The adapter connects to fx over the Agent Client Protocol (ACP) via @ai-sdk/harness-acp, and runs through the same HarnessAgent interface as Claude Code, Cline, Cursor, Codex, Deep Agents, Grok Build, OpenCode, and Pi.

Adding or swapping a coding agent is now a one-line dependency change, keeping one API for streaming, sessions, and tool calls across nine agents.

Vercel Adds fx to AI SDK Harness Layer via @ai-sdk/harness-fx Adapter

What shipped

Vercel added fx to the AI SDK harness layer with the official @ai-sdk/harness-fx adapter, announced in the changelog on August 31, 2026.

What changed

The adapter connects to fx over the Agent Client Protocol (ACP), built on @ai-sdk/harness-acp. You drop it into the same HarnessAgent interface as every other coding agent — no fx-specific integration code:

import { HarnessAgent } from '@ai-sdk/harness/agent';
import { fx } from '@ai-sdk/harness-fx';

const agent = new HarnessAgent({ harness: fx });

fx joins Claude Code, Cline, Codex, Cursor, Deep Agents, Grok Build, OpenCode, and Pi in the supported harness list.

Why a builder cares

Adding or swapping a coding agent in your app is now a one-line dependency change. The harness layer keeps one API for streaming, sessions, and tool calls across nine agents — fx included. No custom adapter to maintain, no second auth flow to wire up.

What shipped

What changed

Why a builder cares

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