diff --git a/packages/ui/src/components/sections/agents/AgentsPage.tsx b/packages/ui/src/components/sections/agents/AgentsPage.tsx
index 5686a5d5..a78f7110 100644
--- a/packages/ui/src/components/sections/agents/AgentsPage.tsx
+++ b/packages/ui/src/components/sections/agents/AgentsPage.tsx
@@ -504,8 +504,8 @@ export const AgentsPage: React.FC = () => {
       const modeValue = agentDraft.mode || 'subagent';
       const modelValue = agentDraft.model || '';
       const variantValue = agentDraft.variant || '';
-      const temperatureValue = agentDraft.temperature;
-      const topPValue = agentDraft.top_p;
+      const temperatureValue = agentDraft.temperature ?? undefined;
+      const topPValue = agentDraft.top_p ?? undefined;
       const promptValue = agentDraft.prompt || '';
 
       setDraftName(draftNameValue);
@@ -628,8 +628,8 @@ export const AgentsPage: React.FC = () => {
         mode,
         model: trimmedModel === '' ? null : trimmedModel,
         variant: trimmedVariant === '' ? null : trimmedVariant || undefined,
-        temperature,
-        top_p: topP,
+        temperature: temperature ?? null,
+        top_p: topP ?? null,
         prompt: trimmedPrompt || (isNewAgent ? undefined : null),
         permission: permissionConfig,
         scope: isNewAgent ? draftScope : undefined,
diff --git a/packages/ui/src/stores/useAgentsStore.ts b/packages/ui/src/stores/useAgentsStore.ts
index ef31b65c..29f3e6ef 100644
--- a/packages/ui/src/stores/useAgentsStore.ts
+++ b/packages/ui/src/stores/useAgentsStore.ts
@@ -105,8 +105,8 @@ export interface AgentConfig {
   description?: string;
   model?: string | null;
   variant?: string | null;
-  temperature?: number;
-  top_p?: number;
+  temperature?: number | null;
+  top_p?: number | null;
   prompt?: string | null;
   mode?: "primary" | "subagent" | "all";
   permission?: PermissionConfig | null;
@@ -172,8 +172,8 @@ export interface AgentDraft {
   description?: string;
   model?: string | null;
   variant?: string;
-  temperature?: number;
-  top_p?: number;
+  temperature?: number | null;
+  top_p?: number | null;
   prompt?: string;
   mode?: "primary" | "subagent" | "all";
   permission?: PermissionConfig;
@@ -334,8 +334,8 @@ export const useAgentsStore = create<AgentsStore>()(
             if (config.description) agentConfig.description = config.description;
             if (config.model) agentConfig.model = config.model;
             if (config.variant) agentConfig.variant = config.variant;
-            if (config.temperature !== undefined) agentConfig.temperature = config.temperature;
-            if (config.top_p !== undefined) agentConfig.top_p = config.top_p;
+            if (config.temperature !== undefined) agentConfig.temperature = config.temperature ?? null;
+            if (config.top_p !== undefined) agentConfig.top_p = config.top_p ?? null;
             if (config.prompt) agentConfig.prompt = config.prompt;
             if (config.permission) agentConfig.permission = config.permission;
             if (config.disable !== undefined) agentConfig.disable = config.disable;
@@ -399,8 +399,8 @@ export const useAgentsStore = create<AgentsStore>()(
             if (config.description !== undefined) agentConfig.description = config.description;
             if (config.model !== undefined) agentConfig.model = config.model;
             if ('variant' in config) agentConfig.variant = config.variant ?? null;
-            if (config.temperature !== undefined) agentConfig.temperature = config.temperature;
-            if (config.top_p !== undefined) agentConfig.top_p = config.top_p;
+            if ('temperature' in config) agentConfig.temperature = config.temperature ?? null;
+            if ('top_p' in config) agentConfig.top_p = config.top_p ?? null;
             if (config.prompt !== undefined) agentConfig.prompt = config.prompt;
             if (config.permission !== undefined) agentConfig.permission = config.permission;
             if (config.disable !== undefined) agentConfig.disable = config.disable;