Online services use a dedicated public receiving branch. Public extended keys are privacy-sensitive. A non-hardened child private key together with its parent zpub can expose the parent's private key.

Cheetah arithmetic uses variable-time Python integer operations. Private operations belong in trusted offline wallet tools, not remote signing or key services. Python's allocator and garbage collector do not guarantee erasure of secret copies. zprv(), words(), and Seed.to_bytes() explicitly export spending authority. Diagnostic string/repr output is redacted; generic object serializers and private attributes are not secret-storage boundaries. Callers own logging, backups, storage, and access control.

Nouns, locks, notes and transaction reviews are immutable. Decoding has byte, logical-node and depth limits. Parsing does not establish signature or chain validity. Call verify_signatures() and validate_inputs() explicitly; obtain complete input records, canonical height, unspent status, and confirmations from a trusted chain-state source.

V1 condition trees and V0 migration inputs are supported. Fund inputs require an explicit authoritative identity and maturity policy. Migration parsing requires complete V0 records. Bridge payload codecs do not establish cross-chain finality or submit Ethereum transactions. This package is not a full consensus validator, chain client, or broadcaster. Applications supply correct height and fee contexts. Native NOCK uses nicks (2^16 per NOCK), distinct from Base ERC-20 units.

Tests use public Hoon, Rust and BIP39 fixtures. No independent cryptographic audit is claimed. Report vulnerabilities privately through GitHub private reporting when available or another established private channel to the maintainers. Never include real seeds, private extended keys, API credentials, or identifying wallet data in issues or reproductions.