diff --git a/lib/services/bundled_mining_service.dart b/lib/services/bundled_mining_service.dart
index be30c08..b243d09 100644
--- a/lib/services/bundled_mining_service.dart
+++ b/lib/services/bundled_mining_service.dart
@@ -1,6 +1,7 @@
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
+import 'dart:math' as math;
 
 import 'package:logger/logger.dart';
 import 'package:path/path.dart' as p;
@@ -142,6 +143,7 @@ class BundledMiningService implements MiningService {
     final logFile = await AppPaths.minerLogFile();
     final launcherLogFile = await AppPaths.minerLauncherLogFile();
     await launcherLogFile.parent.create(recursive: true);
+    await _prepareBinary(binary);
 
     final args = <String>[
       '--coin',
@@ -180,6 +182,10 @@ class BundledMiningService implements MiningService {
     }
 
     try {
+      await _appendLauncherLog(
+        launcherLogFile,
+        'launch request: binary="$binary" cwd="${p.dirname(binary)}" args=${args.join(' ')}',
+      );
       final process = await Process.start(
         binary,
         args,
@@ -191,11 +197,26 @@ class BundledMiningService implements MiningService {
       final earlyExit = await _waitForEarlyExit(process);
       if (earlyExit != null) {
         _logger.w('xmrig exited immediately with code $earlyExit');
+        await _appendLauncherLog(
+          launcherLogFile,
+          'xmrig exited immediately with code $earlyExit',
+        );
         return false;
       }
-      return _waitForApi(config);
+      final ready = await _waitForApi(config);
+      if (!ready) {
+        await _appendLauncherLog(
+          launcherLogFile,
+          'xmrig process did not expose HTTP API on 127.0.0.1:${config.apiPort} within timeout',
+        );
+      }
+      return ready;
     } catch (error) {
       _logger.w('Failed to start xmrig: $error');
+      await _appendLauncherLog(
+        launcherLogFile,
+        'Failed to start xmrig: $error',
+      );
       return false;
     }
   }
@@ -224,6 +245,15 @@ class BundledMiningService implements MiningService {
     );
   }
 
+  Future<void> _appendLauncherLog(File file, String line) async {
+    try {
+      await file.writeAsString(
+        '[${DateTime.now().toIso8601String()}] $line\n',
+        mode: FileMode.writeOnlyAppend,
+      );
+    } catch (_) {}
+  }
+
   Future<int?> _waitForEarlyExit(Process process) async {
     const grace = Duration(seconds: 2);
     final result = await Future.any<Object?>([
@@ -243,6 +273,28 @@ class BundledMiningService implements MiningService {
     return false;
   }
 
+  Future<void> _prepareBinary(String binary) async {
+    if (!Platform.isLinux) {
+      return;
+    }
+    try {
+      final file = File(binary);
+      final stat = await file.stat();
+      final mode = stat.mode;
+      final execBits = 0x49; // user/group/other execute
+      if ((mode & execBits) == execBits) {
+        return;
+      }
+      await Process.run(
+        'chmod',
+        ['755', binary],
+        runInShell: true,
+      );
+    } catch (error) {
+      _logger.w('Failed to ensure xmrig executable bit: $error');
+    }
+  }
+
   Future<bool> _waitForExit(int pid, MinerLaunchConfig? config) async {
     for (var i = 0; i < 20; i++) {
       final alive = _isProcessAlive(pid);
@@ -319,6 +371,10 @@ class BundledMiningService implements MiningService {
     if (index < 0 || index >= values.length) {
       return null;
     }
-    return (values[index] as num?)?.toDouble();
+    final value = (values[index] as num?)?.toDouble();
+    if (value == null) {
+      return null;
+    }
+    return math.max(0, value);
   }
 }
diff --git a/lib/ui/screens/mining_screen.dart b/lib/ui/screens/mining_screen.dart
index 3a50d04..4f3d4af 100644
--- a/lib/ui/screens/mining_screen.dart
+++ b/lib/ui/screens/mining_screen.dart
@@ -419,13 +419,18 @@ class _MiningScreenState extends ConsumerState<MiningScreen> {
   Future<void> _startMining() async {
     final l10n = context.l10n;
     final started = await ref.read(miningControllerProvider.notifier).start();
+    final miningState = ref.read(miningControllerProvider);
     if (!mounted) {
       return;
     }
     ScaffoldMessenger.of(context).showSnackBar(
       SnackBar(
         content: Text(
-          started ? l10n.miningMinerStartSuccess : l10n.miningMinerStartFailure,
+          started
+              ? l10n.miningMinerStartSuccess
+              : (miningState.error?.isNotEmpty == true
+                  ? '${l10n.miningMinerStartFailure}: ${miningState.error}'
+                  : l10n.miningMinerStartFailure),
         ),
       ),
     );
@@ -434,13 +439,18 @@ class _MiningScreenState extends ConsumerState<MiningScreen> {
   Future<void> _stopMining() async {
     final l10n = context.l10n;
     final stopped = await ref.read(miningControllerProvider.notifier).stop();
+    final miningState = ref.read(miningControllerProvider);
     if (!mounted) {
       return;
     }
     ScaffoldMessenger.of(context).showSnackBar(
       SnackBar(
         content: Text(
-          stopped ? l10n.miningMinerStopSuccess : l10n.miningMinerStopFailure,
+          stopped
+              ? l10n.miningMinerStopSuccess
+              : (miningState.error?.isNotEmpty == true
+                  ? '${l10n.miningMinerStopFailure}: ${miningState.error}'
+                  : l10n.miningMinerStopFailure),
         ),
       ),
     );
@@ -449,6 +459,7 @@ class _MiningScreenState extends ConsumerState<MiningScreen> {
   Future<void> _restartMining() async {
     final l10n = context.l10n;
     final restarted = await ref.read(miningControllerProvider.notifier).restart();
+    final miningState = ref.read(miningControllerProvider);
     if (!mounted) {
       return;
     }
@@ -457,7 +468,9 @@ class _MiningScreenState extends ConsumerState<MiningScreen> {
         content: Text(
           restarted
               ? l10n.miningMinerRestartSuccess
-              : l10n.miningMinerRestartFailure,
+              : (miningState.error?.isNotEmpty == true
+                  ? '${l10n.miningMinerRestartFailure}: ${miningState.error}'
+                  : l10n.miningMinerRestartFailure),
         ),
       ),
     );