Notecosm collects nothing, sends nothing and has no account.
Your notes, the index Notecosm builds from them, the names of your groups and anything you ask it. All of it lives in the app's own container on this Mac and in the folder you chose. None of it is transmitted anywhere, and the app has no server to transmit it to.
Only in the folder you chose, and only what you write: a note you create, or an edit you save. It never writes to a file you did not edit, and refuses to save over a file that changed elsewhere while you were reading it.
Notecosm reads and answers using Apple's on-device models. The first time it needs them, macOS itself may download the model files from Apple — that is the system doing it, not Notecosm, and your notes are not part of that request. Everything Notecosm does with your notes happens on this Mac.
There is no telemetry, no crash reporting of our own, no identifier and no advertising. If macOS asks whether to share a crash report with developers, that is Apple's mechanism and your choice.