Definition
Shadow Mode
Shadow mode runs the agent alongside humans before launch: both handle the same requests, but only the human's response reaches the customer. After a thousand shadow conversations you know where the agent matches, beats, or falls short of human quality, mapped by failure mode, before anyone is affected. The book calls it the most underused deployment technique because it costs compute, not customers.

Explained in
Chapter 13: Production AI: Deployment, Monitoring, and Evaluation
The reality of running AI agents. It's nothing like the demo.
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