Block streams replace record streams as the canonical network output format. Mirror node operators and consumers of record files must deploy v0.155.1 of the hiero-mirror-node, or a later cutover-compatible release, before this date to continue ingesting network data without interruption.
The change unifies the existing data streams: record streams, event streams, signature files, and sidecars into a single signed block format defined in HIP-1056. The cutover plan is specified in HIP-1193.
Who Needs to Take Action
- Mirror node operators (commercial providers and self-hosted)
- Direct consumers of record files
Not affected: the Hedera API (HAPI), the Hedera SDKs (Java, Go, JavaScript, Rust), mirror node explorer, mirror node REST API and the JSON-RPC Relay. Application developers do not need to update code. The Hiero local node continues to use record streams during the cutover period and has a separate advisory deprecation ending September 2026.
What’s Changing
Under the current architecture, consensus nodes produce four output streams and upload them to cloud storage. After the cutover, consensus nodes push a single block stream over gRPC to block nodes (HIP-1081), a new infrastructure tier introduced as part of the migration. Mirror nodes read from block nodes, with cloud storage available as a fallback.
Each block contains all transactions and their results, all consensus events, state changes applied during the block, and a single aggregated Threshold Signature Scheme (TSS) signature from the majority of the network by consensus weight. price.
What You Need to Do
Mirror node operators have one required action: deploy a cutover-compatible mirror node release in production before September 2026. Steps to ensure compatibility:
Update to Mirror Node v0.155.1 or later. Releases earlier than v0.155.1 stop ingesting new data at the cutover. Validate ingestion in staging first against testnet and previewnet, where block streams are already live.
Grant read IAM on the new buckets. Pre-grant read access to: hedera-mainnet-recent-block-streams, hedera-testnet-recent-block-streams, and hedera-previewnet-recent-block-streams for the same principal that currently reads hedera-{network}-streams.
Confirm ingestion after the cutover. The configuration flag hiero.mirror.importer.block.sourceType defaults to AUTO. Mirror nodes auto-detect when the cutover has occurred and begin reading block streams. After the cutover, the REST endpoint /api/v1/blocks?order=desc&limit=1 should return a block timestamp within roughly five seconds of wall time.
The legacy hedera-{network}-streams bucket and the historical record files inside it remain available after the cutover. New data stops being written to those buckets.
Timeline
- July 2026 (consensus node v0.75 mainnet): Stage 1 of the cutover. Wrapped Record Blocks (HIP-1427) begin streaming through block nodes. Record-file consumers are not affected.
- September 2026 (consensus node v0.77 mainnet): TSS cutover. Block stream gains network-aggregated TSS signatures. Mirror node operators must be on the minimum supporting version by this point.
- From September 2026 onwards: Block stream is the canonical network output format. Historical record files remain available via the legacy bucket; removing the legacy bucket would require a separate HIP.
Resources and Support
- HIP-1056: Block Streams
- HIP-1081: Block Node
- HIP-1193: Record Stream to Block Stream Cutover
- Hiero Local Node Deprecation
- hiero-mirror-node release notes
- hiero-block-node
- Mirror node operator discussion: Hedera Discord
Mirror node operators should deploy v0.155.1 or later before September 2026, review HIP-1193 for the full cutover specification, and join the Hedera Discord to track the schedule.
