ToolsFebruary 23, 2026via Vercel Blog
Safely inject credentials in HTTP headers with Vercel Sandbox
Why it matters
As AI agent workflows scale, credential exfiltration is becoming a vector for compromise. Vercel's header injection feature lets developers run untrusted code safely by enforcing credential isolation at the network layer, not the code layer—a critical shift for production AI deployments.
Key signals
- Feature: HTTP header injection for outbound requests from sandboxed code
- Credentials stored outside sandbox VM boundary to prevent exfiltration
- Designed specifically for AI agent workflows vulnerable to prompt injection
- Supports domain matching with exact and wildcard rules (e.g., *.github.com)
- Injected headers overwrite sandbox-set headers (full replacement, not additive)
- Can be updated on running sandbox without restart (multi-phase workflows)
- Available to Pro and Enterprise Vercel customers
- Works with all network policy configurations including open internet access
The hook
Vercel just closed a critical attack surface for AI agents. Credentials now live outside the sandbox—even if prompt injection succeeds, there's nothing to steal.
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 p…