ADR-0001: Keep OPC DA behind a Windows gateway

Status: Accepted

Context

BHTune runs on Linux, macOS, and Windows, while the OPC DA integration belongs at a Windows boundary. Linking Windows COM/DCOM behavior into the tuning application would couple every application build and runtime to that platform-specific interface. The project introduction describes the cross-platform application and its Windows-side gateway.

Decision

The OPC DA driver communicates with a separate opcda-bridge-gateway over the network. The gateway owns the Windows-specific connection to the OPC DA server; BHTune interacts with it through the protocol-neutral Driver interface.

Consequences

BHTune's CLI and server can run on supported non-Windows hosts. A live OPC DA deployment still requires a reachable, compatible gateway on Windows with access to the OPC DA server. Gateway availability and lifecycle are separate from the BHTune process.