diff --git a/src/auto-reply/reply/directive-handling.levels.test.ts b/src/auto-reply/reply/directive-handling.levels.test.ts
index 204d2685005..23c8fc9f745 100644
--- a/src/auto-reply/reply/directive-handling.levels.test.ts
+++ b/src/auto-reply/reply/directive-handling.levels.test.ts
@@ -33,4 +33,41 @@ describe("resolveCurrentDirectiveLevels", () => {
     expect(result.currentThinkLevel).toBe("minimal");
     expect(resolveDefaultThinkingLevel).not.toHaveBeenCalled();
   });
+
+  // reasoningDefault tests
+  it("uses agent reasoningDefault when session reasoningLevel is absent", async () => {
+    const result = await resolveCurrentDirectiveLevels({
+      sessionEntry: {},
+      agentCfg: {
+        reasoningDefault: "on",
+      },
+      resolveDefaultThinkingLevel: vi.fn(),
+    });
+
+    expect(result.currentReasoningLevel).toBe("on");
+  });
+
+  it("session reasoningLevel overrides agent reasoningDefault", async () => {
+    const result = await resolveCurrentDirectiveLevels({
+      sessionEntry: {
+        reasoningLevel: "off",
+      },
+      agentCfg: {
+        reasoningDefault: "on",
+      },
+      resolveDefaultThinkingLevel: vi.fn(),
+    });
+
+    expect(result.currentReasoningLevel).toBe("off");
+  });
+
+  it("defaults reasoningLevel to off when neither session nor config is set", async () => {
+    const result = await resolveCurrentDirectiveLevels({
+      sessionEntry: {},
+      agentCfg: {},
+      resolveDefaultThinkingLevel: vi.fn(),
+    });
+
+    expect(result.currentReasoningLevel).toBe("off");
+  });
 });
diff --git a/src/auto-reply/reply/directive-handling.levels.ts b/src/auto-reply/reply/directive-handling.levels.ts
index b62e77c3501..6282c1e1974 100644
--- a/src/auto-reply/reply/directive-handling.levels.ts
+++ b/src/auto-reply/reply/directive-handling.levels.ts
@@ -10,6 +10,7 @@ export async function resolveCurrentDirectiveLevels(params: {
   };
   agentCfg?: {
     thinkingDefault?: unknown;
+    reasoningDefault?: unknown;
     verboseDefault?: unknown;
     elevatedDefault?: unknown;
   };
@@ -32,7 +33,9 @@ export async function resolveCurrentDirectiveLevels(params: {
     (params.sessionEntry?.verboseLevel as VerboseLevel | undefined) ??
     (params.agentCfg?.verboseDefault as VerboseLevel | undefined);
   const currentReasoningLevel =
-    (params.sessionEntry?.reasoningLevel as ReasoningLevel | undefined) ?? "off";
+    (params.sessionEntry?.reasoningLevel as ReasoningLevel | undefined) ??
+    (params.agentCfg?.reasoningDefault as ReasoningLevel | undefined) ??
+    "off";
   const currentElevatedLevel =
     (params.sessionEntry?.elevatedLevel as ElevatedLevel | undefined) ??
     (params.agentCfg?.elevatedDefault as ElevatedLevel | undefined);
diff --git a/src/auto-reply/reply/get-reply-directives.ts b/src/auto-reply/reply/get-reply-directives.ts
index 37eef3fb9b8..3f415a40367 100644
--- a/src/auto-reply/reply/get-reply-directives.ts
+++ b/src/auto-reply/reply/get-reply-directives.ts
@@ -360,6 +360,7 @@ export async function resolveReplyDirectives(params: {
   let resolvedReasoningLevel: ReasoningLevel =
     directives.reasoningLevel ??
     (sessionEntry?.reasoningLevel as ReasoningLevel | undefined) ??
+    (agentCfg?.reasoningDefault as ReasoningLevel | undefined) ??
     "off";
   const resolvedElevatedLevel = elevatedAllowed
     ? (directives.elevatedLevel ??
@@ -412,7 +413,8 @@ export async function resolveReplyDirectives(params: {
   // be emitted as visible "Reasoning:" messages.
   const reasoningExplicitlySet =
     directives.reasoningLevel !== undefined ||
-    (sessionEntry?.reasoningLevel !== undefined && sessionEntry?.reasoningLevel !== null);
+    (sessionEntry?.reasoningLevel !== undefined && sessionEntry?.reasoningLevel !== null) ||
+    agentCfg?.reasoningDefault !== undefined;
   const thinkingActive = resolvedThinkLevelWithDefault !== "off";
   if (!reasoningExplicitlySet && resolvedReasoningLevel === "off" && !thinkingActive) {
     resolvedReasoningLevel = await modelState.resolveDefaultReasoningLevel();
diff --git a/src/auto-reply/status.ts b/src/auto-reply/status.ts
index 1b7aa2a87ec..a0ba5dc4598 100644
--- a/src/auto-reply/status.ts
+++ b/src/auto-reply/status.ts
@@ -512,7 +512,8 @@ export function buildStatusMessage(args: StatusArgs): string {
   const verboseLevel =
     args.resolvedVerbose ?? args.sessionEntry?.verboseLevel ?? args.agent?.verboseDefault ?? "off";
   const fastMode = args.resolvedFast ?? args.sessionEntry?.fastMode ?? false;
-  const reasoningLevel = args.resolvedReasoning ?? args.sessionEntry?.reasoningLevel ?? "off";
+  const reasoningLevel =
+    args.resolvedReasoning ?? args.sessionEntry?.reasoningLevel ?? args.agent?.reasoningDefault ?? "off";
   const elevatedLevel =
     args.resolvedElevated ??
     args.sessionEntry?.elevatedLevel ??
diff --git a/src/config/types.agent-defaults.ts b/src/config/types.agent-defaults.ts
index ecaaecb69b9..165a3a62258 100644
--- a/src/config/types.agent-defaults.ts
+++ b/src/config/types.agent-defaults.ts
@@ -187,6 +187,8 @@ export type AgentDefaultsConfig = {
   memorySearch?: MemorySearchConfig;
   /** Default thinking level when no /think directive is present. */
   thinkingDefault?: "off" | "minimal" | "low" | "medium" | "high" | "xhigh" | "adaptive";
+  /** Default reasoning display level when no /reasoning directive is present. */
+  reasoningDefault?: "off" | "on" | "stream";
   /** Default verbose level when no /verbose directive is present. */
   verboseDefault?: "off" | "on" | "full";
   /** Default elevated level when no /elevated directive is present. */
diff --git a/src/config/zod-schema.agent-defaults.ts b/src/config/zod-schema.agent-defaults.ts
index 836a1fdae91..8f82d636629 100644
--- a/src/config/zod-schema.agent-defaults.ts
+++ b/src/config/zod-schema.agent-defaults.ts
@@ -148,6 +148,9 @@ export const AgentDefaultsSchema = z
         z.literal("adaptive"),
       ])
       .optional(),
+    reasoningDefault: z
+      .union([z.literal("off"), z.literal("on"), z.literal("stream")])
+      .optional(),
     verboseDefault: z.union([z.literal("off"), z.literal("on"), z.literal("full")]).optional(),
     elevatedDefault: z
       .union([z.literal("off"), z.literal("on"), z.literal("ask"), z.literal("full")])