Read-side registry rebuilds re-run the unified metric sync as often as every two seconds, so one poll observation was re-written many times between polls. The metrics store upserts on (resource, metric, tier, timestamp), so each replay UPDATEs the same row and commits a fresh transaction for no new data, churning the SQLite WAL and driving the disk-write amplification reported in #1966.
Track the last sample handed to the store per series and skip exact timestamp+value repeats before the batch is enqueued. A corrected value at the same observation time is still written, so the guard cannot mask a real change. Record the behaviour in the monitoring and agent-lifecycle contracts and move the focused regression into the accepted monitor.go proof file.
Change-source: pulse-maintainer
pulse-triage[bot]
df44238797