Under the hood
Fetched subagent transcripts can be written create-only so a locally-written copy is not clobbered.
The lazy subagent-transcript fetch path now tracks whether a subagent's transcript was already written locally (agentIdsWrittenLocally/hasWrittenAgentLocally) separately from whether it was already fetched. Writing a fetched transcript can pass createOnly to avoid clobbering a locally-written version, returning distinguishable outcomes like exists, written, or backend_no_create. The subagent_lazy_fetch telemetry event now includes a written_locally field.