Bhagavad-Gita is simultaneously words of God, mentioned as an Upanishad, the 'Smriti-prasthana' and a part of the 'Itihasa-purana'.
The scriptures mention a hierarchy as Vedas and Upanishads > Smritis> Itihasa and Puranas.
Any Upanishad is a part of the Vedas, but Gita is NOT a part of any Veda. A smriti is a list of Do's and Don'ts but Gita is not such a Rule Book.
What us the exact position of Gita AS PER THE SCRIPTURES?
I am not interested in the personal opinions as discussed in Is Bhagavad Gita text Shruti or Smriti?