Transaction Structure

RLP Encoding

Frame transactions use EIP-2718 typed transaction envelopes with type 0x06. The payload is defined as:

[chain_id, nonce, sender, frames, max_priority_fee_per_gas, max_fee_per_gas, max_fee_per_blob_gas, blob_versioned_hashes]

Where each frame is:

[mode, target, gas_limit, data]

Notable Differences from Existing Transaction Types

Aspect	Legacy / EIP-1559 / EIP-4844	Frame Transaction
Sender	Derived from signature via ecrecover	Explicit sender field in the payload
Signature	Top-level field(s)	Embedded in frame data (typically a VERIFY frame)
Execution target	Single to field	Multiple frames, each with its own target
Value	Explicit value field	No value field — transfers handled via frame execution
Access list	Optional (EIP-2930)	Not included

The explicit sender field is a fundamental shift: since the transaction is not necessarily signed with ECDSA, the sender cannot be recovered from a signature. The sender is declared and then verified by a VERIFY frame during execution.

Field Constraints

The spec defines static validity constraints:

assert tx.chain_id < 2**256
assert tx.nonce < 2**64
assert len(tx.frames) > 0 and len(tx.frames) <= MAX_FRAMES  # 1..1000
assert len(tx.sender) == 20
assert tx.frames[n].mode < 3
assert len(tx.frames[n].target) == 20 or tx.frames[n].target is None

When target is None (null), it resolves to tx.sender during execution.

Blob Support

Frame transactions support EIP-4844 blobs. When no blobs are included:

• blob_versioned_hashes must be an empty list
• max_fee_per_blob_gas must be 0

Receipt Format

The receipt structure differs from standard transactions:

[cumulative_gas_used, payer, [frame_receipt, ...]]

Where each frame receipt is:

[status, gas_used, logs]

Key additions:

• payer — the address that paid gas fees (recorded here because it cannot be determined statically from the transaction, unlike legacy transactions where sender = payer)
• Per-frame status and logs — each frame gets its own receipt entry

Signature Hash

The canonical signature hash elides data from VERIFY frames:

def compute_sig_hash(tx: FrameTx) -> Hash:
    for i, frame in enumerate(tx.frames):
        if frame.mode == VERIFY:
            tx.frames[i].data = Bytes()
    return keccak(rlp(tx))

This is critical for two reasons:

1. The signature itself lives in VERIFY frame data — it cannot be part of its own hash.
2. It enables future aggregation of cryptographic operations across VERIFY frames.
3. For gas sponsorship, leaving sponsor VERIFY data malleable allows sponsors to attach their authorization after the sender has signed.