Add setComputeUnitPrice to a Jupiter-returned VersionedTransaction in Python by rebuilding the Message with a prepended CompiledInstruction

Problem: the Jupiter swap API hands back an already-built base64 VersionedTransaction. There is no Python helper to "add an instruction" to it, so setting a compute unit price or limit locally (rather than via the API's prioritizationFeeLamports) appears impossible. VersionedTransaction and its Message are effectively immutable in solders.

Approach that works: decompose the message, inject a compiled ComputeBudget instruction at position 0, rebuild, and re-sign. The subtlety is that a compiled instruction refers to its program by *index into the message's account keys*, so the ComputeBudget program id must be appended to account_keys first and the new instruction's program_id_index set to the old length of that list:

rawTransaction = VersionedTransaction.from_bytes(base64.b64decode(apiTransaction)) priorityFee = set_compute_unit_price(gas) accountKeys = rawTransaction.message.account_keys lengthAccountKeys = len(accountKeys) accountKeys.append(priorityFee.program_id) rawInstructions = rawTransaction.message.instructions priorityInstruction = CompiledInstruction( program_id_index=lengthAccountKeys, data=priorityFee.data, accounts=rawInstructions[0].accounts, ) ix = [priorityInstruction, *rawInstructions] newTransactionMessage = Message.new_with_compiled_instructions( num_required_signatures=rawTransaction.message.header.num_required_signatures, num_readonly_signed_accounts=rawTransaction.message.header.num_readonly_signed_accounts, num_readonly_unsigned_accounts=rawTransaction.message.header.num_readonly_unsigned_accounts, account_keys=accountKeys, recent_blockhash=recentBlockhash, instructions=ix, ) userSignature = userKeypair.sign_message(message.to_bytes_versioned(newTransactionMessage))

Ordering matters: the ComputeBudget instruction must precede the swap. Re-signing is mandatory because the message bytes changed. Also note compute unit *price* (micro-lamports per CU) and *limit* (CU count) are separate instructions and the fee is their product — passing prioritizationFeeLamports to the API instead gives a total, not a rate. Header fields must be copied verbatim or signature verification fails.

Source: adapted from a Stack Exchange answer by sashavsthewrld (question by TheLastSamurai), https://solana.stackexchange.com/questions/12788/how-to-set-compute-limit-and-compute-unit-price-using-python — CC BY-SA 4.0