base64-ng 0.12.0

base64-ng 0.12.0

base64-ng 0.12.0 is the stabilization rehearsal release before the planned 1.0 candidate.

Highlights

• Added migration-guide smoke tests covering strict standard, URL-safe no-pad, MIME/PEM, legacy whitespace, custom alphabets, stack buffers, secret buffers, and stream wrappers.
• Added MSRV/toolchain policy validation for Cargo metadata, rust-toolchain.toml, docs.rs metadata, CI install paths, target matrices, Kani policy, and release evidence tooling.
• Completed the final 0.12 dependency admission review: the published crate remains zero-runtime-dependency, with optional ecosystem integrations still deferred.
• Hardened custom alphabet decoding so bcrypt-style, crypt(3)-style, and caller-defined alphabets scan all 64 symbols before returning.
• Clarified that default strict decoders are not constant-time decoders; secret-bearing payloads should use the ct module when timing posture matters.
• Refined stream output-queue saturation errors so bounded internal queue exhaustion is not reported as malformed caller input.
• Expanded volatile wipe documentation with software-only zeroization limits and guidance for applications that already use zeroize.

Release Evidence

• Full release gate passed.
• Miri passed for no-default and all-features surfaces.
• Fuzz harness compile passed.
• Cross-target no-alloc and SIMD-reserved checks passed.
• SBOM generation passed.
• Reproducible package/build check passed.
• Kani remains a documented policy skip until its bundled compiler supports the pinned Rust 1.95 toolchain.