I have a 2048-character password in the vault

[grb]

Maybe you’re confusing encryption with compression? Or not accounting for the effects of Base-64 encoding? Encryption definitely expands the size of the data.

See here:

Notes 10000 character max error with less than 10k char

The character limit applies to your data after it’s been encrypted. Our encryption algorithm increases the length of your data, so 9,000 characters unencrypted will exceed the 10,000 limit after encryption. It seems you can use 7,500 characters as an approximate limit for unencrypted text - see the recent discussion here: The field Notes exceeds the maximum encrypted value length of 10000 characters (when it is false) · Issue #1618 · bitwarden/browser · GitHub

 

You can test it for yourself using Bitwarden’s interactive cryptography tool: compare the length of the strings in the fields “Secret Value” (or “Decrypted”) and “Cipher String” at the bottom of the page.