OpenCode 2.0 launched on October 12 with background subagents and MCP Code Mode by default, while also breaking compatibility with V1 plugins and the older server API.
In the OpenCode tool docs, background: true lets a subagent return immediately instead of blocking the parent, then notify that parent when the child session finishes. Builders can continue work from the returned session ID, and the default nesting depth is one.
The same docs show a broader shift in tool use. The execute tool runs JavaScript in Code Mode so agents can call and combine tools from their catalog, including MCP-backed tools. Related MCP server docs say servers now default to Code Mode, with codemode: false available when teams want to expose tools directly instead.
That changes how integrations need to be designed because the runtime has no direct filesystem access, imports, timers, or fetch; it can only call registered tools. AICoder coverage ties those docs changes to the wider 2.0 release, including a shared local service, @opencode/sdk, and 80+ internal features rebuilt as hot-reloadable plugins.