Harmony 2.4 includes a lot of bug fixes and now supports arm64! Enjoy and consider supporting me on Patreon or become a GitHub sponsor!

Changelog

Added

• Full support for arm64 across all operating systems, including Apple Silicon

• Configurable error handler: A new API lets you register a global error handler that Harmony invokes whenever a patch throws an exception. This allows logging or suppressing errors centrally

• Extended CodeMatcher API: New methods—RemoveSearchForward, RemoveSearchBackward, RemoveUntilForward, RemoveUntilBackward and Do—make it easier to remove or transform instruction sequences via CodeMatcher

• Struct patching: [HarmonyPatch] attributes can now target methods defined in structs, not just classes

• Additional MethodType cases: Harmony’s API now covers more method kinds (e.g., async methods, property accessors or operators). This broadens the range of targets you can patch

• Simpler manual patch registration: The PatchClassProcessor no longer requires Harmony‑specific attributes when registering patches programmatically

Changed

• Patch serialization: PatchInfo now uses ToArray() instead of MemoryStream.GetBuffer to serialize patches, improving compatibility across .NET runtimes

• JSON serialization improvements: InnerMethod and patch classes gained custom System.Text.Json converters. Patch information now serializes round‑trip correctly and fields such as infixes were replaced with innerprefixes and innerpostfixes (new infix system)

• Exception handling: try/fault blocks emitted by Harmony are now compiled as try/catch/finally and won't fail to patch anymore

Fixed

• Correct index for local variables: CodeInstructionExtensions.LocalIndex now checks whether an operand is a LocalBuilder; it returns the correct LocalIndex instead of converting to int, preventing mis‑indexed local variables in transpilers

• Infix negative position bug: Matching of negative positions in infix patches was corrected; positions counting from the end now compute the index properly

• Argument validation for InnerMethod: Creating an InnerMethod now throws ArgumentNullException if method is null and ArgumentException if any position is zero, preventing silent errors

• Stream memory handling: A bug where patch generation incorrectly used MemoryStream.GetBuffer (which could include unused capacity) was fixed; ToArray is now used instead

• IL offset logging: IL offsets are logged again and reported accurately when debugging patched methods (commit referenced in release tag).

Removed

• HarmonyException serialization: HarmonyException is no longer marked [Serializable], so it can no longer be marshalled across AppDomains or remoted contexts

New Contributors

• @MSWS made their first contribution in https://github.com/pardeike/Harmony/pull/685
• @Nytra made their first contribution in https://github.com/pardeike/Harmony/pull/682

Full Changelog: https://github.com/pardeike/Harmony/compare/v2.3.6.0...v2.4.0.0