diff --git a/src/util/diplomat.ts b/src/util/diplomat.ts
index bfecb4b..a41108b 100644
--- a/src/util/diplomat.ts
+++ b/src/util/diplomat.ts
@@ -4,6 +4,23 @@ import { rootLogger } from './logger';
 
 const logger = rootLogger.child({ source: 'diplomat-sdk' });
 
+const FALLBACK_WARN_TTL_MS = 5 * 60 * 1000;
+const fallbackWarnLastFiredAt = new Map<string, number>();
+
+function shouldWarnForFallback(installId: string): boolean {
+  const now = Date.now();
+  const lastFiredAt = fallbackWarnLastFiredAt.get(installId);
+  if (lastFiredAt !== undefined && now - lastFiredAt < FALLBACK_WARN_TTL_MS) {
+    return false;
+  }
+  fallbackWarnLastFiredAt.set(installId, now);
+  return true;
+}
+
+export function resetDiplomatFallbackWarnCacheForTesting(): void {
+  fallbackWarnLastFiredAt.clear();
+}
+
 /**
  * Diplomat Latest Response Format (current)
  */
@@ -65,9 +82,7 @@ export function isDiplomatV1Response(response: DiplomatServerResponse): response
 /**
  * Type guard to check if response is Latest format
  */
-export function isDiplomatLatestResponse(
-  response: DiplomatServerResponse,
-): response is DiplomatServerResponseLatest {
+export function isDiplomatLatestResponse(response: DiplomatServerResponse): response is DiplomatServerResponseLatest {
   return 'status' in response && 'headers' in response && 'body' in response;
 }
 
@@ -131,23 +146,25 @@ export async function getDiplomatClientInstall(installId?: string): Promise<Dipl
 
     return response.data;
   } catch (err: unknown) {
-    // Log the error but return null to fall back to direct routing
+    // Falling back to direct routing is the expected path for non-Diplomat
+    // installs, so the per-request log is debug. A single warn per installId
+    // every 5 minutes preserves operator visibility without the volume.
+    const baseMetadata: Record<string, unknown> = {
+      install_id: installId,
+      diplomat_version: diplomatVersion,
+      diplomat_server_url: serverUrl,
+    };
     if (axios.isAxiosError(err)) {
-      logger.warn('Diplomat server check failed - falling back to direct routing', {
-        install_id: installId,
-        diplomat_version: diplomatVersion,
-        diplomat_server_url: serverUrl,
-        status_code: err.response?.status,
-        error_message: err.message,
-        error_code: err.code,
-      });
+      baseMetadata.status_code = err.response?.status;
+      baseMetadata.error_message = err.message;
+      baseMetadata.error_code = err.code;
     } else {
-      logger.warn('Diplomat server check failed - falling back to direct routing', {
-        install_id: installId,
-        diplomat_version: diplomatVersion,
-        diplomat_server_url: serverUrl,
-        error_message: err instanceof Error ? err.message : String(err),
-      });
+      baseMetadata.error_message = err instanceof Error ? err.message : String(err);
+    }
+
+    logger.debug('Diplomat server check failed - falling back to direct routing', baseMetadata);
+    if (shouldWarnForFallback(installId)) {
+      logger.warn('Diplomat server check failed - falling back to direct routing', baseMetadata);
     }
 
     return null;
diff --git a/test/util/diplomat.test.ts b/test/util/diplomat.test.ts
new file mode 100644
index 0000000..5b2cb00
--- /dev/null
+++ b/test/util/diplomat.test.ts
@@ -0,0 +1,95 @@
+import axios from 'axios';
+import { resetDiplomatFallbackWarnCacheForTesting, getDiplomatClientInstall } from '../../src/util/diplomat';
+
+jest.mock('axios');
+const mockedAxios = axios as jest.Mocked<typeof axios>;
+
+const MS_PER_MINUTE = 60 * 1000;
+const FALLBACK_MESSAGE = 'Diplomat server check failed - falling back to direct routing';
+
+type LoggedEntry = { level: string; message: string; install_id?: string };
+
+function parseLogged(spy: jest.SpyInstance): LoggedEntry[] {
+  return spy.mock.calls
+    .map((args) => {
+      try {
+        return JSON.parse(args[0] as string) as LoggedEntry;
+      } catch {
+        return null;
+      }
+    })
+    .filter((entry): entry is LoggedEntry => entry !== null);
+}
+
+describe('getDiplomatClientInstall — fallback log behavior', () => {
+  let consoleLogSpy: jest.SpyInstance;
+  let consoleWarnSpy: jest.SpyInstance;
+  let dateNowSpy: jest.SpyInstance;
+  let now: number;
+
+  beforeEach(() => {
+    process.env.DIPLOMAT_SERVER_URL = 'https://diplomat.example.com';
+    process.env.DIPLOMAT_SERVER_AUTH_USERNAME = 'user';
+    process.env.DIPLOMAT_SERVER_AUTH_PASSWORD = 'pass';
+
+    resetDiplomatFallbackWarnCacheForTesting();
+
+    consoleLogSpy = jest.spyOn(console, 'log').mockImplementation(() => {});
+    consoleWarnSpy = jest.spyOn(console, 'warn').mockImplementation(() => {});
+
+    now = 1_000_000_000_000;
+    dateNowSpy = jest.spyOn(Date, 'now').mockImplementation(() => now);
+
+    mockedAxios.create.mockReturnValue({
+      get: jest.fn().mockRejectedValue(Object.assign(new Error('boom'), { isAxiosError: true, code: 'ECONNREFUSED' })),
+    } as unknown as ReturnType<typeof axios.create>);
+    (mockedAxios.isAxiosError as unknown as jest.Mock).mockImplementation(
+      (err: unknown) => !!(err && (err as { isAxiosError?: boolean }).isAxiosError),
+    );
+  });
+
+  afterEach(() => {
+    consoleLogSpy.mockRestore();
+    consoleWarnSpy.mockRestore();
+    dateNowSpy.mockRestore();
+  });
+
+  it('logs debug on every fallback and warns only once per installId within 5 minutes', async () => {
+    await getDiplomatClientInstall('install-1');
+    await getDiplomatClientInstall('install-1');
+    await getDiplomatClientInstall('install-1');
+
+    const debugs = parseLogged(consoleLogSpy).filter((e) => e.message === FALLBACK_MESSAGE && e.level === 'debug');
+    const warns = parseLogged(consoleWarnSpy).filter((e) => e.message === FALLBACK_MESSAGE);
+    expect(debugs).toHaveLength(3);
+    expect(warns).toHaveLength(1);
+    expect(warns[0].install_id).toBe('install-1');
+  });
+
+  it('warns again for the same installId after the 5-minute window', async () => {
+    await getDiplomatClientInstall('install-1');
+    let warns = parseLogged(consoleWarnSpy).filter((e) => e.message === FALLBACK_MESSAGE);
+    expect(warns).toHaveLength(1);
+
+    now += 4 * MS_PER_MINUTE + 59_000;
+    await getDiplomatClientInstall('install-1');
+    warns = parseLogged(consoleWarnSpy).filter((e) => e.message === FALLBACK_MESSAGE);
+    expect(warns).toHaveLength(1);
+
+    now += 2_000;
+    await getDiplomatClientInstall('install-1');
+    warns = parseLogged(consoleWarnSpy).filter((e) => e.message === FALLBACK_MESSAGE);
+    expect(warns).toHaveLength(2);
+  });
+
+  it('warns independently per installId', async () => {
+    await getDiplomatClientInstall('install-1');
+    await getDiplomatClientInstall('install-2');
+    await getDiplomatClientInstall('install-1');
+    await getDiplomatClientInstall('install-2');
+
+    const warns = parseLogged(consoleWarnSpy).filter((e) => e.message === FALLBACK_MESSAGE);
+    expect(warns).toHaveLength(2);
+    expect(warns.map((w) => w.install_id).sort()).toEqual(['install-1', 'install-2']);
+  });
+});