https://vercel.com/changelog/safely-inject-credentials-in-http-headers-with-vercel-sandbox (opens in new tab)

# Safely inject credentials in HTTP headers with Vercel Sandbox **Published:** February 23, 2026 | **Authors:** Valerian Roche, Rob Herley --- Vercel Sandbox can now automatically inject HTTP headers into outbound requests from sandboxed code. This keeps API keys and tokens safely outside the sandbox VM boundary, so apps running inside the sandbox can call authenticated services without ever accessing the credentials. Header injection is configured as part of the network policy using `tra...