Stream blocks

StreamBlocks delivers raw HyperCore blocks as they are produced — every signed action the block contained, together with its execution results. This is ideal for full-chain indexers, action and response analysis, deposit and transfer monitoring, and reconciliation against your own records.

Overview

HyperCore produces a block roughly every 70 ms, and block numbers increment by exactly one. The stream reflects that directly:

• One message per block, in order, including blocks with no activity
• Block number is the stream sequence — there is no separate sequence counter to track
• A missing block number is therefore an unambiguous gap
• Blocks are delivered as passthrough — the raw block, not a normalized projection

Because the stream is dense, gap detection needs no heartbeat and no bookkeeping beyond remembering the last block you processed.

Request structure

message StreamBlocksRequest {
  optional uint64 start_height = 1;
  string cursor = 2;
}

Start height

Field: start_height Type: uint64

Block number to begin streaming from. Omit to start from the current head.

Cursor

Field: cursor Type: string

Resume token from a previous session. Opaque — store it and return it unmodified. Takes precedence over start_height when both are supplied.

Response structure

message BlockEnvelope {
  uint64 height = 1;
  string cursor = 2;
  BlockData block = 3;
}

Key fields

height: Block number and stream sequence. Compare it with the last processed block to detect a gap.

cursor: Resume position for this message. Persist it after processing.

block: The raw block.

Block contents

See raw and normalized HyperCore blocks for how these relate to the normalized objects returned by the JSON-RPC block methods.

Recovering from a gap

1. Track the block number of the last message you processed.
2. On reconnect, send that number plus one as start_height, or send your stored cursor.
3. If parent_round does not match your last processed block, fetch the missing range with hl_getBatchBlocks and reconcile before resuming.

Replay covers a short reconnect window, not long-range recovery. Gaps wider than that window cannot be replayed on the stream — use the block lookup methods above to fetch the missing range, then resume.

Stream vs block lookup

Message size

Raw HyperCore blocks can be large, and high-activity blocks substantially more so. Configure your client's maximum receive size and processing queues accordingly.