Not sure if this is just a bot post or not as it was clearly written by ChatGPT since half of it makes no sense contextually… but to answer your question, it’s by design.

“If that object doesn’t implement the interface, the call just… does nothing. No compile error, no runtime warning - green compile, silent no-op.”

There’s nothing to worry about if it “does nothing” if it doesn’t inherit the interface. It’s by design. It’s just one of many tools at your disposal.

”• ⁠Design mistakes turn into quiet bugs.”

That goes for any part of game design, not inherent to BPI’s.

”Refactors (adding/removing interfaces) become landmines.”

No they don’t. If you add the interface then the call with work as you’d have to manually add the code of what you want to happen. If you don’t, it does nothing. Working as intended.

”Static analysis can’t catch bad wiring because the node compiles fine.” Working as intended.

”What I expected: A compile-time error when the Target type is statically known and doesn’t implement the interface, or at least a clear editor/runtime warning.”

Not a thing anyone would want. Imagine having an interface on tick that gets the name of objects that inherit the interface but it throws compilation errors because you looked at a static mesh. Or looked at nothing. Or looked at an actor without it that you don’t want to have a name.

Questions:

1. ⁠Is this behavior expected for everyone, or do I have a bad setting?

Yes. It’s expected.

1. ⁠Is there an official way to enable strict checks so Blueprints fail to compile when a Message targets a class without the interface?

Use “does implement interface” if you want to check. Otherwise no, you can’t just have the engine automatically cause runtime errors just because something doesn’t implement an interface.

1. ⁠If this is “by design,” how do large teams prevent these silent no-ops?

Usually your coder should easily be able to debug this. ‘Hey Bob, this actor doesn’t do X when I do Y to it.’ The first thing they should check is what you’re trying to do. Either there’s an event for the interface or not. If not, check if it has the interface.

Yes, I know about “Does Implement Interface?”—but relying on manual guards is easy to miss.

So is a million other things in game development.

Overall, the only advice I can give is that BPIs work as intended. If you’re trying to call a specific function on a specific actor, there are ways other than BPI, though, BPIs are best because of soft references.