I add here a suggestion for the tests of the ErrorHandler. It would be great to have a union that collects all the classes of errors like
LayerError, TypeError, TensorMathError and so on, and in the tests iterate over that class so to ensure that all the errors of each class have a errorDetails() output.

Around the code there are some error.ErrorSomething. It would be great to use only the error types of errorHandler.zig.
More in general some errors are overused and sometimes they give wrong information about the real error.
For example:
if (out_channels != weight_out_channels) { std.debug.print("Error: Mismatched output channels: dValues {d}, weights {d}\n", .{ out_channels, weight_out_channels }); return TensorMathError.InputTensorsWrongShape; }
inside tensor_math.zig.
In this case the error InputTensorsWrongShape is not the right one, It could put you on the wrong path while debugging.