Hi all,<br /><br />I'm Aaron Zhang, an independent developer focused on Bitcoin script engineering and Taproot experimentation.<br /><br />I’d like to share a hands-on project involving a fully constructed 4-leaf Taproot Merkle tree in Python, with testnet-validated spending transactions and in-depth analysis of control block internals.<br /><br />This work features:<br /><br />- Construction of a <b>Taproot address with 4 distinct script leaves</b>:<br />    1. `OP_SHA256` + `OP_EQUAL` hashlock<br />    2. 2-of-2 `OP_CHECKMULTISIG`<br />    3. `OP_CSV` + `OP_CHECKSIG`<br />    4. `OP_CHECKSIG`<br /><br />- A total of <b>five spending paths</b>, including four script path spends and one key path spend, all confirmed through on-chain transactions on Bitcoin testnet.<br /><br />- Merkle tree construction and Taproot output key tweaking (internal key + script tree root), followed by a **byte-by-byte breakdown of the control blocks**, including:<br />    - Control byte (leaf version + parity)<br />    - Internal public key<br />    - Ordered Merkle sibling hashes<br /><br />- <b>Code-level analysis and experimental validation of how these control blocks</b> are constructed and verified against the Taproot output, based on actual testnet spends.<br /><br />- <b>Witness stack inspection and visualization of script execution</b>, showing the actual runtime behavior for each script path.<br /><br />Resources:<br /><br /><b>- Part 1: 4-leaf tree construction and testnet validation  <br /></b>  https://medium.com/@aaron.recompile/building-a-4-leaf-taproot-tree-in-python-the-first-complete-implementation-on-bitcoin-testnet-c8b66c331f29<br /><br /><b>- Part 2: Control block structure and stack visualization  <br /></b>  https://medium.com/@aaron.recompile/taproot-control-block-deep-analysis-stack-execution-visualization-5ff10f98032c<br /><br />- GitHub repo with code, testnet transactions, and diagrams  <br />  https://github.com/btcstudy/btcstudy.github.io/tree/main/Not-Just-Hodling:bitcoin-script-Engineering/demo3_taproot_4leaf<br /><br />This project aims to provide a fully verifiable and pedagogical example of non-trivial Taproot path spends, helping developers better understand script trees, control blocks, and Tapscript execution through practical experimentation.<br /><br />I’d be happy to receive any feedback or discussion around:<br />- Control block design and merkle path optimization<br />- Spend path visibility and privacy tradeoffs<br />- Tooling for visualizing script-path execution and verification<br /><br />Thanks and best regards,  <br />Aaron Zhang  <br />[@aaron.recompile](https://medium.com/@aaron.recompile)  <br />GitHub: https://github.com/btcstudy

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