The HashiCorp Vault Agent is a service provided by the Vault binary that runs in the environment of an application, simplifying the integration process for applications with Vault. It supports automatic authentication (Auto-Auth) and manages the lifecycle of Vault tokens, including token renewal and re-authentication. The agent also provides templating capabilities to render secrets from Vault, eliminating the need for additional formatting and parsing. Additionally, it supports proxying and caching requests to Vault, reducing the load on Vault servers. For Kubernetes environments, the agent offers persistent caching across init and sidecar containers, reducing duplicate fetches of tokens and improving scalability. The Vault Agent simplifies the zero trust adoption journey by reducing the effort needed for application teams to integrate with Vault.