diff --git a/extensions/acpx/src/service.test.ts b/extensions/acpx/src/service.test.ts
index 7cbd5c74945..9b5f0390842 100644
--- a/extensions/acpx/src/service.test.ts
+++ b/extensions/acpx/src/service.test.ts
@@ -276,6 +276,32 @@ describe("createAcpxRuntimeService", () => {
     await service.stop?.(ctx);
   });
 
+  it("formats non-string doctor details without losing object payloads", async () => {
+    const workspaceDir = await makeTempDir();
+    const ctx = createServiceContext(workspaceDir);
+    const runtime = createMockRuntime({
+      doctor: async () => ({
+        ok: false,
+        message: "probe failed",
+        details: [{ code: "ACP_CLOSED", agent: "codex" }, new Error("stdin closed")],
+      }),
+      isHealthy: () => false,
+    });
+    const service = createAcpxRuntimeService({
+      runtimeFactory: () => runtime as never,
+    });
+
+    await service.start(ctx);
+
+    await vi.waitFor(() => {
+      expect(ctx.logger.warn).toHaveBeenCalledWith(
+        'embedded acpx runtime backend probe failed: probe failed ({"code":"ACP_CLOSED","agent":"codex"}; stdin closed)',
+      );
+    });
+
+    await service.stop?.(ctx);
+  });
+
   it("can skip the embedded runtime backend via env", async () => {
     process.env.OPENCLAW_SKIP_ACPX_RUNTIME = "1";
     const workspaceDir = await makeTempDir();
diff --git a/extensions/acpx/src/service.ts b/extensions/acpx/src/service.ts
index c7065a174fe..df0537497fa 100644
--- a/extensions/acpx/src/service.ts
+++ b/extensions/acpx/src/service.ts
@@ -1,4 +1,5 @@
 import fs from "node:fs/promises";
+import { inspect } from "node:util";
 import { formatErrorMessage } from "openclaw/plugin-sdk/error-runtime";
 import type {
   AcpRuntime,
@@ -79,8 +80,36 @@ function warnOnIgnoredLegacyCompatibilityConfig(params: {
   );
 }
 
-function formatDoctorFailureMessage(report: { message: string; details?: string[] }): string {
-  const detailText = report.details?.filter(Boolean).join("; ").trim();
+function formatDoctorDetail(detail: unknown): string | null {
+  if (!detail) {
+    return null;
+  }
+  if (typeof detail === "string") {
+    return detail.trim() || null;
+  }
+  if (detail instanceof Error) {
+    return formatErrorMessage(detail);
+  }
+  if (typeof detail === "object") {
+    try {
+      return JSON.stringify(detail) ?? inspect(detail, { breakLength: Infinity, depth: 3 });
+    } catch {
+      return inspect(detail, { breakLength: Infinity, depth: 3 });
+    }
+  }
+  if (
+    typeof detail === "number" ||
+    typeof detail === "boolean" ||
+    typeof detail === "bigint" ||
+    typeof detail === "symbol"
+  ) {
+    return detail.toString();
+  }
+  return inspect(detail, { breakLength: Infinity, depth: 3 });
+}
+
+function formatDoctorFailureMessage(report: { message: string; details?: unknown[] }): string {
+  const detailText = report.details?.map(formatDoctorDetail).filter(Boolean).join("; ").trim();
   return detailText ? `${report.message} (${detailText})` : report.message;
 }