##### [\`v3.9.0\`](https://github.com/prometheus/prometheus/releases/tag/v3.9.0)

#### Note for users of Native Histograms

In version 3.9, Native Histograms is no longer experimental, and the feature flag `native-histogram` has no effect.  You must now turn on
the config setting `scrape_native_histograms` to collect Native Histogram samples from exporters.

#### Changelog

- \[CHANGE] Native Histograms are no longer experimental! Make the `native-histogram` feature flag a no-op. Use `scrape_native_histograms` config option instead. [#17528](prometheus/prometheus#17528)
- \[CHANGE] API: Add maximum limit of 10,000 sets of statistics to TSDB status endpoint. [#17647](prometheus/prometheus#17647)
- \[FEATURE] API: Add /api/v1/features for clients to understand which features are supported. [#17427](prometheus/prometheus#17427)
- \[FEATURE] Promtool: Add `start_timestamp` field for unit tests. [#17636](prometheus/prometheus#17636)
- \[FEATURE] Promtool: Add `--format seriesjson` option to `tsdb dump` to output just series labels in JSON format. [#13409](prometheus/prometheus#13409)
- \[FEATURE] Add `--storage.tsdb.delay-compact-file.path` flag for better interoperability with Thanos. [#17435](prometheus/prometheus#17435)
- \[FEATURE] UI: Add an option on the query drop-down menu to duplicate that query panel. [#17714](prometheus/prometheus#17714)
- \[ENHANCEMENT]: TSDB: add flag `--storage.tsdb.block-reload-interval` to configure TSDB Block Reload Interval. [#16728](prometheus/prometheus#16728)
- \[ENHANCEMENT] UI: Add graph option to start the chart's Y axis at zero. [#17565](prometheus/prometheus#17565)
- \[ENHANCEMENT] Scraping: Classic protobuf format no longer requires the unit in the metric name. [#16834](prometheus/prometheus#16834)
- \[ENHANCEMENT] PromQL, Rules, SD, Scraping: Add native histograms to complement existing summaries. [#17374](prometheus/prometheus#17374)
- \[ENHANCEMENT] Notifications: Add a histogram `prometheus_notifications_latency_histogram_seconds` to complement the existing summary. [#16637](prometheus/prometheus#16637)
- \[ENHANCEMENT] Remote-write: Add custom scope support for AzureAD authentication. [#17483](prometheus/prometheus#17483)
- \[ENHANCEMENT] SD: add a `config` label with job name for most `prometheus_sd_refresh` metrics. [#17138](prometheus/prometheus#17138)
- \[ENHANCEMENT] TSDB: New histogram `prometheus_tsdb_sample_ooo_delta`, the distribution of out-of-order samples in seconds. Collected for all samples, accepted or not. [#17477](prometheus/prometheus#17477)
- \[ENHANCEMENT] Remote-read: Validate histograms received via remote-read. [#17561](prometheus/prometheus#17561)
- \[PERF] TSDB: Small optimizations to postings index. [#17439](prometheus/prometheus#17439)
- \[PERF] Scraping: Speed up relabelling of series. [#17530](prometheus/prometheus#17530)
- \[PERF] PromQL: Small optimisations in binary operators. [#17524](prometheus/prometheus#17524), [#17519](prometheus/prometheus#17519).
- \[BUGFIX] UI: PromQL autocomplete now shows the correct type and HELP text for OpenMetrics counters whose samples end in `_total`. [#17682](prometheus/prometheus#17682)
- \[BUGFIX] UI: Fixed codemirror-promql incorrectly showing label completion suggestions after the closing curly brace of a vector selector. [#17602](prometheus/prometheus#17602)
- \[BUGFIX] UI: Query editor no longer suggests a duration unit if one is already present after a number. [#17605](prometheus/prometheus#17605)
- \[BUGFIX] PromQL: Fix some "vector cannot contain metrics with the same labelset" errors when experimental delayed name removal is enabled. [#17678](prometheus/prometheus#17678)
- \[BUGFIX] PromQL: Fix possible corruption of PromQL text if the query had an empty `ignoring()` and non-empty grouping. [#17643](prometheus/prometheus#17643)
- \[BUGFIX] PromQL: Fix resets/changes to return empty results for anchored selectors when all samples are outside the range. [#17479](prometheus/prometheus#17479)
- \[BUGFIX] PromQL: Check more consistently for many-to-one matching in filter binary operators. [#17668](prometheus/prometheus#17668)
- \[BUGFIX] PromQL: Fix collision in unary negation with non-overlapping series. [#17708](prometheus/prometheus#17708)
- \[BUGFIX] PromQL: Fix collision in label\_join and label\_replace with non-overlapping series. [#17703](prometheus/prometheus#17703)
- \[BUGFIX] PromQL: Fix bug with inconsistent results for queries with OR expression when experimental delayed name removal is enabled. [#17161](prometheus/prometheus#17161)
- \[BUGFIX] PromQL: Ensure that `rate`/`increase`/`delta` of histograms results in a gauge histogram. [#17608](prometheus/prometheus#17608)
- \[BUGFIX] PromQL: Do not panic while iterating over invalid histograms. [#17559](prometheus/prometheus#17559)
- \[BUGFIX] TSDB: Reject chunk files whose encoded chunk length overflows int. [#17533](prometheus/prometheus#17533)
- \[BUGFIX] TSDB: Do not panic during resolution reduction of invalid histograms. [#17561](prometheus/prometheus#17561)
- \[BUGFIX] Remote-write Receive: Avoid duplicate labels when experimental type-and-unit-label feature is enabled. [#17546](prometheus/prometheus#17546)
- \[BUGFIX] OTLP Receiver: Only write metadata to disk when experimental metadata-wal-records feature is enabled. [#17472](prometheus/prometheus#17472)