Prometheus

• [CHANGE] PromQL: A range query whose end was not aligned to step caused subqueries inside it to evaluate past the parent's last actual step, inflating peakSamples in the query stats and against the query.max-samples limit, and wasting storage I/O reading samples that were never used in the result. Add tests to prevent regression of the fix made in #18081. #18598
• [CHANGE] PromQL: Do not register a start timestamp reset if the start timestamp hasn't changed between subsequent samples. #19454
• [CHANGE] Logging: Deprecate --log.level; use runtime.log_level configuration to supply the default level. #19511
• [FEATURE] Configuration: Allow changing the process log level through runtime.log_level on configuration reload. #19511
• [FEATURE] Prometheus: Add --auto-gomemlimit.refresh-interval flag to periodically re-detect the container or system memory limit and update GOMEMLIMIT at runtime. #18843
• [FEATURE] Scraping: Add support for scraping targets via Unix Domain Sockets. #12024. #18091
• [FEATURE] scrape: Implement OM2.0 scrape format. #18606
• [ENHANCEMENT] Reduce TSDB head CPU utilization when initializing. #18001
• [ENHANCEMENT] Docker SD: Add labels __meta_docker_container_image and __meta_docker_container_image_id. #19386
• [ENHANCEMENT] Mixin: Add a p95/p99 remote-write send-batch latency panel to the remote-write dashboard. #19500
• [ENHANCEMENT] Mixin: Support native histograms in the remote-write send-batch latency panel. #19522
• [ENHANCEMENT] PromQL/TSDB: The --enable-feature=st-storage flag now automatically enables XOR2 float chunk encoding and ST-capable histogram chunk encoding, so you no longer need to pass xor2-encoding and histograms-st-encoding alongside it. #19518
• [ENHANCEMENT] Remote write / Alertmanager: upgrade sigv4 to v0.5.0, adding session_name and tags fields for STS AssumeRole sessions. The previously undocumented service_name field is now also documented. #19569
• [ENHANCEMENT] Scraping: Support zstd-compressed scrape responses, enabled via feature flag zstd-scrape. #19502
• [ENHANCEMENT] TSDB: Stabilize the XOR2 float chunk encoding. --enable-feature=xor2-encoding is deprecated; use storage.tsdb.chunk_encoding.floats: xor2 instead. Check that other software reading the TSDB directly (e.g. Thanos sidecar) supports XOR2 before enabling. #19461
• [ENHANCEMENT] TSDB: add prometheus_tsdb_head_appenders_created_total metric. #19411
• [ENHANCEMENT] Tracing: add more spans to scrapes, API queries and rule evaluations. #19410
• [ENHANCEMENT] UI: Show the effective configuration for each scrape pool on the Targets and Service Discovery pages. #19384
• [ENHANCEMENT] scrape: Enable start time synthesis for summary _count and _sum series in scrape appender v2. #19323
• [ENHANCEMENT] scrape: stop all pools in parallel for faster shutdowns. #19295
• [ENHANCEMENT] storage/remote: Add undocumented failed_request_logging config field to debug log remote write V2 requests on send errors. #19249
• [ENHANCEMENT] TSDB: Add fast path for XOR chunk decompression to speed up queries. #18049
• [ENHANCEMENT] UI: Improve native histogram table formatting and add a background bar indicating the bucket count. #19332
• [ENHANCEMENT] TSDB: Add prometheus_tsdb_head_series_pending_commit_underflow_total to report pending-sample reservation underflows. #19470
• [PERF] AWS SD: Build RDS cluster labels once per cluster instead of once per instance. #19504
• [PERF] AWS SD: Describe RDS instances of different clusters concurrently, bounded by request_concurrency. #19506
• [PERF] AWS SD: Describe each ElastiCache resource once per refresh instead of twice. #19585
• [PERF] Remote read: Avoid cloning labels for sampled reads when no external labels are configured. #19503
• [PERF] Remote write: Reuse OTLP converter scratch state between requests. #19388
• [PERF] scrape: conversion from classic to native histograms should only parse start times when enabled. #19446
• [BUGFIX] PromQL: Fix info() enrichment for composite expressions with mixed @/offset references or selector-free vector branches, preventing metadata from being evaluated at an unrelated timestamp. #19387
• [BUGFIX] PromQL: Fix info() enrichment when input series use different subsets of identifying labels. #19557
• [BUGFIX] PromQL: Preserve metric-name dropping through the info function when delayed name removal is enabled. #19413
• [BUGFIX] TSDB: Don't silently drop samples when head garbage collection removes a series while it is being appended to. #19272
• [BUGFIX] TSDB: Keep series with uncommitted samples during selected- and stale-series compaction, including when appenders overlap. #19470
• [BUGFIX] TSDB: Do not retain head series after a synthetic start-timestamp zero sample is rejected. #19470
• [BUGFIX] TSDB: Prevent query panics during series eviction after WAL replay. #19664
• [BUGFIX] TSDB: fix potential deadlock between mmapSeriesChunks and gcSeries. #19460
• [BUGFIX] TSDB: fix default block reload interval for custom options. #19368
• [BUGFIX] AWS SD: Do not crash on serverless MSK clusters or MSK clusters without Open Monitoring. #19194
• [BUGFIX] AWS SD: Do not panic when the ElastiCache API omits optional fields of a serverless cache or cache cluster. #19435
• [BUGFIX] AWS SD: Reject non-positive request_concurrency instead of hanging service discovery indefinitely. #19524
• [BUGFIX] Discovery/AWS: Avoid a panic when discovering standalone ECS tasks with custom task groups. #19302
• [BUGFIX] Discovery: Do not panic in AWS Lightsail service discovery when an instance is missing optional fields such as availability zone, blueprint, bundle, name, state or support code. #19324
• [BUGFIX] Discovery: delete the stale prometheus_sd_last_update_timestamp_seconds series for a config that is removed on reload. #19131
• [BUGFIX] HTTP: Avoid truncating compressed responses when handlers set Content-Length. #19661
• [BUGFIX] IONOS SD: Do not panic when the API response omits the server, NIC or volume collections, or a server's properties. #19438
• [BUGFIX] Metadata will not affect the number of Remote Write v2 shards. #19218
• [BUGFIX] Mixins: Fix label mismatches that prevented PrometheusHAGroupNotIngestingSamples and PrometheusHAGroupCrashlooping from firing. #19444
• [BUGFIX] Native histograms: DetectReset no longer misses a counter reset when a populated bucket behind an empty one disappears, which could make histogram rate()/increase() undercount. #19367
• [BUGFIX] Never skip histogram buckets for histogram_stddev and histogram_stdvar functions. #19521
• [BUGFIX] OTLP: Do not abort an entire OTLP payload ingestion if one metric has no datapoints. #19343
• [BUGFIX] PromQL: Fix FastRegexMatcher false-positive match when a capturing group is directly adjacent to a literal (e.g. .*\|(foo)\|.*). #19516
• [BUGFIX] PromQL: Fix a panic in range selectors using the experimental anchored or smoothed modifier when the selected series has no samples inside the query window, for example a query evaluated inside a scrape gap. #19431
• [BUGFIX] PromQL: Fix empty results when a subquery with @ is used as the matrix argument of a call that is not step-invariant (for example quantile_over_time(scalar(x), metric[...:...] @ T)). #19187
• [BUGFIX] PromQL: Make the "found duplicate series for the match group" many-to-many matching error message deterministic by sorting the two duplicate labels. #18810
• [BUGFIX] PromQL: Preserve parentheses around duration literals on Expr.String() round-trip. #19403
• [BUGFIX] PromQL: Reject duration-expression offsets and @ start() / @ end() before range selectors, matching the existing rejection of literal offsets and @ <timestamp>. #19406
• [BUGFIX] PromQL: Report the position of the histogram argument rather than of a scalar argument in the native histogram NaN observation annotations of histogram_quantile and histogram_fraction. #19330
• [BUGFIX] PromQL: info() now applies the @ modifier/offset when evaluating the info series, so info(v @ T) enriches as of T consistently instead of depending on the query start/eval time. #19266
• [BUGFIX] Rules: Fix a panic when a rule manager created without a logger loads a rule file containing multiple YAML documents. #19433
• [BUGFIX] Scrape: Do not append a stale marker for a series that is still exposed when the storage returns a new series reference for it. #19328
• [BUGFIX] Scrape: JSON log formatter correctly format scrape target info. #19472
• [BUGFIX] TSDB: Fix in-order chunk ID overflow by wrapping head chunk IDs modulo 2^23 so they never collide with the out-of-order flag bit. #19450
• [BUGFIX] TSDB: Fix out-of-order chunk ID overflow by wrapping firstOOOChunkID modulo 2^23 instead of growing unbounded. #19216
• [BUGFIX] UI: Remove an extraneous X-axis tick mark in the native histogram chart when using the "linear" display mode. #19326
• [BUGFIX] discovery/aws: Avoid a panic when an ElastiCache ARN is missing its resource ID. #19333
• [BUGFIX] discovery/aws: Do not panic on MSK clusters whose optional API fields are absent. #19584
• [BUGFIX] discovery/aws: Do not panic when the EC2 API omits optional instance fields. #19512
• [BUGFIX] discovery/aws: Don't panic on ECS tasks with absent optional fields. #19396
• [BUGFIX] discovery/aws: MSK Optional Custom Configuration Fields #19422. #19422
• [BUGFIX] discovery/ionos: Fix panic when the IONOS API omits optional server fields. #19418
• [BUGFIX] discovery/kubernetes: Populate __meta_kubernetes_service_loadbalancer_ip from status.loadBalancer.ingress, falling back to deprecated spec.loadBalancerIP. #19404
• [BUGFIX] histogram: Fix Compact moving buckets to wrong indices, and producing negative bucket counts for integer histograms, when more than one span is merged in the same pass. #19312
• [BUGFIX] promtool: Fixed tsdb dump silently dropping native histogram samples. #18051
• [BUGFIX] scrape: fix data race in Manager.TargetsDroppedCounts to avoid miscounting dropped targets. #19304
• [BUGFIX] scrape: fix nil histogram when native and classic histograms are mixed in one metric family. #19452
• [BUGFIX] TSDB: Fix WAL and GC log messages to emit human-readable duration strings instead of nanosecond integers. #19307

• [SECURITY] Bump github.com/klauspost/compress to v1.18.7 (GO-2026-5841) and golang.org/x/crypto to v0.55.0 (GO-2026-6303).
• [BUGFIX] Docker SD: Fix panic in Docker Swarm service discovery when a service runs as a plugin or network-attachment. #19102
• [BUGFIX] PromQL: Fix case-insensitive regex label matchers silently dropping matching values. #19167
• [BUGFIX] Scrape: Fix scrape manager spinning at 100% CPU on shutdown. #19149
• [BUGFIX] Alerting: Fix 100% CPU usage on shutdown that could delay graceful shutdown and trigger timeout-based kills. #17859
• [BUGFIX] TSDB: Fix out-of-order queries blocking compaction for hours, causing memory usage to grow. #19013
• [BUGFIX] TSDB: Fix deleted series causing missing samples and errors after restart. #19140
• [BUGFIX] TSDB: Fix goroutine and file handle leaks when Prometheus fails to open a corrupt TSDB. On Windows, the leaked directory handle also prevented TSDB directory removal. #18291

• [CHANGE] API: Deprecate the stats query parameter of /api/v1/query and /api/v1/query_range for values other than true and all. Other values still enable basic statistics but now return a deprecation warning; they will be rejected in the next major release. #19124
• [CHANGE] API: /api/v1/status/config now correctly shows separator: "" and replacement: "" in relabel configs when explicitly set to empty, instead of omitting them. #18653
• [CHANGE] Discovery/Hetzner: Drop the __meta_hetzner_datacenter label for hcloud targets, following its removal from the Hetzner Cloud API. #19269
• [CHANGE] PromQL: Enable duration expressions by default. The promql-duration-expr feature flag is now a no-op. #19033
• [CHANGE] PromQL: Promote first_over_time to stable. It no longer requires the promql-experimental-functions feature flag. #19093
• [FEATURE] Discovery: Add Oracle Cloud Infrastructure compute service discovery (oci_sd_configs). #18919
• [FEATURE] PromQL: Add experimental start_timestamp(instant-vector) function returning the start timestamp of each sample in the given vector. Requires the use-start-timestamps feature flag. #19089
• [FEATURE] PromQL: Allow rate() and increase() to use start timestamps as an alternative for rate extrapolation. Hidden behind the use-start-timestamps feature flag. #18619
• [FEATURE] TSDB: Add experimental support for encoding start timestamps in histograms and float histograms. Hidden behind the histograms-st-encoding feature flag. #18609
• [ENHANCEMENT] OTLP: Emit a warning when OTLP attribute names collide into the same Prometheus label after sanitization (e.g. k8s.pod.name and k8s_pod_name both become k8s_pod_name), and expose the prometheus_api_otlp_translation_warnings_total counter labelled by category to track such warnings. #18957
• [ENHANCEMENT] Promtool: Add --remote-write.path flag to push metrics for backends that use a non-default remote-write endpoint. #19086
• [ENHANCEMENT] Remote write: Forward histogram start timestamps in the remote write V2 protocol. #18903
• [ENHANCEMENT] TSDB: Add prometheus_tsdb_head_native_histogram_series and prometheus_tsdb_head_native_histogram_buckets gauges tracking the number of native histogram series and buckets in the head. #19170
• [ENHANCEMENT] UI: Add syntax highlighting, autocompletion, and linting for PromQL duration expressions (step(), range(), min_of(), max_of()) in range selectors and subqueries. #18625
• [ENHANCEMENT] UI: Add copy button next to rule names on the Rules and Alerts pages. #18706
• [ENHANCEMENT] UI: Improve rule group title contrast on the Rules page. #19181
• [PERF] Speed up regex label matchers matching a set of literal values (e.g. {job=~"foo|bar|baz"}). #18833
• [PERF] Remote read: Improve remote read throughput by removing unnecessary per-write flushing. #18470
• [PERF] Scrape: Parse text and OpenMetrics formats without recursion, preventing stack overflow from deeply nested or malicious exposition input. #19143
• [PERF] Scrape: Reduce native histogram scrape parsing allocations by ~49%. #19282
• [PERF] TSDB: Speed up queries on series with many in-memory chunks. #18300
• [BUGFIX] Alerting: Fix 100% CPU usage on shutdown that could delay graceful shutdown and trigger timeout-based kills. #17859
• [BUGFIX] Discovery/AWS: Stop promtool check config from making AWS metadata service (IMDS) network calls when the region field is omitted in EC2, ECS, RDS, MSK, ElastiCache, and Lightsail service discovery configs. #19037
• [BUGFIX] Discovery/Docker: Set a request timeout for docker_sd and dockerswarm_sd on unix, npipe, and tcp hosts. Previously an unresponsive daemon could freeze discovery indefinitely, silently pinning targets to a stale snapshot. #19237
• [BUGFIX] Discovery/Docker: Fix panic in Docker Swarm service discovery when a service runs as a plugin or network-attachment. #19102
• [BUGFIX] Discovery/Docker: Fix discovery of IPv6-only containers. #18778
• [BUGFIX] PromQL: Fix case-insensitive regex label matchers silently dropping matching values. #19167
• [BUGFIX] PromQL: Fix mad_over_time returning 0 instead of NaN when the range contains a NaN sample. #19040
• [BUGFIX] Promtool: Accept --enable-feature=promql-binop-fill-modifiers in check rules, which previously rejected valid fill()/fill_left()/fill_right() expressions. #19153
• [BUGFIX] Remote write: Respect the AZURE_FEDERATED_TOKEN_FILE environment variable for workload identity authentication instead of hardcoding the token file path. #18973
• [BUGFIX] Rules: Clean up stale rule_group_last_rule_duration_sum_seconds and rule_group_last_restore_duration_seconds series when a rule group is removed or renamed on reload. Previously each reload leaked two series per dropped group, growing /metrics cardinality over time. #19107
• [BUGFIX] Scrape: Fix scrape manager spinning at 100% CPU on shutdown. #19149
• [BUGFIX] TSDB: Fix silent data loss and potential crash loop when stale_series_compaction_threshold is used in the config file. #19016
• [BUGFIX] TSDB: Fix potential data loss on restart when out-of-order ingestion is enabled and blocks are compacted. #19016
• [BUGFIX] TSDB: Fix prometheus_tsdb_head_stale_series over-counting and early eviction of series that change between float, integer histogram, and float histogram sample types. #19183
• [BUGFIX] TSDB: Fix goroutine and file handle leaks when Prometheus fails to open a corrupt TSDB. On Windows, the leaked directory handle also prevented TSDB directory removal. #18291
• [BUGFIX] TSDB: Fix out-of-order queries blocking compaction for hours, causing memory usage to grow. #19013
• [BUGFIX] TSDB: Fix deleted series causing missing samples and errors after restart. #19140
• [BUGFIX] TSDB: Fix native histogram data becoming incorrect after restart. #19202
• [BUGFIX] TSDB: Surface query errors that were previously silently discarded. #19120
• [BUGFIX] TSDB: Honour the configured float chunk encoding when compaction rewrites chunks; previously chunks encoded with --enable-feature=xor2-encoding could silently revert to XOR after compaction. #19145
• [BUGFIX] UI: Show the delete-series form on the TSDB Status page when --web.enable-admin-api is enabled. #19025

• [CHANGE] API: Deprecate the stats query parameter of /api/v1/query and /api/v1/query_range for values other than true and all. Other values still enable basic statistics but now return a deprecation warning; they will be rejected in the next major release. #19124
• [CHANGE] API: /api/v1/status/config now correctly shows separator: "" and replacement: "" in relabel configs when explicitly set to empty, instead of omitting them. #18653
• [CHANGE] Discovery/Hetzner: Drop the __meta_hetzner_datacenter label for hcloud targets, following its removal from the Hetzner Cloud API. #19269
• [CHANGE] PromQL: Enable duration expressions by default. The promql-duration-expr feature flag is now a no-op. #19033
• [CHANGE] PromQL: Promote first_over_time to stable. It no longer requires the promql-experimental-functions feature flag. #19093
• [FEATURE] Discovery: Add Oracle Cloud Infrastructure compute service discovery (oci_sd_configs). #18919
• [FEATURE] PromQL: Add experimental start_timestamp(instant-vector) function returning the start timestamp of each sample in the given vector. Requires the use-start-timestamps feature flag. #19089
• [FEATURE] PromQL: Allow rate() and increase() to use start timestamps as an alternative for rate extrapolation. Hidden behind the use-start-timestamps feature flag. #18619
• [FEATURE] TSDB: Add experimental support for encoding start timestamps in histograms and float histograms. Hidden behind the histograms-st-encoding feature flag. #18609
• [ENHANCEMENT] OTLP: Emit a warning when OTLP attribute names collide into the same Prometheus label after sanitization (e.g. k8s.pod.name and k8s_pod_name both become k8s_pod_name), and expose the prometheus_api_otlp_translation_warnings_total counter labelled by category to track such warnings. #18957
• [ENHANCEMENT] Promtool: Add --remote-write.path flag to push metrics for backends that use a non-default remote-write endpoint. #19086
• [ENHANCEMENT] Remote write: Forward histogram start timestamps in the remote write V2 protocol. #18903
• [ENHANCEMENT] TSDB: Add prometheus_tsdb_head_native_histogram_series and prometheus_tsdb_head_native_histogram_buckets gauges tracking the number of native histogram series and buckets in the head. #19170
• [ENHANCEMENT] UI: Add syntax highlighting, autocompletion, and linting for PromQL duration expressions (step(), range(), min_of(), max_of()) in range selectors and subqueries. #18625
• [ENHANCEMENT] UI: Add copy button next to rule names on the Rules and Alerts pages. #18706
• [ENHANCEMENT] UI: Improve rule group title contrast on the Rules page. #19181
• [PERF] Speed up regex label matchers matching a set of literal values (e.g. {job=~"foo|bar|baz"}). #18833
• [PERF] Remote read: Improve remote read throughput by removing unnecessary per-write flushing. #18470
• [PERF] Scrape: Parse text and OpenMetrics formats without recursion, preventing stack overflow from deeply nested or malicious exposition input. #19143
• [PERF] Scrape: Reduce native histogram scrape parsing allocations by ~49%. #19282
• [PERF] TSDB: Speed up queries on series with many in-memory chunks. #18300
• [BUGFIX] Alerting: Fix 100% CPU usage on shutdown that could delay graceful shutdown and trigger timeout-based kills. #17859
• [BUGFIX] Discovery/AWS: Stop promtool check config from making AWS metadata service (IMDS) network calls when the region field is omitted in EC2, ECS, RDS, MSK, ElastiCache, and Lightsail service discovery configs. #19037
• [BUGFIX] Discovery/Docker: Set a request timeout for docker_sd and dockerswarm_sd on unix, npipe, and tcp hosts. Previously an unresponsive daemon could freeze discovery indefinitely, silently pinning targets to a stale snapshot. #19237
• [BUGFIX] Discovery/Docker: Fix panic in Docker Swarm service discovery when a service runs as a plugin or network-attachment. #19102
• [BUGFIX] Discovery/Docker: Fix discovery of IPv6-only containers. #18778
• [BUGFIX] PromQL: Fix case-insensitive regex label matchers silently dropping matching values. #19167
• [BUGFIX] PromQL: Fix mad_over_time returning 0 instead of NaN when the range contains a NaN sample. #19040
• [BUGFIX] Promtool: Accept --enable-feature=promql-binop-fill-modifiers in check rules, which previously rejected valid fill()/fill_left()/fill_right() expressions. #19153
• [BUGFIX] Remote write: Respect the AZURE_FEDERATED_TOKEN_FILE environment variable for workload identity authentication instead of hardcoding the token file path. #18973
• [BUGFIX] Rules: Clean up stale rule_group_last_rule_duration_sum_seconds and rule_group_last_restore_duration_seconds series when a rule group is removed or renamed on reload. Previously each reload leaked two series per dropped group, growing /metrics cardinality over time. #19107
• [BUGFIX] Scrape: Fix scrape manager spinning at 100% CPU on shutdown. #19149
• [BUGFIX] TSDB: Fix silent data loss and potential crash loop when stale_series_compaction_threshold is used in the config file. #19016
• [BUGFIX] TSDB: Fix potential data loss on restart when out-of-order ingestion is enabled and blocks are compacted. #19016
• [BUGFIX] TSDB: Fix prometheus_tsdb_head_stale_series over-counting and early eviction of series that change between float, integer histogram, and float histogram sample types. #19183
• [BUGFIX] TSDB: Fix goroutine and file handle leaks when Prometheus fails to open a corrupt TSDB. On Windows, the leaked directory handle also prevented TSDB directory removal. #18291
• [BUGFIX] TSDB: Fix out-of-order queries blocking compaction for hours, causing memory usage to grow. #19013
• [BUGFIX] TSDB: Fix deleted series causing missing samples and errors after restart. #19140
• [BUGFIX] TSDB: Fix native histogram data becoming incorrect after restart. #19202
• [BUGFIX] TSDB: Surface query errors that were previously silently discarded. #19120
• [BUGFIX] TSDB: Honour the configured float chunk encoding when compaction rewrites chunks; previously chunks encoded with --enable-feature=xor2-encoding could silently revert to XOR after compaction. #19145
• [BUGFIX] UI: Show the delete-series form on the TSDB Status page when --web.enable-admin-api is enabled. #19025

What's Changed

• [SECURITY] Bump golang.org/x/text to v0.39.0 (CVE-2026-56852) and google.golang.org/grpc to v1.82.1 (GHSA-hrxh-6v49-42gf). #19290 by @krajorama
• [BUGFIX] PromQL: Preallocate the active query tracker file to avoid SIGBUS crashes when the data disk is full. #19289 by @akshajrawat

Full Changelog: https://github.com/prometheus/prometheus/compare/v3.13.1...v3.13.2

This is a bugfix release for 3.13 LTS.

• [BUGFIX] TSDB: Fix the head-chunk cache returning samples from the wrong chunk, or spurious not-found errors, to range queries after head-chunk truncation. #19134

This release is built with Go 1.25.12 and fixes a security issue in a UI dependency.

• [SECURITY] UI: Bump sanitize-html to v2.17.5 to fix CVE-2026-53606. #19060

• [SECURITY] UI: Bump sanitize-html to fix a cross-site scripting vulnerability (CVE-2026-44990). #18697
• [CHANGE] API: Use SHA-256 instead of SHA-1 to generate rule group pagination tokens. #18927
• [CHANGE] HTTP clients: Credentials (Authorization header, basic auth, bearer token, OAuth2, configured headers) are no longer forwarded when following a redirect to a different host; affects scraping, remote read/write, alerting, and service discovery. Via prometheus/common v0.69.0 (CVE-2025-4673 CVE-2023-45289). #18949
• [CHANGE] promtool: Relative file paths in the file passed to --http.config.file are now resolved relative to that config file's directory instead of its parent directory. Via prometheus/common v0.69.0. #18949
• [CHANGE] PromQL: Rename the min() and max() duration-expression functions (experimental feature flag experimental-duration-expr) to min_of() and max_of() to avoid confusion with the min and max aggregate operators. #18687
• [FEATURE] API: Add experimental search endpoints to search metric names, label names, and label values. #18573
• [FEATURE] Discovery/AWS: Add ability to filter RDS instances. #18859
• [FEATURE] PromQL: Add min_of(a, b) and max_of(a, b) scalar experimental functions, returning the smaller or larger of two scalar values. #18687
• [FEATURE] PromQL: Add support for smoothed/anchored rate with native histograms. #18564
• [FEATURE] PromQL: Expose per-query samplesRead (and samplesReadPerStep with stats=all and the promql-per-step-stats feature flag) in the query stats response, and add the prometheus_engine_query_samples_read_total engine counter. samplesRead reflects storage I/O distinct from totalQueryableSamples, which counts samples loaded into the evaluator (and so over-counts when a sample is reused across multiple range-vector windows). #18081
• [FEATURE] Scrape: Add __convert_classic_histograms_to_nhcb__ internal label to allow per-target override of convert_classic_histograms_to_nhcb scrape configuration via relabeling. #18840
• [FEATURE] TSDB: Add storage.tsdb.chunk_encoding.floats configuration field to select float chunk encoding (xor or xor2) at runtime, independently of the --enable-feature=xor2-encoding flag. #18769
• [FEATURE] remote_write: Add Certificate support for ingesting data into an Azure Monitor Workspace. #18217
• [FEATURE] Scrape: Add __always_scrape_classic_histograms__ and __scrape_native_histograms__ internal labels to allow per-target override of the always_scrape_classic_histograms and scrape_native_histograms scrape configuration via relabeling. #18929
• [ENHANCEMENT] Release: Container images are now also published to the GitHub Container Registry (ghcr.io). #18791
• [ENHANCEMENT] PromQL: Prettify fill_left(x) fill_right(x) as fill(x) when both fill values are equal. #18851
• [ENHANCEMENT] UI: Improve autocompletion after closing a function bracket. #18894
• [PERF] Labels: Add case-insensitive prefix matching to speed up evaluation of long case-insensitive regular expressions (up to ~2x faster). #18540
• [PERF] TSDB: Reduce per-sample overhead in chunk population, speeding up affected queries by ~12-15% in benchmarks. #18699
• [PERF] TSDB: Eliminate unnecessary heap allocations in the V2 histogram WAL decoder, reducing allocations by up to 50% and memory by up to 10% for deployments using native histograms with created-timestamp storage enabled (--enable-feature=created-timestamp-zero-ingestion). #18813
• [BUGFIX] Discovery/AWS: Fix failure when processing an AWS RDS cluster without instances. #18845
• [BUGFIX] Fix race condition in initTime that could cause ErrOutOfBounds. #18629
• [BUGFIX] PromQL: A range query whose end was not aligned to step caused subqueries inside it to evaluate past the parent's last actual step, inflating peakSamples in the query stats and against the query.max-samples limit, and wasting storage I/O reading samples that were never used in the result. #18081
• [BUGFIX] PromQL: A range query containing an at-modifier-unsafe function over a range-vector with an @ modifier (e.g. predict_linear(metric[60s] @ T, X)) silently under-counted totalQueryableSamples for steps after step 0. #18081
• [BUGFIX] PromQL: Fix fill_left/fill_right producing missing samples in range queries when using group_left/group_right. #18850
• [BUGFIX] PromQL: Fix for resets() and changes() in anchored range extenders with histograms. #18906
• [BUGFIX] PromQL: Fix panic on 1[5m] smoothed and similar expressions when extended range selectors are enabled. #18764
• [BUGFIX] PromQL: Fix panic when a smoothed instant vector selector produces no samples for a series. #18943
• [BUGFIX] PromQL: Fix panic when using a parenthesised plain number as an offset (e.g. foo offset -(5)). #18768
• [BUGFIX] promtool: Fix panic when parsing exposition text containing empty braces {}. Via prometheus/common v0.69.0. #18949
• [BUGFIX] Promtool: Fix check healthy and check ready when --url ends with a trailing slash. #18854
• [BUGFIX] Rules: Close PromQL query after each rule evaluation to ensure resources are released. #18733
• [BUGFIX] Scaleway SD: Resolve VPC/IPAM-only instances that have no legacy private_ip or public_ip field, but do have private NICs attached. #18772
• [BUGFIX] TSDB: Do not leak head series when an integer histogram append is rejected (e.g. out-of-order). #18838
• [BUGFIX] UI: Escape label values offered by PromQL autocomplete. #18658
• [BUGFIX] TSDB: Fix chunk snapshot encoding for EncXOR2 chunks, preventing corruption on TSDB restart when EncXOR2-encoded series were present. #18739
• [BUGFIX] TSDB: Store a millisecond timestamp (not a WAL segment number) in walExpiries when a series is evicted via CompactStaleHead/CompactSelectedSeries, so the series's label record is correctly retained in the next WAL checkpoint and replays cleanly. #18847
• [BUGFIX] TSDB: Prevent loss of samples at the chunk-range boundary when CompactSelectedSeries (and CompactStaleHead) evict the series — the per-slice compaction loop now runs one more iteration so the boundary timestamp is captured in a block before the in-memory copy is removed. #18849

This is a Long Term Support LTS release.

• [SECURITY] UI: Bump sanitize-html to fix a cross-site scripting vulnerability (CVE-2026-44990). #18697
• [CHANGE] UI: Third-party npm dependency licenses are now embedded in the Prometheus binary and served at /assets/third-party-licenses.txt, replacing the npm_licenses.tar.bz2 archive previously shipped in release tarballs and container images. #18997
• [CHANGE] API: Use SHA-256 instead of SHA-1 to generate rule group pagination tokens. #18927
• [CHANGE] HTTP clients: Credentials (Authorization header, basic auth, bearer token, OAuth2, configured headers) are no longer forwarded when following a redirect to a different host; affects scraping, remote read/write, alerting, and service discovery. Via prometheus/common v0.69.0 (CVE-2025-4673 CVE-2023-45289). #18949
• [CHANGE] promtool: Relative file paths in the file passed to --http.config.file are now resolved relative to that config file's directory instead of its parent directory. Via prometheus/common v0.69.0. #18949
• [CHANGE] PromQL: Rename the min() and max() duration-expression functions (experimental feature flag experimental-duration-expr) to min_of() and max_of() to avoid confusion with the min and max aggregate operators. #18687
• [FEATURE] API: Add experimental search endpoints to search metric names, label names, and label values. #18573
• [FEATURE] Discovery/AWS: Add ability to filter RDS instances. #18859
• [FEATURE] PromQL: Add min_of(a, b) and max_of(a, b) scalar experimental functions, returning the smaller or larger of two scalar values. #18687
• [FEATURE] PromQL: Add support for smoothed/anchored rate with native histograms. #18564
• [FEATURE] PromQL: Expose per-query samplesRead (and samplesReadPerStep with stats=all and the promql-per-step-stats feature flag) in the query stats response, and add the prometheus_engine_query_samples_read_total engine counter. samplesRead reflects storage I/O distinct from totalQueryableSamples, which counts samples loaded into the evaluator (and so over-counts when a sample is reused across multiple range-vector windows). #18081
• [FEATURE] Scrape: Add __convert_classic_histograms_to_nhcb__ internal label to allow per-target override of convert_classic_histograms_to_nhcb scrape configuration via relabeling. #18840
• [FEATURE] TSDB: Add storage.tsdb.chunk_encoding.floats configuration field to select float chunk encoding (xor or xor2) at runtime, independently of the --enable-feature=xor2-encoding flag. #18769
• [FEATURE] remote_write: Add Certificate support for ingesting data into an Azure Monitor Workspace. #18217
• [FEATURE] Scrape: Add __always_scrape_classic_histograms__ and __scrape_native_histograms__ internal labels to allow per-target override of the always_scrape_classic_histograms and scrape_native_histograms scrape configuration via relabeling. #18929
• [ENHANCEMENT] Release: Container images are now also published to the GitHub Container Registry (ghcr.io). #18791
• [ENHANCEMENT] PromQL: Prettify fill_left(x) fill_right(x) as fill(x) when both fill values are equal. #18851
• [ENHANCEMENT] UI: Improve autocompletion after closing a function bracket. #18894
• [PERF] Labels: Add case-insensitive prefix matching to speed up evaluation of long case-insensitive regular expressions (up to ~2x faster). #18540
• [PERF] TSDB: Reduce per-sample overhead in chunk population, speeding up affected queries by ~12-15% in benchmarks. #18699
• [PERF] TSDB: Eliminate unnecessary heap allocations in the V2 histogram WAL decoder, reducing allocations by up to 50% and memory by up to 10% for deployments using native histograms with created-timestamp storage enabled (--enable-feature=created-timestamp-zero-ingestion). #18813
• [BUGFIX] Discovery/AWS: Fix failure when processing an AWS RDS cluster without instances. #18845
• [BUGFIX] Fix race condition in initTime that could cause ErrOutOfBounds. #18629
• [BUGFIX] PromQL: A range query whose end was not aligned to step caused subqueries inside it to evaluate past the parent's last actual step, inflating peakSamples in the query stats and against the query.max-samples limit, and wasting storage I/O reading samples that were never used in the result. #18081
• [BUGFIX] PromQL: A range query containing an at-modifier-unsafe function over a range-vector with an @ modifier (e.g. predict_linear(metric[60s] @ T, X)) silently under-counted totalQueryableSamples for steps after step 0. #18081
• [BUGFIX] PromQL: Fix fill_left/fill_right producing missing samples in range queries when using group_left/group_right. #18850
• [BUGFIX] PromQL: Fix for resets() and changes() in anchored range extenders with histograms. #18906
• [BUGFIX] PromQL: Fix panic on 1[5m] smoothed and similar expressions when extended range selectors are enabled. #18764
• [BUGFIX] PromQL: Fix panic when a smoothed instant vector selector produces no samples for a series. #18943
• [BUGFIX] PromQL: Fix panic when using a parenthesised plain number as an offset (e.g. foo offset -(5)). #18768
• [BUGFIX] promtool: Fix panic when parsing exposition text containing empty braces {}. Via prometheus/common v0.69.0. #18949
• [BUGFIX] Promtool: Fix check healthy and check ready when --url ends with a trailing slash. #18854
• [BUGFIX] Rules: Close PromQL query after each rule evaluation to ensure resources are released. #18733
• [BUGFIX] Scaleway SD: Resolve VPC/IPAM-only instances that have no legacy private_ip or public_ip field, but do have private NICs attached. #18772
• [BUGFIX] TSDB: Do not leak head series when an integer histogram append is rejected (e.g. out-of-order). #18838
• [BUGFIX] UI: Escape label values offered by PromQL autocomplete. #18658
• [BUGFIX] TSDB: Fix chunk snapshot encoding for EncXOR2 chunks, preventing corruption on TSDB restart when EncXOR2-encoded series were present. #18739
• [BUGFIX] TSDB: Store a millisecond timestamp (not a WAL segment number) in walExpiries when a series is evicted via CompactStaleHead/CompactSelectedSeries, so the series's label record is correctly retained in the next WAL checkpoint and replays cleanly. #18847
• [BUGFIX] TSDB: Prevent loss of samples at the chunk-range boundary when CompactSelectedSeries (and CompactStaleHead) evict the series — the per-slice compaction loop now runs one more iteration so the boundary timestamp is captured in a block before the in-memory copy is removed. #18849

Release notes of the 3.13-rc.1 release:

The 3.13.0-rc.0 release was only partially successful due to the migration from NPM to PNPM and subsequent CI issues, so most of the changes in this release candidate are CI/build-related. The only user-facing change is:

• [CHANGE] UI: Third-party npm dependency licenses are now embedded in the Prometheus binary and served at /assets/third-party-licenses.txt, replacing the npm_licenses.tar.bz2 archive previously shipped in release tarballs and container images. #18997

Release notes of the 3.13-rc.0 release, as it was not published in partial state:

• [SECURITY] UI: Bump sanitize-html to fix a cross-site scripting vulnerability (CVE-2026-44990). #18697
• [CHANGE] API: Use SHA-256 instead of SHA-1 to generate rule group pagination tokens. #18927
• [CHANGE] HTTP clients: Credentials (Authorization header, basic auth, bearer token, OAuth2, configured headers) are no longer forwarded when following a redirect to a different host; affects scraping, remote read/write, alerting, and service discovery. Via prometheus/common v0.69.0 (CVE-2025-4673 CVE-2023-45289). #18949
• [CHANGE] promtool: Relative file paths in the file passed to --http.config.file are now resolved relative to that config file's directory instead of its parent directory. Via prometheus/common v0.69.0. #18949
• [CHANGE] PromQL: Rename the min() and max() duration-expression functions (experimental feature flag experimental-duration-expr) to min_of() and max_of() to avoid confusion with the min and max aggregate operators. #18687
• [FEATURE] API: Add experimental search endpoints to search metric names, label names, and label values. #18573
• [FEATURE] Discovery/AWS: Add ability to filter RDS instances. #18859
• [FEATURE] PromQL: Add min_of(a, b) and max_of(a, b) scalar experimental functions, returning the smaller or larger of two scalar values. #18687
• [FEATURE] PromQL: Add support for smoothed/anchored rate with native histograms. #18564
• [FEATURE] PromQL: Expose per-query samplesRead (and samplesReadPerStep with stats=all and the promql-per-step-stats feature flag) in the query stats response, and add the prometheus_engine_query_samples_read_total engine counter. samplesRead reflects storage I/O distinct from totalQueryableSamples, which counts samples loaded into the evaluator (and so over-counts when a sample is reused across multiple range-vector windows). #18081
• [FEATURE] Scrape: Add __convert_classic_histograms_to_nhcb__ internal label to allow per-target override of convert_classic_histograms_to_nhcb scrape configuration via relabeling. #18840
• [FEATURE] TSDB: Add storage.tsdb.chunk_encoding.floats configuration field to select float chunk encoding (xor or xor2) at runtime, independently of the --enable-feature=xor2-encoding flag. #18769
• [FEATURE] remote_write: Add Certificate support for ingesting data into an Azure Monitor Workspace. #18217
• [FEATURE] Scrape: Add __always_scrape_classic_histograms__ and __scrape_native_histograms__ internal labels to allow per-target override of the always_scrape_classic_histograms and scrape_native_histograms scrape configuration via relabeling. #18929
• [ENHANCEMENT] Release: Container images are now also published to the GitHub Container Registry (ghcr.io). #18791
• [ENHANCEMENT] PromQL: Prettify fill_left(x) fill_right(x) as fill(x) when both fill values are equal. #18851
• [ENHANCEMENT] UI: Improve autocompletion after closing a function bracket. #18894
• [PERF] Labels: Add case-insensitive prefix matching to speed up evaluation of long case-insensitive regular expressions (up to ~2x faster). #18540
• [PERF] TSDB: Reduce per-sample overhead in chunk population, speeding up affected queries by ~12-15% in benchmarks. #18699
• [PERF] TSDB: Eliminate unnecessary heap allocations in the V2 histogram WAL decoder, reducing allocations by up to 50% and memory by up to 10% for deployments using native histograms with created-timestamp storage enabled (--enable-feature=created-timestamp-zero-ingestion). #18813
• [BUGFIX] Discovery/AWS: Fix failure when processing an AWS RDS cluster without instances. #18845
• [BUGFIX] Fix race condition in initTime that could cause ErrOutOfBounds. #18629
• [BUGFIX] PromQL: A range query whose end was not aligned to step caused subqueries inside it to evaluate past the parent's last actual step, inflating peakSamples in the query stats and against the query.max-samples limit, and wasting storage I/O reading samples that were never used in the result. #18081
• [BUGFIX] PromQL: A range query containing an at-modifier-unsafe function over a range-vector with an @ modifier (e.g. predict_linear(metric[60s] @ T, X)) silently under-counted totalQueryableSamples for steps after step 0. #18081
• [BUGFIX] PromQL: Fix fill_left/fill_right producing missing samples in range queries when using group_left/group_right. #18850
• [BUGFIX] PromQL: Fix for resets() and changes() in anchored range extenders with histograms. #18906
• [BUGFIX] PromQL: Fix panic on 1[5m] smoothed and similar expressions when extended range selectors are enabled. #18764
• [BUGFIX] PromQL: Fix panic when a smoothed instant vector selector produces no samples for a series. #18943
• [BUGFIX] PromQL: Fix panic when using a parenthesised plain number as an offset (e.g. foo offset -(5)). #18768
• [BUGFIX] promtool: Fix panic when parsing exposition text containing empty braces {}. Via prometheus/common v0.69.0. #18949
• [BUGFIX] Promtool: Fix check healthy and check ready when --url ends with a trailing slash. #18854
• [BUGFIX] Rules: Close PromQL query after each rule evaluation to ensure resources are released. #18733
• [BUGFIX] Scaleway SD: Resolve VPC/IPAM-only instances that have no legacy private_ip or public_ip field, but do have private NICs attached. #18772
• [BUGFIX] TSDB: Do not leak head series when an integer histogram append is rejected (e.g. out-of-order). #18838
• [BUGFIX] UI: Escape label values offered by PromQL autocomplete. #18658
• [BUGFIX] TSDB: Fix chunk snapshot encoding for EncXOR2 chunks, preventing corruption on TSDB restart when EncXOR2-encoded series were present. #18739
• [BUGFIX] TSDB: Store a millisecond timestamp (not a WAL segment number) in walExpiries when a series is evicted via CompactStaleHead/CompactSelectedSeries, so the series's label record is correctly retained in the next WAL checkpoint and replays cleanly. #18847
• [BUGFIX] TSDB: Prevent loss of samples at the chunk-range boundary when CompactSelectedSeries (and CompactStaleHead) evict the series — the per-slice compaction loop now runs one more iteration so the boundary timestamp is captured in a block before the in-memory copy is removed. #18849

This release fixes multiple security issues.

• [SECURITY] STACKIT SD: Fix secrets being exposed in plaintext via /-/config endpoint. Thanks to @August829 and @Phaxma for reporting. GHSA-39j6-789q-qxvh #18650
• [SECURITY] Dependencies: Bump golang.org/x/net to v0.55.0 and OpenTelemetry to v1.43.0 to fix reported CVEs (GO-2026-5026, GO-2026-4918, GO-2026-4985). #18934
• [SECURITY] UI: Bump mantine-ui dependencies (react-router-dom, vitest, vite, postcss) to their patched versions to resolve security advisories. #18935
• [ENHANCEMENT] Release: Container images are now also published to the GitHub Container Registry (ghcr.io). #18792

This release contains security fixes, new features (especially around PromQL and Service Discovery), performance improvements in TSDB, Start Timestamp improvements and numerous bug fixes.

Thanks to all contributors!

Key Highlights

• Security: Two security vulnerabilities have been addressed: a denial of service in remote-write (snappy decompression limit) and a secret exposure leak in STACKIT service discovery.
• PromQL & Metadata: Several features and bug fixes related to the experimental "start timestamps" support, including updates to rate(), irate(), increase(), and resets(). New experimental functions start(), end(), range(), and step() are introduced.
• TSDB Performance: Optimizations in head chunk lookup (constant time) and mmap operations to reduce CPU usage.
• Service Discovery: Added support for DigitalOcean Managed Databases and Outscale VM, along with improvements to AWS SD (IPv6 support for EC2, external ID support).
• UI: Added a web interface for deleting time series and cleaning tombstones.

Changelog

• [SECURITY] Remote: Reject snappy-compressed received requests via Remote Write whose declared decoded length exceeds the 32MB. Thanks to @hibrian827 for reporting it. #18642
• [SECURITY] STACKIT SD: Fix secrets being exposed in plaintext via /-/config endpoint. Thanks to @August829 and @Phaxma for reporting. GHSA-39j6-789q-qxvh #18649
• [CHANGE] TSDB/Agent: Adds Start Timestamp field to all WAL Histogram samples in memory; used st-storage flag is enabled. #18221
• [FEATURE] API: Add /api/v1/status/self_metrics endpoint returning the current state of the Prometheus server's own metrics about itself as JSON. #18411
• [FEATURE] Discovery: Add DigitalOcean Managed Databases service discovery #18287
• [FEATURE] Prometheus: Add support for the aix/ppc64 compilation target #18321
• [FEATURE] Discovery: Add Outscale VM service discovery (outscale_sd_configs) for discovering scrape targets from the Outscale Cloud API. #18139
• [FEATURE] PromQL: Emit a warning when sort, sort_by_label or sort_by_label_desc is used within range (matrix) queries, as these functions do not have effect in that context. #18498
• [FEATURE] PromQL: Add start(), end(), range(), and step() experimental functions #17877
• [FEATURE] PromQL: Update resets() function to consider start timestamp resets. Hidden behind use-start-timestamps feature flag. #18627
• [FEATURE] Prometheus: Promote auto-reload-config as stable #18620
• [FEATURE] TSDB/Agent: Add CheckpointFromInMemorySeries option to agent.DB that enables checkpoint based on in-memory series. #17948
• [FEATURE] UI: Add a web interface for deleting time series and cleaning tombstones, accessible from the Status menu. #18390
• [FEATURE] PromQL: Use start timestamps for rate(), irate(), and increase() calculations, behind a feature flag use-start-timestamps. Doesn't work together with extended range selectors anchored and smoothed. #18344
• [FEATURE] Scrape: Added a feature flag st-synthesis which synthesizes unknown STs for scraped cumulative metrics. Useful when Remote Writing 2.0 with delta or Otel-based backends. #18279
• [FEATURE] promqltest: support @st annotation in load blocks to specify per-sample start timestamps. #18360
• [ENHANCEMENT] API: reject concurrent fgprof profiles. #18651
• [ENHANCEMENT] AWS SD: Add optional external_id field to ECS/MSK/RDS/Elasticache. #18579
• [ENHANCEMENT] AWS SD: Add optional external_id field. #17171
• [ENHANCEMENT] Discovery: Propagate SD target updates faster by introducing dynamic backoff interval instead of static 5s interval for throttling. #18187
• [ENHANCEMENT] Promtool: Add --header flag to query instant command, matching existing query range behaviour. #18418
• [ENHANCEMENT]: AWS SD: Allows EC2 service discovery to discover IPv6 addresses to communicate with target endpoints. The private IPv4 address remains the default when both IPv4 and IPv6 addresses are present. #16088
• [PERF] TSDB: Make head chunk lookup in range queries constant time instead of quadratic time #18302
• [PERF] TSDB: Skip entire stripes in mmapHeadChunks when no series need mmapping, reducing CPU utilization significantly at production-relevant scales. #18541
• [PERF] TSDB: Skip clean series during periodic head chunk mmap using cached head chunk count #18272
• [PERF] PromQL: Address FloatHistogram.KahanAdd performance regression on Go 1.26. #18568
• [BUGFIX] PromQL: Fix info() function incorrectly handling negated __name__ matchers #17932
• [BUGFIX] API: Return duration expressions in /parse_ast. #18624
• [BUGFIX] API: correctly document formats accepted for duration query request parameters (step, timeout and lookback delta) in OpenAPI spec #18305
• [BUGFIX] Scrape: AppenderV2 now tracks staleness even when OOO/duplicate series errors happen similar to AppenderV1 #18567
• [BUGFIX] Config: Validate remote_write queue_config fields at load time to prevent runtime panic and silent misconfiguration. #18209
• [BUGFIX] Discovery/Consul: Add health_filter for Health API filtering, fixing breakage when using Catalog-only fields like ServiceTags in filter. #18479 #18499
• [BUGFIX] OTLP: limit decompressed body size for gzip-encoded OTLP write requests. #18408
• [BUGFIX] PromQL: Fix smoothed rate/increase returning zero instead of no result when all data falls strictly after the query range. #18523
• [BUGFIX] PromQL: Fix metric name not being dropped when last_over_time or first_over_time is applied to subqueries containing name-dropping functions like abs(). #18409
• [BUGFIX] PromQL: Fix missing warning when mixing exponential and custom-bucket histograms in stats queries. #18660
• [BUGFIX] PromQL: Fix parsing of range() keyword in duration expressions such as foo[5m+range()]. #18623
• [BUGFIX] PromQL: Fix smoothed vector selector returning no results in binary operations when the @ modifier is used. #18531
• [BUGFIX] PromQL: Reject NaN, infinite, and out-of-range duration expressions instead of silently producing an out-of-range time.Duration. #18639
• [BUGFIX] Scrape: Fix panic when scraping malformed native histograms. #18414
• [BUGFIX] Scrape: fix panic when scraping a target exposing a summary with no quantiles via the protobuf format. #18382
• [BUGFIX] Scrape: fix scrape failure log file occasionally not applied after a configuration reload. #18421
• [BUGFIX] TSDB: Allow retention percentage with new data path. #18628
• [BUGFIX] TSDB: Preserve decimal precision in percentage-based retention #18374
• [BUGFIX] TSDB: fix prometheus_tsdb_head_chunks going negative after WAL replay #18401
• [BUGFIX] TSDB: panic with native histograms during query of overlapping chunks. #18692
• [BUGFIX] Tracing: fix startup failure for insecure OTLP HTTP tracing #18469
• [BUGFIX] UI: Escape label values offered by PromQL autocomplete. #18658
• [BUGFIX] UI: Improve Y-axis tick label precision for graph values over small ranges. #18682
• [BUGFIX] prometheus_sd_refresh* and prometheus_sd_discovered_targets metrics for specific scrape jobs are deleted when the scrape job is removed. #17614
• [BUGFIX] Remote: fixed validation for received RW2 requests when parsing metadata unit symbols. This fixes a case when request would cause (recovered) handler panic. #18641
• [BUGFIX] TSDB/Agent: fix race in agent appender where concurrent appends for the same label set could produce duplicate in-memory series and duplicate WAL records. #18292
• [BUGFIX] Config: Update --enable-feature flag description and sort feature names. #18487

This release contains security fixes, new features (especially around PromQL and Service Discovery), performance improvements in TSDB, Start Timestamp improvements and numerous bug fixes.

Thanks to all contributors!

Key Highlights

• Security: Two security vulnerabilities have been addressed: a denial of service in remote-write (snappy decompression limit) and a secret exposure leak in STACKIT service discovery.
• PromQL & Metadata: Several features and bug fixes related to the experimental "start timestamps" support, including updates to rate(), irate(), increase(), and resets(). New experimental functions start(), end(), range(), and step() are introduced.
• TSDB Performance: Optimizations in head chunk lookup (constant time) and mmap operations to reduce CPU usage.
• Service Discovery: Added support for DigitalOcean Managed Databases and Outscale VM, along with improvements to AWS SD (IPv6 support for EC2, external ID support).
• UI: Added a web interface for deleting time series and cleaning tombstones.

Changelog

• [SECURITY] Remote: Reject snappy-compressed received requests via Remote Write whose declared decoded length exceeds the 32MB. Thanks to @hibrian827 for reporting it. #18642
• [SECURITY] STACKIT SD: Fix secrets being exposed in plaintext via /-/config endpoint. Thanks to @August829 and @Phaxma for reporting. GHSA-39j6-789q-qxvh #18649
• [CHANGE] TSDB/Agent: Adds Start Timestamp field to all WAL Histogram samples in memory; used st-storage flag is enabled. #18221
• [FEATURE] API: Add /api/v1/status/self_metrics endpoint returning the current state of the Prometheus server's own metrics about itself as JSON. #18411
• [FEATURE] Discovery: Add DigitalOcean Managed Databases service discovery #18287
• [FEATURE] Prometheus: Add support for the aix/ppc64 compilation target #18321
• [FEATURE] Discovery: Add Outscale VM service discovery (outscale_sd_configs) for discovering scrape targets from the Outscale Cloud API. #18139
• [FEATURE] PromQL: Emit a warning when sort, sort_by_label or sort_by_label_desc is used within range (matrix) queries, as these functions do not have effect in that context. #18498
• [FEATURE] PromQL: Add start(), end(), range(), and step() experimental functions #17877
• [FEATURE] PromQL: Update resets() function to consider start timestamp resets. Hidden behind use-start-timestamps feature flag. #18627
• [FEATURE] Prometheus: Promote auto-reload-config as stable #18620
• [FEATURE] TSDB/Agent: Add CheckpointFromInMemorySeries option to agent.DB that enables checkpoint based on in-memory series. #17948
• [FEATURE] UI: Add a web interface for deleting time series and cleaning tombstones, accessible from the Status menu. #18390
• [FEATURE] PromQL: Use start timestamps for rate(), irate(), and increase() calculations, behind a feature flag use-start-timestamps. Doesn't work together with extended range selectors anchored and smoothed. #18344
• [FEATURE] Scrape: Added a feature flag st-synthesis which synthesizes unknown STs for scraped cumulative metrics. Useful when Remote Writing 2.0 with delta or Otel-based backends. #18279
• [FEATURE] promqltest: support @st annotation in load blocks to specify per-sample start timestamps. #18360
• [ENHANCEMENT] API: reject concurrent fgprof profiles. #18651
• [ENHANCEMENT] AWS SD: Add optional external_id field to ECS/MSK/RDS/Elasticache. #18579
• [ENHANCEMENT] AWS SD: Add optional external_id field. #17171
• [ENHANCEMENT] Discovery: Propagate SD target updates faster by introducing dynamic backoff interval instead of static 5s interval for throttling. #18187
• [ENHANCEMENT] Promtool: Add --header flag to query instant command, matching existing query range behaviour. #18418
• [ENHANCEMENT]: AWS SD: Allows EC2 service discovery to discover IPv6 addresses to communicate with target endpoints. The private IPv4 address remains the default when both IPv4 and IPv6 addresses are present. #16088
• [PERF] TSDB: Make head chunk lookup in range queries constant time instead of quadratic time #18302
• [PERF] TSDB: Skip entire stripes in mmapHeadChunks when no series need mmapping, reducing CPU utilization significantly at production-relevant scales. #18541
• [PERF] TSDB: Skip clean series during periodic head chunk mmap using cached head chunk count #18272
• [PERF] PromQL: Address FloatHistogram.KahanAdd performance regression on Go 1.26. #18568
• [BUGFIX] PromQL: Fix info() function incorrectly handling negated __name__ matchers #17932
• [BUGFIX] API: Return duration expressions in /parse_ast. #18624
• [BUGFIX] API: correctly document formats accepted for duration query request parameters (step, timeout and lookback delta) in OpenAPI spec #18305
• [BUGFIX] Scrape: AppenderV2 now tracks staleness even when OOO/duplicate series errors happen similar to AppenderV1 #18567
• [BUGFIX] Config: Validate remote_write queue_config fields at load time to prevent runtime panic and silent misconfiguration. #18209
• [BUGFIX] Discovery/Consul: Add health_filter for Health API filtering, fixing breakage when using Catalog-only fields like ServiceTags in filter. #18479 #18499
• [BUGFIX] OTLP: limit decompressed body size for gzip-encoded OTLP write requests. #18408
• [BUGFIX] PromQL: Fix smoothed rate/increase returning zero instead of no result when all data falls strictly after the query range. #18523
• [BUGFIX] PromQL: Fix metric name not being dropped when last_over_time or first_over_time is applied to subqueries containing name-dropping functions like abs(). #18409
• [BUGFIX] PromQL: Fix missing warning when mixing exponential and custom-bucket histograms in stats queries. #18660
• [BUGFIX] PromQL: Fix parsing of range() keyword in duration expressions such as foo[5m+range()]. #18623
• [BUGFIX] PromQL: Fix smoothed vector selector returning no results in binary operations when the @ modifier is used. #18531
• [BUGFIX] PromQL: Reject NaN, infinite, and out-of-range duration expressions instead of silently producing an out-of-range time.Duration. #18639
• [BUGFIX] Scrape: Fix panic when scraping malformed native histograms. #18414
• [BUGFIX] Scrape: fix panic when scraping a target exposing a summary with no quantiles via the protobuf format. #18382
• [BUGFIX] Scrape: fix scrape failure log file occasionally not applied after a configuration reload. #18421
• [BUGFIX] TSDB: Allow retention percentage with new data path. #18628
• [BUGFIX] TSDB: Preserve decimal precision in percentage-based retention #18374
• [BUGFIX] TSDB: fix prometheus_tsdb_head_chunks going negative after WAL replay #18401
• [BUGFIX] TSDB: panic with native histograms during query of overlapping chunks. #18692
• [BUGFIX] Tracing: fix startup failure for insecure OTLP HTTP tracing #18469
• [BUGFIX] UI: Escape label values offered by PromQL autocomplete. #18658
• [BUGFIX] UI: Improve Y-axis tick label precision for graph values over small ranges. #18682
• [BUGFIX] prometheus_sd_refresh* and prometheus_sd_discovered_targets metrics for specific scrape jobs are deleted when the scrape job is removed. #17614
• [BUGFIX] Remote: fixed validation for received RW2 requests when parsing metadata unit symbols. This fixes a case when request would cause (recovered) handler panic. #18641
• [BUGFIX] TSDB/Agent: fix race in agent appender where concurrent appends for the same label set could produce duplicate in-memory series and duplicate WAL records. #18292
• [BUGFIX] Config: Update --enable-feature flag description and sort feature names. #18487

This release fixes mutiple security issues.

We would like to thank the following people for the responsible disclosures:

• Shadowbyte (4c1dr3aper) - Charlie Lewis for the Remote-Read snappy decode vulnerability.

• Brett Gervasoni for the AzureAD OAuth client_secret vulnerability.

• @iiihaiii and @Ngocnn97 for the Old UI XSS vulnerability.

• [SECURITY] AzureAD remote write: Fix OAuth client_secret being exposed in plaintext via /-/config endpoint. GHSA-wg65-39gg-5wfj / CVE-2026-42151 #18590

• [SECURITY] Remote-read: Reject snappy-compressed requests whose declared decoded length exceeds the decode limit. GHSA-8rm2-7qqf-34qm / CVE-2026-42154 #18584

• [SECURITY] UI: Fix stored XSS via unescaped le label values in old UI heatmap chart tick labels. GHSA-fw8g-cg8f-9j28 #18588