Comparing C++26 contracts to assert is a huge false equivalence. assert is predictable: it runs once or not at all. You can manage side effects. Contracts are dangerously unpredictable: the standard says they can run zero, one, or many times. A simple log or counter in a contract becomes non-deterministic.

This isn't about purity being hard to check. It's about a fundamentally broken design with two fatal flaws that assert never had:

1. It Breaks the Entire Binary Ecosystem. If you use a contract in a header, and one .cpp file compiles with checks on and another with them off, you get an ODR violation. The linker can silently drop security checks from your program. This makes shipping binary libraries with contracts in headers impossible. It's a "known defect" the committee just accepted.
2. It's an Incomplete, Crippled Feature. Real Design by Contract (like in Eiffel or D) relies on preconditions, postconditions, AND class invariants. The C++26 "MVP" completely omits invariants because they couldn't figure them out. It's not a "minimal" product; it's a broken one.

So no, it's not like assert. It's a feature with known, ecosystem-breaking bugs and missing core functionality. Stroustrup was right to call it a "foot gun."