diff --git a/scripts/install-session.sh b/scripts/install-session.sh
index 5c534c9..47316fc 100644
--- a/scripts/install-session.sh
+++ b/scripts/install-session.sh
@@ -1,165 +1,5 @@
 #!/usr/bin/env bash
-# Install already-built binaries. Run from any directory with sudo.
+# Apply a prepared bundle, roll back, or recover an interrupted installation.
 set -euo pipefail
-
-session_entry_matches() {
-    # App-icon metadata can change between managed releases. All other fields,
-    # especially Exec/TryExec, must still match before replacing an entry.
-    cmp -s -- <(sed '/^Icon=/d' "$1") <(sed '/^Icon=/d' "$2")
-}
-
-managed_file_matches() {
-    local relative=$1 destination=$2
-    cmp -s -- "$repo_dir/packaging/$relative" "$destination" ||
-        cmp -s -- "$install_root/current/installer-files/$relative" "$destination"
-}
-
 repo_dir=$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")/.." && pwd)
-release_id=${1:?usage: install-session.sh RELEASE_ID [--replace-portal-config]}
-replace_portal_config=false
-if [[ ${2:-} == --replace-portal-config && $# == 2 ]]; then
-    replace_portal_config=true
-elif (($# > 1)); then
-    echo 'usage: install-session.sh RELEASE_ID [--replace-portal-config]' >&2
-    exit 2
-fi
-[[ $release_id =~ ^[a-zA-Z0-9][a-zA-Z0-9._-]*$ ]] || exit 2
-[[ $EUID == 0 ]] || { echo 'Run this installer with sudo.' >&2; exit 1; }
-
-install_root=/usr/local/lib/ferese
-release_dir=$install_root/releases/$release_id
-session_entry=/usr/share/wayland-sessions/ferese.desktop
-[[ ! -e $release_dir ]] || { echo "Release already exists: $release_dir" >&2; exit 1; }
-
-# Refuse to overwrite unrelated installations.
-for name in ferese ferese-shell ferese-settings feresectl ferese-session ferese-lock ferese-polkit-agent ferese-screenshot xdg-desktop-portal-ferese ferese-record; do
-    link=/usr/local/bin/$name
-    if [[ -e $link || -L $link ]]; then
-        [[ -L $link && $(readlink -- "$link") == "$install_root/current/$name" ]] || {
-            echo "Unmanaged path exists: $link" >&2; exit 1;
-        }
-    fi
-done
-for link in current previous; do
-    if [[ -e $install_root/$link || -L $install_root/$link ]]; then
-        [[ -L $install_root/$link && $(readlink -- "$install_root/$link") == releases/* ]] || {
-            echo "Unmanaged path exists: $install_root/$link" >&2; exit 1;
-        }
-    fi
-done
-if [[ -e $session_entry ]]; then
-    session_entry_matches "$repo_dir/packaging/ferese.desktop" "$session_entry" || {
-        echo "Different session entry exists: $session_entry" >&2; exit 1;
-    }
-fi
-for name in ferese ferese-shell ferese-settings feresectl ferese-lock ferese-polkit-agent xdg-desktop-portal-ferese ferese-record; do
-    [[ -x $repo_dir/target/release/$name ]] || { echo "Missing release binary: $name" >&2; exit 1; }
-done
-"$repo_dir/target/release/ferese-polkit-agent" --check
-for name in ferese.png ferese.svg; do
-    [[ -f $repo_dir/assets/wallpapers/$name ]] || { echo "Missing wallpaper asset: $name" >&2; exit 1; }
-done
-# Preserve administrator-supplied policies. New installs use the distro's
-# authentication and account stacks, never a permissive fallback.
-pam_policy=generic
-if [[ -f /etc/pam.d/system-auth ]]; then
-    pam_policy=fedora
-elif [[ -f /etc/pam.d/common-auth && -f /etc/pam.d/common-account ]]; then
-    pam_policy=debian
-elif [[ ! -f /etc/pam.d/login && ! -f /etc/pam.d/ferese-lock ]]; then
-    echo 'No supported PAM stack found; install /etc/pam.d/ferese-lock first.' >&2
-    exit 1
-fi
-
-# These files are owned by Ferese; preserve unrelated administrator configuration.
-for entry in \
-    'ferese.portal:portals/ferese.portal' \
-    'ferese-portals.conf:ferese-portals.conf'; do
-    source=${entry%%:*}
-    destination=/usr/share/xdg-desktop-portal/${entry#*:}
-    if [[ -e $destination ]] && ! managed_file_matches "portal/$source" "$destination" && ! $replace_portal_config; then
-        echo "Unmanaged portal configuration exists: $destination" >&2
-        echo 'Use --replace-portal-config to back up and replace Ferese portal configuration.' >&2
-        exit 1
-    fi
-done
-service=/usr/local/share/dbus-1/services/org.freedesktop.impl.portal.desktop.ferese.service
-if [[ -e $service ]] && ! managed_file_matches "portal/$(basename "$service")" "$service"; then
-    # Upgrade the exact activation file shipped before systemd supervision.
-    if ! cmp -s <(printf '%s\n' '[D-BUS Service]' \
-        'Name=org.freedesktop.impl.portal.desktop.ferese' \
-        'Exec=/usr/local/lib/ferese/current/xdg-desktop-portal-ferese') "$service"; then
-        echo "Unmanaged portal service exists: $service" >&2; exit 1
-    fi
-fi
-
-portal_unit=/usr/local/lib/systemd/user/xdg-desktop-portal-ferese.service
-if [[ -e $portal_unit ]] && ! managed_file_matches "systemd/xdg-desktop-portal-ferese.service" "$portal_unit"; then
-    echo "Unmanaged portal unit exists: $portal_unit" >&2; exit 1
-fi
-
-session_target=/usr/local/lib/systemd/user/ferese-session.target
-if [[ -e $session_target ]] && ! managed_file_matches "systemd/ferese-session.target" "$session_target"; then
-    echo "Unmanaged session target exists: $session_target" >&2; exit 1
-fi
-
-desktop-file-validate "$repo_dir/packaging/ferese.desktop"
-desktop-file-validate "$repo_dir/packaging/dev.ferese.Settings.desktop"
-
-install -d -m 0755 -- "$release_dir" /usr/local/bin /usr/share/wayland-sessions
-for relative in portals/ferese.portal ferese-portals.conf; do
-    destination=/usr/share/xdg-desktop-portal/$relative
-    if [[ -e $destination ]]; then
-        install -D -m 0644 -- "$destination" "$release_dir/portal-config.previous/$relative"
-    fi
-done
-for relative in \
-    portal/ferese.portal \
-    portal/ferese-portals.conf \
-    portal/org.freedesktop.impl.portal.desktop.ferese.service \
-    systemd/xdg-desktop-portal-ferese.service \
-    systemd/ferese-session.target; do
-    install -D -m 0644 -- "$repo_dir/packaging/$relative" "$release_dir/installer-files/$relative"
-done
-if [[ -e $session_entry ]]; then
-    install -m 0644 -- "$session_entry" "$release_dir/session.previous.desktop"
-fi
-for name in ferese ferese-shell ferese-settings feresectl ferese-lock ferese-polkit-agent xdg-desktop-portal-ferese ferese-record; do
-    install -m 0755 -- "$repo_dir/target/release/$name" "$release_dir/$name"
-done
-install -m 0755 -- "$repo_dir/packaging/ferese-session" "$release_dir/ferese-session"
-install -m 0755 -- "$repo_dir/packaging/ferese-session-shell" "$release_dir/ferese-session-shell"
-install -D -m 0644 -- "$repo_dir/packaging/systemd/ferese-session.target" "$session_target"
-install -D -m 0644 -- "$repo_dir/packaging/systemd/xdg-desktop-portal-ferese.service" "$portal_unit"
-install -m 0755 -- "$repo_dir/packaging/ferese-screenshot" "$release_dir/ferese-screenshot"
-install -m 0644 -- "$repo_dir/packaging/config.kdl" "$release_dir/config.example.kdl"
-install -D -m 0644 -- "$repo_dir/assets/fonts/Comfortaa-LICENSE.txt" "$release_dir/licenses/Comfortaa-LICENSE.txt"
-install -D -m 0644 -- "$repo_dir/assets/fonts/Cantarell-LICENSE.txt" "$release_dir/licenses/Cantarell-LICENSE.txt"
-for license in "$repo_dir"/assets/themes/licenses/*.txt; do
-    install -D -m 0644 -- "$license" "$release_dir/licenses/theme-$(basename -- "$license")"
-done
-install -d -m 0755 -- "$release_dir/wallpapers"
-install -m 0644 -- "$repo_dir/assets/wallpapers/ferese.png" "$release_dir/wallpapers/ferese.png"
-install -m 0644 -- "$repo_dir/assets/wallpapers/ferese.svg" "$release_dir/wallpapers/ferese.svg"
-
-if [[ ! -e /etc/pam.d/ferese-lock ]]; then
-    install -D -m 0644 -- "$repo_dir/packaging/pam.d/ferese-lock.$pam_policy" /etc/pam.d/ferese-lock
-fi
-
-if [[ -L $install_root/current ]]; then
-    ln -sfn -- "$(readlink -- "$install_root/current")" "$install_root/previous"
-fi
-ln -s -- "releases/$release_id" "$install_root/current-$release_id"
-mv -Tf -- "$install_root/current-$release_id" "$install_root/current"
-for name in ferese ferese-shell ferese-settings feresectl ferese-session ferese-lock ferese-polkit-agent ferese-screenshot xdg-desktop-portal-ferese ferese-record; do
-    ln -sfn -- "$install_root/current/$name" "/usr/local/bin/$name"
-done
-install -m 0644 -- "$repo_dir/packaging/ferese.desktop" "$session_entry"
-install -D -m 0644 -- "$repo_dir/packaging/dev.ferese.Settings.desktop" /usr/local/share/applications/dev.ferese.Settings.desktop
-install -D -m 0644 -- "$repo_dir/packaging/icons/ferese.svg" /usr/local/share/icons/hicolor/scalable/apps/dev.ferese.Settings.svg
-install -D -m 0644 -- "$repo_dir/packaging/icons/ferese.svg" /usr/local/share/icons/hicolor/scalable/apps/ferese.svg
-install -D -m 0644 -- "$repo_dir/packaging/portal/ferese.portal" /usr/share/xdg-desktop-portal/portals/ferese.portal
-install -D -m 0644 -- "$repo_dir/packaging/portal/ferese-portals.conf" /usr/share/xdg-desktop-portal/ferese-portals.conf
-install -D -m 0644 -- "$repo_dir/packaging/portal/org.freedesktop.impl.portal.desktop.ferese.service" "$service"
-if command -v update-desktop-database >/dev/null; then update-desktop-database /usr/local/share/applications || true; fi
-echo "Installed Ferese $release_id. Select Ferese at your login screen, or run /usr/local/bin/ferese-session from a local TTY."
+exec python3 "$repo_dir/scripts/installer/install.py" "$@"
diff --git a/scripts/install.sh b/scripts/install.sh
index 710c0a4..7093918 100755
--- a/scripts/install.sh
+++ b/scripts/install.sh
@@ -1,64 +1,48 @@
 #!/usr/bin/env bash
-# Build as the invoking user; elevate only the versioned system installation.
+# Build and prepare a complete release as the user; elevate only installation.
 set -euo pipefail
 
 usage() {
     cat <<'EOF'
 Usage: scripts/install.sh [options]
 
-Build and install Ferese's compositor, shell, CLI, and login-screen session.
-Run from any directory as your normal user. Existing user config is preserved.
+Build, bundle and install Ferese. Run as your normal user.
 
-  --release-id ID  Name the installed release (default: UTC timestamp + PID)
-  --skip-build     Install existing target/release binaries
-  --replace-portal-config  Back up and replace existing Ferese portal configuration
-  --offline        Build using only cached Cargo dependencies
-  --resize-metrics Build with resize-barrier measurements (reported on exit)
-  --dry-run        Print commands without building or installing
-  -h, --help       Show this help
+  --release-id ID          Release name (default: UTC timestamp + PID)
+  --bundle PATH            Install an existing verified bundle; do not build
+  --bundle-only PATH       Build a bundle at PATH without installing
+  --replace-portal-config  Back up and replace modified Ferese portal config
+  --offline               Build using cached Cargo dependencies
+  --resize-metrics        Build with resize-barrier measurements
+  --dry-run               Show commands without building or installing
+  -h, --help              Show this help
 
-The previous release remains available for rollback. Administrator
-authentication is requested only after a successful build.
+Recovery and rollback: scripts/install-session.sh --help
+Repeat user setup: python3 scripts/installer/install.py user-setup
 EOF
 }
 
-check_user_portal_override() {
-    local override=$1 user_home=$2
-    [[ -f $override ]] || return 0
-    if ! cmp -s -- <(printf '%s\n' '[Service]' 'ExecStart=' \
-        "ExecStart=$user_home/.local/libexec/ferese/xdg-desktop-portal-ferese") "$override"; then
-        echo "Custom portal override takes precedence over the installation: $override" >&2
-        echo 'Update its ExecStart to /usr/local/lib/ferese/current/xdg-desktop-portal-ferese before installing.' >&2
-        return 1
-    fi
-}
-
-backup_user_portal_override() {
-    local override=$1 user_home=$2 release=$3
-    [[ -f $override ]] || return 0
-    check_user_portal_override "$override" "$user_home" || return 1
-    local backup="$override.before-$release"
-    [[ ! -e $backup ]] || { echo "Portal override backup already exists: $backup" >&2; return 1; }
-    mv -- "$override" "$backup"
-    echo "Backed up old development portal override: $backup"
-}
-
 fail() { echo "ferese installer: $*" >&2; exit 1; }
 repo_dir=$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")/.." && pwd)
+helper=$repo_dir/scripts/installer/install.py
 release_id="$(date -u +%Y%m%d-%H%M%S)-$$"
-skip_build=false
+release_set=false
+bundle_path=
+bundle_only=
 replace_portal_config=false
 offline=false
 resize_metrics=false
 dry_run=false
 while (($#)); do
     case $1 in
-        --release-id)
-            (($# >= 2)) || fail '--release-id requires a value'
-            release_id=$2
-            shift 2
-            ;;
-        --skip-build) skip_build=true; shift ;;
+        --release-id|--bundle|--bundle-only)
+            (($# >= 2)) && [[ -n $2 && $2 != --* ]] || fail "$1 requires a value"
+            case $1 in
+                --release-id) release_id=$2; release_set=true ;;
+                --bundle) bundle_path=$2 ;;
+                --bundle-only) bundle_only=$2 ;;
+            esac
+            shift 2 ;;
         --replace-portal-config) replace_portal_config=true; shift ;;
         --offline) offline=true; shift ;;
         --resize-metrics) resize_metrics=true; shift ;;
@@ -68,56 +52,77 @@ while (($#)); do
     esac
 done
 [[ $release_id =~ ^[a-zA-Z0-9][a-zA-Z0-9._-]*$ ]] || fail 'invalid release ID'
-if $skip_build && $resize_metrics; then
-    fail '--resize-metrics requires a build; omit --skip-build'
-fi
-
 [[ $(uname -s) == Linux ]] || fail 'Ferese requires Linux'
-for tool in desktop-file-validate dbus-run-session; do
-    command -v "$tool" >/dev/null || fail "required command not found: $tool"
-done
-desktop-file-validate "$repo_dir/packaging/ferese.desktop"
-user_portal_override="${XDG_CONFIG_HOME:-$HOME/.config}/systemd/user/xdg-desktop-portal-ferese.service.d/override.conf"
-if ((EUID != 0)); then
-    check_user_portal_override "$user_portal_override" "$HOME" || fail 'portal service override needs attention'
+command -v python3 >/dev/null || fail 'install Python 3 first'
+if [[ -n $bundle_path ]]; then
+    [[ -z $bundle_only ]] && ! $offline && ! $resize_metrics && ! $release_set ||
+        fail '--bundle cannot be combined with build options'
+else
+    ((EUID != 0)) || fail 'build as your normal user, without sudo'
+fi
+if [[ -n $bundle_only ]] && $replace_portal_config; then
+    fail '--replace-portal-config requires installation'
 fi
 
-build=(cargo build --manifest-path "$repo_dir/Cargo.toml"
-    --target-dir "$repo_dir/target" --release --locked
-    -p ferese -p ferese-shell -p ferese-settings -p feresectl -p ferese-lock -p ferese-polkit-agent -p xdg-desktop-portal-ferese)
+build=(cargo build --manifest-path "$repo_dir/Cargo.toml" --target-dir "$repo_dir/target" --release --locked)
+mapfile -t packages < <(python3 "$helper" packages)
+((${#packages[@]})) || fail 'could not read package inventory'
+for package in "${packages[@]}"; do build+=(-p "$package"); done
 if $offline; then build+=(--offline); fi
-if $resize_metrics; then build+=(--features ferese/resize-metrics); fi
-if ! $skip_build; then
-    ((EUID != 0)) || fail 'build as your normal user, without sudo (or use --skip-build)'
-    command -v cargo >/dev/null || fail 'install the Rust toolchain and Cargo first'
+features=default
+if $resize_metrics; then
+    build+=(--features ferese/resize-metrics)
+    features=ferese/resize-metrics
 fi
 
-installer=(bash "$repo_dir/scripts/install-session.sh" "$release_id")
+if [[ -z $bundle_path ]]; then
+    bundle_path=${bundle_only:-$repo_dir/target/bundles/$release_id}
+    prepare=(python3 "$helper" bundle --output "$bundle_path" --release-id "$release_id" --features "$features")
+fi
+installer=(/usr/bin/bash "$repo_dir/scripts/install-session.sh" install "$bundle_path")
 if $replace_portal_config; then installer+=(--replace-portal-config); fi
-if ((EUID != 0)); then
+if [[ -z $bundle_only ]] && ((EUID != 0)); then
     if command -v sudo >/dev/null; then
         installer=(sudo "${installer[@]}")
     elif command -v pkexec >/dev/null; then
-        installer=(pkexec /usr/bin/bash "$repo_dir/scripts/install-session.sh" "$release_id")
+        installer=(pkexec "${installer[@]}")
     else
         fail 'system installation requires sudo or pkexec'
     fi
 fi
 
 if $dry_run; then
-    if ! $skip_build; then printf 'Build: '; printf '%q ' "${build[@]}"; printf '\n'; fi
-    printf 'Install: '; printf '%q ' "${installer[@]}"; printf '\n'
+    if [[ ${prepare+x} ]]; then
+        printf 'Build: '; printf '%q ' "${build[@]}"; printf '\n'
+        printf 'Bundle: '; printf '%q ' "${prepare[@]}"; printf '\n'
+    fi
+    if [[ -z $bundle_only ]]; then printf 'Install: '; printf '%q ' "${installer[@]}"; printf '\n'; fi
     exit 0
 fi
 
-cd -- "$repo_dir"
-if ! $skip_build; then "${build[@]}"; fi
-for name in ferese ferese-shell ferese-settings feresectl ferese-lock ferese-polkit-agent xdg-desktop-portal-ferese ferese-record; do
-    [[ -x $repo_dir/target/release/$name ]] || fail "missing release binary: $name"
-done
+if [[ -z $bundle_only ]] && ((EUID != 0)); then
+    python3 "$helper" user-setup --check
+fi
+if [[ ${prepare+x} ]]; then
+    for tool in cargo desktop-file-validate dbus-run-session; do
+        command -v "$tool" >/dev/null || fail "required command not found: $tool"
+    done
+    desktop-file-validate "$repo_dir/packaging/ferese.desktop"
+    desktop-file-validate "$repo_dir/packaging/dev.ferese.Settings.desktop"
+    (cd -- "$repo_dir"; "${build[@]}")
+    "$repo_dir/target/release/ferese-polkit-agent" --check
+    "${prepare[@]}"
+fi
+[[ -z $bundle_only ]] || exit 0
+
+python3 "$helper" verify "$bundle_path"
 "${installer[@]}"
-if ((EUID != 0)) && [[ -f $user_portal_override ]]; then
-    backup_user_portal_override "$user_portal_override" "$HOME" "$release_id" || fail 'could not update portal override'
-    systemctl --user daemon-reload || fail 'could not reload the user portal service configuration'
+if ((EUID != 0)); then
+    if ! python3 "$helper" user-setup; then
+        echo 'System installation succeeded; user setup is incomplete.' >&2
+        echo "Retry as your normal user: python3 '$helper' user-setup" >&2
+        exit 1
+    fi
+else
+    echo "System installation succeeded. As your normal user, run: python3 '$helper' user-setup"
 fi
-echo 'Installation complete. Log out and select Ferese at your login screen, or run ferese-session from a local TTY.'
diff --git a/scripts/installer/install.py b/scripts/installer/install.py
new file mode 100644
index 0000000..cb0c880
--- /dev/null
+++ b/scripts/installer/install.py
@@ -0,0 +1,568 @@
+#!/usr/bin/env python3
+"""Build release bundles and apply recoverable, serialized system installations."""
+import argparse
+import contextlib
+import fcntl
+import hashlib
+import json
+import os
+from pathlib import Path
+import re
+import shutil
+import stat
+import subprocess
+import sys
+import tempfile
+import time
+import uuid
+
+REPO = Path(__file__).resolve().parents[2]
+INVENTORY = json.loads(Path(__file__).with_name('inventory.json').read_text())
+PREFIX = '/usr/local/lib/ferese'
+ID = re.compile(r'[A-Za-z0-9][A-Za-z0-9._-]*\Z')
+
+
+def fail(message):
+    raise ValueError(message)
+
+
+def release_id(value):
+    if not ID.fullmatch(value):
+        fail(f'Invalid release ID: {value}')
+
+    return value
+
+
+def digest(path):
+    with path.open('rb') as stream:
+        checksum = hashlib.sha256()
+        for block in iter(lambda: stream.read(1024 * 1024), b''):
+            checksum.update(block)
+
+        return checksum.hexdigest()
+
+
+def sync_dir(path):
+    fd = os.open(path, os.O_RDONLY | os.O_DIRECTORY)
+    try:
+        os.fsync(fd)
+    finally:
+        os.close(fd)
+
+
+def atomic_bytes(path, data, mode=0o644):
+    path.parent.mkdir(parents=True, exist_ok=True)
+    fd, temporary = tempfile.mkstemp(prefix='.ferese-', dir=path.parent)
+    try:
+        with os.fdopen(fd, 'wb') as stream:
+            stream.write(data)
+            os.fchmod(stream.fileno(), mode)
+            stream.flush()
+            os.fsync(stream.fileno())
+
+        os.replace(temporary, path)
+        sync_dir(path.parent)
+    finally:
+        if os.path.lexists(temporary):
+            os.unlink(temporary)
+
+
+def atomic_copy(path, source, mode):
+    path.parent.mkdir(parents=True, exist_ok=True)
+    fd, temporary = tempfile.mkstemp(prefix='.ferese-', dir=path.parent)
+    try:
+        with os.fdopen(fd, 'wb') as output:
+            source_fd = os.open(source, os.O_RDONLY | os.O_NOFOLLOW)
+            with os.fdopen(source_fd, 'rb') as stream:
+                if not stat.S_ISREG(os.fstat(stream.fileno()).st_mode):
+                    fail(f'Expected regular file: {source}')
+                shutil.copyfileobj(stream, output)
+
+            os.fchmod(output.fileno(), mode)
+            output.flush()
+            os.fsync(output.fileno())
+
+        os.replace(temporary, path)
+        sync_dir(path.parent)
+    finally:
+        if os.path.lexists(temporary):
+            os.unlink(temporary)
+
+
+def sync_tree(path):
+    # Persist new directory entries as well as file contents before publication.
+    for directory, _, _ in os.walk(path, topdown=False):
+        sync_dir(Path(directory))
+
+
+def atomic_json(path, data, mode=0o600):
+    atomic_bytes(path, (json.dumps(data, indent=2, sort_keys=True) + '\n').encode(), mode)
+
+
+def record(rule, name=None):
+    return {key: (value.format(name=name) if key == 'target' else value)
+            for key, value in rule.items() if key != 'source'}
+
+
+def validate_bundle(bundle):
+    if bundle.is_symlink() or not bundle.is_dir():
+        fail(f'Bundle must be a directory, not a symlink: {bundle}')
+
+    for path in bundle.rglob('*'):
+        if path.is_symlink() or not (path.is_file() or path.is_dir()):
+            fail(f'Unexpected bundle entry: {path}')
+
+    manifest = json.loads((bundle / 'manifest.json').read_text())
+    if manifest.get('format') != 1:
+        fail('Unsupported bundle format')
+
+    release_id(manifest['release'])
+    expected = {rule['target']: record(rule) for rule in INVENTORY['files'] if '*' not in rule['source']}
+    seen = set()
+    for item in manifest['files']:
+        target = item['target']
+        allowed = expected.get(target)
+        if allowed is None and re.fullmatch(r'licenses/theme-[A-Za-z0-9._-]+\.txt', target):
+            allowed = {'target': target, 'mode': '0644'}
+
+        if allowed is None or {k: v for k, v in item.items() if k != 'sha256'} != allowed or target in seen:
+            fail(f'Invalid inventory entry: {target}')
+
+        path = bundle / target
+        if not path.is_file() or digest(path) != item['sha256']:
+            fail(f'Checksum mismatch: {target}')
+        if stat.S_IMODE(path.stat().st_mode) != int(item['mode'], 8):
+            fail(f'Incorrect file mode: {target}')
+
+        seen.add(target)
+
+    actual = {str(path.relative_to(bundle)) for path in bundle.rglob('*') if path.is_file()}
+    if not expected.keys() <= seen or actual != seen | {'manifest.json'}:
+        fail('Bundle is incomplete or contains unlisted files')
+
+    return manifest
+
+
+def bundle(args):
+    release_id(args.release_id)
+    source = args.source_root.resolve()
+    output = args.output.absolute()
+    if output.exists() or output.is_symlink():
+        fail(f'Bundle already exists: {output}')
+
+    output.parent.mkdir(parents=True, exist_ok=True)
+    with tempfile.TemporaryDirectory(prefix='.bundle-', dir=output.parent) as temporary:
+        staging = Path(temporary) / 'release'
+        staging.mkdir()
+        files = []
+        for rule in INVENTORY['files']:
+            sources = sorted(source.glob(rule['source']))
+            if not sources:
+                fail(f'Missing bundle input: {rule["source"]}')
+
+            for origin in sources:
+                if origin.is_symlink() or not origin.is_file():
+                    fail(f'Bundle input must be a regular file: {origin}')
+                if rule['mode'] == '0755' and not os.access(origin, os.X_OK):
+                    fail(f'Bundle input is not executable: {origin}')
+
+                item = record(rule, origin.name)
+                destination = staging / item['target']
+                atomic_copy(destination, origin, int(item['mode'], 8))
+                item['sha256'] = digest(destination)
+                files.append(item)
+
+        def git(*command):
+            result = subprocess.run(['git', '-C', str(source), *command], capture_output=True, text=True)
+            return result.stdout.strip() if result.returncode == 0 else None
+
+        status = git('status', '--porcelain')
+        manifest = dict(format=1, release=args.release_id, commit=git('rev-parse', 'HEAD'),
+                        dirty=None if status is None else bool(status), features=args.features,
+                        created_utc=time.strftime('%Y-%m-%dT%H:%M:%SZ', time.gmtime()), files=files)
+        atomic_json(staging / 'manifest.json', manifest, 0o644)
+        validate_bundle(staging)
+        sync_tree(staging)
+        os.rename(staging, output)
+        sync_dir(output.parent)
+
+    print(f'Prepared bundle: {output}')
+
+
+class Installation:
+    def __init__(self, root):
+        self.root = root.resolve()
+        self.base = self.path(PREFIX)
+        self.transaction = self.base / '.transaction'
+
+    def path(self, absolute):
+        if not absolute.startswith('/') or '..' in Path(absolute).parts:
+            fail(f'Invalid installation path: {absolute}')
+
+        path = self.root / absolute.lstrip('/')
+        for parent in path.parents:
+            if parent == self.root:
+                break
+            if parent.is_symlink():
+                fail(f'Refusing symlinked parent: {parent}')
+
+        return path
+
+    @contextlib.contextmanager
+    def lock(self):
+        self.base.mkdir(parents=True, exist_ok=True)
+        lock_path = self.path(PREFIX + '/.install.lock')
+        fd = os.open(lock_path, os.O_CREAT | os.O_RDWR | os.O_NOFOLLOW, 0o600)
+        try:
+            try:
+                fcntl.flock(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
+            except BlockingIOError:
+                fail('Another Ferese installation is in progress')
+
+            yield
+        finally:
+            os.close(fd)
+
+    def pointer(self, name):
+        path = self.path(PREFIX + '/' + name)
+        if not os.path.lexists(path):
+            return None
+        if not path.is_symlink():
+            fail(f'Unmanaged release pointer: {path}')
+
+        target = os.readlink(path)
+        if not target.startswith('releases/') or not ID.fullmatch(target[len('releases/'):]):
+            fail(f'Invalid release pointer: {path}')
+
+        return target[len('releases/'):]
+
+    def state(self, absolute):
+        path = self.path(absolute)
+        if path.is_symlink():
+            return {'kind': 'link', 'target': os.readlink(path)}
+        if not path.exists():
+            return {'kind': 'absent'}
+        if not path.is_file():
+            fail(f'Unmanaged non-file path: {path}')
+
+        return {'kind': 'file', 'sha256': digest(path), 'mode': stat.S_IMODE(path.stat().st_mode)}
+
+    def manifest(self, release):
+        directory = self.path(PREFIX + '/releases/' + release_id(release))
+        if not (directory / 'manifest.json').is_file():
+            fail(f'Release {release} predates verified bundles; select a bundled release for rollback')
+
+        return validate_bundle(directory)
+
+    def current_publication(self, current):
+        if not current:
+            return {}
+
+        directory = self.path(PREFIX + '/releases/' + current)
+        if (directory / 'manifest.json').exists():
+            return self.publication(self.manifest(current))
+
+        # The previous installer retained exact originals for these integration files.
+        # Use those ownership receipts for the first upgrade, never the live file itself.
+        if directory.is_symlink() or not (directory / 'installer-files').is_dir():
+            fail(f'Release has no installation manifest: {current}')
+
+        entries = {}
+        for rule in INVENTORY['files']:
+            if rule.get('link'):
+                target = rule['target']
+                entries['/usr/local/bin/' + target] = (
+                    {'kind': 'link', 'target': PREFIX + '/current/' + target}, None, 'managed')
+            if 'destination' in rule:
+                saved = directory / 'installer-files' / rule['source'].removeprefix('packaging/')
+                if saved.is_file() and not saved.is_symlink():
+                    entries[rule['destination']] = (
+                        {'kind': 'file', 'sha256': digest(saved), 'mode': int(rule['mode'], 8)},
+                        None, rule['policy'])
+
+        return entries
+
+    def publication(self, manifest):
+        entries = {}
+        for item in manifest['files']:
+            if item.get('link'):
+                destination = '/usr/local/bin/' + item['target']
+                entries[destination] = ({'kind': 'link', 'target': PREFIX + '/current/' + item['target']}, None, 'managed')
+            if 'destination' in item:
+                source = PREFIX + '/releases/' + manifest['release'] + '/' + item['target']
+                entries[item['destination']] = ({'kind': 'file', 'sha256': item['sha256'],
+                                                'mode': int(item['mode'], 8)}, source, item['policy'])
+
+        return entries
+
+    def plan(self, manifest, replace_portal=False, remove=False):
+        current = self.pointer('current')
+        self.pointer('previous')
+        previous = self.current_publication(current)
+        desired = {} if remove else self.publication(manifest)
+        operations = []
+        for destination in sorted(previous.keys() | desired.keys()):
+            old = self.state(destination)
+            new, source, policy = desired.get(destination, ({'kind': 'absent'}, None, 'managed'))
+            owned = previous.get(destination, (None,))[0]
+            if old != {'kind': 'absent'} and old != owned and old != new:
+                if not (replace_portal and policy == 'portal' and old['kind'] == 'file'):
+                    fail(f'Unmanaged or modified file: {destination}')
+
+            if old != new:
+                operations.append(dict(path=destination, old=old, new=new, source=source))
+
+        pam_path = '/etc/pam.d/ferese-lock'
+        if not remove and not os.path.lexists(self.path(pam_path)):
+            if self.path('/etc/pam.d/system-auth').is_file():
+                policy = 'fedora'
+            elif all(self.path('/etc/pam.d/' + name).is_file() for name in ('common-auth', 'common-account')):
+                policy = 'debian'
+            elif self.path('/etc/pam.d/login').is_file():
+                policy = 'generic'
+            else:
+                fail('No supported PAM stack; install /etc/pam.d/ferese-lock first')
+
+            item = next(item for item in manifest['files'] if item['target'] == 'pam/' + policy)
+            operations.append(dict(path=pam_path, old={'kind': 'absent'},
+                                   new={'kind': 'file', 'sha256': item['sha256'], 'mode': 0o644},
+                                   source=PREFIX + '/releases/' + manifest['release'] + '/' + item['target']))
+
+        for name, target in [('previous', self.pointer('previous') if current == manifest['release'] and not remove else current),
+                             ('current', None if remove else manifest['release'])]:
+            old = self.state(PREFIX + '/' + name)
+            new = {'kind': 'link', 'target': 'releases/' + target} if target else {'kind': 'absent'}
+            if old != new:
+                operations.append(dict(path=PREFIX + '/' + name, old=old, new=new, source=None))
+
+        return operations
+
+    def write_state(self, absolute, state, source=None):
+        path = self.path(absolute)
+        path.parent.mkdir(parents=True, exist_ok=True)
+        if state['kind'] == 'absent':
+            path.unlink(missing_ok=True)
+            sync_dir(path.parent)
+        elif state['kind'] == 'file':
+            if digest(source) != state['sha256']:
+                fail(f'Recovery source checksum mismatch: {source}')
+
+            atomic_copy(path, source, state['mode'])
+        else:
+            temporary = path.parent / ('.ferese-link-' + uuid.uuid4().hex)
+            try:
+                temporary.symlink_to(state['target'])
+                os.replace(temporary, path)
+                sync_dir(path.parent)
+            finally:
+                temporary.unlink(missing_ok=True)
+
+    def archive(self, journal):
+        history = self.path(PREFIX + '/transactions')
+        history.mkdir(mode=0o700, exist_ok=True)
+        os.rename(self.transaction, history / journal['id'])
+        sync_dir(history)
+        sync_dir(self.base)
+
+    def recover(self):
+        if not self.transaction.exists():
+            return
+
+        if self.transaction.is_symlink():
+            fail('Refusing symlinked recovery transaction')
+
+        journal = json.loads((self.transaction / 'journal.json').read_text())
+        if journal['phase'] != 'committed':
+            # Check all paths before restoring anything; preserve later administrator edits.
+            for operation in journal['operations']:
+                actual = self.state(operation['path'])
+                if actual not in (operation['old'], operation['new']):
+                    fail(f'Recovery conflict at {operation["path"]}; transaction retained at {self.transaction}')
+
+            for index, operation in reversed(list(enumerate(journal['operations']))):
+                self.write_state(operation['path'], operation['old'], self.transaction / 'backup' / str(index))
+
+            journal['phase'] = 'rolled-back'
+            atomic_json(self.transaction / 'journal.json', journal)
+            print('Recovered interrupted installation; restored previous files')
+
+        self.archive(journal)
+
+    def apply(self, operations):
+        if not operations:
+            print('Already installed; no system changes needed')
+            return
+
+        journal = dict(id=time.strftime('%Y%m%dT%H%M%S', time.gmtime()) + '-' + uuid.uuid4().hex,
+                       phase='applying', operations=operations)
+        with tempfile.TemporaryDirectory(prefix='.prepare-', dir=self.base) as temporary:
+            staging = Path(temporary) / 'transaction'
+            staging.mkdir(mode=0o700)
+            for index, operation in enumerate(operations):
+                if self.state(operation['path']) != operation['old']:
+                    fail(f'File changed during preparation: {operation["path"]}')
+                if operation['old']['kind'] == 'file':
+                    backup = staging / 'backup' / str(index)
+                    atomic_copy(backup, self.path(operation['path']), 0o600)
+                    if digest(backup) != operation['old']['sha256']:
+                        fail(f'File changed while backing up: {operation["path"]}')
+
+            atomic_json(staging / 'journal.json', journal)
+            sync_tree(staging)
+            os.rename(staging, self.transaction)
+            sync_dir(self.base)
+
+        try:
+            for operation in operations:
+                if self.state(operation['path']) != operation['old']:
+                    fail(f'File changed during installation: {operation["path"]}')
+
+                source = self.path(operation['source']) if operation['source'] else None
+                self.write_state(operation['path'], operation['new'], source)
+
+            journal['phase'] = 'committed'
+            atomic_json(self.transaction / 'journal.json', journal)
+        except BaseException:
+            self.recover()
+            raise
+
+        self.archive(journal)
+
+    def stage(self, origin, manifest):
+        releases = self.path(PREFIX + '/releases')
+        if releases.is_symlink():
+            fail(f'Refusing symlinked release directory: {releases}')
+
+        releases.mkdir(parents=True, exist_ok=True)
+        destination = releases / manifest['release']
+        if os.path.lexists(destination):
+            if self.manifest(manifest['release']) != manifest:
+                fail(f'Release ID already belongs to a different bundle: {manifest["release"]}')
+
+            return
+
+        with tempfile.TemporaryDirectory(prefix='.stage-', dir=releases) as temporary:
+            staging = Path(temporary) / 'release'
+            staging.mkdir()
+            for item in manifest['files']:
+                atomic_copy(staging / item['target'], origin / item['target'], int(item['mode'], 8))
+
+            atomic_json(staging / 'manifest.json', manifest, 0o644)
+            validate_bundle(staging)
+            sync_tree(staging)
+            os.rename(staging, destination)
+            sync_dir(releases)
+
+
+def system_command(args):
+    if args.root.resolve() == Path('/') and os.geteuid() != 0 and not args.dry_run:
+        fail('System installation requires sudo or pkexec')
+
+    installation = Installation(args.root)
+    if args.dry_run:
+        if installation.transaction.exists():
+            fail('An interrupted transaction requires recovery before planning')
+
+        if args.command == 'recover':
+            print('No interrupted transaction')
+            return
+        if args.command == 'install':
+            manifest = validate_bundle(args.bundle)
+        else:
+            selected = (installation.pointer('current') if args.command == 'uninstall' else
+                        args.release or installation.pointer('previous'))
+            manifest = installation.manifest(selected or fail('No release selected'))
+        operations = installation.plan(manifest, getattr(args, 'replace_portal_config', False), args.command == 'uninstall')
+        for operation in operations:
+            print(f'{operation["path"]}: {operation["old"]["kind"]} -> {operation["new"]["kind"]}')
+        return
+
+    with installation.lock():
+        installation.recover()
+        if args.command == 'recover':
+            return
+        if args.command == 'install':
+            manifest = validate_bundle(args.bundle)
+            # Preflight before retaining a release or changing integration files.
+            operations = installation.plan(manifest, args.replace_portal_config)
+            installation.stage(args.bundle, manifest)
+        elif args.command == 'rollback':
+            selected = args.release or installation.pointer('previous') or fail('No previous release')
+            manifest = installation.manifest(selected)
+            operations = installation.plan(manifest)
+        else:
+            current = installation.pointer('current') or fail('No installed release')
+            manifest = installation.manifest(current)
+            operations = installation.plan(manifest, remove=True)
+
+        installation.apply(operations)
+        print(f'System {args.command} complete: {manifest["release"]}')
+
+
+def user_setup(args):
+    if os.geteuid() == 0:
+        fail('Run user-setup as your normal user')
+
+    config = Path(os.environ.get('XDG_CONFIG_HOME', str(Path.home() / '.config')))
+    override = config / 'systemd/user/xdg-desktop-portal-ferese.service.d/override.conf'
+    expected = f'[Service]\nExecStart=\nExecStart={Path.home()}/.local/libexec/ferese/xdg-desktop-portal-ferese\n'
+    if os.path.lexists(override):
+        if override.is_symlink() or override.read_text() != expected:
+            fail(f'Custom portal override preserved: {override}; update its ExecStart to {PREFIX}/current/xdg-desktop-portal-ferese')
+        if not args.check:
+            backup = override.with_name('override.conf.before-' + uuid.uuid4().hex)
+            override.rename(backup)
+            print(f'Backed up development portal override: {backup}')
+
+    if not args.check:
+        subprocess.run(['systemctl', '--user', 'daemon-reload'], check=True)
+        print('User setup complete. Log out and select Ferese to use the installed release.')
+
+
+def parser():
+    result = argparse.ArgumentParser(description=__doc__)
+    commands = result.add_subparsers(dest='command', required=True)
+    build = commands.add_parser('bundle')
+    build.add_argument('--source-root', type=Path, default=REPO)
+    build.add_argument('--output', type=Path, required=True)
+    build.add_argument('--release-id', required=True)
+    build.add_argument('--features', default='default')
+    commands.add_parser('packages')
+    verify = commands.add_parser('verify')
+    verify.add_argument('bundle', type=Path)
+    user = commands.add_parser('user-setup')
+    user.add_argument('--check', action='store_true')
+    for name in ('install', 'rollback', 'recover', 'uninstall'):
+        command = commands.add_parser(name)
+        command.add_argument('--root', type=Path, default=Path('/'), help='Destination filesystem root (for packaging/tests)')
+        command.add_argument('--dry-run', action='store_true')
+        if name == 'install':
+            command.add_argument('bundle', type=Path)
+            command.add_argument('--replace-portal-config', action='store_true')
+        elif name == 'rollback':
+            command.add_argument('release', nargs='?')
+
+    return result
+
+
+def main():
+    args = parser().parse_args()
+    if args.command == 'bundle':
+        bundle(args)
+    elif args.command == 'verify':
+        manifest = validate_bundle(args.bundle)
+        print(f'Verified bundle: {manifest["release"]}')
+    elif args.command == 'packages':
+        print('\n'.join(INVENTORY['packages']))
+    elif args.command == 'user-setup':
+        user_setup(args)
+    else:
+        system_command(args)
+
+
+if __name__ == '__main__':
+    try:
+        main()
+    except (ValueError, OSError, KeyError, TypeError, subprocess.CalledProcessError) as error:
+        print(f'ferese installer: {error}', file=sys.stderr)
+        sys.exit(1)
diff --git a/scripts/installer/inventory.json b/scripts/installer/inventory.json
new file mode 100644
index 0000000..f4d13cc
--- /dev/null
+++ b/scripts/installer/inventory.json
@@ -0,0 +1,187 @@
+{
+  "packages": [
+    "ferese",
+    "ferese-shell",
+    "ferese-settings",
+    "feresectl",
+    "ferese-lock",
+    "ferese-polkit-agent",
+    "xdg-desktop-portal-ferese"
+  ],
+  "files": [
+    {
+      "source": "target/release/ferese",
+      "target": "ferese",
+      "mode": "0755",
+      "link": true
+    },
+    {
+      "source": "target/release/ferese-shell",
+      "target": "ferese-shell",
+      "mode": "0755",
+      "link": true
+    },
+    {
+      "source": "target/release/ferese-settings",
+      "target": "ferese-settings",
+      "mode": "0755",
+      "link": true
+    },
+    {
+      "source": "target/release/feresectl",
+      "target": "feresectl",
+      "mode": "0755",
+      "link": true
+    },
+    {
+      "source": "target/release/ferese-lock",
+      "target": "ferese-lock",
+      "mode": "0755",
+      "link": true
+    },
+    {
+      "source": "target/release/ferese-polkit-agent",
+      "target": "ferese-polkit-agent",
+      "mode": "0755",
+      "link": true
+    },
+    {
+      "source": "target/release/xdg-desktop-portal-ferese",
+      "target": "xdg-desktop-portal-ferese",
+      "mode": "0755",
+      "link": true
+    },
+    {
+      "source": "target/release/ferese-record",
+      "target": "ferese-record",
+      "mode": "0755",
+      "link": true
+    },
+    {
+      "source": "packaging/ferese-session",
+      "target": "ferese-session",
+      "mode": "0755",
+      "link": true
+    },
+    {
+      "source": "packaging/ferese-session-shell",
+      "target": "ferese-session-shell",
+      "mode": "0755",
+      "link": false
+    },
+    {
+      "source": "packaging/ferese-screenshot",
+      "target": "ferese-screenshot",
+      "mode": "0755",
+      "link": true
+    },
+    {
+      "source": "packaging/config.kdl",
+      "target": "config.example.kdl",
+      "mode": "0644"
+    },
+    {
+      "source": "assets/fonts/Comfortaa-LICENSE.txt",
+      "target": "licenses/Comfortaa-LICENSE.txt",
+      "mode": "0644"
+    },
+    {
+      "source": "assets/fonts/Cantarell-LICENSE.txt",
+      "target": "licenses/Cantarell-LICENSE.txt",
+      "mode": "0644"
+    },
+    {
+      "source": "assets/themes/licenses/*.txt",
+      "target": "licenses/theme-{name}",
+      "mode": "0644"
+    },
+    {
+      "source": "assets/wallpapers/ferese.png",
+      "target": "wallpapers/ferese.png",
+      "mode": "0644"
+    },
+    {
+      "source": "assets/wallpapers/ferese.svg",
+      "target": "wallpapers/ferese.svg",
+      "mode": "0644"
+    },
+    {
+      "source": "packaging/ferese.desktop",
+      "target": "integration/usr/share/wayland-sessions/ferese.desktop",
+      "mode": "0644",
+      "destination": "/usr/share/wayland-sessions/ferese.desktop",
+      "policy": "managed"
+    },
+    {
+      "source": "packaging/dev.ferese.Settings.desktop",
+      "target": "integration/usr/local/share/applications/dev.ferese.Settings.desktop",
+      "mode": "0644",
+      "destination": "/usr/local/share/applications/dev.ferese.Settings.desktop",
+      "policy": "managed"
+    },
+    {
+      "source": "packaging/icons/ferese.svg",
+      "target": "integration/usr/local/share/icons/hicolor/scalable/apps/ferese.svg",
+      "mode": "0644",
+      "destination": "/usr/local/share/icons/hicolor/scalable/apps/ferese.svg",
+      "policy": "managed"
+    },
+    {
+      "source": "packaging/icons/ferese.svg",
+      "target": "integration/usr/local/share/icons/hicolor/scalable/apps/dev.ferese.Settings.svg",
+      "mode": "0644",
+      "destination": "/usr/local/share/icons/hicolor/scalable/apps/dev.ferese.Settings.svg",
+      "policy": "managed"
+    },
+    {
+      "source": "packaging/systemd/ferese-session.target",
+      "target": "integration/usr/local/lib/systemd/user/ferese-session.target",
+      "mode": "0644",
+      "destination": "/usr/local/lib/systemd/user/ferese-session.target",
+      "policy": "managed"
+    },
+    {
+      "source": "packaging/systemd/xdg-desktop-portal-ferese.service",
+      "target": "integration/usr/local/lib/systemd/user/xdg-desktop-portal-ferese.service",
+      "mode": "0644",
+      "destination": "/usr/local/lib/systemd/user/xdg-desktop-portal-ferese.service",
+      "policy": "managed"
+    },
+    {
+      "source": "packaging/portal/ferese.portal",
+      "target": "integration/usr/share/xdg-desktop-portal/portals/ferese.portal",
+      "mode": "0644",
+      "destination": "/usr/share/xdg-desktop-portal/portals/ferese.portal",
+      "policy": "portal"
+    },
+    {
+      "source": "packaging/portal/ferese-portals.conf",
+      "target": "integration/usr/share/xdg-desktop-portal/ferese-portals.conf",
+      "mode": "0644",
+      "destination": "/usr/share/xdg-desktop-portal/ferese-portals.conf",
+      "policy": "portal"
+    },
+    {
+      "source": "packaging/portal/org.freedesktop.impl.portal.desktop.ferese.service",
+      "target": "integration/usr/local/share/dbus-1/services/org.freedesktop.impl.portal.desktop.ferese.service",
+      "mode": "0644",
+      "destination": "/usr/local/share/dbus-1/services/org.freedesktop.impl.portal.desktop.ferese.service",
+      "policy": "managed"
+    },
+    {
+      "source": "packaging/pam.d/ferese-lock.fedora",
+      "target": "pam/fedora",
+      "mode": "0644"
+    },
+    {
+      "source": "packaging/pam.d/ferese-lock.debian",
+      "target": "pam/debian",
+      "mode": "0644"
+    },
+    {
+      "source": "packaging/pam.d/ferese-lock.generic",
+      "target": "pam/generic",
+      "mode": "0644"
+    }
+  ]
+}
diff --git a/scripts/tests/test_portal_install.py b/scripts/tests/test_portal_install.py
index 30b808b..526d4ee 100644
--- a/scripts/tests/test_portal_install.py
+++ b/scripts/tests/test_portal_install.py
@@ -1,161 +1,362 @@
-"""Exercise portal upgrade preflight against temporary installation files."""
+"""Run complete installer commands against disposable destination filesystems."""
+import fcntl
+import importlib.util
+import json
+import os
 from pathlib import Path
+import shutil
 import subprocess
+import sys
 import tempfile
 import unittest
 
 REPO = Path(__file__).resolve().parents[2]
-LEGACY = ('[D-BUS Service]\n'
-          'Name=org.freedesktop.impl.portal.desktop.ferese\n'
-          'Exec=/usr/local/lib/ferese/current/xdg-desktop-portal-ferese\n')
+HELPER = REPO / 'scripts/installer/install.py'
+spec = importlib.util.spec_from_file_location('ferese_install', HELPER)
+installer = importlib.util.module_from_spec(spec)
+spec.loader.exec_module(installer)
+PREFIX = installer.PREFIX.lstrip('/')
+PORTAL = 'usr/share/xdg-desktop-portal/ferese-portals.conf'
+UNIT = 'usr/local/lib/systemd/user/xdg-desktop-portal-ferese.service'
+DESKTOP = 'usr/share/wayland-sessions/ferese.desktop'
 
 
-class PortalInstallTest(unittest.TestCase):
-    def preflight(self, service=None, unit=None):
-        script = (REPO / 'scripts/install-session.sh').read_text()
-        start = script.index('service=/usr/local/share/dbus-1/services/')
-        helpers = script[:script.index('repo_dir=')]
-        script = helpers + script[start:script.index('session_target=', start)]
-        with tempfile.TemporaryDirectory() as directory:
-            root = Path(directory)
-            if service is not None:
-                (root / 'activation.service').write_text(service)
-            if unit is not None:
-                (root / 'portal.service').write_text(unit)
-            script = script.replace(
-                'service=/usr/local/share/dbus-1/services/org.freedesktop.impl.portal.desktop.ferese.service',
-                'service="$TEST_ROOT/activation.service"')
-            script = script.replace('$(basename "$service")',
-                                    'org.freedesktop.impl.portal.desktop.ferese.service')
-            script = script.replace(
-                'portal_unit=/usr/local/lib/systemd/user/xdg-desktop-portal-ferese.service',
-                'portal_unit="$TEST_ROOT/portal.service"')
-            return subprocess.run(['bash', '-eu', '-c', script],
-                                  env={'repo_dir': str(REPO), 'TEST_ROOT': directory, 'install_root': directory},
-                                  capture_output=True, text=True)
+class InstallerTest(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        cls.shared = tempfile.TemporaryDirectory()
+        cls.source = Path(cls.shared.name) / 'source'
+        for rule in installer.INVENTORY['files']:
+            if rule['source'].startswith('target/release/'):
+                paths = [REPO / rule['source']]
+            else:
+                paths = sorted(REPO.glob(rule['source']))
 
-    def configuration_preflight(self, portal=None, preferences=None, previous=None, replace=False):
-        script = (REPO / 'scripts/install-session.sh').read_text()
-        helpers = script[:script.index('repo_dir=')]
-        start = script.index('for entry in ')
-        check = script[start:script.index('service=/usr/local/share/dbus-1/services/', start)]
-        check = check.replace('/usr/share/xdg-desktop-portal/', '$TEST_ROOT/config/')
-        with tempfile.TemporaryDirectory() as directory:
-            root = Path(directory)
-            for relative, content in [('portals/ferese.portal', portal), ('ferese-portals.conf', preferences)]:
-                if content is not None:
-                    destination = root / 'config' / relative
-                    destination.parent.mkdir(parents=True, exist_ok=True)
-                    destination.write_text(content)
-            if previous:
-                for relative, content in previous.items():
-                    destination = root / 'current/installer-files/portal' / relative
-                    destination.parent.mkdir(parents=True, exist_ok=True)
-                    destination.write_text(content)
-            return subprocess.run(['bash', '-eu', '-c', helpers + check],
-                                  env={'repo_dir': str(REPO), 'TEST_ROOT': directory, 'install_root': directory,
-                                       'replace_portal_config': str(replace).lower()},
-                                  capture_output=True, text=True)
+            for path in paths:
+                target = cls.source / path.relative_to(REPO)
+                target.parent.mkdir(parents=True, exist_ok=True)
+                target.write_bytes(b'#!/bin/sh\nexit 0\n' if rule['source'].startswith('target/release/') else path.read_bytes())
+                target.chmod(int(rule['mode'], 8))
 
-    def user_override(self, content, backup=False):
-        script = (REPO / 'scripts/install.sh').read_text()
-        helpers = script[script.index('check_user_portal_override()'):script.index('fail() {')]
-        with tempfile.TemporaryDirectory() as directory:
-            root = Path(directory)
-            override = root / 'override.conf'
-            if content is not None:
-                override.write_text(content.replace('USER_HOME', directory))
-            command = 'backup_user_portal_override' if backup else 'check_user_portal_override'
-            result = subprocess.run(['bash', '-eu', '-c', helpers +
-                                     f'\n{command} "$TEST_ROOT/override.conf" "$TEST_ROOT" test-release'],
-                                    env={'TEST_ROOT': directory}, capture_output=True, text=True)
-            saved = root / 'override.conf.before-test-release'
-            return result, override.exists(), saved.read_text() if saved.exists() else None
+        cls.bundles = []
+        for name in ('first', 'second'):
+            for relative in ('portal/ferese-portals.conf', 'systemd/xdg-desktop-portal-ferese.service', 'ferese.desktop'):
+                with (cls.source / 'packaging' / relative).open('a') as stream:
+                    stream.write(f'\n# {name}\n')
 
-    def test_user_development_override_is_backed_up(self):
-        content = '[Service]\nExecStart=\nExecStart=USER_HOME/.local/libexec/ferese/xdg-desktop-portal-ferese\n'
-        result, exists, saved = self.user_override(content, backup=True)
-        self.assertEqual(result.returncode, 0, result.stderr)
-        self.assertFalse(exists)
-        self.assertIn('/.local/libexec/ferese/xdg-desktop-portal-ferese', saved)
+            output = Path(cls.shared.name) / name
+            subprocess.run([sys.executable, str(HELPER), 'bundle', '--source-root', str(cls.source),
+                            '--output', str(output), '--release-id', name], check=True, capture_output=True)
+            cls.bundles.append(output)
 
-    def test_custom_user_override_is_preserved_and_reported(self):
-        result, exists, saved = self.user_override('[Service]\nExecStart=/custom/portal\n', backup=True)
-        self.assertNotEqual(result.returncode, 0)
-        self.assertTrue(exists)
-        self.assertIsNone(saved)
-        self.assertIn('takes precedence', result.stderr)
+    @classmethod
+    def tearDownClass(cls):
+        cls.shared.cleanup()
 
-    def test_missing_user_override_needs_no_backup(self):
-        result, exists, saved = self.user_override(None, backup=True)
-        self.assertEqual(result.returncode, 0, result.stderr)
-        self.assertFalse(exists)
-        self.assertIsNone(saved)
+    def setUp(self):
+        self.temporary = tempfile.TemporaryDirectory()
+        self.addCleanup(self.temporary.cleanup)
+        self.root = Path(self.temporary.name) / 'root'
+        pam = self.root / 'etc/pam.d/login'
+        pam.parent.mkdir(parents=True)
+        pam.write_text('test PAM stack\n')
+        self.base = self.root / PREFIX
 
-    def test_existing_development_install_requires_explicit_replacement(self):
-        portal = ('[portal]\nDBusName=org.freedesktop.impl.portal.desktop.ferese\n'
-                  'Interfaces=org.freedesktop.impl.portal.ScreenCast;\nUseIn=Ferese;\n')
-        preferences = '[preferred]\ndefault=gtk;\norg.freedesktop.impl.portal.ScreenCast=ferese;\n'
-        result = self.configuration_preflight(portal, preferences)
-        self.assertNotEqual(result.returncode, 0)
-        self.assertIn('--replace-portal-config', result.stderr)
-        result = self.configuration_preflight(portal, preferences, replace=True)
-        self.assertEqual(result.returncode, 0, result.stderr)
+    def run_command(self, *args, success=True, fault=None, fault_after=4):
+        command = [sys.executable, str(HELPER)]
+        if fault:
+            # Inject failure at the filesystem boundary, without shipping production test hooks.
+            code = f'''import importlib.util, os, sys
+spec = importlib.util.spec_from_file_location('installer', {str(HELPER)!r})
+m = importlib.util.module_from_spec(spec)
+spec.loader.exec_module(m)
+original = m.Installation.write_state
+count = 0
+def write(self, *args, **kwargs):
+    global count
+    original(self, *args, **kwargs)
+    count += 1
+    if count == {fault_after}:
+        {fault}
+m.Installation.write_state = write
+m.main()
+'''
+            command = [sys.executable, '-c', code]
 
-    def test_previous_portal_configuration_is_backed_up(self):
-        script = (REPO / 'scripts/install-session.sh').read_text()
-        start = script.index('for relative in portals/ferese.portal')
-        backup = script[start:script.index('for relative in ', start + 1)]
-        backup = backup.replace('/usr/share/xdg-desktop-portal/', '$TEST_ROOT/config/')
-        with tempfile.TemporaryDirectory() as directory:
-            root = Path(directory)
-            for relative in ('portals/ferese.portal', 'ferese-portals.conf'):
-                source = root / 'config' / relative
-                source.parent.mkdir(parents=True, exist_ok=True)
-                source.write_text('existing custom content\n')
-            result = subprocess.run(['bash', '-eu', '-c', backup],
-                                    env={'TEST_ROOT': directory, 'release_dir': str(root / 'release')},
-                                    capture_output=True, text=True)
+        result = subprocess.run([*command, *map(str, args), '--root', str(self.root)], capture_output=True, text=True)
+        if success:
             self.assertEqual(result.returncode, 0, result.stderr)
-            for relative in ('portals/ferese.portal', 'ferese-portals.conf'):
-                self.assertEqual((root / 'release/portal-config.previous' / relative).read_text(),
-                                 'existing custom content\n')
-                self.assertEqual((root / 'config' / relative).read_text(), 'existing custom content\n')
+        else:
+            self.assertNotEqual(result.returncode, 0, result.stdout)
 
-    def test_upgrades_recorded_previous_release(self):
-        old_portal = '[portal]\nInterfaces=org.freedesktop.impl.portal.Settings;\n'
-        old_preferences = '[preferred]\norg.freedesktop.impl.portal.Settings=ferese;\n'
-        result = self.configuration_preflight(old_portal, old_preferences,
-                                              {'ferese.portal': old_portal, 'ferese-portals.conf': old_preferences})
-        self.assertEqual(result.returncode, 0, result.stderr)
-        result = self.configuration_preflight(old_portal + 'UseIn=Custom;\n', old_preferences,
-                                              {'ferese.portal': old_portal, 'ferese-portals.conf': old_preferences})
-        self.assertNotEqual(result.returncode, 0)
-        self.assertIn('Unmanaged portal configuration', result.stderr)
+        return result
 
-    def test_preserves_custom_configuration(self):
-        portal = (REPO / 'packaging/portal/ferese.portal').read_text()
-        preferences = '[preferred]\ndefault=custom;\n'
-        result = self.configuration_preflight(portal, preferences)
-        self.assertNotEqual(result.returncode, 0)
-        self.assertIn('Unmanaged portal configuration', result.stderr)
+    def install(self, index=0, **kwargs):
+        return self.run_command('install', self.bundles[index], **kwargs)
 
-    def test_accepts_fresh_install_and_previous_activation_file(self):
-        self.assertEqual(self.preflight().returncode, 0)
-        self.assertEqual(self.preflight(LEGACY).returncode, 0)
+    def snapshot(self):
+        result = {}
+        for path in self.root.rglob('*'):
+            if path.is_relative_to(self.base / 'transactions') or path.is_relative_to(self.base / 'releases'):
+                continue
+            if path.is_symlink():
+                result[str(path.relative_to(self.root))] = os.readlink(path)
+            elif path.is_file() and path.name != '.install.lock':
+                result[str(path.relative_to(self.root))] = path.read_bytes()
 
-    def test_accepts_current_managed_files(self):
-        service = (REPO / 'packaging/portal/org.freedesktop.impl.portal.desktop.ferese.service').read_text()
-        unit = (REPO / 'packaging/systemd/xdg-desktop-portal-ferese.service').read_text()
-        self.assertEqual(self.preflight(service, unit).returncode, 0)
+        return result
 
-    def test_preserves_modified_activation_and_systemd_files(self):
-        result = self.preflight(LEGACY.replace('/usr/local/lib/ferese/current/', '/custom/'))
-        self.assertNotEqual(result.returncode, 0)
-        self.assertIn('Unmanaged portal service', result.stderr)
-        result = self.preflight(LEGACY, '[Service]\nExecStart=/custom/portal\n')
-        self.assertNotEqual(result.returncode, 0)
-        self.assertIn('Unmanaged portal unit', result.stderr)
+    def test_fresh_upgrade_and_rollback_restore_all_integration(self):
+        self.install()
+        first = [(self.root / path).read_bytes() for path in (PORTAL, UNIT, DESKTOP)]
+        self.assertEqual(os.readlink(self.base / 'current'), 'releases/first')
+        self.assertEqual(os.readlink(self.root / 'usr/local/bin/ferese'), '/usr/local/lib/ferese/current/ferese')
+        self.install(1)
+        self.assertEqual(os.readlink(self.base / 'previous'), 'releases/first')
+        for path, old in zip((PORTAL, UNIT, DESKTOP), first):
+            self.assertNotEqual((self.root / path).read_bytes(), old)
+
+        self.run_command('rollback')
+        self.assertEqual(os.readlink(self.base / 'current'), 'releases/first')
+        self.assertEqual(os.readlink(self.base / 'previous'), 'releases/second')
+        self.assertEqual([(self.root / path).read_bytes() for path in (PORTAL, UNIT, DESKTOP)], first)
+
+    def test_upgrade_uses_previous_installer_ownership_receipts(self):
+        self.install()
+        release = self.base / 'releases/first'
+        (release / 'manifest.json').unlink()
+        for rule in installer.INVENTORY['files']:
+            if 'destination' in rule and ('portal/' in rule['source'] or 'systemd/' in rule['source']):
+                receipt = release / 'installer-files' / rule['source'].removeprefix('packaging/')
+                receipt.parent.mkdir(parents=True, exist_ok=True)
+                shutil.copyfile(self.root / rule['destination'].lstrip('/'), receipt)
+
+        # The old installer saved no desktop receipt: only identical incoming files are safe.
+        (self.root / DESKTOP).write_bytes((self.bundles[1] / ('integration/' + DESKTOP)).read_bytes())
+        self.install(1)
+        result = self.run_command('rollback', success=False)
+        self.assertIn('predates verified bundles', result.stderr)
+        self.assertEqual(os.readlink(self.base / 'current'), 'releases/second')
+
+    def test_reinstall_is_idempotent_and_keeps_previous(self):
+        self.install()
+        self.install(1)
+        before = self.snapshot()
+        self.install(1)
+        self.assertEqual(before, self.snapshot())
+        self.assertEqual(len(list((self.base / 'transactions').iterdir())), 2)
+
+    def test_modified_configuration_is_preserved_on_upgrade_and_rollback(self):
+        self.install()
+        self.install(1)
+        (self.root / UNIT).write_text('administrator override\n')
+        before = self.snapshot()
+        self.run_command('rollback', success=False)
+        self.assertEqual(before, self.snapshot())
+        self.install(success=False)
+        self.assertEqual(before, self.snapshot())
+
+    def test_explicit_portal_replacement_keeps_backup(self):
+        self.install()
+        (self.root / PORTAL).write_text('administrator preferences\n')
+        self.install(1, success=False)
+        self.run_command('install', self.bundles[1], '--replace-portal-config')
+        backups = list((self.base / 'transactions').glob('*/backup/*'))
+        self.assertTrue(any(path.read_text() == 'administrator preferences\n' for path in backups))
+
+    def test_normal_failure_restores_previous_files_and_can_retry(self):
+        self.install()
+        before = self.snapshot()
+        self.install(1, success=False, fault="raise OSError('injected write failure')")
+        self.assertEqual(before, self.snapshot())
+        self.assertFalse((self.base / '.transaction').exists())
+        self.install(1)
+
+    def test_killed_upgrade_recovers_before_next_install(self):
+        self.install()
+        self.install(1, success=False, fault='os._exit(91)')
+        self.assertTrue((self.base / '.transaction/journal.json').is_file())
+        result = self.install(1)
+        self.assertIn('Recovered interrupted', result.stdout)
+        self.assertFalse((self.base / '.transaction').exists())
+        self.assertEqual(os.readlink(self.base / 'current'), 'releases/second')
+
+    def test_failure_after_switching_current_restores_previous_release(self):
+        self.install()
+        before = self.snapshot()
+        self.install(1, success=False, fault="raise OSError('failure after current switch')", fault_after=5)
+        self.assertEqual(before, self.snapshot())
+
+    def test_killed_install_after_current_switch_is_recovered(self):
+        self.install()
+        before = self.snapshot()
+        self.install(1, success=False, fault='os._exit(91)', fault_after=5)
+        self.assertEqual(os.readlink(self.base / 'current'), 'releases/second')
+        self.run_command('recover')
+        self.assertEqual(before, self.snapshot())
+
+    def test_killed_fresh_install_recovers_absent_files(self):
+        before = self.snapshot()
+        self.install(success=False, fault='os._exit(91)')
+        self.run_command('recover')
+        self.assertEqual(before, self.snapshot())
+
+    def test_recovery_preserves_edits_made_after_interruption(self):
+        self.install()
+        self.install(1, success=False, fault='os._exit(91)')
+        (self.root / UNIT).write_text('edited after crash\n')
+        result = self.run_command('recover', success=False)
+        self.assertIn('Recovery conflict', result.stderr)
+        self.assertEqual((self.root / UNIT).read_text(), 'edited after crash\n')
+        self.assertTrue((self.base / '.transaction').exists())
+
+    def test_concurrent_install_is_rejected(self):
+        self.base.mkdir(parents=True)
+        with (self.base / '.install.lock').open('w') as lock:
+            fcntl.flock(lock, fcntl.LOCK_EX)
+            result = self.install(success=False)
+
+        self.assertIn('in progress', result.stderr)
+        self.assertFalse((self.base / 'current').exists())
+
+    def test_dry_run_does_not_write(self):
+        before = self.snapshot()
+        self.run_command('install', self.bundles[0], '--dry-run')
+        self.assertEqual(before, self.snapshot())
+        self.assertFalse(self.base.exists())
+
+    def test_custom_pam_is_preserved(self):
+        pam = self.root / 'etc/pam.d/ferese-lock'
+        pam.write_text('administrator authentication\n')
+        self.install()
+        self.install(1)
+        self.run_command('rollback')
+        self.assertEqual(pam.read_text(), 'administrator authentication\n')
+
+    def test_missing_pam_stack_fails_before_publication(self):
+        (self.root / 'etc/pam.d/login').unlink()
+        self.install(success=False)
+        self.assertFalse((self.base / 'current').exists())
+        self.assertFalse((self.root / UNIT).exists())
+
+    def test_symlinked_destination_parent_is_rejected(self):
+        outside = Path(self.temporary.name) / 'outside'
+        outside.mkdir()
+        (self.root / 'usr').symlink_to(outside)
+        self.install(success=False)
+        self.assertEqual(list(outside.iterdir()), [])
+
+    def test_uninstall_preserves_releases_pam_and_unrelated_files(self):
+        self.install()
+        unrelated = self.root / 'usr/local/bin/unrelated'
+        unrelated.write_text('keep\n')
+        self.run_command('uninstall')
+        self.assertFalse(os.path.lexists(self.base / 'current'))
+        self.assertFalse(os.path.lexists(self.root / 'usr/local/bin/ferese'))
+        self.assertFalse((self.root / PORTAL).exists())
+        self.assertTrue((self.base / 'releases/first/ferese').is_file())
+        self.assertTrue((self.root / 'etc/pam.d/ferese-lock').is_file())
+        self.assertEqual(unrelated.read_text(), 'keep\n')
+
+    def test_corrupt_incomplete_unlisted_or_symlink_bundle_is_rejected(self):
+        for mutation in ('checksum', 'missing', 'extra', 'symlink', 'mode', 'traversal'):
+            with self.subTest(mutation=mutation):
+                copy = Path(self.temporary.name) / mutation
+                shutil.copytree(self.bundles[0], copy)
+                binary = copy / 'ferese'
+                if mutation == 'checksum':
+                    binary.write_text('corrupt')
+                elif mutation == 'missing':
+                    binary.unlink()
+                elif mutation == 'extra':
+                    (copy / 'unexpected').write_text('extra')
+                elif mutation == 'symlink':
+                    binary.unlink()
+                    binary.symlink_to('/etc/passwd')
+                elif mutation == 'mode':
+                    binary.chmod(0o777)
+                else:
+                    manifest = json.loads((copy / 'manifest.json').read_text())
+                    manifest['files'][0]['target'] = '../../etc/passwd'
+                    (copy / 'manifest.json').write_text(json.dumps(manifest))
+
+                self.run_command('install', copy, success=False)
+                self.assertFalse((self.base / 'current').exists())
+
+    def test_release_id_collision_does_not_change_current(self):
+        self.install()
+        changed = Path(self.temporary.name) / 'changed'
+        shutil.copytree(self.bundles[0], changed)
+        manifest = json.loads((changed / 'manifest.json').read_text())
+        manifest['features'] = 'different-build'
+        (changed / 'manifest.json').write_text(json.dumps(manifest))
+        before = self.snapshot()
+        self.run_command('install', changed, success=False)
+        self.assertEqual(before, self.snapshot())
+
+
+class FrontendTest(unittest.TestCase):
+    def test_elevation_preserves_arguments_for_sudo_and_pkexec(self):
+        import shlex
+        for elevation in ('sudo', 'pkexec'):
+            with self.subTest(elevation=elevation), tempfile.TemporaryDirectory() as directory:
+                bin_dir = Path(directory)
+                for tool in ('python3', 'dirname', 'uname', 'date'):
+                    (bin_dir / tool).symlink_to(shutil.which(tool))
+                elevate = bin_dir / elevation
+                elevate.write_text('#!/bin/sh\nexit 99\n')
+                elevate.chmod(0o755)
+                result = subprocess.run(['/bin/bash', str(REPO / 'scripts/install.sh'), '--bundle',
+                                         '/tmp/bundle with spaces', '--replace-portal-config', '--dry-run'],
+                                        env=dict(os.environ, PATH=str(bin_dir)), capture_output=True, text=True)
+                self.assertEqual(result.returncode, 0, result.stderr)
+                command = shlex.split(result.stdout.removeprefix('Install: '))
+                # Building is prohibited as root, but installing an existing bundle is allowed.
+                expected = ([] if os.geteuid() == 0 else [elevation]) + [
+                    '/usr/bin/bash', str(REPO / 'scripts/install-session.sh'), 'install',
+                    '/tmp/bundle with spaces', '--replace-portal-config']
+                self.assertEqual(command, expected)
+
+    def test_incompatible_or_missing_options_are_rejected(self):
+        for options in (['--bundle'], ['--release-id'], ['--bundle-only'],
+                        ['--bundle', '/tmp/bundle', '--offline'],
+                        ['--bundle', '/tmp/bundle', '--resize-metrics'],
+                        ['--bundle', '/tmp/bundle', '--release-id', 'another'],
+                        ['--skip-build']):
+            with self.subTest(options=options):
+                result = subprocess.run(['/bin/bash', str(REPO / 'scripts/install.sh'), *options],
+                                        capture_output=True)
+                self.assertNotEqual(result.returncode, 0)
+
+
+class UserSetupTest(unittest.TestCase):
+    def test_repeatable_migration_and_reload_after_failure(self):
+        with tempfile.TemporaryDirectory() as directory:
+            home = Path(directory)
+            override = home / '.config/systemd/user/xdg-desktop-portal-ferese.service.d/override.conf'
+            override.parent.mkdir(parents=True)
+            override.write_text(f'[Service]\nExecStart=\nExecStart={home}/.local/libexec/ferese/xdg-desktop-portal-ferese\n')
+            bin_dir = home / 'bin'
+            bin_dir.mkdir()
+            systemctl = bin_dir / 'systemctl'
+            systemctl.write_text('#!/bin/sh\nexit 1\n')
+            systemctl.chmod(0o755)
+            env = dict(os.environ, HOME=str(home), XDG_CONFIG_HOME=str(home / '.config'), PATH=str(bin_dir))
+            # User setup intentionally refuses root; emulate the user identity in root-run CI.
+            command = [sys.executable, '-c', f"import runpy, os; os.geteuid = lambda: 1000; runpy.run_path({str(HELPER)!r}, run_name='__main__')", 'user-setup']
+            result = subprocess.run(command, env=env, capture_output=True)
+            self.assertNotEqual(result.returncode, 0)
+            self.assertFalse(override.exists())
+            self.assertEqual(len(list(override.parent.glob('*.before-*'))), 1)
+            systemctl.write_text('#!/bin/sh\nexit 0\n')
+            for _ in range(2):
+                result = subprocess.run(command, env=env, capture_output=True)
+                self.assertEqual(result.returncode, 0, result.stderr)
+            self.assertEqual(len(list(override.parent.glob('*.before-*'))), 1)
+            override.write_text('custom configuration\n')
+            result = subprocess.run(command, env=env, capture_output=True)
+            self.assertNotEqual(result.returncode, 0)
+            self.assertEqual(override.read_text(), 'custom configuration\n')
 
 
 if __name__ == '__main__':