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Prometheus 3.16 ships GA with query cost limits behind a flag and stable Smoothed/Anchored selectors

promqlquery-costtsdbremote-writeobservability
◆Current state
Prometheus 3.16.0 went GA on 4 November after four release candidates. It makes Smoothed and Anchored vector selectors stable and always-on, adds experimental query cost estimation with configurable execution limits, an experimental integral() function, per-query start-timestamp overrides and metadata-wal-records in Agent mode. The rest is TSDB correctness fixes for out-of-order samples and a long list of scrape and remote-write performance work.
◆Where it's heading
The 3.16 cycle makes PromQL cost measurable before making it enforceable: subquery samples now count toward statistics, and limits ship behind --enable-feature=query-cost. Remote Write 2.0 keeps dropping legacy metadata metrics, and the 3.15.x and 3.13 LTS lines move separately on security rebuilds.
◆Prediction
Expect 3.15.x and 3.13.x security patches next and a 3.17 rc within weeks; whether query-cost leaves its flag depends on feedback the entries do not yet show.

◆Recent moves

  1. 4d ago

    Prometheus 3.16 GA: query cost limits, stable smoothed selectors

    The GA confirms the rc.2–rc.4 feature set unchanged: stable Smoothed and Anchored selectors, flag-gated query cost limits and an experimental integral(). Operators get real guardrails against expensive queries, but only after opting in, so the default behavior barely moves.

    View source ↗
  2. 6d ago

    3.16.0-rc.4: integral() function, stricter sample accounting

    The fourth 3.16 candidate adds an experimental integral() function and per-query start-timestamp overrides, and makes subquery samples count toward query statistics. The accounting change matters because the query cost limits added in rc.2 depend on those counts being right.

    View source ↗
  3. 12d ago

    3.16.0-rc.2: query cost limits, smoothed selectors go stable

    The 3.16 candidate makes Smoothed and Anchored selectors stable and always-on and adds flag-gated query cost estimation with execution limits. Most of the remaining notes are TSDB, OTLP and OpenMetrics 2.0 corrections, which fits a line spending its effort on accuracy and cost.

    View source ↗
  4. 19d ago

    3.15.1: distrusts two root CAs, patches Go and HTTP/2

    Security rebuild for the 3.15 line: container images distrust two root CAs after the eMudhra key compromise, and Go and x/net move to patched versions. A scrape target chained to a distrusted root could fail TLS verification in these images.

    View source ↗
  5. 19d ago

    3.13.5: LTS gets the CA distrust and Go security rebuild

    The 3.13 LTS track gets the same CA distrust and Go fixes as 3.15.1, plus an OpenTelemetry bump that stops exporter endpoint URLs leaking into info logs. Building from source now requires Go 1.26.

    View source ↗
  6. 1mo ago

    3.13.4: gRPC fix, native histogram corrections on LTS

    An LTS patch with a gRPC memory-exhaustion fix and repairs for float native histograms in federation and scraping. Agent mode also ignores unknown WAL records, which allows rollback from newer versions.

    View source ↗