Why does string.GetHashCode() return a different value every run in .NET?
Since .NET Core, string.GetHashCode() is seeded with a random per-process value (Marvin hashing), so the same string hashes differently in every process. Why the runtime does it, which types are affected (HashCode.Combine, ValueTuple, records with string members), how Dictionary<string, T> quietly avoids the cost, and how to get a stable hash with XxHash3 or FNV-1a, verified on .NET 10.0.10.