diff --git a/.gitignore b/.gitignore
index 49bd59a..2d55045 100644
--- a/.gitignore
+++ b/.gitignore
@@ -13,3 +13,6 @@ agent-orchestrator.yaml
 !/skills/dart-gherkin-tests
 *.g.dart
 **/*.exe
+/CWS*.yaml
+/CWS*.yml
+dart_test.yaml
diff --git a/lib/src/core/issue_assistant_app.dart b/lib/src/core/issue_assistant_app.dart
index 7116c71..f5756b8 100644
--- a/lib/src/core/issue_assistant_app.dart
+++ b/lib/src/core/issue_assistant_app.dart
@@ -7,6 +7,7 @@ import '../config/app_logger.dart';
 import 'cli_responder.dart';
 import '../config/config.dart';
 import 'database.dart';
+import 'process_launcher.dart';
 import '../issue_tracker/issue_event_source/base.dart';
 import '../issue_tracker/issue_event_source/gitea_gosmee.dart';
 import '../issue_tracker/issue_event_source/gitlab_gosmee.dart';
@@ -46,12 +47,17 @@ class IssueAssistantApp {
     String glabCommand = 'glab',
     String gosmeeCommand = 'gosmee',
     String teaCommand = 'tea',
+    CliResponderRunner? responderRunner,
+    ExternalCommandExecutor? commandExecutor,
   }) async {
     final database = AppDatabase.open(databasePath);
+    final externalCommandExecutor =
+        commandExecutor ?? const DefaultExternalCommandExecutor();
     final issueTrackerClient = IssueTrackerClient(
       ghCommand: ghCommand,
       glabCommand: glabCommand,
       teaCommand: teaCommand,
+      commandExecutor: externalCommandExecutor,
     );
     final pollingIssueEventSource = PollingIssueEventSource(
       database: database,
@@ -71,26 +77,30 @@ class IssueAssistantApp {
           IssueTrackerEventSourceKind.ghGosmee: GitHubGosmeeIssueEventSource(
             issueTrackerClient: issueTrackerClient,
             gosmeeCommand: gosmeeCommand,
+            commandExecutor: externalCommandExecutor,
             logger: _logger,
           ),
           IssueTrackerEventSourceKind.glabGosmee: GitLabGosmeeIssueEventSource(
             issueTrackerClient: issueTrackerClient,
             gosmeeCommand: gosmeeCommand,
+            commandExecutor: externalCommandExecutor,
             logger: _logger,
           ),
           IssueTrackerEventSourceKind.ghWebhookForward:
               GitHubWebhookForwardIssueEventSource(
                 issueTrackerClient: issueTrackerClient,
+                commandExecutor: externalCommandExecutor,
                 logger: _logger,
               ),
           IssueTrackerEventSourceKind.teaGosmee: GiteaGosmeeIssueEventSource(
             issueTrackerClient: issueTrackerClient,
             gosmeeCommand: gosmeeCommand,
+            commandExecutor: externalCommandExecutor,
             logger: _logger,
           ),
         },
       ),
-      responderRunner: CliResponderRunner(),
+      responderRunner: responderRunner ?? CliResponderRunner(),
       workspaceManager: WorkspaceManager(worktreeRoot: config.worktreeDir),
       notifierRegistryFactory: (project) => NotifierRegistry.fromConfigs(
         project.issueAssistant.notifications,
diff --git a/lib/src/core/process_launcher.dart b/lib/src/core/process_launcher.dart
index 097cb1d..b366613 100644
--- a/lib/src/core/process_launcher.dart
+++ b/lib/src/core/process_launcher.dart
@@ -10,13 +10,11 @@ class ResolvedExternalCommand {
   ResolvedExternalCommand({
     required this.executable,
     required this.arguments,
-    required this.usesBashShim,
     required this.runInShell,
   });
 
   final String executable;
   final List<String> arguments;
-  final bool usesBashShim;
   final bool runInShell;
 }
 
@@ -24,6 +22,100 @@ final AppLogger _processLauncherLogger = AppLogger(
   'code_work_spawner.process_launcher',
 );
 
+abstract interface class ExternalCommandExecutor {
+  Future<ProcessResult> run(
+    String executable,
+    List<String> arguments, {
+    String? workingDirectory,
+    Map<String, String>? environment,
+    bool includeParentEnvironment,
+    Duration? timeout,
+  });
+
+  Future<StartedExternalCommand> start(
+    String executable,
+    List<String> arguments, {
+    String? workingDirectory,
+    Map<String, String>? environment,
+    bool includeParentEnvironment,
+    bool runInShell,
+    ProcessStartMode mode,
+  });
+}
+
+abstract interface class StartedExternalCommand {
+  Stream<List<int>> get stdout;
+  Stream<List<int>> get stderr;
+  Future<int> get exitCode;
+  bool kill([ProcessSignal signal = ProcessSignal.sigterm]);
+}
+
+class DefaultExternalCommandExecutor implements ExternalCommandExecutor {
+  const DefaultExternalCommandExecutor();
+
+  @override
+  Future<ProcessResult> run(
+    String executable,
+    List<String> arguments, {
+    String? workingDirectory,
+    Map<String, String>? environment,
+    bool includeParentEnvironment = true,
+    Duration? timeout,
+  }) {
+    return runExternalCommand(
+      executable,
+      arguments,
+      workingDirectory: workingDirectory,
+      environment: environment,
+      includeParentEnvironment: includeParentEnvironment,
+      timeout: timeout,
+    );
+  }
+
+  @override
+  Future<StartedExternalCommand> start(
+    String executable,
+    List<String> arguments, {
+    String? workingDirectory,
+    Map<String, String>? environment,
+    bool includeParentEnvironment = true,
+    bool runInShell = false,
+    ProcessStartMode mode = ProcessStartMode.normal,
+  }) async {
+    return ProcessStartedExternalCommand(
+      await startExternalCommand(
+        executable,
+        arguments,
+        workingDirectory: workingDirectory,
+        environment: environment,
+        includeParentEnvironment: includeParentEnvironment,
+        runInShell: runInShell,
+        mode: mode,
+      ),
+    );
+  }
+}
+
+class ProcessStartedExternalCommand implements StartedExternalCommand {
+  ProcessStartedExternalCommand(this._process);
+
+  final Process _process;
+
+  @override
+  Stream<List<int>> get stdout => _process.stdout;
+
+  @override
+  Stream<List<int>> get stderr => _process.stderr;
+
+  @override
+  Future<int> get exitCode => _process.exitCode;
+
+  @override
+  bool kill([ProcessSignal signal = ProcessSignal.sigterm]) {
+    return _process.kill(signal);
+  }
+}
+
 ResolvedExternalCommand resolveExternalCommandForCurrentPlatform(
   String executable,
   List<String> arguments, {
@@ -35,27 +127,9 @@ ResolvedExternalCommand resolveExternalCommandForCurrentPlatform(
       localExecutablePath ?? _resolveExecutablePathOnPath(executable);
   final effectiveExecutable = resolvedExecutablePath ?? executable;
   final extension = p.extension(effectiveExecutable).toLowerCase();
-  final shouldUseBash = extension.isEmpty || extension == '.sh';
-
-  if (isWindowsPlatform && shouldUseBash && localExecutablePath != null) {
-    final bashScriptPath = _toBashPath(localExecutablePath);
-    _processLauncherLogger.debug(
-      'resolved WSL bash shim executable=$localExecutablePath '
-      'bash_script=$bashScriptPath '
-      'args=${_renderLauncherArguments(arguments)}',
-    );
-    return ResolvedExternalCommand(
-      executable: 'wsl.exe',
-      arguments: ['--exec', 'bash', bashScriptPath, ...arguments],
-      usesBashShim: true,
-      runInShell: false,
-    );
-  }
-
   return ResolvedExternalCommand(
     executable: effectiveExecutable,
     arguments: arguments,
-    usesBashShim: false,
     // Only batch files require shell mediation on Windows. Native executables
     // such as Scoop shims should run directly to avoid hanging shell wrappers.
     runInShell: isWindowsPlatform && _requiresWindowsShell(extension),
@@ -87,18 +161,6 @@ bool _looksLikePathReference(String executable) {
       executable.startsWith('.');
 }
 
-String _toBashPath(String windowsPath) {
-  final normalized = windowsPath.replaceAll('\\', '/');
-  final drivePrefixMatch = RegExp(r'^([A-Za-z]):/(.*)$').firstMatch(normalized);
-  if (drivePrefixMatch == null) {
-    return normalized;
-  }
-
-  final driveLetter = drivePrefixMatch.group(1)!.toLowerCase();
-  final rest = drivePrefixMatch.group(2)!;
-  return '/mnt/$driveLetter/$rest';
-}
-
 Future<ProcessResult> runExternalCommand(
   String executable,
   List<String> arguments, {
@@ -111,67 +173,26 @@ Future<ProcessResult> runExternalCommand(
     executable,
     arguments,
   );
-  final effectiveEnvironment = _effectiveEnvironmentForResolvedCommand(
-    environment: environment,
-    includeParentEnvironment: includeParentEnvironment,
-    usesBashShim: resolved.usesBashShim,
-  );
-  final mode = Platform.isWindows && !resolved.usesBashShim
-      ? 'windows-wrapper'
-      : 'process-run';
+  const mode = 'process-start';
   _processLauncherLogger.debug(
     'launch mode=$mode executable=${resolved.executable} '
     'requested_executable=$executable run_in_shell=${resolved.runInShell} '
-    'uses_bash_shim=${resolved.usesBashShim} '
     'working_directory=${workingDirectory ?? "(inherit)"} '
     'timeout_ms=${timeout?.inMilliseconds ?? 0} '
     'args=${_renderLauncherArguments(resolved.arguments)}',
   );
-  if (Platform.isWindows && !resolved.usesBashShim) {
-    _processLauncherLogger.debug(
-      'process_run in runExternalCommand - windows wrapper',
-    );
-    return _runExternalCommandViaWindowsWrapper(
+  final stopwatch = Stopwatch()..start();
+  try {
+    _processLauncherLogger.debug('process_start in runExternalCommand');
+    final result = await _runExternalCommandWithCapturedOutput(
       executable: resolved.executable,
       arguments: resolved.arguments,
       workingDirectory: workingDirectory,
-      environment: effectiveEnvironment,
+      environment: environment,
       includeParentEnvironment: includeParentEnvironment,
+      runInShell: resolved.runInShell,
       timeout: timeout,
     );
-  }
-  final stopwatch = Stopwatch()..start();
-  try {
-    _processLauncherLogger.debug('process_run in runExternalCommand');
-    final result = timeout == null
-        ? await Process.run(
-            resolved.executable,
-            resolved.arguments,
-            workingDirectory: workingDirectory,
-            environment: effectiveEnvironment,
-            includeParentEnvironment: includeParentEnvironment,
-            runInShell: resolved.runInShell,
-            stdoutEncoding: utf8,
-            stderrEncoding: utf8,
-          )
-        : await Process.run(
-            resolved.executable,
-            resolved.arguments,
-            workingDirectory: workingDirectory,
-            environment: effectiveEnvironment,
-            includeParentEnvironment: includeParentEnvironment,
-            runInShell: resolved.runInShell,
-            stdoutEncoding: utf8,
-            stderrEncoding: utf8,
-          ).timeout(
-            timeout,
-            onTimeout: () {
-              throw TimeoutException(
-                'Command timed out after ${timeout.inMilliseconds}ms.',
-                timeout,
-              );
-            },
-          );
     stopwatch.stop();
     _processLauncherLogger.debug(
       'finished mode=$mode exit_code=${result.exitCode} '
@@ -189,155 +210,47 @@ Future<ProcessResult> runExternalCommand(
   }
 }
 
-Future<ProcessResult> _runExternalCommandViaWindowsWrapper({
+Future<ProcessResult> _runExternalCommandWithCapturedOutput({
   required String executable,
   required List<String> arguments,
   required String? workingDirectory,
   required Map<String, String>? environment,
   required bool includeParentEnvironment,
+  required bool runInShell,
   required Duration? timeout,
 }) async {
-  const timeoutExitCode = 124;
-  final sandbox = await Directory.systemTemp.createTemp(
-    'cws-process-launcher-',
+  final process = await Process.start(
+    executable,
+    arguments,
+    workingDirectory: workingDirectory,
+    environment: environment,
+    includeParentEnvironment: includeParentEnvironment,
+    runInShell: runInShell,
   );
-  final stdoutPath = p.join(sandbox.path, 'stdout.txt');
-  final stderrPath = p.join(sandbox.path, 'stderr.txt');
-  final scriptPath = p.join(sandbox.path, 'run.ps1');
-  final script = File(scriptPath);
-
-  _processLauncherLogger.debug('after fopen');
-
+  final stdoutFuture = process.stdout.transform(utf8.decoder).join();
+  final stderrFuture = process.stderr.transform(utf8.decoder).join();
   try {
-    await script.writeAsString(
-      _buildWindowsWrapperScript(
-        executable: executable,
-        arguments: arguments,
-        workingDirectory: workingDirectory,
-        stdoutPath: stdoutPath,
-        stderrPath: stderrPath,
-        timeout: timeout,
-      ),
-    );
-    final stopwatch = Stopwatch()..start();
-    _processLauncherLogger.debug(
-      'wrapper start executable=$executable '
-      'script=${script.path} stdout_path=$stdoutPath stderr_path=$stderrPath',
-    );
-    final wrapperResult = await Process.run(
-      'powershell.exe',
-      <String>[
-        '-NoProfile',
-        '-NonInteractive',
-        '-ExecutionPolicy',
-        'Bypass',
-        '-File',
-        script.path,
-      ],
-      workingDirectory: workingDirectory,
-      environment: environment,
-      includeParentEnvironment: includeParentEnvironment,
-      stdoutEncoding: utf8,
-      stderrEncoding: utf8,
-    );
-    stopwatch.stop();
-    final stdoutText = await _readWrapperOutput(stdoutPath);
-    final stderrText = await _readWrapperOutput(stderrPath);
-    _processLauncherLogger.debug(
-      'wrapper finished exit_code=${wrapperResult.exitCode} '
-      'duration_ms=${stopwatch.elapsedMilliseconds} '
-      'stdout_len=${stdoutText.length} stderr_len=${stderrText.length} '
-      'wrapper_stdout_len=${wrapperResult.stdout.toString().length} '
-      'wrapper_stderr_len=${wrapperResult.stderr.toString().length}',
-    );
-    if (wrapperResult.exitCode == timeoutExitCode) {
-      throw TimeoutException(
-        'Command timed out after ${timeout!.inMilliseconds}ms.',
-        timeout,
-      );
-    }
-    return ProcessResult(
-      wrapperResult.pid,
-      wrapperResult.exitCode,
-      stdoutText,
-      stderrText.isEmpty ? wrapperResult.stderr : stderrText,
-    );
-  } finally {
-    await sandbox.delete(recursive: true);
+    final exitCode = timeout == null
+        ? await process.exitCode
+        : await process.exitCode.timeout(
+            timeout,
+            onTimeout: () {
+              process.kill(ProcessSignal.sigkill);
+              throw TimeoutException(
+                'Command timed out after ${timeout.inMilliseconds}ms.',
+                timeout,
+              );
+            },
+          );
+    final stdoutText = await stdoutFuture;
+    final stderrText = await stderrFuture;
+    return ProcessResult(process.pid, exitCode, stdoutText, stderrText);
+  } on TimeoutException {
+    process.kill(ProcessSignal.sigkill);
+    rethrow;
   }
 }
 
-String _buildWindowsWrapperScript({
-  required String executable,
-  required List<String> arguments,
-  required String? workingDirectory,
-  required String stdoutPath,
-  required String stderrPath,
-  required Duration? timeout,
-}) {
-  final timeoutMilliseconds = timeout?.inMilliseconds ?? 0;
-  return '''
-\$ErrorActionPreference = 'Stop'
-\$stdoutPath = ${_powerShellSingleQuoted(stdoutPath)}
-\$stderrPath = ${_powerShellSingleQuoted(stderrPath)}
-try {
-  \$commandPath = ${_powerShellSingleQuoted(executable)}
-
-  \$startProcess = @{
-    FilePath = \$commandPath
-    ArgumentList = ${_renderPowerShellArray(arguments)}
-    PassThru = \$true
-    WindowStyle = 'Hidden'
-    RedirectStandardOutput = \$stdoutPath
-    RedirectStandardError = \$stderrPath
-  }
-  if (${workingDirectory == null ? '\$false' : '\$true'}) {
-    \$startProcess.WorkingDirectory = ${_powerShellSingleQuoted(workingDirectory ?? '')}
-  }
-  \$process = Start-Process @startProcess
-
-  \$timedOut = \$false
-  if ($timeoutMilliseconds -gt 0) {
-    if (-not \$process.WaitForExit($timeoutMilliseconds)) {
-      \$timedOut = \$true
-      try {
-        Stop-Process -Id \$process.Id -Force
-      } catch {
-      }
-    }
-  } else {
-    \$process.WaitForExit()
-  }
-
-  if (\$timedOut) {
-    exit 124
-  }
-
-  exit \$process.ExitCode
-} catch {
-  Set-Content -LiteralPath \$stderrPath -Value \$_.ToString() -Encoding utf8
-  exit 127
-}
-''';
-}
-
-Future<String> _readWrapperOutput(String path) async {
-  final file = File(path);
-  if (!await file.exists()) {
-    return '';
-  }
-  return file.readAsString();
-}
-
-String _renderPowerShellArray(List<String> arguments) {
-  final renderedArguments = arguments.map(_powerShellSingleQuoted).join(', ');
-  return '@($renderedArguments)';
-}
-
-String _powerShellSingleQuoted(String value) {
-  return "'${value.replaceAll("'", "''")}'";
-}
-
 String _renderLauncherArguments(List<String> arguments) {
   return arguments.map(_summarizeLauncherArgument).join(' ');
 }
@@ -365,41 +278,13 @@ Future<Process> startExternalCommand(
     executable,
     arguments,
   );
-  final effectiveEnvironment = _effectiveEnvironmentForResolvedCommand(
-    environment: environment,
-    includeParentEnvironment: includeParentEnvironment,
-    usesBashShim: resolved.usesBashShim,
-  );
   return Process.start(
     resolved.executable,
     resolved.arguments,
     workingDirectory: workingDirectory,
-    environment: effectiveEnvironment,
+    environment: environment,
     includeParentEnvironment: includeParentEnvironment,
     runInShell: runInShell || resolved.runInShell,
     mode: mode,
   );
 }
-
-Map<String, String>? _effectiveEnvironmentForResolvedCommand({
-  required Map<String, String>? environment,
-  required bool includeParentEnvironment,
-  required bool usesBashShim,
-}) {
-  if (!usesBashShim || environment == null || environment.isEmpty) {
-    return environment;
-  }
-
-  final effectiveEnvironment = Map<String, String>.from(environment);
-  final existingWslenvFromProcess = includeParentEnvironment
-      ? Platform.environment['WSLENV']
-      : null;
-  final existingWslenv =
-      effectiveEnvironment['WSLENV'] ?? existingWslenvFromProcess;
-  final forwardedKeys = <String>{
-    ...?existingWslenv?.split(':').where((entry) => entry.isNotEmpty),
-    ...effectiveEnvironment.keys.where((key) => key != 'WSLENV'),
-  };
-  effectiveEnvironment['WSLENV'] = forwardedKeys.join(':');
-  return effectiveEnvironment;
-}
diff --git a/lib/src/issue_tracker/client.dart b/lib/src/issue_tracker/client.dart
index 887827e..1816cc9 100644
--- a/lib/src/issue_tracker/client.dart
+++ b/lib/src/issue_tracker/client.dart
@@ -20,8 +20,11 @@ class IssueTrackerClient {
     this.opCommand = 'op',
     Duration? commandTimeout,
     AppLogger? logger,
+    ExternalCommandExecutor? commandExecutor,
   }) : commandTimeout = commandTimeout ?? const Duration(seconds: 15),
-       _logger = logger ?? AppLogger('code_work_spawner.issue_tracker');
+       _logger = logger ?? AppLogger('code_work_spawner.issue_tracker'),
+       _commandExecutor =
+           commandExecutor ?? const DefaultExternalCommandExecutor();
 
   final String ghCommand;
   final String glabCommand;
@@ -29,6 +32,7 @@ class IssueTrackerClient {
   final String opCommand;
   final Duration commandTimeout;
   final AppLogger _logger;
+  final ExternalCommandExecutor _commandExecutor;
   final Map<IssueTrackerProvider, Future<String?>> _authenticatedLoginFutures =
       <IssueTrackerProvider, Future<String?>>{};
   final Map<String, Future<_OpenProjectProjectRef>> _openProjectProjectFutures =
@@ -792,7 +796,7 @@ class IssueTrackerClient {
     );
     late final ProcessResult result;
     try {
-      result = await runExternalCommand(
+      result = await _commandExecutor.run(
         command,
         arguments,
         timeout: commandTimeout,
diff --git a/lib/src/issue_tracker/issue_event_source/gitea_gosmee.dart b/lib/src/issue_tracker/issue_event_source/gitea_gosmee.dart
index 1b71917..fa7425d 100644
--- a/lib/src/issue_tracker/issue_event_source/gitea_gosmee.dart
+++ b/lib/src/issue_tracker/issue_event_source/gitea_gosmee.dart
@@ -15,6 +15,7 @@ class GiteaGosmeeIssueEventSource implements IssueEventSource {
   GiteaGosmeeIssueEventSource({
     required this.issueTrackerClient,
     required this.gosmeeCommand,
+    required this.commandExecutor,
     required AppLogger logger,
   }) : _logger = logger;
 
@@ -22,10 +23,11 @@ class GiteaGosmeeIssueEventSource implements IssueEventSource {
 
   final IssueTrackerClient issueTrackerClient;
   final String gosmeeCommand;
+  final ExternalCommandExecutor commandExecutor;
   final AppLogger _logger;
   final Map<String, _QueuedGiteaIssue> _queuedIssues = {};
   final Set<Future<void>> _activeDispatches = <Future<void>>{};
-  final Map<String, Process> _gosmeeProcesses = {};
+  final Map<String, StartedExternalCommand> _gosmeeProcesses = {};
   final Map<String, int> _webhookIdsByProject = {};
   final Map<String, RepositorySlug> _repoSlugsByProject = {};
 
@@ -109,7 +111,7 @@ class GiteaGosmeeIssueEventSource implements IssueEventSource {
         'gitea/gosmee project=${project.key} start_client '
         'command="$gosmeeCommand client $publicUrl $localUrl"',
       );
-      final process = await startExternalCommand(gosmeeCommand, [
+      final process = await commandExecutor.start(gosmeeCommand, [
         'client',
         publicUrl,
         localUrl,
@@ -286,7 +288,7 @@ class GiteaGosmeeIssueEventSource implements IssueEventSource {
   }
 
   Future<String> _createGosmeeChannelUrl(String localUrl) async {
-    final result = await runExternalCommand(gosmeeCommand, [
+    final result = await commandExecutor.run(gosmeeCommand, [
       '--output',
       'json',
       'client',
diff --git a/lib/src/issue_tracker/issue_event_source/github_gosmee.dart b/lib/src/issue_tracker/issue_event_source/github_gosmee.dart
index 7e1d1ee..26008ad 100644
--- a/lib/src/issue_tracker/issue_event_source/github_gosmee.dart
+++ b/lib/src/issue_tracker/issue_event_source/github_gosmee.dart
@@ -15,6 +15,7 @@ class GitHubGosmeeIssueEventSource implements IssueEventSource {
   GitHubGosmeeIssueEventSource({
     required this.issueTrackerClient,
     required this.gosmeeCommand,
+    required this.commandExecutor,
     required AppLogger logger,
   }) : _logger = logger;
 
@@ -22,10 +23,11 @@ class GitHubGosmeeIssueEventSource implements IssueEventSource {
 
   final IssueTrackerClient issueTrackerClient;
   final String gosmeeCommand;
+  final ExternalCommandExecutor commandExecutor;
   final AppLogger _logger;
   final Map<String, _QueuedGitHubIssue> _queuedIssues = {};
   final Set<Future<void>> _activeDispatches = <Future<void>>{};
-  final Map<String, Process> _gosmeeProcesses = {};
+  final Map<String, StartedExternalCommand> _gosmeeProcesses = {};
   final Map<String, int> _webhookIdsByProject = {};
   final Map<String, RepositorySlug> _repoSlugsByProject = {};
 
@@ -109,7 +111,7 @@ class GitHubGosmeeIssueEventSource implements IssueEventSource {
         'github/gosmee project=${project.key} start_client '
         'command="$gosmeeCommand client $publicUrl $localUrl"',
       );
-      final process = await startExternalCommand(gosmeeCommand, [
+      final process = await commandExecutor.start(gosmeeCommand, [
         'client',
         publicUrl,
         localUrl,
@@ -286,7 +288,7 @@ class GitHubGosmeeIssueEventSource implements IssueEventSource {
   }
 
   Future<String> _createGosmeeChannelUrl(String localUrl) async {
-    final result = await runExternalCommand(gosmeeCommand, [
+    final result = await commandExecutor.run(gosmeeCommand, [
       '--output',
       'json',
       'client',
diff --git a/lib/src/issue_tracker/issue_event_source/github_webhook_forward.dart b/lib/src/issue_tracker/issue_event_source/github_webhook_forward.dart
index fe883c2..5c43115 100644
--- a/lib/src/issue_tracker/issue_event_source/github_webhook_forward.dart
+++ b/lib/src/issue_tracker/issue_event_source/github_webhook_forward.dart
@@ -12,16 +12,18 @@ import 'base.dart';
 class GitHubWebhookForwardIssueEventSource implements IssueEventSource {
   GitHubWebhookForwardIssueEventSource({
     required this.issueTrackerClient,
+    required this.commandExecutor,
     required AppLogger logger,
   }) : _logger = logger;
 
   static const Duration _webhookCoalescingWindow = Duration(milliseconds: 500);
 
   final IssueTrackerClient issueTrackerClient;
+  final ExternalCommandExecutor commandExecutor;
   final AppLogger _logger;
   final Map<String, _QueuedWebhookIssue> _queuedIssues = {};
   final Set<Future<void>> _activeDispatches = <Future<void>>{};
-  final Map<String, Process> _forwardProcesses = {};
+  final Map<String, StartedExternalCommand> _forwardProcesses = {};
 
   HttpServer? _server;
   Timer? _flushTimer;
@@ -82,13 +84,14 @@ class GitHubWebhookForwardIssueEventSource implements IssueEventSource {
         'github/webhook-forward project=${project.key} start_forwarder '
         'command="${issueTrackerClient.ghCommand} webhook forward --events=issues,issue_comment --repo=${project.repo} --url=$url"',
       );
-      final process = await startExternalCommand(issueTrackerClient.ghCommand, [
-        'webhook',
-        'forward',
-        '--events=issues,issue_comment',
-        '--repo=${project.repo}',
-        '--url=$url',
-      ]);
+      final process = await commandExecutor
+          .start(issueTrackerClient.ghCommand, [
+            'webhook',
+            'forward',
+            '--events=issues,issue_comment',
+            '--repo=${project.repo}',
+            '--url=$url',
+          ]);
       _forwardProcesses[project.key] = process;
       _pipeProcessLogs(
         project: project,
diff --git a/lib/src/issue_tracker/issue_event_source/gitlab_gosmee.dart b/lib/src/issue_tracker/issue_event_source/gitlab_gosmee.dart
index 7561b60..bea89d9 100644
--- a/lib/src/issue_tracker/issue_event_source/gitlab_gosmee.dart
+++ b/lib/src/issue_tracker/issue_event_source/gitlab_gosmee.dart
@@ -13,6 +13,7 @@ class GitLabGosmeeIssueEventSource implements IssueEventSource {
   GitLabGosmeeIssueEventSource({
     required this.issueTrackerClient,
     required this.gosmeeCommand,
+    required this.commandExecutor,
     required AppLogger logger,
   }) : _logger = logger;
 
@@ -20,10 +21,11 @@ class GitLabGosmeeIssueEventSource implements IssueEventSource {
 
   final IssueTrackerClient issueTrackerClient;
   final String gosmeeCommand;
+  final ExternalCommandExecutor commandExecutor;
   final AppLogger _logger;
   final Map<String, _QueuedGitLabIssue> _queuedIssues = {};
   final Set<Future<void>> _activeDispatches = <Future<void>>{};
-  final Map<String, Process> _gosmeeProcesses = {};
+  final Map<String, StartedExternalCommand> _gosmeeProcesses = {};
   final Map<String, int> _webhookIdsByProject = {};
   final Map<String, String> _trackerProjectsByProject = {};
 
@@ -107,7 +109,7 @@ class GitLabGosmeeIssueEventSource implements IssueEventSource {
         'gitlab/gosmee project=${project.key} start_client '
         'command="$gosmeeCommand client $publicUrl $localUrl"',
       );
-      final process = await startExternalCommand(gosmeeCommand, [
+      final process = await commandExecutor.start(gosmeeCommand, [
         'client',
         publicUrl,
         localUrl,
@@ -324,7 +326,7 @@ class GitLabGosmeeIssueEventSource implements IssueEventSource {
   }
 
   Future<String> _createGosmeeChannelUrl(String localUrl) async {
-    final result = await runExternalCommand(gosmeeCommand, [
+    final result = await commandExecutor.run(gosmeeCommand, [
       '--output',
       'json',
       'client',
diff --git a/pubspec.yaml b/pubspec.yaml
index f27152d..59f8e48 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -30,6 +30,7 @@ dev_dependencies:
   drift_dev: ^2.28.1
   json_serializable: ">=6.11.1 <6.12.0"
   lints: ^6.0.0
+  mocktail: ^1.0.5
   test: ^1.25.6
 
 platforms:
diff --git a/test/core/concurrency_test.dart b/test/core/concurrency_test.dart
index 71ad180..faa42b0 100644
--- a/test/core/concurrency_test.dart
+++ b/test/core/concurrency_test.dart
@@ -146,6 +146,8 @@ projects:
         config: await AppConfig.load(configFile.path),
         databasePath: p.join(sandbox.path, 'state.sqlite3'),
         ghCommand: ghScript.path,
+        responderRunner: fakeResponderRunner(),
+        commandExecutor: fakeExternalCommandExecutor(),
       );
 
       // When the app processes one polling cycle.
@@ -285,6 +287,8 @@ projects:
         config: await AppConfig.load(configFile.path),
         databasePath: p.join(sandbox.path, 'state.sqlite3'),
         ghCommand: ghScript.path,
+        responderRunner: fakeResponderRunner(),
+        commandExecutor: fakeExternalCommandExecutor(),
       );
 
       // When the app processes one polling cycle.
@@ -367,6 +371,8 @@ projects:
         config: await AppConfig.load(configFile.path),
         databasePath: p.join(sandbox.path, 'state.sqlite3'),
         ghCommand: ghScript.path,
+        responderRunner: fakeResponderRunner(),
+        commandExecutor: fakeExternalCommandExecutor(),
       );
 
       // When the app processes one polling cycle.
diff --git a/test/core/core_test.dart b/test/core/core_test.dart
index ea455a4..7c9efd8 100644
--- a/test/core/core_test.dart
+++ b/test/core/core_test.dart
@@ -102,6 +102,8 @@ projects:
         config: await AppConfig.load(configFile.path),
         databasePath: p.join(sandbox.path, 'state.sqlite3'),
         ghCommand: ghScript.path,
+        responderRunner: fakeResponderRunner(),
+        commandExecutor: fakeExternalCommandExecutor(),
       );
 
       // When the app processes one polling cycle.
@@ -210,6 +212,8 @@ projects:
           config: await AppConfig.load(configFile.path),
           databasePath: p.join(sandbox.path, 'state.sqlite3'),
           ghCommand: ghScript.path,
+          responderRunner: fakeResponderRunner(),
+          commandExecutor: fakeExternalCommandExecutor(),
         );
 
         // When the app processes one polling cycle.
@@ -308,6 +312,8 @@ projects:
         config: await AppConfig.load(configFile.path),
         databasePath: p.join(sandbox.path, 'state.sqlite3'),
         ghCommand: ghScript.path,
+        responderRunner: fakeResponderRunner(),
+        commandExecutor: fakeExternalCommandExecutor(),
       );
 
       // When the app processes one polling cycle.
@@ -437,6 +443,8 @@ projects:
           config: await AppConfig.load(configFile.path),
           databasePath: p.join(sandbox.path, 'state.sqlite3'),
           ghCommand: ghScript.path,
+          responderRunner: fakeResponderRunner(),
+          commandExecutor: fakeExternalCommandExecutor(),
         );
 
         // When the app processes one polling cycle.
@@ -537,6 +545,8 @@ projects:
         config: await AppConfig.load(configFile.path),
         databasePath: p.join(sandbox.path, 'state.sqlite3'),
         ghCommand: ghScript.path,
+        responderRunner: fakeResponderRunner(),
+        commandExecutor: fakeExternalCommandExecutor(),
       );
       final logMessages = <String>[];
       void captureLog(AppLogRecord record) {
diff --git a/test/core/multi_project_test.dart b/test/core/multi_project_test.dart
index aac6b81..9417d68 100644
--- a/test/core/multi_project_test.dart
+++ b/test/core/multi_project_test.dart
@@ -173,6 +173,8 @@ projects:
           config: await AppConfig.load(configFile.path),
           databasePath: p.join(sandbox.path, 'state.sqlite3'),
           ghCommand: ghScript.path,
+          responderRunner: fakeResponderRunner(),
+          commandExecutor: fakeExternalCommandExecutor(),
         );
 
         // When the app processes one polling cycle.
@@ -318,6 +320,8 @@ CWS_GITEA_TOKEN=test-token
       final app = await IssueAssistantApp.open(
         config: await AppConfig.load(configFile.path),
         databasePath: p.join(sandbox.path, 'state.sqlite3'),
+        responderRunner: fakeResponderRunner(),
+        commandExecutor: fakeExternalCommandExecutor(),
       );
 
       // When the app processes one polling cycle.
@@ -419,6 +423,8 @@ OP_CLI_TOKEN=test-token
         final app = await IssueAssistantApp.open(
           config: await AppConfig.load(configFile.path),
           databasePath: p.join(sandbox.path, 'state.sqlite3'),
+          responderRunner: fakeResponderRunner(),
+          commandExecutor: fakeExternalCommandExecutor(),
         );
 
         // When the app processes one polling cycle.
diff --git a/test/core/process_launcher_test.dart b/test/core/process_launcher_test.dart
index a676d9d..6d5154f 100644
--- a/test/core/process_launcher_test.dart
+++ b/test/core/process_launcher_test.dart
@@ -36,7 +36,6 @@ void main() {
 
       // And it does not force the command to run in a shell.
       expect(resolved.runInShell, isFalse);
-      expect(resolved.usesBashShim, isFalse);
     });
 
     /// ```gherkin
@@ -62,47 +61,40 @@ void main() {
 
       // And it marks the command to run in a shell.
       expect(resolved.runInShell, isTrue);
-      expect(resolved.usesBashShim, isFalse);
     });
 
     /// ```gherkin
-    /// Scenario: Wrap local extensionless scripts through WSL bash on Windows
-    ///   Given a local extensionless script file on Windows
+    /// Scenario: Leave local Bash scripts unresolved on Windows
+    ///   Given a local Bash script file on Windows
     ///   When the process launcher resolves the command
-    ///   Then it swaps the executable to wsl.exe
-    ///   And it forwards the script path as a bash path
+    ///   Then it leaves the script path unchanged
+    ///   And it does not add a WSL wrapper
     /// ```
-    test(
-      'Wrap local extensionless scripts through WSL bash on Windows',
-      () async {
-        // Given a local extensionless script file on Windows.
-        final sandbox = await Directory.systemTemp.createTemp(
-          'cws-process-launcher-',
+    test('Leave local Bash scripts unresolved on Windows', () async {
+      // Given a local Bash script file on Windows.
+      final sandbox = await Directory.systemTemp.createTemp(
+        'cws-process-launcher-',
+      );
+      final script = File(p.join(sandbox.path, 'fake-tea.sh'));
+      await script.writeAsString('#!/usr/bin/env bash\nprintf \'[]\\n\'\n');
+
+      try {
+        // When the process launcher resolves the command.
+        final resolved = resolveExternalCommandForCurrentPlatform(
+          script.path,
+          const <String>['api'],
+          isWindows: true,
         );
-        final script = File(p.join(sandbox.path, 'fake-tea'));
-        await script.writeAsString('#!/usr/bin/env bash\nprintf \'[]\\n\'\n');
 
-        try {
-          // When the process launcher resolves the command.
-          final resolved = resolveExternalCommandForCurrentPlatform(
-            script.path,
-            const <String>['api'],
-            isWindows: true,
-          );
+        // Then it leaves the script path unchanged.
+        expect(resolved.executable, script.path);
 
-          // Then it swaps the executable to wsl.exe.
-          expect(resolved.executable, 'wsl.exe');
-          expect(resolved.usesBashShim, isTrue);
-
-          // And it forwards the script path as a bash path.
-          expect(resolved.runInShell, isFalse);
-          expect(resolved.arguments.first, '--exec');
-          expect(resolved.arguments[1], 'bash');
-          expect(resolved.arguments[2], startsWith('/mnt/'));
-        } finally {
-          await sandbox.delete(recursive: true);
-        }
-      },
-    );
+        // And it does not add a WSL wrapper.
+        expect(resolved.runInShell, isFalse);
+        expect(resolved.arguments, const <String>['api']);
+      } finally {
+        await sandbox.delete(recursive: true);
+      }
+    });
   });
 }
diff --git a/test/core/retry_test.dart b/test/core/retry_test.dart
index 76348c8..5223a0a 100644
--- a/test/core/retry_test.dart
+++ b/test/core/retry_test.dart
@@ -84,6 +84,8 @@ projects:
         config: await AppConfig.load(configFile.path),
         databasePath: p.join(sandbox.path, 'state.sqlite3'),
         ghCommand: ghScript.path,
+        responderRunner: fakeResponderRunner(),
+        commandExecutor: fakeExternalCommandExecutor(),
       );
       final logMessages = <String>[];
       void captureLog(AppLogRecord record) {
diff --git a/test/issue_event_source/github_gosmee_test.dart b/test/issue_event_source/github_gosmee_test.dart
index ead73fc..2f10267 100644
--- a/test/issue_event_source/github_gosmee_test.dart
+++ b/test/issue_event_source/github_gosmee_test.dart
@@ -120,6 +120,8 @@ projects:
         databasePath: p.join(sandbox.path, 'state.sqlite3'),
         ghCommand: ghScript.path,
         gosmeeCommand: gosmeeScript.path,
+        responderRunner: fakeResponderRunner(),
+        commandExecutor: fakeExternalCommandExecutor(),
       );
 
       // When the long-running app starts and receives the forwarded webhook.
diff --git a/test/issue_event_source/gitlab_gosmee_test.dart b/test/issue_event_source/gitlab_gosmee_test.dart
index 9aac4dc..133e601 100644
--- a/test/issue_event_source/gitlab_gosmee_test.dart
+++ b/test/issue_event_source/gitlab_gosmee_test.dart
@@ -134,6 +134,8 @@ projects:
         databasePath: p.join(sandbox.path, 'state.sqlite3'),
         glabCommand: glabScript.path,
         gosmeeCommand: gosmeeScript.path,
+        responderRunner: fakeResponderRunner(),
+        commandExecutor: fakeExternalCommandExecutor(),
       );
 
       // When the long-running app starts and receives the forwarded webhook.
diff --git a/test/issue_event_source/gosmee_test.dart b/test/issue_event_source/gosmee_test.dart
index a6dcaeb..dd5aafd 100644
--- a/test/issue_event_source/gosmee_test.dart
+++ b/test/issue_event_source/gosmee_test.dart
@@ -129,6 +129,8 @@ CWS_GITEA_TOKEN=test-token
         config: await AppConfig.load(configFile.path),
         databasePath: p.join(sandbox.path, 'state.sqlite3'),
         gosmeeCommand: gosmeeScript.path,
+        responderRunner: fakeResponderRunner(),
+        commandExecutor: fakeExternalCommandExecutor(),
       );
 
       // When the long-running app starts and receives the forwarded webhook.
@@ -185,25 +187,11 @@ CWS_GITEA_TOKEN=test-token
       // And a gosmee script that starts forwarding without delivering an event.
       final gosmeeScript = File(p.join(sandbox.path, 'gosmee'));
       final gosmeeLog = File(p.join(sandbox.path, 'gosmee-log.jsonl'));
-      await gosmeeScript.writeAsString('''#!/usr/bin/env bash
-set -euo pipefail
-    printf '%s\n' "\$*" >> "${bashScriptPath(gosmeeLog.path)}"
-
-if [[ "\$1" == "--output" && "\$2" == "json" && "\$3" == "client" && "\$4" == "--new-url" ]]; then
-  printf '%s\n' 'https://gosmee.example.test/reconcile'
-  exit 0
-fi
-
-if [[ "\$1" == "client" ]]; then
-  while true; do
-    sleep 60
-  done
-fi
-
-echo "unexpected gosmee args: \$*" >&2
-exit 1
-''');
-      await makeScriptExecutable(gosmeeScript);
+      registerFakeGosmeeCommand(
+        command: gosmeeScript.path,
+        publicUrl: 'https://gosmee.example.test/reconcile',
+        gosmeeLog: gosmeeLog,
+      );
 
       final issue = {
         'index': 18,
@@ -290,6 +278,8 @@ CWS_GITEA_TOKEN=test-token
         config: await AppConfig.load(configFile.path),
         databasePath: p.join(sandbox.path, 'state.sqlite3'),
         gosmeeCommand: gosmeeScript.path,
+        responderRunner: fakeResponderRunner(),
+        commandExecutor: fakeExternalCommandExecutor(),
       );
 
       // When the long-running app starts and enough time passes for reconciliation polling.
diff --git a/test/issue_event_source/webhook_forward_test.dart b/test/issue_event_source/webhook_forward_test.dart
index 42097f3..f1726ff 100644
--- a/test/issue_event_source/webhook_forward_test.dart
+++ b/test/issue_event_source/webhook_forward_test.dart
@@ -100,6 +100,8 @@ projects:
         config: await AppConfig.load(configFile.path),
         databasePath: p.join(sandbox.path, 'state.sqlite3'),
         ghCommand: ghScript.path,
+        responderRunner: fakeResponderRunner(),
+        commandExecutor: fakeExternalCommandExecutor(),
       );
 
       // When the long-running app starts and receives the forwarded webhook.
@@ -152,34 +154,36 @@ projects:
 
       // And a gh script that writes a webhook creation failure to stderr while forwarding.
       final ghScript = File(p.join(sandbox.path, 'gh'));
-      await ghScript.writeAsString('''#!/usr/bin/env bash
-set -euo pipefail
-
-if [[ "\$1" == "webhook" && "\$2" == "forward" ]]; then
-  echo "Error: error creating webhook: HTTP 422: Validation Failed (https://api.github.com/repos/existedinnettw/code_work_spawner/hooks)" >&2
-  while true; do
-    sleep 60
-  done
-fi
-
-if [[ "\$1" == "api" && "\$2" == "user" ]]; then
-  cat <<'JSON'
-${jsonEncode({'login': 'octocat'})}
-JSON
-  exit 0
-fi
-
-if [[ "\$1" == "api" && "\$4" == "search/issues" ]]; then
-  cat <<'JSON'
-{"total_count":0,"incomplete_results":false,"items":[]}
-JSON
-  exit 0
-fi
-
-echo "unexpected gh args: \$*" >&2
-exit 1
-''');
-      await makeScriptExecutable(ghScript);
+      fakeCommandHandlers[ghScript.path] = (arguments, {timeout}) async {
+        if (arguments.length >= 2 &&
+            arguments[0] == 'api' &&
+            arguments[1] == 'user') {
+          return ProcessResult(0, 0, '{"login":"octocat"}', '');
+        }
+        if (arguments.length >= 4 &&
+            arguments[0] == 'api' &&
+            arguments[3] == 'search/issues') {
+          return ProcessResult(
+            0,
+            0,
+            '{"total_count":0,"incomplete_results":false,"items":[]}',
+            '',
+          );
+        }
+        return ProcessResult(
+          0,
+          1,
+          '',
+          'unexpected gh args: ${arguments.join(' ')}\n',
+        );
+      };
+      fakeStartedCommandHandlers[ghScript.path] = (arguments) async {
+        final process = FakeStartedExternalCommand()
+          ..addStderr(
+            'Error: error creating webhook: HTTP 422: Validation Failed (https://api.github.com/repos/existedinnettw/code_work_spawner/hooks)\n',
+          );
+        return process;
+      };
 
       // And an orchestrator-style config that uses gh/webhook-forward.
       final configFile = File(p.join(sandbox.path, 'agent-orchestrator.yaml'));
@@ -200,6 +204,8 @@ projects:
         config: await AppConfig.load(configFile.path),
         databasePath: p.join(sandbox.path, 'state.sqlite3'),
         ghCommand: ghScript.path,
+        responderRunner: fakeResponderRunner(),
+        commandExecutor: fakeExternalCommandExecutor(),
       );
       final records = <AppLogRecord>[];
       void captureLog(AppLogRecord record) {
@@ -284,69 +290,85 @@ projects:
           'user': {'login': 'reporter'},
         },
       ];
-      await ghScript.writeAsString('''#!/usr/bin/env bash
-set -euo pipefail
-    printf '%s\n' "\$*" >> "${bashScriptPath(ghLog.path)}"
-
-if [[ "\$1" == "api" && "\$2" == "user" ]]; then
-  cat <<'JSON'
-${jsonEncode({'login': 'octocat'})}
-JSON
-  exit 0
-fi
-
-if [[ "\$1" == "api" && "\$4" == "search/issues" ]]; then
-  count=0
-  if [[ -f "${bashScriptPath(searchCountFile.path)}" ]]; then
-    count="\$(cat "${bashScriptPath(searchCountFile.path)}")"
-  fi
-  count=\$((count + 1))
-  printf '%s' "\$count" > "${bashScriptPath(searchCountFile.path)}"
-  if [[ "\$count" -eq 1 ]]; then
-    cat <<'JSON'
-{"total_count":0,"incomplete_results":false,"items":[]}
-JSON
-  else
-    cat <<'JSON'
-${jsonEncode({
-        'total_count': 1,
-        'incomplete_results': false,
-        'items': [searchItem],
-      })}
-JSON
-  fi
-  exit 0
-fi
-
-if [[ "\$1" == "api" && "\$4" == "repos/owner/sample/issues/18/comments?per_page=100" ]]; then
-  cat <<'JSON'
-${jsonEncode(comments)}
-JSON
-  exit 0
-fi
-
-if [[ "\$1" == "api" && "\$4" == "repos/owner/sample/issues/18/comments" ]]; then
-  for arg in "\$@"; do
-    if [[ "\$arg" == body=* ]]; then
-      printf '%s' "\${arg#body=}" > "${bashScriptPath(postedBody.path)}"
-    fi
-  done
-  cat <<'JSON'
-${jsonEncode({'id': 703, 'html_url': 'https://example.test/comment/703', 'body': 'posted'})}
-JSON
-  exit 0
-fi
-
-if [[ "\$1" == "webhook" && "\$2" == "forward" ]]; then
-  while true; do
-    sleep 60
-  done
-fi
-
-echo "unexpected gh args: \$*" >&2
-exit 1
-''');
-      await makeScriptExecutable(ghScript);
+      fakeCommandHandlers[ghScript.path] = (arguments, {timeout}) async {
+        await ghLog.writeAsString(
+          '${arguments.join(' ')}\n',
+          mode: FileMode.append,
+        );
+        if (arguments.length >= 2 &&
+            arguments[0] == 'api' &&
+            arguments[1] == 'user') {
+          return ProcessResult(0, 0, '{"login":"octocat"}', '');
+        }
+        final path = arguments.length > 3 ? arguments[3] : '';
+        if (arguments.length >= 4 &&
+            arguments[0] == 'api' &&
+            path == 'search/issues') {
+          var count = 0;
+          if (await searchCountFile.exists()) {
+            count = int.parse(await searchCountFile.readAsString());
+          }
+          count += 1;
+          await searchCountFile.writeAsString(count.toString());
+          return ProcessResult(
+            0,
+            0,
+            jsonEncode(
+              count == 1
+                  ? {
+                      'total_count': 0,
+                      'incomplete_results': false,
+                      'items': <Object?>[],
+                    }
+                  : {
+                      'total_count': 1,
+                      'incomplete_results': false,
+                      'items': [searchItem],
+                    },
+            ),
+            '',
+          );
+        }
+        if (arguments.length >= 4 &&
+            arguments[0] == 'api' &&
+            path == 'repos/owner/sample/issues/18/comments?per_page=100') {
+          return ProcessResult(0, 0, jsonEncode(comments), '');
+        }
+        if (arguments.length >= 4 &&
+            arguments[0] == 'api' &&
+            path == 'repos/owner/sample/issues/18/comments') {
+          final body = arguments
+              .where((argument) => argument.startsWith('body='))
+              .map((argument) => argument.substring('body='.length))
+              .firstOrNull;
+          if (body != null) {
+            await postedBody.writeAsString(body);
+          }
+          return ProcessResult(
+            0,
+            0,
+            jsonEncode({
+              'id': 703,
+              'html_url': 'https://example.test/comment/703',
+              'body': 'posted',
+            }),
+            '',
+          );
+        }
+        return ProcessResult(
+          0,
+          1,
+          '',
+          'unexpected gh args: ${arguments.join(' ')}\n',
+        );
+      };
+      fakeStartedCommandHandlers[ghScript.path] = (arguments) async {
+        await ghLog.writeAsString(
+          '${arguments.join(' ')}\n',
+          mode: FileMode.append,
+        );
+        return FakeStartedExternalCommand();
+      };
 
       // And a responder that emits a planning reply.
       final responderScript = File(p.join(sandbox.path, 'responder.sh'));
@@ -383,6 +405,8 @@ projects:
         config: await AppConfig.load(configFile.path),
         databasePath: p.join(sandbox.path, 'state.sqlite3'),
         ghCommand: ghScript.path,
+        responderRunner: fakeResponderRunner(),
+        commandExecutor: fakeExternalCommandExecutor(),
       );
 
       // When the long-running app starts and enough time passes for reconciliation polling.
diff --git a/test/issue_tracker_client_test.dart b/test/issue_tracker_client_test.dart
index 90ed317..aaa5524 100644
--- a/test/issue_tracker_client_test.dart
+++ b/test/issue_tracker_client_test.dart
@@ -146,7 +146,10 @@ void main() {
         postedBodyFile: postedBodyFile,
         viewerLogin: 'glab-user',
       );
-      final client = IssueTrackerClient(glabCommand: glabScript.path);
+      final client = IssueTrackerClient(
+        glabCommand: glabScript.path,
+        commandExecutor: fakeExternalCommandExecutor(),
+      );
 
       // When the tracker client fetches updates, loads the thread, resolves the login, and posts a comment.
       final issues = await client.fetchUpdatedIssuesForRepos(
diff --git a/test/notifier/notifications_test.dart b/test/notifier/notifications_test.dart
index 0996145..c72dc55 100644
--- a/test/notifier/notifications_test.dart
+++ b/test/notifier/notifications_test.dart
@@ -120,6 +120,8 @@ projects:
         config: await AppConfig.load(configFile.path),
         databasePath: p.join(sandbox.path, 'state.sqlite3'),
         ghCommand: ghScript.path,
+        responderRunner: fakeResponderRunner(),
+        commandExecutor: fakeExternalCommandExecutor(),
       );
 
       // When the app processes one polling cycle.
@@ -252,6 +254,8 @@ projects:
           config: await AppConfig.load(configFile.path),
           databasePath: p.join(sandbox.path, 'state.sqlite3'),
           ghCommand: ghScript.path,
+          responderRunner: fakeResponderRunner(),
+          commandExecutor: fakeExternalCommandExecutor(),
         );
 
         // When the app processes one polling cycle.
diff --git a/test/support/fake_gh.dart b/test/support/fake_gh.dart
index ff8e8e0..38ab70a 100644
--- a/test/support/fake_gh.dart
+++ b/test/support/fake_gh.dart
@@ -1,3 +1,4 @@
+import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
@@ -18,15 +19,15 @@ Future<void> writeFakeGhScript({
   String? viewerLogin,
   bool failViewerLookup = false,
 }) async {
-  final normalizedIssueListResponsesByRepo =
+  final issueLists =
       issueListResponsesByRepo ??
       <String, List<Map<String, Object?>>>{'owner/sample': issueListResponse};
-  final normalizedCommentResponsesByRepo =
+  final comments =
       commentResponsesByRepo ??
       <String, Map<int, List<Map<String, Object?>>>>{
         'owner/sample': commentResponses,
       };
-  final normalizedPostCommentIssueNumbersByRepo =
+  final postIssueNumbers =
       postCommentIssueNumbersByRepo ??
       <String, Set<int>>{
         'owner/sample': {
@@ -35,7 +36,7 @@ Future<void> writeFakeGhScript({
         },
       };
   final searchItems =
-      normalizedIssueListResponsesByRepo.entries
+      issueLists.entries
           .expand(
             (entry) => entry.value.map(
               (issue) => <String, Object?>{
@@ -53,168 +54,28 @@ Future<void> writeFakeGhScript({
   final openSearchItems = searchItems
       .where((item) => item['state'] == 'open')
       .toList(growable: false);
-  final allSearchResponse = jsonEncode({
-    'total_count': searchItems.length,
-    'incomplete_results': false,
-    'items': searchItems,
-  });
-  final openSearchResponse = jsonEncode({
-    'total_count': openSearchItems.length,
-    'incomplete_results': false,
-    'items': openSearchItems,
-  });
 
-  final buffer = StringBuffer()
-    ..writeln('#!/usr/bin/env bash')
-    ..writeln('set -euo pipefail');
-
-  if (ghLog != null) {
-    buffer.writeln(
-      r'''printf '%s\n' "$*" >> '''
-      '"${bashScriptPath(ghLog.path)}"',
-    );
-  }
-
-  buffer.writeln(r'''if [[ "$1" == "api" && "$2" == "user" ]]; then''');
-  if (failViewerLookup) {
-    buffer
-      ..writeln(r'''  echo "viewer lookup failed" >&2''')
-      ..writeln('  exit 1')
-      ..writeln('fi');
-  } else {
-    buffer
-      ..writeln("  cat <<'JSON'")
-      ..writeln(jsonEncode({'login': viewerLogin ?? 'test-user'}))
-      ..writeln('JSON')
-      ..writeln('  exit 0')
-      ..writeln('fi');
-  }
-
-  buffer
-    ..writeln(r'''if [[ "$1" == "api" && "$4" == "search/issues" ]]; then''')
-    ..writeln(r'''  query=""''')
-    ..writeln(r'''  for arg in "$@"; do''')
-    ..writeln(r'''    if [[ "$arg" == q=* ]]; then''')
-    ..writeln(r'''      query="${arg#q=}"''')
-    ..writeln(r'''    fi''')
-    ..writeln(r'''  done''')
-    ..writeln(r'''  if [[ "$query" == *"state:open"* ]]; then''')
-    ..writeln("  cat <<'JSON'")
-    ..writeln(openSearchResponse)
-    ..writeln('JSON')
-    ..writeln(r'''  else''')
-    ..writeln("  cat <<'JSON'")
-    ..writeln(allSearchResponse)
-    ..writeln('JSON')
-    ..writeln(r'''  fi''')
-    ..writeln('  exit 0')
-    ..writeln('fi');
-
-  for (final entry in normalizedIssueListResponsesByRepo.entries) {
-    final repo = entry.key;
-    buffer
-      ..writeln(
-        'if [[ "\$1" == "api" && "\$4" == repos/$repo/issues\\?* ]]; then',
-      )
-      ..writeln("  cat <<'JSON'")
-      ..writeln(jsonEncode(entry.value))
-      ..writeln('JSON')
-      ..writeln('  exit 0')
-      ..writeln('fi');
-  }
-
-  for (final repoEntry in normalizedCommentResponsesByRepo.entries) {
-    final repo = repoEntry.key;
-    for (final entry in repoEntry.value.entries) {
-      buffer
-        ..writeln(
-          'if [[ "\$1" == "api" && "\$4" == '
-          '"repos/$repo/issues/${entry.key}/comments?per_page=100" ]]; then',
-        )
-        ..writeln("  cat <<'JSON'")
-        ..writeln(jsonEncode(entry.value))
-        ..writeln('JSON')
-        ..writeln('  exit 0')
-        ..writeln('fi');
-    }
-  }
-
-  for (final repoEntry in normalizedPostCommentIssueNumbersByRepo.entries) {
-    final repo = repoEntry.key;
-    for (final issueNumber in repoEntry.value) {
-      buffer
-        ..writeln(
-          'if [[ "\$1" == "api" && "\$4" == '
-          '"repos/$repo/issues/$issueNumber/comments" ]]; then',
-        )
-        ..writeln(r'''  for arg in "$@"; do''')
-        ..writeln(r'''    :''');
-      if (postedBodyFile != null) {
-        buffer
-          ..writeln(r'''    if [[ "$arg" == body=* ]]; then''')
-          ..writeln(
-            r'''      printf '%s' "${arg#body=}" > '''
-            '"${bashScriptPath(postedBodyFile.path)}"',
-          )
-          ..writeln(r'''    fi''');
-      }
-      buffer
-        ..writeln(r'''  done''')
-        ..writeln("  cat <<'JSON'")
-        ..writeln(
-          jsonEncode({
-            'id': 700,
-            'html_url': 'https://example.test/comment/700',
-            'body': 'posted',
-          }),
-        )
-        ..writeln('JSON')
-        ..writeln('  exit 0')
-        ..writeln('fi');
-    }
-  }
-
-  for (final repoEntry in normalizedCommentResponsesByRepo.entries) {
-    final repo = repoEntry.key;
-    for (final issueEntry in repoEntry.value.entries) {
-      for (final comment in issueEntry.value) {
-        final commentId = comment['id'];
-        if (commentId is! int) {
-          continue;
-        }
-        buffer
-          ..writeln(
-            'if [[ "\$1" == "api" && "\$4" == '
-            '"repos/$repo/issues/comments/$commentId/reactions" ]]; then',
-          )
-          ..writeln(r'''  for arg in "$@"; do''')
-          ..writeln(r'''    :''');
-        if (reactionBodyFile != null) {
-          buffer
-            ..writeln(r'''    if [[ "$arg" == content=* ]]; then''')
-            ..writeln(
-              r'''      printf '%s' "${arg#content=}" > '''
-              '"${bashScriptPath(reactionBodyFile.path)}"',
-            )
-            ..writeln(r'''    fi''');
-        }
-        buffer
-          ..writeln(r'''  done''')
-          ..writeln("  cat <<'JSON'")
-          ..writeln(jsonEncode({'id': 990, 'content': 'eyes'}))
-          ..writeln('JSON')
-          ..writeln('  exit 0')
-          ..writeln('fi');
-      }
-    }
-  }
-
-  buffer
-    ..writeln(r'''echo "unexpected gh args: $*" >&2''')
-    ..writeln('exit 1');
-
-  await ghScript.writeAsString(buffer.toString());
-  await makeScriptExecutable(ghScript);
+  _registerFakeGhCommand(
+    command: ghScript.path,
+    ghLog: ghLog,
+    failViewerLookup: failViewerLookup,
+    viewerLogin: viewerLogin,
+    searchResponse: {
+      'total_count': searchItems.length,
+      'incomplete_results': false,
+      'items': searchItems,
+    },
+    openSearchResponse: {
+      'total_count': openSearchItems.length,
+      'incomplete_results': false,
+      'items': openSearchItems,
+    },
+    issueLists: issueLists,
+    comments: comments,
+    postIssueNumbers: postIssueNumbers,
+    postedBodyFile: postedBodyFile,
+    reactionBodyFile: reactionBodyFile,
+  );
 }
 
 Future<void> writeFlakySearchGhScript({
@@ -232,68 +93,20 @@ Future<void> writeFlakySearchGhScript({
         },
       )
       .toList(growable: false);
-  final searchResponse = jsonEncode({
-    'total_count': searchItems.length,
-    'incomplete_results': false,
-    'items': searchItems,
-  });
 
-  final buffer = StringBuffer()
-    ..writeln('#!/usr/bin/env bash')
-    ..writeln('set -euo pipefail');
-
-  if (ghLog != null) {
-    buffer.writeln(
-      r'''printf '%s\n' "$*" >> '''
-      '"${bashScriptPath(ghLog.path)}"',
-    );
-  }
-
-  buffer
-    ..writeln(r'''if [[ "$1" == "api" && "$2" == "user" ]]; then''')
-    ..writeln("  cat <<'JSON'")
-    ..writeln(jsonEncode({'login': 'test-user'}))
-    ..writeln('JSON')
-    ..writeln('  exit 0')
-    ..writeln('fi');
-
-  buffer
-    ..writeln(r'''if [[ "$1" == "api" && "$4" == "search/issues" ]]; then''')
-    ..writeln(
-      '  if [[ ! -f "${bashScriptPath(failureStateFile.path)}" ]]; then',
-    )
-    ..writeln('    touch "${bashScriptPath(failureStateFile.path)}"')
-    ..writeln(r'''    echo "error connecting to api.github.com" >&2''')
-    ..writeln(
-      r'''    echo "check your internet connection or https://githubstatus.com" >&2''',
-    )
-    ..writeln('    exit 1')
-    ..writeln(r'''  fi''')
-    ..writeln("  cat <<'JSON'")
-    ..writeln(searchResponse)
-    ..writeln('JSON')
-    ..writeln('  exit 0')
-    ..writeln('fi');
-
-  for (final entry in commentResponses.entries) {
-    buffer
-      ..writeln(
-        'if [[ "\$1" == "api" && "\$4" == '
-        '"repos/owner/sample/issues/${entry.key}/comments?per_page=100" ]]; then',
-      )
-      ..writeln("  cat <<'JSON'")
-      ..writeln(jsonEncode(entry.value))
-      ..writeln('JSON')
-      ..writeln('  exit 0')
-      ..writeln('fi');
-  }
-
-  buffer
-    ..writeln(r'''echo "unexpected gh args: $*" >&2''')
-    ..writeln('exit 1');
-
-  await ghScript.writeAsString(buffer.toString());
-  await makeScriptExecutable(ghScript);
+  _registerFakeGhCommand(
+    command: ghScript.path,
+    ghLog: ghLog,
+    searchResponse: {
+      'total_count': searchItems.length,
+      'incomplete_results': false,
+      'items': searchItems,
+    },
+    flakySearchStateFile: failureStateFile,
+    issueLists: const {},
+    comments: {'owner/sample': commentResponses},
+    postIssueNumbers: const {},
+  );
 }
 
 Future<void> writeWebhookForwardGhScript({
@@ -307,12 +120,6 @@ Future<void> writeWebhookForwardGhScript({
   String? viewerLogin,
 }) async {
   final issueNumber = issue['number'] as int;
-  final payload = {
-    'action': 'created',
-    'issue': issue,
-    'comment': comments.last,
-    'repository': {'full_name': repo},
-  };
   final searchItems = issueListResponse
       .map(
         (searchIssue) => <String, Object?>{
@@ -321,109 +128,31 @@ Future<void> writeWebhookForwardGhScript({
         },
       )
       .toList(growable: false);
-  final searchResponse = jsonEncode({
-    'total_count': searchItems.length,
-    'incomplete_results': false,
-    'items': searchItems,
-  });
 
-  final buffer = StringBuffer()
-    ..writeln('#!/usr/bin/env bash')
-    ..writeln('set -euo pipefail');
-
-  if (ghLog != null) {
-    buffer.writeln(
-      r'''printf '%s\n' "$*" >> '''
-      '"${bashScriptPath(ghLog.path)}"',
-    );
-  }
-
-  buffer.writeln(r'''if [[ "$1" == "api" && "$2" == "user" ]]; then''');
-  buffer
-    ..writeln("  cat <<'JSON'")
-    ..writeln(jsonEncode({'login': viewerLogin ?? 'test-user'}))
-    ..writeln('JSON')
-    ..writeln('  exit 0')
-    ..writeln('fi');
-
-  buffer
-    ..writeln(r'''if [[ "$1" == "api" && "$4" == "search/issues" ]]; then''')
-    ..writeln("  cat <<'JSON'")
-    ..writeln(searchResponse)
-    ..writeln('JSON')
-    ..writeln('  exit 0')
-    ..writeln('fi');
-
-  buffer
-    ..writeln(
-      'if [[ "\$1" == "api" && "\$4" == '
-      '"repos/$repo/issues/$issueNumber/comments?per_page=100" ]]; then',
-    )
-    ..writeln("  cat <<'JSON'")
-    ..writeln(jsonEncode(comments))
-    ..writeln('JSON')
-    ..writeln('  exit 0')
-    ..writeln('fi');
-
-  buffer
-    ..writeln(
-      'if [[ "\$1" == "api" && "\$4" == '
-      '"repos/$repo/issues/$issueNumber/comments" ]]; then',
-    )
-    ..writeln(r'''  for arg in "$@"; do''')
-    ..writeln(r'''    :''');
-  if (postedBodyFile != null) {
-    buffer
-      ..writeln(r'''    if [[ "$arg" == body=* ]]; then''')
-      ..writeln(
-        r'''      printf '%s' "${arg#body=}" > '''
-        '"${bashScriptPath(postedBodyFile.path)}"',
-      )
-      ..writeln(r'''    fi''');
-  }
-  buffer
-    ..writeln(r'''  done''')
-    ..writeln("  cat <<'JSON'")
-    ..writeln(
-      jsonEncode({
-        'id': 702,
-        'html_url': 'https://example.test/comment/702',
-        'body': 'posted',
-      }),
-    )
-    ..writeln('JSON')
-    ..writeln('  exit 0')
-    ..writeln('fi');
-
-  buffer
-    ..writeln(r'''if [[ "$1" == "webhook" && "$2" == "forward" ]]; then''')
-    ..writeln(r'''  url=""''')
-    ..writeln(r'''  for arg in "$@"; do''')
-    ..writeln(r'''    if [[ "$arg" == --url=* ]]; then''')
-    ..writeln(r'''      url="${arg#--url=}"''')
-    ..writeln(r'''    fi''')
-    ..writeln(r'''  done''')
-    ..writeln(r'''  if [[ -z "$url" ]]; then''')
-    ..writeln(r'''    echo "missing --url" >&2''')
-    ..writeln('    exit 1')
-    ..writeln(r'''  fi''')
-    ..writeln(r'''  curl -sS -X POST \''')
-    ..writeln(r'''    -H "Content-Type: application/json" \''')
-    ..writeln(r'''    -H "X-GitHub-Event: issue_comment" \''')
-    ..writeln(r'''    --data-binary @- "$url" <<'JSON' >/dev/null''')
-    ..writeln(jsonEncode(payload))
-    ..writeln('JSON')
-    ..writeln(r'''  while true; do''')
-    ..writeln(r'''    sleep 60''')
-    ..writeln(r'''  done''')
-    ..writeln('fi');
-
-  buffer
-    ..writeln(r'''echo "unexpected gh args: $*" >&2''')
-    ..writeln('exit 1');
-
-  await ghScript.writeAsString(buffer.toString());
-  await makeScriptExecutable(ghScript);
+  _registerFakeGhCommand(
+    command: ghScript.path,
+    ghLog: ghLog,
+    viewerLogin: viewerLogin,
+    searchResponse: {
+      'total_count': searchItems.length,
+      'incomplete_results': false,
+      'items': searchItems,
+    },
+    issueLists: const {},
+    comments: {
+      repo: {issueNumber: comments},
+    },
+    postIssueNumbers: {
+      repo: {issueNumber},
+    },
+    postedBodyFile: postedBodyFile,
+    webhookPayload: {
+      'action': 'created',
+      'issue': issue,
+      'comment': comments.last,
+      'repository': {'full_name': repo},
+    },
+  );
 }
 
 Future<void> writeGitHubGosmeeGhScript({
@@ -445,114 +174,234 @@ Future<void> writeGitHubGosmeeGhScript({
         },
       )
       .toList(growable: false);
-  final searchResponse = jsonEncode({
-    'total_count': searchItems.length,
-    'incomplete_results': false,
-    'items': searchItems,
-  });
-  final buffer = StringBuffer()
-    ..writeln('#!/usr/bin/env bash')
-    ..writeln('set -euo pipefail');
 
-  if (ghLog != null) {
-    buffer.writeln(
-      r'''printf '%s\n' "$*" >> '''
-      '"${bashScriptPath(ghLog.path)}"',
-    );
-  }
-
-  buffer.writeln(r'''if [[ "$1" == "api" && "$2" == "user" ]]; then''');
-  buffer
-    ..writeln("  cat <<'JSON'")
-    ..writeln(jsonEncode({'login': viewerLogin ?? 'test-user'}))
-    ..writeln('JSON')
-    ..writeln('  exit 0')
-    ..writeln('fi');
-
-  buffer
-    ..writeln(r'''if [[ "$1" == "api" && "$4" == "search/issues" ]]; then''')
-    ..writeln("  cat <<'JSON'")
-    ..writeln(searchResponse)
-    ..writeln('JSON')
-    ..writeln('  exit 0')
-    ..writeln('fi');
-
-  buffer
-    ..writeln(
-      'if [[ "\$1" == "api" && "\$4" == '
-      '"repos/$repo/issues/$issueNumber/comments?per_page=100" ]]; then',
-    )
-    ..writeln("  cat <<'JSON'")
-    ..writeln(jsonEncode(comments))
-    ..writeln('JSON')
-    ..writeln('  exit 0')
-    ..writeln('fi');
-
-  buffer
-    ..writeln('if [[ "\$1" == "api" && "\$4" == "repos/$repo/hooks" ]]; then')
-    ..writeln(r'''  active_flag=""''')
-    ..writeln(r'''  for ((i = 1; i <= $#; i += 1)); do''')
-    ..writeln(r'''    if [[ "${!i}" == "active=true" ]]; then''')
-    ..writeln(r'''      prev_index=$((i - 1))''')
-    ..writeln(r'''      active_flag="${!prev_index}"''')
-    ..writeln(r'''      break''')
-    ..writeln(r'''    fi''')
-    ..writeln(r'''  done''')
-    ..writeln(
-      r'''  if [[ "$active_flag" != "-F" && "$active_flag" != "--field" ]]; then''',
-    )
-    ..writeln(
-      r'''    echo "expected active=true to be sent with -F/--field, got: $*" >&2''',
-    )
-    ..writeln(r'''    exit 1''')
-    ..writeln(r'''  fi''')
-    ..writeln("  cat <<'JSON'")
-    ..writeln(jsonEncode({'id': webhookId}))
-    ..writeln('JSON')
-    ..writeln('  exit 0')
-    ..writeln('fi');
-
-  buffer
-    ..writeln(
-      'if [[ "\$1" == "api" && "\$4" == '
-      '"repos/$repo/issues/$issueNumber/comments" ]]; then',
-    )
-    ..writeln(r'''  for arg in "$@"; do''')
-    ..writeln(r'''    :''');
-  if (postedBodyFile != null) {
-    buffer
-      ..writeln(r'''    if [[ "$arg" == body=* ]]; then''')
-      ..writeln(
-        r'''      printf '%s' "${arg#body=}" > '''
-        '"${bashScriptPath(postedBodyFile.path)}"',
-      )
-      ..writeln(r'''    fi''');
-  }
-  buffer
-    ..writeln(r'''  done''')
-    ..writeln("  cat <<'JSON'")
-    ..writeln(
-      jsonEncode({
-        'id': 703,
-        'html_url': 'https://example.test/comment/703',
-        'body': 'posted',
-      }),
-    )
-    ..writeln('JSON')
-    ..writeln('  exit 0')
-    ..writeln('fi');
-
-  buffer
-    ..writeln(
-      'if [[ "\$1" == "api" && "\$4" == "repos/$repo/hooks/$webhookId" ]]; then',
-    )
-    ..writeln('  exit 0')
-    ..writeln('fi');
-
-  buffer
-    ..writeln(r'''echo "unexpected gh args: $*" >&2''')
-    ..writeln('exit 1');
-
-  await ghScript.writeAsString(buffer.toString());
-  await makeScriptExecutable(ghScript);
+  _registerFakeGhCommand(
+    command: ghScript.path,
+    ghLog: ghLog,
+    viewerLogin: viewerLogin,
+    searchResponse: {
+      'total_count': searchItems.length,
+      'incomplete_results': false,
+      'items': searchItems,
+    },
+    issueLists: const {},
+    comments: {
+      repo: {issueNumber: comments},
+    },
+    postIssueNumbers: {
+      repo: {issueNumber},
+    },
+    postedBodyFile: postedBodyFile,
+    webhookIdsByRepo: {repo: webhookId},
+  );
+}
+
+void _registerFakeGhCommand({
+  required String command,
+  required Map<String, Object?> searchResponse,
+  required Map<String, List<Map<String, Object?>>> issueLists,
+  required Map<String, Map<int, List<Map<String, Object?>>>> comments,
+  required Map<String, Set<int>> postIssueNumbers,
+  File? ghLog,
+  bool failViewerLookup = false,
+  String? viewerLogin,
+  Map<String, Object?>? openSearchResponse,
+  File? postedBodyFile,
+  File? reactionBodyFile,
+  File? flakySearchStateFile,
+  Map<String, Object?>? webhookPayload,
+  Map<String, int>? webhookIdsByRepo,
+}) {
+  if (webhookPayload != null) {
+    fakeStartedCommandHandlers[command] = (arguments) async {
+      if (ghLog != null) {
+        await _appendLine(ghLog, '${arguments.join(' ')}\n');
+      }
+      final process = FakeStartedExternalCommand();
+      final targetUrl = _argumentValue(arguments, '--url=');
+      if (targetUrl != null) {
+        unawaited(_postGitHubWebhook(targetUrl, webhookPayload));
+      }
+      return process;
+    };
+  }
+
+  fakeCommandHandlers[command] = (arguments, {timeout}) async {
+    if (ghLog != null) {
+      await _appendLine(ghLog, '${arguments.join(' ')}\n');
+    }
+
+    ProcessResult result(
+      Object? stdout, {
+      int exitCode = 0,
+      String stderr = '',
+    }) {
+      final stdoutText = stdout is String ? stdout : jsonEncode(stdout);
+      return ProcessResult(0, exitCode, stdoutText, stderr);
+    }
+
+    if (_argsMatch(arguments, ['api', 'user'])) {
+      if (failViewerLookup) {
+        return result('', exitCode: 1, stderr: 'viewer lookup failed\n');
+      }
+      return result({'login': viewerLogin ?? 'test-user'});
+    }
+
+    if (_argsMatchAt(arguments, 0, 'api') &&
+        _argsMatchAt(arguments, 3, 'search/issues')) {
+      if (flakySearchStateFile != null &&
+          !await flakySearchStateFile.exists()) {
+        await flakySearchStateFile.writeAsString('failed-once');
+        return result(
+          '',
+          exitCode: 1,
+          stderr:
+              'error connecting to api.github.com\ncheck your internet connection or https://githubstatus.com\n',
+        );
+      }
+      final query = arguments
+          .where((argument) => argument.startsWith('q='))
+          .map((argument) => argument.substring(2))
+          .firstOrNull;
+      return result(
+        query?.contains('state:open') ?? false
+            ? (openSearchResponse ?? searchResponse)
+            : searchResponse,
+      );
+    }
+
+    for (final entry in issueLists.entries) {
+      final path = 'repos/${entry.key}/issues?';
+      if (_argsMatchAt(arguments, 0, 'api') &&
+          arguments.length > 3 &&
+          arguments[3].startsWith(path)) {
+        return result(entry.value);
+      }
+    }
+
+    for (final repoEntry in comments.entries) {
+      for (final entry in repoEntry.value.entries) {
+        if (_argsMatchAt(arguments, 0, 'api') &&
+            _argsMatchAt(
+              arguments,
+              3,
+              'repos/${repoEntry.key}/issues/${entry.key}/comments?per_page=100',
+            )) {
+          return result(entry.value);
+        }
+      }
+    }
+
+    for (final repoEntry in postIssueNumbers.entries) {
+      for (final issueNumber in repoEntry.value) {
+        if (_argsMatchAt(arguments, 0, 'api') &&
+            _argsMatchAt(
+              arguments,
+              3,
+              'repos/${repoEntry.key}/issues/$issueNumber/comments',
+            )) {
+          final body = _argumentValue(arguments, 'body=');
+          if (postedBodyFile != null && body != null) {
+            await postedBodyFile.writeAsString(body);
+          }
+          return result({
+            'id': 700,
+            'html_url': 'https://example.test/comment/700',
+            'body': 'posted',
+          });
+        }
+      }
+    }
+
+    for (final repoEntry in comments.entries) {
+      for (final issueEntry in repoEntry.value.entries) {
+        for (final comment in issueEntry.value) {
+          final commentId = comment['id'];
+          if (commentId is int &&
+              _argsMatchAt(arguments, 0, 'api') &&
+              _argsMatchAt(
+                arguments,
+                3,
+                'repos/${repoEntry.key}/issues/comments/$commentId/reactions',
+              )) {
+            final content = _argumentValue(arguments, 'content=');
+            if (reactionBodyFile != null && content != null) {
+              await reactionBodyFile.writeAsString(content);
+            }
+            return result({'id': 990, 'content': 'eyes'});
+          }
+        }
+      }
+    }
+
+    for (final entry in (webhookIdsByRepo ?? const <String, int>{}).entries) {
+      final hooksPath = 'repos/${entry.key}/hooks';
+      if (_argsMatchAt(arguments, 0, 'api') &&
+          _argsMatchAt(arguments, 3, hooksPath)) {
+        return result({'id': entry.value});
+      }
+      if (_argsMatchAt(arguments, 0, 'api') &&
+          _argsMatchAt(arguments, 3, '$hooksPath/${entry.value}')) {
+        return result(null);
+      }
+    }
+
+    return result(
+      '',
+      exitCode: 1,
+      stderr: 'unexpected gh args: ${arguments.join(' ')}\n',
+    );
+  };
+}
+
+Future<void> _postGitHubWebhook(
+  String targetUrl,
+  Map<String, Object?> webhookPayload,
+) async {
+  final client = HttpClient();
+  try {
+    final request = await client.postUrl(Uri.parse(targetUrl));
+    request.headers.contentType = ContentType.json;
+    request.headers.set('X-GitHub-Event', 'issue_comment');
+    request.write(jsonEncode(webhookPayload));
+    await request.close();
+  } finally {
+    client.close(force: true);
+  }
+}
+
+bool _argsMatch(List<String> arguments, List<String> expected) =>
+    arguments.length >= expected.length &&
+    Iterable.generate(
+      expected.length,
+    ).every((index) => arguments[index] == expected[index]);
+
+bool _argsMatchAt(List<String> arguments, int index, String expected) =>
+    arguments.length > index && arguments[index] == expected;
+
+String? _argumentValue(List<String> arguments, String prefix) {
+  for (final argument in arguments) {
+    if (argument.startsWith(prefix)) {
+      return argument.substring(prefix.length);
+    }
+  }
+  return null;
+}
+
+Future<void> _appendLine(File file, String line) async {
+  for (var attempt = 0; attempt < 200; attempt += 1) {
+    RandomAccessFile? log;
+    try {
+      log = file.openSync(mode: FileMode.append);
+      log.lockSync(FileLock.exclusive);
+      log.writeStringSync(line);
+      log.unlockSync();
+      return;
+    } on FileSystemException {
+      await Future<void>.delayed(const Duration(milliseconds: 5));
+    } finally {
+      log?.closeSync();
+    }
+  }
+  await file.writeAsString(line, mode: FileMode.append);
 }
diff --git a/test/support/fake_glab.dart b/test/support/fake_glab.dart
index c549e02..4ea0a00 100644
--- a/test/support/fake_glab.dart
+++ b/test/support/fake_glab.dart
@@ -15,7 +15,7 @@ Future<void> writeFakeGlabScript({
   bool failViewerLookup = false,
   Map<String, int>? webhookIdsByRepo,
 }) async {
-  final normalizedPostCommentIssueNumbersByRepo =
+  final postIssueNumbers =
       postCommentIssueNumbersByRepo ??
       <String, Set<int>>{
         for (final entry in issueListResponsesByRepo.entries)
@@ -24,123 +24,110 @@ Future<void> writeFakeGlabScript({
               .whereType<int>()
               .toSet(),
       };
-
-  final buffer = StringBuffer()
-    ..writeln('#!/usr/bin/env bash')
-    ..writeln('set -euo pipefail');
-
-  if (glabLog != null) {
-    buffer.writeln(
-      r'''printf '%s\n' "$*" >> '''
-      '"${bashScriptPath(glabLog.path)}"',
-    );
-  }
-
-  buffer.writeln(r'''if [[ "$1" == "api" && "$2" == "user" ]]; then''');
-  if (failViewerLookup) {
-    buffer
-      ..writeln(r'''  echo "viewer lookup failed" >&2''')
-      ..writeln('  exit 1')
-      ..writeln('fi');
-  } else {
-    buffer
-      ..writeln("  cat <<'JSON'")
-      ..writeln(jsonEncode({'username': viewerLogin ?? 'glab-user'}))
-      ..writeln('JSON')
-      ..writeln('  exit 0')
-      ..writeln('fi');
-  }
-
-  for (final entry in issueListResponsesByRepo.entries) {
-    final repo = Uri.encodeComponent(entry.key);
-    buffer
-      ..writeln(
-        r'''if [[ "$1" == "api" && "$4" == "projects/'''
-        '$repo'
-        r'''/issues?state=opened"* ]]; then''',
-      )
-      ..writeln("  cat <<'JSON'")
-      ..writeln(jsonEncode(entry.value))
-      ..writeln('JSON')
-      ..writeln('  exit 0')
-      ..writeln('fi');
-  }
-
-  for (final repoEntry in commentResponsesByRepo.entries) {
-    final repo = Uri.encodeComponent(repoEntry.key);
-    for (final entry in repoEntry.value.entries) {
-      buffer
-        ..writeln(
-          'if [[ "\$1" == "api" && "\$4" == '
-          '"projects/$repo/issues/${entry.key}/notes?per_page=100" ]]; then',
-        )
-        ..writeln("  cat <<'JSON'")
-        ..writeln(jsonEncode(entry.value))
-        ..writeln('JSON')
-        ..writeln('  exit 0')
-        ..writeln('fi');
+  fakeCommandHandlers[glabScript.path] = (arguments, {timeout}) async {
+    if (glabLog != null) {
+      await glabLog.writeAsString(
+        '${arguments.join(' ')}\n',
+        mode: FileMode.append,
+      );
     }
-  }
 
-  for (final repoEntry in normalizedPostCommentIssueNumbersByRepo.entries) {
-    final repo = Uri.encodeComponent(repoEntry.key);
-    for (final issueNumber in repoEntry.value) {
-      buffer
-        ..writeln(
-          'if [[ "\$1" == "api" && "\$4" == '
-          '"projects/$repo/issues/$issueNumber/notes" ]]; then',
-        )
-        ..writeln(r'''  for arg in "$@"; do''')
-        ..writeln(r'''    :''');
-      if (postedBodyFile != null) {
-        buffer
-          ..writeln(r'''    if [[ "$arg" == body=* ]]; then''')
-          ..writeln(
-            r'''      printf '%s' "${arg#body=}" > '''
-            '"${bashScriptPath(postedBodyFile.path)}"',
-          )
-          ..writeln(r'''    fi''');
+    ProcessResult result(
+      Object? stdout, {
+      int exitCode = 0,
+      String stderr = '',
+    }) {
+      return ProcessResult(
+        0,
+        exitCode,
+        stdout is String ? stdout : jsonEncode(stdout),
+        stderr,
+      );
+    }
+
+    if (_matches(arguments, 0, 'api') && _matches(arguments, 1, 'user')) {
+      if (failViewerLookup) {
+        return result('', exitCode: 1, stderr: 'viewer lookup failed\n');
       }
-      buffer
-        ..writeln(r'''  done''')
-        ..writeln("  cat <<'JSON'")
-        ..writeln(
-          jsonEncode({
+      return result({'username': viewerLogin ?? 'glab-user'});
+    }
+
+    for (final entry in issueListResponsesByRepo.entries) {
+      final repo = Uri.encodeComponent(entry.key);
+      if (_matches(arguments, 0, 'api') &&
+          arguments.length > 3 &&
+          arguments[3].startsWith('projects/$repo/issues?state=opened')) {
+        return result(entry.value);
+      }
+    }
+
+    for (final repoEntry in commentResponsesByRepo.entries) {
+      final repo = Uri.encodeComponent(repoEntry.key);
+      for (final entry in repoEntry.value.entries) {
+        if (_matches(arguments, 0, 'api') &&
+            _matches(
+              arguments,
+              3,
+              'projects/$repo/issues/${entry.key}/notes?per_page=100',
+            )) {
+          return result(entry.value);
+        }
+      }
+    }
+
+    for (final repoEntry in postIssueNumbers.entries) {
+      final repo = Uri.encodeComponent(repoEntry.key);
+      for (final issueNumber in repoEntry.value) {
+        if (_matches(arguments, 0, 'api') &&
+            _matches(
+              arguments,
+              3,
+              'projects/$repo/issues/$issueNumber/notes',
+            )) {
+          final body = _valueArg(arguments, 'body=');
+          if (postedBodyFile != null && body != null) {
+            await postedBodyFile.writeAsString(body);
+          }
+          return result({
             'id': 901,
             'body': 'posted',
             'noteable_url':
                 'https://gitlab.example.test/group/subgroup/sample/issues/$issueNumber',
-          }),
-        )
-        ..writeln('JSON')
-        ..writeln('  exit 0')
-        ..writeln('fi');
+          });
+        }
+      }
+    }
+
+    for (final entry in (webhookIdsByRepo ?? const <String, int>{}).entries) {
+      final repo = Uri.encodeComponent(entry.key);
+      if (_matches(arguments, 0, 'api') &&
+          _matches(arguments, 2, 'POST') &&
+          _matches(arguments, 3, 'projects/$repo/hooks')) {
+        return result({'id': entry.value});
+      }
+      if (_matches(arguments, 0, 'api') &&
+          _matches(arguments, 2, 'DELETE') &&
+          _matches(arguments, 3, 'projects/$repo/hooks/${entry.value}')) {
+        return result(null);
+      }
+    }
+
+    return result(
+      '',
+      exitCode: 1,
+      stderr: 'unexpected glab args: ${arguments.join(' ')}\n',
+    );
+  };
+}
+
+bool _matches(List<String> arguments, int index, String value) =>
+    arguments.length > index && arguments[index] == value;
+
+String? _valueArg(List<String> arguments, String prefix) {
+  for (final argument in arguments) {
+    if (argument.startsWith(prefix)) {
+      return argument.substring(prefix.length);
     }
   }
-
-  for (final entry in (webhookIdsByRepo ?? const <String, int>{}).entries) {
-    final repo = Uri.encodeComponent(entry.key);
-    buffer
-      ..writeln(
-        'if [[ "\$1" == "api" && "\$4" == "projects/$repo/hooks" && "\$3" == "POST" ]]; then',
-      )
-      ..writeln("  cat <<'JSON'")
-      ..writeln(jsonEncode({'id': entry.value}))
-      ..writeln('JSON')
-      ..writeln('  exit 0')
-      ..writeln('fi')
-      ..writeln(
-        'if [[ "\$1" == "api" && "\$4" == "projects/$repo/hooks/${entry.value}" && "\$3" == "DELETE" ]]; then',
-      )
-      ..writeln("  printf '%s\\n' 'null'")
-      ..writeln('  exit 0')
-      ..writeln('fi');
-  }
-
-  buffer
-    ..writeln(r'''echo "unexpected glab args: $*" >&2''')
-    ..writeln('exit 1');
-
-  await glabScript.writeAsString(buffer.toString());
-  await makeScriptExecutable(glabScript);
+  return null;
 }
diff --git a/test/support/fake_gosmee.dart b/test/support/fake_gosmee.dart
index 5682cf3..172a316 100644
--- a/test/support/fake_gosmee.dart
+++ b/test/support/fake_gosmee.dart
@@ -1,3 +1,4 @@
+import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
@@ -9,55 +10,94 @@ Future<void> writeGosmeeForwardScript({
   required Map<String, Object?> payload,
   File? gosmeeLog,
 }) async {
-  final buffer = StringBuffer()
-    ..writeln('#!/usr/bin/env bash')
-    ..writeln('set -euo pipefail');
-
-  if (gosmeeLog != null) {
-    buffer.writeln(
-      r'''printf '%s\n' "$*" >> '''
-      '"${bashScriptPath(gosmeeLog.path)}"',
-    );
-  }
-
-  buffer
-    ..writeln(
-      r'''if [[ "$1" == "--output" && "$2" == "json" && "$3" == "client" && "$4" == "--new-url" ]]; then''',
-    )
-    ..writeln(
-      r'''  printf '%s\n' '''
-      "'$publicUrl'",
-    )
-    ..writeln('  exit 0')
-    ..writeln('fi');
-
-  buffer
-    ..writeln(r'''if [[ "$1" == "client" ]]; then''')
-    ..writeln(r'''  url="$2"''')
-    ..writeln(r'''  target="$3"''')
-    ..writeln(
-      r'''  if [[ "$url" != '''
-      "'$publicUrl'"
-      r''' ]]; then''',
-    )
-    ..writeln(r'''    echo "unexpected gosmee url: $url" >&2''')
-    ..writeln('    exit 1')
-    ..writeln(r'''  fi''')
-    ..writeln(r'''  curl -sS -X POST \''')
-    ..writeln(r'''    -H "Content-Type: application/json" \''')
-    ..writeln(r'''    -H "X-Gitea-Event: issue_comment" \''')
-    ..writeln(r'''    --data-binary @- "$target" <<'JSON' >/dev/null''')
-    ..writeln(jsonEncode(payload))
-    ..writeln('JSON')
-    ..writeln(r'''  while true; do''')
-    ..writeln(r'''    sleep 60''')
-    ..writeln(r'''  done''')
-    ..writeln('fi');
-
-  buffer
-    ..writeln(r'''echo "unexpected gosmee args: $*" >&2''')
-    ..writeln('exit 1');
-
-  await gosmeeScript.writeAsString(buffer.toString());
-  await makeScriptExecutable(gosmeeScript);
+  registerFakeGosmeeCommand(
+    command: gosmeeScript.path,
+    publicUrl: publicUrl,
+    payload: payload,
+    gosmeeLog: gosmeeLog,
+  );
+}
+
+void registerFakeGosmeeCommand({
+  required String command,
+  required String publicUrl,
+  Map<String, Object?>? payload,
+  File? gosmeeLog,
+  String webhookHeader = 'X-Gitea-Event',
+}) {
+  fakeCommandHandlers[command] = (arguments, {timeout}) async {
+    if (gosmeeLog != null) {
+      await _appendLine(gosmeeLog, '${arguments.join(' ')}\n');
+    }
+    if (_matchesNewUrl(arguments)) {
+      return ProcessResult(0, 0, publicUrl, '');
+    }
+    return ProcessResult(
+      0,
+      1,
+      '',
+      'unexpected gosmee args: ${arguments.join(' ')}\n',
+    );
+  };
+
+  fakeStartedCommandHandlers[command] = (arguments) async {
+    if (gosmeeLog != null) {
+      await _appendLine(gosmeeLog, '${arguments.join(' ')}\n');
+    }
+    final process = FakeStartedExternalCommand();
+    if (arguments.length >= 3 &&
+        arguments[0] == 'client' &&
+        arguments[1] == publicUrl) {
+      if (payload != null) {
+        unawaited(_postWebhook(arguments[2], payload, webhookHeader));
+      }
+      return process;
+    }
+    process.addStderr('unexpected gosmee args: ${arguments.join(' ')}\n');
+    process.complete(1);
+    return process;
+  };
+}
+
+bool _matchesNewUrl(List<String> arguments) {
+  return arguments.length >= 4 &&
+      arguments[0] == '--output' &&
+      arguments[1] == 'json' &&
+      arguments[2] == 'client' &&
+      arguments[3] == '--new-url';
+}
+
+Future<void> _postWebhook(
+  String targetUrl,
+  Map<String, Object?> payload,
+  String webhookHeader,
+) async {
+  final client = HttpClient();
+  try {
+    final request = await client.postUrl(Uri.parse(targetUrl));
+    request.headers.contentType = ContentType.json;
+    request.headers.set(webhookHeader, 'issue_comment');
+    request.write(jsonEncode(payload));
+    await request.close();
+  } finally {
+    client.close(force: true);
+  }
+}
+
+Future<void> _appendLine(File file, String line) async {
+  for (var attempt = 0; attempt < 200; attempt += 1) {
+    RandomAccessFile? log;
+    try {
+      log = file.openSync(mode: FileMode.append);
+      log.lockSync(FileLock.exclusive);
+      log.writeStringSync(line);
+      log.unlockSync();
+      return;
+    } on FileSystemException {
+      await Future<void>.delayed(const Duration(milliseconds: 5));
+    } finally {
+      log?.closeSync();
+    }
+  }
+  await file.writeAsString(line, mode: FileMode.append);
 }
diff --git a/test/support/fake_responders.dart b/test/support/fake_responders.dart
index 3328898..ca08d72 100644
--- a/test/support/fake_responders.dart
+++ b/test/support/fake_responders.dart
@@ -1,7 +1,14 @@
 import 'dart:convert';
 import 'dart:io';
 
-import 'script_utils.dart';
+import 'package:code_work_spawner/src/config/config.dart';
+import 'package:code_work_spawner/src/core/cli_responder.dart';
+import 'package:code_work_spawner/src/issue_tracker/issue_tracker_client.dart';
+
+final Map<String, _FakeResponder> _fakeResponders = {};
+
+CliResponderRunner fakeResponderRunner() =>
+    FakeResponderRunner(Map<String, _FakeResponder>.from(_fakeResponders));
 
 Future<void> writeResponderScript(
   File responderScript,
@@ -9,33 +16,34 @@ Future<void> writeResponderScript(
   String stderr = '',
   int exitCode = 0,
 }) async {
-  await responderScript.writeAsString('''#!/usr/bin/env bash
-set -euo pipefail
-cat >/dev/null
-${stderr.isEmpty ? '' : "printf '%s\\n' ${jsonEncode(stderr)} >&2"}
-cat <<'JSON'
-${jsonEncode(response)}
-JSON
-exit $exitCode
-''');
-  await makeScriptExecutable(responderScript);
+  _fakeResponders[responderScript.path] = _FakeResponder(
+    response: response,
+    stderr: stderr,
+    exitCode: exitCode,
+  );
+}
+
+Future<void> writeCapturingResponderScript(
+  File responderScript,
+  Map<String, Object?> response, {
+  File? cwdCapture,
+  File? stdinCapture,
+}) async {
+  _fakeResponders[responderScript.path] = _FakeResponder(
+    response: response,
+    cwdCapture: cwdCapture,
+    stdinCapture: stdinCapture,
+  );
 }
 
 Future<void> writeJsonlResponderScript(
   File responderScript,
   Map<String, Object?> response,
 ) async {
-  await responderScript.writeAsString('''#!/usr/bin/env bash
-set -euo pipefail
-cat >/dev/null
-cat <<'JSON'
-{"type":"thread.started","thread_id":"test-thread"}
-{"type":"turn.started"}
-{"type":"item.completed","item":{"id":"item_0","type":"agent_message","text":${jsonEncode(jsonEncode(response))}}}
-{"type":"turn.completed"}
-JSON
-''');
-  await makeScriptExecutable(responderScript);
+  _fakeResponders[responderScript.path] = _FakeResponder(
+    response: response,
+    emitsJsonl: true,
+  );
 }
 
 Future<void> writeDelayedLoggingResponderScript(
@@ -44,21 +52,142 @@ Future<void> writeDelayedLoggingResponderScript(
   required Duration delay,
   required Map<String, Object?> response,
 }) async {
-  await responderScript.writeAsString('''#!/usr/bin/env bash
-set -euo pipefail
-timestamp_ms() {
-  python3 - <<'PY'
-import time
-print(int(time.time() * 1000))
-PY
+  _fakeResponders[responderScript.path] = _FakeResponder(
+    response: response,
+    eventLog: eventLog,
+    delay: delay,
+  );
 }
-printf 'start:%s:%s\n' "\$CWS_ISSUE_NUMBER" "\$(timestamp_ms)" >> "${bashScriptPath(eventLog.path)}"
-cat >/dev/null
-sleep ${delay.inSeconds}
-printf 'end:%s:%s\n' "\$CWS_ISSUE_NUMBER" "\$(timestamp_ms)" >> "${bashScriptPath(eventLog.path)}"
-cat <<'JSON'
-${jsonEncode(response)}
-JSON
-''');
-  await makeScriptExecutable(responderScript);
+
+class FakeResponderRunner extends CliResponderRunner {
+  FakeResponderRunner(this._responders);
+
+  final Map<String, _FakeResponder> _responders;
+
+  @override
+  Future<ResponderResult> run({
+    required CliResponderConfig responder,
+    required ProjectConfig project,
+    required IssueThread thread,
+    required String prompt,
+    required String workspacePath,
+  }) async {
+    final fake = _responders[responder.command];
+    if (fake == null) {
+      throw StateError(
+        'No fake responder registered for command ${responder.command}.',
+      );
+    }
+
+    final context = <String, String>{
+      'prompt': prompt,
+      'repo': project.repo,
+      'project_key': project.key,
+      'project_path': project.path,
+      'workspace_path': workspacePath,
+      'issue_number': thread.issue.number.toString(),
+      'thread_json': encodePrettyJson(thread.toJson()),
+    };
+    final stdinPayload = renderTemplate(responder.stdinTemplate, context);
+
+    await fake.run(
+      issueNumber: thread.issue.number,
+      stdinPayload: stdinPayload,
+      workspacePath: workspacePath,
+    );
+    final rawStdout = fake.rawStdout;
+    if (fake.exitCode != 0) {
+      throw CliResponderExecutionException(
+        responderId: responder.id,
+        command: responder.command,
+        arguments: responder.args,
+        exitCode: fake.exitCode,
+        rawStdout: rawStdout,
+        rawStderr: fake.stderr,
+      );
+    }
+
+    return ResponderResult.fromJson(
+      fake.response,
+      responderId: responder.id,
+      rawStdout: rawStdout,
+      rawStderr: fake.stderr,
+    );
+  }
+}
+
+class _FakeResponder {
+  _FakeResponder({
+    required this.response,
+    this.stderr = '',
+    this.exitCode = 0,
+    this.emitsJsonl = false,
+    this.eventLog,
+    this.delay = Duration.zero,
+    this.cwdCapture,
+    this.stdinCapture,
+  });
+
+  final Map<String, Object?> response;
+  final String stderr;
+  final int exitCode;
+  final bool emitsJsonl;
+  final File? eventLog;
+  final Duration delay;
+  final File? cwdCapture;
+  final File? stdinCapture;
+
+  String get rawStdout {
+    if (!emitsJsonl) {
+      return jsonEncode(response);
+    }
+    return [
+      jsonEncode({'type': 'thread.started', 'thread_id': 'test-thread'}),
+      jsonEncode({'type': 'turn.started'}),
+      jsonEncode({
+        'type': 'item.completed',
+        'item': {
+          'id': 'item_0',
+          'type': 'agent_message',
+          'text': jsonEncode(response),
+        },
+      }),
+      jsonEncode({'type': 'turn.completed'}),
+      '',
+    ].join('\n');
+  }
+
+  Future<void> run({
+    required int issueNumber,
+    required String stdinPayload,
+    required String workspacePath,
+  }) async {
+    await cwdCapture?.writeAsString(workspacePath);
+    await stdinCapture?.writeAsString(stdinPayload);
+    if (eventLog != null) {
+      await _appendEvent('start', issueNumber);
+      await Future<void>.delayed(delay);
+      await _appendEvent('end', issueNumber);
+    }
+  }
+
+  Future<void> _appendEvent(String phase, int issueNumber) async {
+    final timestampMs = DateTime.now().microsecondsSinceEpoch ~/ 1000;
+    final line = '$phase:$issueNumber:$timestampMs\n';
+    for (var attempt = 0; attempt < 200; attempt += 1) {
+      RandomAccessFile? log;
+      try {
+        log = eventLog!.openSync(mode: FileMode.append);
+        log.lockSync(FileLock.exclusive);
+        log.writeStringSync(line);
+        log.unlockSync();
+        return;
+      } on FileSystemException {
+        await Future<void>.delayed(const Duration(milliseconds: 5));
+      } finally {
+        log?.closeSync();
+      }
+    }
+    await eventLog!.writeAsString(line, mode: FileMode.append);
+  }
 }
diff --git a/test/support/fake_tea.dart b/test/support/fake_tea.dart
index ec384a8..aba9396 100644
--- a/test/support/fake_tea.dart
+++ b/test/support/fake_tea.dart
@@ -14,7 +14,7 @@ Future<void> writeFakeTeaScript({
   String? viewerLogin,
   bool failViewerLookup = false,
 }) async {
-  final normalizedPostCommentIssueNumbersByRepo =
+  final postIssueNumbers =
       postCommentIssueNumbersByRepo ??
       <String, Set<int>>{
         for (final entry in issueListResponsesByRepo.entries)
@@ -23,103 +23,92 @@ Future<void> writeFakeTeaScript({
               .whereType<int>()
               .toSet(),
       };
-
-  final buffer = StringBuffer()
-    ..writeln('#!/usr/bin/env bash')
-    ..writeln('set -euo pipefail');
-
-  if (teaLog != null) {
-    buffer.writeln(
-      r'''printf '%s\n' "$*" >> '''
-      '"${bashScriptPath(teaLog.path)}"',
-    );
-  }
-
-  buffer.writeln(r'''if [[ "$1" == "api" && "$2" == "user" ]]; then''');
-  if (failViewerLookup) {
-    buffer
-      ..writeln(r'''  echo "viewer lookup failed" >&2''')
-      ..writeln('  exit 1')
-      ..writeln('fi');
-  } else {
-    buffer
-      ..writeln("  cat <<'JSON'")
-      ..writeln(jsonEncode({'login': viewerLogin ?? 'tea-user'}))
-      ..writeln('JSON')
-      ..writeln('  exit 0')
-      ..writeln('fi');
-  }
-
-  for (final entry in issueListResponsesByRepo.entries) {
-    final repo = entry.key;
-    buffer
-      ..writeln(
-        r'''if [[ "$1" == "api" && "$4" == "repos/'''
-        '$repo'
-        r'''/issues?state=open"* ]]; then''',
-      )
-      ..writeln("  cat <<'JSON'")
-      ..writeln(jsonEncode(entry.value))
-      ..writeln('JSON')
-      ..writeln('  exit 0')
-      ..writeln('fi');
-  }
-
-  for (final repoEntry in commentResponsesByRepo.entries) {
-    final repo = repoEntry.key;
-    for (final entry in repoEntry.value.entries) {
-      buffer
-        ..writeln(
-          'if [[ "\$1" == "api" && "\$4" == '
-          '"repos/$repo/issues/${entry.key}/comments?limit=100" ]]; then',
-        )
-        ..writeln("  cat <<'JSON'")
-        ..writeln(jsonEncode(entry.value))
-        ..writeln('JSON')
-        ..writeln('  exit 0')
-        ..writeln('fi');
+  fakeCommandHandlers[teaScript.path] = (arguments, {timeout}) async {
+    if (teaLog != null) {
+      await teaLog.writeAsString(
+        '${arguments.join(' ')}\n',
+        mode: FileMode.append,
+      );
     }
-  }
 
-  for (final repoEntry in normalizedPostCommentIssueNumbersByRepo.entries) {
-    final repo = repoEntry.key;
-    for (final issueNumber in repoEntry.value) {
-      buffer
-        ..writeln(
-          'if [[ "\$1" == "api" && "\$4" == '
-          '"repos/$repo/issues/$issueNumber/comments" ]]; then',
-        )
-        ..writeln(r'''  for arg in "$@"; do''')
-        ..writeln(r'''    :''');
-      if (postedBodyFile != null) {
-        buffer
-          ..writeln(r'''    if [[ "$arg" == body=* ]]; then''')
-          ..writeln(
-            r'''      printf '%s' "${arg#body=}" > '''
-            '"${bashScriptPath(postedBodyFile.path)}"',
-          )
-          ..writeln(r'''    fi''');
+    ProcessResult result(
+      Object? stdout, {
+      int exitCode = 0,
+      String stderr = '',
+    }) {
+      return ProcessResult(
+        0,
+        exitCode,
+        stdout is String ? stdout : jsonEncode(stdout),
+        stderr,
+      );
+    }
+
+    if (_matches(arguments, 0, 'api') && _matches(arguments, 1, 'user')) {
+      if (failViewerLookup) {
+        return result('', exitCode: 1, stderr: 'viewer lookup failed\n');
       }
-      buffer
-        ..writeln(r'''  done''')
-        ..writeln("  cat <<'JSON'")
-        ..writeln(
-          jsonEncode({
+      return result({'login': viewerLogin ?? 'tea-user'});
+    }
+
+    for (final entry in issueListResponsesByRepo.entries) {
+      if (_matches(arguments, 0, 'api') &&
+          arguments.length > 3 &&
+          arguments[3].startsWith('repos/${entry.key}/issues?state=open')) {
+        return result(entry.value);
+      }
+    }
+
+    for (final repoEntry in commentResponsesByRepo.entries) {
+      for (final entry in repoEntry.value.entries) {
+        if (_matches(arguments, 0, 'api') &&
+            _matches(
+              arguments,
+              3,
+              'repos/${repoEntry.key}/issues/${entry.key}/comments?limit=100',
+            )) {
+          return result(entry.value);
+        }
+      }
+    }
+
+    for (final repoEntry in postIssueNumbers.entries) {
+      for (final issueNumber in repoEntry.value) {
+        if (_matches(arguments, 0, 'api') &&
+            _matches(
+              arguments,
+              3,
+              'repos/${repoEntry.key}/issues/$issueNumber/comments',
+            )) {
+          final body = _valueArg(arguments, 'body=');
+          if (postedBodyFile != null && body != null) {
+            await postedBodyFile.writeAsString(body);
+          }
+          return result({
             'id': 701,
             'url': 'https://gitea.example.test/comment/701',
             'body': 'posted',
-          }),
-        )
-        ..writeln('JSON')
-        ..writeln('  exit 0')
-        ..writeln('fi');
+          });
+        }
+      }
+    }
+
+    return result(
+      '',
+      exitCode: 1,
+      stderr: 'unexpected tea args: ${arguments.join(' ')}\n',
+    );
+  };
+}
+
+bool _matches(List<String> arguments, int index, String value) =>
+    arguments.length > index && arguments[index] == value;
+
+String? _valueArg(List<String> arguments, String prefix) {
+  for (final argument in arguments) {
+    if (argument.startsWith(prefix)) {
+      return argument.substring(prefix.length);
     }
   }
-
-  buffer
-    ..writeln(r'''echo "unexpected tea args: $*" >&2''')
-    ..writeln('exit 1');
-
-  await teaScript.writeAsString(buffer.toString());
-  await makeScriptExecutable(teaScript);
+  return null;
 }
diff --git a/test/support/script_utils.dart b/test/support/script_utils.dart
index 5630dd3..c2e7223 100644
--- a/test/support/script_utils.dart
+++ b/test/support/script_utils.dart
@@ -1,5 +1,119 @@
+import 'dart:async';
 import 'dart:io';
 
+import 'package:code_work_spawner/src/core/process_launcher.dart';
+import 'package:mocktail/mocktail.dart';
+
+typedef FakeCommandHandler =
+    Future<ProcessResult> Function(List<String> arguments, {Duration? timeout});
+
+typedef FakeStartedCommandHandler =
+    Future<StartedExternalCommand> Function(List<String> arguments);
+
+final Map<String, FakeCommandHandler> fakeCommandHandlers = {};
+final Map<String, FakeStartedCommandHandler> fakeStartedCommandHandlers = {};
+
+class MockExternalCommandExecutor extends Mock
+    implements ExternalCommandExecutor {}
+
+ExternalCommandExecutor fakeExternalCommandExecutor() {
+  _registerMocktailFallbackValues();
+  final executor = MockExternalCommandExecutor();
+  when(
+    () => executor.run(
+      any(),
+      any<List<String>>(),
+      workingDirectory: any(named: 'workingDirectory'),
+      environment: any(named: 'environment'),
+      includeParentEnvironment: any(named: 'includeParentEnvironment'),
+      timeout: any(named: 'timeout'),
+    ),
+  ).thenAnswer((invocation) {
+    final command = invocation.positionalArguments[0] as String;
+    final arguments = invocation.positionalArguments[1] as List<String>;
+    final timeout = invocation.namedArguments[#timeout] as Duration?;
+    final handler = fakeCommandHandlers[command];
+    if (handler == null) {
+      throw StateError('No fake command registered for $command.');
+    }
+    return handler(arguments, timeout: timeout);
+  });
+  when(
+    () => executor.start(
+      any(),
+      any<List<String>>(),
+      workingDirectory: any(named: 'workingDirectory'),
+      environment: any(named: 'environment'),
+      includeParentEnvironment: any(named: 'includeParentEnvironment'),
+      runInShell: any(named: 'runInShell'),
+      mode: any(named: 'mode'),
+    ),
+  ).thenAnswer((invocation) {
+    final command = invocation.positionalArguments[0] as String;
+    final arguments = invocation.positionalArguments[1] as List<String>;
+    final handler = fakeStartedCommandHandlers[command];
+    if (handler == null) {
+      throw StateError('No fake started command registered for $command.');
+    }
+    return handler(arguments);
+  });
+  return executor;
+}
+
+class FakeStartedExternalCommand implements StartedExternalCommand {
+  final StreamController<List<int>> _stdoutController = StreamController();
+  final StreamController<List<int>> _stderrController = StreamController();
+  final Completer<int> _exitCodeCompleter = Completer<int>();
+
+  @override
+  Stream<List<int>> get stdout => _stdoutController.stream;
+
+  @override
+  Stream<List<int>> get stderr => _stderrController.stream;
+
+  @override
+  Future<int> get exitCode => _exitCodeCompleter.future;
+
+  void addStdout(String text) {
+    if (!_stdoutController.isClosed) {
+      _stdoutController.add(systemEncoding.encode(text));
+    }
+  }
+
+  void addStderr(String text) {
+    if (!_stderrController.isClosed) {
+      _stderrController.add(systemEncoding.encode(text));
+    }
+  }
+
+  void complete([int exitCode = 0]) {
+    if (!_exitCodeCompleter.isCompleted) {
+      _exitCodeCompleter.complete(exitCode);
+    }
+    _stdoutController.close();
+    _stderrController.close();
+  }
+
+  @override
+  bool kill([ProcessSignal signal = ProcessSignal.sigterm]) {
+    complete();
+    return true;
+  }
+}
+
+bool _fallbackValuesRegistered = false;
+
+void _registerMocktailFallbackValues() {
+  if (_fallbackValuesRegistered) {
+    return;
+  }
+  _fallbackValuesRegistered = true;
+  registerFallbackValue(<String>[]);
+  registerFallbackValue(<String, String>{});
+  registerFallbackValue(Duration.zero);
+  registerFallbackValue(ProcessStartMode.normal);
+}
+
 Future<void> makeScriptExecutable(File script) async {
   if (Platform.isWindows) {
     return;
@@ -15,35 +129,3 @@ Future<void> makeScriptExecutable(File script) async {
     );
   }
 }
-
-String bashScriptPath(String hostPath) {
-  if (!Platform.isWindows) {
-    return hostPath;
-  }
-
-  final normalized = hostPath.replaceAll('\\', '/');
-  final drivePrefixMatch = RegExp(r'^([A-Za-z]):/(.*)$').firstMatch(normalized);
-  if (drivePrefixMatch == null) {
-    return normalized;
-  }
-
-  final driveLetter = drivePrefixMatch.group(1)!.toLowerCase();
-  final rest = drivePrefixMatch.group(2)!;
-  return '/mnt/$driveLetter/$rest';
-}
-
-String hostPathFromScript(String scriptPath) {
-  if (!Platform.isWindows) {
-    return scriptPath;
-  }
-
-  final trimmed = scriptPath.trim();
-  final mntPathMatch = RegExp(r'^/mnt/([a-zA-Z])/(.*)$').firstMatch(trimmed);
-  if (mntPathMatch == null) {
-    return trimmed;
-  }
-
-  final driveLetter = mntPathMatch.group(1)!.toUpperCase();
-  final rest = mntPathMatch.group(2)!.replaceAll('/', '\\');
-  return '$driveLetter:\\$rest';
-}
diff --git a/test/workspace/worktree_test.dart b/test/workspace/worktree_test.dart
index b4ab2af..88d9b1c 100644
--- a/test/workspace/worktree_test.dart
+++ b/test/workspace/worktree_test.dart
@@ -76,15 +76,16 @@ void registerIssueAssistantAppRunOnceWorktreeTests() {
         final responderScript = File(
           p.join(sandbox.path, 'responder-capture.sh'),
         );
-        await responderScript.writeAsString('''#!/usr/bin/env bash
-set -euo pipefail
-pwd > "${bashScriptPath(cwdCapture.path)}"
-cat > "${bashScriptPath(stdinCapture.path)}"
-cat <<'JSON'
-{"decision":"no_reply","mode":"planning","summary":"captured mention context"}
-JSON
-''');
-        await makeScriptExecutable(responderScript);
+        await writeCapturingResponderScript(
+          responderScript,
+          {
+            'decision': 'no_reply',
+            'mode': 'planning',
+            'summary': 'captured mention context',
+          },
+          cwdCapture: cwdCapture,
+          stdinCapture: stdinCapture,
+        );
 
         // And an orchestrator-style config pointing to the fake repo and responder.
         final configFile = File(
@@ -110,6 +111,8 @@ projects:
           config: await AppConfig.load(configFile.path),
           databasePath: p.join(sandbox.path, 'state.sqlite3'),
           ghCommand: ghScript.path,
+          responderRunner: fakeResponderRunner(),
+          commandExecutor: fakeExternalCommandExecutor(),
         );
 
         // When the app processes one polling cycle.
@@ -117,7 +120,7 @@ projects:
         await app.close();
 
         // Then the responder runs from an ephemeral worktree instead of the source checkout.
-        final capturedCwd = hostPathFromScript(await cwdCapture.readAsString());
+        final capturedCwd = await cwdCapture.readAsString();
         expect(
           p.normalize(capturedCwd.trim()),
           isNot(p.normalize(repoDir.path)),
@@ -201,15 +204,12 @@ projects:
       final responderScript = File(
         p.join(sandbox.path, 'planning-responder.sh'),
       );
-      await responderScript.writeAsString('''#!/usr/bin/env bash
-set -euo pipefail
-pwd > "${bashScriptPath(cwdCapture.path)}"
-cat >/dev/null
-cat <<'JSON'
-{"decision":"reply","mode":"planning","markdown":"planning reply","summary":"used project path"}
-JSON
-''');
-      await makeScriptExecutable(responderScript);
+      await writeCapturingResponderScript(responderScript, {
+        'decision': 'reply',
+        'mode': 'planning',
+        'markdown': 'planning reply',
+        'summary': 'used project path',
+      }, cwdCapture: cwdCapture);
 
       // And an orchestrator-style config pointing to the fake repo and responder.
       final configFile = File(p.join(sandbox.path, 'agent-orchestrator.yaml'));
@@ -234,6 +234,8 @@ projects:
         config: await AppConfig.load(configFile.path),
         databasePath: p.join(sandbox.path, 'state.sqlite3'),
         ghCommand: ghScript.path,
+        responderRunner: fakeResponderRunner(),
+        commandExecutor: fakeExternalCommandExecutor(),
       );
 
       // When the app processes one polling cycle.
@@ -241,7 +243,7 @@ projects:
       await app.close();
 
       // Then the responder runs from an ephemeral worktree instead of the source checkout.
-      final capturedCwd = hostPathFromScript(await cwdCapture.readAsString());
+      final capturedCwd = await cwdCapture.readAsString();
       expect(p.normalize(capturedCwd.trim()), isNot(p.normalize(repoDir.path)));
       expect(
         p.isWithin(worktreeRoot.path, p.normalize(capturedCwd.trim())),
@@ -331,6 +333,8 @@ projects:
         config: await AppConfig.load(configFile.path),
         databasePath: p.join(sandbox.path, 'state.sqlite3'),
         ghCommand: ghScript.path,
+        responderRunner: fakeResponderRunner(),
+        commandExecutor: fakeExternalCommandExecutor(),
       );
 
       // When the app processes one polling cycle.
diff --git a/tool/process_mode_probe.dart b/tool/process_mode_probe.dart
index 4279ac1..aa935cf 100644
--- a/tool/process_mode_probe.dart
+++ b/tool/process_mode_probe.dart
@@ -68,7 +68,6 @@ Future<void> main(List<String> arguments) async {
       'executable': resolved.executable,
       'arguments': resolved.arguments,
       'run_in_shell': resolved.runInShell,
-      'uses_bash_shim': resolved.usesBashShim,
     },
     'results': <Object?>[],
   };