EnvVars are plaintext env vars set for every command in the sandbox while this rule is enabled. Use them for tools that refuse to run unless a credential env var is present (e.g. gh needs GH_TOKEN) even though this rule injects the real credential on the wire — set a dummy value here so the command starts. Explicit per-sandbox env_vars win over these, and provider-managed (AWS/GCP) vars win over both.
