Grafana Alloy v1.21: OpenTelemetry engine moves to Public Preview

Grafana Labs announced on 3 November that with the release of Alloy v1.21.0, the OpenTelemetry (OTel) engine of the agent moves from experimental stability to Public Preview, standing alongside the default engine already familiar to users. For those managing observability stacks on VPS or bare metal, the update brings the ability to run native OTLP pipelines without relying on Alloy's own configuration syntax.\n\n## What changes in practice\n\nAs of Alloy v1.21.0, the OTel engine has moved to Public Preview and runs alongside the already-known default engine. The OTel engine, according to Grafana, executes standard collector YAML without translation and without Alloy syntax: if you already have a configuration for a collector, you already have one for the OTel engine. In practice, the binary accepts both alloy run (default engine) and alloy otel --config=config.yaml, using the same subcommands (validate, components, print-config) as the upstream OpenTelemetry Collector project.\n\nCentralised management is not new to this release: remote configuration was one of the first gaps filled after the initial launch, and since v1.19.0 it has been possible to manage the OTel engine configuration centrally with Fleet Management.\n\n## Context the announcement doesn't provide\n\nThe OTel engine didn't debut in this release: according to Alloy's version history, it was introduced with experimental stability in v1.14.0, over a year ago. Version 1.21.0 was released on 16 October 2026 and brings the underlying collector update to OpenTelemetry Collector v0.162.0, along with several breaking changes to verify before upgrading: enabling WAL in loki.write now requires the --stability.level=experimental flag, whilst maximum retries for otelcol.receiver.kafka and otelcol.exporter.kafka now default to 20 attempts.\n\n## Who should do what\n\nAnyone managing Alloy installations for collecting metrics, logs and traces should read the full changelog before upgrading, particularly if using Loki pipelines with WAL enabled or Kafka connectors: both areas have changed default behaviours in this release. The official documentation for the OTel engine remains available in the "set-up" section of the Alloy docs.\n