Tool sessions and contributions
===============================

Overview
--------

A session owns runtime bindings and selections. A contribution supplies views,
actions, and status. The workspace owns documents, focus, and time.

Mental model
------------

::

   workspace (documents/focus/time)
       +-> Render Toy session (Scene/Post bindings)
       `-> ShaderToy session (one binding)

   view selector -> chooses visible layout only

Changing the primary view does not create or destroy either session. This boundary
supports future Lookdev, Render, ANARI, and studio tools without making one tool the
application owner.

See :doc:`../architecture/tool_contributions` and :doc:`../extending/adding_tool`.