diff --git a/include/swift/AST/DiagnosticsFrontend.def b/include/swift/AST/DiagnosticsFrontend.def
index 065291fe82fb4..c2ebf1b73e9bb 100644
--- a/include/swift/AST/DiagnosticsFrontend.def
+++ b/include/swift/AST/DiagnosticsFrontend.def
@@ -609,6 +609,9 @@ ERROR(no_swift_sources_with_embedded,none,
 ERROR(package_cmo_requires_library_evolution, none,
         "Library evolution must be enabled for Package CMO", ())
 
+WARNING(internal_bridging_header_without_library_evolution,none,
+        "using internal bridging headers without library evolution can cause instability", ())
+
 ERROR(experimental_not_supported_in_production,none,
       "experimental feature '%0' cannot be enabled in production compiler",
       (StringRef))
@@ -636,6 +639,8 @@ NOTE(dependency_scan_unexpected_variant_module_map_note, none,
 NOTE(dependency_scan_unexpected_variant_extra_arg_note, none,
      "%select{first|second}0 module command-line has extra argument: '%1'", (bool, StringRef))
 
+ERROR(bridging_header_and_pch_internal_mismatch,none,
+      "bridging header and precompiled header options mismatch on internal vs. public import", ())
 
 #define UNDEFINE_DIAGNOSTIC_MACROS
 #include "DefineDiagnosticMacros.h"
diff --git a/include/swift/AST/DiagnosticsSema.def b/include/swift/AST/DiagnosticsSema.def
index 97bc1f14a4183..92dfb54da7e8f 100644
--- a/include/swift/AST/DiagnosticsSema.def
+++ b/include/swift/AST/DiagnosticsSema.def
@@ -2702,13 +2702,13 @@ NOTE(module_imported_here,none,
 NOTE(decl_import_via_here,none,
      "%kind0 imported as "
      "'%select{private|fileprivate|internal|package|%ERROR|%ERROR}1' "
-     "from %2 here",
-     (const Decl *, AccessLevel, const ModuleDecl*))
+     "from %select{%2 here|bridging header}3",
+     (const Decl *, AccessLevel, const ModuleDecl*, bool))
 NOTE(decl_import_via_local,none,
      "%kind0 is imported by this file as "
      "'%select{private|fileprivate|internal|package|%ERROR|%ERROR}1' "
-     "from %2",
-     (const Decl *, AccessLevel, const ModuleDecl*))
+     "from %select{%2|bridging header}3",
+     (const Decl *, AccessLevel, const ModuleDecl*, bool))
 
 // Opaque return types
 ERROR(opaque_type_invalid_constraint,none,
@@ -3834,6 +3834,7 @@ ERROR(decl_from_hidden_module,none,
       "%2 was imported for SPI only|"
       "%2 was not imported by this file|"
       "C++ types from imported module %2 do not support library evolution|"
+      "it was imported via the internal bridging header|"
       "%2 was not imported publicly}3",
       (const Decl *, unsigned, Identifier, unsigned))
 ERROR(typealias_desugars_to_type_from_hidden_module,none,
@@ -3850,6 +3851,7 @@ ERROR(typealias_desugars_to_type_from_hidden_module,none,
       "%4 was imported for SPI only|"
       "%4 was not imported by this file|"
       "C++ types from imported module %4 do not support library evolution|"
+      "it was imported via the internal bridging header|"
       "%4 was not imported publicly}5",
       (const TypeAliasDecl *, StringRef, StringRef, unsigned, Identifier, unsigned))
 ERROR(conformance_from_implementation_only_module,none,
@@ -3864,6 +3866,7 @@ ERROR(conformance_from_implementation_only_module,none,
       "%3 was imported for SPI only|"
       "%3 was not imported by this file|"
       "C++ types from imported module %3 do not support library evolution|"
+      "it was imported via the internal bridging header|"
       "%3 was not imported publicly}4",
       (Type, Identifier, unsigned, Identifier, unsigned))
 NOTE(assoc_conformance_from_implementation_only_module,none,
@@ -7317,6 +7320,7 @@ ERROR(inlinable_decl_ref_from_hidden_module,
       "%2 was imported for SPI only|"
       "%2 was not imported by this file|"
       "C++ APIs from imported module %2 do not support library evolution|"
+      "it was imported via the internal bridging header|"
       "%2 was not imported publicly}3",
       (const ValueDecl *, unsigned, Identifier, unsigned))
 
@@ -7328,6 +7332,7 @@ ERROR(inlinable_typealias_desugars_to_type_from_hidden_module,
       "%4 was imported for SPI only|"
       "%4 was not imported by this file|"
       "C++ types from imported module %4 do not support library evolution|"
+      "it was imported via the internal bridging header|"
       "%4 was not imported publicly}5",
       (const TypeAliasDecl *, StringRef, StringRef, unsigned, Identifier, unsigned))
 
diff --git a/include/swift/Basic/LangOptions.h b/include/swift/Basic/LangOptions.h
index cfd593e18112f..e3991483dde0e 100644
--- a/include/swift/Basic/LangOptions.h
+++ b/include/swift/Basic/LangOptions.h
@@ -1046,6 +1046,10 @@ namespace swift {
     /// The bridging header PCH file.
     std::string BridgingHeaderPCH;
 
+    /// Whether the bridging header and PCH file are considered to be
+    /// internal imports.
+    bool BridgingHeaderIsInternal = false;
+
     /// When automatically generating a precompiled header from the bridging
     /// header, place it in this directory.
     std::string PrecompiledHeaderOutputDir;
diff --git a/include/swift/Frontend/FrontendOptions.h b/include/swift/Frontend/FrontendOptions.h
index eee71255c1392..38b91a728e8bb 100644
--- a/include/swift/Frontend/FrontendOptions.h
+++ b/include/swift/Frontend/FrontendOptions.h
@@ -66,12 +66,16 @@ class FrontendOptions {
 
   bool isOutputFileDirectory() const;
 
-  /// An Objective-C header to import and make implicitly visible.
+  /// A C header to import and make implicitly visible.
   std::string ImplicitObjCHeaderPath;
 
-  /// An Objective-C pch to import and make implicitly visible.
+  /// A C pch to import and make implicitly visible.
   std::string ImplicitObjCPCHPath;
 
+  /// Whether the imported C header or precompiled header is considered
+  /// an internal import (vs. the default, a public import).
+  bool ImportHeaderAsInternal = false;
+
   /// The map of aliases and real names of imported or referenced modules.
   llvm::StringMap<std::string> ModuleAliasMap;
 
diff --git a/include/swift/Option/Options.td b/include/swift/Option/Options.td
index c3d87e4941df9..e99cdc850671f 100644
--- a/include/swift/Option/Options.td
+++ b/include/swift/Option/Options.td
@@ -347,16 +347,25 @@ def import_underlying_module : Flag<["-"], "import-underlying-module">,
   Flags<[FrontendOption, NoInteractiveOption]>,
   HelpText<"Implicitly imports the Objective-C half of a module">;
 
-def import_objc_header : Separate<["-"], "import-objc-header">,
-  Flags<[FrontendOption, HelpHidden, ArgumentIsPath]>,
-  HelpText<"Implicitly imports an Objective-C header file">;
 def import_bridging_header : Separate<["-"], "import-bridging-header">,
+  Flags<[FrontendOption, ArgumentIsPath]>,
+  HelpText<"Implicitly imports a C header file">;
+def import_objc_header : Separate<["-"], "import-objc-header">,
   Flags<[FrontendOption, HelpHidden, ArgumentIsPath]>,
-  Alias<import_objc_header>;
+  Alias<import_bridging_header>;
+
+def internal_import_bridging_header : Separate<["-"], "internal-import-bridging-header">,
+  Flags<[FrontendOption, ArgumentIsPath]>,
+  HelpText<"Implicitly imports a C header file as an internal import">;
+
 def import_pch : Separate<["-"], "import-pch">,
   Flags<[FrontendOption, HelpHidden, ArgumentIsPath]>,
   HelpText<"Import bridging header PCH file">;
 
+def internal_import_pch : Separate<["-"], "internal-import-pch">,
+  Flags<[FrontendOption, HelpHidden, ArgumentIsPath]>,
+  HelpText<"Import bridging header PCH file as internal">;
+
 def pch_output_dir: Separate<["-"], "pch-output-dir">,
   Flags<[FrontendOption, HelpHidden, ArgumentIsPath]>,
   HelpText<"Directory to persist automatically created precompiled bridging headers">;
diff --git a/lib/AST/Module.cpp b/lib/AST/Module.cpp
index 93409fb5eed9b..c3ed11ff240cd 100644
--- a/lib/AST/Module.cpp
+++ b/lib/AST/Module.cpp
@@ -2991,7 +2991,9 @@ SourceFile::getImportAccessLevel(const ModuleDecl *targetModule) const {
   // they are recommended over indirect imports.
   if ((!restrictiveImport.has_value() ||
        restrictiveImport->accessLevel < AccessLevel::Public) &&
-     imports.isImportedBy(targetModule, getParentModule()))
+      !(restrictiveImport &&
+        restrictiveImport->module.importedModule->isClangHeaderImportModule()) &&
+      imports.isImportedBy(targetModule, getParentModule()))
     return std::nullopt;
 
   return restrictiveImport;
diff --git a/lib/ClangImporter/ClangImporter.cpp b/lib/ClangImporter/ClangImporter.cpp
index 6182b43e83a50..19449f9365094 100644
--- a/lib/ClangImporter/ClangImporter.cpp
+++ b/lib/ClangImporter/ClangImporter.cpp
@@ -2714,6 +2714,7 @@ ClangImporter::Implementation::Implementation(
       DisableSwiftBridgeAttr(ctx.ClangImporterOpts.DisableSwiftBridgeAttr),
       BridgingHeaderExplicitlyRequested(
           !ctx.ClangImporterOpts.BridgingHeader.empty()),
+      BridgingHeaderIsInternal(ctx.ClangImporterOpts.BridgingHeaderIsInternal),
       DisableOverlayModules(ctx.ClangImporterOpts.DisableOverlayModules),
       EnableClangSPI(ctx.ClangImporterOpts.EnableClangSPI),
       IsReadingBridgingPCH(false),
@@ -3762,8 +3763,13 @@ ImportDecl *swift::createImportDecl(ASTContext &Ctx,
   auto *ID = ImportDecl::create(Ctx, DC, SourceLoc(),
                                 ImportKind::Module, SourceLoc(),
                                 importPath.get(), ClangN);
-  if (IsExported)
+  if (Ctx.ClangImporterOpts.BridgingHeaderIsInternal) {
+    ID->getAttrs().add(
+        new (Ctx) AccessControlAttr(SourceLoc(), SourceRange(),
+                                    AccessLevel::Internal, /*implicit=*/true));
+  } else if (IsExported) {
     ID->getAttrs().add(new (Ctx) ExportedAttr(/*IsImplicit=*/false));
+  }
   return ID;
 }
 
diff --git a/lib/ClangImporter/ImporterImpl.h b/lib/ClangImporter/ImporterImpl.h
index 3138cca331a52..4b7126a7b2d0d 100644
--- a/lib/ClangImporter/ImporterImpl.h
+++ b/lib/ClangImporter/ImporterImpl.h
@@ -481,6 +481,7 @@ class LLVM_LIBRARY_VISIBILITY ClangImporter::Implementation
   const bool ImportForwardDeclarations;
   const bool DisableSwiftBridgeAttr;
   const bool BridgingHeaderExplicitlyRequested;
+  const bool BridgingHeaderIsInternal;
   const bool DisableOverlayModules;
   const bool EnableClangSPI;
 
diff --git a/lib/Driver/Driver.cpp b/lib/Driver/Driver.cpp
index 6c42ca0c8a64c..60903dd63226d 100644
--- a/lib/Driver/Driver.cpp
+++ b/lib/Driver/Driver.cpp
@@ -144,7 +144,8 @@ static void validateLegacyUnsupportedArgs(DiagnosticEngine &diags,
 
 static void validateBridgingHeaderArgs(DiagnosticEngine &diags,
                                        const ArgList &args) {
-  if (!args.hasArgNoClaim(options::OPT_import_objc_header))
+  if (!args.hasArgNoClaim(options::OPT_import_bridging_header,
+                          options::OPT_internal_import_bridging_header))
     return;
 
   if (args.hasArgNoClaim(options::OPT_import_underlying_module))
@@ -1521,7 +1522,9 @@ void Driver::buildActions(SmallVectorImpl<const Action *> &TopLevelActions,
     if (Args.hasFlag(options::OPT_enable_bridging_pch,
                      options::OPT_disable_bridging_pch,
                      true)) {
-      if (Arg *A = Args.getLastArg(options::OPT_import_objc_header)) {
+      if (Arg *A = Args.getLastArg(
+              options::OPT_import_bridging_header,
+              options::OPT_internal_import_bridging_header)) {
         StringRef Value = A->getValue();
         auto Ty = TC.lookupTypeForExtension(llvm::sys::path::extension(Value));
         if (Ty == file_types::TY_ClangHeader) {
diff --git a/lib/Driver/ToolChains.cpp b/lib/Driver/ToolChains.cpp
index 8011dd7d02b62..2d2deec00e082 100644
--- a/lib/Driver/ToolChains.cpp
+++ b/lib/Driver/ToolChains.cpp
@@ -522,19 +522,28 @@ ToolChain::constructInvocation(const CompileJobAction &job,
   addCommonFrontendArgs(context.OI, context.Output, context.Args, Arguments);
   addRuntimeLibraryFlags(context.OI, Arguments);
 
-  // Pass along an -import-objc-header arg, replacing the argument with the name
-  // of any input PCH to the current action if one is present.
-  if (context.Args.hasArgNoClaim(options::OPT_import_objc_header)) {
+  // Pass along an -(internal-)?import-bridging-header arg, replacing the
+  // argument with the name of any input PCH to the current action if one is
+  // present.
+  if (context.Args.hasArgNoClaim(options::OPT_import_bridging_header,
+                                 options::OPT_internal_import_bridging_header)) {
     bool ForwardAsIs = true;
     bool bridgingPCHIsEnabled =
         context.Args.hasFlag(options::OPT_enable_bridging_pch,
                              options::OPT_disable_bridging_pch, true);
     bool usePersistentPCH = bridgingPCHIsEnabled &&
                             context.Args.hasArg(options::OPT_pch_output_dir);
+    bool isInternalImport = context.Args.getLastArgNoClaim(
+        options::OPT_import_bridging_header,
+        options::OPT_internal_import_bridging_header)
+      ->getOption().getID() == options::OPT_internal_import_bridging_header;
     if (!usePersistentPCH) {
       for (auto *IJ : context.Inputs) {
         if (!IJ->getOutput().getAnyOutputForType(file_types::TY_PCH).empty()) {
-          Arguments.push_back("-import-objc-header");
+          if (isInternalImport)
+            Arguments.push_back("-internal-import-bridging-header");
+          else
+            Arguments.push_back("-import-bridging-header");
           addInputsOfType(Arguments, context.Inputs, context.Args,
                           file_types::TY_PCH);
           ForwardAsIs = false;
@@ -543,7 +552,8 @@ ToolChain::constructInvocation(const CompileJobAction &job,
       }
     }
     if (ForwardAsIs) {
-      context.Args.AddLastArg(Arguments, options::OPT_import_objc_header);
+      context.Args.AddLastArg(Arguments, options::OPT_import_bridging_header,
+                              options::OPT_internal_import_bridging_header);
     }
     if (usePersistentPCH) {
       context.Args.AddLastArg(Arguments, options::OPT_pch_output_dir);
@@ -972,7 +982,8 @@ ToolChain::constructInvocation(const InterpretJobAction &job,
   addCommonFrontendArgs(context.OI, context.Output, context.Args, Arguments);
   addRuntimeLibraryFlags(context.OI, Arguments);
 
-  context.Args.AddLastArg(Arguments, options::OPT_import_objc_header);
+  context.Args.AddLastArg(Arguments, options::OPT_import_bridging_header,
+                          options::OPT_internal_import_bridging_header);
 
   context.Args.AddLastArg(Arguments, options::OPT_parse_sil);
 
@@ -1233,7 +1244,8 @@ ToolChain::constructInvocation(const MergeModuleJobAction &job,
                           options::OPT_omit_extension_block_symbols);
   context.Args.AddLastArg(Arguments, options::OPT_symbol_graph_minimum_access_level);
 
-  context.Args.AddLastArg(Arguments, options::OPT_import_objc_header);
+  context.Args.AddLastArg(Arguments, options::OPT_import_bridging_header,
+                          options::OPT_internal_import_bridging_header);
 
   Arguments.push_back("-module-name");
   Arguments.push_back(context.Args.MakeArgString(context.OI.ModuleName));
@@ -1276,7 +1288,8 @@ ToolChain::constructInvocation(const VerifyModuleInterfaceJobAction &job,
                    file_types::TY_SerializedDiagnostics,
                    "-serialize-diagnostics-path");
 
-  context.Args.AddLastArg(Arguments, options::OPT_import_objc_header);
+  context.Args.AddLastArg(Arguments, options::OPT_import_bridging_header,
+                          options::OPT_internal_import_bridging_header);
 
   Arguments.push_back("-module-name");
   Arguments.push_back(context.Args.MakeArgString(context.OI.ModuleName));
@@ -1342,7 +1355,8 @@ ToolChain::constructInvocation(const REPLJobAction &job,
   addCommonFrontendArgs(context.OI, context.Output, context.Args, FrontendArgs);
   addRuntimeLibraryFlags(context.OI, FrontendArgs);
 
-  context.Args.AddLastArg(FrontendArgs, options::OPT_import_objc_header);
+  context.Args.AddLastArg(FrontendArgs, options::OPT_import_bridging_header,
+                          options::OPT_internal_import_bridging_header);
   context.Args.addAllArgs(FrontendArgs,
                           {options::OPT_framework, options::OPT_L});
   ToolChain::addLinkedLibArgs(context.Args, FrontendArgs);
diff --git a/lib/Frontend/ArgsToFrontendOptionsConverter.cpp b/lib/Frontend/ArgsToFrontendOptionsConverter.cpp
index ecbcfbd3d44d1..b40573686b280 100644
--- a/lib/Frontend/ArgsToFrontendOptionsConverter.cpp
+++ b/lib/Frontend/ArgsToFrontendOptionsConverter.cpp
@@ -913,18 +913,40 @@ static inline bool isPCHFilenameExtension(StringRef path) {
 
 void ArgsToFrontendOptionsConverter::computeImportObjCHeaderOptions() {
   using namespace options;
-  if (const Arg *A = Args.getLastArgNoClaim(OPT_import_objc_header)) {
-    // Legacy support for passing PCH file through `-import-objc-header`.
+  bool hadNormalBridgingHeader = false;
+  if (const Arg *A = Args.getLastArgNoClaim(
+          OPT_import_bridging_header,
+          OPT_internal_import_bridging_header)) {
+    // Legacy support for passing PCH file through `-import-bridging-header`.
     if (isPCHFilenameExtension(A->getValue()))
       Opts.ImplicitObjCPCHPath = A->getValue();
     else
       Opts.ImplicitObjCHeaderPath = A->getValue();
-    // If `-import-object-header` is used, it means the module has a direct
+    // If `-import-bridging-header` is used, it means the module has a direct
     // bridging header dependency and it can be serialized into binary module.
     Opts.ModuleHasBridgingHeader |= true;
+
+    Opts.ImportHeaderAsInternal =
+        A->getOption().getID() == OPT_internal_import_bridging_header;
+
+    hadNormalBridgingHeader = true;
   }
-  if (const Arg *A = Args.getLastArgNoClaim(OPT_import_pch))
+  if (const Arg *A = Args.getLastArgNoClaim(OPT_import_pch,
+                                            OPT_internal_import_pch)) {
     Opts.ImplicitObjCPCHPath = A->getValue();
+
+    bool importAsInternal = A->getOption().getID() == OPT_internal_import_pch;
+
+    /// Don't let the bridging-header and precompiled-header options differ in
+    /// whether they are treated as internal or public imports.
+    if (hadNormalBridgingHeader &&
+        importAsInternal != Opts.ImportHeaderAsInternal) {
+      Diags.diagnose(SourceLoc(),
+                     diag::bridging_header_and_pch_internal_mismatch);
+    }
+
+    Opts.ImportHeaderAsInternal = importAsInternal;
+  }
 }
 void ArgsToFrontendOptionsConverter::
 computeImplicitImportModuleNames(OptSpecifier id, bool isTestable) {
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index d31373ff4b4d7..0f7e155b9c2da 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -363,6 +363,8 @@ setBridgingHeaderFromFrontendOptions(ClangImporterOptions &ImporterOpts,
   if (!FrontendOpts.InputsAndOutputs.hasInputs())
     return;
 
+  ImporterOpts.BridgingHeaderIsInternal = FrontendOpts.ImportHeaderAsInternal;
+
   // If we aren't asked to output a bridging header, we don't need to set this.
   if (ImporterOpts.PrecompiledHeaderOutputDir.empty())
     return;
@@ -2109,10 +2111,31 @@ static bool ParseClangImporterArgs(ClangImporterOptions &Opts, ArgList &Args,
   else if (Args.hasArg(OPT_emit_pcm) || Args.hasArg(OPT_dump_pcm))
     Opts.Mode = ClangImporterOptions::Modes::PrecompiledModule;
 
-  if (auto *A = Args.getLastArg(OPT_import_objc_header))
+  bool hadNormalBridgingHeader = false;
+  if (auto *A = Args.getLastArg(OPT_import_bridging_header,
+                                OPT_internal_import_bridging_header)) {
     Opts.BridgingHeader = A->getValue();
-  if (auto *A = Args.getLastArg(OPT_import_pch))
+    Opts.BridgingHeaderIsInternal =
+        A->getOption().getID() == OPT_internal_import_bridging_header;
+  }
+  if (auto *A = Args.getLastArg(OPT_import_pch, OPT_internal_import_pch)) {
     Opts.BridgingHeaderPCH = A->getValue();
+    bool importAsInternal = A->getOption().getID() == OPT_internal_import_pch;
+    if (hadNormalBridgingHeader &&
+        importAsInternal != Opts.BridgingHeaderIsInternal) {
+      Diags.diagnose(SourceLoc(),
+                     diag::bridging_header_and_pch_internal_mismatch);
+    }
+    Opts.BridgingHeaderIsInternal = importAsInternal;
+  }
+
+  // Until we have some checking in place, internal bridging headers are a
+  // bit unsafe without library evolution.
+  if (Opts.BridgingHeaderIsInternal && !FrontendOpts.EnableLibraryEvolution) {
+    Diags.diagnose(SourceLoc(),
+                   diag::internal_bridging_header_without_library_evolution);
+  }
+
   Opts.DisableSwiftBridgeAttr |= Args.hasArg(OPT_disable_swift_bridge_attr);
 
   Opts.DisableOverlayModules |= Args.hasArg(OPT_emit_imported_modules);
diff --git a/lib/Frontend/Frontend.cpp b/lib/Frontend/Frontend.cpp
index 5ce141e45a407..ff0ba284205fd 100644
--- a/lib/Frontend/Frontend.cpp
+++ b/lib/Frontend/Frontend.cpp
@@ -197,7 +197,8 @@ SerializationOptions CompilerInvocation::computeSerializationOptions(
   serializationOpts.DocOutputPath = outs.ModuleDocOutputPath;
   serializationOpts.SourceInfoOutputPath = outs.ModuleSourceInfoOutputPath;
   serializationOpts.GroupInfoPath = opts.GroupInfoPath.c_str();
-  if (opts.ModuleHasBridgingHeader && !outs.ModuleOutputPath.empty())
+  if (opts.ModuleHasBridgingHeader && !outs.ModuleOutputPath.empty() &&
+      !opts.ImportHeaderAsInternal)
     serializationOpts.SerializeBridgingHeader = true;
   // For batch mode, emit empty header path as placeholder.
   if (serializationOpts.SerializeBridgingHeader &&
diff --git a/lib/Option/features.json b/lib/Option/features.json
index f9c87c00022b9..7d521787a4dd8 100644
--- a/lib/Option/features.json
+++ b/lib/Option/features.json
@@ -50,6 +50,9 @@
     },
     {
        "name": "Isystem"
+    },
+    {
+       "name": "internal-import-bridging-header"
     }
   ]
 }
diff --git a/lib/Sema/ImportResolution.cpp b/lib/Sema/ImportResolution.cpp
index e14ef37dfb046..9811296b1611d 100644
--- a/lib/Sema/ImportResolution.cpp
+++ b/lib/Sema/ImportResolution.cpp
@@ -574,8 +574,13 @@ ModuleImplicitImportsRequest::evaluate(Evaluator &evaluator,
       !clangImporter->importBridgingHeader(bridgingHeaderPath, module)) {
     auto *headerModule = clangImporter->getImportedHeaderModule();
     assert(headerModule && "Didn't load bridging header?");
-    imports.emplace_back(
+    AttributedImport<ImportedModule> import(
         ImportedModule(headerModule), SourceLoc(), ImportFlags::Exported);
+    if (ctx.ClangImporterOpts.BridgingHeaderIsInternal) {
+      import.accessLevel = AccessLevel::Internal;
+    }
+
+    imports.emplace_back(import);
   }
 
   // Implicitly import the underlying Clang half of this module if needed.
diff --git a/lib/Sema/ResilienceDiagnostics.cpp b/lib/Sema/ResilienceDiagnostics.cpp
index 5fb3249585144..3a4dbd1112107 100644
--- a/lib/Sema/ResilienceDiagnostics.cpp
+++ b/lib/Sema/ResilienceDiagnostics.cpp
@@ -133,7 +133,9 @@ bool TypeChecker::diagnoseInlinableDeclRefAccess(SourceLoc loc,
     Context.Diags.diagnose(problematicImport->importLoc,
                            diag::decl_import_via_here, D,
                            problematicImport->accessLevel,
-                           problematicImport->module.importedModule);
+                           problematicImport->module.importedModule,
+                           problematicImport->module.importedModule
+                             ->isClangHeaderImportModule());
   }
 
   return (downgradeToWarning == DowngradeToWarning::No);
@@ -213,7 +215,9 @@ static bool diagnoseTypeAliasDeclRefExportability(SourceLoc loc,
     ctx.Diags.diagnose(limitImport->importLoc,
                        diag::decl_import_via_here, D,
                        limitImport->accessLevel,
-                       limitImport->module.importedModule);
+                       limitImport->module.importedModule,
+                       limitImport->module.importedModule
+                         ->isClangHeaderImportModule());
   }
 
   return true;
@@ -273,7 +277,8 @@ static bool diagnoseValueDeclRefExportability(SourceLoc loc, const ValueDecl *D,
       D, DC, AccessLevel::Public,
       [&](AttributedImport<ImportedModule> attributedImport) {
         if (where.isExported() && reason != ExportabilityReason::General &&
-            originKind != DisallowedOriginKind::NonPublicImport) {
+            originKind != DisallowedOriginKind::NonPublicImport &&
+            originKind != DisallowedOriginKind::InternalBridgingHeaderImport) {
           // These may be reported twice, for the Type and for the TypeRepr.
           ModuleDecl *importedVia = attributedImport.module.importedModule,
                      *sourceModule = D->getModuleContext();
@@ -290,6 +295,7 @@ static bool diagnoseValueDeclRefExportability(SourceLoc loc, const ValueDecl *D,
     return false;
 
   case DisallowedOriginKind::NonPublicImport:
+  case DisallowedOriginKind::InternalBridgingHeaderImport:
     // With a few exceptions, access levels from imports are diagnosed during
     // access checking and should be skipped here.
     if (!shouldDiagnoseDeclAccess(D, where))
@@ -368,7 +374,9 @@ static bool diagnoseValueDeclRefExportability(SourceLoc loc, const ValueDecl *D,
     ctx.Diags.diagnose(import->importLoc,
                        diag::decl_import_via_here, D,
                        import->accessLevel,
-                       import->module.importedModule);
+                       import->module.importedModule,
+                       import->module.importedModule
+                         ->isClangHeaderImportModule());
   }
 
   return true;
@@ -454,7 +462,9 @@ TypeChecker::diagnoseConformanceExportability(SourceLoc loc,
     ctx.Diags.diagnose(limitImport->importLoc,
                        diag::decl_import_via_here, ext,
                        limitImport->accessLevel,
-                       limitImport->module.importedModule);
+                       limitImport->module.importedModule,
+                       limitImport->module.importedModule
+                         ->isClangHeaderImportModule());
   }
 
   return true;
diff --git a/lib/Sema/TypeCheckAccess.cpp b/lib/Sema/TypeCheckAccess.cpp
index 4a844cf7b2e0f..f7c12060e4ac5 100644
--- a/lib/Sema/TypeCheckAccess.cpp
+++ b/lib/Sema/TypeCheckAccess.cpp
@@ -454,12 +454,16 @@ static void noteLimitingImport(const Decl *userDecl, ASTContext &ctx,
     if (userDecl)
       userDecl->diagnose(diag::decl_import_via_local, complainDecl,
                          limitImport->accessLevel,
-                         limitImport->module.importedModule);
+                         limitImport->module.importedModule,
+                         limitImport->module.importedModule
+                           ->isClangHeaderImportModule());
 
     if (limitImport->importLoc.isValid())
       ctx.Diags.diagnose(limitImport->importLoc, diag::decl_import_via_here,
                          complainDecl, limitImport->accessLevel,
-                         limitImport->module.importedModule);
+                         limitImport->module.importedModule,
+                         limitImport->module.importedModule
+                           ->isClangHeaderImportModule());
   } else if (limitImport->importLoc.isValid()) {
     ctx.Diags.diagnose(limitImport->importLoc, diag::module_imported_here,
                        limitImport->module.importedModule,
@@ -2163,8 +2167,11 @@ swift::getDisallowedOriginKind(const Decl *decl,
   // See \c diagnoseValueDeclRefExportability.
   auto importSource = decl->getImportAccessFrom(where.getDeclContext());
   if (importSource.has_value() &&
-      importSource->accessLevel < AccessLevel::Public)
-    return DisallowedOriginKind::NonPublicImport;
+      importSource->accessLevel < AccessLevel::Public) {
+    return importSource->module.importedModule->isClangHeaderImportModule()
+      ? DisallowedOriginKind::InternalBridgingHeaderImport
+      : DisallowedOriginKind::NonPublicImport;
+  }
 
   return DisallowedOriginKind::None;
 }
@@ -2692,6 +2699,11 @@ void swift::recordRequiredImportAccessLevelForDecl(
   if (definingModule == dc->getParentModule())
     return;
 
+  // Egregious hack: if the declaration is for a C++ namespace, assume it's
+  // accessible.
+  if (isa_and_nonnull<clang::NamespaceDecl>(decl->getClangDecl()))
+    return;
+
   sf->registerRequiredAccessLevelForModule(definingModule, accessLevel);
 
   if (auto attributedImport = sf->getImportAccessLevel(definingModule)) {
diff --git a/lib/Sema/TypeCheckAccess.h b/lib/Sema/TypeCheckAccess.h
index 6291c1de9d419..c97312b962370 100644
--- a/lib/Sema/TypeCheckAccess.h
+++ b/lib/Sema/TypeCheckAccess.h
@@ -47,6 +47,10 @@ enum class DisallowedOriginKind : uint8_t {
   SPIOnly,
   MissingImport,
   FragileCxxAPI,
+
+  /// An import that is internal via the internally-imported bridging header.
+  InternalBridgingHeaderImport,
+
   NonPublicImport,
   None
 };
diff --git a/test/ClangImporter/Inputs/c-bridging-header.h b/test/ClangImporter/Inputs/c-bridging-header.h
new file mode 100644
index 0000000000000..5dc00a6d1a586
--- /dev/null
+++ b/test/ClangImporter/Inputs/c-bridging-header.h
@@ -0,0 +1,12 @@
+#ifndef C_BRIDGING_HEADER_H
+#define C_BRIDGING_HEADER_H
+
+#include "ctypes.h"
+#include "macros.h"
+
+typedef struct {
+  double x, y;
+} MyPoint;
+
+typedef double MyDouble;
+#endif
diff --git a/test/ClangImporter/Inputs/cxx-bridging-header.h b/test/ClangImporter/Inputs/cxx-bridging-header.h
new file mode 100644
index 0000000000000..d792ba4ecc409
--- /dev/null
+++ b/test/ClangImporter/Inputs/cxx-bridging-header.h
@@ -0,0 +1,9 @@
+
+namespace OuterNS {
+  class MyPoint {
+  public:
+    double x, y;
+  };
+}
+
+#include "cxx-outer-ns.h"
diff --git a/test/ClangImporter/Inputs/cxx-outer-ns.h b/test/ClangImporter/Inputs/cxx-outer-ns.h
new file mode 100644
index 0000000000000..d9d78404852f4
--- /dev/null
+++ b/test/ClangImporter/Inputs/cxx-outer-ns.h
@@ -0,0 +1,7 @@
+namespace OuterNS {
+  enum Color {
+    red,
+    green,
+    blue
+  };
+}
diff --git a/test/ClangImporter/Inputs/module.modulemap b/test/ClangImporter/Inputs/module.modulemap
new file mode 100644
index 0000000000000..296486613ab8c
--- /dev/null
+++ b/test/ClangImporter/Inputs/module.modulemap
@@ -0,0 +1,3 @@
+module CXXOuterNS {
+  header "cxx-outer-ns.h"
+}
diff --git a/test/ClangImporter/InternalBridgingHeader/access_checking.swift b/test/ClangImporter/InternalBridgingHeader/access_checking.swift
new file mode 100644
index 0000000000000..237536cec4ef7
--- /dev/null
+++ b/test/ClangImporter/InternalBridgingHeader/access_checking.swift
@@ -0,0 +1,39 @@
+// RUN: %empty-directory(%t)
+// RUN: mkdir -p %t/tmp
+
+// Test with the normal bridging header.
+// RUN: %target-typecheck-verify-swift -internal-import-bridging-header %S/../Inputs/c-bridging-header.h -sdk %clang-importer-sdk
+
+// Test with a precompiled bridging header.
+// RUN: %target-swift-frontend -emit-pch -o %t/c-bridging-header.pch %S/../Inputs/c-bridging-header.h -sdk %clang-importer-sdk
+// RUN: %target-typecheck-verify-swift -internal-import-bridging-header %t/c-bridging-header.pch -sdk %clang-importer-sdk
+
+
+// Overrides the internal import that comes through the bridging header.
+public import macros
+
+public func getRed() -> Color { red } // expected-error{{function cannot be declared public because its result uses an internal type}}
+// expected-note@-1{{struct 'Color' is imported by this file as 'internal' from bridging header}}
+
+public func getX(point: MyPoint) -> Double { point.x } // expected-error{{function cannot be declared public because its parameter uses an internal type}}
+// expected-note@-1{{struct 'MyPoint' is imported by this file as 'internal' from bridging header}}
+
+// Comes from the macros module.
+public func returnsFromMacrosModule() -> okay_t { 0 }
+
+public protocol P {
+  associatedtype A
+}
+
+public struct MyType: P {
+  public typealias A = MyDouble
+  // expected-error@-1{{type alias cannot be declared public because its underlying type uses an internal type}}
+  // expected-note@-2{{type alias 'MyDouble' is imported by this file as 'internal' from bridging header}}
+}
+
+// expected-error@+1{{cannot use struct 'MyPoint' in an extension with public or '@usableFromInline' members; it was imported via the internal bridging header}}
+extension MyPoint: P {
+  public typealias A = MyDouble
+  // expected-error@-1{{type alias cannot be declared public because its underlying type uses an internal type}}
+  // expected-note@-2{{type alias 'MyDouble' is imported by this file as 'internal' from bridging header}}
+}
diff --git a/test/ClangImporter/InternalBridgingHeader/access_checking_cxx.swift b/test/ClangImporter/InternalBridgingHeader/access_checking_cxx.swift
new file mode 100644
index 0000000000000..fb355fd625db5
--- /dev/null
+++ b/test/ClangImporter/InternalBridgingHeader/access_checking_cxx.swift
@@ -0,0 +1,9 @@
+// RUN: %target-typecheck-verify-swift -internal-import-bridging-header %S/../Inputs/cxx-bridging-header.h -sdk %clang-importer-sdk -cxx-interoperability-mode=default -I %S/../Inputs
+
+public func getRed() -> OuterNS.Color { OuterNS.red }
+// expected-error@-1{{function cannot be declared public because its result uses an internal type}}
+// expected-note@-2{{enum 'OuterNS' is imported by this file as 'internal' from bridging header}}
+
+public func getX(point: OuterNS.MyPoint) -> Double { point.x }
+// expected-error@-1{{function cannot be declared public because its parameter uses an internal type}}
+// expected-note@-2{{enum 'OuterNS' is imported by this file as 'internal' from bridging header}}
diff --git a/test/ClangImporter/InternalBridgingHeader/implementation_only_checking.swift b/test/ClangImporter/InternalBridgingHeader/implementation_only_checking.swift
new file mode 100644
index 0000000000000..ba10fe9969c62
--- /dev/null
+++ b/test/ClangImporter/InternalBridgingHeader/implementation_only_checking.swift
@@ -0,0 +1,21 @@
+// RUN: %empty-directory(%t)
+// RUN: mkdir -p %t/tmp
+
+// Test with the normal bridging header.
+// RUN: %target-typecheck-verify-swift -internal-import-bridging-header %S/../Inputs/c-bridging-header.h -sdk %clang-importer-sdk -verify-ignore-unknown
+
+// RUN: not %target-swift-frontend -typecheck -internal-import-bridging-header %S/../Inputs/c-bridging-header.h -sdk %clang-importer-sdk %s 2>&1 | %FileCheck %s
+
+// Test with a precompiled bridging header.
+// RUN: %target-swift-frontend -emit-pch -o %t/c-bridging-header.pch %S/../Inputs/c-bridging-header.h -sdk %clang-importer-sdk
+// RUN: %target-typecheck-verify-swift -internal-import-bridging-header %t/c-bridging-header.pch -sdk %clang-importer-sdk -verify-ignore-unknown
+
+
+@inlinable
+public func f() -> Any {
+  return red
+  // expected-error@-1{{var 'red' is internal and cannot be referenced from an '@inlinable' function}}
+  // expected-warning@-2{{getter for var 'red' is internal and should not be referenced from an '@inlinable' function}}
+}
+
+// CHECK: var 'red' imported as 'internal' from bridging header
diff --git a/test/ClangImporter/InternalBridgingHeader/interface.swift b/test/ClangImporter/InternalBridgingHeader/interface.swift
new file mode 100644
index 0000000000000..f6ea1825348fe
--- /dev/null
+++ b/test/ClangImporter/InternalBridgingHeader/interface.swift
@@ -0,0 +1,14 @@
+// RUN: %empty-directory(%t)
+
+// RUN: %target-swift-emit-module-interface(%t/MyModule.swiftinterface) %s -module-name MyModule -internal-import-bridging-header %S/../Inputs/c-bridging-header.h -sdk %clang-importer-sdk -enable-library-evolution
+
+// RUN: %FileCheck %s < %t/MyModule.swiftinterface
+
+// CHECK-NOT: internal-import-bridging-header
+
+// CHECK: public func g()
+
+func getX(point: MyPoint) -> Double { point.x }
+
+public func g() {
+}
diff --git a/test/ClangImporter/InternalBridgingHeader/library_evolution.swift b/test/ClangImporter/InternalBridgingHeader/library_evolution.swift
new file mode 100644
index 0000000000000..df3b9de4bf58e
--- /dev/null
+++ b/test/ClangImporter/InternalBridgingHeader/library_evolution.swift
@@ -0,0 +1,14 @@
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -internal-import-bridging-header %S/../Inputs/c-bridging-header.h -sdk %clang-importer-sdk %s 2>&1 | %FileCheck -check-prefix NONRESILIENT %s
+
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -internal-import-bridging-header %S/../Inputs/c-bridging-header.h -sdk %clang-importer-sdk %s -enable-library-evolution 2>&1 | %FileCheck -check-prefix EVOLUTION %s
+
+// NONRESILIENT: warning: using internal bridging headers without library evolution can cause instability
+
+// EVOLUTION-NOT: internal bridging head
+
+@available(*, deprecated)
+func f() { }
+
+func g(){
+  f() // make sure we emit something
+}
diff --git a/test/ClangImporter/InternalBridgingHeader/pch.swift b/test/ClangImporter/InternalBridgingHeader/pch.swift
new file mode 100644
index 0000000000000..d0b65ffe8a993
--- /dev/null
+++ b/test/ClangImporter/InternalBridgingHeader/pch.swift
@@ -0,0 +1,52 @@
+// RUN: %empty-directory(%t)
+// RUN: mkdir -p %t/tmp
+
+// First test the explicit frontend-based bridging PCH generation and use works
+// RUN: %target-swift-frontend -emit-pch -o %t/c-bridging-header.pch %S/../Inputs/c-bridging-header.h -sdk %clang-importer-sdk
+// RUN: %target-typecheck-verify-swift -internal-import-bridging-header %t/c-bridging-header.pch -sdk %clang-importer-sdk
+
+// Now test the driver-automated version is inert when disabled
+// Output path of the PCH differs in the new driver, so force SWIFT_USE_OLD_DRIVER for now.
+// RUN: env TMPDIR=%t/tmp/ SWIFT_USE_OLD_DRIVER=1 %target-swiftc_driver -typecheck -disable-bridging-pch -save-temps %s -internal-import-bridging-header %S/../Inputs/c-bridging-header.h -sdk %clang-importer-sdk
+// RUN: not ls %t/tmp/*.pch >/dev/null 2>&1
+
+// Test the driver-automated version works by default
+// Output path of the PCH differs in the new driver, so force SWIFT_USE_OLD_DRIVER for now.
+// RUN: env TMPDIR=%t/tmp/ SWIFT_USE_OLD_DRIVER=1 %target-swiftc_driver -typecheck -save-temps %s -internal-import-bridging-header %S/../Inputs/c-bridging-header.h -sdk %clang-importer-sdk
+// RUN: ls %t/tmp/*.pch >/dev/null 2>&1
+// RUN: llvm-objdump --raw-clang-ast %t/tmp/*.pch | llvm-bcanalyzer -dump | %FileCheck %s
+// CHECK: ORIGINAL_FILE{{.*}}Inputs/c-bridging-header.h
+
+// Test the driver-automated version deletes its PCH file when done
+// RUN: rm %t/tmp/*.pch
+// RUN: env TMPDIR=%t/tmp/ %target-swiftc_driver -typecheck %s -internal-import-bridging-header %S/../Inputs/c-bridging-header.h -sdk %clang-importer-sdk
+// RUN: not ls %t/tmp/*.pch >/dev/null 2>&1
+
+// Test -emit-pch invocation but with a persistent PCH
+// RUN: %target-swift-frontend -emit-pch -pch-output-dir %t/pch %S/../Inputs/c-bridging-header.h -sdk %clang-importer-sdk
+// RUN: %target-typecheck-verify-swift -internal-import-bridging-header %S/../Inputs/c-bridging-header.h -pch-output-dir %t/pch -pch-disable-validation -sdk %clang-importer-sdk
+// RUN: ls %t/pch/*.pch >/dev/null 2>&1
+
+// Test implicit use of persistent PCH
+// RUN: %target-typecheck-verify-swift -internal-import-bridging-header %S/../Inputs/c-bridging-header.h -pch-output-dir %t/pch2 -sdk %clang-importer-sdk
+// RUN: ls %t/pch2/*.pch >/dev/null 2>&1
+
+// RUN: touch %t/header.with.dot.h
+// RUN: touch %t/test.swift
+// RUN: %target-swift-frontend -typecheck %t/test.swift -internal-import-bridging-header %t/header.with.dot.h -pch-output-dir %t/pch_with_dot -module-cache-path %t/mcp1 -sdk %clang-importer-sdk
+// RUN: %target-swift-frontend -typecheck %t/test.swift -internal-import-bridging-header %t/header.with.dot.h -pch-output-dir %t/pch_with_dot -module-cache-path %t/mcp2 -sdk %clang-importer-sdk
+// RUN: ls %t/pch_with_dot/*swift*clang*.pch | count 2
+
+// Test the driver-automated version using persistent PCH
+// RUN: %target-swiftc_driver -typecheck -save-temps %s -internal-import-bridging-header %S/../Inputs/c-bridging-header.h -pch-output-dir %t/pch3 -sdk %clang-importer-sdk
+// RUN: ls %t/pch3/*.pch >/dev/null 2>&1
+// RUN: llvm-objdump --raw-clang-ast %t/pch3/*.pch | llvm-bcanalyzer -dump | %FileCheck %s -check-prefix=PERSISTENT
+// PERSISTENT: ORIGINAL_FILE{{.*}}Inputs/c-bridging-header.h
+
+// Test that -pch-disable-validation works in that it won't implicitly create a PCH
+// RUN: not %target-swift-frontend -typecheck %s -internal-import-bridging-header %S/../Inputs/c-bridging-header.h -pch-output-dir %t/no-pch -pch-disable-validation -sdk %clang-importer-sdk 2>&1 | %FileCheck %s -check-prefix=NO-VALIDATION
+// NO-VALIDATION: PCH file {{.*}} not found
+
+// UNSUPPORTED: OS=windows-msvc
+
+func getX(point: MyPoint) -> Double { point.x }
diff --git a/test/ClangImporter/InternalBridgingHeader/serialization.swift b/test/ClangImporter/InternalBridgingHeader/serialization.swift
new file mode 100644
index 0000000000000..499d2b883a4ce
--- /dev/null
+++ b/test/ClangImporter/InternalBridgingHeader/serialization.swift
@@ -0,0 +1,48 @@
+// RUN: %empty-directory(%t)
+
+// Stage in the headers we need
+// RUN: mkdir %t/headers
+// RUN: cp %S/../Inputs/c-bridging-header.h %t/headers
+
+// RUN: mkdir %t/src
+// RUN: split-file %s %t/src
+
+// Build a module
+// RUN: mkdir %t/modules
+// RUN: %target-swift-frontend -internal-import-bridging-header %t/headers/c-bridging-header.h -sdk %clang-importer-sdk -emit-module -o %t/modules/MyModule.swiftmodule %t/src/MyModule.swift
+
+// Check that there's no serialized bridging header in the module file.
+// RUN: llvm-bcanalyzer -dump %t/modules/MyModule.swiftmodule | %FileCheck -check-prefix MODULE-FILE %s
+
+// Use the module.
+// RUN: %target-swift-frontend -typecheck -sdk %clang-importer-sdk -I %t/modules %t/src/MyClient.swift
+
+// Delete the bridging header, and again use the module.
+// RUN: rm %t/headers/c-bridging-header.h
+// RUN: %target-swift-frontend -typecheck -sdk %clang-importer-sdk -I %t/modules %t/src/MyClient.swift
+
+//--- MyModule.swift
+func getRed() -> Color { red }
+
+func getX(point: MyPoint) -> Double { point.x }
+
+public func f() {
+  _ = getRed()
+}
+
+//--- MyClient.swift
+
+import MyModule
+
+func g() {
+  f()
+}
+
+
+// MODULE-FILE-NOT: IMPORTED_HEADER
+// MODULE-FILE-NOT: IMPORTED_HEADER_CONTENTS
+
+// MODULE-FILE: SEARCH_PATH
+
+// MODULE-FILE-NOT: IMPORTED_HEADER
+// MODULE-FILE-NOT: IMPORTED_HEADER_CONTENTS
diff --git a/test/Driver/bridging-pch.swift b/test/Driver/bridging-pch.swift
index 522303fe7c82d..2f50b15d3a36d 100644
--- a/test/Driver/bridging-pch.swift
+++ b/test/Driver/bridging-pch.swift
@@ -6,63 +6,63 @@
 // YESPCHACT: 2: input, "{{.*}}bridging-pch.swift", swift
 // YESPCHACT: 3: compile, {2, 1}, none
 
-// RUN: %target-build-swift -typecheck -disable-bridging-pch -driver-print-actions -import-objc-header %S/Inputs/bridging-header.h %s 2>&1 | %FileCheck %s -check-prefix=NOPCHACT
+// RUN: %target-build-swift -typecheck -disable-bridging-pch -driver-print-actions -import-bridging-header %S/Inputs/bridging-header.h %s 2>&1 | %FileCheck %s -check-prefix=NOPCHACT
 // NOPCHACT: 0: input, "{{.*}}bridging-pch.swift", swift
 // NOPCHACT: 1: compile, {0}, none
 
-// RUN: %target-build-swift -typecheck -driver-print-jobs -import-objc-header %S/Inputs/bridging-header.h %s 2>&1 | %FileCheck %s -check-prefix=YESPCHJOB
+// RUN: %target-build-swift -typecheck -driver-print-jobs -import-bridging-header %S/Inputs/bridging-header.h %s 2>&1 | %FileCheck %s -check-prefix=YESPCHJOB
 // YESPCHJOB: {{.*}}swift{{(c|c-legacy-driver|-frontend)?(\.exe)?"?}} -frontend {{.*}} -emit-pch -o {{.*}}bridging-header-{{.*}}.pch
-// YESPCHJOB: {{.*}}swift{{(c|c-legacy-driver|-frontend)?(\.exe)?"?}} -frontend {{.*}} -import-objc-header {{.*}}bridging-header-{{.*}}.pch
+// YESPCHJOB: {{.*}}swift{{(c|c-legacy-driver|-frontend)?(\.exe)?"?}} -frontend {{.*}} -import-bridging-header {{.*}}bridging-header-{{.*}}.pch
 
-// RUN: %target-build-swift -typecheck -disable-bridging-pch  -driver-print-jobs -import-objc-header %S/Inputs/bridging-header.h %s 2>&1 | %FileCheck %s -check-prefix=NOPCHJOB
-// NOPCHJOB: {{.*}}swift{{(c|c-legacy-driver|-frontend)?(\.exe)?"?}} -frontend {{.*}} -import-objc-header {{.*}}Inputs/bridging-header.h
+// RUN: %target-build-swift -typecheck -disable-bridging-pch  -driver-print-jobs -import-bridging-header %S/Inputs/bridging-header.h %s 2>&1 | %FileCheck %s -check-prefix=NOPCHJOB
+// NOPCHJOB: {{.*}}swift{{(c|c-legacy-driver|-frontend)?(\.exe)?"?}} -frontend {{.*}} -import-bridging-header {{.*}}Inputs/bridging-header.h
 
-// RUN: %target-build-swift -typecheck -driver-print-jobs -index-store-path %t/idx -import-objc-header %S/Inputs/bridging-header.h %s 2>&1 | %FileCheck %s -check-prefix=INDEXSTORE
+// RUN: %target-build-swift -typecheck -driver-print-jobs -index-store-path %t/idx -import-bridging-header %S/Inputs/bridging-header.h %s 2>&1 | %FileCheck %s -check-prefix=INDEXSTORE
 // INDEXSTORE: {{.*}}swift{{(c|c-legacy-driver|-frontend)?(\.exe)?"?}} -frontend {{.*}} -index-store-path {{.*}}/idx{{"?}} -emit-pch -o {{.*}}bridging-header-{{.*}}.pch
 
 // RUN: echo "{\"\": {\"swift-dependencies\": \"%/t/master.swiftdeps\"}, \"%/s\": {\"swift-dependencies\": \"%/t/bridging-header.swiftdeps\"}}" > %t.json
-// RUN: %target-build-swift -typecheck -incremental -enable-bridging-pch -output-file-map %t.json -import-objc-header %S/Inputs/bridging-header.h %s
+// RUN: %target-build-swift -typecheck -incremental -enable-bridging-pch -output-file-map %t.json -import-bridging-header %S/Inputs/bridging-header.h %s
 
 // RUN: mkdir %t/tmp
-// RUN: env TMP="%t/tmp/" TMPDIR="%t/tmp/" not %target-build-swift -typecheck -import-objc-header %S/../Inputs/empty.h -driver-use-frontend-path "%{python.unquoted};%S/Inputs/crash-after-generating-pch.py" -v %s
+// RUN: env TMP="%t/tmp/" TMPDIR="%t/tmp/" not %target-build-swift -typecheck -import-bridging-header %S/../Inputs/empty.h -driver-use-frontend-path "%{python.unquoted};%S/Inputs/crash-after-generating-pch.py" -v %s
 // RUN: ls %/t/tmp/ | grep .*pch
 
 // Test persistent PCH
 
-// RUN: %target-build-swift -typecheck -driver-print-actions -import-objc-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch %s 2>&1 | %FileCheck %s -check-prefix=PERSISTENT-YESPCHACT
+// RUN: %target-build-swift -typecheck -driver-print-actions -import-bridging-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch %s 2>&1 | %FileCheck %s -check-prefix=PERSISTENT-YESPCHACT
 // PERSISTENT-YESPCHACT: 0: input, "{{.*}}Inputs/bridging-header.h", clang-header
 // PERSISTENT-YESPCHACT: 1: generate-pch, {0}, none
 // PERSISTENT-YESPCHACT: 2: input, "{{.*}}bridging-pch.swift", swift
 // PERSISTENT-YESPCHACT: 3: compile, {2, 1}, none
 
-// RUN: %target-build-swift -c -driver-print-actions -embed-bitcode -import-objc-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch %s 2>&1 | %FileCheck %s -check-prefix=PERSISTENT-YESPCHACTBC
+// RUN: %target-build-swift -c -driver-print-actions -embed-bitcode -import-bridging-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch %s 2>&1 | %FileCheck %s -check-prefix=PERSISTENT-YESPCHACTBC
 // PERSISTENT-YESPCHACTBC: 0: input, "{{.*}}Inputs/bridging-header.h", clang-header
 // PERSISTENT-YESPCHACTBC: 1: generate-pch, {0}, none
 // PERSISTENT-YESPCHACTBC: 2: input, "{{.*}}bridging-pch.swift", swift
 // PERSISTENT-YESPCHACTBC: 3: compile, {2, 1}, llvm-bc
 
-// RUN: %target-build-swift -typecheck -disable-bridging-pch -driver-print-actions -import-objc-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch %s 2>&1 | %FileCheck %s -check-prefix=NOPCHACT
+// RUN: %target-build-swift -typecheck -disable-bridging-pch -driver-print-actions -import-bridging-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch %s 2>&1 | %FileCheck %s -check-prefix=NOPCHACT
 
-// RUN: %target-build-swift -typecheck -driver-print-jobs -import-objc-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch -disable-bridging-pch %s 2>&1 | %FileCheck %s -check-prefix=PERSISTENT-DISABLED-YESPCHJOB
-// RUN: %target-build-swift -typecheck -driver-print-jobs -import-objc-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch -whole-module-optimization -disable-bridging-pch %s 2>&1 | %FileCheck %s -check-prefix=PERSISTENT-DISABLED-YESPCHJOB
+// RUN: %target-build-swift -typecheck -driver-print-jobs -import-bridging-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch -disable-bridging-pch %s 2>&1 | %FileCheck %s -check-prefix=PERSISTENT-DISABLED-YESPCHJOB
+// RUN: %target-build-swift -typecheck -driver-print-jobs -import-bridging-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch -whole-module-optimization -disable-bridging-pch %s 2>&1 | %FileCheck %s -check-prefix=PERSISTENT-DISABLED-YESPCHJOB
 // PERSISTENT-DISABLED-YESPCHJOB-NOT: -pch-output-dir
 
-// RUN: %target-build-swift -typecheck -driver-print-jobs -import-objc-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch -serialize-diagnostics %s 2>&1 | %FileCheck %s -check-prefix=PERSISTENT-YESPCHJOB-DIAG1
+// RUN: %target-build-swift -typecheck -driver-print-jobs -import-bridging-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch -serialize-diagnostics %s 2>&1 | %FileCheck %s -check-prefix=PERSISTENT-YESPCHJOB-DIAG1
 // PERSISTENT-YESPCHJOB-DIAG1: {{.*}}swift{{(c|c-legacy-driver|-frontend)?(\.exe)?"?}} -frontend {{.*}} -serialize-diagnostics-path {{.*}}bridging-header-{{.*}}.dia{{"?}} {{.*}} -emit-pch -pch-output-dir {{.*}}/pch
 
-// RUN: %target-build-swift -typecheck -driver-print-jobs -import-objc-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch-out-dir -serialize-diagnostics %s -emit-module -emit-module-path /module-path-dir 2>&1 | %FileCheck %s -check-prefix=PERSISTENT-YESPCHJOB-DIAG2
+// RUN: %target-build-swift -typecheck -driver-print-jobs -import-bridging-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch-out-dir -serialize-diagnostics %s -emit-module -emit-module-path /module-path-dir 2>&1 | %FileCheck %s -check-prefix=PERSISTENT-YESPCHJOB-DIAG2
 // PERSISTENT-YESPCHJOB-DIAG2: {{.*}}swift{{(c|c-legacy-driver|-frontend)?(\.exe)?"?}} -frontend {{.*}} -serialize-diagnostics-path {{.*}}/pch-out-dir{{/|\\\\}}bridging-header-{{.*}}.dia{{"?}} {{.*}} -emit-pch -pch-output-dir {{.*}}/pch-out-dir
 
-// RUN: %target-build-swift -typecheck -import-objc-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch -parseable-output -driver-skip-execution %s 2>&1 | %FileCheck %s -check-prefix=PERSISTENT-OUTPUT
+// RUN: %target-build-swift -typecheck -import-bridging-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch -parseable-output -driver-skip-execution %s 2>&1 | %FileCheck %s -check-prefix=PERSISTENT-OUTPUT
 // PERSISTENT-OUTPUT-NOT: "outputs": [
 
-// RUN: %target-build-swift -typecheck -driver-print-jobs -import-objc-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch -whole-module-optimization %s 2>&1 | %FileCheck %s -check-prefix=PERSISTENT-WMO-YESPCHJOB --implicit-check-not pch-disable-validation
-// PERSISTENT-WMO-YESPCHJOB: {{.*}}swift{{(c|c-legacy-driver|-frontend)?(\.exe)?"?}} -frontend {{.*}} -import-objc-header {{.*}}bridging-header.h{{"?}} -pch-output-dir {{.*}}/pch
+// RUN: %target-build-swift -typecheck -driver-print-jobs -import-bridging-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch -whole-module-optimization %s 2>&1 | %FileCheck %s -check-prefix=PERSISTENT-WMO-YESPCHJOB --implicit-check-not pch-disable-validation
+// PERSISTENT-WMO-YESPCHJOB: {{.*}}swift{{(c|c-legacy-driver|-frontend)?(\.exe)?"?}} -frontend {{.*}} -import-bridging-header {{.*}}bridging-header.h{{"?}} -pch-output-dir {{.*}}/pch
 
-// RUN: %target-build-swift -typecheck -disable-bridging-pch  -driver-print-jobs -import-objc-header %/S/Inputs/bridging-header.h -pch-output-dir %t/pch %/s 2>&1 | %FileCheck %s -check-prefix=NOPCHJOB
-// RUN: %target-build-swift -typecheck -incremental -enable-bridging-pch -output-file-map %t.json -import-objc-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch %s
+// RUN: %target-build-swift -typecheck -disable-bridging-pch  -driver-print-jobs -import-bridging-header %/S/Inputs/bridging-header.h -pch-output-dir %t/pch %/s 2>&1 | %FileCheck %s -check-prefix=NOPCHJOB
+// RUN: %target-build-swift -typecheck -incremental -enable-bridging-pch -output-file-map %t.json -import-bridging-header %S/Inputs/bridging-header.h -pch-output-dir %t/pch %s
 
-// RUN: %target-build-swift -### -typecheck -O -import-objc-header %S/Inputs/bridging-header.h %s 2>&1 | %FileCheck %s -check-prefix=OPTPCH
+// RUN: %target-build-swift -### -typecheck -O -import-bridging-header %S/Inputs/bridging-header.h %s 2>&1 | %FileCheck %s -check-prefix=OPTPCH
 // OPTPCH: swift{{(c|c-legacy-driver|-frontend)?(\.exe)?"?}} -frontend
 // OPTPCH-SAME: -O{{ }}
 // OPTPCH-SAME: -emit-pch
diff --git a/test/Driver/working-directory.swift b/test/Driver/working-directory.swift
index 26919e89d6472..b5ab72fab7f65 100644
--- a/test/Driver/working-directory.swift
+++ b/test/Driver/working-directory.swift
@@ -32,10 +32,10 @@
 // RUN: cd %t && %swiftc_driver -driver-print-jobs -working-directory %/S/Inputs -emit-executable %/s -L=. | %FileCheck %s -check-prefix=L_PATH
 // L_PATH: -L {{"?}}SOURCE_DIR/test/Driver/Inputs
 
-// RUN: cd %t && %swiftc_driver -driver-print-jobs -working-directory %/S/Inputs -c %/s -disable-bridging-pch -import-objc-header bridging-header.h | %FileCheck %s -check-prefix=OBJC_HEADER1
-// OBJC_HEADER1: -import-objc-header {{"?}}SOURCE_DIR/test/Driver/Inputs{{/|\\\\}}bridging-header.h
+// RUN: cd %t && %swiftc_driver -driver-print-jobs -working-directory %/S/Inputs -c %/s -disable-bridging-pch -import-bridging-header bridging-header.h | %FileCheck %s -check-prefix=OBJC_HEADER1
+// OBJC_HEADER1: -import-bridging-header {{"?}}SOURCE_DIR/test/Driver/Inputs{{/|\\\\}}bridging-header.h
 
-// RUN: cd %t && %swiftc_driver -driver-print-jobs -working-directory %/S/Inputs -c %/s -enable-bridging-pch -import-objc-header bridging-header.h | %FileCheck %s -check-prefix=OBJC_HEADER2
+// RUN: cd %t && %swiftc_driver -driver-print-jobs -working-directory %/S/Inputs -c %/s -enable-bridging-pch -import-bridging-header bridging-header.h | %FileCheck %s -check-prefix=OBJC_HEADER2
 // OBJC_HEADER2: SOURCE_DIR/test/Driver/Inputs{{/|\\\\}}bridging-header.h{{"? .*}}-emit-pch
 
 // RUN: cd %t && %swiftc_driver -driver-print-jobs -working-directory %/S/Inputs -c %/s -o main.o | %FileCheck %s -check-prefix=OUTPUT_OBJ