diff --git a/src/libstore/local-fs-store.hh b/src/libstore/local-fs-store.hh
index 27ef32ee94c..8fbd98db99d 100644
--- a/src/libstore/local-fs-store.hh
+++ b/src/libstore/local-fs-store.hh
@@ -20,7 +20,7 @@ struct LocalFSStoreConfig : LocalFSStoreConfigT<config::JustValue>
 {
     const Store::Config & storeConfig;
 
-    config::SettingDescriptionMap descriptions();
+    static config::SettingDescriptionMap descriptions();
 
     LocalFSStoreConfig(
         const Store::Config & storeConfig,
diff --git a/src/libstore/local-overlay-store.cc b/src/libstore/local-overlay-store.cc
index a1bf594cdb4..5f3d9281814 100644
--- a/src/libstore/local-overlay-store.cc
+++ b/src/libstore/local-overlay-store.cc
@@ -5,84 +5,88 @@
 #include "realisation.hh"
 #include "processes.hh"
 #include "url.hh"
-#include "store-open.hh"
+#include "store-api.hh"
 #include "store-registration.hh"
 #include "config-parse-impl.hh"
 
 namespace nix {
 
-LocalOverlayStore::Config::Descriptions::Descriptions()
-    : Store::Config::Descriptions{Store::Config::descriptions}
-    , LocalFSStore::Config::Descriptions{LocalFSStore::Config::descriptions}
-    , LocalStore::Config::Descriptions{LocalStore::Config::descriptions}
-    , LocalOverlayStoreConfigT<config::SettingInfo>{
-        .lowerStoreUri{
-            .name = "lower-store",
-            .description = R"(
-              [Store URL](@docroot@/command-ref/new-cli/nix3-help-stores.md#store-url-format)
-              for the lower store. The default is `auto` (i.e. use the Nix daemon or `/nix/store` directly).
-
-              Must be a store with a store dir on the file system.
-              Must be used as OverlayFS lower layer for this store's store dir.
-            )",
-        },
-        .upperLayer{
-            .name = "upper-layer",
-            .description = R"(
-              Directory containing the OverlayFS upper layer for this store's store dir.
-            )",
-        },
-        .checkMount{
-            .name = "check-mount",
-            .description = R"(
-              Check that the overlay filesystem is correctly mounted.
-
-              Nix does not manage the overlayfs mount point itself, but the correct
-              functioning of the overlay store does depend on this mount point being set up
-              correctly. Rather than just assume this is the case, check that the lowerdir
-              and upperdir options are what we expect them to be. This check is on by
-              default, but can be disabled if needed.
-            )",
-        },
-        .remountHook{
-            .name = "remount-hook",
-            .description = R"(
-              Script or other executable to run when overlay filesystem needs remounting.
-
-              This is occasionally necessary when deleting a store path that exists in both upper and lower layers.
-              In such a situation, bypassing OverlayFS and deleting the path in the upper layer directly
-              is the only way to perform the deletion without creating a "whiteout".
-              However this causes the OverlayFS kernel data structures to get out-of-sync,
-              and can lead to 'stale file handle' errors; remounting solves the problem.
-
-              The store directory is passed as an argument to the invoked executable.
-            )",
-        },
-    }
-{}
-
-
-const LocalOverlayStore::Config::Descriptions LocalOverlayStore::Config::descriptions{};
+static LocalOverlayStoreConfigT<config::SettingInfo> localOverlayStoreConfigDescriptions = {
+    .lowerStoreConfig{
+        .name = "lower-store",
+        .description = R"(
+          [Store URL](@docroot@/command-ref/new-cli/nix3-help-stores.md#store-url-format)
+          for the lower store. The default is `auto` (i.e. use the Nix daemon or `/nix/store` directly).
+
+          Must be a store with a store dir on the file system.
+          Must be used as OverlayFS lower layer for this store's store dir.
+        )",
+    },
+    .upperLayer{
+        .name = "upper-layer",
+        .description = R"(
+          Directory containing the OverlayFS upper layer for this store's store dir.
+        )",
+    },
+    .checkMount{
+        .name = "check-mount",
+        .description = R"(
+          Check that the overlay filesystem is correctly mounted.
+
+          Nix does not manage the overlayfs mount point itself, but the correct
+          functioning of the overlay store does depend on this mount point being set up
+          correctly. Rather than just assume this is the case, check that the lowerdir
+          and upperdir options are what we expect them to be. This check is on by
+          default, but can be disabled if needed.
+        )",
+    },
+    .remountHook{
+        .name = "remount-hook",
+        .description = R"(
+          Script or other executable to run when overlay filesystem needs remounting.
+
+          This is occasionally necessary when deleting a store path that exists in both upper and lower layers.
+          In such a situation, bypassing OverlayFS and deleting the path in the upper layer directly
+          is the only way to perform the deletion without creating a "whiteout".
+          However this causes the OverlayFS kernel data structures to get out-of-sync,
+          and can lead to 'stale file handle' errors; remounting solves the problem.
+
+          The store directory is passed as an argument to the invoked executable.
+        )",
+    },
+};
+
+#define LOCAL_OVERLAY_STORE_CONFIG_FIELDS(X) \
+    X(lowerStoreConfig), \
+    X(upperLayer), \
+    X(checkMount), \
+    X(remountHook),
+
+MAKE_PARSE(LocalOverlayStoreConfig, localOverlayStoreConfig, LOCAL_OVERLAY_STORE_CONFIG_FIELDS)
+
+static LocalOverlayStoreConfigT<config::JustValue> localOverlayStoreConfigDefaults()
+{
+    return {
+        .lowerStoreConfig = {make_ref<LocalStore::Config>(StoreReference::Params{})},
+        .upperLayer = {""},
+        .checkMount = {true},
+        .remountHook = {""},
+    };
+}
 
+MAKE_APPLY_PARSE(LocalOverlayStoreConfig, localOverlayStoreConfig, LOCAL_OVERLAY_STORE_CONFIG_FIELDS)
 
 LocalOverlayStore::Config::LocalOverlayStoreConfig(
     std::string_view scheme,
     std::string_view authority,
     const StoreReference::Params & params)
-    : Store::Config(params)
-    , LocalFSStore::Config(authority, params)
-    , LocalStore::Config(scheme, authority, params)
-    , LocalOverlayStoreConfigT<config::JustValue>{
-        CONFIG_ROW(lowerStoreUri, ""),
-        CONFIG_ROW(upperLayer, ""),
-        CONFIG_ROW(checkMount, true),
-        CONFIG_ROW(remountHook, ""),
-    }
+    : LocalStore::Config(scheme, authority, params)
+    , LocalOverlayStoreConfigT<config::JustValue>{localOverlayStoreConfigApplyParse(params)}
 {
 }
 
 
-std::string LocalOverlayStoreConfig::doc()
+std::string LocalOverlayStoreConfig::doc() const
 {
     return
         #include "local-overlay-store.md"
@@ -90,26 +94,24 @@ std::string LocalOverlayStoreConfig::doc()
 }
 
 
-Path LocalOverlayStoreConfig::toUpperPath(const StorePath & path) {
+Path LocalOverlayStoreConfig::toUpperPath(const StorePath & path) const
+{
     return upperLayer + "/" + path.to_string();
 }
 
 
-LocalOverlayStore::LocalOverlayStore(const Config & config)
-    : Store::Config{config}
-    , LocalFSStore::Config{config}
-    , LocalStore::Config{config}
-    , LocalOverlayStore::Config{config}
-    , Store{static_cast<const Store::Config &>(*this)}
-    , LocalFSStore{static_cast<const LocalFSStore::Config &>(*this)}
-    , LocalStore{static_cast<const LocalStore::Config &>(*this)}
-    , lowerStore(nix::openStore(lowerStoreUri.get()).dynamic_pointer_cast<LocalFSStore>())
+LocalOverlayStore::LocalOverlayStore(ref<const Config> config)
+    : Store{*config}
+    , LocalFSStore{*config}
+    , LocalStore{static_cast<ref<const LocalStore::Config>>(config)}
+    , config{config}
+    , lowerStore(config->lowerStoreConfig.value->openStore().dynamic_pointer_cast<LocalFSStore>())
 {
-    if (checkMount.get()) {
+    if (config->checkMount.get()) {
         std::smatch match;
         std::string mountInfo;
         auto mounts = readFile("/proc/self/mounts");
-        auto regex = std::regex(R"((^|\n)overlay )" + realStoreDir.get() + R"( .*(\n|$))");
+        auto regex = std::regex(R"((^|\n)overlay )" + config->realStoreDir.get() + R"( .*(\n|$))");
 
         // Mount points can be stacked, so there might be multiple matching entries.
         // Loop until the last match, which will be the current state of the mount point.
@@ -122,13 +124,13 @@ LocalOverlayStore::LocalOverlayStore(const Config & config)
             return std::regex_search(mountInfo, std::regex("\\b" + option + "=" + value + "( |,)"));
         };
 
-        auto expectedLowerDir = lowerStore->realStoreDir.get();
-        if (!checkOption("lowerdir", expectedLowerDir) || !checkOption("upperdir", upperLayer)) {
+        auto expectedLowerDir = lowerStore->config.realStoreDir.get();
+        if (!checkOption("lowerdir", expectedLowerDir) || !checkOption("upperdir", config->upperLayer)) {
             debug("expected lowerdir: %s", expectedLowerDir);
-            debug("expected upperdir: %s", upperLayer);
+            debug("expected upperdir: %s", config->upperLayer);
             debug("actual mount: %s", mountInfo);
             throw Error("overlay filesystem '%s' mounted incorrectly",
-                realStoreDir.get());
+                config->realStoreDir.get());
         }
     }
 }
@@ -278,14 +280,14 @@ void LocalOverlayStore::collectGarbage(const GCOptions & options, GCResults & re
 
 void LocalOverlayStore::deleteStorePath(const Path & path, uint64_t & bytesFreed)
 {
-    auto mergedDir = realStoreDir.get() + "/";
+    auto mergedDir = config->realStoreDir.get() + "/";
     if (path.substr(0, mergedDir.length()) != mergedDir) {
         warn("local-overlay: unexpected gc path '%s' ", path);
         return;
     }
 
     StorePath storePath = {path.substr(mergedDir.length())};
-    auto upperPath = toUpperPath(storePath);
+    auto upperPath = config->toUpperPath(storePath);
 
     if (pathExists(upperPath)) {
         debug("upper exists: %s", path);
@@ -334,7 +336,7 @@ LocalStore::VerificationResult LocalOverlayStore::verifyAllValidPaths(RepairFlag
     StorePathSet done;
 
     auto existsInStoreDir = [&](const StorePath & storePath) {
-        return pathExists(realStoreDir.get() + "/" + storePath.to_string());
+        return pathExists(config->realStoreDir.get() + "/" + storePath.to_string());
     };
 
     bool errors = false;
@@ -354,10 +356,10 @@ void LocalOverlayStore::remountIfNecessary()
 {
     if (!_remountRequired) return;
 
-    if (remountHook.get().empty()) {
-        warn("'%s' needs remounting, set remount-hook to do this automatically", realStoreDir.get());
+    if (config->remountHook.get().empty()) {
+        warn("'%s' needs remounting, set remount-hook to do this automatically", config->realStoreDir.get());
     } else {
-        runProgram(remountHook, false, {realStoreDir});
+        runProgram(config->remountHook, false, {config->realStoreDir});
     }
 
     _remountRequired = false;
diff --git a/src/libstore/local-overlay-store.hh b/src/libstore/local-overlay-store.hh
index 3d16c0c4695..112abd6be6b 100644
--- a/src/libstore/local-overlay-store.hh
+++ b/src/libstore/local-overlay-store.hh
@@ -6,7 +6,7 @@ namespace nix {
 template<template<typename> class F>
 struct LocalOverlayStoreConfigT
 {
-    const F<std::string> lowerStoreUri;
+    const F<ref<const StoreConfig>> lowerStoreConfig;
     const F<Path> upperLayer;
     const F<bool> checkMount;
     const F<Path> remountHook;
@@ -16,25 +16,17 @@ struct LocalOverlayStoreConfigT
  * Configuration for `LocalOverlayStore`.
  */
 struct LocalOverlayStoreConfig :
-    virtual LocalStoreConfig,
+    LocalStoreConfig,
     LocalOverlayStoreConfigT<config::JustValue>
 {
-    struct Descriptions :
-        virtual Store::Config::Descriptions,
-        virtual LocalStore::Config::Descriptions,
-        LocalOverlayStoreConfigT<config::SettingInfo>
-    {
-        Descriptions();
-    };
-
-    static const Descriptions descriptions;
+    static config::SettingDescriptionMap descriptions();
 
     LocalOverlayStoreConfig(
         std::string_view scheme,
         PathView path,
         const StoreReference::Params & params);
 
-    const std::string name() override { return "Experimental Local Overlay Store"; }
+    const std::string name() const override { return "Experimental Local Overlay Store"; }
 
     std::optional<ExperimentalFeature> experimentalFeature() const override
     {
@@ -46,7 +38,7 @@ struct LocalOverlayStoreConfig :
         return { "local-overlay" };
     }
 
-    std::string doc() override;
+    std::string doc() const override;
 
 protected:
     /**
@@ -57,7 +49,9 @@ protected:
      * at that file path. It might be stored in the lower layer instead,
      * or it might not be part of this store at all.
      */
-    Path toUpperPath(const StorePath & path);
+    Path toUpperPath(const StorePath & path) const;
+
+    friend struct LocalOverlayStore;
 };
 
 /**
@@ -66,11 +60,13 @@ protected:
  * Documentation on overridden methods states how they differ from their
  * `LocalStore` counterparts.
  */
-struct LocalOverlayStore : virtual LocalOverlayStoreConfig, virtual LocalStore
+struct LocalOverlayStore : virtual LocalStore
 {
     using Config = LocalOverlayStoreConfig;
 
-    LocalOverlayStore(const Config &);
+    ref<const Config> config;
+
+    LocalOverlayStore(ref<const Config>);
 
     std::string getUri() override
     {
diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index b16d56ebb3d..2572ed9e75a 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -108,7 +108,7 @@ LocalStore::Config::LocalStoreConfig(
 {
 }
 
-std::string LocalStoreConfig::doc()
+std::string LocalStoreConfig::doc() const
 {
     return
         #include "local-store.md"
diff --git a/src/libstore/local-store.hh b/src/libstore/local-store.hh
index e05d3cc3b85..fd72249abe0 100644
--- a/src/libstore/local-store.hh
+++ b/src/libstore/local-store.hh
@@ -58,12 +58,12 @@ struct LocalStoreConfig :
         std::string_view authority,
         const StoreReference::Params & params);
 
-    const std::string name() override { return "Local Store"; }
+    const std::string name() const override { return "Local Store"; }
 
     static std::set<std::string> uriSchemes()
     { return {"local"}; }
 
-    std::string doc() override;
+    std::string doc() const override;
 
     ref<Store> openStore() const override;
 };
diff --git a/src/libstore/remote-store.hh b/src/libstore/remote-store.hh
index d4a63de1f13..b79f68b3c53 100644
--- a/src/libstore/remote-store.hh
+++ b/src/libstore/remote-store.hh
@@ -21,22 +21,13 @@ template<typename T> class Pool;
 template<template<typename> class F>
 struct RemoteStoreConfigT
 {
-    const F<int> maxConnections;
-    const F<unsigned int> maxConnectionAge;
+    F<int> maxConnections;
+    F<unsigned int> maxConnectionAge;
 };
 
-struct RemoteStoreConfig :
-    virtual Store::Config,
-    RemoteStoreConfigT<config::JustValue>
+struct RemoteStoreConfig : RemoteStoreConfigT<config::JustValue>
 {
-    struct Descriptions :
-        virtual Store::Config::Descriptions,
-        RemoteStoreConfigT<config::SettingInfo>
-    {
-        Descriptions();
-    };
-
-    static const Descriptions descriptions;
+    static config::SettingDescriptionMap descriptions();
 
     RemoteStoreConfig(const StoreReference::Params &);
 };
@@ -46,13 +37,14 @@ struct RemoteStoreConfig :
  * DaemonStore.
  */
 struct RemoteStore :
-    public virtual RemoteStoreConfig,
     public virtual Store,
     public virtual GcStore,
     public virtual LogStore
 {
     using Config = RemoteStoreConfig;
 
+    const Config & config;
+
     RemoteStore(const Config & config);
 
     /* Implementations of abstract store API methods. */
diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index 675f09a1231..1629135b751 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -1307,7 +1307,7 @@ std::optional<ValidPathInfo> decodeValidPathInfo(const Store & store, std::istre
 }
 
 
-std::string MixStoreDirMethods::showPaths(const StorePathSet & paths)
+std::string MixStoreDirMethods::showPaths(const StorePathSet & paths) const
 {
     std::string s;
     for (auto & i : paths) {
diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index 206a35373db..87b8335430a 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -133,12 +133,12 @@ struct StoreConfig :
     /**
      * The name of this type of store.
      */
-    virtual const std::string name() = 0;
+    virtual const std::string name() const = 0;
 
     /**
      * Documentation for this type of store.
      */
-    virtual std::string doc()
+    virtual std::string doc() const
     {
         return "";
     }
@@ -897,3 +897,6 @@ std::map<DrvOutput, StorePath> drvOutputReferences(
     Store * evalStore = nullptr);
 
 }
+
+// Parses a Store URL, uses global state not pure so think about this
+JSON_IMPL(ref<const StoreConfig>)
diff --git a/src/libstore/store-dir-config.hh b/src/libstore/store-dir-config.hh
index f247f917a50..dae372147c9 100644
--- a/src/libstore/store-dir-config.hh
+++ b/src/libstore/store-dir-config.hh
@@ -64,7 +64,7 @@ struct MixStoreDirMethods
      * Display a set of paths in human-readable form (i.e., between quotes
      * and separated by commas).
      */
-    std::string showPaths(const StorePathSet & paths);
+    std::string showPaths(const StorePathSet & paths) const;
 
     /**
      * @return true if ‘path’ is in the Nix store (but not the Nix
diff --git a/src/libstore/store-registration.cc b/src/libstore/store-registration.cc
index 1f3edfc71c1..306416b2681 100644
--- a/src/libstore/store-registration.cc
+++ b/src/libstore/store-registration.cc
@@ -15,7 +15,6 @@ ref<Store> openStore(StoreReference && storeURI)
 {
     auto store = resolveStoreConfig(std::move(storeURI))->openStore();
 
-    experimentalFeatureSettings.require(store->experimentalFeature());
 #if 0 // FIXME
     store->warnUnknownSettings();
     store->init();
@@ -69,6 +68,8 @@ ref<StoreConfig> resolveStoreConfig(StoreReference && storeURI)
         },
         storeURI.variant);
 
+    experimentalFeatureSettings.require(storeConfig->experimentalFeature());
+
     return storeConfig;
 }
 
@@ -94,7 +95,9 @@ std::list<ref<Store>> getDefaultSubstituters()
         for (auto uri : settings.substituters.get())
             addStore(uri);
 
-        stores.sort([](ref<Store> & a, ref<Store> & b) { return a->priority < b->priority; });
+        stores.sort([](ref<Store> & a, ref<Store> & b) {
+            return a->resolvedSubstConfig.priority < b->resolvedSubstConfig.priority;
+        });
 
         return stores;
     }());
@@ -103,3 +106,54 @@ std::list<ref<Store>> getDefaultSubstituters()
 }
 
 }
+
+namespace nlohmann {
+
+using namespace nix::config;
+
+ref<const StoreConfig> adl_serializer<ref<const StoreConfig>>::from_json(const json & json)
+{
+    StoreReference ref;
+    switch (json.type()) {
+
+    case json::value_t::string: {
+        ref = StoreReference::parse(json.get_ref<const std::string &>());
+        break;
+    }
+
+    case json::value_t::object: {
+        auto & obj = json.get_ref<const json::object_t &>();
+        ref = StoreReference {
+            .variant = StoreReference::Specified{
+                .scheme = getString(valueAt(obj, "scheme")),
+                .authority = getString(valueAt(obj, "authority")),
+            },
+            .params = obj,
+        };
+        break;
+    }
+
+    case json::value_t::null:
+    case json::value_t::number_unsigned:
+    case json::value_t::number_integer:
+    case json::value_t::number_float:
+    case json::value_t::boolean:
+    case json::value_t::array:
+    case json::value_t::binary:
+    case json::value_t::discarded:
+    default:
+        throw UsageError(
+            "Invalid JSON for Store configuration: is type '%s' but must be string or object",
+            json.type_name());
+    };
+
+    return resolveStoreConfig(std::move(ref));
+}
+
+void adl_serializer<ref<const StoreConfig>>::to_json(json & obj, ref<const StoreConfig> s)
+{
+    // TODO, for tests maybe
+    assert(false);
+}
+
+}
diff --git a/src/libstore/uds-remote-store.hh b/src/libstore/uds-remote-store.hh
index 4af4eac624e..a584bb90385 100644
--- a/src/libstore/uds-remote-store.hh
+++ b/src/libstore/uds-remote-store.hh
@@ -8,17 +8,12 @@
 namespace nix {
 
 struct UDSRemoteStoreConfig :
-    virtual LocalFSStore::Config,
-    virtual RemoteStore::Config
+    std::enable_shared_from_this<UDSRemoteStoreConfig>,
+    Store::Config,
+    LocalFSStore::Config,
+    RemoteStore::Config
 {
-    struct Descriptions :
-        virtual LocalFSStore::Config::Descriptions,
-        virtual RemoteStore::Config::Descriptions
-    {
-        Descriptions();
-    };
-
-    static const Descriptions descriptions;
+    static config::SettingDescriptionMap descriptions();
 
     UDSRemoteStoreConfig(const StoreReference::Params & params)
         : UDSRemoteStoreConfig{"unix", "", params}
@@ -32,9 +27,9 @@ struct UDSRemoteStoreConfig :
         std::string_view authority,
         const StoreReference::Params & params);
 
-    const std::string name() override { return "Local Daemon Store"; }
+    const std::string name() const override { return "Local Daemon Store"; }
 
-    std::string doc() override;
+    std::string doc() const override;
 
     /**
      * The path to the unix domain socket.
@@ -51,12 +46,13 @@ struct UDSRemoteStoreConfig :
 };
 
 struct UDSRemoteStore :
-    virtual UDSRemoteStoreConfig,
     virtual IndirectRootStore,
     virtual RemoteStore
 {
     using Config = UDSRemoteStoreConfig;
 
+    ref<const Config> config;
+
     UDSRemoteStore(const Config &);
 
     std::string getUri() override;