I use the SDK in my app and it works fine with plan mode. I don't deal with auth at all. I detect if the CLI is installed and it just reuses whatever auth the user has already setup. Works fine.
no, they banned use of the model without the CLI harness/SDK when using the subscription plans. Opencode was spoofing requests as if they were coming from claude code CLI, and controlling the agent loop / tool call totally internally. Anthropic wants subscription plans to use the CLI/SDK.
