diff --git a/apps/code/src/main/services/agent/service.ts b/apps/code/src/main/services/agent/service.ts
index af80ec302..e4d20e86f 100644
--- a/apps/code/src/main/services/agent/service.ts
+++ b/apps/code/src/main/services/agent/service.ts
@@ -1773,7 +1773,7 @@ For git operations while detached:
         id: adapter === "codex" ? "reasoning_effort" : "effort",
         name: adapter === "codex" ? "Reasoning Level" : "Effort",
         type: "select",
-        currentValue: "high",
+        currentValue: adapter === "codex" ? "high" : "medium",
         options: effortOpts,
         category: "thought_level",
         description:
diff --git a/apps/code/src/renderer/features/task-detail/hooks/usePreviewConfig.ts b/apps/code/src/renderer/features/task-detail/hooks/usePreviewConfig.ts
index f9f496107..86b6c80c9 100644
--- a/apps/code/src/renderer/features/task-detail/hooks/usePreviewConfig.ts
+++ b/apps/code/src/renderer/features/task-detail/hooks/usePreviewConfig.ts
@@ -141,13 +141,14 @@ export function usePreviewConfig(
                 ? "reasoning_effort"
                 : "effort";
 
+          const defaultEffort = adapter === "codex" ? "high" : "medium";
           if (effortOpts && existingIdx >= 0) {
             const currentEffort = updated[existingIdx].currentValue;
             const validEffort = effortOpts.some(
               (e) => e.value === currentEffort,
             )
               ? currentEffort
-              : "high";
+              : defaultEffort;
             updated[existingIdx] = {
               ...updated[existingIdx],
               currentValue: validEffort,
@@ -160,7 +161,7 @@ export function usePreviewConfig(
                 id: effortOptionId,
                 name: adapter === "codex" ? "Reasoning Level" : "Effort",
                 type: "select",
-                currentValue: "high",
+                currentValue: defaultEffort,
                 options: effortOpts,
                 category: "thought_level",
                 description:
diff --git a/packages/agent/src/adapters/claude/claude-agent.ts b/packages/agent/src/adapters/claude/claude-agent.ts
index a715cb510..a48808630 100644
--- a/packages/agent/src/adapters/claude/claude-agent.ts
+++ b/packages/agent/src/adapters/claude/claude-agent.ts
@@ -1309,7 +1309,7 @@ export class ClaudeAcpAgent extends BaseAcpAgent {
     const configOptions = this.buildConfigOptions(
       permissionMode,
       modelOptions,
-      effort ?? "high",
+      effort ?? "medium",
     );
     session.configOptions = configOptions;
 
@@ -1406,7 +1406,7 @@ export class ClaudeAcpAgent extends BaseAcpAgent {
       currentModelId: string;
       options: SessionConfigSelectOption[];
     },
-    currentEffort: EffortLevel = "high",
+    currentEffort: EffortLevel = "medium",
   ): SessionConfigOption[] {
     const modeOptions = getAvailableModes().map((mode) => ({
       value: mode.id,