diff --git a/src/core/server/http/base_path_proxy_server.ts b/src/core/server/http/base_path_proxy_server.ts
index 737aab00cff0e..d461abe54ccbd 100644
--- a/src/core/server/http/base_path_proxy_server.ts
+++ b/src/core/server/http/base_path_proxy_server.ts
@@ -52,6 +52,14 @@ export class BasePathProxyServer {
     return this.devConfig.basePathProxyTargetPort;
   }
 
+  public get host() {
+    return this.httpConfig.host;
+  }
+
+  public get port() {
+    return this.httpConfig.port;
+  }
+
   constructor(
     private readonly log: Logger,
     private readonly httpConfig: HttpConfig,
@@ -92,7 +100,10 @@ export class BasePathProxyServer {
     await this.server.start();
 
     this.log.info(
-      `basepath proxy server running at ${this.server.info.uri}${this.httpConfig.basePath}`
+      `basepath proxy server running at ${Url.format({
+        host: this.server.info.uri,
+        pathname: this.httpConfig.basePath,
+      })}`
     );
   }
 
diff --git a/src/dev/cli_dev_mode/cli_dev_mode.test.ts b/src/dev/cli_dev_mode/cli_dev_mode.test.ts
index b86100d161bd3..a6905df8d0c27 100644
--- a/src/dev/cli_dev_mode/cli_dev_mode.test.ts
+++ b/src/dev/cli_dev_mode/cli_dev_mode.test.ts
@@ -95,6 +95,7 @@ it('passes correct args to sub-classes', () => {
           ],
           "gracefulTimeout": 5000,
           "log": <TestLog>,
+          "mapLogLine": [Function],
           "script": <absolute path>/scripts/kibana,
           "watcher": Watcher {
             "serverShouldRestart$": [MockFunction],
diff --git a/src/dev/cli_dev_mode/cli_dev_mode.ts b/src/dev/cli_dev_mode/cli_dev_mode.ts
index 3cb97b08b75c2..58d5e499f189b 100644
--- a/src/dev/cli_dev_mode/cli_dev_mode.ts
+++ b/src/dev/cli_dev_mode/cli_dev_mode.ts
@@ -21,7 +21,7 @@ import Path from 'path';
 
 import { REPO_ROOT } from '@kbn/dev-utils';
 import * as Rx from 'rxjs';
-import { mapTo, filter, take } from 'rxjs/operators';
+import { mapTo, filter, take, tap, distinctUntilChanged, switchMap } from 'rxjs/operators';
 
 import { CliArgs } from '../../core/server/config';
 import { LegacyConfig } from '../../core/server/legacy';
@@ -142,6 +142,15 @@ export class CliDevMode {
             ]
           : []),
       ],
+      mapLogLine: (line) => {
+        if (!this.basePathProxy) {
+          return line;
+        }
+
+        return line
+          .split(`${this.basePathProxy.host}:${this.basePathProxy.targetPort}`)
+          .join(`${this.basePathProxy.host}:${this.basePathProxy.port}`);
+      },
     });
 
     this.optimizer = new Optimizer({
@@ -168,10 +177,41 @@ export class CliDevMode {
     this.subscription = new Rx.Subscription();
 
     if (basePathProxy) {
-      const delay$ = firstAllTrue(this.devServer.isReady$(), this.optimizer.isReady$());
+      const serverReady$ = new Rx.BehaviorSubject(false);
+      const optimizerReady$ = new Rx.BehaviorSubject(false);
+      const userWaiting$ = new Rx.BehaviorSubject(false);
+
+      this.subscription.add(
+        Rx.merge(
+          this.devServer.isReady$().pipe(tap(serverReady$)),
+          this.optimizer.isReady$().pipe(tap(optimizerReady$)),
+          userWaiting$.pipe(
+            distinctUntilChanged(),
+            switchMap((waiting) =>
+              !waiting
+                ? Rx.EMPTY
+                : Rx.timer(1000).pipe(
+                    tap(() => {
+                      this.log.warn(
+                        'please hold',
+                        !optimizerReady$.getValue()
+                          ? 'optimizer is still bundling so requests have been paused'
+                          : 'server is not ready so requests have been paused'
+                      );
+                    })
+                  )
+            )
+          )
+        ).subscribe(this.observer('readiness checks'))
+      );
 
       basePathProxy.start({
-        delayUntil: () => delay$,
+        delayUntil: () => {
+          userWaiting$.next(true);
+          return firstAllTrue(serverReady$, optimizerReady$).pipe(
+            tap(() => userWaiting$.next(false))
+          );
+        },
         shouldRedirectFromOldBasePath,
       });
 
diff --git a/src/dev/cli_dev_mode/dev_server.ts b/src/dev/cli_dev_mode/dev_server.ts
index da64c680a3c2d..f832acd38c641 100644
--- a/src/dev/cli_dev_mode/dev_server.ts
+++ b/src/dev/cli_dev_mode/dev_server.ts
@@ -45,6 +45,7 @@ export interface Options {
   processExit$?: Rx.Observable<void>;
   sigint$?: Rx.Observable<void>;
   sigterm$?: Rx.Observable<void>;
+  mapLogLine?: DevServer['mapLogLine'];
 }
 
 export class DevServer {
@@ -59,6 +60,7 @@ export class DevServer {
   private readonly script: string;
   private readonly argv: string[];
   private readonly gracefulTimeout: number;
+  private readonly mapLogLine?: (line: string) => string | null;
 
   constructor(options: Options) {
     this.log = options.log;
@@ -70,6 +72,7 @@ export class DevServer {
     this.processExit$ = options.processExit$ ?? Rx.fromEvent(process as EventEmitter, 'exit');
     this.sigint$ = options.sigint$ ?? Rx.fromEvent(process as EventEmitter, 'SIGINT');
     this.sigterm$ = options.sigterm$ ?? Rx.fromEvent(process as EventEmitter, 'SIGTERM');
+    this.mapLogLine = options.mapLogLine;
   }
 
   isReady$() {
@@ -124,8 +127,11 @@ export class DevServer {
         // observable which emits devServer states containing lines
         // logged to stdout/stderr, completes when stdio streams complete
         const log$ = Rx.merge(observeLines(proc.stdout!), observeLines(proc.stderr!)).pipe(
-          tap((line) => {
-            this.log.write(line);
+          tap((observedLine) => {
+            const line = this.mapLogLine ? this.mapLogLine(observedLine) : observedLine;
+            if (line !== null) {
+              this.log.write(line);
+            }
           })
         );