# Prometheus v3.16.0

> Observability · 2026-11-05

This release changes several operator-visible defaults and validation rules, with substantial PromQL and histogram work. It also includes performance improvements and correctness fixes across storage, APIs, scraping, and remote write.

## Action needed
- **[breaking]** Deprecated Remote Write 2.0 metadata metrics
  - Remote Write 2.0 queues no longer expose the deprecated `prometheus_remote_storage_metadata_total`, `prometheus_remote_storage_metadata_failed_total`, `prometheus_remote_storage_metadata_retried_total`, and `prometheus_remote_storage_metadata_bytes_total` metrics.
- **[breaking]** Unique exemplar label names
  - Exemplars with duplicate label names are now rejected instead of being stored and returned with a duplicate JSON key from `/api/v1/query_exemplars`.
- **[breaking]** Stable `Smoothed` and `Anchored` vector selectors
  - `Smoothed` and `Anchored` vector selectors are now stable and always on.
- **[breaking]** Overflow validation for `timeout` and `lookback_delta`
  - Values for `timeout` and `lookback_delta` that overflow `int64` are now rejected instead of being converted into negative durations.
- **[breaking]** Future-dated exemplar handling
  - Exemplars with timestamps more than 10 minutes in the future are now dropped instead of being stored and blocking subsequent exemplars for the series.
- **[breaking]** Native histogram span offset validation
  - Native histograms whose span offsets overflow the `int32` bucket index are now rejected instead of being stored with corrupted buckets.

## Check if affected
- **[breaking]** The `batch_size` limit on experimental search endpoints
  - Applies if you use the experimental search endpoints.
  - The experimental search endpoints now clamp `batch_size` to 1000.
- **[breaking]** The `--web.external-url` default with TLS
  - Applies if you use `--web.config.file`.
  - When `--web.config.file` enables TLS, `--web.external-url` now defaults to `https`.
- **[breaking]** Sum-only classic histogram handling during `NHCB` conversion
  - Applies if you use `NHCB` conversion.
  - Sum-only classic histograms are now rejected during `NHCB` conversion.

## Other recorded changes
- 76 (defect_corrected 52, value_changed 14, added 10)

[Full analysis](https://ratatosk.io/en/releases/prometheus/v3.16.0)

[Original release notes](https://github.com/prometheus/prometheus/releases/tag/v3.16.0)