diff --git a/.gitea/workflows/ci.yaml b/.gitea/workflows/ci.yaml
index fc901c4..f260604 100644
--- a/.gitea/workflows/ci.yaml
+++ b/.gitea/workflows/ci.yaml
@@ -26,10 +26,24 @@ jobs:
           # skipped for the same reason: our CMakeLists declares akerror::akerror
           # first and libakstdlib guards on if(NOT TARGET ...).
           submodules: true
+      # moreutils is load-bearing, not incidental: it supplies errno(1), which
+      # deps/libakerror/scripts/generrno.sh shells out to at build time to
+      # generate its errno name table and to stamp AKERR_LAST_ERRNO_VALUE into
+      # the generated akerror.h.
+      #
+      # Its absence does not fail the build, which is what made this expensive to
+      # find. The script prints "errno: command not found" twice, emits an empty
+      # akerr_init_errno() so no errno ever gets a name, and substitutes an empty
+      # AKERR_LAST_ERRNO_VALUE -- so every code in libakerror's reserved band
+      # collapses from (134 + n) to ( + n), i.e. to n. AKERR_OUTOFBOUNDS is
+      # (AKERR_LAST_ERRNO_VALUE + 2), so it becomes literally 2, and ERR(2)
+      # answers "Out Of Bounds Error" where ENOENT's "No such file or directory"
+      # belongs. That is the docs_examples failure at docs/15-error-codes.md:105
+      # that this job carried on every run since #2.
       - name: dependencies
         run: |
           sudo apt-get update -y
-          sudo apt-get install -y cmake gcc
+          sudo apt-get install -y cmake gcc moreutils
       - name: build
         run: |
           cmake -S . -B build
@@ -74,7 +88,7 @@ jobs:
       - name: dependencies
         run: |
           sudo apt-get update -y
-          sudo apt-get install -y cmake gcc
+          sudo apt-get install -y cmake gcc moreutils
       # The whole suite under ASan and UBSan, golden files included. This is the
       # gate libakstdlib's TODO.md section 1 calls its highest-value missing item
       # -- worth having here from the start, because this library is all fixed
@@ -98,7 +112,7 @@ jobs:
       - name: dependencies
         run: |
           sudo apt-get update -y
-          sudo apt-get install -y cmake gcc gcovr
+          sudo apt-get install -y cmake gcc gcovr moreutils
       # The gate is a ratchet, not a target: src/ sits at 94.6% of lines and
       # 98.6% of functions, so 90 fails on a real regression (a test deleted, or
       # new untested code added) without tripping over rounding.
@@ -172,11 +186,33 @@ jobs:
       # for deps/SDL_ttf/external/freetype, which the checkout above
       # deliberately does not clone. Installing two dev packages is much cheaper
       # than cloning freetype and harfbuzz.
+      #
+      # The X11 dev packages are the other half, and they are what this job has
+      # been dying on since run #2 -- it has never once been green. SDL_X11 and
+      # its nine sub-options default ON on Linux, and CheckX11() in
+      # deps/SDL/cmake/sdlchecks.cmake calls SDL_missing_dependency() -- a hard
+      # CMake error, not a downgrade -- for any one of them whose header is
+      # absent. The runner image carries libx11-dev (X11/XKBlib.h resolved) but
+      # none of the extension packages, so configuration stopped at the first of
+      # the nine: "Couldn't find dependency package for XCURSOR".
+      #
+      # Turning the missing ones OFF would also configure, and is the wrong
+      # answer: the point of this job is that an AKGL build is a real SDL
+      # program, and a real SDL program on Linux builds the X11 backend. The
+      # tests still run headless under SDL_VIDEODRIVER=dummy -- see the env block
+      # below -- so this buys a faithful build, not a display.
+      #
+      # The list is SDL's own, from deps/SDL/docs/README-linux.md, reduced to the
+      # X11 entries: the audio, Wayland, KMSDRM and Vulkan backends all degrade
+      # to "not found" and skip themselves rather than erroring, so they cost
+      # nothing to leave out. Nine packages, all in noble.
       - name: dependencies
         run: |
           sudo apt-get update -y
-          sudo apt-get install -y cmake gcc g++ pkg-config \
-            libfreetype-dev libharfbuzz-dev
+          sudo apt-get install -y cmake gcc g++ pkg-config moreutils \
+            libfreetype-dev libharfbuzz-dev \
+            libx11-dev libxext-dev libxcursor-dev libxi-dev libxfixes-dev \
+            libxrandr-dev libxss-dev libxtst-dev libxkbcommon-dev
       # The akgl-backed half: the text sink and the graphics, audio and input
       # backends, the standalone SDL frontend, and the two suites that drive
       # them against a real software renderer and read the pixels back.
@@ -256,7 +292,7 @@ jobs:
       - name: dependencies
         run: |
           sudo apt-get update -y
-          sudo apt-get install -y cmake gcc python3
+          sudo apt-get install -y cmake gcc python3 moreutils
       # Verify the tests actually catch bugs: break the library many ways and
       # confirm the suite fails. This matters more here than in an ordinary C
       # library, because the akerror control-flow macros expand at their call
diff --git a/.gitea/workflows/release.yaml b/.gitea/workflows/release.yaml
index dac235e..f2e6537 100644
--- a/.gitea/workflows/release.yaml
+++ b/.gitea/workflows/release.yaml
@@ -70,10 +70,14 @@ jobs:
           # corpus is part of what kills mutants and it is checked in now, so
           # that is libakerror and libakstdlib and nothing else.
           submodules: true
+      # moreutils for errno(1), which deps/libakerror's scripts/generrno.sh needs
+      # to generate its errno table. Without it the generated table is empty and
+      # every AKERR_* code collapses onto a low integer -- see the long note on
+      # ci.yaml's cmake_build job for what that breaks and how it presents.
       - name: dependencies
         run: |
           sudo apt-get update -y
-          sudo apt-get install -y cmake gcc python3
+          sudo apt-get install -y cmake gcc python3 moreutils
       # The whole akbasic-owned src/ tree. ci.yaml runs a two-file subset on every
       # push; this is the one that actually covers the interpreter.
       #