Transactions

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v1 only

Every transaction the router builds is v1 (SIMD-0385, active on mainnet since slot 447,120,000). There is no v0 and no legacy form: txVersion: 0 and asLegacyTransaction: true answer 400.

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Getting a transaction

The build answers instructions by default. Two ways to a transaction:

• Let the router serialize it: send "serialize": true. You get swapTransaction (base64, unsigned) and lastValidBlockHeight. The blockhash is the router’s, at most a few seconds old; send before it expires.
• Assemble it yourself: put setupInstructions, then every instruction of swapInstructions, then cleanupInstruction, then otherInstructions, and set the header from transactionConfig. Or post them to POST /tx/v1, which serializes any instructions you give it as an unsigned v1 transaction (useful to add your own instructions).

The swap instruction has no deadline of its own: only the blockhash expires the transaction.

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Compute budget

transactionConfig carries what goes in the v1 header: A limit left out of a v1 header counts as zero, not as a default: keep every field the router gives you. The compute-unit limit is sized from the route’s steps (walkSteps in the quote); if you strip walkSteps from a quoteResponse, the build declares the maximum for those hops and you pay priority fee on it.

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Priority fee

The first of these that the build body sets decides the fee: Nothing set means no priority fee: absent is not auto. The fee is charged on the declared compute-unit limit, not on the units the swap ends up using. costs.priorityFeeSource says where the number came from (client, chain, floor, ceiling, none).

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Tips

• prioritizationFeeLamports: {"jitoTipLamports": N} adds a transfer of N lamports to a Jito tip account in otherInstructions (and no priority fee from that field).
• tipWallet + tipLamports tip any wallet you choose, and win over the Jito field.

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What the user pays

costs estimates the lamports the transaction costs the user, as decimal strings: rentLamports is an upper bound: it counts every account the setup creates as if the user had none of them. A user who already has the token account pays less.