diff --git a/agent/lib/src/runner.dart b/agent/lib/src/runner.dart
index 6a64c7af41..533b7c7328 100644
--- a/agent/lib/src/runner.dart
+++ b/agent/lib/src/runner.dart
@@ -6,6 +6,7 @@ import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
+import 'package:meta/meta.dart';
 import 'package:vm_service_client/vm_service_client.dart';
 
 import 'agent.dart';
@@ -128,12 +129,62 @@ Future<TaskResult> runTask(Agent agent, CocoonTask task) async {
     await stdoutSub.cancel();
     await stderrSub.cancel();
     await sendLog('Task execution finished', flush: true);
+    // Force-quit the task runner process.
     if (!runnerFinished)
       runner.kill(ProcessSignal.SIGKILL);
+    // Force-quit processes launched by Flutter.
+    await _forceQuitFlutterProcesses();
+    // Force-quit dangling local processes (such as adb commands).
     await forceQuitRunningProcesses();
   }
 }
 
+class ProcessListResult {
+  ProcessListResult({@required this.processId, @required this.currentWorkingDirectory});
+
+  /// The "PID" field reported by `ps`.
+  final int processId;
+
+  /// The "cwd" field reported by `lsof`.
+  final String currentWorkingDirectory;
+}
+
+Future<Null> _forceQuitFlutterProcesses() async {
+  List<ProcessListResult> processes = await _listFlutterProcesses();
+  for (ProcessListResult process in processes) {
+    Process.killPid(process.processId, ProcessSignal.SIGKILL);
+  }
+}
+
+Future<List<ProcessListResult>> _listFlutterProcesses() async {
+  List<ProcessListResult> processes = await _listProcesses();
+  return processes
+    .where((ProcessListResult result) => result.currentWorkingDirectory.contains(config.flutterDirectory.absolute.path))
+    .toList();
+}
+
+final _emptySpace = new RegExp(r'\s+');
+
+Future<List<ProcessListResult>> _listProcesses() async {
+  var results = <ProcessListResult>[];
+  String ps = await eval('ps', ['-ef', '-u', Platform.environment['USER']]);
+  for (String psLine in ps.split('\n').skip(1)) {
+    int processId = int.parse(psLine.trim().split(_emptySpace)[1].trim());
+    String lsof = await eval('lsof', ['-p', '$processId'], canFail: true);
+    Iterable<String> cwdGrep = grep('cwd', from: lsof);
+    if (cwdGrep.isEmpty) {
+      // Not all processes report cwd; skip those, unlikely to be interesting.
+      continue;
+    }
+    String cwd = cwdGrep.first.split(' ').last;
+    results.add(new ProcessListResult(
+      processId: processId,
+      currentWorkingDirectory: cwd,
+    ));
+  }
+  return results;
+}
+
 Future<VMIsolate> _connectToRunnerIsolate(int vmServicePort) async {
   String url = 'ws://localhost:$vmServicePort/ws';
   DateTime started = new DateTime.now();