diff --git a/pkg/dds/CHANGELOG.md b/pkg/dds/CHANGELOG.md
index 32cc8aab7b6..fd0e01d0313 100644
--- a/pkg/dds/CHANGELOG.md
+++ b/pkg/dds/CHANGELOG.md
@@ -1,6 +1,7 @@
 # 5.2.0-wip
 
 - [DAP] `Stopped(reason: 'entry')` events will no longer be lost if an isolate has not yet reached the `PauseStart` state when connecting to the VM.
+- **Breaking change:** [DAP] Support for the custom `supportsDartUris` client capability and `dart-macro+file:///` mappings that supported the Dart macros experiment have been removed.
 
 # 5.1.0
 - Update to version 2.1 of the DDS protocol.
diff --git a/pkg/dds/lib/src/dap/adapters/dart.dart b/pkg/dds/lib/src/dap/adapters/dart.dart
index 2a7b2ca0d31..6be98008074 100644
--- a/pkg/dds/lib/src/dap/adapters/dart.dart
+++ b/pkg/dds/lib/src/dap/adapters/dart.dart
@@ -1240,7 +1240,7 @@ abstract class DartDebugAdapter<TL extends LaunchRequestArguments,
 
     // Ensure that we stop watching for a VM Service info file if we are using
     // these utils.
-    if (this case VmServiceInfoFileUtils vmServiceUtils) {
+    if (this case final VmServiceInfoFileUtils vmServiceUtils) {
       vmServiceUtils.stopWaitingForVmServiceInfoFile();
     }
 
@@ -1319,32 +1319,29 @@ abstract class DartDebugAdapter<TL extends LaunchRequestArguments,
       return false;
     }
 
-    final packageFileLikeUri = await thread.resolveUriToPackageLibPath(uri);
-    if (packageFileLikeUri == null) {
+    final packageFileUri = await thread.resolveUriToPackageLibPath(uri);
+    if (packageFileUri == null) {
       return false;
     }
 
-    return !isInUserProject(packageFileLikeUri);
+    return !isInUserProject(packageFileUri);
   }
 
-  /// Checks whether [uri] is inside the users project. This is used to support
-  /// debugging "Just My Code" (via [isExternalPackageLibrary]) and also for
-  /// stack trace highlighting, where non-user code will be faded.
+  /// Checks whether [targetUri] is inside the users project. This is used to
+  /// support debugging "Just My Code" (via [isExternalPackageLibrary]) and also
+  /// for stack trace highlighting, where non-user code will be faded.
   bool isInUserProject(Uri targetUri) {
-    if (!isSupportedFileScheme(targetUri)) {
+    if (!targetUri.isScheme('file')) {
       return false;
     }
 
-    // We could already be 'file', or we could be another supported file scheme
-    // like dart-macro+file, but we can only call toFilePath() on a file URI
-    // and we use the equivalent path to decide if this is within the workspace.
-    var targetPath = targetUri.replace(scheme: 'file').toFilePath();
-
-    // Always compare paths case-insensitively to avoid any issues where APIs
-    // may have returned different casing (e.g. Windows drive letters). It's
-    // almost certain a user wouldn't have a "local" package and an "external"
-    // package with paths differing only be case.
-    targetPath = targetPath.toLowerCase();
+    final targetPath = targetUri
+        .toFilePath()
+        // Always compare paths case-insensitively to avoid any issues where APIs
+        // may have returned different casing (e.g. Windows drive letters). It's
+        // almost certain a user wouldn't have a "local" package and an "external"
+        // package with paths differing only be case.
+        .toLowerCase();
 
     return projectPaths
         .map((projectPath) => projectPath.toLowerCase())
@@ -1602,9 +1599,7 @@ abstract class DartDebugAdapter<TL extends LaunchRequestArguments,
 
     final path = args.source.path;
     final name = args.source.name;
-    final uri = path != null
-        ? normalizeUri(fromClientPathOrUri(path)).toString()
-        : name!;
+    final uri = path != null ? normalizeUri(Uri.file(path)).toString() : name!;
 
     // Use a completer to track when the response is sent, so any events related
     // to these breakpoints are not sent before the client has the IDs.
@@ -1681,7 +1676,7 @@ abstract class DartDebugAdapter<TL extends LaunchRequestArguments,
   }
 
   /// Converts a URI in the form org-dartlang-sdk:///sdk/lib/collection/hash_set.dart
-  /// to a local file-like URI based on the current SDK.
+  /// to a local file URI based on the current SDK.
   Uri? convertOrgDartlangSdkToPath(Uri uri) {
     // org-dartlang-sdk URIs can be in multiple forms:
     //
@@ -2340,14 +2335,14 @@ abstract class DartDebugAdapter<TL extends LaunchRequestArguments,
     final framePaths = await Future.wait(frameLocations.map((frame) async {
       final uri = frame?.uri;
       if (uri == null) return null;
-      if (isSupportedFileScheme(uri)) {
+      if (uri.isScheme('file')) {
         return (uri: uri, isUserCode: isInUserProject(uri));
       }
       if (thread == null || !isResolvableUri(uri)) return null;
       try {
-        final fileLikeUri = await thread.resolveUriToPath(uri);
-        return fileLikeUri != null
-            ? (uri: fileLikeUri, isUserCode: isInUserProject(fileLikeUri))
+        final fileUri = await thread.resolveUriToPath(uri);
+        return fileUri != null
+            ? (uri: fileUri, isUserCode: isInUserProject(fileUri))
             : null;
       } catch (e, s) {
         // Swallow errors for the same reason noted above.
@@ -2363,8 +2358,8 @@ abstract class DartDebugAdapter<TL extends LaunchRequestArguments,
       final uri = frameLocation?.uri;
       final framePathInfo = framePaths[i];
 
-      // A file-like URI ('file://' or 'dart-macro+file://').
-      final fileLikeUri = framePathInfo?.uri;
+      // A file URI.
+      final fileUri = framePathInfo?.uri;
 
       // Default to true so that if we don't know whether this is user-project
       // then we leave the formatting as-is and don't fade anything out.
@@ -2372,7 +2367,7 @@ abstract class DartDebugAdapter<TL extends LaunchRequestArguments,
 
       // For the name, we usually use the package URI, but if we only had a file
       // URI to begin with, try to make it relative to cwd so it's not so long.
-      final name = uri != null && fileLikeUri != null
+      final name = uri != null && fileUri != null
           ? (uri.isScheme('file')
               ? _converter.convertToRelativePath(uri.toFilePath())
               : uri.toString())
@@ -2397,8 +2392,7 @@ abstract class DartDebugAdapter<TL extends LaunchRequestArguments,
         continue;
       }
 
-      final clientPath =
-          fileLikeUri != null ? toClientPathOrUri(fileLikeUri) : null;
+      final clientPath = fileUri != null ? toClientPathOrUri(fileUri) : null;
       events.add(
         OutputEventBody(
           category: category,
@@ -2645,19 +2639,19 @@ abstract class DartDebugAdapter<TL extends LaunchRequestArguments,
       return;
     }
 
-    // Doesn't need resolving if already file-like.
-    if (isSupportedFileScheme(uri)) {
+    // Doesn't need resolving if already file.
+    if (uri.isScheme('file')) {
       return;
     }
 
-    final fileLikeUri = await thread.resolveUriToPath(uri);
-    if (fileLikeUri != null) {
+    final fileUri = await thread.resolveUriToPath(uri);
+    if (fileUri != null) {
       // Convert:
       //   uri -> resolvedUri
       //   fileUri -> resolvedFileUri
       final resolvedFieldName =
           'resolved${field.substring(0, 1).toUpperCase()}${field.substring(1)}';
-      data[resolvedFieldName] = fileLikeUri.toString();
+      data[resolvedFieldName] = fileUri.toString();
     }
   }
 
@@ -2888,47 +2882,18 @@ abstract class DartDebugAdapter<TL extends LaunchRequestArguments,
     }
   }
 
-  /// Whether the current client supports URIs in place of file paths, including
-  /// file-like URIs that are not the 'file' scheme (such as 'dart-macro+file').
-  bool get clientSupportsUri => _initializeArgs?.supportsDartUris ?? false;
-
-  /// Returns whether [uri] is a file-like URI scheme that is supported by the
-  /// client.
-  ///
-  /// Returning `true` here does not guarantee that the client supports URIs,
-  /// the caller should also check [clientSupportsUri].
-  bool isSupportedFileScheme(Uri uri) {
-    return uri.isScheme('file') ||
-        // Handle all file-like schemes that end '+file' like
-        // 'dart-macro+file://'.
-        (clientSupportsUri && uri.scheme.endsWith('+file'));
-  }
-
   /// Converts a URI into a form that can be used by the client.
   ///
-  /// If the client supports URIs (like VS Code), it will be returned unchanged
-  /// but otherwise it will be the `toFilePath()` equivalent if a 'file://' URI
-  /// and otherwise `null`.
+  /// Returns `null` if the uri is not a supported file scheme.
   String? toClientPathOrUri(Uri? uri) {
     if (uri == null) {
       return null;
-    } else if (clientSupportsUri) {
-      return uri.toString();
     } else if (uri.isScheme('file')) {
       return uri.toFilePath();
     } else {
       return null;
     }
   }
-
-  /// Converts a String used by the client as a path/URI into a [Uri].
-  Uri fromClientPathOrUri(String filePathOrUriString) {
-    var uri = Uri.tryParse(filePathOrUriString);
-    if (uri == null || !isSupportedFileScheme(uri)) {
-      uri = Uri.file(filePathOrUriString);
-    }
-    return uri;
-  }
 }
 
 /// An implementation of [LaunchRequestArguments] that includes all fields used
diff --git a/pkg/dds/lib/src/dap/adapters/mixins.dart b/pkg/dds/lib/src/dap/adapters/mixins.dart
index 1aa1c2ce6b1..7982b27cc49 100644
--- a/pkg/dds/lib/src/dap/adapters/mixins.dart
+++ b/pkg/dds/lib/src/dap/adapters/mixins.dart
@@ -260,13 +260,6 @@ mixin FileUtils {
       final filePath = uri.toFilePath();
       final normalizedPath = normalizePath(filePath);
       return Uri.file(normalizedPath);
-    } else if (uri.scheme.endsWith('+file')) {
-      // For virtual file schemes, we need to replace the scheme to use
-      // toFilePath() so we can normalise the path, then convert back.
-      final originalScheme = uri.scheme;
-      final filePath = uri.replace(scheme: 'file').toFilePath();
-      final normalizedPath = normalizePath(filePath);
-      return Uri.file(normalizedPath).replace(scheme: originalScheme);
     } else {
       return uri;
     }
diff --git a/pkg/dds/lib/src/dap/isolate_manager.dart b/pkg/dds/lib/src/dap/isolate_manager.dart
index aad66813135..12fc105d61d 100644
--- a/pkg/dds/lib/src/dap/isolate_manager.dart
+++ b/pkg/dds/lib/src/dap/isolate_manager.dart
@@ -922,7 +922,7 @@ class IsolateManager {
     var userMessage = error is vm.RPCError
         ? error.details ?? error.toString()
         : error.toString();
-    var terseMessageMatch =
+    final terseMessageMatch =
         _terseBreakpointFailureRegex.firstMatch(userMessage);
     if (terseMessageMatch != null) {
       userMessage = terseMessageMatch.group(1) ?? userMessage;
@@ -1298,13 +1298,13 @@ class ThreadInfo with FileUtils {
   /// tokenPos) can share the same response.
   final _scripts = <String, Future<vm.Script>>{};
 
-  /// A cache of requests (Futures) to resolve URIs to their file-like URIs.
+  /// A cache of requests (Futures) to resolve URIs to their file URIs.
   ///
   /// Used so that multiple requests that require them (for example looking up
   /// locations for stack frames from tokenPos) can share the same response.
   ///
   /// Keys are URIs in string form.
-  /// Values are file-like URIs (file: or similar, such as dart-macro+file:).
+  /// Values are file URIs.
   final _resolvedPaths = <String, Future<Uri?>>{};
 
   /// Whether this isolate has an in-flight user-initiated resume request that
@@ -1370,7 +1370,7 @@ class ThreadInfo with FileUtils {
   ///
   /// sdk-path/lib/core/print.dart -> dart:core/print.dart
   /// c:\foo\bar -> package:foo/bar
-  /// dart-macro+file:///c:/foo/bar -> dart-macro+package:foo/bar
+  /// file:///c:/foo/bar -> package:foo/bar
   ///
   /// This is required so that when the user sets a breakpoint in an SDK source
   /// (which they may have navigated to via the Analysis Server) we generate a
@@ -1417,7 +1417,7 @@ class ThreadInfo with FileUtils {
     }
   }
 
-  /// Batch resolves source URIs from the VM to a file-like URI for the package
+  /// Batch resolves source URIs from the VM to a file URI for the package
   /// lib folder.
   ///
   /// This method is more performant than repeatedly calling
@@ -1437,7 +1437,7 @@ class ThreadInfo with FileUtils {
         .toList();
   }
 
-  /// Batch resolves source URIs from the VM to a file-like URI.
+  /// Batch resolves source URIs from the VM to a file URI.
   ///
   /// This method is more performant than repeatedly calling [resolveUriToPath]
   /// because it resolves multiple URIs in a single request to the VM.
@@ -1513,7 +1513,7 @@ class ThreadInfo with FileUtils {
     // because they were either filtered out of [requiredUris] because they were
     // already there, or we then populated completers for them above.
     final futures = uris.map((uri) async {
-      if (_manager._adapter.isSupportedFileScheme(uri)) {
+      if (uri.isScheme('file')) {
         return uri;
       } else {
         return await _resolvedPaths[uri.toString()];
@@ -1562,11 +1562,10 @@ class ThreadInfo with FileUtils {
   /// would not be changed.
   final _libraryIsDebuggableById = <String, bool>{};
 
-  /// Resolves a source URI to a file-like URI for the lib folder of its
+  /// Resolves a source URI to a file URI for the lib folder of its
   /// package.
   ///
   /// package:foo/a/b/c/d.dart -> file:///code/packages/foo/lib
-  /// dart-macro+package:foo/a/b/c/d.dart -> dart-macro+file:///code/packages/foo/lib
   ///
   /// This method is an optimisation over calling [resolveUriToPath] where only
   /// the package root is required (for example when determining whether a
@@ -1578,7 +1577,7 @@ class ThreadInfo with FileUtils {
     return result.first;
   }
 
-  /// Resolves a source URI from the VM to a file-like URI.
+  /// Resolves a source URI from the VM to a file URI.
   ///
   /// dart:core/print.dart -> sdk-path/lib/core/print.dart
   ///
@@ -1596,8 +1595,6 @@ class ThreadInfo with FileUtils {
   int storeData(Object data) => _manager.storeData(this, data);
 
   Uri? _convertPathToGoogle3Uri(Uri input) {
-    // TODO(dantup): Do we need to handle non-file here? Eg. can we have
-    //  dart-macro+file:/// for a google3 path?
     if (!input.isScheme('file')) {
       return null;
     }
@@ -1605,8 +1602,8 @@ class ThreadInfo with FileUtils {
 
     const search = '/google3/';
     if (inputPath.startsWith('/google') && inputPath.contains(search)) {
-      var idx = inputPath.indexOf(search);
-      var remainingPath = inputPath.substring(idx + search.length);
+      final idx = inputPath.indexOf(search);
+      final remainingPath = inputPath.substring(idx + search.length);
       return Uri(
         scheme: 'google3',
         host: '',
@@ -1617,17 +1614,17 @@ class ThreadInfo with FileUtils {
     return null;
   }
 
-  /// Converts a VM-returned URI to a file-like URI, taking org-dartlang-sdk
+  /// Converts a VM-returned URI to a file URI, taking org-dartlang-sdk
   /// schemes into account.
   ///
-  /// Supports file-like URIs and org-dartlang-sdk:// URIs.
+  /// Supports file URIs and org-dartlang-sdk:// URIs.
   Uri? _convertUriToFilePath(Uri? input) {
     if (input == null) {
       return null;
-    } else if (_manager._adapter.isSupportedFileScheme(input)) {
+    } else if (input.isScheme('file')) {
       return input;
     } else {
-      // TODO(dantup): UriConverter should be upgraded to use file-like URIs
+      // TODO(dantup): UriConverter should be upgraded to use file URIs
       //  instead of paths, but that might be breaking because it's used
       //  outside of this package?
       final uriConverter = _manager._adapter.uriConverter();
@@ -1644,8 +1641,8 @@ class ThreadInfo with FileUtils {
   ///
   /// [uri] should be the equivalent package: URI and is used to know how many
   /// segments to remove from the file path to get to the lib folder.
-  Uri? _trimPathToLibFolder(Uri? fileLikeUri, Uri uri) {
-    if (fileLikeUri == null) {
+  Uri? _trimPathToLibFolder(Uri? fileUri, Uri uri) {
+    if (fileUri == null) {
       return null;
     }
 
@@ -1657,14 +1654,14 @@ class ThreadInfo with FileUtils {
     // least as many segments as the path of the URI.
     assert(uri.pathSegments.length > libraryPathSegments);
     if (uri.pathSegments.length <= libraryPathSegments) {
-      return fileLikeUri;
+      return fileUri;
     }
 
     // Strip off the correct number of segments to the resulting path points
     // to the root of the package:/ URI.
-    final keepSegments = fileLikeUri.pathSegments.length - libraryPathSegments;
-    return fileLikeUri.replace(
-        pathSegments: fileLikeUri.pathSegments.sublist(0, keepSegments));
+    final keepSegments = fileUri.pathSegments.length - libraryPathSegments;
+    return fileUri.replace(
+        pathSegments: fileUri.pathSegments.sublist(0, keepSegments));
   }
 
   /// Clears all temporary stored for this thread. This includes:
diff --git a/pkg/dds/lib/src/dap/protocol_converter.dart b/pkg/dds/lib/src/dap/protocol_converter.dart
index b3aa18cc8af..01994bac0eb 100644
--- a/pkg/dds/lib/src/dap/protocol_converter.dart
+++ b/pkg/dds/lib/src/dap/protocol_converter.dart
@@ -609,8 +609,7 @@ class ProtocolConverter {
     final uriIsPackage = uri?.isScheme('package') ?? false;
     final sourcePathUri =
         uri != null ? await thread.resolveUriToPath(uri) : null;
-    var canShowSource =
-        sourcePathUri != null && _adapter.isSupportedFileScheme(sourcePathUri);
+    var canShowSource = sourcePathUri != null && sourcePathUri.isScheme('file');
 
     // If we don't have a local source file but the source is a "dart:" uri we
     // might still be able to download the source from the VM.
@@ -639,7 +638,7 @@ class ProtocolConverter {
     }
 
     // LSP uses 0 for unknown lines.
-    var (line, col) = lineCol ?? (0, 0);
+    final (line, col) = lineCol ?? (0, 0);
 
     // If a source would be considered not-debuggable (for example it's in the
     // SDK and debugSdkLibraries=false) then we should also mark it as
diff --git a/pkg/dds/lib/src/dap/protocol_stream_transformers.dart b/pkg/dds/lib/src/dap/protocol_stream_transformers.dart
index 774061f75b8..8bb133b2239 100644
--- a/pkg/dds/lib/src/dap/protocol_stream_transformers.dart
+++ b/pkg/dds/lib/src/dap/protocol_stream_transformers.dart
@@ -78,7 +78,7 @@ class PacketTransformer extends StreamTransformerBase<List<int>, String> {
 
   /// Whether [buffer] ends in '\r\n\r\n'.
   static bool _endsWithCrLfCrLf(List<int> buffer) {
-    var l = buffer.length;
+    final l = buffer.length;
     return l > 4 &&
         buffer[l - 1] == 10 &&
         buffer[l - 2] == 13 &&
diff --git a/pkg/dds/lib/src/dap/utils.dart b/pkg/dds/lib/src/dap/utils.dart
index 09faa99dc58..1d8c554aeac 100644
--- a/pkg/dds/lib/src/dap/utils.dart
+++ b/pkg/dds/lib/src/dap/utils.dart
@@ -9,12 +9,10 @@ import 'package:vm_service/vm_service.dart' as vm;
 
 import '../rpc_error_codes.dart';
 
-/// Returns whether this URI is something that can be resolved to a file-like
+/// Returns whether this URI is something that can be resolved to a file
 /// URI via the VM Service.
 bool isResolvableUri(Uri uri) {
   return !uri.isScheme('file') &&
-      // Custom-scheme versions of file, like `dart-macro+file://`
-      !uri.scheme.endsWith('+file') &&
       !uri.isScheme('http') &&
       !uri.isScheme('https') &&
       // Parsed stack frames may have URIs with no scheme and the text
@@ -62,9 +60,7 @@ bool _isDartUri(Uri uri) {
   // Only accept package: and file: URIs if they end with .dart.
   // - package:foo/foo.dart
   // - file:///c:/foo/bar.dart
-  if (uri.isScheme('package') ||
-      uri.isScheme('file') ||
-      uri.scheme.endsWith('+file')) {
+  if (uri.isScheme('package') || uri.isScheme('file')) {
     return uri.path.endsWith('.dart');
   }
 
@@ -101,16 +97,16 @@ final _stackFrameLocationPattern =
 /// It should not be assumed that if a value is returned that the input
 /// was necessarily a stack frame.
 StackFrameLocation? _parseStackFrame(String input) {
-  var match = _stackFrameLocationPattern.firstMatch(input);
+  final match = _stackFrameLocationPattern.firstMatch(input);
   if (match == null) return null;
 
-  var uriMatch = match.group(1);
-  var lineMatch = match.group(2);
-  var colMatch = match.group(3);
+  final uriMatch = match.group(1);
+  final lineMatch = match.group(2);
+  final colMatch = match.group(3);
 
   var uri = uriMatch != null ? Uri.tryParse(uriMatch) : null;
-  var line = lineMatch != null ? int.tryParse(lineMatch) : null;
-  var col = colMatch != null ? int.tryParse(colMatch) : null;
+  final line = lineMatch != null ? int.tryParse(lineMatch) : null;
+  final col = colMatch != null ? int.tryParse(colMatch) : null;
 
   if (uriMatch == null || uri == null) {
     return null;
@@ -118,7 +114,7 @@ StackFrameLocation? _parseStackFrame(String input) {
 
   // If the URI has no scheme, assume a relative path from Directory.current.
   if (!uri.hasScheme && path.isRelative(uriMatch)) {
-    var currentDirectoryPath = Directory.current.path;
+    final currentDirectoryPath = Directory.current.path;
     if (currentDirectoryPath.isNotEmpty) {
       uri = Uri.file(path.join(currentDirectoryPath, uriMatch));
     }
diff --git a/pkg/dds/test/dap/integration/debug_breakpoints_test.dart b/pkg/dds/test/dap/integration/debug_breakpoints_test.dart
index 365e60d9d5e..6cfa47563fb 100644
--- a/pkg/dds/test/dap/integration/debug_breakpoints_test.dart
+++ b/pkg/dds/test/dap/integration/debug_breakpoints_test.dart
@@ -20,8 +20,7 @@ main() {
   tearDown(() => dap.tearDown());
 
   group('debug mode breakpoints', () {
-    testWithUriConfigurations(() => dap, 'stops at a line breakpoint',
-        () async {
+    test('stops at a line breakpoint', () async {
       final client = dap.client;
       final testFile = dap.createTestFile(simpleBreakpointProgram);
       final breakpointLine = lineWith(testFile, breakpointMarker);
@@ -29,8 +28,7 @@ main() {
       await client.hitBreakpoint(testFile, breakpointLine);
     });
 
-    testWithUriConfigurations(() => dap, 'resolves modified breakpoints',
-        () async {
+    test('resolves modified breakpoints', () async {
       final client = dap.client;
       final testFile = dap.createTestFile(simpleMultiBreakpointProgram);
       final breakpointLine = lineWith(testFile, breakpointMarker);
@@ -75,8 +73,7 @@ main() {
       expect(resolvedBreakpoints, addedBreakpoints);
     });
 
-    testWithUriConfigurations(
-        () => dap, 'provides reason for failed breakpoints', () async {
+    test('provides reason for failed breakpoints', () async {
       final client = dap.client;
       final testFile = dap.createTestFile(debuggerPauseProgram);
       final invalidBreakpointLine = 9999;
@@ -96,8 +93,8 @@ main() {
       });
 
       // Set the breakpoint and also collect the original reason.
-      var bps = await client.setBreakpoint(testFile, invalidBreakpointLine);
-      var bp = bps.breakpoints.single;
+      final bps = await client.setBreakpoint(testFile, invalidBreakpointLine);
+      final bp = bps.breakpoints.single;
       breakpointReasons.add('${bp.reason}: ${bp.message}');
 
       // Wait up to a few seconds for the change events to come through to
@@ -118,9 +115,7 @@ main() {
       await breakpointChangedSubscription.cancel();
     });
 
-    testWithUriConfigurations(
-        () => dap, 'provides reason for not-yet-resolved breakpoints',
-        () async {
+    test('provides reason for not-yet-resolved breakpoints', () async {
       final client = dap.client;
       final testFile = dap.createTestFile(debuggerPauseProgram);
       final breakpointLine = lineWith(testFile, breakpointMarker);
@@ -132,7 +127,7 @@ main() {
       ], eagerError: true);
 
       // Set a breakpoint and verify the result.
-      var bps = await client.setBreakpoint(testFile, breakpointLine);
+      final bps = await client.setBreakpoint(testFile, breakpointLine);
       expect(bps.breakpoints.single.reason, 'pending');
       expect(bps.breakpoints.single.message,
           'Breakpoint has not yet been resolved');
diff --git a/pkg/dds/test/dap/integration/debug_exceptions_test.dart b/pkg/dds/test/dap/integration/debug_exceptions_test.dart
index d6ab684e0e1..da2c649ae8b 100644
--- a/pkg/dds/test/dap/integration/debug_exceptions_test.dart
+++ b/pkg/dds/test/dap/integration/debug_exceptions_test.dart
@@ -42,9 +42,7 @@ main() {
       ]);
     });
 
-    testWithUriConfigurations(
-        () => dap, 'pauses on uncaught exceptions when mode=Unhandled',
-        () async {
+    test('pauses on uncaught exceptions when mode=Unhandled', () async {
       final client = dap.client;
       final testFile = dap.createTestFile(simpleThrowingProgram);
 
diff --git a/pkg/dds/test/dap/integration/debug_logging_test.dart b/pkg/dds/test/dap/integration/debug_logging_test.dart
index 7643689eca9..cfdea3e05fa 100644
--- a/pkg/dds/test/dap/integration/debug_logging_test.dart
+++ b/pkg/dds/test/dap/integration/debug_logging_test.dart
@@ -97,7 +97,7 @@ void main(List<String> args) async {
 }
     ''');
 
-      var outputEvents = await dap.client.collectOutput(file: testFile);
+      final outputEvents = await dap.client.collectOutput(file: testFile);
 
       // Skip the first two lines because it's the VM Service connection info.
       final output = outputEvents.skip(2).map((e) => e.output).join();
diff --git a/pkg/dds/test/dap/integration/debug_stack_test.dart b/pkg/dds/test/dap/integration/debug_stack_test.dart
index fbe67967465..f3548f00384 100644
--- a/pkg/dds/test/dap/integration/debug_stack_test.dart
+++ b/pkg/dds/test/dap/integration/debug_stack_test.dart
@@ -16,8 +16,7 @@ main() {
   tearDown(() => dap.tearDown());
 
   group('debug mode stack trace', () {
-    testWithUriConfigurations(
-        () => dap, 'includes expected names and async boundaries', () async {
+    test('includes expected names and async boundaries', () async {
       final client = dap.client;
       final testFile = dap.createTestFile(simpleAsyncProgram);
       final breakpointLine = lineWith(testFile, breakpointMarker);
diff --git a/pkg/dds/test/dap/integration/test_client.dart b/pkg/dds/test/dap/integration/test_client.dart
index 871752fa1a9..3a8a8da6c8d 100644
--- a/pkg/dds/test/dap/integration/test_client.dart
+++ b/pkg/dds/test/dap/integration/test_client.dart
@@ -11,7 +11,6 @@ import 'package:dap/dap.dart';
 import 'package:dds/src/dap/adapters/dart.dart';
 import 'package:dds/src/dap/logging.dart';
 import 'package:dds/src/dap/protocol_stream.dart';
-import 'package:path/path.dart' as path;
 import 'package:test/test.dart';
 import 'package:vm_service/vm_service.dart' as vm;
 
@@ -34,17 +33,6 @@ class DapTestClient {
   final _eventController = StreamController<Event>.broadcast();
   int _seq = 1;
 
-  /// Whether to advertise support for URIs and expect them in stack traces
-  /// and breakpoint updates from the debug adapter.
-  bool supportUris = false;
-
-  /// Whether to send URIs in breakpoints even for standard file paths.
-  ///
-  /// This is separate from [supportUris] so that we can test when support is
-  /// enabled that the client can still send paths. This is because VS Code will
-  /// send file paths for file:/// documents even though URIs are supported.
-  bool sendFileUris = false;
-
   /// Functions provided by tests to handle requests that may come from the
   /// server (such as `runInTerminal`).
   final _serverRequestHandlers =
@@ -314,7 +302,6 @@ class DapTestClient {
         adapterID: 'test',
         supportsRunInTerminalRequest: supportsRunInTerminalRequest,
         supportsProgressReporting: supportsProgressReporting,
-        supportsDartUris: supportUris,
       )),
       sendRequest(
         SetExceptionBreakpointsArguments(
@@ -607,7 +594,7 @@ class DapTestClient {
   Future<T> _logIfSlow<T>(String name, Future<T> future) {
     // Use a loop to periodically check so that we can exit earlier if
     // the test is being torn down.
-    var endTime = DateTime.now().add(_requestWarningDuration);
+    final endTime = DateTime.now().add(_requestWarningDuration);
     late Timer timer;
     timer = Timer.periodic(Duration(milliseconds: 100), (_) {
       // Shutting down, so just abort.
@@ -760,34 +747,12 @@ extension DapTestClientExtension on DapTestClient {
     return stop;
   }
 
-  /// Converts a file path to a URI to send to the debug adapter if
-  /// [sendFileUris] is `true` and otherwise returns as-is.
-  String toPathOrUri(String filePath) {
-    assert(path.isAbsolute(filePath));
-    return sendFileUris ? Uri.file(filePath).toString() : filePath;
-  }
-
-  /// Converts a string from the debug adapter back to a file path, asserting
-  /// it was a URI if [useUris] is `true`, and not if [useUris] is `false`.
-  String fromPathOrUri(String filePathOrUri) {
-    if (!supportUris) {
-      // Expect an absolute path.
-      assert(path.isAbsolute(filePathOrUri));
-      return filePathOrUri;
-    }
-
-    // Expect a URI with file:/// scheme.
-    final uri = Uri.parse(filePathOrUri);
-    assert(uri.isScheme('file'));
-    return uri.toFilePath();
-  }
-
   /// Sets a breakpoint at [line] in [file].
   Future<SetBreakpointsResponseBody> setBreakpoint(File file, int line,
       {String? condition}) async {
     final response = await sendRequest(
       SetBreakpointsArguments(
-        source: Source(path: toPathOrUri(_normalizeBreakpointPath(file.path))),
+        source: Source(path: _normalizeBreakpointPath(file.path)),
         breakpoints: [SourceBreakpoint(line: line, condition: condition)],
       ),
     );
@@ -802,7 +767,7 @@ extension DapTestClientExtension on DapTestClient {
       File file, List<int> lines) async {
     final response = await sendRequest(
       SetBreakpointsArguments(
-        source: Source(path: toPathOrUri(_normalizeBreakpointPath(file.path))),
+        source: Source(path: _normalizeBreakpointPath(file.path)),
         breakpoints: lines.map((line) => SourceBreakpoint(line: line)).toList(),
       ),
     );
@@ -866,8 +831,7 @@ extension DapTestClientExtension on DapTestClient {
       initialize(),
       sendRequest(
         SetBreakpointsArguments(
-          source:
-              Source(path: toPathOrUri(_normalizeBreakpointPath(file.path))),
+          source: Source(path: _normalizeBreakpointPath(file.path)),
           breakpoints: [
             SourceBreakpoint(
               line: line,
@@ -950,8 +914,7 @@ extension DapTestClientExtension on DapTestClient {
       final frame = result.stackFrames[0];
 
       if (file != null) {
-        expect(fromPathOrUri(frame.source!.path!),
-            equals(uppercaseDriveLetter(file.path)));
+        expect(frame.source!.path!, equals(uppercaseDriveLetter(file.path)));
       }
       if (sourceName != null) {
         expect(frame.source?.name, equals(sourceName));
diff --git a/pkg/dds/test/dap/integration/test_support.dart b/pkg/dds/test/dap/integration/test_support.dart
index e777f47f8ef..7c0c450bbdf 100644
--- a/pkg/dds/test/dap/integration/test_support.dart
+++ b/pkg/dds/test/dap/integration/test_support.dart
@@ -8,7 +8,6 @@ import 'dart:io';
 
 import 'package:dap/dap.dart';
 import 'package:dds/src/dap/logging.dart';
-import 'package:meta/meta.dart';
 import 'package:path/path.dart' as path;
 import 'package:test/test.dart';
 
@@ -320,37 +319,12 @@ environment:
   }
 }
 
-/// A helper to run [testFunc] as a test in various configurations of URI
-/// support.
-///
-/// This should be used to ensure coverage of each configuration where
-/// breakpoints and stack traces are being tested.
-@isTest
-void testWithUriConfigurations(
-  DapTestSession Function() dapFunc,
-  String name,
-  FutureOr<void> Function() testFunc,
-) {
-  for (final (supportUris, sendFileUris) in [
-    (false, false),
-    (true, false),
-    (true, true),
-  ]) {
-    test('$name (supportUris: $supportUris, sendFileUris: $sendFileUris)', () {
-      final client = dapFunc().client;
-      client.supportUris = supportUris;
-      client.sendFileUris = sendFileUris;
-      return testFunc();
-    });
-  }
-}
-
 /// Sets the casing of a drive letter according to [casing].
 String setDriveLetterCasing(String path, DriveLetterCasing? casing) {
   if (!Platform.isWindows || path.isEmpty) {
     return path;
   }
-  var (driveLetter, rest) = (path.substring(0, 1), path.substring(1));
+  final (driveLetter, rest) = (path.substring(0, 1), path.substring(1));
   return switch (casing) {
     DriveLetterCasing.uppercase => driveLetter.toUpperCase() + rest,
     DriveLetterCasing.lowercase => driveLetter.toLowerCase() + rest,
diff --git a/pkg/dds/test/dap/integration/windows_path_casing_test.dart b/pkg/dds/test/dap/integration/windows_path_casing_test.dart
index a84aaeb4dcd..b1d0d69cab8 100644
--- a/pkg/dds/test/dap/integration/windows_path_casing_test.dart
+++ b/pkg/dds/test/dap/integration/windows_path_casing_test.dart
@@ -28,6 +28,9 @@ main() {
                 'breakpoint requests: $breakpointCasing)', () async {
               // Set the correct casing of drive letters for this test.
               if (actualCwdCasing != null) {
+                // TODO(dantup): This setting of Directory.current can cause
+                //  test failures when running multiple tests with `dart test`
+                //  due to concurrency!
                 Directory.current = Directory(
                   setDriveLetterCasing(Directory.current.path, actualCwdCasing),
                 );
diff --git a/pkg/dds/test/dap/utils_test.dart b/pkg/dds/test/dap/utils_test.dart
index f979658b1e6..fa050be43e9 100644
--- a/pkg/dds/test/dap/utils_test.dart
+++ b/pkg/dds/test/dap/utils_test.dart
@@ -39,7 +39,7 @@ main() {
       int? col,
     ]) {
       for (var input in inputs) {
-        var frame = parseDartStackFrame(input);
+        final frame = parseDartStackFrame(input);
         expect(frame, isNotNull, reason: 'Failed to parse "$input"');
         expect(frame!.uri, uri, reason: 'Failed to parse URI from "$input"');
         expect(frame.line, line, reason: 'Failed to parse line from "$input"');
@@ -141,30 +141,6 @@ main() {
       });
     });
 
-    group('Posix dart-macro+file URIs', () {
-      test('without line/col', () {
-        expectFrames(
-          [
-            '#1        A.b (dart-macro+file:///a/b/c/d.dart)',
-            'flutter: #1        A.b (dart-macro+file:///a/b/c/d.dart)',
-          ],
-          Uri.parse('dart-macro+file:///a/b/c/d.dart'),
-        );
-      });
-
-      test('with line/col', () {
-        expectFrames(
-          [
-            '#1        A.b (dart-macro+file:///a/b/c/d.dart:1:2)',
-            'flutter: #1        A.b (dart-macro+file:///a/b/c/d.dart:1:2)',
-          ],
-          Uri.parse('dart-macro+file:///a/b/c/d.dart'),
-          1,
-          2,
-        );
-      });
-    });
-
     group('Posix relative paths', () {
       test('without line/col', () {
         expectFrames(
@@ -227,30 +203,6 @@ main() {
       });
     });
 
-    group('Windows dart-macro+file URIs', () {
-      test('without line/col', () {
-        expectFrames(
-          [
-            '#1        A.b (dart-macro+file:///a:/b/c/d.dart)',
-            'flutter: #1        A.b (dart-macro+file:///a:/b/c/d.dart)',
-          ],
-          Uri.parse('dart-macro+file:///a:/b/c/d.dart'),
-        );
-      });
-
-      test('with line/col', () {
-        expectFrames(
-          [
-            '#1        A.b (dart-macro+file:///a:/b/c/d.dart:1:2)',
-            'flutter: #1        A.b (dart-macro+file:///a:/b/c/d.dart:1:2)',
-          ],
-          Uri.parse('dart-macro+file:///a:/b/c/d.dart'),
-          1,
-          2,
-        );
-      });
-    });
-
     group('Windows relative paths', () {
       test('without line/col', () {
         expectFrames(
diff --git a/third_party/pkg/dap/CHANGELOG.md b/third_party/pkg/dap/CHANGELOG.md
index 4d5cea55d09..2a4e7e90610 100644
--- a/third_party/pkg/dap/CHANGELOG.md
+++ b/third_party/pkg/dap/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 1.5.0-wip
+
+- Removed the `supportsDartUris` flag from `DartInitializeRequestArguments` because it was only required to support the (now removed) Dart macros experiment.
+
 ## 1.4.0
 
 - Updated all generated classes using the latest published version of the DAP spec.
diff --git a/third_party/pkg/dap/lib/src/protocol_special.dart b/third_party/pkg/dap/lib/src/protocol_special.dart
index 70f398d49b6..96e51d4bc4b 100644
--- a/third_party/pkg/dap/lib/src/protocol_special.dart
+++ b/third_party/pkg/dap/lib/src/protocol_special.dart
@@ -58,33 +58,17 @@ abstract class ToJsonable {
 /// A custom version of [InitializeRequestArguments] that adds custom Dart
 /// capabilities not covered by the DAP spec.
 class DartInitializeRequestArguments extends InitializeRequestArguments {
-  /// Whether the client supports URIs in places where we would normally send
-  /// file paths.
-  ///
-  /// This may be replaced by something standard DAP in future
-  /// https://github.com/microsoft/debug-adapter-protocol/issues/444
-  final bool supportsDartUris;
-
   /// A reader for protocol arguments that throws detailed exceptions if
   /// arguments aren't of the correct type.
   static final arg = DebugAdapterArgumentReader('initialize');
 
   DartInitializeRequestArguments({
     required super.adapterID,
-    this.supportsDartUris = false,
     super.supportsRunInTerminalRequest,
     super.supportsProgressReporting,
   });
 
-  DartInitializeRequestArguments.fromMap(super.obj)
-      : supportsDartUris = arg.read<bool?>(obj, 'supportsDartUris') ?? false,
-        super.fromMap();
-
-  @override
-  Map<String, Object?> toJson() => {
-        ...super.toJson(),
-        if (supportsDartUris) 'supportsDartUris': supportsDartUris,
-      };
+  DartInitializeRequestArguments.fromMap(super.obj) : super.fromMap();
 
   static DartInitializeRequestArguments fromJson(Map<String, Object?> obj) =>
       DartInitializeRequestArguments.fromMap(obj);
diff --git a/third_party/pkg/dap/pubspec.yaml b/third_party/pkg/dap/pubspec.yaml
index bf98dd91887..9d180e7d760 100644
--- a/third_party/pkg/dap/pubspec.yaml
+++ b/third_party/pkg/dap/pubspec.yaml
@@ -1,5 +1,5 @@
 name: dap
-version: 1.4.0
+version: 1.5.0-wip
 description: >-
   A package of classes that are generated from the DAP specifications along with
   their generating code.