# Payload envelope

The binary payload envelope shared by raw HTTP, QUIC streams and IPC records for transactions and bundles.

Source: https://docs.zerocopy.sh/api/payload-envelope

Every raw channel carries this payload: `/binary`, `/plaintext`, [QUIC](/api/quic#streams) streams and the agent's [IPC records](/api/ipc).

A payload whose first byte is not `0x00` is one signed transaction in wire format.

A payload that starts with `0x00` is an envelope:

| Offset | Size | Field |
| --- | --- | --- |
| 0 | 1 | `0x00` |
| 1 | 1 | Flags: `0x01` declared tip present, `0x02` bundle body. No other bits may be set. |
| 2 | 8 | Declared tip in lamports, `u64` little endian. Present only when flags include `0x01`. |
| 2 or 10 | rest | The body. |

Without the `0x02` flag, the body is one transaction. With it, the body is:

| Size | Field |
| --- | --- |
| 1 | Transaction count, 1 to 4 |
| 2 | Length of the next transaction, `u16` little endian, 1 to 4,096 |
| length | The transaction's wire bytes |

The length and transaction pair repeats once per transaction, and no bytes may follow the last one. The largest payload, a declared-tip bundle of four 4,096-byte transactions, is 16,403 bytes.

| Payload | Bytes |
| --- | --- |
| One transaction | `TX` |
| One transaction, declared tip of 1,000,000 lamports | `00 01 40 42 0f 00 00 00 00 00 TX` |
| Bundle of two | `00 02 02 L1 L1 TX1 L2 L2 TX2` |
| Bundle of two, declared tip of 1,000,000 lamports | `00 03 40 42 0f 00 00 00 00 00 02 L1 L1 TX1 L2 L2 TX2` |

Here `L1 L1` is the little-endian length of `TX1`. An envelope that breaks these rules is refused as [`malformed`](/errors#malformed) with problem `invalid_envelope`, or as [`bundle_size`](/errors#bundle_size) when the count is 0 or above 4.