feat: add default variant support in settings and UI components

packages/desktop/src-tauri/src/commands/settings.rs

@@ -234,13 +234,27 @@ fn sanitize_settings_update(payload: &Value) -> Value {
             }
         }
         if let Some(Value::String(s)) = obj.get("defaultModel") {
-            if !s.is_empty() {
+            let trimmed = s.trim();
-                result_obj.insert("defaultModel".to_string(), json!(s));
+            if trimmed.is_empty() {
+                result_obj.insert("defaultModel".to_string(), Value::Null);
+            } else {
+                result_obj.insert("defaultModel".to_string(), json!(trimmed));
+            }
+        }
+        if let Some(Value::String(s)) = obj.get("defaultVariant") {
+            let trimmed = s.trim();
+            if trimmed.is_empty() {
+                result_obj.insert("defaultVariant".to_string(), Value::Null);
+            } else {
+                result_obj.insert("defaultVariant".to_string(), json!(trimmed));
             }
         }
         if let Some(Value::String(s)) = obj.get("defaultAgent") {
-            if !s.is_empty() {
+            let trimmed = s.trim();
-                result_obj.insert("defaultAgent".to_string(), json!(s));
+            if trimmed.is_empty() {
+                result_obj.insert("defaultAgent".to_string(), Value::Null);
+            } else {
+                result_obj.insert("defaultAgent".to_string(), json!(trimmed));
             }
         }
 

packages/ui/src/components/chat/ModelControls.tsx

@@ -276,6 +276,7 @@ export const ModelControls: React.FC<ModelControlsProps> = ({ className }) => {
         currentModelId,
         currentVariant,
         currentAgentName,
+        settingsDefaultVariant,
         setProvider,
         setModel,
         setCurrentVariant,
@@ -865,7 +866,7 @@ export const ModelControls: React.FC<ModelControlsProps> = ({ className }) => {
     }, [currentAgentName, currentSessionId, getAgentModelForSession, tryApplyModelSelection, agents, contextHydrated]);
 
     React.useEffect(() => {
-        if (!contextHydrated || !currentSessionId || !currentAgentName) {
+        if (!contextHydrated || !currentAgentName) {
             setCurrentVariant(undefined);
             return;
         }
@@ -875,6 +876,28 @@ export const ModelControls: React.FC<ModelControlsProps> = ({ className }) => {
             return;
         }
 
+        if (availableVariants.length === 0) {
+            setCurrentVariant(undefined);
+            return;
+        }
+
+        if (currentVariant && !availableVariants.includes(currentVariant)) {
+            setCurrentVariant(undefined);
+            return;
+        }
+
+        // Draft state (no session yet): seed from settings default, but don't override
+        // user selection while drafting.
+        if (!currentSessionId) {
+            if (!currentVariant) {
+                const desired = settingsDefaultVariant && availableVariants.includes(settingsDefaultVariant)
+                    ? settingsDefaultVariant
+                    : undefined;
+                setCurrentVariant(desired);
+            }
+            return;
+        }
+
         const savedVariant = getAgentModelVariantForSession(
             currentSessionId,
             currentAgentName,
@@ -882,12 +905,11 @@ export const ModelControls: React.FC<ModelControlsProps> = ({ className }) => {
             currentModelId,
         );
 
-        if (savedVariant && !availableVariants.includes(savedVariant)) {
+        const resolvedSaved = savedVariant && availableVariants.includes(savedVariant)
-            setCurrentVariant(undefined);
+            ? savedVariant
-            return;
+            : undefined;
-        }
 
-        setCurrentVariant(savedVariant);
+        setCurrentVariant(resolvedSaved);
     }, [
         availableVariants,
         contextHydrated,
@@ -895,8 +917,10 @@ export const ModelControls: React.FC<ModelControlsProps> = ({ className }) => {
         currentAgentName,
         currentProviderId,
         currentModelId,
+        currentVariant,
         getAgentModelVariantForSession,
         setCurrentVariant,
+        settingsDefaultVariant,
     ]);
 
     const handleVariantSelect = React.useCallback((variant: string | undefined) => {

packages/ui/src/components/sections/openchamber/DefaultsSettings.tsx

@@ -3,6 +3,7 @@ import { RiInformationLine } from '@remixicon/react';
 import { Tooltip, TooltipContent, TooltipTrigger } from '@/components/ui/tooltip';
 import { ModelSelector } from '@/components/sections/agents/ModelSelector';
 import { AgentSelector } from '@/components/sections/commands/AgentSelector';
+import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from '@/components/ui/select';
 import { updateDesktopSettings } from '@/lib/persistence';
 import { isDesktopRuntime, getDesktopSettings } from '@/lib/desktop';
 import { useConfigStore } from '@/stores/useConfigStore';
@@ -13,13 +14,16 @@ export const DefaultsSettings: React.FC = () => {
   const setProvider = useConfigStore((state) => state.setProvider);
   const setModel = useConfigStore((state) => state.setModel);
   const setAgent = useConfigStore((state) => state.setAgent);
+  const setCurrentVariant = useConfigStore((state) => state.setCurrentVariant);
   const setSettingsDefaultModel = useConfigStore((state) => state.setSettingsDefaultModel);
+  const setSettingsDefaultVariant = useConfigStore((state) => state.setSettingsDefaultVariant);
   const setSettingsDefaultAgent = useConfigStore((state) => state.setSettingsDefaultAgent);
   const settingsAutoCreateWorktree = useConfigStore((state) => state.settingsAutoCreateWorktree);
   const setSettingsAutoCreateWorktree = useConfigStore((state) => state.setSettingsAutoCreateWorktree);
   const providers = useConfigStore((state) => state.providers);
 
   const [defaultModel, setDefaultModel] = React.useState<string | undefined>();
+  const [defaultVariant, setDefaultVariant] = React.useState<string | undefined>();
   const [defaultAgent, setDefaultAgent] = React.useState<string | undefined>();
   const [isLoading, setIsLoading] = React.useState(true);
 
@@ -35,7 +39,7 @@ export const DefaultsSettings: React.FC = () => {
   React.useEffect(() => {
     const loadSettings = async () => {
       try {
-        let data: { defaultModel?: string; defaultAgent?: string } | null = null;
+        let data: { defaultModel?: string; defaultVariant?: string; defaultAgent?: string } | null = null;
 
         // 1. Desktop runtime (Tauri)
         if (isDesktopRuntime()) {
@@ -50,6 +54,7 @@ export const DefaultsSettings: React.FC = () => {
               if (settings) {
                 data = {
                   defaultModel: typeof settings.defaultModel === 'string' ? settings.defaultModel : undefined,
+                  defaultVariant: typeof (settings as Record<string, unknown>).defaultVariant === 'string' ? ((settings as Record<string, unknown>).defaultVariant as string) : undefined,
                   defaultAgent: typeof settings.defaultAgent === 'string' ? settings.defaultAgent : undefined,
                 };
               }
@@ -71,8 +76,13 @@ export const DefaultsSettings: React.FC = () => {
         }
 
         if (data) {
-          setDefaultModel(data.defaultModel);
+          const model = typeof data.defaultModel === 'string' && data.defaultModel.trim().length > 0 ? data.defaultModel.trim() : undefined;
-          setDefaultAgent(data.defaultAgent);
+          const variant = typeof data.defaultVariant === 'string' && data.defaultVariant.trim().length > 0 ? data.defaultVariant.trim() : undefined;
+          const agent = typeof data.defaultAgent === 'string' && data.defaultAgent.trim().length > 0 ? data.defaultAgent.trim() : undefined;
+
+          setDefaultModel(model);
+          setDefaultVariant(variant);
+          setDefaultAgent(agent);
         }
       } catch (error) {
         console.warn('Failed to load defaults settings:', error);
@@ -87,6 +97,11 @@ export const DefaultsSettings: React.FC = () => {
     const newValue = providerId && modelId ? `${providerId}/${modelId}` : undefined;
     setDefaultModel(newValue);
 
+    // Reset variant when model changes (model-specific)
+    setDefaultVariant(undefined);
+    setSettingsDefaultVariant(undefined);
+    setCurrentVariant(undefined);
+
     // Update config store settings default (used by setAgent logic)
     setSettingsDefaultModel(newValue);
 
@@ -102,11 +117,29 @@ export const DefaultsSettings: React.FC = () => {
     try {
       await updateDesktopSettings({
         defaultModel: newValue ?? '',
+        defaultVariant: '',
       });
     } catch (error) {
       console.warn('Failed to save default model:', error);
     }
-  }, [providers, setProvider, setModel, setSettingsDefaultModel]);
+  }, [providers, setCurrentVariant, setProvider, setModel, setSettingsDefaultModel, setSettingsDefaultVariant]);
+
+  const DEFAULT_VARIANT_VALUE = '__default__';
+
+  const handleVariantChange = React.useCallback(async (variant: string) => {
+    const newValue = variant === DEFAULT_VARIANT_VALUE ? undefined : (variant || undefined);
+    setDefaultVariant(newValue);
+    setSettingsDefaultVariant(newValue);
+    setCurrentVariant(newValue);
+
+    try {
+      await updateDesktopSettings({
+        defaultVariant: newValue ?? '',
+      });
+    } catch (error) {
+      console.warn('Failed to save default variant:', error);
+    }
+  }, [setCurrentVariant, setSettingsDefaultVariant]);
 
   const handleAgentChange = React.useCallback(async (agentName: string) => {
     const newValue = agentName || undefined;
@@ -129,6 +162,31 @@ export const DefaultsSettings: React.FC = () => {
     }
   }, [setAgent, setSettingsDefaultAgent]);
 
+  const availableVariants = React.useMemo(() => {
+    const provider = providers.find((p) => p.id === parsedModel.providerId);
+    const model = provider?.models.find((m: Record<string, unknown>) => (m as { id?: string }).id === parsedModel.modelId) as
+      | { variants?: Record<string, unknown> }
+      | undefined;
+    const variants = model?.variants;
+    if (!variants) {
+      return [];
+    }
+    return Object.keys(variants);
+  }, [parsedModel.modelId, parsedModel.providerId, providers]);
+
+  const supportsVariants = availableVariants.length > 0;
+
+  React.useEffect(() => {
+    if (!supportsVariants && defaultVariant) {
+      setDefaultVariant(undefined);
+      setSettingsDefaultVariant(undefined);
+      setCurrentVariant(undefined);
+      updateDesktopSettings({ defaultVariant: '' }).catch(() => {
+        // best effort
+      });
+    }
+  }, [defaultVariant, setCurrentVariant, setSettingsDefaultVariant, supportsVariants]);
+
   const handleAutoWorktreeChange = React.useCallback(async (e: React.ChangeEvent<HTMLInputElement>) => {
     const enabled = e.target.checked;
     setSettingsAutoCreateWorktree(enabled);
@@ -161,29 +219,53 @@ export const DefaultsSettings: React.FC = () => {
         </div>
       </div>
 
-      <div className="space-y-3">
+        <div className="space-y-3">
-        <div className="flex flex-col gap-1.5">
+         <div className="flex flex-col gap-1.5">
-          <label className="typography-ui-label text-muted-foreground">Default model</label>
+           <label className="typography-ui-label text-muted-foreground">Default model</label>
-          <ModelSelector
+           <ModelSelector
-            providerId={parsedModel.providerId}
+             providerId={parsedModel.providerId}
-            modelId={parsedModel.modelId}
+             modelId={parsedModel.modelId}
-            onChange={handleModelChange}
+             onChange={handleModelChange}
-          />
+           />
-        </div>
+         </div>
 
-        <div className="flex flex-col gap-1.5">
+         {supportsVariants && (
-          <label className="typography-ui-label text-muted-foreground">Default agent</label>
+           <div className="flex flex-col gap-1.5">
-          <AgentSelector
+             <label className="typography-ui-label text-muted-foreground">Default thinking</label>
-            agentName={defaultAgent || ''}
+             <Select value={defaultVariant ?? DEFAULT_VARIANT_VALUE} onValueChange={handleVariantChange}>
-            onChange={handleAgentChange}
+               <SelectTrigger className="w-auto max-w-xs typography-meta text-foreground">
-          />
+                 <SelectValue placeholder="Thinking" />
-        </div>
+               </SelectTrigger>
-      </div>
+               <SelectContent>
+                 <SelectItem value={DEFAULT_VARIANT_VALUE} className="pr-2 [&>span:first-child]:hidden">Default</SelectItem>
+                 {availableVariants.map((variant) => (
+                   <SelectItem key={variant} value={variant} className="pr-2 [&>span:first-child]:hidden">
+                     {variant}
+                   </SelectItem>
+                 ))}
+               </SelectContent>
+             </Select>
+           </div>
+         )}
+ 
+         <div className="flex flex-col gap-1.5">
+           <label className="typography-ui-label text-muted-foreground">Default agent</label>
+           <AgentSelector
+             agentName={defaultAgent || ''}
+             onChange={handleAgentChange}
+           />
+         </div>
+       </div>
 
       {(defaultModel || defaultAgent) && (
         <div className="typography-meta text-muted-foreground">
           New sessions will start with:{' '}
-          {defaultModel && <span className="text-foreground">{defaultModel}</span>}
+          {defaultModel && (
+            <span className="text-foreground">
+              {defaultModel}
+              {supportsVariants ? ` (${defaultVariant ?? 'default'})` : ''}
+            </span>
+          )}
           {defaultModel && defaultAgent && ' / '}
           {defaultAgent && <span className="text-foreground">{defaultAgent}</span>}
         </div>

packages/ui/src/lib/desktop.ts

@@ -54,6 +54,7 @@ export type DesktopSettings = {
   autoDeleteEnabled?: boolean;
   autoDeleteAfterDays?: number;
   defaultModel?: string; // format: "provider/model"
+  defaultVariant?: string;
   defaultAgent?: string;
   autoCreateWorktree?: boolean;
   queueModeEnabled?: boolean;

packages/ui/src/lib/persistence.ts

@@ -252,6 +252,9 @@ const sanitizeWebSettings = (payload: unknown): DesktopSettings | null => {
   if (typeof candidate.defaultModel === 'string' && candidate.defaultModel.length > 0) {
     result.defaultModel = candidate.defaultModel;
   }
+  if (typeof candidate.defaultVariant === 'string' && candidate.defaultVariant.length > 0) {
+    result.defaultVariant = candidate.defaultVariant;
+  }
   if (typeof candidate.defaultAgent === 'string' && candidate.defaultAgent.length > 0) {
     result.defaultAgent = candidate.defaultAgent;
   }

packages/ui/src/lib/worktreeSessionCreator.ts

@@ -160,6 +160,24 @@ export async function createWorktreeSession(): Promise<{ id: string } | null> {
               useContextStore.getState().saveSessionModelSelection(session.id, providerId, modelId);
               // Also save the specific agent's model preference for this session
               useContextStore.getState().saveAgentModelForSession(session.id, agentName, providerId, modelId);
+
+              // Seed default variant into session context so ModelControls restore logic
+              // doesn't wipe it on first switch to the new session.
+              const settingsDefaultVariant = configState.settingsDefaultVariant;
+              if (settingsDefaultVariant) {
+                const provider = configState.providers.find((p) => p.id === providerId);
+                const model = provider?.models.find((m: Record<string, unknown>) => (m as { id?: string }).id === modelId) as
+                  | { variants?: Record<string, unknown> }
+                  | undefined;
+                const variants = model?.variants;
+
+                if (variants && Object.prototype.hasOwnProperty.call(variants, settingsDefaultVariant)) {
+                  configState.setCurrentVariant(settingsDefaultVariant);
+                  useContextStore
+                    .getState()
+                    .saveAgentModelVariantForSession(session.id, agentName, providerId, modelId, settingsDefaultVariant);
+                }
+              }
             }
           }
         }

packages/ui/src/stores/useConfigStore.ts

@@ -22,6 +22,7 @@ const FALLBACK_MODEL_ID = "big-pickle";
 
 interface OpenChamberDefaults {
     defaultModel?: string;
+    defaultVariant?: string;
     defaultAgent?: string;
     autoCreateWorktree?: boolean;
 }
@@ -33,6 +34,7 @@ const fetchOpenChamberDefaults = async (): Promise<OpenChamberDefaults> => {
             const settings = await getDesktopSettings();
             return {
                 defaultModel: settings?.defaultModel,
+                defaultVariant: settings?.defaultVariant,
                 defaultAgent: settings?.defaultAgent,
                 autoCreateWorktree: settings?.autoCreateWorktree,
             };
@@ -45,9 +47,14 @@ const fetchOpenChamberDefaults = async (): Promise<OpenChamberDefaults> => {
                 const result = await runtimeSettings.load();
                 const data = result?.settings;
                 if (data) {
+                    const defaultModel = typeof data?.defaultModel === 'string' ? data.defaultModel.trim() : '';
+                    const defaultVariant = typeof data?.defaultVariant === 'string' ? data.defaultVariant.trim() : '';
+                    const defaultAgent = typeof data?.defaultAgent === 'string' ? data.defaultAgent.trim() : '';
+
                     return {
-                        defaultModel: typeof data?.defaultModel === 'string' ? data.defaultModel : undefined,
+                        defaultModel: defaultModel.length > 0 ? defaultModel : undefined,
-                        defaultAgent: typeof data?.defaultAgent === 'string' ? data.defaultAgent : undefined,
+                        defaultVariant: defaultVariant.length > 0 ? defaultVariant : undefined,
+                        defaultAgent: defaultAgent.length > 0 ? defaultAgent : undefined,
                         autoCreateWorktree: typeof data?.autoCreateWorktree === 'boolean' ? data.autoCreateWorktree : undefined,
                     };
                 }
@@ -65,9 +72,14 @@ const fetchOpenChamberDefaults = async (): Promise<OpenChamberDefaults> => {
             return {};
         }
         const data = await response.json();
+        const defaultModel = typeof data?.defaultModel === 'string' ? data.defaultModel.trim() : '';
+        const defaultVariant = typeof data?.defaultVariant === 'string' ? data.defaultVariant.trim() : '';
+        const defaultAgent = typeof data?.defaultAgent === 'string' ? data.defaultAgent.trim() : '';
+
         return {
-            defaultModel: typeof data?.defaultModel === 'string' ? data.defaultModel : undefined,
+            defaultModel: defaultModel.length > 0 ? defaultModel : undefined,
-            defaultAgent: typeof data?.defaultAgent === 'string' ? data.defaultAgent : undefined,
+            defaultVariant: defaultVariant.length > 0 ? defaultVariant : undefined,
+            defaultAgent: defaultAgent.length > 0 ? defaultAgent : undefined,
             autoCreateWorktree: typeof data?.autoCreateWorktree === 'boolean' ? data.autoCreateWorktree : undefined,
         };
     } catch {
@@ -326,10 +338,12 @@ const resolveInitialDirectoryKey = (): string => {
 };
 
 interface DirectoryScopedConfig {
+
     providers: ProviderWithModelList[];
     agents: Agent[];
     currentProviderId: string;
     currentModelId: string;
+    currentVariant?: string | undefined;
     currentAgentName: string | undefined;
     selectedProviderId: string;
     agentModelSelections: { [agentName: string]: { providerId: string; modelId: string } };
@@ -355,6 +369,7 @@ interface ConfigStore {
     modelsMetadata: Map<string, ModelMetadata>;
     // OpenChamber settings-based defaults (take precedence over agent preferences)
     settingsDefaultModel: string | undefined; // format: "provider/model"
+    settingsDefaultVariant: string | undefined;
     settingsDefaultAgent: string | undefined;
     settingsAutoCreateWorktree: boolean;
 
@@ -370,6 +385,7 @@ interface ConfigStore {
     setAgent: (agentName: string | undefined) => void;
     setSelectedProvider: (providerId: string) => void;
     setSettingsDefaultModel: (model: string | undefined) => void;
+    setSettingsDefaultVariant: (variant: string | undefined) => void;
     setSettingsDefaultAgent: (agent: string | undefined) => void;
     setSettingsAutoCreateWorktree: (enabled: boolean) => void;
     saveAgentModelSelection: (agentName: string, providerId: string, modelId: string) => void;
@@ -412,6 +428,7 @@ export const useConfigStore = create<ConfigStore>()(
                 isInitialized: false,
                 modelsMetadata: new Map<string, ModelMetadata>(),
                 settingsDefaultModel: undefined,
+                settingsDefaultVariant: undefined,
                 settingsDefaultAgent: undefined,
                 settingsAutoCreateWorktree: false,
 
@@ -427,6 +444,7 @@ export const useConfigStore = create<ConfigStore>()(
                                 agents: snapshot.agents,
                                 currentProviderId: snapshot.currentProviderId,
                                 currentModelId: snapshot.currentModelId,
+                                currentVariant: snapshot.currentVariant,
                                 currentAgentName: snapshot.currentAgentName,
                                 selectedProviderId: snapshot.selectedProviderId,
                                 agentModelSelections: snapshot.agentModelSelections,
@@ -564,14 +582,14 @@ export const useConfigStore = create<ConfigStore>()(
                 setProvider: (providerId: string) => {
                     const { providers } = get();
                     const provider = providers.find((p) => p.id === providerId);
-
+ 
                     if (!provider) {
                         return;
                     }
-
+ 
                     const firstModel = provider.models[0];
                     const newModelId = firstModel?.id || "";
-
+ 
                     set((state) => {
                         const directoryKey = state.activeDirectoryKey;
                         const baseSnapshot: DirectoryScopedConfig = state.directoryScoped[directoryKey] ?? {
@@ -579,6 +597,7 @@ export const useConfigStore = create<ConfigStore>()(
                             agents: state.agents,
                             currentProviderId: state.currentProviderId,
                             currentModelId: state.currentModelId,
+                            currentVariant: state.currentVariant,
                             currentAgentName: state.currentAgentName,
                             selectedProviderId: state.selectedProviderId,
                             agentModelSelections: state.agentModelSelections,
@@ -612,6 +631,7 @@ export const useConfigStore = create<ConfigStore>()(
                             agents: state.agents,
                             currentProviderId: state.currentProviderId,
                             currentModelId: state.currentModelId,
+                            currentVariant: state.currentVariant,
                             currentAgentName: state.currentAgentName,
                             selectedProviderId: state.selectedProviderId,
                             agentModelSelections: state.agentModelSelections,
@@ -638,7 +658,32 @@ export const useConfigStore = create<ConfigStore>()(
                         if (state.currentVariant === variant) {
                             return state;
                         }
-                        return { currentVariant: variant };
+
+                        const directoryKey = state.activeDirectoryKey;
+                        const baseSnapshot: DirectoryScopedConfig = state.directoryScoped[directoryKey] ?? {
+                            providers: state.providers,
+                            agents: state.agents,
+                            currentProviderId: state.currentProviderId,
+                            currentModelId: state.currentModelId,
+                            currentVariant: state.currentVariant,
+                            currentAgentName: state.currentAgentName,
+                            selectedProviderId: state.selectedProviderId,
+                            agentModelSelections: state.agentModelSelections,
+                            defaultProviders: state.defaultProviders,
+                        };
+
+                        const nextSnapshot: DirectoryScopedConfig = {
+                            ...baseSnapshot,
+                            currentVariant: variant,
+                        };
+
+                        return {
+                            currentVariant: variant,
+                            directoryScoped: {
+                                ...state.directoryScoped,
+                                [directoryKey]: nextSnapshot,
+                            },
+                        };
                     });
                 },
 
@@ -659,18 +704,17 @@ export const useConfigStore = create<ConfigStore>()(
 
                     const current = get().currentVariant;
                     if (!current) {
-                        set((state) => (state.currentVariant === variantKeys[0] ? state : { currentVariant: variantKeys[0] }));
+                        get().setCurrentVariant(variantKeys[0]);
-                        return;
-                    }
- 
-                    const index = variantKeys.indexOf(current);
-                    if (index === -1 || index === variantKeys.length - 1) {
-                        set((state) => (state.currentVariant === undefined ? state : { currentVariant: undefined }));
                         return;
                     }
 
-                    const nextVariant = variantKeys[index + 1];
+                    const index = variantKeys.indexOf(current);
-                    set((state) => (state.currentVariant === nextVariant ? state : { currentVariant: nextVariant }));
+                    if (index === -1 || index === variantKeys.length - 1) {
+                        get().setCurrentVariant(undefined);
+                        return;
+                    }
+
+                    get().setCurrentVariant(variantKeys[index + 1]);
                 },
  
                 setSelectedProvider: (providerId: string) => {
@@ -780,9 +824,10 @@ export const useConfigStore = create<ConfigStore>()(
                                 };
 
                                 const nextState: Partial<ConfigStore> = {
-                                    settingsDefaultModel: openChamberDefaults.defaultModel,
+                                     settingsDefaultModel: openChamberDefaults.defaultModel,
-                                    settingsDefaultAgent: openChamberDefaults.defaultAgent,
+                                     settingsDefaultVariant: openChamberDefaults.defaultVariant,
-                                    settingsAutoCreateWorktree: openChamberDefaults.autoCreateWorktree ?? false,
+                                     settingsDefaultAgent: openChamberDefaults.defaultAgent,
+                                     settingsAutoCreateWorktree: openChamberDefaults.autoCreateWorktree ?? false,
                                     directoryScoped: {
                                         ...state.directoryScoped,
                                         [directoryKey]: nextSnapshot,
@@ -801,9 +846,10 @@ export const useConfigStore = create<ConfigStore>()(
                                     const baseSnapshot: DirectoryScopedConfig = state.directoryScoped[directoryKey] ?? {
                                         providers,
                                         agents: [],
-                                        currentProviderId: "",
+                            currentProviderId: "",
-                                        currentModelId: "",
+                            currentModelId: "",
-                                        currentAgentName: undefined,
+                            currentVariant: undefined,
+                            currentAgentName: undefined,
                                         selectedProviderId: "",
                                         agentModelSelections: {},
                                         defaultProviders: {},
@@ -849,7 +895,7 @@ export const useConfigStore = create<ConfigStore>()(
                             let resolvedAgent: Agent = fallbackAgent;
 
                             // Track invalid settings to clear
-                            const invalidSettings: { defaultModel?: string; defaultAgent?: string } = {};
+                             const invalidSettings: { defaultModel?: string; defaultVariant?: string; defaultAgent?: string } = {};
 
                             // 1. Check OpenChamber settings for default agent
                             if (openChamberDefaults.defaultAgent) {
@@ -862,22 +908,34 @@ export const useConfigStore = create<ConfigStore>()(
                                 }
                             }
 
-                            // --- Model Selection ---
+                             // --- Model Selection ---
-                            // Priority: settings.defaultModel → agent's preferred model → opencode/big-pickle
+                             // Priority: settings.defaultModel → agent's preferred model → opencode/big-pickle
-                            let resolvedProviderId: string | undefined;
+                             let resolvedProviderId: string | undefined;
-                            let resolvedModelId: string | undefined;
+                             let resolvedModelId: string | undefined;
+                             let resolvedVariant: string | undefined;
 
-                            // 1. Check OpenChamber settings for default model
+                             // 1. Check OpenChamber settings for default model
-                            if (openChamberDefaults.defaultModel) {
+                             if (openChamberDefaults.defaultModel) {
-                                const parsed = parseModelString(openChamberDefaults.defaultModel);
+                                 const parsed = parseModelString(openChamberDefaults.defaultModel);
-                                if (parsed && validateModel(parsed.providerId, parsed.modelId)) {
+                                 if (parsed && validateModel(parsed.providerId, parsed.modelId)) {
-                                    resolvedProviderId = parsed.providerId;
+                                     resolvedProviderId = parsed.providerId;
-                                    resolvedModelId = parsed.modelId;
+                                     resolvedModelId = parsed.modelId;
-                                } else {
+
-                                    // Model no longer exists - mark for clearing
+                                     if (openChamberDefaults.defaultVariant) {
-                                    invalidSettings.defaultModel = '';
+                                         const provider = providers.find((p) => p.id === parsed.providerId);
-                                }
+                                         const model = provider?.models.find((m) => m.id === parsed.modelId) as { variants?: Record<string, unknown> } | undefined;
-                            }
+                                         const variants = model?.variants;
+                                         if (variants && Object.prototype.hasOwnProperty.call(variants, openChamberDefaults.defaultVariant)) {
+                                             resolvedVariant = openChamberDefaults.defaultVariant;
+                                         } else {
+                                             invalidSettings.defaultVariant = '';
+                                         }
+                                     }
+                                 } else {
+                                     // Model no longer exists - mark for clearing
+                                     invalidSettings.defaultModel = '';
+                                 }
+                             }
 
                             // 2. Fall back to agent's preferred model
                             if (!resolvedProviderId && resolvedAgent?.model?.providerID && resolvedAgent?.model?.modelID) {
@@ -919,8 +977,9 @@ export const useConfigStore = create<ConfigStore>()(
                                     providers,
                                     agents: safeAgents,
                                     currentAgentName: resolvedAgent.name,
-                                    currentProviderId: resolvedProviderId ?? baseSnapshot.currentProviderId,
+                                     currentProviderId: resolvedProviderId ?? baseSnapshot.currentProviderId,
-                                    currentModelId: resolvedModelId ?? baseSnapshot.currentModelId,
+                                     currentModelId: resolvedModelId ?? baseSnapshot.currentModelId,
+                                     currentVariant: resolvedVariant,
                                 };
 
                                 const nextState: Partial<ConfigStore> = {
@@ -930,13 +989,14 @@ export const useConfigStore = create<ConfigStore>()(
                                     },
                                 };
 
-                                if (state.activeDirectoryKey === directoryKey) {
+                                 if (state.activeDirectoryKey === directoryKey) {
-                                    nextState.currentAgentName = resolvedAgent.name;
+                                     nextState.currentAgentName = resolvedAgent.name;
-                                    if (resolvedProviderId && resolvedModelId) {
+                                     if (resolvedProviderId && resolvedModelId) {
-                                        nextState.currentProviderId = resolvedProviderId;
+                                         nextState.currentProviderId = resolvedProviderId;
-                                        nextState.currentModelId = resolvedModelId;
+                                         nextState.currentModelId = resolvedModelId;
-                                    }
+                                         nextState.currentVariant = resolvedVariant;
-                                }
+                                     }
+                                 }
 
                                 return nextState;
                             });
@@ -944,10 +1004,11 @@ export const useConfigStore = create<ConfigStore>()(
                             // Clear invalid settings from storage (best-effort cleanup)
                             if (Object.keys(invalidSettings).length > 0) {
                                 // Also clear from store state
-                                set({
+                                 set({
-                                    settingsDefaultModel: invalidSettings.defaultModel !== undefined ? undefined : get().settingsDefaultModel,
+                                     settingsDefaultModel: invalidSettings.defaultModel !== undefined ? undefined : get().settingsDefaultModel,
-                                    settingsDefaultAgent: invalidSettings.defaultAgent !== undefined ? undefined : get().settingsDefaultAgent,
+                                     settingsDefaultVariant: invalidSettings.defaultVariant !== undefined ? undefined : get().settingsDefaultVariant,
-                                });
+                                     settingsDefaultAgent: invalidSettings.defaultAgent !== undefined ? undefined : get().settingsDefaultAgent,
+                                 });
                                 updateDesktopSettings(invalidSettings).catch(() => {
                                     // Ignore errors - best effort cleanup
                                 });
@@ -1003,7 +1064,7 @@ export const useConfigStore = create<ConfigStore>()(
                 },
 
                 setAgent: (agentName: string | undefined) => {
-                    const { agents, providers, settingsDefaultModel } = get();
+                    const { agents, providers, settingsDefaultModel, settingsDefaultVariant } = get();
 
                     set((state) => {
                         const directoryKey = state.activeDirectoryKey;
@@ -1086,21 +1147,34 @@ export const useConfigStore = create<ConfigStore>()(
                                             agents: state.agents,
                                             currentProviderId: state.currentProviderId,
                                             currentModelId: state.currentModelId,
+                                            currentVariant: state.currentVariant,
                                             currentAgentName: state.currentAgentName,
                                             selectedProviderId: state.selectedProviderId,
                                             agentModelSelections: state.agentModelSelections,
                                             defaultProviders: state.defaultProviders,
                                         };
 
+                                        let nextVariant: string | undefined;
+                                        if (settingsDefaultVariant) {
+                                            const settingsProvider = providers.find((p) => p.id === parsed.providerId);
+                                            const model = settingsProvider?.models.find((m) => m.id === parsed.modelId) as { variants?: Record<string, unknown> } | undefined;
+                                            const variants = model?.variants;
+                                            if (variants && Object.prototype.hasOwnProperty.call(variants, settingsDefaultVariant)) {
+                                                nextVariant = settingsDefaultVariant;
+                                            }
+                                        }
+
                                         const nextSnapshot: DirectoryScopedConfig = {
                                             ...baseSnapshot,
                                             currentProviderId: parsed.providerId,
                                             currentModelId: parsed.modelId,
+                                            currentVariant: nextVariant,
                                         };
 
                                         return {
                                             currentProviderId: parsed.providerId,
                                             currentModelId: parsed.modelId,
+                                            currentVariant: nextVariant,
                                             directoryScoped: {
                                                 ...state.directoryScoped,
                                                 [directoryKey]: nextSnapshot,
@@ -1156,13 +1230,17 @@ export const useConfigStore = create<ConfigStore>()(
                     }
                 },
 
-                setSettingsDefaultModel: (model: string | undefined) => {
+                 setSettingsDefaultModel: (model: string | undefined) => {
-                    set({ settingsDefaultModel: model });
+                     set({ settingsDefaultModel: model });
-                },
+                 },
 
-                setSettingsDefaultAgent: (agent: string | undefined) => {
+                 setSettingsDefaultVariant: (variant: string | undefined) => {
-                    set({ settingsDefaultAgent: agent });
+                     set({ settingsDefaultVariant: variant });
-                },
+                 },
+ 
+                 setSettingsDefaultAgent: (agent: string | undefined) => {
+                     set({ settingsDefaultAgent: agent });
+                 },
 
                 setSettingsAutoCreateWorktree: (enabled: boolean) => {
                     set({ settingsAutoCreateWorktree: enabled });

packages/vscode/src/bridge.ts

@@ -80,6 +80,15 @@ const persistSettings = async (changes: Record<string, unknown>, ctx?: BridgeCon
   const current = readSettings(ctx);
   const restChanges = { ...(changes || {}) };
   delete restChanges.lastDirectory;
+
+  // Normalize empty-string clears to key removal (match web/desktop behavior)
+  for (const key of ['defaultModel', 'defaultVariant', 'defaultAgent']) {
+    const value = restChanges[key];
+    if (typeof value === 'string' && value.trim().length === 0) {
+      delete restChanges[key];
+    }
+  }
+
   const merged = { ...current, ...restChanges, lastDirectory: current.lastDirectory };
   await ctx?.context?.globalState.update(SETTINGS_KEY, merged);
   return merged;

packages/web/server/index.js

@@ -590,11 +590,17 @@ const sanitizeSettingsUpdate = (payload) => {
     result.typographySizes = typography;
   }
 
-  if (typeof candidate.defaultModel === 'string' && candidate.defaultModel.length > 0) {
+  if (typeof candidate.defaultModel === 'string') {
-    result.defaultModel = candidate.defaultModel;
+    const trimmed = candidate.defaultModel.trim();
+    result.defaultModel = trimmed.length > 0 ? trimmed : undefined;
   }
-  if (typeof candidate.defaultAgent === 'string' && candidate.defaultAgent.length > 0) {
+  if (typeof candidate.defaultVariant === 'string') {
-    result.defaultAgent = candidate.defaultAgent;
+    const trimmed = candidate.defaultVariant.trim();
+    result.defaultVariant = trimmed.length > 0 ? trimmed : undefined;
+  }
+  if (typeof candidate.defaultAgent === 'string') {
+    const trimmed = candidate.defaultAgent.trim();
+    result.defaultAgent = trimmed.length > 0 ? trimmed : undefined;
   }
   if (typeof candidate.queueModeEnabled === 'boolean') {
     result.queueModeEnabled = candidate.queueModeEnabled;