vercel__workflow/.changeset/pre/stream-write-flush-span.md

@workflow/core, @workflow/world-vercel

@workflow/core	@workflow/world-vercel
patch	patch

Emit a client-observed workflow.stream.flush span per stream-write batch, with a buffer_dwell_ms attribute separating client-side batching cost from network/server time. Log under DEBUG=workflow:* when @opentelemetry/api fails to load in world-vercel.