You can. Anthropic documents it: the Agent SDK and claude -p work signed in with your Claude plan and draw from your normal subscription limits. https://support.claude.com/en/articles/15036540-use-the-clau...
We build a desktop app on top of the SDK, so I've spent a lot of time on that page.
Not true any more, read the note at the top of that page. They give you API credits but it's limited.