"Are you mainlining it yet?" This is one of the key internal memes at @OpenAI, and a big part of the reason there's been a vibe shift toward Codex over the past few months. It asks: are you using the product all day, every day? Are you depending on it? Are you bringing all your taste to bear on whether this is something people actually want? Tara Seshan (@tarstarr) leads product for Codex and ChatGPT work at OpenAI (alongside her EM @ajambrosino). When I asked her what changed internally to…