diff --git a/packages/codev-sandbox/README.md b/packages/codev-sandbox/README.md
index 830417cce5..b62b9f1cf3 100644
--- a/packages/codev-sandbox/README.md
+++ b/packages/codev-sandbox/README.md
@@ -124,7 +124,10 @@ containerized (any machine with Docker):
   the optional office layer: `image/office/install-office.sh` translates the
   codev-office setup script system-wide — pandoc + LibreOffice + fonts from
   Debian, .NET 8 SDK at `/opt/dotnet`, the pinned Python package set, the
-  bundle's pure-JS node-module trees on `NODE_PATH`, and the office skills at
+  bundle's node-module trees (pure-JS ones verbatim; sharp's native binary
+  re-resolved for the guest arch) reachable three ways — `NODE_PATH`,
+  `~/.node_modules` via skel, and `/usr/local/lib/node`, the one that needs
+  neither the environment nor `$HOME` — and the office skills at
   `/opt/codev-skills` with an `/etc/skel` codev.json pointing at them. Fresh
   sandbox homes get skel (vz at image build; bwrap seeded by the boot script),
   and images declare extra env in `/etc/codev-guest.env`.
diff --git a/packages/codev-sandbox/image/office/install-office.sh b/packages/codev-sandbox/image/office/install-office.sh
index d792b57608..e20c05b646 100644
--- a/packages/codev-sandbox/image/office/install-office.sh
+++ b/packages/codev-sandbox/image/office/install-office.sh
@@ -173,10 +173,14 @@ python3 -c 'import pandas, openpyxl, markitdown, reportlab, pypdf, matplotlib, d
 
 # --- JS module trees ---
 # Merged into one tree the way the setup script merges them under
-# ~/.codev-office. Reached two ways on purpose: NODE_PATH in the guest env
-# (which the server exports, so its shell tool inherits it) and an
-# /etc/skel/.node_modules symlink — one of Node's global require() fallback
-# folders — so require() also resolves from a plain shell in any directory.
+# ~/.codev-office. Reached three ways on purpose, because each of the first two
+# has a way to not be there: NODE_PATH in the guest env (the server exports it,
+# so its shell tool inherits it — unless something along the way replaces the
+# environment), an /etc/skel/.node_modules symlink (one of Node's global
+# require() fallback folders — but only for a process whose HOME is a home the
+# skel was copied into, which a root shell's /root is not), and
+# /usr/local/lib/node below, which is the same fallback list without either
+# dependency.
 mkdir -p "$OFFICE_HOME/node_modules"
 staging="$(mktemp -d)"
 for mod_zip in "$BUNDLE"/*-node-modules.zip; do
@@ -188,6 +192,73 @@ done
 rm -rf "$staging"
 mkdir -p /etc/skel
 ln -sfn "$OFFICE_HOME/node_modules" /etc/skel/.node_modules
+# $PREFIX/lib/node — the entry in Node's global fallback list that depends on
+# neither the environment nor $HOME. Node derives it from its own binary
+# (execPath/../../lib/node, so /usr/local/lib/node for the tarball install in
+# the Dockerfile), which means require("pptxgenjs") resolves for any user, from
+# any directory, with NODE_PATH unset. That is worth having even when the other
+# two work: an agent that cannot require() the module goes looking for it, and
+# `npm install -g pptxgenjs` cannot fix it either (npm -g installs into
+# $PREFIX/lib/node_modules, which is NOT on require()'s search path) in a guest
+# with no route off loopback.
+#
+# The fallback list is consulted only after the full node_modules walk-up, so a
+# workspace project's own dependencies always win. The one behaviour this does
+# change: a project MISSING a dependency the office tree happens to carry
+# (react, react-dom) resolves it from here instead of failing.
+mkdir -p /usr/local/lib
+ln -sfn "$OFFICE_HOME/node_modules" /usr/local/lib/node
+
+# Those trees are copied verbatim because they are pure JS — one build serves
+# every arch. sharp (the pptx skill's react-icons -> SVG -> PNG path) is the
+# exception: it loads a prebuilt libvips binary from an @img/sharp-<os>-<cpu>
+# optional dependency, and the bundle carries the linux-x64 one. On arm64 that
+# binary cannot load, so re-resolve it here exactly as every other
+# arch-specific component in this file is handled — same version, arch-correct
+# build. dpkg's arm64 is npm's arm64, and the Dockerfile refuses any arch that
+# is not amd64 or arm64, so ARCH doubles as the --cpu value on this branch.
+#
+# Resolved in a scratch dir and copied in, NOT installed into the shared tree:
+# `npm install` in a node_modules dir with no package.json reifies the tree
+# from scratch and drops everything it cannot account for, which would take
+# PptxGenJS and Playwright with it.
+sharp_pkg="$OFFICE_HOME/node_modules/sharp/package.json"
+if [ "$ARCH" != "amd64" ] && [ -f "$sharp_pkg" ]; then
+  SHARP_VERSION="$(python3 -c 'import json,sys; print(json.load(open(sys.argv[1]))["version"])' "$sharp_pkg")"
+  sharp_scratch="$(mktemp -d)"
+  ( cd "$sharp_scratch" && npm init -y >/dev/null \
+      && npm install --no-audit --no-fund --os=linux --cpu="$ARCH" --libc=glibc "sharp@$SHARP_VERSION" >/dev/null )
+  # A silently-ignored --cpu yields a tree that looks right and throws only in
+  # the guest, so require the binary package by name rather than trusting npm.
+  [ -d "$sharp_scratch/node_modules/@img/sharp-linux-$ARCH" ] \
+    || { echo "no @img/sharp-linux-$ARCH for sharp $SHARP_VERSION (npm >= 10 needed for --cpu)" >&2; exit 1; }
+  rm -rf "$OFFICE_HOME/node_modules/@img"
+  cp -R "$sharp_scratch/node_modules/." "$OFFICE_HOME/node_modules/"
+  rm -rf "$sharp_scratch"
+fi
+
+# Use the trees rather than just checking they unpacked, the way the LibreOffice
+# step converts a document instead of resolving a binary. They arrive by a
+# wildcard glob, so a zip that failed to unpack, or a native binary built for
+# the other arch, is otherwise invisible until an agent tries to build a deck.
+#
+# Deliberately run with NODE_PATH unset, from a directory with no relationship
+# to the tree: that is the guest's worst case (a shell whose environment did not
+# survive, in the user's workspace), so it is what the image should be proven
+# against. Passing here means the /usr/local/lib/node fallback carries it alone.
+office_node() { ( cd / && env -u NODE_PATH -u NODE_OPTIONS node -e "$1" ); }
+if [ -d "$OFFICE_HOME/node_modules/pptxgenjs" ]; then
+  office_node 'const P=require("pptxgenjs");const p=new P();p.layout="LAYOUT_16x9";p.addSlide().addText("image check",{x:1,y:1,w:8,h:1,fontSize:24});p.writeFile({fileName:"/tmp/office-check.pptx"}).then(function(){process.exit(0);}).catch(function(e){console.error(e);process.exit(1);});'
+  python3 -m markitdown /tmp/office-check.pptx >/dev/null
+  rm -f /tmp/office-check.pptx
+fi
+# Icons are optional per the skill's own docs, so this warns like the playwright
+# steps below rather than failing the build: without them decks still come out
+# of shapes, text and charts.
+if [ -d "$OFFICE_HOME/node_modules/sharp" ]; then
+  office_node 'const React=require("react"),RDS=require("react-dom/server"),sharp=require("sharp");const {FaCheckCircle}=require("react-icons/fa");const svg=RDS.renderToStaticMarkup(React.createElement(FaCheckCircle,{color:"#000000",size:"64"}));sharp(Buffer.from(svg)).png().toBuffer().then(function(b){process.exit(b.length?0:1);}).catch(function(e){console.error(e);process.exit(1);});' \
+    || echo "warn: the pptx icon toolchain is unusable; react-icons artwork will be unavailable" >&2
+fi
 
 # --- Chromium for Playwright (pdf cover rendering) ---
 # Playwright launches the browser build matching its own version, so the