diff --git a/init/host_init_verifier.cpp b/init/host_init_verifier.cpp
index ef9a451..db127d3 100644
--- a/init/host_init_verifier.cpp
+++ b/init/host_init_verifier.cpp
@@ -25,6 +25,8 @@
 #include <fstream>
 #include <iostream>
 #include <iterator>
+#include <map>
+#include <set>
 #include <string>
 #include <vector>
 
@@ -51,6 +53,7 @@
 
 using namespace std::literals;
 
+using android::base::EndsWith;
 using android::base::ParseInt;
 using android::base::ReadFileToString;
 using android::base::Split;
@@ -61,6 +64,10 @@
 
 static std::vector<std::string> passwd_files;
 
+// NOTE: Keep this in sync with the order used by init.cpp LoadBootScripts()
+static const std::vector<std::string> partition_search_order =
+        std::vector<std::string>({"system", "system_ext", "odm", "vendor", "product"});
+
 static std::vector<std::pair<std::string, int>> GetVendorPasswd(const std::string& passwd_file) {
     std::string passwd;
     if (!ReadFileToString(passwd_file, &passwd)) {
@@ -148,13 +155,24 @@
 #include "generated_stub_builtin_function_map.h"
 
 void PrintUsage() {
-    std::cout << "usage: host_init_verifier [options] <init rc file>\n"
-                 "\n"
-                 "Tests an init script for correctness\n"
-                 "\n"
-                 "-p FILE\tSearch this passwd file for users and groups\n"
-                 "--property_contexts=FILE\t Use this file for property_contexts\n"
-              << std::endl;
+    fprintf(stdout, R"(usage: host_init_verifier [options]
+
+Tests init script(s) for correctness.
+
+Generic options:
+  -p FILE                     Search this passwd file for users and groups.
+  --property_contexts=FILE    Use this file for property_contexts.
+
+Single script mode options:
+  [init rc file]              Positional argument; test this init script.
+
+Multiple script mode options:
+  --out_system=DIR            Path to the output product directory for the system partition.
+  --out_system_ext=DIR        Path to the output product directory for the system_ext partition.
+  --out_odm=DIR               Path to the output product directory for the odm partition.
+  --out_vendor=DIR            Path to the output product directory for the vendor partition.
+  --out_product=DIR           Path to the output product directory for the product partition.
+)");
 }
 
 Result<InterfaceInheritanceHierarchyMap> ReadInterfaceInheritanceHierarchy() {
@@ -203,12 +221,18 @@
     android::base::SetMinimumLogSeverity(android::base::ERROR);
 
     auto property_infos = std::vector<PropertyInfoEntry>();
+    std::map<std::string, std::string> partition_map;
 
     while (true) {
         static const char kPropertyContexts[] = "property-contexts=";
         static const struct option long_options[] = {
                 {"help", no_argument, nullptr, 'h'},
                 {kPropertyContexts, required_argument, nullptr, 0},
+                {"out_system", required_argument, nullptr, 0},
+                {"out_system_ext", required_argument, nullptr, 0},
+                {"out_odm", required_argument, nullptr, 0},
+                {"out_vendor", required_argument, nullptr, 0},
+                {"out_product", required_argument, nullptr, 0},
                 {nullptr, 0, nullptr, 0},
         };
 
@@ -224,6 +248,16 @@
                 if (long_options[option_index].name == kPropertyContexts) {
                     HandlePropertyContexts(optarg, &property_infos);
                 }
+                for (const auto& p : partition_search_order) {
+                    if (long_options[option_index].name == "out_" + p) {
+                        if (partition_map.find(p) != partition_map.end()) {
+                            PrintUsage();
+                            return EXIT_FAILURE;
+                        }
+                        partition_map[p] =
+                                EndsWith(optarg, "/") ? optarg : std::string(optarg) + "/";
+                    }
+                }
                 break;
             case 'h':
                 PrintUsage();
@@ -240,7 +274,9 @@
     argc -= optind;
     argv += optind;
 
-    if (argc != 1) {
+    // If provided, use the partition map to check multiple init rc files.
+    // Otherwise, check a single init rc file.
+    if ((!partition_map.empty() && argc != 0) || (partition_map.empty() && argc != 1)) {
         PrintUsage();
         return EXIT_FAILURE;
     }
@@ -262,24 +298,42 @@
 
     property_info_area = reinterpret_cast<const PropertyInfoArea*>(serialized_contexts.c_str());
 
+    if (!partition_map.empty()) {
+        std::vector<std::string> vendor_prefixes;
+        for (const auto& partition : {"vendor", "odm"}) {
+            if (partition_map.find(partition) != partition_map.end()) {
+                vendor_prefixes.push_back(partition_map.at(partition));
+            }
+        }
+        InitializeHostSubcontext(vendor_prefixes);
+    }
+
     const BuiltinFunctionMap& function_map = GetBuiltinFunctionMap();
     Action::set_function_map(&function_map);
     ActionManager& am = ActionManager::GetInstance();
     ServiceList& sl = ServiceList::GetInstance();
     Parser parser;
-    parser.AddSectionParser("service", std::make_unique<ServiceParser>(
-                                               &sl, nullptr, *interface_inheritance_hierarchy_map));
-    parser.AddSectionParser("on", std::make_unique<ActionParser>(&am, nullptr));
+    parser.AddSectionParser("service",
+                            std::make_unique<ServiceParser>(&sl, GetSubcontext(),
+                                                            *interface_inheritance_hierarchy_map));
+    parser.AddSectionParser("on", std::make_unique<ActionParser>(&am, GetSubcontext()));
     parser.AddSectionParser("import", std::make_unique<HostImportParser>());
 
-    if (!parser.ParseConfigFileInsecure(*argv)) {
-        LOG(ERROR) << "Failed to open init rc script '" << *argv << "'";
-        return EXIT_FAILURE;
+    if (!partition_map.empty()) {
+        for (const auto& p : partition_search_order) {
+            if (partition_map.find(p) != partition_map.end()) {
+                parser.ParseConfig(partition_map.at(p) + "etc/init");
+            }
+        }
+    } else {
+        if (!parser.ParseConfigFileInsecure(*argv)) {
+            LOG(ERROR) << "Failed to open init rc script '" << *argv << "'";
+            return EXIT_FAILURE;
+        }
     }
     size_t failures = parser.parse_error_count() + am.CheckAllCommands() + sl.CheckAllCommands();
     if (failures > 0) {
-        LOG(ERROR) << "Failed to parse init script '" << *argv << "' with " << failures
-                   << " errors";
+        LOG(ERROR) << "Failed to parse init scripts with " << failures << " error(s).";
         return EXIT_FAILURE;
     }
     return EXIT_SUCCESS;
diff --git a/init/service.cpp b/init/service.cpp
index 7b98392..766eb5d 100644
--- a/init/service.cpp
+++ b/init/service.cpp
@@ -154,6 +154,7 @@
                  .priority = 0},
       namespaces_{.flags = namespace_flags},
       seclabel_(seclabel),
+      subcontext_(subcontext_for_restart_commands),
       onrestart_(false, subcontext_for_restart_commands, "<Service '" + name + "' onrestart>", 0,
                  "onrestart", {}),
       oom_score_adjust_(DEFAULT_OOM_SCORE_ADJUST),
diff --git a/init/service.h b/init/service.h
index bc5c90f..aee1e5d 100644
--- a/init/service.h
+++ b/init/service.h
@@ -137,6 +137,7 @@
             flags_ &= ~SVC_ONESHOT;
         }
     }
+    Subcontext* subcontext() const { return subcontext_; }
 
   private:
     void NotifyStateChange(const std::string& new_state) const;
@@ -168,6 +169,7 @@
     std::vector<FileDescriptor> files_;
     std::vector<std::pair<std::string, std::string>> environment_vars_;
 
+    Subcontext* subcontext_;
     Action onrestart_;  // Commands to execute on restart.
 
     std::vector<std::string> writepid_files_;
diff --git a/init/service_parser.cpp b/init/service_parser.cpp
index 97621da..57c311a 100644
--- a/init/service_parser.cpp
+++ b/init/service_parser.cpp
@@ -657,6 +657,14 @@
                            << "' with a config in APEX";
         }
 
+        std::string context = service_->subcontext() ? service_->subcontext()->context() : "";
+        std::string old_context =
+                old_service->subcontext() ? old_service->subcontext()->context() : "";
+        if (context != old_context) {
+            return Error() << "service '" << service_->name() << "' overrides another service "
+                           << "across the treble boundary.";
+        }
+
         service_list_->RemoveService(*old_service);
         old_service = nullptr;
     }
diff --git a/init/subcontext.cpp b/init/subcontext.cpp
index dc2455e..f1fbffe 100644
--- a/init/subcontext.cpp
+++ b/init/subcontext.cpp
@@ -342,6 +342,9 @@
                 new Subcontext(std::vector<std::string>{"/vendor", "/odm"}, kVendorContext));
     }
 }
+void InitializeHostSubcontext(std::vector<std::string> vendor_prefixes) {
+    subcontext.reset(new Subcontext(vendor_prefixes, kVendorContext, /*host=*/true));
+}
 
 Subcontext* GetSubcontext() {
     return subcontext.get();
diff --git a/init/subcontext.h b/init/subcontext.h
index 788d3be..cb4138e 100644
--- a/init/subcontext.h
+++ b/init/subcontext.h
@@ -36,9 +36,11 @@
 
 class Subcontext {
   public:
-    Subcontext(std::vector<std::string> path_prefixes, std::string context)
+    Subcontext(std::vector<std::string> path_prefixes, std::string context, bool host = false)
         : path_prefixes_(std::move(path_prefixes)), context_(std::move(context)), pid_(0) {
-        Fork();
+        if (!host) {
+            Fork();
+        }
     }
 
     Result<void> Execute(const std::vector<std::string>& args);
@@ -61,6 +63,7 @@
 
 int SubcontextMain(int argc, char** argv, const BuiltinFunctionMap* function_map);
 void InitializeSubcontext();
+void InitializeHostSubcontext(std::vector<std::string> vendor_prefixes);
 Subcontext* GetSubcontext();
 bool SubcontextChildReap(pid_t pid);
 void SubcontextTerminate();