diff --git a/src/auto-reply/reply/directive-handling.levels.test.ts b/src/auto-reply/reply/directive-handling.levels.test.ts
index 45797d8a0ed..be786cfcdae 100644
--- a/src/auto-reply/reply/directive-handling.levels.test.ts
+++ b/src/auto-reply/reply/directive-handling.levels.test.ts
@@ -121,4 +121,19 @@ describe("resolveCurrentDirectiveLevels", () => {
 
     expect(result.currentReasoningLevel).toBe("off");
   });
+
+  it("respects agent reasoningDefault: off as explicit override", async () => {
+    const resolveDefaultThinkingLevel = vi.fn().mockResolvedValue("off");
+
+    const result = await resolveCurrentDirectiveLevels({
+      sessionEntry: {},
+      agentEntry: {
+        reasoningDefault: "off",
+      },
+      resolveDefaultThinkingLevel,
+    });
+
+    // Agent explicitly setting "off" should be respected, not overridden by model default
+    expect(result.currentReasoningLevel).toBe("off");
+  });
 });
diff --git a/src/auto-reply/reply/get-reply-directives.ts b/src/auto-reply/reply/get-reply-directives.ts
index 9dad0b76875..44ed8990d05 100644
--- a/src/auto-reply/reply/get-reply-directives.ts
+++ b/src/auto-reply/reply/get-reply-directives.ts
@@ -434,11 +434,16 @@ export async function resolveReplyDirectives(params: {
     (agentCfg?.thinkingDefault as ThinkLevel | undefined);
 
   // When neither directive nor session nor agent set reasoning, default to model capability
-  // (e.g. OpenRouter with reasoning: true).
+  // (e.g. OpenRouter with reasoning: true). Skip model default when thinking is active
+  // to avoid redundant Reasoning: output alongside internal thinking blocks.
+  const hasAgentReasoningDefault =
+    agentEntry?.reasoningDefault !== undefined && agentEntry?.reasoningDefault !== null;
   const reasoningExplicitlySet =
     directives.reasoningLevel !== undefined ||
-    (sessionEntry?.reasoningLevel !== undefined && sessionEntry?.reasoningLevel !== null);
-  if (!reasoningExplicitlySet && resolvedReasoningLevel === "off") {
+    (sessionEntry?.reasoningLevel !== undefined && sessionEntry?.reasoningLevel !== null) ||
+    hasAgentReasoningDefault;
+  const thinkingActive = resolvedThinkLevelWithDefault !== "off";
+  if (!reasoningExplicitlySet && resolvedReasoningLevel === "off" && !thinkingActive) {
     resolvedReasoningLevel = await modelState.resolveDefaultReasoningLevel();
   }