HexBytes Library Version Silently Changes Signature Format, Breaking API Validation

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A subtle breaking change in the Python hexbytes library causes EIP-712 cryptographic signatures to be returned in different formats depending on the installed version, with no runtime error or warning raised. In version 0.3.x, the HexBytes.hex() method returned a 0x-prefixed string, but version 1.0.0 removed that override, causing the method to return bare hex without the prefix. This means server-side regex validation of signature headers can silently fail — the client code runs without error, but the server rejects the malformed value. The issue is compounded by a naive fix of prepending '0x' manually, which produces a double-prefixed string on older versions and gets rejected for incorrect length. A version-safe workaround using prefix normalization rather than concatenation is recommended to ensure consistent output across all affected hexbytes releases.

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