• [FEATURE] PromQL: Add step(), and min() and max() on durations, behind feature flag promql-duration-expr. #16777
• [FEATURE] API: Add a /v1/status/tsdb/blocks endpoint exposing metadata about loaded blocks. #16695
• [FEATURE] Templates: Add toDuration() and now() functions. #16619
• [ENHANCEMENT] Discovery: Add support for attaching namespace metadata to targets. #16831
• [ENHANCEMENT] OTLP: Support new UnderscoreEscapingWithoutSuffixes strategy via otlp.translation_strategy. #16849
• [ENHANCEMENT] OTLP: Support including scope metadata as metric labels via otlp.promote_scope_metadata. #16878
• [ENHANCEMENT] OTLP: Add __type__ and __unit__ labels when feature flag type-and-unit-labels is enabled. #16630
• [ENHANCEMENT] Tracing: Send the traceparent HTTP header during scrapes. #16425
• [ENHANCEMENT] UI: Add option to disable info and warning query messages under Query page settings. #16901
• [ENHANCEMENT] UI: Improve metadata handling for _count/_sum/_bucket suffixes. #16910
• [PERF] PromQL: Improve performance due to internal optimizations. #16797
• [BUGFIX] Config: Fix "unknown global name escaping method" error messages produced during config validation. #16801
• [BUGFIX] Discovery: Fix race condition during shutdown. #16820
• [BUGFIX] OTLP: Generate target_info samples between the earliest and latest samples per resource. #16737
• [BUGFIX] PromQL: Fail when NaN is passed as parameter to topk(), bottomk(), limitk() and limit_ratio(). #16725
• [BUGFIX] PromQL: Fix extrapolation for native counter histograms. #16828
• [BUGFIX] PromQL: Reduce numerical errors by disabling some optimizations. #16895
• [BUGFIX] PromQL: Fix inconsistencies when using native histograms in subqueries. #16879
• [BUGFIX] PromQL: Fix inconsistent annotations for rate() and increase() on histograms when feature flag type-and-unit-labels is enabled. #16915
• [BUGFIX] Scraping: Fix memory corruption in slicelabels builds. #16946
• [BUGFIX] TSDB: Fix panic on append when feature flag created-timestamp-zero-ingestion is enabled. #16332
• [BUGFIX] TSDB: Fix panic on append for native histograms with empty buckets. #16893

3.5 is a Long Term Support (LTS) release; see release https://prometheus.io/docs/introduction/release-cycle/
There are a number of new features, and no known breaking changes in this release:

• [FEATURE] PromQL: Add experimental type and unit metadata labels, behind feature flag type-and-unit-labels. #16228 #16632 #16718 #16743
• [FEATURE] PromQL: Add ts_of_(min|max|last)_over_time, behind feature flag experimental-promql-functions. #16722 #16733
• [FEATURE] Scraping: Add global option always_scrape_classic_histograms to scrape a classic histogram even if it is also exposed as native. #16452
• [FEATURE] OTLP: New config options promote_all_resource_attributes and ignore_resource_attributes. #16426
• [FEATURE] Discovery: New service discovery for STACKIT Cloud. #16401
• [ENHANCEMENT] Hetzner SD: Add label_selector to filter servers. #16512
• [ENHANCEMENT] PromQL: support non-constant parameter in aggregations like quantile and topk. #16404
• [ENHANCEMENT] UI: Better total target count display when using keep_dropped_targets option. #16604
• [ENHANCEMENT] UI: Add simple filtering on the /rules page. #16605
• [ENHANCEMENT] UI: Display query stats in hover tooltip over table query tab. #16723
• [ENHANCEMENT] UI: Clear search field on /targets page. #16567
• [ENHANCEMENT] Rules: Check that rules parse without error earlier at startup. #16601
• [ENHANCEMENT] Promtool: Optional fuzzy float64 comparison in rules unittests. #16395
• [PERF] PromQL: Reuse histogramStatsIterator where possible. #16686
• [PERF] PromQL: Reuse storage for custom bucket values for native histograms. #16565
• [PERF] UI: Optimize memoization and search debouncing on /targets page. #16589
• [PERF] UI: Fix full-page re-rendering when opening status nav menu. #16590
• [PERF] Kubernetes SD: use service cache.Indexer to achieve better performance. #16365
• [PERF] TSDB: Optionally use Direct IO for chunks writing. #15365
• [PERF] TSDB: When fetching label values, stop work earlier if the limit is reached. #16158
• [PERF] Labels: Simpler/faster stringlabels encoding. #16069
• [PERF] Scraping: Reload scrape pools concurrently. #16595 #16783
• [BUGFIX] Top-level: Update GOGC before loading TSDB. #16491
• [BUGFIX] Config: Respect GOGC environment variable if no "runtime" block exists. #16558
• [BUGFIX] PromQL: Fix native histogram last_over_time. #16744
• [BUGFIX] PromQL: Fix reported parser position range in errors for aggregations wrapped in ParenExpr #16041 #16754
• [BUGFIX] PromQL: Don't emit a value from histogram_fraction or histogram_quantile if classic and native histograms are present at the same timestamp. #16552
• [BUGFIX] PromQL: Incorrect rounding of [1001ms] to [1s] and similar. #16478
• [BUGFIX] PromQL: Fix inconsistent / sometimes negative histogram_count and histogram_sum. #16682
• [BUGFIX] PromQL: Improve handling of NaNs in native histograms. #16724
• [BUGFIX] PromQL: Fix unary operator precedence in duration expressions. #16713
• [BUGFIX] PromQL: Improve consistency of avg aggregation and avg_over_time. #16569 #16773
• [BUGFIX] UI: Add query warnings and info to graph view. #16753 #16759
• [BUGFIX] API: Add HTTP Vary: Origin header to responses to avoid cache poisoning. #16008
• [BUGFIX] Discovery: Avoid deadlocks by taking locks in consistent order. #16587
• [BUGFIX] Remote-write: For Azure AD auth, allow empty client_id to suppport system assigned managed identity. #16421
• [BUGFIX] Scraping: Fix rare memory corruption bug. #16623
• [BUGFIX] Scraping: continue handling custom-bucket histograms after an exponential histogram is encountered. #16720
• [BUGFIX] OTLP: Default config not respected when otlp: block is unset. #16693

3.5 will be a Long Term Support (LTS) release; see release https://prometheus.io/docs/introduction/release-cycle/
There are a number of new features, and no known breaking changes in this release.

The following feature was removed since RC.1, since problems were discovered:

• [FEATURE] OTLP: Support promoting OTel scope name/version/schema URL/attributes as metric labels, via otlp.promote_scope_metadata. #16730 #16760

What's Changed

• [FEATURE] PromQL: Add experimental type and unit metadata labels, behind feature flag type-and-unit-labels. #16228 #16632 #16718 #16743
• [FEATURE] PromQL: Add ts_of_(min|max|last)_over_time, behind feature flag experimental-promql-functions. #16722 #16733
• [FEATURE] Scraping: Add global option always_scrape_classic_histograms to scrape a classic histogram even if it is also exposed as native. #16452
• [FEATURE] OTLP: New config options promote_all_resource_attributes and ignore_resource_attributes. #16426
• [FEATURE] Discovery: New service discovery for STACKIT Cloud. #16401
• [ENHANCEMENT] Hetzner SD: Add label_selector to filter servers. #16512
• [ENHANCEMENT] PromQL: support non-constant parameter in aggregations like quantile and topk. #16404
• [ENHANCEMENT] UI: Better total target count display when using keep_dropped_targets option. #16604
• [ENHANCEMENT] UI: Add simple filtering on the /rules page. #16605
• [ENHANCEMENT] UI: Display query stats in hover tooltip over table query tab. #16723
• [ENHANCEMENT] UI: Clear search field on /targets page. #16567
• [ENHANCEMENT] Rules: Check that rules parse without error earlier at startup. #16601
• [ENHANCEMENT] Promtool: Optional fuzzy float64 comparison in rules unittests. #16395
• [PERF] PromQL: Reuse histogramStatsIterator where possible. #16686
• [PERF] PromQL: Reuse storage for custom bucket values for native histograms. #16565
• [PERF] UI: Optimize memoization and search debouncing on /targets page. #16589
• [PERF] UI: Fix full-page re-rendering when opening status nav menu. #16590
• [PERF] Kubernetes SD: use service cache.Indexer to achieve better performance. #16365
• [PERF] TSDB: Optionally use Direct IO for chunks writing. #15365
• [PERF] TSDB: When fetching label values, stop work earlier if the limit is reached. #16158
• [PERF] Labels: Simpler/faster stringlabels encoding. #16069
• [PERF] Scraping: Reload scrape pools concurrently. #16595 #16783
• [BUGFIX] Top-level: Update GOGC before loading TSDB. #16491
• [BUGFIX] Config: Respect GOGC environment variable if no "runtime" block exists. #16558
• [BUGFIX] PromQL: Fix native histogram last_over_time. #16744
• [BUGFIX] PromQL: Fix reported parser position range in errors for aggregations wrapped in ParenExpr #16041 #16754
• [BUGFIX] PromQL: Don't emit a value from histogram_fraction or histogram_quantile if classic and native histograms are present at the same timestamp. #16552
• [BUGFIX] PromQL: Incorrect rounding of [1001ms] to [1s] and similar. #16478
• [BUGFIX] PromQL: Fix inconsistent / sometimes negative histogram_count and histogram_sum. #16682
• [BUGFIX] PromQL: Improve handling of NaNs in native histograms. #16724
• [BUGFIX] PromQL: Fix unary operator precedence in duration expressions. #16713
• [BUGFIX] PromQL: Improve consistency of avg aggregation and avg_over_time. #16569 #16773
• [BUGFIX] UI: Add query warnings and info to graph view. #16753 #16759
• [BUGFIX] API: Add HTTP Vary: Origin header to responses to avoid cache poisoning. #16008
• [BUGFIX] Discovery: Avoid deadlocks by taking locks in consistent order. #16587
• [BUGFIX] Remote-write: For Azure AD auth, allow empty client_id to suppport system assigned managed identity. #16421
• [BUGFIX] Scraping: Fix rare memory corruption bug. #16623
• [BUGFIX] Scraping: continue handling custom-bucket histograms after an exponential histogram is encountered. #16720
• [BUGFIX] OTLP: Default config not respected when otlp: block is unset. #16693

3.5 will be a Long Term Support (LTS) release; see release https://prometheus.io/docs/introduction/release-cycle/
There are a number of new features, and no known breaking changes in this release.

What's Changed

• [FEATURE] PromQL: Add experimental type and unit metadata labels, behind feature flag type-and-unit-labels. #16228 #16632 #16718 #16743
• [FEATURE] PromQL: Add ts_of_(min|max|last)_over_time, behind feature flag experimental-promql-functions. #16722 #16733
• [FEATURE] Scraping: Add global option always_scrape_classic_histograms to scrape a classic histogram even if it is also exposed as native. #16452
• [FEATURE] OTLP: Support promoting OTel scope name/version/schema URL/attributes as metric labels, via otlp.promote_scope_metadata. #16730 #16760
• [FEATURE] OTLP: New config options promote_all_resource_attributes and ignore_resource_attributes. #16426
• [FEATURE] Discovery: New service discovery for STACKIT Cloud. #16401
• [ENHANCEMENT] Hetzner SD: Add label_selector to filter servers. #16512
• [ENHANCEMENT] PromQL: support non-constant parameter in aggregations like quantile and topk. #16404
• [ENHANCEMENT] UI: Better total target count display when using keep_dropped_targets option. #16604
• [ENHANCEMENT] UI: Add simple filtering on the /rules page. #16605
• [ENHANCEMENT] UI: Display query stats in hover tooltip over table query tab. #16723
• [ENHANCEMENT] UI: Clear search field on /targets page. #16567
• [ENHANCEMENT] Rules: Check that rules parse without error earlier at startup. #16601
• [ENHANCEMENT] Promtool: Optional fuzzy float64 comparison in rules unittests. #16395
• [PERF] PromQL: Reuse histogramStatsIterator where possible. #16686
• [PERF] PromQL: Reuse storage for custom bucket values for native histograms. #16565
• [PERF] UI: Optimize memoization and search debouncing on /targets page. #16589
• [PERF] UI: Fix full-page re-rendering when opening status nav menu. #16590
• [PERF] Kubernetes SD: use service cache.Indexer to achieve better performance. #16365
• [PERF] TSDB: Optionally use Direct IO for chunks writing. #15365
• [PERF] TSDB: When fetching label values, stop work earlier if the limit is reached. #16158
• [PERF] Labels: Simpler/faster stringlabels encoding. #16069
• [PERF] Scraping: Reload scrape pools concurrently. #16595 #16783
• [BUGFIX] Top-level: Update GOGC before loading TSDB. #16491
• [BUGFIX] Config: Respect GOGC environment variable if no "runtime" block exists. #16558
• [BUGFIX] PromQL: Fix native histogram last_over_time. #16744
• [BUGFIX] PromQL: Fix reported parser position range in errors for aggregations wrapped in ParenExpr #16041 #16754
• [BUGFIX] PromQL: Don't emit a value from histogram_fraction or histogram_quantile if classic and native histograms are present at the same timestamp. #16552
• [BUGFIX] PromQL: Incorrect rounding of [1001ms] to [1s] and similar. #16478
• [BUGFIX] PromQL: Fix inconsistent / sometimes negative histogram_count and histogram_sum. #16682
• [BUGFIX] PromQL: Improve handling of NaNs in native histograms. #16724
• [BUGFIX] PromQL: Fix unary operator precedence in duration expressions. #16713
• [BUGFIX] PromQL: Improve consistency of avg aggregation and avg_over_time. #16569 #16773
• [BUGFIX] UI: Add query warnings and info to graph view. #16753 #16759
• [BUGFIX] API: Add HTTP Vary: Origin header to responses to avoid cache poisoning. #16008
• [BUGFIX] Discovery: Avoid deadlocks by taking locks in consistent order. #16587
• [BUGFIX] Remote-write: For Azure AD auth, allow empty client_id to suppport system assigned managed identity. #16421
• [BUGFIX] Scraping: Fix rare memory corruption bug. #16623
• [BUGFIX] Scraping: continue handling custom-bucket histograms after an exponential histogram is encountered. #16720
• [BUGFIX] OTLP: Default config not respected when otlp: block is unset. #16693

[LTS patch release]

• [ENHANCEMENT] TSDB: Add backward compatibility with the upcoming TSDB block index v3 #16762
• [BUGFIX] Top-level: Update GOGC before loading TSDB #16521

• [BUGFIX] OTLP receiver: Fix default configuration not being respected if the otlp: block is unset in the config file. #16693

• [BUGFIX] Parser: Add reproducer for a dangling-reference issue in parsers. #16633

• [CHANGE] Config: Make setting out-of-order native histograms feature (--enable-feature=ooo-native-histograms) a no-op. Out-of-order native histograms are now always enabled when out_of_order_time_window is greater than zero and --enable-feature=native-histograms is set. #16207
• [FEATURE] OTLP translate: Add feature flag for optionally translating OTel explicit bucket histograms into native histograms with custom buckets. #15850
• [FEATURE] OTLP translate: Add option to receive OTLP metrics without translating names or attributes. #16441
• [FEATURE] PromQL: allow arithmetic operations in durations in PromQL parser. #16249
• [FEATURE] OTLP receiver: Add primitive support for ingesting OTLP delta metrics as-is. #16360
• [ENHANCEMENT] PromQL: histogram_fraction for bucket histograms. #16095
• [ENHANCEMENT] TSDB: add prometheus_tsdb_wal_replay_unknown_refs_total and prometheus_tsdb_wbl_replay_unknown_refs_total metrics to track unknown series references during WAL/WBL replay. #16166
• [ENHANCEMENT] Scraping: Add config option for escaping scheme request. #16066
• [ENHANCEMENT] Config: Add global config option for convert_classic_histograms_to_nhcb. #16226
• [ENHANCEMENT] Alerting: make batch size configurable (--alertmanager.notification-batch-size). #16254
• [PERF] Kubernetes SD: make endpointSlice discovery more efficient. #16433
• [BUGFIX] Config: Fix auto-reload on changes to rule and scrape config files. #16340
• [BUGFIX] Scraping: Skip native histogram series if ingestion is disabled. #16218
• [BUGFIX] TSDB: Handle metadata/tombstones/exemplars for duplicate series during WAL replay. #16231
• [BUGFIX] TSDB: Avoid processing exemplars outside the valid time range during WAL replay. #16242
• [BUGFIX] Promtool: Add feature flags for PromQL features. #16443
• [BUGFIX] Rules: correct logging of alert name & template data. #15093
• [BUGFIX] PromQL: Use arithmetic mean for histogram_stddev() and histogram_stdvar() . #16444

• [CHANGE] Config: Make setting out-of-order native histograms feature (--enable-feature=ooo-native-histograms) a no-op. Out-of-order native histograms are now always enabled when out_of_order_time_window is greater than zero and --enable-feature=native-histograms is set. #16207
• [FEATURE] OTLP translate: Add feature flag for optionally translating OTel explicit bucket histograms into native histograms with custom buckets. #15850
• [FEATURE] OTLP translate: Add option to receive OTLP metrics without translating names or attributes. #16441
• [FEATURE] PromQL: allow arithmetic operations in durations in PromQL parser. #16249
• [FEATURE] OTLP receiver: Add primitive support for ingesting OTLP delta metrics as-is. #16360
• [ENHANCEMENT] PromQL: histogram_fraction for bucket histograms. #16095
• [ENHANCEMENT] TSDB: add prometheus_tsdb_wal_replay_unknown_refs_total and prometheus_tsdb_wbl_replay_unknown_refs_total metrics to track unknown series references during WAL/WBL replay. #16166
• [ENHANCEMENT] Scraping: Add config option for escaping scheme request. #16066
• [ENHANCEMENT] Config: Add global config option for convert_classic_histograms_to_nhcb. #16226
• [ENHANCEMENT] Alerting: make batch size configurable (--alertmanager.notification-batch-size). #16254
• [PERF] Kubernetes SD: make endpointSlice discovery more efficient. #16433
• [BUGFIX] Config: Fix auto-reload on changes to rule and scrape config files. #16340
• [BUGFIX] Scraping: Skip native histogram series if ingestion is disabled. #16218
• [BUGFIX] TSDB: Handle metadata/tombstones/exemplars for duplicate series during WAL replay. #16231
• [BUGFIX] TSDB: Avoid processing exemplars outside the valid time range during WAL replay. #16242
• [BUGFIX] Promtool: Add feature flags for PromQL features. #16443
• [BUGFIX] Rules: correct logging of alert name & template data. #15093
• [BUGFIX] PromQL: Use arithmetic mean for histogram_stddev() and histogram_stdvar() . #16444

• [BUGFIX] Azure SD: Fix panic on malformed log message. #16434 #16210
• [BUGFIX] Config: Update GOGC before loading TSDB. #16491