Some Bitcoin Cash or Dogecoin forks use unusual derivation paths. When you attempt to sign a transaction from such a fork, Trezor sees m/44'/145'/0' (unrecognized coin_type) and blocks it unless the coin’s app is explicitly installed.
Apostrophes ( ' ) denote — a one-way cryptographic step that prevents a child key from being reversed to find its parent.
Trezor’s firmware is open-source, and the community has proposed — where users could pre-approve specific custom paths in a config file. However, as of firmware 24.x, this feature remains unimplemented due to security concerns.
A compromised or malicious web wallet could ask your Trezor to sign a transaction using a non-standard path like m/44'/0'/999999'/0/0 — far outside normal account ranges. The goal: trick you into signing for an address whose private key the attacker knows (e.g., pre-generated from a weak seed). Trezor’s forbidden path check stops this attack cold.
If you encounter this error while performing a legitimate transaction, you can resolve it by adjusting your security settings or using specialized tools. 1. Change Safety Checks to "Prompt"
No legitimate DeFi protocol or exchange requires non-standard, non-hardened paths. If a dApp asks you to approve a “custom derivation path,” treat it as a red flag.