diff --git a/open-sse/executors/codebuddy-cn.js b/open-sse/executors/codebuddy-cn.js
index 46e51951..5f37d015 100644
--- a/open-sse/executors/codebuddy-cn.js
+++ b/open-sse/executors/codebuddy-cn.js
@@ -25,10 +25,14 @@ export class CodeBuddyExecutor extends DefaultExecutor {
     const eff = transformed.reasoning_effort;
     if (eff === "none" || eff === "off") {
       delete transformed.reasoning_effort; // gateway has no "none" — just omit
-    } else {
-      if (!eff) transformed.reasoning_effort = "medium";
+    } else if (eff) {
+      // Client explicitly asked for reasoning — mirror the CLI's reasoning_summary
+      // so CodeBuddy surfaces the model's reasoning.
       transformed.reasoning_summary = "auto";
     }
+    // No reasoning requested: leave both unset. Forcing reasoning_effort:"medium"
+    // + reasoning_summary on plain requests makes CodeBuddy trip its content
+    // filter and return an error (#2071).
     return transformed;
   }
 }
diff --git a/tests/unit/codebuddy-reasoning-optin.test.js b/tests/unit/codebuddy-reasoning-optin.test.js
new file mode 100644
index 00000000..1bfaf15b
--- /dev/null
+++ b/tests/unit/codebuddy-reasoning-optin.test.js
@@ -0,0 +1,37 @@
+// #2071 — CodeBuddy forced reasoning_effort:"medium" + reasoning_summary:"auto"
+// on requests where the client never asked for reasoning, tripping CodeBuddy's
+// content filter ("model return error"). Reasoning params must be opt-in.
+import { describe, it, expect } from "vitest";
+import { CodeBuddyExecutor } from "../../open-sse/executors/codebuddy-cn.js";
+
+describe("CodeBuddyExecutor reasoning params are opt-in (#2071)", () => {
+  const exec = new CodeBuddyExecutor();
+
+  it("does NOT force reasoning when the client did not request it", () => {
+    const out = exec.transformRequest("glm-5.2", { messages: [{ role: "user", content: "hi" }] }, false, {});
+    expect(out.reasoning_effort).toBeUndefined();
+    expect(out.reasoning_summary).toBeUndefined();
+  });
+
+  it("mirrors reasoning_summary:auto when the client explicitly requested reasoning", () => {
+    const out = exec.transformRequest(
+      "glm-5.2",
+      { messages: [{ role: "user", content: "hi" }], reasoning_effort: "high" },
+      false,
+      {}
+    );
+    expect(out.reasoning_effort).toBe("high");
+    expect(out.reasoning_summary).toBe("auto");
+  });
+
+  it("omits reasoning_effort for none/off and adds no reasoning_summary", () => {
+    const out = exec.transformRequest(
+      "glm-5.2",
+      { messages: [{ role: "user", content: "hi" }], reasoning_effort: "none" },
+      false,
+      {}
+    );
+    expect(out.reasoning_effort).toBeUndefined();
+    expect(out.reasoning_summary).toBeUndefined();
+  });
+});