From dec5ff0ff92800f91e5580a4dbeb48b592ecffb8 Mon Sep 17 00:00:00 2001
From: Luc Mcgrady <lucmcgrady@gmail.com>
Date: Fri, 26 Jun 2026 21:52:54 +0100
Subject: [PATCH 1/6] Save set values in config_json

---
 qt/aqt/mediasrv.py                   |  3 +++
 qt/aqt/webview.py                    |  1 +
 rslib/src/backend/config.rs          | 10 ++++++++--
 ts/lib/components/Switch.svelte      |  1 +
 ts/routes/preferences/+page.svelte   | 14 ++++++++++----
 ts/routes/preferences/+page.ts       | 16 ++++++++++++++++
 ts/routes/preferences/LabItem.svelte | 11 ++++++++++-
 ts/routes/preferences/json.ts        | 21 +++++++++++++++++++++
 8 files changed, 70 insertions(+), 7 deletions(-)
 create mode 100644 ts/routes/preferences/+page.ts
 create mode 100644 ts/routes/preferences/json.ts

diff --git a/qt/aqt/mediasrv.py b/qt/aqt/mediasrv.py
index c7f0d831cf1..3968c609fab 100644
--- a/qt/aqt/mediasrv.py
+++ b/qt/aqt/mediasrv.py
@@ -760,6 +760,9 @@ def save_custom_colours() -> bytes:
     # DeckConfigService
     "get_ignored_before_count",
     "get_retention_workload",
+    # ConfigService
+    "set_config_json",
+    "get_config_json",
 ]
 
 
diff --git a/qt/aqt/webview.py b/qt/aqt/webview.py
index 1d55006ba5a..c7fd8165796 100644
--- a/qt/aqt/webview.py
+++ b/qt/aqt/webview.py
@@ -143,6 +143,7 @@ def _profileForPage(self, kind: AnkiWebViewKind) -> QWebEngineProfile:
             AnkiWebViewKind.IMPORT_ANKI_PACKAGE,
             AnkiWebViewKind.IMPORT_CSV,
             AnkiWebViewKind.IMPORT_LOG,
+            AnkiWebViewKind.PREFERENCES,
         )
 
         global _profile_with_api_access, _profile_without_api_access
diff --git a/rslib/src/backend/config.rs b/rslib/src/backend/config.rs
index b6e81ce2ad7..3b731067472 100644
--- a/rslib/src/backend/config.rs
+++ b/rslib/src/backend/config.rs
@@ -57,8 +57,14 @@ impl From<StringKeyProto> for StringKey {
 
 impl crate::services::ConfigService for Collection {
     fn get_config_json(&mut self, input: generic::String) -> Result<generic::Json> {
-        let val: Option<Value> = self.get_config_optional(input.val.as_str());
-        val.or_not_found(input.val)
+        let key = input.val.as_str();
+        let val: Option<Value> = self.get_config_optional(key);
+        let default = match key {
+            "experimentalFeatures" => Some(serde_json::from_str("{}").unwrap()),
+            _ => None,
+        };
+        val.or(default)
+            .or_not_found(key)
             .and_then(|v| serde_json::to_vec(&v).map_err(Into::into))
             .map(Into::into)
     }
diff --git a/ts/lib/components/Switch.svelte b/ts/lib/components/Switch.svelte
index d48f46fb338..343cddf3baa 100644
--- a/ts/lib/components/Switch.svelte
+++ b/ts/lib/components/Switch.svelte
@@ -20,6 +20,7 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
         class:nightMode={$pageTheme.isDark}
         bind:checked={value}
         {disabled}
+        on:input
     />
 </div>
 
diff --git a/ts/routes/preferences/+page.svelte b/ts/routes/preferences/+page.svelte
index 6032d7bd502..471f80732f4 100644
--- a/ts/routes/preferences/+page.svelte
+++ b/ts/routes/preferences/+page.svelte
@@ -2,10 +2,14 @@
 Copyright: Ankitects Pty Ltd and contributors
 License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
 -->
-<script>
+<script lang="ts">
     import "../deck-options/deck-options-base.scss";
     import Warning from "../deck-options/Warning.svelte";
     import LabItem from "./LabItem.svelte";
+    import type { PreferenceStore } from "$lib/sveltelib/preferences";
+
+    export let data: { labPerfs: PreferenceStore<any> };
+    const labPerfs = data.labPerfs;
 </script>
 
 <div class="container">
@@ -17,13 +21,15 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
         <LabItem
             title="Svelte note editor"
             description="Replaces the legacy editor with a new Svelte-based implementation. May affect addon compatibility."
+            key="svelte-editor"
+            {labPerfs}
         ></LabItem>
-        <LabItem title="Example 2"></LabItem>
         <LabItem
-            title="Example 3"
+            title="Example 2"
             description="This is a long winded description to help demonstrate the tiling of these elements. They should remain in line because I have used the css grid rather than flex boxes for easy use."
+            key="example-2"
+            {labPerfs}
         ></LabItem>
-        <LabItem title="Example 4"></LabItem>
     </div>
 </div>
 
diff --git a/ts/routes/preferences/+page.ts b/ts/routes/preferences/+page.ts
new file mode 100644
index 00000000000..03d19aa0ee8
--- /dev/null
+++ b/ts/routes/preferences/+page.ts
@@ -0,0 +1,16 @@
+// Copyright: Ankitects Pty Ltd and contributors
+// License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
+import { autoSavingPrefs } from "$lib/sveltelib/preferences";
+import type { PageLoad } from "./$types";
+import { getConfigJsonObject, setConfigJsonObject } from "./json";
+
+const CONFIG_KEY = "experimentalFeatures";
+
+export const load = (async () => {
+    const labPerfs = await autoSavingPrefs(
+        () => getConfigJsonObject(CONFIG_KEY),
+        ($config) => setConfigJsonObject(CONFIG_KEY, $config),
+    );
+
+    return { labPerfs };
+}) satisfies PageLoad;
diff --git a/ts/routes/preferences/LabItem.svelte b/ts/routes/preferences/LabItem.svelte
index 03aec37b06b..8514f339d75 100644
--- a/ts/routes/preferences/LabItem.svelte
+++ b/ts/routes/preferences/LabItem.svelte
@@ -4,16 +4,25 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
 -->
 <script lang="ts">
     import Switch from "$lib/components/Switch.svelte";
+    import type { PreferenceStore } from "$lib/sveltelib/preferences";
 
     export let title: string;
     export let description = "";
+    export let key: string;
+    export let labPerfs: PreferenceStore<any>;
+    let value = $labPerfs[key];
+
+    function onInput(e: Event) {
+        const target = e.target as HTMLInputElement;
+        $labPerfs = { ...$labPerfs, [key]: target.checked };
+    }
 </script>
 
 <label>
     <div class="header">
         <b>{title}</b>
         <div class="switch">
-            <Switch id={title} value={false}></Switch>
+            <Switch id={title} bind:value on:input={onInput}></Switch>
         </div>
     </div>
     {description}
diff --git a/ts/routes/preferences/json.ts b/ts/routes/preferences/json.ts
new file mode 100644
index 00000000000..2fcbf818de2
--- /dev/null
+++ b/ts/routes/preferences/json.ts
@@ -0,0 +1,21 @@
+// Copyright: Ankitects Pty Ltd and contributors
+// License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
+import { getConfigJson, setConfigJson } from "@generated/backend";
+
+const encoder = new TextEncoder();
+const decoder = new TextDecoder();
+
+export async function getConfigJsonObject(key: string) {
+    const resp = await getConfigJson({ val: key });
+    const json_string = decoder.decode(resp.json);
+    if (json_string.length > 0) {
+        return JSON.parse(json_string);
+    } else {
+        return {};
+    }
+}
+
+export async function setConfigJsonObject(key: string, value: any, undoable = false) {
+    value = JSON.stringify(value);
+    return await setConfigJson({ key, valueJson: encoder.encode(value), undoable });
+}

From 6b4337a582b0a0b124e66b51d9a8bd69ee9ecd8b Mon Sep 17 00:00:00 2001
From: Luc Mcgrady <lucmcgrady@gmail.com>
Date: Fri, 26 Jun 2026 22:11:20 +0100
Subject: [PATCH 2/6] Experiment loading interface

---
 pylib/anki/config.py               | 5 +++++
 qt/aqt/main.py                     | 2 ++
 ts/routes/preferences/+page.svelte | 6 +++---
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/pylib/anki/config.py b/pylib/anki/config.py
index 775557c848f..113438e0676 100644
--- a/pylib/anki/config.py
+++ b/pylib/anki/config.py
@@ -37,6 +37,8 @@
 class ConfigManager:
     def __init__(self, col: anki.collection.Collection):
         self.col = col.weakref()
+        # Saved when the collection is loaded to prevent changes before restart.
+        self._experiments: dict[str, bool] = self.get_immutable("experimentalFeatures")
 
     def get_immutable(self, key: str) -> Any:
         try:
@@ -44,6 +46,9 @@ def get_immutable(self, key: str) -> Any:
         except NotFoundError as exc:
             raise KeyError from exc
 
+    def experiment_enabled(self, key: str) -> bool:
+        return self._experiments.get(key, False)
+
     def set(self, key: str, val: Any) -> None:
         self.col._backend.set_config_json_no_undo(
             key=key,
diff --git a/qt/aqt/main.py b/qt/aqt/main.py
index d25d5a79cb7..9e3666698db 100644
--- a/qt/aqt/main.py
+++ b/qt/aqt/main.py
@@ -527,6 +527,8 @@ def _onsuccess(synced: bool) -> None:
                 onsuccess()
             if not self.safeMode:
                 self.maybe_check_for_addon_updates(self.setup_auto_update)
+            if self.col.conf.experiment_enabled("ping"):
+                showInfo("You have the \"ping\" experiment enabled")
 
         last_day_cutoff = self.col.sched.day_cutoff
 
diff --git a/ts/routes/preferences/+page.svelte b/ts/routes/preferences/+page.svelte
index 471f80732f4..02567036b6b 100644
--- a/ts/routes/preferences/+page.svelte
+++ b/ts/routes/preferences/+page.svelte
@@ -25,9 +25,9 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
             {labPerfs}
         ></LabItem>
         <LabItem
-            title="Example 2"
-            description="This is a long winded description to help demonstrate the tiling of these elements. They should remain in line because I have used the css grid rather than flex boxes for easy use."
-            key="example-2"
+            title="Ping"
+            description="Enable this experiment and see an alert every time you load this profile. Used for testing the experiment interface."
+            key="ping"
             {labPerfs}
         ></LabItem>
     </div>

From fa910f3f42cfaf001a60e529348b0ab7d95107d6 Mon Sep 17 00:00:00 2001
From: Luc Mcgrady <lucmcgrady@gmail.com>
Date: Mon, 29 Jun 2026 15:43:36 +0100
Subject: [PATCH 3/6] give restart required warning

---
 pylib/anki/config.py  | 9 ++++++++-
 qt/aqt/preferences.py | 4 ++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/pylib/anki/config.py b/pylib/anki/config.py
index 113438e0676..606e0f7bc5d 100644
--- a/pylib/anki/config.py
+++ b/pylib/anki/config.py
@@ -38,7 +38,7 @@ class ConfigManager:
     def __init__(self, col: anki.collection.Collection):
         self.col = col.weakref()
         # Saved when the collection is loaded to prevent changes before restart.
-        self._experiments: dict[str, bool] = self.get_immutable("experimentalFeatures")
+        self._experiments = self._get_unapplied_experiments()
 
     def get_immutable(self, key: str) -> Any:
         try:
@@ -49,6 +49,13 @@ def get_immutable(self, key: str) -> Any:
     def experiment_enabled(self, key: str) -> bool:
         return self._experiments.get(key, False)
 
+    def _get_unapplied_experiments(self) -> dict[str, bool]:
+        """This fetches the experments in the state that they are saved in the database.
+        This should not be used to check if an experement is enabled because this will update immidiately without a restart
+
+        use "experiment_enabled" to fetch an active experiment instead"""
+        return self.get_immutable("experimentalFeatures")
+
     def set(self, key: str, val: Any) -> None:
         self.col._backend.set_config_json_no_undo(
             key=key,
diff --git a/qt/aqt/preferences.py b/qt/aqt/preferences.py
index 6ef1f1d496d..abb7a80997a 100644
--- a/qt/aqt/preferences.py
+++ b/qt/aqt/preferences.py
@@ -403,6 +403,10 @@ def update_global(self) -> None:
             self.mw.pm.setUiScale(newScale)
             restart_required = True
 
+        conf = self.mw.col.conf
+        if conf._get_unapplied_experiments() != conf._experiments:
+            restart_required = True
+
         if restart_required:
             showInfo(tr.preferences_changes_will_take_effect_when_you())
 

From 27310e6a9e19029d4ced4b4803264a2507fc06b7 Mon Sep 17 00:00:00 2001
From: Luc Mcgrady <lucmcgrady@gmail.com>
Date: Mon, 29 Jun 2026 15:44:48 +0100
Subject: [PATCH 4/6] ./check

---
 qt/aqt/main.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/qt/aqt/main.py b/qt/aqt/main.py
index 9e3666698db..c3d1a73d831 100644
--- a/qt/aqt/main.py
+++ b/qt/aqt/main.py
@@ -528,7 +528,7 @@ def _onsuccess(synced: bool) -> None:
             if not self.safeMode:
                 self.maybe_check_for_addon_updates(self.setup_auto_update)
             if self.col.conf.experiment_enabled("ping"):
-                showInfo("You have the \"ping\" experiment enabled")
+                showInfo('You have the "ping" experiment enabled')
 
         last_day_cutoff = self.col.sched.day_cutoff
 

From d1eee22d50d602f89e5d37923d3cf269ebdbd581 Mon Sep 17 00:00:00 2001
From: Luc Mcgrady <lucmcgrady@gmail.com>
Date: Mon, 29 Jun 2026 15:50:56 +0100
Subject: [PATCH 5/6] unapplied -> dirty

---
 pylib/anki/config.py  | 10 +++++-----
 qt/aqt/preferences.py |  2 +-
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/pylib/anki/config.py b/pylib/anki/config.py
index 606e0f7bc5d..cc7b469f249 100644
--- a/pylib/anki/config.py
+++ b/pylib/anki/config.py
@@ -38,7 +38,7 @@ class ConfigManager:
     def __init__(self, col: anki.collection.Collection):
         self.col = col.weakref()
         # Saved when the collection is loaded to prevent changes before restart.
-        self._experiments = self._get_unapplied_experiments()
+        self._experiments = self._get_experiments_dirty()
 
     def get_immutable(self, key: str) -> Any:
         try:
@@ -49,11 +49,11 @@ def get_immutable(self, key: str) -> Any:
     def experiment_enabled(self, key: str) -> bool:
         return self._experiments.get(key, False)
 
-    def _get_unapplied_experiments(self) -> dict[str, bool]:
-        """This fetches the experments in the state that they are saved in the database.
-        This should not be used to check if an experement is enabled because this will update immidiately without a restart
+    def _get_experiments_dirty(self) -> dict[str, bool]:
+        """This fetches the experiments in the state that they are saved in the database.
+        This should not be used to check if an experiment is enabled because this will update immediately without a restart.
 
-        use "experiment_enabled" to fetch an active experiment instead"""
+        Use "experiment_enabled" to fetch an active experiment instead."""
         return self.get_immutable("experimentalFeatures")
 
     def set(self, key: str, val: Any) -> None:
diff --git a/qt/aqt/preferences.py b/qt/aqt/preferences.py
index abb7a80997a..3ebc2c0bd71 100644
--- a/qt/aqt/preferences.py
+++ b/qt/aqt/preferences.py
@@ -404,7 +404,7 @@ def update_global(self) -> None:
             restart_required = True
 
         conf = self.mw.col.conf
-        if conf._get_unapplied_experiments() != conf._experiments:
+        if conf._get_experiments_dirty() != conf._experiments:
             restart_required = True
 
         if restart_required:

From dc62d743a9d70988483a30b43d29636b289cd552 Mon Sep 17 00:00:00 2001
From: Luc Mcgrady <lucmcgrady@gmail.com>
Date: Tue, 30 Jun 2026 12:29:20 +0100
Subject: [PATCH 6/6] Use protobuf enum

---
 proto/anki/config.proto              | 6 ++++++
 pylib/anki/config.py                 | 5 +++--
 qt/aqt/main.py                       | 3 ++-
 ts/routes/preferences/+page.svelte   | 5 +++--
 ts/routes/preferences/LabItem.svelte | 3 ++-
 5 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/proto/anki/config.proto b/proto/anki/config.proto
index ea115f0fc81..354229789ee 100644
--- a/proto/anki/config.proto
+++ b/proto/anki/config.proto
@@ -66,6 +66,12 @@ message ConfigKey {
   }
 }
 
+enum ExperimentalFeatureFlag {
+  TEST_FLAG = 0;
+  SVELTE_EDITOR = 1;
+  SVELTE_REVIEWER = 2;
+}
+
 message GetConfigBoolRequest {
   ConfigKey.Bool key = 1;
 }
diff --git a/pylib/anki/config.py b/pylib/anki/config.py
index cc7b469f249..c72df83e79d 100644
--- a/pylib/anki/config.py
+++ b/pylib/anki/config.py
@@ -32,6 +32,7 @@
 from anki.utils import from_json_bytes, to_json_bytes
 
 Config = config_pb2.ConfigKey
+ExperimentFlag = config_pb2.ExperimentalFeatureFlag
 
 
 class ConfigManager:
@@ -46,8 +47,8 @@ def get_immutable(self, key: str) -> Any:
         except NotFoundError as exc:
             raise KeyError from exc
 
-    def experiment_enabled(self, key: str) -> bool:
-        return self._experiments.get(key, False)
+    def experiment_enabled(self, key: ExperimentFlag.ValueType) -> bool:
+        return self._experiments.get(str(key), False)
 
     def _get_experiments_dirty(self) -> dict[str, bool]:
         """This fetches the experiments in the state that they are saved in the database.
diff --git a/qt/aqt/main.py b/qt/aqt/main.py
index c3d1a73d831..eecda929978 100644
--- a/qt/aqt/main.py
+++ b/qt/aqt/main.py
@@ -27,6 +27,7 @@
 from anki._legacy import deprecated
 from anki.buildinfo import version as version_str
 from anki.collection import Collection, Config, GithubRelease, OpChanges, UndoStatus
+from anki.config import ExperimentFlag
 from anki.decks import DeckDict, DeckId
 from anki.hooks import runHook
 from anki.notes import NoteId
@@ -527,7 +528,7 @@ def _onsuccess(synced: bool) -> None:
                 onsuccess()
             if not self.safeMode:
                 self.maybe_check_for_addon_updates(self.setup_auto_update)
-            if self.col.conf.experiment_enabled("ping"):
+            if self.col.conf.experiment_enabled(ExperimentFlag.TEST_FLAG):
                 showInfo('You have the "ping" experiment enabled')
 
         last_day_cutoff = self.col.sched.day_cutoff
diff --git a/ts/routes/preferences/+page.svelte b/ts/routes/preferences/+page.svelte
index 5fd25dac231..a5e1200a16b 100644
--- a/ts/routes/preferences/+page.svelte
+++ b/ts/routes/preferences/+page.svelte
@@ -7,6 +7,7 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
     import "../deck-options/deck-options-base.scss";
     import LabItem from "./LabItem.svelte";
     import type { PreferenceStore } from "$lib/sveltelib/preferences";
+    import { ExperimentalFeatureFlag } from "@generated/anki/config_pb";
 
     export let data: { labPerfs: PreferenceStore<any> };
     const labPerfs = data.labPerfs;
@@ -26,13 +27,13 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
         <LabItem
             title="Svelte note editor"
             description="Replaces the legacy editor with a new Svelte-based implementation. May affect addon compatibility."
-            key="svelte-editor"
+            key={ExperimentalFeatureFlag.SVELTE_EDITOR}
             {labPerfs}
         ></LabItem>
         <LabItem
             title="Ping"
             description="Enable this experiment and see an alert every time you load this profile. Used for testing the experiment interface."
-            key="ping"
+            key={ExperimentalFeatureFlag.TEST_FLAG}
             {labPerfs}
         ></LabItem>
     </div>
diff --git a/ts/routes/preferences/LabItem.svelte b/ts/routes/preferences/LabItem.svelte
index 8514f339d75..ca285b977e9 100644
--- a/ts/routes/preferences/LabItem.svelte
+++ b/ts/routes/preferences/LabItem.svelte
@@ -5,10 +5,11 @@ License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
 <script lang="ts">
     import Switch from "$lib/components/Switch.svelte";
     import type { PreferenceStore } from "$lib/sveltelib/preferences";
+    import type { ExperimentalFeatureFlag } from "@generated/anki/config_pb";
 
     export let title: string;
     export let description = "";
-    export let key: string;
+    export let key: ExperimentalFeatureFlag;
     export let labPerfs: PreferenceStore<any>;
     let value = $labPerfs[key];