Canopy Depth

The number of top levels of a Concurrent Merkle Tree that are cached on-chain within the CMT account, reducing the Merkle proof size that clients must include in transactions. A canopy depth of D means the top D levels (2^D - 1 nodes) are stored on-chain, so clients only need to supply (tree_depth - D) sibling hashes instead of the full tree_depth. Deeper canopies reduce transaction size and compute costs but increase the CMT account's rent-exempt balance. Choosing optimal canopy depth is a cost trade-off between on-chain storage rent and per-transaction proof overhead.