PostHog · MattPua · Jul 6, 2026
diff --git a/packages/ui/src/features/sessions/hooks/useAvailableModelOptions.ts b/packages/ui/src/features/sessions/hooks/useAvailableModelOptions.ts
@@ -0,0 +1,37 @@
+import { useHostTRPC } from "@posthog/host-router/react";
+import { flattenSelectOptions, getCloudUrlFromRegion } from "@posthog/shared";
+import { useAuthStateValue } from "@posthog/ui/features/auth/store";
+import { useQuery } from "@tanstack/react-query";
+import { useMemo } from "react";
+
+export interface ModelOption {
+  value: string;
+  name: string;
+}
+
+export function useAvailableModelOptions(
+  adapter: "claude" | "codex",
+): ModelOption[] {
+  const hostTRPC = useHostTRPC();
+  const cloudRegion = useAuthStateValue((state) => state.cloudRegion);
+  const apiHost = useMemo(
+    () => (cloudRegion ? getCloudUrlFromRegion(cloudRegion) : null),
+    [cloudRegion],
+  );
+
+  const { data: configOptions } = useQuery({
+    ...hostTRPC.agent.getPreviewConfigOptions.queryOptions({
+      apiHost: apiHost ?? "",
+      adapter,
+    }),
+    enabled: !!apiHost,
+  });
+
+  return useMemo(() => {
+    const modelOpt = configOptions?.find(
+      (o) => o.category === "model" || o.id === "model",
+    );
+    if (!modelOpt || modelOpt.type !== "select") return [];
+    return flattenSelectOptions(modelOpt.options);
+  }, [configOptions]);
+}
diff --git a/packages/ui/src/features/settings/sections/GeneralSettings.tsx b/packages/ui/src/features/settings/sections/GeneralSettings.tsx
@@ -7,11 +7,13 @@ import {
   COLLAPSE_MODE_OPTIONS,
   type CollapseMode,
 } from "@posthog/ui/features/sessions/components/new-thread/conversationThreadConfig";
+import { useAvailableModelOptions } from "@posthog/ui/features/sessions/hooks/useAvailableModelOptions";
 import { SettingRow } from "@posthog/ui/features/settings/SettingRow";
 import {
   type AutoConvertLongText,
   type DefaultInitialTaskMode,
   type DefaultMessagingMode,
+  type DefaultModel,
   type DefaultReasoningEffort,
   type DiffOpenMode,
   type SendMessagesWith,
@@ -71,6 +73,7 @@ export function GeneralSettings() {
     autoConvertLongText,
     defaultInitialTaskMode,
     defaultMessagingMode,
+    defaultModels,
     defaultReasoningEffort,
     diffOpenMode,
     sendMessagesWith,
@@ -81,6 +84,7 @@ export function GeneralSettings() {
     setAutoConvertLongText,
     setDefaultInitialTaskMode,
     setDefaultMessagingMode,
+    setDefaultModel,
     setDefaultReasoningEffort,
     setDiffOpenMode,
     setSendMessagesWith,
@@ -90,6 +94,9 @@ export function GeneralSettings() {
     setBrainrotMode,
   } = useSettingsStore();
 
+  const claudeModelOptions = useAvailableModelOptions("claude");
+  const codexModelOptions = useAvailableModelOptions("codex");
+
   // Appearance handlers
   const handleThemeChange = useCallback(
     (value: ThemePreference) => {
@@ -164,6 +171,18 @@ export function GeneralSettings() {
     [defaultReasoningEffort, setDefaultReasoningEffort],
   );
 
+  const handleDefaultModelChange = useCallback(
+    (adapter: "claude" | "codex", value: DefaultModel) => {
+      track(ANALYTICS_EVENTS.SETTING_CHANGED, {
+        setting_name: "default_model",
+        new_value: value,
+        old_value: defaultModels[adapter] ?? "last_used",
+      });
+      setDefaultModel(adapter, value);
+    },
+    [defaultModels, setDefaultModel],
+  );
+
   const handleConversationCollapseModeChange = useCallback(
     (value: CollapseMode) => {
       track(ANALYTICS_EVENTS.SETTING_CHANGED, {
@@ -311,6 +330,55 @@ export function GeneralSettings() {
         </Select.Root>
       </SettingRow>
 
+      <SettingRow
+        label="Default Claude model"
+        description="Choose the default model for new Claude tasks, or remember your last-used model"
+      >
+        <Select.Root
+          value={defaultModels.claude ?? "last_used"}
+          onValueChange={(value) =>
+            handleDefaultModelChange("claude", value as DefaultModel)
+          }
+          size="1"
+          disabled={claudeModelOptions.length === 0}
+        >
+          <Select.Trigger className="min-w-[140px]" />
+          <Select.Content>
+            <Select.Item value="last_used">Last used</Select.Item>
+            {claudeModelOptions.map((opt) => (
+              <Select.Item key={opt.value} value={opt.value}>
+                {opt.name}
+              </Select.Item>
+            ))}
+          </Select.Content>
+        </Select.Root>
+      </SettingRow>
+
+      {codexModelOptions.length > 0 && (
+        <SettingRow
+          label="Default Codex model"
+          description="Choose the default model for new Codex tasks, or remember your last-used model"
+        >
+          <Select.Root
+            value={defaultModels.codex ?? "last_used"}
+            onValueChange={(value) =>
+              handleDefaultModelChange("codex", value as DefaultModel)
+            }
+            size="1"
+          >
+            <Select.Trigger className="min-w-[140px]" />
+            <Select.Content>
+              <Select.Item value="last_used">Last used</Select.Item>
+              {codexModelOptions.map((opt) => (
+                <Select.Item key={opt.value} value={opt.value}>
+                  {opt.name}
+                </Select.Item>
+              ))}
+            </Select.Content>
+          </Select.Root>
+        </SettingRow>
+      )}
+
       <SettingRow
         label="Default effort level"
         description="Choose the default reasoning effort for new tasks, or remember your last-used level"

diff --git a/packages/ui/src/features/settings/settingsStore.ts b/packages/ui/src/features/settings/settingsStore.ts
@@ -23,6 +23,8 @@ export type DefaultReasoningEffort =
   | "max"
   | "last_used";
 
+export type DefaultModel = string | "last_used";
+
 export type SendMessagesWith = "enter" | "cmd+enter";
 export type AutoConvertLongText = "off" | "1000" | "2500" | "5000" | "10000";
 export type DiffOpenMode = "auto" | "split" | "same-pane" | "last-active-pane";
@@ -91,6 +93,7 @@ interface SettingsStore {
   // Mode last chosen when approving a plan; pre-selected on the next approval.
   lastPlanApprovalMode: ExecutionMode | null;
   defaultReasoningEffort: DefaultReasoningEffort;
+  defaultModels: Partial<Record<"claude" | "codex", DefaultModel>>;
   defaultMessagingMode: DefaultMessagingMode;
   setDefaultMessagingMode: (mode: DefaultMessagingMode) => void;
   setDefaultRunMode: (mode: DefaultRunMode) => void;
@@ -113,6 +116,7 @@ interface SettingsStore {
   setLastUsedInitialTaskMode: (mode: ExecutionMode) => void;
   setLastPlanApprovalMode: (mode: ExecutionMode) => void;
   setDefaultReasoningEffort: (effort: DefaultReasoningEffort) => void;
+  setDefaultModel: (adapter: "claude" | "codex", model: DefaultModel) => void;
 
   // Notifications
   desktopNotifications: boolean;
@@ -228,6 +232,7 @@ export const useSettingsStore = create<SettingsStore>()(
       lastUsedInitialTaskMode: "plan",
       lastPlanApprovalMode: null,
       defaultReasoningEffort: "last_used",
+      defaultModels: {},
       defaultMessagingMode: "queue",
       setDefaultRunMode: (mode) => set({ defaultRunMode: mode }),
       setLastUsedRunMode: (mode) => set({ lastUsedRunMode: mode }),
@@ -261,6 +266,10 @@ export const useSettingsStore = create<SettingsStore>()(
       setLastPlanApprovalMode: (mode) => set({ lastPlanApprovalMode: mode }),
       setDefaultReasoningEffort: (effort) =>
         set({ defaultReasoningEffort: effort }),
+      setDefaultModel: (adapter, model) =>
+        set((state) => ({
+          defaultModels: { ...state.defaultModels, [adapter]: model },
+        })),
       setDefaultMessagingMode: (mode) => set({ defaultMessagingMode: mode }),
 
       // Notifications

diff --git a/packages/ui/src/features/task-detail/hooks/usePreviewConfig.ts b/packages/ui/src/features/task-detail/hooks/usePreviewConfig.ts
@@ -89,8 +89,10 @@ export function usePreviewConfig(
           lastUsedInitialTaskMode,
           defaultReasoningEffort,
           lastUsedReasoningEffort,
+          defaultModels,
           lastUsedModel,
         } = useSettingsStore.getState();
+        const defaultModel = defaultModels[adapter] ?? "last_used";
 
         let initial = deriveInitialConfig(
           options,
@@ -107,19 +109,22 @@ export function usePreviewConfig(
         // without this the user's last pick (e.g. fable) is lost on every
         // refetch/remount. Restore it through applyConfigChange so the dependent
         // effort options are recomputed for the restored model.
+        // If defaultModel is set (not "last_used"), prefer it over lastUsedModel.
+        const targetModel =
+          defaultModel !== "last_used" ? defaultModel : lastUsedModel;
         const modelOpt = getOptionByCategory(initial, "model");
         if (
-          lastUsedModel &&
+          targetModel &&
           modelOpt?.type === "select" &&
-          modelOpt.currentValue !== lastUsedModel &&
-          flattenConfigValues(modelOpt).includes(lastUsedModel)
+          modelOpt.currentValue !== targetModel &&
+          flattenConfigValues(modelOpt).includes(targetModel)
         ) {
           initial = applyConfigChange(initial, {
             adapter,
             configId: modelOpt.id,
-            value: lastUsedModel,
+            value: targetModel,
             effortOptions:
-              getReasoningEffortOptions(adapter, lastUsedModel) ?? undefined,
+              getReasoningEffortOptions(adapter, targetModel) ?? undefined,
             settings: {
               defaultInitialTaskMode: "",
               lastUsedInitialTaskMode: undefined,