diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 474aab6..93fa31c 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -42,6 +42,9 @@ jobs:
         run: cmake --build build --parallel 2
       - name: Test
         run: ctest --test-dir build --output-on-failure --parallel 2
+      - name: Application QML startup smoke
+        shell: bash
+        run: dbus-run-session -- bash tests/ApplicationStartupSmoke.sh "$PWD/build/ryofiles"
       - name: FileChooser D-Bus smoke
         shell: bash
         run: dbus-run-session -- bash tests/FileChooserPortalSmoke.sh "$PWD/build/ryofiles"
diff --git a/qml/components/GitDiffPanel.qml b/qml/components/GitDiffPanel.qml
index 3faef41..de58de9 100644
--- a/qml/components/GitDiffPanel.qml
+++ b/qml/components/GitDiffPanel.qml
@@ -269,7 +269,6 @@ Item {
                         selectedTextColor: Ryoku.inkOnBone
                         font.family: Ryoku.monoFont
                         font.pixelSize: 10 * root.uiScale
-                        lineHeight: 1.25
                     }
                 }
             }
diff --git a/tests/ApplicationStartupSmoke.sh b/tests/ApplicationStartupSmoke.sh
new file mode 100644
index 0000000..2e146b8
--- /dev/null
+++ b/tests/ApplicationStartupSmoke.sh
@@ -0,0 +1,55 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: GPL-3.0-only
+set -euo pipefail
+
+if [[ $# -ne 1 ]]; then
+    echo "usage: $0 /path/to/ryofiles" >&2
+    exit 2
+fi
+
+binary="$1"
+[[ -x "$binary" ]] || { echo "not executable: $binary" >&2; exit 2; }
+
+workdir="$(mktemp -d)"
+trap 'rm -rf "$workdir"' EXIT
+mkdir -p "$workdir/home" "$workdir/runtime" "$workdir/config" "$workdir/cache" "$workdir/data"
+chmod 700 "$workdir/runtime"
+
+set +e
+output="$(
+    HOME="$workdir/home" \
+    XDG_RUNTIME_DIR="$workdir/runtime" \
+    XDG_CONFIG_HOME="$workdir/config" \
+    XDG_CACHE_HOME="$workdir/cache" \
+    XDG_DATA_HOME="$workdir/data" \
+    QT_QPA_PLATFORM=offscreen \
+    QT_QUICK_BACKEND=software \
+    timeout 4s "$binary" 2>&1
+)"
+status=$?
+set -e
+
+printf '%s\n' "$output"
+
+if grep -Fq "QQmlApplicationEngine failed to load component" <<<"$output"; then
+    echo "QML application engine failed to load the root component" >&2
+    exit 1
+fi
+
+if grep -Fq "Type " <<<"$output" && grep -Fq " unavailable" <<<"$output"; then
+    echo "QML type dependency was unavailable during startup" >&2
+    exit 1
+fi
+
+if grep -Fq "Cannot assign to non-existent property" <<<"$output"; then
+    echo "QML assigned a non-existent property during startup" >&2
+    exit 1
+fi
+
+# A healthy GUI process is expected to remain alive until timeout in this headless smoke.
+if [[ $status -ne 124 ]]; then
+    echo "Ryofiles exited unexpectedly during startup smoke (status=$status)" >&2
+    exit 1
+fi
+
+echo "Ryofiles root QML instantiated successfully"