• [SECURITY] Container images: Update CA certificates to distrust "emSign ECC Root CA - G3" and "Comodo AAA Services root" following the compromise of eMudhra intermediate CA private keys.
• [SECURITY] Build with Go 1.27.3 to fix vulnerabilities in net/http, net/textproto, crypto/tls and html/template.
• [SECURITY] Bump golang.org/x/net to v0.60.0 to fix HTTP/2 vulnerabilities (GO-2026-6603, GO-2026-6610, GO-2026-6611, GO-2026-6612, GO-2026-6617).

• [SECURITY] Container images: Update CA certificates to distrust "emSign ECC Root CA - G3" and "Comodo AAA Services root" following the compromise of eMudhra intermediate CA private keys.
• [SECURITY] Build with Go 1.26.10 to fix vulnerabilities in net/http, net/textproto, crypto/tls and html/template.
• [SECURITY] Bump golang.org/x/net to v0.60.0 to fix HTTP/2 vulnerabilities (GO-2026-6603, GO-2026-6610, GO-2026-6611, GO-2026-6612, GO-2026-6617).
• [SECURITY] Bump OpenTelemetry to v1.45.0 to fix exporter endpoint URLs leaking into info logs (GO-2026-6505).
• [CHANGE] Building Prometheus now requires Go 1.26 or later.

• [SECURITY] Bump google.golang.org/grpc to v1.83.1 to fix HTTP/2 DATA frame fragmentation memory exhaustion (GO-2026-6348). #19834
• [SECURITY] UI: Update vulnerable npm dependencies. #19834
• [BUGFIX] Agent: Ignore unknown WAL record types to allow rolling back from newer versions. #19814
• [BUGFIX] Federation: Fix corruption of float native histograms. #19679
• [BUGFIX] Scrape: Fix failing scrapes of protobuf float histograms with zero sample, zero and bucket counts, such as the result of recording rate(x[1m]) over a constant histogram. #19682

• [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....

• [BUGFIX] TSDB: Avoid WAL corruption after a failed WAL write in Agent mode. #19700

• [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....

• [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: v3.13.1...v3.13.2