SITUATION EXPLAINED: A Republican senator wants AI labs briefing the National Security Council. • His letter goes to Marco Rubio, cc'ing Hegseth, DNI Jay Clayton, National Cyber Director Sean Cairncross, and General Joshua Rudd at Cyber Command • The ask is recurring NSC roundtables with frontier developers, cybersecurity experts, national security officials, and critical infrastructure representatives • From the letter: recent developments have demonstrated the ability of advanced systems to…