diff --git a/src/auto-reply/reply.directive.test.ts b/src/auto-reply/reply.directive.test.ts
index 8ee37bc32..70a940ddf 100644
--- a/src/auto-reply/reply.directive.test.ts
+++ b/src/auto-reply/reply.directive.test.ts
@@ -190,9 +190,50 @@ describe("directive behavior", () => {
     });
   });
 
-  it("shows off when /think has no argument and no default set", async () => {
+  it("defaults /think to low for reasoning-capable models when no default set", async () => {
     await withTempHome(async (home) => {
       vi.mocked(runEmbeddedPiAgent).mockReset();
+      vi.mocked(loadModelCatalog).mockResolvedValueOnce([
+        {
+          id: "claude-opus-4-5",
+          name: "Opus 4.5",
+          provider: "anthropic",
+          reasoning: true,
+        },
+      ]);
+
+      const res = await getReplyFromConfig(
+        { Body: "/think", From: "+1222", To: "+1222" },
+        {},
+        {
+          agents: {
+            defaults: {
+              model: "anthropic/claude-opus-4-5",
+              workspace: path.join(home, "clawd"),
+            },
+          },
+          session: { store: path.join(home, "sessions.json") },
+        },
+      );
+
+      const text = Array.isArray(res) ? res[0]?.text : res?.text;
+      expect(text).toContain("Current thinking level: low");
+      expect(text).toContain("Options: off, minimal, low, medium, high.");
+      expect(runEmbeddedPiAgent).not.toHaveBeenCalled();
+    });
+  });
+
+  it("shows off when /think has no argument and model lacks reasoning", async () => {
+    await withTempHome(async (home) => {
+      vi.mocked(runEmbeddedPiAgent).mockReset();
+      vi.mocked(loadModelCatalog).mockResolvedValueOnce([
+        {
+          id: "claude-opus-4-5",
+          name: "Opus 4.5",
+          provider: "anthropic",
+          reasoning: false,
+        },
+      ]);
 
       const res = await getReplyFromConfig(
         { Body: "/think", From: "+1222", To: "+1222" },
diff --git a/src/auto-reply/reply.ts b/src/auto-reply/reply.ts
index 05c2ea186..78b2b134b 100644
--- a/src/auto-reply/reply.ts
+++ b/src/auto-reply/reply.ts
@@ -673,7 +673,8 @@ export async function getReplyFromConfig(
   ) {
     const currentThinkLevel =
       (sessionEntry?.thinkingLevel as ThinkLevel | undefined) ??
-      (agentCfg?.thinkingDefault as ThinkLevel | undefined);
+      (agentCfg?.thinkingDefault as ThinkLevel | undefined) ??
+      (await modelState.resolveDefaultThinkingLevel());
     const currentVerboseLevel =
       (sessionEntry?.verboseLevel as VerboseLevel | undefined) ??
       (agentCfg?.verboseDefault as VerboseLevel | undefined);