diff --git a/src/libostree/ostree-bootconfig-parser-private.h b/src/libostree/ostree-bootconfig-parser-private.h
index 16ccb0fcdc..1450fa9921 100644
--- a/src/libostree/ostree-bootconfig-parser-private.h
+++ b/src/libostree/ostree-bootconfig-parser-private.h
@@ -8,4 +8,6 @@ G_BEGIN_DECLS
 
 const char *_ostree_bootconfig_parser_filename (OstreeBootconfigParser *self);
 
+GVariant *_ostree_bootconfig_parser_get_extra_keys_variant (OstreeBootconfigParser *self);
+
 G_END_DECLS
diff --git a/src/libostree/ostree-bootconfig-parser.c b/src/libostree/ostree-bootconfig-parser.c
index 2e08256d72..4e7c823a59 100644
--- a/src/libostree/ostree-bootconfig-parser.c
+++ b/src/libostree/ostree-bootconfig-parser.c
@@ -339,6 +339,60 @@ ostree_bootconfig_parser_write (OstreeBootconfigParser *self, GFile *output,
                                             cancellable, error);
 }
 
+/* Standard BLS keys that are managed by ostree's own deployment code.
+ * These are rebuilt from scratch during staged deployment finalization
+ * (title, version, linux, initrd from the deployment; options from the
+ * serialized kargs), so they must NOT be duplicated into bootconfig-extra.
+ */
+static const char *const standard_bls_keys[]
+    = { "title", "version", "options", "linux", "initrd", "devicetree", NULL };
+
+static gboolean
+is_standard_bls_key (const char *key)
+{
+  for (const char *const *p = standard_bls_keys; *p != NULL; p++)
+    {
+      if (strcmp (key, *p) == 0)
+        return TRUE;
+    }
+  return FALSE;
+}
+
+/**
+ * _ostree_bootconfig_parser_get_extra_keys_variant:
+ * @self: Parser
+ *
+ * Returns a GVariant of type "a{ss}" containing all bootconfig keys
+ * that are not part of the standard BLS set managed by ostree.  These
+ * are extension keys set by consumers like bootc (e.g.
+ * "x-options-source-tuned") that need to survive the staged deployment
+ * serialization roundtrip.
+ *
+ * Returns: (transfer full) (nullable): A new floating GVariant, or NULL if
+ *          there are no extra keys
+ */
+GVariant *
+_ostree_bootconfig_parser_get_extra_keys_variant (OstreeBootconfigParser *self)
+{
+  g_auto (GVariantBuilder) builder = OT_VARIANT_BUILDER_INITIALIZER;
+  gboolean has_entries = FALSE;
+
+  g_variant_builder_init (&builder, (GVariantType *)"a{ss}");
+
+  GLNX_HASH_TABLE_FOREACH_KV (self->options, const char *, k, const char *, v)
+    {
+      if (is_standard_bls_key (k))
+        continue;
+      g_variant_builder_add (&builder, "{ss}", k, v);
+      has_entries = TRUE;
+    }
+
+  if (!has_entries)
+    return NULL;
+
+  return g_variant_builder_end (&builder);
+}
+
 static void
 ostree_bootconfig_parser_finalize (GObject *object)
 {
diff --git a/src/libostree/ostree-sysroot-deploy.c b/src/libostree/ostree-sysroot-deploy.c
index 1dbaaa7e9d..77b601ff42 100644
--- a/src/libostree/ostree-sysroot-deploy.c
+++ b/src/libostree/ostree-sysroot-deploy.c
@@ -3884,6 +3884,33 @@ ostree_sysroot_stage_tree_with_options (OstreeSysroot *self, const char *osname,
     g_variant_builder_add (builder, "{sv}", "overlay-initrds",
                            g_variant_new_strv ((const char *const *)opts->overlay_initrds, -1));
 
+  /* Serialize any extension BLS keys (e.g. x-options-source-tuned).
+   * These are custom keys set by consumers like bootc and need to survive
+   * the staging roundtrip so they are preserved during finalization at shutdown.
+   *
+   * First check the new deployment's bootconfig (in case the caller set keys
+   * on it directly).  If none found, fall back to the merge deployment's
+   * bootconfig, which carries the keys from the currently deployed BLS entry.
+   * This ensures that x-prefixed keys are inherited across staged deployments
+   * even though _ostree_deployment_set_bootconfig_from_kargs() creates a fresh
+   * bootconfig containing only the "options" key.
+   */
+  {
+    GVariant *extra = NULL;
+    OstreeBootconfigParser *bootconfig = ostree_deployment_get_bootconfig (deployment);
+    if (bootconfig)
+      extra = _ostree_bootconfig_parser_get_extra_keys_variant (bootconfig);
+    if (!extra && merge_deployment)
+      {
+        OstreeBootconfigParser *merge_bootconfig
+            = ostree_deployment_get_bootconfig (merge_deployment);
+        if (merge_bootconfig)
+          extra = _ostree_bootconfig_parser_get_extra_keys_variant (merge_bootconfig);
+      }
+    if (extra)
+      g_variant_builder_add (builder, "{sv}", "bootconfig-extra", extra);
+  }
+
   const char *parent = dirname (strdupa (_OSTREE_SYSROOT_RUNSTATE_STAGED));
   if (!glnx_shutil_mkdir_p_at (AT_FDCWD, parent, 0755, cancellable, error))
     return FALSE;
diff --git a/src/libostree/ostree-sysroot.c b/src/libostree/ostree-sysroot.c
index 282df6d100..5b837bb2f7 100644
--- a/src/libostree/ostree-sysroot.c
+++ b/src/libostree/ostree-sysroot.c
@@ -1225,6 +1225,24 @@ _ostree_sysroot_reload_staged (OstreeSysroot *self, GError **error)
 
           _ostree_deployment_set_overlay_initrds (staged, overlay_initrds);
 
+          /* Restore any extension BLS keys (e.g. x-options-source-tuned)
+           * that were serialized during staging. This preserves custom keys
+           * set by consumers like bootc through the staging roundtrip.
+           */
+          {
+            g_autoptr (GVariant) bootconfig_extra = NULL;
+            if (g_variant_dict_lookup (staged_deployment_dict, "bootconfig-extra", "@a{ss}",
+                                       &bootconfig_extra))
+              {
+                OstreeBootconfigParser *bootconfig = ostree_deployment_get_bootconfig (staged);
+                GVariantIter iter;
+                const char *key, *value;
+                g_variant_iter_init (&iter, bootconfig_extra);
+                while (g_variant_iter_next (&iter, "{&s&s}", &key, &value))
+                  ostree_bootconfig_parser_set (bootconfig, key, value);
+              }
+          }
+
           self->staged_deployment = g_steal_pointer (&staged);
           self->staged_deployment_data = g_steal_pointer (&staged_deployment_data);
           /* We set this flag for ostree_deployment_is_staged() because that API
diff --git a/tests/test-bootconfig-parser-internals.c b/tests/test-bootconfig-parser-internals.c
index 00b18d4a17..d84c4a3be0 100644
--- a/tests/test-bootconfig-parser-internals.c
+++ b/tests/test-bootconfig-parser-internals.c
@@ -49,6 +49,211 @@ test_parse_tries_invalid (void)
   g_assert_cmpuint (done, ==, 0);
 }
 
+static void
+test_extra_keys_variant_empty (void)
+{
+  /* A bootconfig with no x-prefixed keys should return NULL */
+  OstreeBootconfigParser *parser = ostree_bootconfig_parser_new ();
+  ostree_bootconfig_parser_set (parser, "title", "Fedora Linux 43");
+  ostree_bootconfig_parser_set (parser, "version", "1");
+  ostree_bootconfig_parser_set (parser, "options", "root=UUID=abc rw quiet");
+  ostree_bootconfig_parser_set (parser, "linux", "/vmlinuz-6.8.0");
+  ostree_bootconfig_parser_set (parser, "initrd", "/initramfs-6.8.0.img");
+
+  GVariant *extra = _ostree_bootconfig_parser_get_extra_keys_variant (parser);
+  g_assert_null (extra);
+
+  g_object_unref (parser);
+}
+
+static void
+test_extra_keys_variant_with_extension_keys (void)
+{
+  /* Standard keys should be excluded, only extension keys returned */
+  OstreeBootconfigParser *parser = ostree_bootconfig_parser_new ();
+  ostree_bootconfig_parser_set (parser, "title", "Fedora Linux 43");
+  ostree_bootconfig_parser_set (parser, "options", "root=UUID=abc rw");
+  ostree_bootconfig_parser_set (parser, "linux", "/vmlinuz-6.8.0");
+  ostree_bootconfig_parser_set (parser, "x-options-source-tuned", "nohz=full isolcpus=1-3");
+  ostree_bootconfig_parser_set (parser, "x-options-source-dracut", "rd.driver.pre=vfio-pci");
+
+  GVariant *extra = _ostree_bootconfig_parser_get_extra_keys_variant (parser);
+  g_assert_nonnull (extra);
+
+  GVariant *extra_owned = g_variant_ref_sink (extra);
+
+  /* Should be a{ss} with exactly 2 entries */
+  g_assert_true (g_variant_is_of_type (extra_owned, G_VARIANT_TYPE ("a{ss}")));
+  g_assert_cmpuint (g_variant_n_children (extra_owned), ==, 2);
+
+  /* Verify the contents */
+  GVariantIter iter;
+  const char *key, *val;
+  gboolean found_tuned = FALSE, found_dracut = FALSE;
+  g_variant_iter_init (&iter, extra_owned);
+  while (g_variant_iter_next (&iter, "{&s&s}", &key, &val))
+    {
+      if (g_str_equal (key, "x-options-source-tuned"))
+        {
+          g_assert_cmpstr (val, ==, "nohz=full isolcpus=1-3");
+          found_tuned = TRUE;
+        }
+      else if (g_str_equal (key, "x-options-source-dracut"))
+        {
+          g_assert_cmpstr (val, ==, "rd.driver.pre=vfio-pci");
+          found_dracut = TRUE;
+        }
+      else
+        {
+          g_assert_not_reached ();
+        }
+    }
+  g_assert_true (found_tuned);
+  g_assert_true (found_dracut);
+
+  g_variant_unref (extra_owned);
+  g_object_unref (parser);
+}
+
+static void
+test_extra_keys_variant_standard_excluded (void)
+{
+  /* Standard BLS keys (title, version, options, linux, initrd, devicetree)
+   * should be excluded. All other keys should be preserved.
+   */
+  OstreeBootconfigParser *parser = ostree_bootconfig_parser_new ();
+  ostree_bootconfig_parser_set (parser, "title", "Test");
+  ostree_bootconfig_parser_set (parser, "version", "1.0");
+  ostree_bootconfig_parser_set (parser, "options", "root=UUID=abc");
+  ostree_bootconfig_parser_set (parser, "linux", "/vmlinuz");
+  ostree_bootconfig_parser_set (parser, "initrd", "/initramfs.img");
+  ostree_bootconfig_parser_set (parser, "devicetree", "/dtb");
+
+  /* Only standard keys -- should return NULL */
+  GVariant *extra = _ostree_bootconfig_parser_get_extra_keys_variant (parser);
+  g_assert_null (extra);
+
+  /* Add non-standard keys -- all should be preserved */
+  ostree_bootconfig_parser_set (parser, "my-custom-key", "some-value");
+  ostree_bootconfig_parser_set (parser, "x-options-source-tuned", "nohz=full");
+
+  extra = _ostree_bootconfig_parser_get_extra_keys_variant (parser);
+  g_assert_nonnull (extra);
+  GVariant *extra_owned = g_variant_ref_sink (extra);
+
+  g_assert_cmpuint (g_variant_n_children (extra_owned), ==, 2);
+
+  GVariantIter iter;
+  const char *key, *val;
+  gboolean found_custom = FALSE, found_tuned = FALSE;
+  g_variant_iter_init (&iter, extra_owned);
+  while (g_variant_iter_next (&iter, "{&s&s}", &key, &val))
+    {
+      if (g_str_equal (key, "my-custom-key"))
+        {
+          g_assert_cmpstr (val, ==, "some-value");
+          found_custom = TRUE;
+        }
+      else if (g_str_equal (key, "x-options-source-tuned"))
+        {
+          g_assert_cmpstr (val, ==, "nohz=full");
+          found_tuned = TRUE;
+        }
+      else
+        g_assert_not_reached ();
+    }
+  g_assert_true (found_custom);
+  g_assert_true (found_tuned);
+
+  g_variant_unref (extra_owned);
+  g_object_unref (parser);
+}
+
+static void
+test_extra_keys_roundtrip (void)
+{
+  /* Test that extra keys can be serialized to a variant and restored */
+  OstreeBootconfigParser *original = ostree_bootconfig_parser_new ();
+  ostree_bootconfig_parser_set (original, "options", "root=UUID=abc rw");
+  ostree_bootconfig_parser_set (original, "linux", "/vmlinuz");
+  ostree_bootconfig_parser_set (original, "x-options-source-tuned", "nohz=full isolcpus=1-3");
+
+  /* Serialize */
+  GVariant *extra = _ostree_bootconfig_parser_get_extra_keys_variant (original);
+  g_assert_nonnull (extra);
+  GVariant *extra_owned = g_variant_ref_sink (extra);
+
+  /* Create a new parser (simulating deserialization) with only standard keys */
+  OstreeBootconfigParser *restored = ostree_bootconfig_parser_new ();
+  ostree_bootconfig_parser_set (restored, "options", "root=UUID=abc rw nohz=full isolcpus=1-3");
+
+  /* Restore extra keys from variant */
+  GVariantIter iter;
+  const char *key, *value;
+  g_variant_iter_init (&iter, extra_owned);
+  while (g_variant_iter_next (&iter, "{&s&s}", &key, &value))
+    ostree_bootconfig_parser_set (restored, key, value);
+
+  /* Verify the extension key survived the roundtrip */
+  g_assert_cmpstr (ostree_bootconfig_parser_get (restored, "x-options-source-tuned"), ==,
+                   "nohz=full isolcpus=1-3");
+  /* Standard keys should also be present */
+  g_assert_cmpstr (ostree_bootconfig_parser_get (restored, "options"), ==,
+                   "root=UUID=abc rw nohz=full isolcpus=1-3");
+
+  g_variant_unref (extra_owned);
+  g_object_unref (original);
+  g_object_unref (restored);
+}
+
+static void
+test_extra_keys_parse_write_roundtrip (void)
+{
+  /* Test that x-prefixed keys survive a parse -> write -> parse roundtrip
+   * via the BLS file format.
+   */
+  const char *bls_content = "title Fedora Linux 43\n"
+                            "version 6.8.0-300.fc40.x86_64\n"
+                            "linux /vmlinuz-6.8.0\n"
+                            "initrd /initramfs-6.8.0.img\n"
+                            "options root=UUID=abc rw nohz=full\n"
+                            "x-options-source-tuned nohz=full\n";
+
+  /* Write the BLS content to a temp file */
+  g_autofree char *tmpdir = g_dir_make_tmp ("ostree-test-XXXXXX", NULL);
+  g_assert_nonnull (tmpdir);
+  g_autofree char *tmpfile = g_build_filename (tmpdir, "ostree-test.conf", NULL);
+  g_assert_true (g_file_set_contents (tmpfile, bls_content, -1, NULL));
+
+  /* Parse */
+  OstreeBootconfigParser *parser = ostree_bootconfig_parser_new ();
+  g_assert_true (ostree_bootconfig_parser_parse_at (parser, AT_FDCWD, tmpfile, NULL, NULL));
+
+  /* The x-prefixed key should have been parsed */
+  g_assert_cmpstr (ostree_bootconfig_parser_get (parser, "x-options-source-tuned"), ==,
+                   "nohz=full");
+  g_assert_cmpstr (ostree_bootconfig_parser_get (parser, "options"), ==,
+                   "root=UUID=abc rw nohz=full");
+
+  /* Write it back out */
+  g_autofree char *outfile = g_build_filename (tmpdir, "ostree-test-out.conf", NULL);
+  g_assert_true (ostree_bootconfig_parser_write_at (parser, AT_FDCWD, outfile, NULL, NULL));
+
+  /* Parse the output and verify the key survived */
+  OstreeBootconfigParser *parser2 = ostree_bootconfig_parser_new ();
+  g_assert_true (ostree_bootconfig_parser_parse_at (parser2, AT_FDCWD, outfile, NULL, NULL));
+  g_assert_cmpstr (ostree_bootconfig_parser_get (parser2, "x-options-source-tuned"), ==,
+                   "nohz=full");
+  g_assert_cmpstr (ostree_bootconfig_parser_get (parser2, "options"), ==,
+                   "root=UUID=abc rw nohz=full");
+
+  g_object_unref (parser);
+  g_object_unref (parser2);
+  (void)unlink (tmpfile);
+  (void)unlink (outfile);
+  (void)rmdir (tmpdir);
+}
+
 int
 main (int argc, char *argv[])
 {
@@ -56,5 +261,13 @@ main (int argc, char *argv[])
 
   g_test_add_func ("/bootconfig-parser/tries/valid", test_parse_tries_valid);
   g_test_add_func ("/bootconfig-parser/tries/invalid", test_parse_tries_invalid);
+  g_test_add_func ("/bootconfig-parser/extra-keys/empty", test_extra_keys_variant_empty);
+  g_test_add_func ("/bootconfig-parser/extra-keys/with-extension-keys",
+                   test_extra_keys_variant_with_extension_keys);
+  g_test_add_func ("/bootconfig-parser/extra-keys/standard-excluded",
+                   test_extra_keys_variant_standard_excluded);
+  g_test_add_func ("/bootconfig-parser/extra-keys/roundtrip", test_extra_keys_roundtrip);
+  g_test_add_func ("/bootconfig-parser/extra-keys/parse-write-roundtrip",
+                   test_extra_keys_parse_write_roundtrip);
   return g_test_run ();
 }