One adapter now covers any ACP-compatible coding harness in the AI SDK

Vercel shipped @ai-sdk/harness-acp on 13 August 2026, a meta-adapter that lets the AI SDK harness layer drive any harness speaking the Agent Client Protocol by passing the package to createACP, instead of writing a bespoke adapter per runtime. Codex, Claude Code, Pi, Deep Agents and OpenCode are named as ACP-compatible. Vercel still recommends the direct adapters where they exist, warning that "not every harness supports ACP, and for some, ACP limits or changes how well they expose their internal behaviors".

What it means Swapping the coding harness under an agent stops being a rewrite and becomes a config change, which is the practical hedge against betting a product on one vendor’s runtime. The caveat is worth reading: going through the protocol can hide behaviour a direct adapter would expose.