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Overview

Token-2022 is Solana’s next-generation token program. It supports extensions that add new behaviours to tokens — including a transfer fee extension that automatically deducts a percentage of each transfer. The Umbra SDK fully supports Token-2022 mints, including those with transfer fee extensions.

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Transfer Fees

When you deposit a Token-2022 token that has a transfer fee configured, the fee is deducted by the Token-2022 program before tokens reach the pool custody account. The SDK accounts for this by:
  1. Fetching the mint account to detect the TransferFeeConfig extension.
  2. Calling the epoch info provider to determine the current epoch.
  3. Selecting the applicable fee schedule (Token-2022 supports epoch-based fee changes).
  4. Computing actualReceived = amount - transferFee.
  5. Applying Umbra protocol fees on top of actualReceived.
The amount credited to your ETA is actualReceived - protocolFees.

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Epoch Info Provider

Transfer fee schedule selection requires knowing the current Solana epoch. This is why epochInfoProvider is part of the IUmbraClient interface — it is fetched once per deposit operation for Token-2022 mints. For standard SPL tokens (Token program), the epoch info provider is not called. The provider defaults to an RPC-based implementation constructed from rpcUrl. You can override it if needed: 
import { getUmbraClient } from "@umbra-privacy/sdk";

const client = await getUmbraClient(
  { signer, network, rpcUrl, rpcSubscriptionsUrl },
  {
    // Custom epoch info provider (e.g., for testing with a fixed epoch).
    epochInfoProvider: async () => ({
      epoch: 500n,
      slotIndex: 0n,
      slotsInEpoch: 432000n,
      absoluteSlot: 216000000n,
      blockHeight: 210000000n,
    }),
  },
);

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Fee Calculation

The SDK uses the same fee calculation as the Token-2022 program: 
transferFee = min(
  floor(amount × feeBasisPoints / 10_000),
  maximumFee
)
Where feeBasisPoints and maximumFee are read from the epoch-appropriate fee schedule in the mint’s TransferFeeConfig extension. Note that Token-2022’s BPS divisor is 10,000, while Umbra’s protocol-fee BPS divisor is 16,384 (2^14). Don’t confuse the two.

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No Special Configuration Required

You do not need to do anything special to use Token-2022 mints. Simply pass the Token-2022 mint address as you would any other mint: 
import { getATAIntoETADirectDepositorFunction } from "@umbra-privacy/sdk/deposit";

const TOKEN22_MINT = "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v"; // USDC

const deposit = getATAIntoETADirectDepositorFunction({ client });
const result  = await deposit(client.signer.address, TOKEN22_MINT, 1_000_000n);
The SDK detects that the mint is a Token-2022 program account, checks for a transfer fee extension, and handles the fee deduction automatically.

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Affected Operations

Transfer fee handling applies to these ATA-source operations:
  • getATAIntoETADirectDepositorFunction — fetches epoch info only when a Token-2022 transfer fee is detected.
  • getATAIntoSelfBurnableStealthPoolNoteCreatorFunction — same.
  • getATAIntoReceiverBurnableStealthPoolNoteCreatorFunction — same.
  • getETAIntoATAWithdrawerFunction — same (the transfer back into an ATA also crosses the Token-2022 boundary).
  • getSelfBurnableStealthPoolNoteIntoATABurnerFunction — same.
Operations that route entirely between an ETA and the on-chain Stealth Pool (e.g. self-burnable → ETA, receiver-burnable → ETA) are not affected by Token-2022 transfer fees, because the transfer happens within the Umbra program and does not cross the Token-2022 transfer fee boundary. Each of the affected factories accepts an epochInfoCommitment option (defaults to "confirmed") to control the commitment level used when fetching the current epoch for fee schedule selection.