Daily brief: SpaceX-Tesla merger talk, OCC rewards rule, Zcash upgrade

CoinDesk's daily briefing leads with Elon Musk saying SpaceX and Tesla are exploring a merger that would combine their more than 30,000 bitcoin holdings. No terms, structure or timeline have been disclosed.

Also in the brief:

• The OCC published its first final rule implementing the GENIUS Act, tightening how stablecoin issuers operate in the U.S. — existing rewards programs get no safe harbor as the rule takes effect January 18.
• Zcash is preparing for the NU7 upgrade, which cuts target block time from 75 to 25 seconds and could roughly triple transaction speed.