Agents cannot start a top-level thread in another project #47

Outcome

An agent in Chromeria can start a new top-level thread in any project, with a task, provider instance, model, and effort, when the user asks for an independent session rather than a child.

Evidence (2026-09-27)

The user asked a planner to start a new Opus 5.5 xhigh planner for #46, "not as your child". The planner could not:

• spawn_thread creates a child of the calling thread in the calling thread's project.
• message_thread with scope: project reaches only threads in the caller's project.
• t3 app <path> opens an empty thread for a project in the desktop app, with no task, model, or effort, and needs the t3 CLI installed.

The only remaining route was a separate terminal session outside Chromeria, which the user does not want for work that should be visible in the app.

Acceptance criteria

• An MCP tool (or a scope on spawn_thread) starts a top-level thread in a named project with task, instance, model, effort, runtime mode, and title.
• The new thread appears in that project's sidebar, not in the caller's Agents panel.
• The caller can read and message it afterwards.

Non-goals

• Changing child-thread behavior.
• Cross-machine projects.

Blockers

None known. Check the thread-creation orchestration command for a project argument.

Proof

From a thread in one project, start a top-level thread in another project; it runs on the named model and effort and shows in that project's sidebar.