| ChunkCountExceededError | A chunk count derived from a plaintext or ciphertext length exceeds MAX_CHUNK_COUNT. |
| CriticalHeaderError | A crit (label 2) listing was rejected — wrong bucket, wrong shape, or naming a label this profile does not understand or does not actually carry. |
| EnvelopeError | Base class for every error raised by this package. |
| InvalidChunkSizeError | chunkSize is not an integer within [MIN_CHUNK_SIZE, MAX_CHUNK_SIZE]. |
| InvalidCiphertextLengthError | ciphertextLength is not a valid ciphertext length for the given chunk size. |
| InvalidNonceError | A base nonce, chunk index, or last-chunk flag is not valid for per-chunk nonce derivation. |
| InvalidPlaintextLengthError | plaintextLength is not a non-negative safe integer, or the ciphertext length it implies is unrepresentable or past the encoded-object limit. |
| MalformedEnvelopeError | The envelope, or a value destined for one, does not match this package’s wire profile. Raised on both paths: by encode when a caller’s input would produce bytes this package could not read back, and by decode on anything the profile forbids. |
| UnsupportedSchemeError | The protected header’s alg is not one of the schemes this package implements (ALG_AES_256_GCM or ALG_CHUNKED_AES_256_GCM_STREAM). |
