Vercel AI Updates: September 1, 2026

1. fx Coding Agent Joins the AI SDK Harness Layer

Vercel added support for fx, its lightweight open-source coding agent, to the AI SDK harness layer, which lets developers run multiple coding agents through a unified API without building separate integrations. Developers configure HarnessAgent with the official @ai-sdk/harness-fx adapter, which connects to fx over the Agent Client Protocol using @ai-sdk/harness-acp. fx joins an existing set of supported harnesses that includes Claude Code, Cline, Codex, Cursor, Deep Agents, Grok Build, OpenCode, and Pi. The approach lets teams add fx to their applications through standardized configuration rather than custom wiring. Source

2. AI Gateway Adds Per-User Spending Budgets

Vercel introduced per-user budgets on AI Gateway, letting teams set individual spending limits that are enforced across all API keys and app tokens tied to a member. Teams can define a default budget that applies to everyone, including new members, and override it with custom limits for specific individuals. Budgets reset monthly by default but also support daily, weekly, or continuous cycles, with optional email notifications at 50, 75, and 100 percent usage. Once a limit is reached, AI Gateway rejects new requests until the budget resets or is increased, and Bring Your Own Key traffic does not count toward user budgets. Source