The opcode

The opcode tells a vault which operation to run: a buffer of up to 16 bytes whose first byte is the operation.

Reading it

Vaults read byte 0 like this (from the sublink template):

(define-private (get-byte (opcode (optional (buff 16))) (position uint))
    (default-to 0x00 (element-at? (default-to 0x00 opcode) position)))

none or an empty buffer reads as 0x00. A pool treats that as a swap from A to B; a sublink rejects it.

dexterity-sdk sends all 16 bytes, zero-padded:

export const opcodeCV = (op: number): ClarityValue => {
  const b = new Uint8Array(16).fill(0);
  b[0] = op;
  return someCV(bufferCV(b));
};

One byte works too: Invest's liquidity buttons send 02 and 03.

Operations

Byte 0	OPCODES name	amount	dx	dy	dk
0x00	SWAP_A_TO_B	Token A in	Input¹	Token B out	0
0x01	SWAP_B_TO_A	Token B in	Input¹	Token A out	0
0x02	ADD_LIQUIDITY	LP tokens to mint	Token A paid in	Token B paid in	LP minted
0x03	REMOVE_LIQUIDITY	LP tokens to burn	Token A paid out	Token B paid out	LP burned
0x04	LOOKUP_RESERVES	Ignored, send 0	Reserve A	Reserve B	LP supply
0x05	OP_DEPOSIT	Tokens into the subnet	amount	amount	0
0x06	OP_WITHDRAW	Tokens out of the subnet	amount	amount	0
0x07	Not in the SDK	Ignored	Blocks since the last harvest²	Balance over that time²	Energy harvested²

¹ Charisma pools report the input after their LP fee. Wrappers report the input consumed. ² From execute. quote returns 0, 0 and the blocks since the last harvest.

Contracts prefix every constant with OP_ (OP_SWAP_A_TO_B, OP_HARVEST_ENERGY). OPCODES in dexterity-sdk drops the prefix for 0x00 to 0x04 and has no 0x07.

Who implements what

Vault	execute	quote	Any other opcode
Charisma pool (Launchpad template)	00 to 03	00 to 04	err u400
Early Charisma pool, e.g. charismatic-flow	00 to 03	00 to 03	err u400
Sublink	05, 06	05, 06	err u4002
External DEX wrapper	00, 01	00, 01, 04	err u400
energize-v1	07	07	err u4002
hooter-farm-rewards	00, 01	00, 01, 04	err u400

Caller	Sends
dexterity-sdk Router, building a route	00, 01, 05 into a subnet, 06 out of one
Invest, adding and removing liquidity	02, 03
Invest, refreshing reserves	04

Room to grow

• Byte 0 has 256 values. 0x00 to 0x07 are taken.
• No vault reads bytes 1 to 15 yet. They are room for an operation's parameters.
• A new operation needs a vault that understands it and a caller that sends it. The trait, the routers and existing vaults stay as they are.

Not the Blaze opcode

Blaze intents also have an opcode field of the same type, with a different job.

	Dexterity opcode	Blaze opcode
Lives in	Each execute or quote call, one per hop	A signed intent
Set by	Whoever builds the transaction	The signer, inside the signature
Says	Which operation a vault runs	Extra terms the signer commits to
Used today	Every vault call	Never: always none

Both appear in one Blaze swap:

See Signing: the opcode field.