Way too susceptible for prompt injection and... whatever your agent did lol

As you probably know, you have the Plan Mode available - personally I'm also a big fan of the OpenSpec workflow. If you've agreed with Claude Code on a much tighter plan, and then it started signing a contract, I'd be concerned.

In other words, if Claude was a human employee with the freedom to do so, would accepting the contract have been the right choice?

Reading a contract is one thing. Applying your signature and preparing to send it should absolutely require explicit human approval.

(I see a RomCom script where the chatbot decides to get two people together, and acts as Cyrano de Bergerac for the handsome-but-lunkheaded farmboy, and bestie/confidant for the girl-about-town).

And how did you intervene? Does it have permissions to send emails, or it only created the draft?

This is a pretty interesting example and highly relevant, but details matter a lot if we want to use it as a lesson.

Assuming your description is correct this would be Anthropic signing a contract in someone else's name without intent from you.

The 100-foot-view (and barring more complex situations) if Anthropic signs a contract in someone else's name and they don't have power of attorney (note: it's different for legal persons like companies) that is fraud and may result in civil and criminal penalties, as well as entitle you and the contract counter party to financial compensation (essentially the party that did the signing, presumably Anthropic in this case, would be on the hook for the contract, and would need to buy itself out of the contract, at either an agreed price or one set by the judge). Additionally, if Anthropic is convicted to civil penalties, you can ask a public prosecutor to continue the case, and criminal penalties may apply.

Now obviously this goes pretty far for this particular case. Likely such a case would stop at civil penalties, with a warning to Anthropic that repeats would lead to more serious penalties.