# UTXO ## Chain Client Example for Bitcoin. #### Observer {% embed url="" %} #### Signer {% embed url="" %} ### Scanning Blocks The block scanner monitors the Asgard Addresses and looks for incoming UTXOs spending to those addresses. When it sees one performs validation on it and witnesses to MAYAChain. For Bitcoin, it looks that at least 1 output is spent to Asgard, and searchs for another output to have an `OP_RETURN`. These two outputs form the `amount` and `memo` witness to MAYAChain. ### Confirmation Counting The `txValue` is the sum of all transactions received in a block to Asgard vaults. The `blockValue` is the coinbase value, which includes fees and subsidy. If a miner forgets to add a coinbase value (it has happened) a default of 6.25 is used. (This should be updated every 4 years, or use logic to auto-update). ### Re-orgs Bifrost tracks the `BlockCacheSize = 144` blocks of transactions reported in a local KV store. Every time it detects a new block at a previous height it has seen, it checks for the presence of every transaction it has reported. If the transaction is missing then it has been re-orged out. The missing txID is reported to MAYAChain as an `ErrataTx` ### Network Fees Reported as `sats/byte` where the fee rate is computed over the last block. Reports the highest seen in the last 20 blocks. ### Handling Gas The gas amount for a transaction is just the difference between outputs and inputs.\\ ### Other Considerations #### UTXO consolidation UTXOs consume inputs, and these inputs need to be signed independently. Thus consuming 15 inputs requires 15 times the TSS bandwidth than a single input. To prevent runaway liabilities the client will automatically enter a TSS signing ceremony for Asgard every 15 inputs to consolidate them back to one. This transaction uses the `consolidate` memo and can be seen regularly on MAYAChain vaults. #### ReplaceByFee RBF transactions allow the spender to double-spend with a higher fee. Users can use RBF transactions to spend to Asgard, but RBF does not need to be used in the THORChain vaults. ## Wallet Client UTXO clients implemented in XChainJS have the following nuances: ### Fees The wallet client should spend with a fee rate at least equal to what is reported on `inbound_addresses` - if not it risks not being confirmed by the time the vault migrates. ### Pending UTXOS Do not consume pending transactions when spending to Asgard (with a memo) since it may consume a low-fee tx and get stuck. ### MEMO The memo is inserted as an OP\_RETURN in an output. It can be any output. The MEMO is limited to 80 bytes, so it should be trimmed and use abbreviated memos or Asset identifiers where possible. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.mayaprotocol.com/mayachain-dev-docs/protocol-development/chain-clients/utxo.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.