• [CHANGE] Promote the auto-gomemlimit feature flag to the --auto-gomemlimit command-line flag. This is a breaking change: the --enable-feature=auto-gomemlimit option has been removed. #5464
• [CHANGE] Remove the deprecated types package in favor of the alert package. #5585
• [CHANGE] eventrecorder: Every output now requires a name. This is a breaking change: configurations with unnamed outputs fail to load. The name identifies the output in metrics and logs instead of its URL, broker or topic. #5393
• [CHANGE] eventrecorder: The output data format now uses the new events/v2 schema. This is a breaking change: alert labels, alert annotations, group labels, silence annotations, and muted-alert labels are JSON maps, and protobuf consumers must use the new schema. #5409, #5500
• [FEATURE] Add a distroless container image. #5258
• [FEATURE] amtool: Look up the default config file in %APPDATA% and %ProgramData% on Windows. #5073
• [FEATURE] api: Add an experimental ConnectRPC API served alongside /api/v2/ under the version-neutral /api/ prefix, exposing the Connect, gRPC, and gRPC-Web protocols plus the gRPC Health Checking Protocol and server reflection. The first service is status.v3.StatusService. #5377, #5506, #5507, #5508, #5509
• [FEATURE] incidentio: Add templated metadata field. #5022
• [FEATURE] pagerduty: Report more specific failure reasons in alertmanager_notifications_failed_total. #5659
• [FEATURE] rocketchat: Add message_text option to set the message text shown in desktop and push notifications. #5595
• [FEATURE] slack: Add post_updates_to_thread option to post subsequent notifications of an alert group as replies in the thread of the initial message. #5540
• [FEATURE] telegram: Add timeout option to limit how long a notification request may take. #5127
• [FEATURE] telegram: Count only visible HTML text toward the message length limit, excluding link URLs. #5499
• [FEATURE] template: Add addDuration function to shift a timestamp by a duration such as -30m and return it in Unix milliseconds. #5550
• [FEATURE] template: Allow the join function to accept slices and arrays of any type. #5233
• [FEATURE] timeinterval: Allow weekday ranges to wrap around the end of the week, e.g. friday:monday. #5579
• [FEATURE] ui: Make the creator and comment of a silence optional, matching the API. #5471
• [FEATURE] ui: Serve the new Mantine UI at /ui/ alongside the existing UI. #5502, #5538, #5539, #5537
• [ENHANCEMENT] Compute alert fingerprints once at ingestion instead of on every mute check, reducing CPU usage and allocations. #5583
• [ENHANCEMENT] api: Speed up /api/v2/alerts/groups by evaluating mutes only once per alert and group. #5674
• [ENHANCEMENT] cluster: Fix the memeberlist typo in error messages. #5472
• [ENHANCEMENT] docs: Add a Gotify example using a custom webhook payload. #5408, #5498
• [ENHANCEMENT] docs: Add a reusable HTML email template example. #5391
• [ENHANCEMENT] docs: Clarify the usage of the KV Remove template function. #5297
• [ENHANCEMENT] docs: Clarify which route options are inherited by child routes. #5565
• [ENHANCEMENT] docs: Correct the PagerDuty default config. #5397
• [ENHANCEMENT] docs: Document OAuth2 support in the http_config of jira_config. #5571
• [ENHANCEMENT] docs: Document VictorOps custom fields. #5399
• [ENHANCEMENT] docs: Document project and issue_type in jira_config as templated strings. #5549
• [ENHANCEMENT] docs: Document victorops_api_key and victorops_api_key_file in the global config. #5168
• [ENHANCEMENT] docs: Fix rocketchat_config defaults and field types. #5591
• [ENHANCEMENT] docs: Fix the tracing config key, which was misspelled as traciing. #5437
• [ENHANCEMENT] notify: Add the receiver name to the log message for failed notifications. #5401
• [ENHANCEMENT] silences: Reduce allocations when computing the alertmanager_silences metric. #5460
• [ENHANCEMENT] victorops: Use Splunk On-Call branding in documentation and error messages without renaming configuration fields. #5402
• [BUGFIX] api: Report alerts muted by time intervals as of the time of the request instead of the last group flush, matching silences and inhibitions. #5661
• [BUGFIX] cluster: Downgrade memberlist to v0.5.4 to fix Failed to read remote state: user state length (...) exceeds limit errors. #5640
• [BUGFIX] config: Fix merging of global configs for the smtp, opsgenie, victorops and rocketchat notifiers. #5448, #5457
• [BUGFIX] discord: Retry notifications on HTTP 429 (rate limited) instead of dropping them. #5496
• [BUGFIX] httpserver: Fix the /-/reload endpoint getting stuck when the client cancels the request. #5234
• [BUGFIX] notify: Wait the full backoff interval before retrying a notification that failed slowly. #5497, #5389, #5553
• [BUGFIX] opsgenie: Respect the notification timeout and tracing span for the update-message request sent when update_alerts is enabled. #5465
• [BUGFIX] pagerduty: Report the failure reason of Events API v1 requests in alertmanager_notifications_failed_total instead of reason="other". #5505
• [BUGFIX] pushover: Trim whitespace from token_file and user_key_file contents so keys stored in files with a trailing newline are accepted. #5590
• [BUGFIX] silences: Treat a silence as expired at exactly its end time, consistent with the API. #5665
• [BUGFIX] silences: Use a single evaluation time for each read or write of silences. #5666
• [BUGFIX] slack: Avoid a panic when update_message relies on global.slack_api_url. #5589
• [BUGFIX] slack: Retry notifications on HTTP 429 (rate limited) and honor the Retry-After header instead of dropping them. #5048
• [BUGFIX] telegram: Redact the bot token from logged notification errors. #5254
• [BUGFIX] telegram: Report the failure reason in alertmanager_notifications_failed_total. #5375
• [BUGFIX] template: Preserve quoted numeric strings as strings in templated JSON fields. #5098
• [BUGFIX] timeinterval: Fix negative days_of_month resolving one day early in months with a DST transition. #5447
• [BUGFIX] timeinterval: Reject month numbers outside 1-12. #5626
• [BUGFIX] webex: Fix a panic when truncating long notifications containing non-ASCII characters. #5544
• [BUGFIX] webex: Retry notifications on HTTP 429 (rate limited) and honor the Retry-After header instead of dropping them. #5548
• [BUGFIX] wechat: Report template errors in corp_id and api_secret instead of sending a token request with empty values. #5688