Why bother with a second one
You have a working CLI already. Learning a second one needs a real reason, so here are the real reasons.
You stop being trapped. If you only know one tool, then when that company raises prices, has an outage, changes something you relied on, or ships a bad update, you have no move. You wait. A builder who knows two tools always has a move: switch to the other one and keep working.
You get a second opinion. Tools have different strengths and different blind spots. When one CLI gets stuck on a problem, or gives you an answer that smells wrong, handing the same problem to the other one is one of the most useful debugging tricks you'll learn. Two tools disagreeing tells you something. Two tools agreeing is reassuring.
You can pick the better fit. They are not identical. For some kinds of work one will feel sharper than the other. You can't know which unless you've actually used both on real tasks.
This is not a loyalty thing
It's easy to treat tool choice like sports teams. Don't. There is no prize for being a Claude person or an OpenAI person, and the companies trade the lead back and forth constantly. The builder who treats these as interchangeable equipment, picks whichever fits today, and switches without drama, is in a stronger spot than the one with a favorite.
The cost of the second tool is low, which is the other half of the argument. Because Codex does the same job in the same shape as the Claude CLI, learning it is not starting over. It's mostly recognizing what you already know in slightly different clothes. The next step lists exactly how much carries over, and it's most of it.
Why bother with a second one
You have a working CLI already. Learning a second one needs a real reason, so here are the real reasons.
You stop being trapped. If you only know one tool, then when that company raises prices, has an outage, changes something you relied on, or ships a bad update, you have no move. You wait. A builder who knows two tools always has a move: switch to the other one and keep working.
You get a second opinion. Tools have different strengths and different blind spots. When one CLI gets stuck on a problem, or gives you an answer that smells wrong, handing the same problem to the other one is one of the most useful debugging tricks you'll learn. Two tools disagreeing tells you something. Two tools agreeing is reassuring.
You can pick the better fit. They are not identical. For some kinds of work one will feel sharper than the other. You can't know which unless you've actually used both on real tasks.
This is not a loyalty thing
It's easy to treat tool choice like sports teams. Don't. There is no prize for being a Claude person or an OpenAI person, and the companies trade the lead back and forth constantly. The builder who treats these as interchangeable equipment, picks whichever fits today, and switches without drama, is in a stronger spot than the one with a favorite.
The cost of the second tool is low, which is the other half of the argument. Because Codex does the same job in the same shape as the Claude CLI, learning it is not starting over. It's mostly recognizing what you already know in slightly different clothes. The next step lists exactly how much carries over, and it's most of it.