I used dagger for the sandbox in my personal harness. Docker also has a sandbox (microvm based) product now. Both obscure the credentials, but I do not think it eliminates them base64 encoding it (or some other transformation). It does step it from being visible if it is the same string, regardless where/how it is printed.

Service accounts / IAM / WIF / proxies, which remove credentials from the environment all together, are more advanced options.

I'm working on a custom "tool calling policy" guardrail agent. There are a number of models which have been trained to accept a policy document and user content, returning a truthy value for the harness to use during approval.