How to Let AI Agents Deploy to Servers Safely Without Sharing SSH Keys

AI coding agents can now handle most development tasks like branching, patching, and opening pull requests, but deploying changes to live servers has remained a security bottleneck. The core problem is that SSH private keys are bearer credentials — once shared with an agent's environment, there is no reliable way to confirm they weren't exposed in logs or transcripts. Security experts recommend a broker-based model where the agent never directly holds credentials, but instead requests actions through a custodian process that authenticates on its behalf. This approach enables explicit scope control, real-time human oversight, and simple access revocation without requiring credential rotation across multiple servers. Tools like Termalin are emerging to implement this model by pairing an SSH client with a built-in MCP server, making secure agent deployments more accessible without complex custom infrastructure.