diff --git a/gpt4all-chat/CMakeLists.txt b/gpt4all-chat/CMakeLists.txt
index bf987db8..d29af3ef 100644
--- a/gpt4all-chat/CMakeLists.txt
+++ b/gpt4all-chat/CMakeLists.txt
@@ -245,6 +245,7 @@ qt_add_executable(chat
     src/llmodel_ollama.cpp        src/llmodel_ollama.h
     src/llmodel_openai.cpp        src/llmodel_openai.h
     src/llmodel_provider.cpp      src/llmodel_provider.h
+    src/llmodel_provider_builtins.cpp
     src/localdocs.cpp             src/localdocs.h
     src/localdocsmodel.cpp        src/localdocsmodel.h
     src/logger.cpp                src/logger.h
diff --git a/gpt4all-chat/src/chatllm.cpp b/gpt4all-chat/src/chatllm.cpp
index b5491727..8eb4ba99 100644
--- a/gpt4all-chat/src/chatllm.cpp
+++ b/gpt4all-chat/src/chatllm.cpp
@@ -330,10 +330,8 @@ void ChatLLM::trySwitchContextOfLoadedModel(const ModelInfo &modelInfo)
     emit trySwitchContextOfLoadedModelCompleted(0);
 }
 
-// TODO: always call with a resource guard held since this didn't previously use coroutines
 auto ChatLLM::loadModel(const ModelInfo &modelInfo) -> QCoro::Task<bool>
 {
-    // TODO: get the description from somewhere
     bool alreadyAcquired = isModelLoaded();
     if (alreadyAcquired && *modelInfo.modelDesc() == *m_modelInfo.modelDesc()) {
         // already acquired -> keep it
diff --git a/gpt4all-chat/src/llmodel_chat.h b/gpt4all-chat/src/llmodel_chat.h
index a44ec3c4..0e9ba155 100644
--- a/gpt4all-chat/src/llmodel_chat.h
+++ b/gpt4all-chat/src/llmodel_chat.h
@@ -19,7 +19,6 @@ struct ChatResponseMetadata {
     int nResponseTokens;
 };
 
-// TODO: implement two of these; one based on Ollama (TBD) and the other based on OpenAI (chatapi.h)
 class ChatLLMInstance {
 public:
     virtual ~ChatLLMInstance() noexcept = 0;
diff --git a/gpt4all-chat/src/llmodel_description.h b/gpt4all-chat/src/llmodel_description.h
index 56004a31..fc2811fb 100644
--- a/gpt4all-chat/src/llmodel_description.h
+++ b/gpt4all-chat/src/llmodel_description.h
@@ -15,12 +15,14 @@ namespace gpt4all::ui {
 
 class ChatLLMInstance;
 
-// TODO: implement shared_from_this guidance for restricted construction
 class ModelDescription : public std::enable_shared_from_this<ModelDescription> {
     Q_GADGET
     Q_PROPERTY(const ModelProvider *provider READ provider CONSTANT)
     Q_PROPERTY(QVariant             key      READ key      CONSTANT)
 
+protected:
+    struct protected_t { explicit protected_t() = default; };
+
 public:
     virtual ~ModelDescription() noexcept = 0;
 
diff --git a/gpt4all-chat/src/llmodel_ollama.cpp b/gpt4all-chat/src/llmodel_ollama.cpp
index 56bea6aa..a05a1556 100644
--- a/gpt4all-chat/src/llmodel_ollama.cpp
+++ b/gpt4all-chat/src/llmodel_ollama.cpp
@@ -34,14 +34,17 @@ auto OllamaProvider::makeGenerationParams(const QMap<GenerationParam, QVariant>
 { return new OllamaGenerationParams(values); }
 
 /// load
-OllamaProviderCustom::OllamaProviderCustom(std::shared_ptr<ProviderStore> store, QUuid id)
-    : ModelProvider(std::move(id))
+OllamaProviderCustom::OllamaProviderCustom(std::shared_ptr<ProviderStore> store, QUuid id, QString name, QUrl baseUrl)
+    : ModelProvider      (std::move(id), std::move(name), std::move(baseUrl))
     , ModelProviderCustom(std::move(store))
-{ load(); }
+{
+    if (auto res = m_store->acquire(m_id); !res)
+        res.error().raise();
+}
 
 /// create
 OllamaProviderCustom::OllamaProviderCustom(std::shared_ptr<ProviderStore> store, QString name, QUrl baseUrl)
-    : ModelProvider(std::move(name), std::move(baseUrl))
+    : ModelProvider      (std::move(name), std::move(baseUrl))
     , ModelProviderCustom(std::move(store))
 {
     auto data = m_store->create(m_name, m_baseUrl);
@@ -50,8 +53,20 @@ OllamaProviderCustom::OllamaProviderCustom(std::shared_ptr<ProviderStore> store,
     m_id = (*data)->id;
 }
 
-OllamaModelDescription::OllamaModelDescription(std::shared_ptr<const OllamaProvider> provider, QByteArray modelHash)
-    : m_provider(std::move(provider))
+auto OllamaProviderCustom::asData() -> ModelProviderData
+{
+    return {
+        .id               = m_id,
+        .builtin          = false,
+        .type             = ProviderType::ollama,
+        .custom_details   = CustomProviderDetails { m_name, m_baseUrl },
+        .provider_details = {},
+    };
+}
+
+OllamaModelDescription::OllamaModelDescription(protected_t, std::shared_ptr<const OllamaProvider> provider,
+                                               QByteArray modelHash)
+    : m_provider (std::move(provider ))
     , m_modelHash(std::move(modelHash))
     {}
 
@@ -63,7 +78,7 @@ auto OllamaModelDescription::newInstanceImpl(QNetworkAccessManager *nam) const -
 
 OllamaChatModel::OllamaChatModel(std::shared_ptr<const OllamaModelDescription> description, QNetworkAccessManager *nam)
     : m_description(std::move(description))
-    , m_nam(nam)
+    , m_nam        (nam                   )
     {}
 
 auto OllamaChatModel::preload() -> QCoro::Task<>
diff --git a/gpt4all-chat/src/llmodel_ollama.h b/gpt4all-chat/src/llmodel_ollama.h
index 761b4db0..bfd94334 100644
--- a/gpt4all-chat/src/llmodel_ollama.h
+++ b/gpt4all-chat/src/llmodel_ollama.h
@@ -50,8 +50,10 @@ public:
     auto makeGenerationParams(const QMap<GenerationParam, QVariant> &values) const -> OllamaGenerationParams * override;
 };
 
-class OllamaProviderBuiltin : public OllamaProvider, public ModelProviderBuiltin {
+class OllamaProviderBuiltin : public OllamaProvider {
     Q_GADGET
+    Q_PROPERTY(QString name    READ name    CONSTANT)
+    Q_PROPERTY(QUrl    baseUrl READ baseUrl CONSTANT)
 
 public:
     /// Create a new built-in Ollama provider (transient).
@@ -64,18 +66,17 @@ class OllamaProviderCustom final : public OllamaProvider, public ModelProviderCu
 
 public:
     /// Load an existing OllamaProvider from disk.
-    explicit OllamaProviderCustom(std::shared_ptr<ProviderStore> store, QUuid id);
+    explicit OllamaProviderCustom(ProviderStore *store, QUuid id, QString name, QUrl baseUrl);
 
     /// Create a new OllamaProvider on disk.
-    explicit OllamaProviderCustom(std::shared_ptr<ProviderStore> store, QString name, QUrl baseUrl);
+    explicit OllamaProviderCustom(ProviderStore *store, QString name, QUrl baseUrl);
 
 Q_SIGNALS:
     void nameChanged   (const QString &value);
     void baseUrlChanged(const QUrl    &value);
 
 protected:
-    auto asData() -> ModelProviderData override
-    { return { m_id, ProviderType::ollama, m_name, m_baseUrl, {} }; }
+    auto asData() -> ModelProviderData override;
 };
 
 class OllamaModelDescription : public ModelDescription {
@@ -83,7 +84,11 @@ class OllamaModelDescription : public ModelDescription {
     Q_PROPERTY(QByteArray modelHash READ modelHash CONSTANT)
 
 public:
-    explicit OllamaModelDescription(std::shared_ptr<const OllamaProvider> provider, QByteArray modelHash);
+    explicit OllamaModelDescription(protected_t, std::shared_ptr<const OllamaProvider> provider, QByteArray modelHash);
+
+    static auto create(std::shared_ptr<const OllamaProvider> provider, QByteArray modelHash)
+        -> std::shared_ptr<OllamaModelDescription>
+    { return std::make_shared<OllamaModelDescription>(protected_t(), std::move(provider), std::move(modelHash)); }
 
     // getters
     [[nodiscard]] auto              provider () const -> const OllamaProvider * override { return m_provider.get(); }
diff --git a/gpt4all-chat/src/llmodel_openai.cpp b/gpt4all-chat/src/llmodel_openai.cpp
index 53b51e85..d47dfb43 100644
--- a/gpt4all-chat/src/llmodel_openai.cpp
+++ b/gpt4all-chat/src/llmodel_openai.cpp
@@ -96,23 +96,38 @@ auto OpenaiProvider::makeGenerationParams(const QMap<GenerationParam, QVariant>
     -> OpenaiGenerationParams *
 { return new OpenaiGenerationParams(values); }
 
-OpenaiProviderBuiltin::OpenaiProviderBuiltin(QUuid id, QString name, QUrl baseUrl, QString apiKey)
+OpenaiProviderBuiltin::OpenaiProviderBuiltin(ProviderStore *store, QUuid id, QString name, QUrl baseUrl)
     : ModelProvider(std::move(id), std::move(name), std::move(baseUrl))
-    , OpenaiProvider(std::move(apiKey))
-    {}
-
-/// load
-OpenaiProviderCustom::OpenaiProviderCustom(std::shared_ptr<ProviderStore> store, QUuid id)
-    : ModelProvider(std::move(id))
-    , ModelProviderCustom(std::move(store))
+    , ModelProviderMutable(store)
 {
-    auto &details = load();
-    m_apiKey = std::get<OpenaiProviderDetails>(details).api_key;
+    auto res = m_store->acquire(m_id);
+    if (!res)
+        res.error().raise();
+    if (auto maybeData = *res) {
+        auto &details = (*maybeData)->openai_details.value();
+        m_apiKey = details.api_key;
+    }
 }
 
+auto OpenaiProviderBuiltin::asData() -> ModelProviderData
+{
+    return {
+        .id             = m_id,
+        .type           = ProviderType::openai,
+        .custom_details = {},
+        .openai_details = OpenaiProviderDetails { m_apiKey },
+    };
+}
+
+/// load
+OpenaiProviderCustom::OpenaiProviderCustom(ProviderStore *store, QUuid id, QString name, QUrl baseUrl, QString apiKey)
+    : ModelProvider(std::move(id), std::move(name), std::move(baseUrl))
+    , OpenaiProvider(std::move(apiKey))
+    , ModelProviderCustom(store)
+    {}
+
 /// create
-OpenaiProviderCustom::OpenaiProviderCustom(std::shared_ptr<ProviderStore> store, QString name, QUrl baseUrl,
-                                           QString apiKey)
+OpenaiProviderCustom::OpenaiProviderCustom(ProviderStore *store, QString name, QUrl baseUrl, QString apiKey)
     : ModelProvider(std::move(name), std::move(baseUrl))
     , ModelProviderCustom(std::move(store))
     , OpenaiProvider(std::move(apiKey))
@@ -123,8 +138,19 @@ OpenaiProviderCustom::OpenaiProviderCustom(std::shared_ptr<ProviderStore> store,
     m_id = (*data)->id;
 }
 
-OpenaiModelDescription::OpenaiModelDescription(std::shared_ptr<const OpenaiProvider> provider, QString modelName)
-    : m_provider(std::move(provider))
+auto OpenaiProviderCustom::asData() -> ModelProviderData
+{
+    return {
+        .id             = m_id,
+        .type           = ProviderType::openai,
+        .custom_details = CustomProviderDetails { m_name, m_baseUrl },
+        .openai_details = OpenaiProviderDetails { m_apiKey          },
+    };
+}
+
+OpenaiModelDescription::OpenaiModelDescription(protected_t, std::shared_ptr<const OpenaiProvider> provider,
+                                               QString modelName)
+    : m_provider (std::move(provider ))
     , m_modelName(std::move(modelName))
     {}
 
diff --git a/gpt4all-chat/src/llmodel_openai.h b/gpt4all-chat/src/llmodel_openai.h
index 28c2cee9..a5a9fa6e 100644
--- a/gpt4all-chat/src/llmodel_openai.h
+++ b/gpt4all-chat/src/llmodel_openai.h
@@ -42,12 +42,13 @@ protected:
 
 class OpenaiProvider : public QObject, public virtual ModelProvider {
     Q_OBJECT
+    Q_PROPERTY(QString apiKey READ apiKey WRITE setApiKey NOTIFY apiKeyChanged)
 
 protected:
-    explicit OpenaiProvider() = default; // custom
-    explicit OpenaiProvider(QString apiKey) // built-in
-        : m_apiKey(std::move(apiKey))
-        {}
+    explicit OpenaiProvider() = default;
+    explicit OpenaiProvider(QString apiKey)
+        : m_apiKey(std::move(apiKey)) {}
+
 public:
     ~OpenaiProvider() noexcept override = 0;
 
@@ -56,6 +57,8 @@ public:
 
     [[nodiscard]] const QString &apiKey() const { return m_apiKey; }
 
+    virtual void setApiKey(QString value) = 0;
+
     auto supportedGenerationParams() const -> QSet<GenerationParam> override;
     auto makeGenerationParams(const QMap<GenerationParam, QVariant> &values) const -> OpenaiGenerationParams * override;
 
@@ -63,28 +66,32 @@ protected:
     QString m_apiKey;
 };
 
-class OpenaiProviderBuiltin : public OpenaiProvider, public ModelProviderBuiltin {
+class OpenaiProviderBuiltin : public OpenaiProvider, private ModelProviderMutable {
     Q_GADGET
-    Q_PROPERTY(QString apiKey READ apiKey CONSTANT)
+    Q_PROPERTY(QString name    READ name    CONSTANT)
+    Q_PROPERTY(QUrl    baseUrl READ baseUrl CONSTANT)
 
 public:
-    /// Create a new built-in OpenAI provider (transient).
-    explicit OpenaiProviderBuiltin(QUuid id, QString name, QUrl baseUrl, QString apiKey);
+    /// Create a new built-in OpenAI provider, loading its API key from disk if known.
+    explicit OpenaiProviderBuiltin(ProviderStore *store, QUuid id, QString name, QUrl baseUrl);
+
+    void setApiKey(QString value) override { setMemberProp<QString>(&OpenaiProviderBuiltin::m_apiKey, "apiKey", std::move(value)); }
+
+protected:
+    auto asData() -> ModelProviderData override;
 };
 
 class OpenaiProviderCustom final : public OpenaiProvider, public ModelProviderCustom {
     Q_OBJECT
 
-    Q_PROPERTY(QString apiKey READ apiKey WRITE setApiKey NOTIFY apiKeyChanged)
-
 public:
     /// Load an existing OpenaiProvider from disk.
-    explicit OpenaiProviderCustom(std::shared_ptr<ProviderStore> store, QUuid id);
+    explicit OpenaiProviderCustom(ProviderStore *store, QUuid id, QString name, QUrl baseUrl, QString apiKey);
 
     /// Create a new OpenaiProvider on disk.
-    explicit OpenaiProviderCustom(std::shared_ptr<ProviderStore> store, QString name, QUrl baseUrl, QString apiKey);
+    explicit OpenaiProviderCustom(ProviderStore *store, QString name, QUrl baseUrl, QString apiKey);
 
-    void setApiKey(QString value) { setMemberProp<QString>(&OpenaiProviderCustom::m_apiKey, "apiKey", std::move(value)); }
+    void setApiKey(QString value) override { setMemberProp<QString>(&OpenaiProviderCustom::m_apiKey, "apiKey", std::move(value)); }
 
 Q_SIGNALS:
     void nameChanged   (const QString &value);
@@ -92,8 +99,7 @@ Q_SIGNALS:
     void apiKeyChanged (const QString &value);
 
 protected:
-    auto asData() -> ModelProviderData override
-    { return { m_id, ProviderType::openai, m_name, m_baseUrl, OpenaiProviderDetails { m_apiKey } }; }
+    auto asData() -> ModelProviderData override;
 };
 
 class OpenaiModelDescription : public ModelDescription {
@@ -101,7 +107,11 @@ class OpenaiModelDescription : public ModelDescription {
     Q_PROPERTY(QString modelName READ modelName CONSTANT)
 
 public:
-    explicit OpenaiModelDescription(std::shared_ptr<const OpenaiProvider> provider, QString modelName);
+    explicit OpenaiModelDescription(protected_t, std::shared_ptr<const OpenaiProvider> provider, QString modelName);
+
+    static auto create(std::shared_ptr<const OpenaiProvider> provider, QByteArray modelHash)
+        -> std::shared_ptr<OpenaiModelDescription>
+    { return std::make_shared<OpenaiModelDescription>(protected_t(), std::move(provider), std::move(modelHash)); }
 
     // getters
     [[nodiscard]] auto           provider () const -> const OpenaiProvider * override { return m_provider.get(); }
diff --git a/gpt4all-chat/src/llmodel_provider.cpp b/gpt4all-chat/src/llmodel_provider.cpp
index ae88c3a5..fbf847ef 100644
--- a/gpt4all-chat/src/llmodel_provider.cpp
+++ b/gpt4all-chat/src/llmodel_provider.cpp
@@ -1,5 +1,8 @@
 #include "llmodel_provider.h"
 
+#include "llmodel_ollama.h"
+#include "llmodel_openai.h"
+
 #include "mysettings.h"
 
 #include <fmt/format.h>
@@ -42,67 +45,97 @@ QVariant GenerationParams::tryParseValue(QMap<GenerationParam, QVariant> &values
 
 ModelProvider::~ModelProvider() noexcept = default;
 
-ModelProviderCustom::~ModelProviderCustom() noexcept
+ModelProviderMutable::~ModelProviderMutable() noexcept
 {
     if (auto res = m_store->release(m_id); !res)
         res.error().raise(); // should not happen - will terminate program
 }
 
-auto ModelProviderCustom::load() -> const ModelProviderData::Details &
-{
-    auto data = m_store->acquire(m_id);
-    if (!data)
-        data.error().raise();
-    m_name    = (*data)->name;
-    m_baseUrl = (*data)->base_url;
-    return (*data)->details;
-}
-
-ProviderRegistry::ProviderRegistry(fs::path path)
-    : m_store(std::move(path))
+ProviderRegistry::ProviderRegistry(PathSet paths)
+    : m_customStore (std::move(paths.custom ))
+    , m_builtinStore(std::move(paths.builtin))
 {
     auto *mysettings = MySettings::globalInstance();
     connect(mysettings, &MySettings::modelPathChanged, this, &ProviderRegistry::onModelPathChanged);
+    load();
 }
 
-Q_INVOKABLE void ProviderRegistry::registerBuiltinProvider(ModelProviderBuiltin *provider)
+void ProviderRegistry::load()
 {
-    auto [_, unique] = m_providers.emplace(provider->id(), provider->asQObject());
-    if (!unique)
-        qWarning() << "ignoring duplicate provider:" << provider->id();
+    for (auto &p : s_builtinProviders) { // (not all builtin providers are stored)
+        auto provider = std::make_shared<OpenaiProviderBuiltin>(m_builtinStore, p.id, p.name, p.base_url);
+        auto [_, unique] = m_providers.emplace(p.id, std::move(provider));
+        if (!unique)
+            throw std::logic_error(fmt::format("duplicate builtin provider id: {}", p.id));
+    }
+    for (auto &p : m_customStore.list()) { // disk is source of truth for custom providers
+        if (!p.custom_details) {
+            qWarning() << "ignoring builtin provider in custom store:" << p.id;
+            continue;
+        }
+        auto &cust = *p.custom_details;
+        std::shared_ptr<ModelProviderCustom> provider;
+        switch (p.type) {
+            using enum ProviderType;
+        case ollama:
+            provider = std::make_shared<OllamaProviderCustom>(
+                &m_customStore, p.id, cust.name, cust.base_url
+            );
+        case openai:
+            provider = std::make_shared<OpenaiProviderCustom>(
+                &m_customStore, p.id, cust.name, cust.base_url, p.openai_details.value().api_key
+            );
+        }
+        auto [_, unique] = m_providers.emplace(p.id, std::move(provider));
+        if (!unique)
+            qWarning() << "ignoring duplicate custom provider with id:" << p.id;
+    }
 }
 
 [[nodiscard]]
-bool ProviderRegistry::registerCustomProvider(std::unique_ptr<ModelProviderCustom> provider)
+bool ProviderRegistry::add(std::unique_ptr<ModelProviderCustom> provider)
 {
-    auto [_, unique] = m_providers.emplace(provider->id(), provider->asQObject());
+    auto [it, unique] = m_providers.emplace(provider->id(), std::move(provider));
     if (unique) {
-        m_customProviders.push_back(std::move(provider));
+        m_customProviders.push_back(std::make_unique<QUuid>(it->first));
         emit customProviderAdded(m_customProviders.size() - 1);
     }
     return unique;
 }
 
-fs::path ProviderRegistry::getSubdir()
+auto ProviderRegistry::customProviderAt(size_t i) const -> const ModelProviderCustom *
+{
+    auto it = m_providers.find(*m_customProviders.at(i));
+    Q_ASSERT(it != m_providers.end());
+    return &dynamic_cast<ModelProviderCustom &>(*it->second);
+}
+
+auto ProviderRegistry::getSubdirs() -> PathSet
 {
     auto *mysettings = MySettings::globalInstance();
-    return toFSPath(mysettings->modelPath()) / "providers";
+    auto parent = toFSPath(mysettings->modelPath()) / "providers";
+    return { .builtin = parent, .custom  = parent / "custom" };
 }
 
 void ProviderRegistry::onModelPathChanged()
 {
-    auto path = getSubdir();
-    if (path != m_store.path()) {
+    auto paths = getSubdirs();
+    if (paths.builtin != m_builtinStore.path()) {
         emit aboutToBeCleared();
-        m_customProviders.clear(); // delete custom providers to release store locks
-        if (auto res = m_store.setPath(path); !res)
+        // delete providers to release store locks
+        m_customProviders.clear();
+        m_providers.clear();
+        if (auto res = m_builtinStore.setPath(paths.builtin); !res)
             res.error().raise(); // should not happen
+        if (auto res = m_customStore.setPath(paths.custom); !res)
+            res.error().raise(); // should not happen
+        load();
     }
 }
 
 CustomProviderList::CustomProviderList(QPointer<ProviderRegistry> registry)
-    : m_registry(std::move(registry))
-    , m_size(m_registry->customProviderCount())
+    : m_registry(std::move(registry)              )
+    , m_size    (m_registry->customProviderCount())
 {
     connect(m_registry, &ProviderRegistry::customProviderAdded, this, &CustomProviderList::onCustomProviderAdded);
     connect(m_registry, &ProviderRegistry::aboutToBeCleared, this, &CustomProviderList::onAboutToBeCleared,
diff --git a/gpt4all-chat/src/llmodel_provider.h b/gpt4all-chat/src/llmodel_provider.h
index a4aea566..6ff6b9ef 100644
--- a/gpt4all-chat/src/llmodel_provider.h
+++ b/gpt4all-chat/src/llmodel_provider.h
@@ -14,6 +14,7 @@
 #include <QUuid>
 #include <QtPreprocessorSupport>
 
+#include <array>
 #include <cstddef>
 #include <filesystem>
 #include <memory>
@@ -63,9 +64,7 @@ class ModelProvider {
     Q_PROPERTY(QUuid id READ id CONSTANT)
 
 protected:
-    explicit ModelProvider(QUuid id) // load
-        : m_id(std::move(id)) {}
-    explicit ModelProvider(QUuid id, QString name, QUrl baseUrl) // create built-in
+    explicit ModelProvider(QUuid id, QString name, QUrl baseUrl) // create built-in or load
         : m_id(std::move(id)), m_name(std::move(name)), m_baseUrl(std::move(baseUrl)) {}
     explicit ModelProvider(QString name, QUrl baseUrl) // create custom
         : m_name(std::move(name)), m_baseUrl(std::move(baseUrl)) {}
@@ -93,36 +92,39 @@ protected:
     QUrl    m_baseUrl;
 };
 
-class ModelProviderBuiltin : public virtual ModelProvider {
+// Mixin with no public interface providing basic load/save
+class ModelProviderMutable : public virtual ModelProvider {
     Q_GADGET
-    Q_PROPERTY(QString name    READ name    CONSTANT)
-    Q_PROPERTY(QUrl    baseUrl READ baseUrl CONSTANT)
-};
-
-class ModelProviderCustom : public virtual ModelProvider {
-    Q_GADGET
-    Q_PROPERTY(QString name    READ name    WRITE setName    NOTIFY nameChanged   )
-    Q_PROPERTY(QUrl    baseUrl READ baseUrl WRITE setBaseUrl NOTIFY baseUrlChanged)
 
 protected:
-    explicit ModelProviderCustom(std::shared_ptr<ProviderStore> store)
-        : m_store(std::move(store)) {}
+    explicit ModelProviderMutable(ProviderStore *store)
+        : m_store(store) {}
 
 public:
-    ~ModelProviderCustom() noexcept override;
-
-    // setters
-    void setName   (QString value) { setMemberProp<QString>(&ModelProviderCustom::m_name,    "name",    std::move(value)); }
-    void setBaseUrl(QUrl    value) { setMemberProp<QUrl   >(&ModelProviderCustom::m_baseUrl, "baseUrl", std::move(value)); }
+    ~ModelProviderMutable() noexcept override;
 
 protected:
-    virtual auto load() -> const ModelProviderData::Details &;
     virtual auto asData() -> ModelProviderData = 0;
 
     template <typename T, typename S, typename C>
     void setMemberProp(this S &self, T C::* member, std::string_view name, T value);
 
-    std::shared_ptr<ProviderStore> m_store;
+    ProviderStore *m_store;
+};
+
+class ModelProviderCustom : public ModelProviderMutable {
+    Q_GADGET
+    Q_PROPERTY(QString name    READ name    WRITE setName    NOTIFY nameChanged   )
+    Q_PROPERTY(QUrl    baseUrl READ baseUrl WRITE setBaseUrl NOTIFY baseUrlChanged)
+
+protected:
+    explicit ModelProviderCustom(ProviderStore *store)
+        : ModelProviderMutable(store) {}
+
+public:
+    // setters
+    void setName   (QString value) { setMemberProp<QString>(&ModelProviderCustom::m_name,    "name",    std::move(value)); }
+    void setBaseUrl(QUrl    value) { setMemberProp<QUrl   >(&ModelProviderCustom::m_baseUrl, "baseUrl", std::move(value)); }
 };
 
 class ProviderRegistry : public QObject {
@@ -130,18 +132,26 @@ class ProviderRegistry : public QObject {
     QML_ELEMENT
     QML_SINGLETON
 
+private:
+    struct PathSet { std::filesystem::path builtin, custom; };
+
+    struct BuiltinProviderData {
+        QUuid   id;
+        QString name;
+        QUrl    base_url;
+    };
+
 protected:
-    explicit ProviderRegistry(std::filesystem::path path);
+    explicit ProviderRegistry(PathSet paths);
 
 public:
-    static ProviderRegistry *create(QQmlEngine *, QJSEngine *) { return new ProviderRegistry(getSubdir()); }
-    Q_INVOKABLE   void registerBuiltinProvider(ModelProviderBuiltin *provider);
-    [[nodiscard]] bool registerCustomProvider (std::unique_ptr<ModelProviderCustom> provider);
+    static ProviderRegistry *create(QQmlEngine *, QJSEngine *) { return new ProviderRegistry(getSubdirs()); }
+    [[nodiscard]] bool add(std::unique_ptr<ModelProviderCustom> provider);
 
-    size_t customProviderCount() const
+    // TODO(jared): implement a way to remove custom providers via the model
+    [[nodiscard]] size_t customProviderCount() const
     { return m_customProviders.size(); }
-    auto customProviderAt(size_t i) const -> const ModelProviderCustom *
-    { return m_customProviders.at(i).get(); }
+    [[nodiscard]] auto customProviderAt(size_t i) const -> const ModelProviderCustom *;
     auto operator[](const QUuid &id) -> ModelProviderCustom *
     { return &dynamic_cast<ModelProviderCustom &>(*m_providers.at(id)); }
 
@@ -150,20 +160,24 @@ Q_SIGNALS:
     void aboutToBeCleared();
 
 private:
-    static auto getSubdir() -> std::filesystem::path;
+    void load();
+    static PathSet getSubdirs();
 
 private Q_SLOTS:
     void onModelPathChanged();
 
 private:
-    ProviderStore                                     m_store;
-    std::unordered_map<QUuid, QPointer<QObject>>      m_providers;
-    std::vector<std::unique_ptr<ModelProviderCustom>> m_customProviders;
+    static constexpr size_t N_BUILTIN = 3;
+    static const std::array<BuiltinProviderData, N_BUILTIN> s_builtinProviders;
+
+    ProviderStore                                             m_customStore;
+    ProviderStore                                             m_builtinStore;
+    std::unordered_map<QUuid, std::shared_ptr<ModelProvider>> m_providers;
+    std::vector<std::unique_ptr<QUuid>>                       m_customProviders;
 };
 
 class CustomProviderList : public QAbstractListModel {
     Q_OBJECT
-    QML_ELEMENT
 
 protected:
     explicit CustomProviderList(QPointer<ProviderRegistry> registry);
diff --git a/gpt4all-chat/src/llmodel_provider.inl b/gpt4all-chat/src/llmodel_provider.inl
index a707f6b2..94a078c3 100644
--- a/gpt4all-chat/src/llmodel_provider.inl
+++ b/gpt4all-chat/src/llmodel_provider.inl
@@ -13,9 +13,9 @@ void GenerationParams::tryParseValue(this S &self, QMap<GenerationParam, QVarian
 }
 
 template <typename T, typename S, typename C>
-void ModelProviderCustom::setMemberProp(this S &self, T C::* member, std::string_view name, T value)
+void ModelProviderMutable::setMemberProp(this S &self, T C::* member, std::string_view name, T value)
 {
-    auto &mpc = static_cast<ModelProviderCustom &>(self);
+    auto &mpc = static_cast<ModelProviderMutable &>(self);
     auto &cur = self.*member;
     if (cur != value) {
         cur = std::move(value);
diff --git a/gpt4all-chat/src/llmodel_provider_builtins.cpp b/gpt4all-chat/src/llmodel_provider_builtins.cpp
new file mode 100644
index 00000000..77367ee1
--- /dev/null
+++ b/gpt4all-chat/src/llmodel_provider_builtins.cpp
@@ -0,0 +1,34 @@
+#include "llmodel_provider.h"
+
+using namespace Qt::StringLiterals;
+
+
+namespace gpt4all::ui {
+
+
+// TODO: use these in the constructor of ProviderRegistry
+// TODO: we have to be careful to reserve these names for ProviderStore purposes, so the user can't write JSON files that alias them.
+// this *is a problem*, because we want to be able to safely introduce these.
+// so we need a different namespace, i.e. a *different directory*.
+const std::array<
+    ProviderRegistry::BuiltinProviderData, ProviderRegistry::N_BUILTIN
+> ProviderRegistry::s_builtinProviders {
+    BuiltinProviderData {
+        .id       = QUuid("20f963dc-1f99-441e-ad80-f30a0a06bcac"),
+        .name     = u"Groq"_s,
+        .base_url = u"https://api.groq.com/openai/v1/"_s,
+    },
+    BuiltinProviderData {
+        .id       = QUuid("6f874c3a-f1ad-47f7-9129-755c5477146c"),
+        .name     = u"OpenAI"_s,
+        .base_url = u"https://api.openai.com/v1/"_s,
+    },
+    BuiltinProviderData {
+        .id       = QUuid("7ae617b3-c0b2-4d2c-9ff2-bc3f049494cc"),
+        .name     = u"Mistral"_s,
+        .base_url = u"https://api.mistral.ai/v1/"_s,
+    },
+};
+
+
+} // namespace gpt4all::ui
diff --git a/gpt4all-chat/src/store_base.cpp b/gpt4all-chat/src/store_base.cpp
index f3d49eb6..c084e605 100644
--- a/gpt4all-chat/src/store_base.cpp
+++ b/gpt4all-chat/src/store_base.cpp
@@ -73,7 +73,7 @@ auto DataStoreBase::reload() -> DataStoreResult<>
         if (!jv) {
             (qWarning().nospace() << "skipping " << file.fileName() << "because of read error: ").noquote()
                 << jv.error().errorString();
-        } else if (auto [unique, uuid] = insert(*jv); !unique)
+        } else if (auto [unique, uuid] = cacheInsert(*jv); !unique)
             qWarning() << "skipping duplicate data store entry:" << uuid;
         file.close();
     }
@@ -103,7 +103,7 @@ auto DataStoreBase::openNew(const QString &name) -> DataStoreResult<std::unique_
     return file;
 }
 
-auto DataStoreBase::openExisting(const QString &name) -> DataStoreResult<std::unique_ptr<QSaveFile>>
+auto DataStoreBase::openExisting(const QString &name, bool allowCreate) -> DataStoreResult<std::unique_ptr<QSaveFile>>
 {
     auto path = getFilePath(name);
     if (!QFile::exists(path))
@@ -111,7 +111,10 @@ auto DataStoreBase::openExisting(const QString &name) -> DataStoreResult<std::un
             std::make_error_code(std::errc::no_such_file_or_directory), path.string()
         ));
     auto file = std::make_unique<QSaveFile>(toQString(path));
-    if (!file->open(QSaveFile::WriteOnly | QSaveFile::ExistingOnly))
+    QFile::OpenMode flags = QSaveFile::WriteOnly;
+    if (!allowCreate)
+        flags |= QSaveFile::ExistingOnly;
+    if (!file->open(flags))
         return std::unexpected(&*file);
     return file;
 }
diff --git a/gpt4all-chat/src/store_base.h b/gpt4all-chat/src/store_base.h
index 79ba2300..720fe797 100644
--- a/gpt4all-chat/src/store_base.h
+++ b/gpt4all-chat/src/store_base.h
@@ -15,6 +15,7 @@
 #include <expected>
 #include <filesystem>
 #include <memory>
+#include <optional>
 #include <unordered_map>
 #include <unordered_set>
 #include <utility>
@@ -65,13 +66,13 @@ public:
 protected:
     auto reload() -> DataStoreResult<>;
     virtual auto clear() -> DataStoreResult<> = 0;
-    struct InsertResult { bool unique; QUuid uuid; };
-    virtual InsertResult insert(const boost::json::value &jv) = 0;
+    struct CacheInsertResult { bool unique; QUuid uuid; };
+    virtual CacheInsertResult cacheInsert(const boost::json::value &jv) = 0;
 
     // helpers
     auto getFilePath(const QString &name) -> std::filesystem::path;
     auto openNew(const QString &name) -> DataStoreResult<std::unique_ptr<QFile>>;
-    auto openExisting(const QString &name) -> DataStoreResult<std::unique_ptr<QSaveFile>>;
+    auto openExisting(const QString &name, bool allowCreate = false) -> DataStoreResult<std::unique_ptr<QSaveFile>>;
     static auto read(QFileDevice &file, boost::json::stream_parser &parser) -> DataStoreResult<boost::json::value>;
     auto write(const boost::json::value &value, QFileDevice &file) -> DataStoreResult<>;
 
@@ -94,23 +95,26 @@ public:
 
     auto list() -> tl::generator<const T &>;
     auto setData(T data) -> DataStoreResult<>;
+    auto createOrSetData(T data, const QString &name) -> DataStoreResult<>;
     auto remove(const QUuid &id) -> DataStoreResult<>;
 
-    auto acquire(QUuid        id) -> DataStoreResult<const T *>;
+    auto acquire(QUuid        id) -> DataStoreResult<std::optional<const T *>>;
     auto release(const QUuid &id) -> DataStoreResult<>;
 
-    [[nodiscard]]
-    auto operator[](const QUuid &id) const -> const T &
+    [[nodiscard]] auto operator[](const QUuid &id) const -> const T &
     { return m_entries.at(id); }
+    [[nodiscard]] auto find(const QUuid &id) const -> std::optional<const T *>
+    { auto it = m_entries.find(id); return it == m_entries.end() ? std::nullopt : std::optional(&*it); }
 
 protected:
     auto createImpl(T data, const QString &name) -> DataStoreResult<const T *>;
     auto clear() -> DataStoreResult<> final;
-    InsertResult insert(const boost::json::value &jv) override;
+    CacheInsertResult cacheInsert(const boost::json::value &jv) override;
 
 private:
-    std::unordered_map<QUuid, T> m_entries;
-    std::unordered_set<QUuid>    m_acquired;
+    std::unordered_map<QUuid, T>       m_entries;
+    std::unordered_set<QUuid>          m_acquired;
+    std::unordered_map<QUuid, QString> m_names;
 };
 
 
diff --git a/gpt4all-chat/src/store_base.inl b/gpt4all-chat/src/store_base.inl
index 840afd0d..641ad905 100644
--- a/gpt4all-chat/src/store_base.inl
+++ b/gpt4all-chat/src/store_base.inl
@@ -51,8 +51,12 @@ auto DataStore<T>::createImpl(T data, const QString &name) -> DataStoreResult<co
 template <typename T>
 auto DataStore<T>::setData(T data) -> DataStoreResult<>
 {
+    auto name_it = m_names.find(data.id);
+    if (name_it == m_names.end())
+        return std::unexpected(QStringLiteral("id not found: %1").arg(data.id.toString()));
+
     // acquire path
-    auto file = openExisting(data.name);
+    auto file = openExisting(name_it->second);
     if (!file)
         return std::unexpected(file.error());
 
@@ -67,6 +71,32 @@ auto DataStore<T>::setData(T data) -> DataStoreResult<>
     return {};
 }
 
+template <typename T>
+auto DataStore<T>::createOrSetData(T data, const QString &name) -> DataStoreResult<>
+{
+    auto name_it = m_names.find(data.id);
+    if (name_it != m_names.end() && name_it->second != name)
+        return std::unexpected(QStringLiteral("name conflict for id %1: old=%2, new=%3")
+                               .arg(data.id.toString(), name_it->second, name));
+
+    // acquire path
+    auto file = openExisting(name, /*allowCreate*/ true);
+    if (!file)
+        return std::unexpected(file.error());
+
+    // serialize
+    if (auto res = write(boost::json::value_from(data), **file); !res)
+        return std::unexpected(res.error());
+    if (!(*file)->commit())
+        return std::unexpected(file->get());
+
+    // update
+    m_entries[data.id] = std::move(data);
+    if (name_it == m_names.end())
+        m_names.emplace(data.id, name);
+    return {};
+}
+
 template <typename T>
 auto DataStore<T>::remove(const QUuid &id) -> DataStoreResult<>
 {
@@ -89,12 +119,12 @@ auto DataStore<T>::remove(const QUuid &id) -> DataStoreResult<>
 }
 
 template <typename T>
-auto DataStore<T>::acquire(QUuid id) -> DataStoreResult<const T *>
+auto DataStore<T>::acquire(QUuid id) -> DataStoreResult<std::optional<const T *>>
 {
     auto [it, unique] = m_acquired.insert(std::move(id));
     if (!unique)
         return std::unexpected(QStringLiteral("id already acquired: %1").arg(id.toString()));
-    return &(*this)[*it];
+    return find(*it);
 }
 
 template <typename T>
@@ -115,7 +145,7 @@ auto DataStore<T>::clear() -> DataStoreResult<>
 }
 
 template <typename T>
-auto DataStore<T>::insert(const boost::json::value &jv) -> InsertResult
+auto DataStore<T>::cacheInsert(const boost::json::value &jv) -> CacheInsertResult
 {
     auto data = boost::json::value_to<T>(jv);
     auto id = data.id;
@@ -124,5 +154,4 @@ auto DataStore<T>::insert(const boost::json::value &jv) -> InsertResult
 }
 
 
-
 } // namespace gpt4all::ui
diff --git a/gpt4all-chat/src/store_provider.cpp b/gpt4all-chat/src/store_provider.cpp
index 6c42a437..30a26aed 100644
--- a/gpt4all-chat/src/store_provider.cpp
+++ b/gpt4all-chat/src/store_provider.cpp
@@ -1,23 +1,81 @@
 #include "store_provider.h"
 
+#include "json-helpers.h" // IWYU pragma: keep
+
+#include <gpt4all-backend/json-helpers.h> // IWYU pragma: keep
+
 #include <utility>
 
+namespace json = boost::json;
+
 
 namespace gpt4all::ui {
 
 
+void tag_invoke(const boost::json::value_from_tag &, boost::json::value &jv, ModelProviderData data)
+{
+    auto &obj = jv.emplace_object();
+    obj = { { "id",      data.id              },
+            { "builtin", !data.custom_details },
+            { "type",    data.type()          } };
+    if (auto custom = data.custom_details) {
+        obj.emplace("name",     custom->name);
+        obj.emplace("base_url", custom->base_url);
+    }
+    switch (data.type()) {
+        using enum ProviderType;
+    case openai:
+        obj.emplace("api_key", std::get<size_t(openai)>(data.provider_details).api_key);
+    case ollama:
+        ;
+    }
+}
+
+auto tag_invoke(const boost::json::value_to_tag<ModelProviderData> &, const boost::json::value &jv)
+    -> ModelProviderData
+{
+    auto &obj = jv.as_object();
+    auto type = json::value_to<ProviderType>(jv.at("type"));
+    std::optional<CustomProviderDetails> custom_details;
+    if (!jv.at("builtin").as_bool())
+        custom_details.emplace(CustomProviderDetails {
+            json::value_to<QString>(jv.at("name"    )),
+            json::value_to<QString>(jv.at("base_url")),
+        });
+    ModelProviderData::ProviderDetails provider_details;
+    switch (type) {
+        using enum ProviderType;
+    case openai:
+        provider_details = OpenaiProviderDetails { json::value_to<QString>(jv.at("api_key")) };
+    case ollama:
+        ;
+    }
+    return {
+        .id               = json::value_to<QUuid>(obj.at("id")),
+        .custom_details   = std::move(custom_details),
+        .provider_details = std::move(provider_details)
+    };
+}
+
 auto ProviderStore::create(QString name, QUrl base_url, QString api_key)
     -> DataStoreResult<const ModelProviderData *>
 {
-    ModelProviderData data { QUuid::createUuid(), ProviderType::openai, name, std::move(base_url),
-                             OpenaiProviderDetails { std::move(api_key) }                          };
+    ModelProviderData data {
+        .id               = QUuid::createUuid(),
+        .custom_details   = CustomProviderDetails { name, std::move(base_url) },
+        .provider_details = OpenaiProviderDetails { std::move(api_key)        },
+    };
     return createImpl(std::move(data), name);
 }
 
 auto ProviderStore::create(QString name, QUrl base_url)
     -> DataStoreResult<const ModelProviderData *>
 {
-    ModelProviderData data { QUuid::createUuid(), ProviderType::ollama, name, std::move(base_url), {} };
+    ModelProviderData data {
+        .id               = QUuid::createUuid(),
+        .custom_details   = CustomProviderDetails { name, std::move(base_url) },
+        .provider_details = {},
+    };
     return createImpl(std::move(data), name);
 }
 
diff --git a/gpt4all-chat/src/store_provider.h b/gpt4all-chat/src/store_provider.h
index 02666a10..078a3ec4 100644
--- a/gpt4all-chat/src/store_provider.h
+++ b/gpt4all-chat/src/store_provider.h
@@ -4,33 +4,43 @@
 
 #include <boost/describe/class.hpp>
 #include <boost/describe/enum.hpp>
+#include <boost/json.hpp> // IWYU pragma: keep
 
 #include <QString>
 #include <QUrl>
 #include <QUuid>
 
-#include <variant>
-
 
 namespace gpt4all::ui {
 
 
-BOOST_DEFINE_ENUM_CLASS(ProviderType, openai, ollama)
+// indices of this enum should be consistent with indices of ProviderDetails
+enum class ProviderType {
+    openai = 0,
+    ollama = 1,
+};
+BOOST_DESCRIBE_ENUM(ProviderType, openai, ollama)
+
+struct CustomProviderDetails {
+    QString name;
+    QUrl    base_url;
+};
 
 struct OpenaiProviderDetails {
     QString api_key;
 };
-BOOST_DESCRIBE_STRUCT(OpenaiProviderDetails, (), (api_key))
 
 struct ModelProviderData {
-    using Details = std::variant<std::monostate, OpenaiProviderDetails>;
-    QUuid        id;
-    ProviderType type;
-    QString      name;
-    QUrl         base_url;
-    Details      details;
+    using ProviderDetails = std::variant<OpenaiProviderDetails, std::monostate>;
+    QUuid                                id;
+    std::optional<CustomProviderDetails> custom_details;
+    ProviderDetails                      provider_details;
+
+    ProviderType type() const { return ProviderType(provider_details.index()); }
 };
-BOOST_DESCRIBE_STRUCT(ModelProviderData, (), (id, type, name, base_url, details))
+void tag_invoke(const boost::json::value_from_tag &, boost::json::value &jv, ModelProviderData data);
+auto tag_invoke(const boost::json::value_to_tag<ModelProviderData> &, const boost::json::value &jv)
+    -> ModelProviderData;
 
 class ProviderStore : public DataStore<ModelProviderData> {
 private: