diff --git a/Fixtures/SwiftMigrate/ExistentialAnyMigration/Sources/Fixed/Test.swift b/Fixtures/SwiftMigrate/ExistentialAnyMigration/Sources/Fixed/Test.swift
index 9ebe6520552..1b6fd4581b9 100644
--- a/Fixtures/SwiftMigrate/ExistentialAnyMigration/Sources/Fixed/Test.swift
+++ b/Fixtures/SwiftMigrate/ExistentialAnyMigration/Sources/Fixed/Test.swift
@@ -1,5 +1,7 @@
 protocol P {
 }
+protocol Q {
+}
 
 func test1(_: any P) {
 }
@@ -14,3 +16,6 @@ func test3() {
 func test4() {
     var x = 42
 }
+
+func test5(_: any P & Q) {
+}
diff --git a/Fixtures/SwiftMigrate/ExistentialAnyMigration/Sources/Test.swift b/Fixtures/SwiftMigrate/ExistentialAnyMigration/Sources/Test.swift
index 5081ad285fa..abfc872e2b4 100644
--- a/Fixtures/SwiftMigrate/ExistentialAnyMigration/Sources/Test.swift
+++ b/Fixtures/SwiftMigrate/ExistentialAnyMigration/Sources/Test.swift
@@ -1,5 +1,7 @@
 protocol P {
 }
+protocol Q {
+}
 
 func test1(_: P) {
 }
@@ -14,3 +16,6 @@ func test3() {
 func test4() {
     var x = 42
 }
+
+func test5(_: P & Q) {
+}
diff --git a/Fixtures/SwiftMigrate/InferIsolatedConformancesMigration/Sources/Fixed/Test2.swift b/Fixtures/SwiftMigrate/InferIsolatedConformancesMigration/Sources/Fixed/Test2.swift
new file mode 100644
index 00000000000..f4e8671264f
--- /dev/null
+++ b/Fixtures/SwiftMigrate/InferIsolatedConformancesMigration/Sources/Fixed/Test2.swift
@@ -0,0 +1,5 @@
+protocol P {}
+protocol Q {}
+
+@MainActor
+struct S: nonisolated P & Q {}
diff --git a/Fixtures/SwiftMigrate/InferIsolatedConformancesMigration/Sources/Test2.swift b/Fixtures/SwiftMigrate/InferIsolatedConformancesMigration/Sources/Test2.swift
new file mode 100644
index 00000000000..b8980dfdaed
--- /dev/null
+++ b/Fixtures/SwiftMigrate/InferIsolatedConformancesMigration/Sources/Test2.swift
@@ -0,0 +1,5 @@
+protocol P {}
+protocol Q {}
+
+@MainActor
+struct S: P & Q {}
diff --git a/Sources/SwiftFixIt/SwiftFixIt.swift b/Sources/SwiftFixIt/SwiftFixIt.swift
index b1539933afc..da0babf5456 100644
--- a/Sources/SwiftFixIt/SwiftFixIt.swift
+++ b/Sources/SwiftFixIt/SwiftFixIt.swift
@@ -301,7 +301,11 @@ extension SwiftFixIt {
                 }
             }
 
-            let result = SwiftIDEUtils.FixItApplier.apply(edits: consume edits, to: sourceFile.syntax)
+            let result = SwiftIDEUtils.FixItApplier.apply(
+                edits: consume edits,
+                to: sourceFile.syntax,
+                allowDuplicateInsertions: false
+            )
 
             try self.fileSystem.writeFileContents(sourceFile.path, string: consume result)
         }
diff --git a/Tests/CommandsTests/PackageCommandTests.swift b/Tests/CommandsTests/PackageCommandTests.swift
index 3b96873e169..9732f2cc554 100644
--- a/Tests/CommandsTests/PackageCommandTests.swift
+++ b/Tests/CommandsTests/PackageCommandTests.swift
@@ -2112,7 +2112,7 @@ class PackageCommandTestCase: CommandsBuildProviderTestCase {
             "skipping because test environment compiler doesn't support `-print-supported-features`"
         )
 
-      func doMigration(featureName: String, expectedSummary: String) async throws {
+        func doMigration(featureName: String, expectedSummary: String) async throws {
             try await fixture(name: "SwiftMigrate/\(featureName)Migration") { fixturePath in
                 let sourcePaths: [AbsolutePath]
                 let fixedSourcePaths: [AbsolutePath]
@@ -2151,9 +2151,11 @@ class PackageCommandTestCase: CommandsBuildProviderTestCase {
             }
         }
 
-        try await doMigration(featureName: "ExistentialAny", expectedSummary: "Applied 3 fix-its in 1 file")
+        // When updating these, make sure we keep testing both the singular and
+        // plural forms of the nouns in the summary.
+        try await doMigration(featureName: "ExistentialAny", expectedSummary: "Applied 5 fix-its in 1 file")
         try await doMigration(featureName: "StrictMemorySafety", expectedSummary: "Applied 1 fix-it in 1 file")
-        try await doMigration(featureName: "InferIsolatedConformances", expectedSummary: "Applied 1 fix-it in 1 file")
+        try await doMigration(featureName: "InferIsolatedConformances", expectedSummary: "Applied 3 fix-its in 2 files")
     }
 
     func testBuildToolPlugin() async throws {
diff --git a/Tests/SwiftFixItTests/FilteringTests.swift b/Tests/SwiftFixItTests/FilteringTests.swift
index 82e5f7ec102..dad7176c94f 100644
--- a/Tests/SwiftFixItTests/FilteringTests.swift
+++ b/Tests/SwiftFixItTests/FilteringTests.swift
@@ -412,19 +412,12 @@ struct FilteringTests {
         }
     }
 
-    @Test
     func testDuplicateInsertionFixIts() throws {
-        withKnownIssue("FIXME: Filter out duplicate insertion fix-its") {
-            try self._testDuplicateInsertionFixIts()
-        }
-    }
-
-    func _testDuplicateInsertionFixIts() throws {
         try testAPI1File { path in
             .init(
                 edits: .init(input: "var x = 1", result: "@W var yx = 21"),
                 summary: .init(
-                    // 4 because skipped by SwiftIDEUtils.FixItApplier, not SwiftFixIt.
+                    // 6 because skipped by SwiftIDEUtils.FixItApplier, not SwiftFixIt.
                     numberOfFixItsApplied: 6,
                     numberOfFilesChanged: 1
                 ),
@@ -470,7 +463,7 @@ struct FilteringTests {
                         text: "error3_fixit1",
                         location: .init(path: path, line: 1, column: 3),
                         fixIts: [
-                            // FIXME: Should be skipped.
+                            // Skipped, duplicate insertion.
                             .init(
                                 start: .init(path: path, line: 1, column: 1),
                                 end: .init(path: path, line: 1, column: 1),
@@ -500,7 +493,7 @@ struct FilteringTests {
                                 text: "error5_note1",
                                 location: .init(path: path, line: 1, column: 9),
                                 fixIts: [
-                                    // FIXME: Should be skipped.
+                                    // Skipped, duplicate insertion.
                                     .init(
                                         start: .init(path: path, line: 1, column: 9),
                                         end: .init(path: path, line: 1, column: 9),
@@ -519,7 +512,7 @@ struct FilteringTests {
                                 text: "error6_note1",
                                 location: .init(path: path, line: 1, column: 5),
                                 fixIts: [
-                                    // FIXME: Should be skipped.
+                                    // Skipped, duplicate insertion.
                                     .init(
                                         start: .init(path: path, line: 1, column: 5),
                                         end: .init(path: path, line: 1, column: 5),