diff --git a/README.md b/README.md
index e911f306..48e47f83 100644
--- a/README.md
+++ b/README.md
@@ -229,6 +229,10 @@ xo-umbrella2/
 +- Doxyfile.in                    doxygen config template; cmake will prepare Doxyfile in build dir
 +- _static/                       static inputs to sphinx
 |
++- doc
+|  +- glossary.rst                glossary for umbrella documentation
+|  \- install.rst                 umbrella install instructions
+|
 +- etc
 |  +- hostegl/                    sample video driver symlinks for WSL2
 |  \- hostubuntu/                 sample video driver symlinks for ubuntu
diff --git a/docs/install.rst b/docs/install.rst
index 117f7e08..f8ba26dd 100644
--- a/docs/install.rst
+++ b/docs/install.rst
@@ -6,9 +6,12 @@
 Source
 ======
 
-Source code for XO is on github `here`_
+Source code for XO available at:
+- github `here_github`_
+- forgejo `here_forgejo`_
 
-.. _here: https://github.com/rconybea/xo-umbrella2
+.. _here_github: https://github.com/rconybea/xo-umbrella2
+.. _here_forgejo: https://conybeare.us/git/roland/xo-umbrella2
 
 This repo contains source to all the XO libraries,  in the most convenient form for
 building + installing all XO libraries, or developing changes to XO itself.
@@ -32,6 +35,19 @@ XO dependencies (if you're using nix, it will assemble these for you)
 - eigen
 - catch2
 - pybind11
+- json5
+- jinja2  
+- replxx
+- libunwind
+
+XO imgui needs also:
+
+- vulkan
+- moltenvk (for darwin/osx)
+- SDL2
+- glew
+- libGL  
+- dejavu fonts
 
 XO documentation requires:
 
@@ -209,6 +225,20 @@ To run address sanitizer
     # phase 2
     $ cmake -B .build -S . -DCMAKE_INSTALL_PREFIX=$PREFIX -DCMAKE_BUILD_TYPE=asan
 
+
+Documentation Setup
+-------------------
+
+To build documentation:
+
+.. code-block::
+
+    # can reuse phase 1 cmake-macros-install
+
+	# phase 2
+	$ cmake -B .build -S . -DCMAKE_INSTALL_PREFIX=$PREFIX -DXO_ENABLE_DOCS=1
+	
+
 Sphinx Autobuild Setup
 ----------------------
 
diff --git a/docs/internals.rst b/docs/internals.rst
new file mode 100644
index 00000000..76fc66c0
--- /dev/null
+++ b/docs/internals.rst
@@ -0,0 +1,93 @@
+.. _internals:
+
+.. toctree
+   :maxdepth: 2
+
+Internals
+=========
+
+Monorepo
+--------
+
+The umbrella project ``xo-umbrella2`` provides a monorepo with all the XO projects.
+Each XO project appears as a top-level subdirectory (``xo-umbrella2/xo-arena``, ``xo-umbrella2/xo-flatstring``, ..).
+Each project also has it's own satellite repo, and can build/install independently of xo-umbrella2.
+
+In ``xo-umbrella2`` We use `git-subrepo`_ to coordinate the monorepo and each satellite repo.
+The subrepo feature rewrites commits in each direction.
+For example an ``xo-umbrella2`` commit touching ``xo-foo/src/foo/source.cpp`` will have a parallel ``xo-foo`` commit
+touching ``src/foo/source.cpp``.
+
+.. _git-subrepo: https://github.com/ingydotnet/git-subrepo
+
+There are some procedural differences between monorepo and satellite builds that are salient to cmake.
+We use the ``XO_SUBMODULE_BUILD`` to trigger monorepo-specific behavior.
+
+XO Cmake Macros
+---------------
+
+XO projects rely on a common set of cmake macros.
+Typical practice for a project ``foo`` using cmake would be to collect private macros in ``foo/cmake/``,
+then refer to them from ``foo/CMakeLists.txt``.
+
+XO uses a different policy, because we want to use the same set of cmake macros across all XO satellite projects,
+but we don't want to maintain separate copies. Instead we put XO cmake macros in their own repo
+``xo-cmake``.  Instead of maintaining a copy of the full XO cmake macro set, each satellite project contains
+its own copy of a common cmake bootstrap sequence. The bootstrap's job is to add the location of ``xo-cmake``
+to ``CMAKE_MODULE_PATH``.
+
+In a monorepo build, the XO cmake macros are available at ``xo-umbrella2/xo-cmake``.
+
+This gives us two ways to get XO cmake macros:
+
+- in-tree.
+  Build with ``CMAKE_MODULE_PATH=`` or ``CMAKE_MODULE_PATH=prefix`` (literal ``prefix`` here)
+
+- installed.
+  Build with ``CMAKE_MODULE_PATH=$PREFIX/share/cmake`` where PREFIX is installed location of ``xo-cmake``.
+
+The bootstrap sequence needs to know whether it's runing on behalf of an XO monorepo or an indepndent satellite
+project.  We use cmake variable ``XO_SUBMODULE_BUILD`` to signal this.
+
+Documentation
+-------------
+
+In XO projects we use a combination of doxygen, sphinx and breathe to assemble documentation.
+An individual satellite project will have a sphinx entry point ``xo-foo/doc/conf.py``,
+targeting building a documentation tree for ``xo-foo`` alone.
+
+In a monorepo build we want to generate a consolidated documentation tree.
+This relies on some monorepo-only scaffolding:
+
+- xo-umbrella2/conf.py.
+  Sphinx configuration file
+
+- xo-umbrella2/Doxyfile.in
+  CMake template for ``$BUILDDIR/Doxyfile``
+
+- index.rst.
+  Top-level sphinx documentation page.
+  This page points to ``xo-foo/docs/index`` for each satellite ``xo-foo`` that provides
+  sphinx documentation.
+
+- docs/.
+  Additional umbrella-only sphinx documentation
+  
+Continuous Integration
+----------------------
+
+The primary CI pipeline runs on forgejo, see ``.forgejo/workflows/ci.yaml``.
+The forgejo setup uses a custom runner so that the nix store is shared between builds.
+
+There's also a github pipeline, see ``.github/workflows/main-stock-ubuntu.yml``.
+In practice that's proved more awkward to maintain, since it installs 3rd party dependencies
+on top of stock ubuntu.
+
+
+
+
+
+
+
+
+