New Opcodes

EIP-8141 introduces four new opcodes that provide the EVM interface for frame transaction execution and introspection.

APPROVE (0xaa)

The most significant new opcode. APPROVE is the mechanism by which a frame signals that the transaction sender and/or gas payer has been verified.

Stack

Position	Value
top - 0	offset — return data memory offset
top - 1	length — return data length
top - 2	scope — what is being approved

Scope Values

Scope	Meaning
0x0	Approve execution — sender authorizes future SENDER mode frames
0x1	Approve payment — account commits to paying gas costs
0x2	Approve both execution and payment

Behavior

APPROVE works like RETURN (exits the frame successfully) but additionally updates transaction-scoped approval state:

• Scope 0x0: Sets sender_approved = true. Only valid when frame.target == tx.sender. Cannot be called twice.
• Scope 0x1: Increments the sender's nonce, collects gas fees from the account, sets payer_approved = true. Requires sender_approved == true first. Cannot be called twice.
• Scope 0x2: Combines both — sets sender_approved, increments nonce, collects gas, sets payer_approved. Only valid when frame.target == tx.sender. Cannot be called twice.

Constraints

• ADDRESS must equal frame.target — only the frame's target contract can call APPROVE
• The approval bits in frame.mode (bits 9-10) must permit the requested scope
• Any violation results in an exceptional halt or frame revert

TXPARAM (0xb0)

An introspection opcode for accessing transaction metadata. Gas cost: 2.

Stack

Position	Value
top - 0	param — which field to read
top - 1	in2 — frame index (or must be 0)

Parameters

Transaction-level (in2 must be 0)

param	Returns
0x00	Transaction type
0x01	nonce
0x02	sender
0x03	max_priority_fee_per_gas
0x04	max_fee_per_gas
0x05	max_fee_per_blob_gas
0x06	Max cost (worst-case total fee)
0x07	len(blob_versioned_hashes)
0x08	compute_sig_hash(tx)
0x09	len(frames)

Frame-level (in2 = frame index)

param	Returns
0x10	Currently executing frame index
0x11	target of frame at index
0x12	gas_limit of frame at index
0x13	mode of frame at index
0x14	len(data) of frame at index (0 for VERIFY frames)
0x15	status of frame at index (only past frames)

Error Cases

• Invalid param values: exceptional halt
• Out-of-bounds frame index: exceptional halt
• Accessing status of current or future frame: exceptional halt
• len(data) returns 0 for VERIFY mode frames (data is elided)

FRAMEDATALOAD (0xb1)

Loads a 32-byte word from another frame's data. Gas cost: 3 (matches CALLDATALOAD).

Stack

Position	Value
top - 0	offset — byte offset into frame data
top - 1	frameIndex — which frame's data to read

Semantics match CALLDATALOAD — reads 32 bytes starting at offset, zero-padding if the offset extends beyond the data length. When targeting a VERIFY frame, the returned data is always zero.

FRAMEDATACOPY (0xb2)

Copies data from another frame into memory. Gas cost matches CALLDATACOPY (fixed cost of 3 + memory expansion + copy cost).

Stack

Position	Value
top - 0	memOffset — destination in memory
top - 1	dataOffset — byte offset into frame data
top - 2	length — bytes to copy
top - 3	frameIndex — which frame's data to read

When targeting a VERIFY frame, no data is copied (the region is zero-filled per standard memory expansion).