evaluation or telemetry. Keywords: optional metadata streaming protocol validation fail closed transcript continuity overflow diagnostic