# AI SDK harness layer now supports native subscription authentication By Steven Van · 2026-09-14 Vercel's AI SDK harnesses can now authenticate via a coding agent's own subscription login, with no code changes required. Vercel's [AI SDK]() harness layer, which runs coding agents like Claude Code, Codex and Cursor behind a shared HarnessAgent interface, can now authenticate using a harness's own native subscription instead of only API keys. No code changes or new settings are needed. - The default auto mode, and the explicit direct mode, use a native subscription found on the host whenever explicit provider credentials or AI Gateway credentials aren't set; the ai-gateway mode never reads native subscriptions. - Credentials are resolved at the host boundary, the same way API keys are, with OAuth access tokens refreshed there as needed. - Where the sandbox supports it, the harness itself only sees placeholder credentials, and the real token is injected into outbound requests on the host. - Native subscription login is supported across the Claude Code, Cline, Codex, Cursor, fx, GitHub Copilot, Grok Build, OpenCode, and Pi [harness adapters](), wherever the underlying harness itself supports it. [![]()]() ![Vercel]() Vercel The platform for frontend developers — deploy, preview, and scale web apps and AI agents with zero config. [View Vercel →]() Sources [Original source]() [Read AI SDK harness layer now supports native subscription authentication on Creators Toolbox]() --- Canonical source: https://creatorstoolbox.com/blog/vercel-ai-sdk-harness-layer-now-supports-native-subscription-authentication