Architecture

Meta Harness maintains one portable workflow model and maps it onto actively supported coding-agent runtimes. The portable model is authoritative; runtime profiles and adapters are optional, removable execution material.

Architecture guides

• Portable contract — source of truth and rippability.
• Runtime capabilities — capability vocabulary and safe degradation.
• Role contract — runtime-neutral delegated-role fields.
• Handoffs — ephemeral coordination and durable artifacts.

Core invariant

A runtime adapter may lower a guarantee, but it must not silently claim a stronger guarantee than the runtime provides. When a required capability is unavailable, serialize the work or stop with a clear limitation.