Was this Claude Code or Claude.ai or some other tool that used Claude under the hood?
Different harnesses have different search capabilities.
If I'm doing something that benefits from search I tend to switch to ChatGPT because I know it has a really good search feature available to it. I don't trust Claude's as much.
I used the Claude website and Mac desktop app for a relatively standard iOS SwiftUI project.
I used Claude Code with VS Code for some Godot stuff, and even there it sometimes gave outdated and outright made-up APIs (functions that seemed like they should exist but did not etc.)