Intel / article

Use ACP-compatible harnesses with the AI SDK harness layer

Source: vercel.com
Author: Felix Arntz
Date: Published Aug 13, 2026

Context

Vercel's AI SDK can connect to additional coding- runtimes through a shared protocol. Its ACP adapter translates between the SDK's HarnessAgent interface and a runtime's Agent Client Protocol package. Developers still configure the package and the mapping between interfaces, but can reuse the protocol integration instead of building every connection separately.

This is most useful when a runtime supports ACP but lacks a direct SDK adapter. The announcement recommends direct adapters where they expose the runtime's behavior more faithfully.

Terms in this piece · Glossary

AI agent — An AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.
agent harness — The scaffolding around a model that turns it into a working agent — the loop, the tools it can call, and the rules for when to stop.

Key quotes

“The AI SDK harness layer now supports any Agent Client Protocol (ACP)-compatible harness with HarnessAgent through the new @ai-sdk/harness-acp package.”
Felix Arntz

“Previously, every harness adapter wrapped one specific runtime (Claude Code, Codex, Pi, Deep Agents, OpenCode). @ai-sdk/harness-acp wraps the protocol instead.”
Felix Arntz

“ACP is an abstraction over coding harnesses, but the AI SDK harness layer stays deliberately decoupled from it. Not every harness supports ACP, and for some, ACP limits or changes how well they expose their internal behaviors, so a direct adapter can produce a tighter integration.”
Felix Arntz

“For Claude Code and Codex, prefer the direct @ai-sdk/harness-claude-code and @ai-sdk/harness-codex adapters over an ACP-based implementation; reach for @ai-sdk/harness-acp when a harness has no direct adapter but ships an ACP-compatible package.”
Felix Arntz

Read the source vercel.com