diff --git a/.github/workflows/pr-auto-tag-and-check-title.yaml b/.github/workflows/pr-auto-tag.yaml
similarity index 57%
rename from .github/workflows/pr-auto-tag-and-check-title.yaml
rename to .github/workflows/pr-auto-tag.yaml
index 2bd85cf3034..c0e440b7c44 100644
--- a/.github/workflows/pr-auto-tag-and-check-title.yaml
+++ b/.github/workflows/pr-auto-tag.yaml
@@ -1,4 +1,4 @@
-name: PR Title Check & Tag
+name: PR Auto Tag
 on:
   pull_request_target:
     types: [opened, reopened, synchronize, edited]
@@ -17,16 +17,3 @@ jobs:
       with:
         repo-token: "${{ secrets.GITHUB_TOKEN }}"
         sync-labels: ""
-
-  title-check:
-    permissions:
-      contents: read
-      pull-requests: write
-
-    runs-on: ubuntu-latest
-    steps:
-    - uses: thehanimo/pr-title-checker@v1.3.5
-      with:
-        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-        pass_on_octokit_error: false
-        configuration_path: ".github/pr_title_checker_config.json"
diff --git a/BUILD b/BUILD
index db7b0a5ac55..6e02ac04d52 100644
--- a/BUILD
+++ b/BUILD
@@ -30,8 +30,8 @@ licenses(["reciprocal"])
 package(
     default_visibility = ["//visibility:public"],
     features = [
-        "layering_check",
         "-parse_headers",
+        "layering_check",
     ],
 )
 
@@ -211,11 +211,11 @@ config_setting(
 python_config_settings()
 
 # This should be updated along with build_handwritten.yaml
-g_stands_for = "gjallarhorn"  # @unused
+g_stands_for = "grand"  # @unused
 
-core_version = "36.0.0"  # @unused
+core_version = "37.0.0"  # @unused
 
-version = "1.60.0-dev"  # @unused
+version = "1.61.0-dev"  # @unused
 
 GPR_PUBLIC_HDRS = [
     "include/grpc/support/alloc.h",
@@ -2941,6 +2941,7 @@ grpc_cc_library(
         "//src/core:lib/resolver/endpoint_addresses.h",
     ],
     external_deps = [
+        "absl/functional:function_ref",
         "absl/status",
         "absl/status:statusor",
         "absl/strings",
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 10ddf87db66..4c8979a56ec 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -25,11 +25,11 @@
 cmake_minimum_required(VERSION 3.8)
 
 set(PACKAGE_NAME          "grpc")
-set(PACKAGE_VERSION       "1.60.0-dev")
-set(gRPC_CORE_VERSION     "36.0.0")
-set(gRPC_CORE_SOVERSION   "36")
-set(gRPC_CPP_VERSION      "1.60.0-dev")
-set(gRPC_CPP_SOVERSION    "1.60")
+set(PACKAGE_VERSION       "1.61.0-dev")
+set(gRPC_CORE_VERSION     "37.0.0")
+set(gRPC_CORE_SOVERSION   "37")
+set(gRPC_CPP_VERSION      "1.61.0-dev")
+set(gRPC_CPP_SOVERSION    "1.61")
 set(PACKAGE_STRING        "${PACKAGE_NAME} ${PACKAGE_VERSION}")
 set(PACKAGE_TARNAME       "${PACKAGE_NAME}-${PACKAGE_VERSION}")
 set(PACKAGE_BUGREPORT     "https://github.com/grpc/grpc/issues/")
@@ -1109,6 +1109,7 @@ if(gRPC_BUILD_TESTS)
   add_dependencies(buildtests_cxx init_test)
   add_dependencies(buildtests_cxx initial_settings_frame_bad_client_test)
   add_dependencies(buildtests_cxx insecure_security_connector_test)
+  add_dependencies(buildtests_cxx inter_activity_latch_test)
   add_dependencies(buildtests_cxx inter_activity_pipe_test)
   add_dependencies(buildtests_cxx interceptor_list_test)
   add_dependencies(buildtests_cxx interop_client)
@@ -14936,6 +14937,39 @@ target_link_libraries(insecure_security_connector_test
 )
 
 
+endif()
+if(gRPC_BUILD_TESTS)
+
+add_executable(inter_activity_latch_test
+  test/core/promise/inter_activity_latch_test.cc
+)
+target_compile_features(inter_activity_latch_test PUBLIC cxx_std_14)
+target_include_directories(inter_activity_latch_test
+  PRIVATE
+    ${CMAKE_CURRENT_SOURCE_DIR}
+    ${CMAKE_CURRENT_SOURCE_DIR}/include
+    ${_gRPC_ADDRESS_SORTING_INCLUDE_DIR}
+    ${_gRPC_RE2_INCLUDE_DIR}
+    ${_gRPC_SSL_INCLUDE_DIR}
+    ${_gRPC_UPB_GENERATED_DIR}
+    ${_gRPC_UPB_GRPC_GENERATED_DIR}
+    ${_gRPC_UPB_INCLUDE_DIR}
+    ${_gRPC_XXHASH_INCLUDE_DIR}
+    ${_gRPC_ZLIB_INCLUDE_DIR}
+    third_party/googletest/googletest/include
+    third_party/googletest/googletest
+    third_party/googletest/googlemock/include
+    third_party/googletest/googlemock
+    ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(inter_activity_latch_test
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  gtest
+  grpc
+)
+
+
 endif()
 if(gRPC_BUILD_TESTS)
 
diff --git a/Makefile b/Makefile
index e61509270c2..4833a2944fe 100644
--- a/Makefile
+++ b/Makefile
@@ -410,8 +410,8 @@ E = @echo
 Q = @
 endif
 
-CORE_VERSION = 36.0.0
-CPP_VERSION = 1.60.0-dev
+CORE_VERSION = 37.0.0
+CPP_VERSION = 1.61.0-dev
 
 CPPFLAGS_NO_ARCH += $(addprefix -I, $(INCLUDES)) $(addprefix -D, $(DEFINES))
 CPPFLAGS += $(CPPFLAGS_NO_ARCH) $(ARCH_FLAGS)
@@ -447,7 +447,7 @@ SHARED_EXT_CORE = dll
 SHARED_EXT_CPP = dll
 
 SHARED_PREFIX =
-SHARED_VERSION_CORE = -36
+SHARED_VERSION_CORE = -37
 SHARED_VERSION_CPP = -1
 else ifeq ($(SYSTEM),Darwin)
 EXECUTABLE_SUFFIX =
@@ -814,8 +814,8 @@ $(LIBDIR)/$(CONFIG)/libaddress_sorting$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE):
 ifeq ($(SYSTEM),Darwin)
 	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -install_name $(SHARED_PREFIX)address_sorting$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) -dynamiclib -o $(LIBDIR)/$(CONFIG)/libaddress_sorting$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBADDRESS_SORTING_OBJS) $(LDLIBS)
 else
-	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libaddress_sorting.so.36 -o $(LIBDIR)/$(CONFIG)/libaddress_sorting$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBADDRESS_SORTING_OBJS) $(LDLIBS)
-	$(Q) ln -sf $(SHARED_PREFIX)address_sorting$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libaddress_sorting$(SHARED_VERSION_CORE).so.36
+	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libaddress_sorting.so.37 -o $(LIBDIR)/$(CONFIG)/libaddress_sorting$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBADDRESS_SORTING_OBJS) $(LDLIBS)
+	$(Q) ln -sf $(SHARED_PREFIX)address_sorting$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libaddress_sorting$(SHARED_VERSION_CORE).so.37
 	$(Q) ln -sf $(SHARED_PREFIX)address_sorting$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libaddress_sorting$(SHARED_VERSION_CORE).so
 endif
 endif
@@ -938,8 +938,8 @@ $(LIBDIR)/$(CONFIG)/libgpr$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE): $(LIBGPR_OB
 ifeq ($(SYSTEM),Darwin)
 	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -install_name $(SHARED_PREFIX)gpr$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) -dynamiclib -o $(LIBDIR)/$(CONFIG)/libgpr$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBGPR_OBJS) $(GRPC_ABSEIL_MERGE_LIBS) $(LDLIBS)
 else
-	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libgpr.so.36 -o $(LIBDIR)/$(CONFIG)/libgpr$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBGPR_OBJS) $(GRPC_ABSEIL_MERGE_LIBS) $(LDLIBS)
-	$(Q) ln -sf $(SHARED_PREFIX)gpr$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libgpr$(SHARED_VERSION_CORE).so.36
+	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libgpr.so.37 -o $(LIBDIR)/$(CONFIG)/libgpr$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBGPR_OBJS) $(GRPC_ABSEIL_MERGE_LIBS) $(LDLIBS)
+	$(Q) ln -sf $(SHARED_PREFIX)gpr$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libgpr$(SHARED_VERSION_CORE).so.37
 	$(Q) ln -sf $(SHARED_PREFIX)gpr$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libgpr$(SHARED_VERSION_CORE).so
 endif
 endif
@@ -1848,8 +1848,8 @@ $(LIBDIR)/$(CONFIG)/libgrpc$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE): $(LIBGRPC_
 ifeq ($(SYSTEM),Darwin)
 	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -install_name $(SHARED_PREFIX)grpc$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) -dynamiclib -o $(LIBDIR)/$(CONFIG)/libgrpc$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBGRPC_OBJS) $(LIBDIR)/$(CONFIG)/libaddress_sorting.a $(LIBDIR)/$(CONFIG)/libgpr.a $(GRPC_ABSEIL_MERGE_LIBS) $(LIBDIR)/$(CONFIG)/libcares.a $(ZLIB_MERGE_LIBS) $(LIBDIR)/$(CONFIG)/libre2.a $(LIBDIR)/$(CONFIG)/libupb.a $(LIBDIR)/$(CONFIG)/libupb_textformat_lib.a $(LIBDIR)/$(CONFIG)/libupb_json_lib.a $(LIBDIR)/$(CONFIG)/libutf8_range_lib.a $(LIBDIR)/$(CONFIG)/libupb_collections_lib.a $(OPENSSL_MERGE_LIBS) $(LDLIBS_SECURE) $(LDLIBS)
 else
-	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libgrpc.so.36 -o $(LIBDIR)/$(CONFIG)/libgrpc$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBGRPC_OBJS) $(LIBDIR)/$(CONFIG)/libaddress_sorting.a $(LIBDIR)/$(CONFIG)/libgpr.a $(GRPC_ABSEIL_MERGE_LIBS) $(LIBDIR)/$(CONFIG)/libcares.a $(ZLIB_MERGE_LIBS) $(LIBDIR)/$(CONFIG)/libre2.a $(LIBDIR)/$(CONFIG)/libupb.a $(LIBDIR)/$(CONFIG)/libupb_textformat_lib.a $(LIBDIR)/$(CONFIG)/libupb_json_lib.a $(LIBDIR)/$(CONFIG)/libutf8_range_lib.a $(LIBDIR)/$(CONFIG)/libupb_collections_lib.a $(OPENSSL_MERGE_LIBS) $(LDLIBS_SECURE) $(LDLIBS)
-	$(Q) ln -sf $(SHARED_PREFIX)grpc$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libgrpc$(SHARED_VERSION_CORE).so.36
+	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libgrpc.so.37 -o $(LIBDIR)/$(CONFIG)/libgrpc$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBGRPC_OBJS) $(LIBDIR)/$(CONFIG)/libaddress_sorting.a $(LIBDIR)/$(CONFIG)/libgpr.a $(GRPC_ABSEIL_MERGE_LIBS) $(LIBDIR)/$(CONFIG)/libcares.a $(ZLIB_MERGE_LIBS) $(LIBDIR)/$(CONFIG)/libre2.a $(LIBDIR)/$(CONFIG)/libupb.a $(LIBDIR)/$(CONFIG)/libupb_textformat_lib.a $(LIBDIR)/$(CONFIG)/libupb_json_lib.a $(LIBDIR)/$(CONFIG)/libutf8_range_lib.a $(LIBDIR)/$(CONFIG)/libupb_collections_lib.a $(OPENSSL_MERGE_LIBS) $(LDLIBS_SECURE) $(LDLIBS)
+	$(Q) ln -sf $(SHARED_PREFIX)grpc$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libgrpc$(SHARED_VERSION_CORE).so.37
 	$(Q) ln -sf $(SHARED_PREFIX)grpc$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libgrpc$(SHARED_VERSION_CORE).so
 endif
 endif
@@ -2364,8 +2364,8 @@ $(LIBDIR)/$(CONFIG)/libgrpc_unsecure$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE): $
 ifeq ($(SYSTEM),Darwin)
 	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -install_name $(SHARED_PREFIX)grpc_unsecure$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) -dynamiclib -o $(LIBDIR)/$(CONFIG)/libgrpc_unsecure$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBGRPC_UNSECURE_OBJS) $(LIBDIR)/$(CONFIG)/libaddress_sorting.a $(LIBDIR)/$(CONFIG)/libgpr.a $(GRPC_ABSEIL_MERGE_LIBS) $(LIBDIR)/$(CONFIG)/libcares.a $(ZLIB_MERGE_LIBS) $(LIBDIR)/$(CONFIG)/libutf8_range_lib.a $(LIBDIR)/$(CONFIG)/libupb.a $(LIBDIR)/$(CONFIG)/libupb_collections_lib.a $(LDLIBS)
 else
-	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libgrpc_unsecure.so.36 -o $(LIBDIR)/$(CONFIG)/libgrpc_unsecure$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBGRPC_UNSECURE_OBJS) $(LIBDIR)/$(CONFIG)/libaddress_sorting.a $(LIBDIR)/$(CONFIG)/libgpr.a $(GRPC_ABSEIL_MERGE_LIBS) $(LIBDIR)/$(CONFIG)/libcares.a $(ZLIB_MERGE_LIBS) $(LIBDIR)/$(CONFIG)/libutf8_range_lib.a $(LIBDIR)/$(CONFIG)/libupb.a $(LIBDIR)/$(CONFIG)/libupb_collections_lib.a $(LDLIBS)
-	$(Q) ln -sf $(SHARED_PREFIX)grpc_unsecure$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libgrpc_unsecure$(SHARED_VERSION_CORE).so.36
+	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libgrpc_unsecure.so.37 -o $(LIBDIR)/$(CONFIG)/libgrpc_unsecure$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBGRPC_UNSECURE_OBJS) $(LIBDIR)/$(CONFIG)/libaddress_sorting.a $(LIBDIR)/$(CONFIG)/libgpr.a $(GRPC_ABSEIL_MERGE_LIBS) $(LIBDIR)/$(CONFIG)/libcares.a $(ZLIB_MERGE_LIBS) $(LIBDIR)/$(CONFIG)/libutf8_range_lib.a $(LIBDIR)/$(CONFIG)/libupb.a $(LIBDIR)/$(CONFIG)/libupb_collections_lib.a $(LDLIBS)
+	$(Q) ln -sf $(SHARED_PREFIX)grpc_unsecure$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libgrpc_unsecure$(SHARED_VERSION_CORE).so.37
 	$(Q) ln -sf $(SHARED_PREFIX)grpc_unsecure$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libgrpc_unsecure$(SHARED_VERSION_CORE).so
 endif
 endif
@@ -2431,8 +2431,8 @@ $(LIBDIR)/$(CONFIG)/libre2$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE): $(LIBRE2_OB
 ifeq ($(SYSTEM),Darwin)
 	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -install_name $(SHARED_PREFIX)re2$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) -dynamiclib -o $(LIBDIR)/$(CONFIG)/libre2$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBRE2_OBJS) $(LDLIBS)
 else
-	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libre2.so.36 -o $(LIBDIR)/$(CONFIG)/libre2$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBRE2_OBJS) $(LDLIBS)
-	$(Q) ln -sf $(SHARED_PREFIX)re2$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libre2$(SHARED_VERSION_CORE).so.36
+	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libre2.so.37 -o $(LIBDIR)/$(CONFIG)/libre2$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBRE2_OBJS) $(LDLIBS)
+	$(Q) ln -sf $(SHARED_PREFIX)re2$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libre2$(SHARED_VERSION_CORE).so.37
 	$(Q) ln -sf $(SHARED_PREFIX)re2$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libre2$(SHARED_VERSION_CORE).so
 endif
 endif
@@ -2479,8 +2479,8 @@ $(LIBDIR)/$(CONFIG)/libupb$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE): $(LIBUPB_OB
 ifeq ($(SYSTEM),Darwin)
 	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -install_name $(SHARED_PREFIX)upb$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) -dynamiclib -o $(LIBDIR)/$(CONFIG)/libupb$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBUPB_OBJS) $(LDLIBS)
 else
-	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libupb.so.36 -o $(LIBDIR)/$(CONFIG)/libupb$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBUPB_OBJS) $(LDLIBS)
-	$(Q) ln -sf $(SHARED_PREFIX)upb$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libupb$(SHARED_VERSION_CORE).so.36
+	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libupb.so.37 -o $(LIBDIR)/$(CONFIG)/libupb$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBUPB_OBJS) $(LDLIBS)
+	$(Q) ln -sf $(SHARED_PREFIX)upb$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libupb$(SHARED_VERSION_CORE).so.37
 	$(Q) ln -sf $(SHARED_PREFIX)upb$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libupb$(SHARED_VERSION_CORE).so
 endif
 endif
@@ -2535,8 +2535,8 @@ $(LIBDIR)/$(CONFIG)/libupb_collections_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CO
 ifeq ($(SYSTEM),Darwin)
 	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -install_name $(SHARED_PREFIX)upb_collections_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) -dynamiclib -o $(LIBDIR)/$(CONFIG)/libupb_collections_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBUPB_COLLECTIONS_LIB_OBJS) $(LDLIBS)
 else
-	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libupb_collections_lib.so.36 -o $(LIBDIR)/$(CONFIG)/libupb_collections_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBUPB_COLLECTIONS_LIB_OBJS) $(LDLIBS)
-	$(Q) ln -sf $(SHARED_PREFIX)upb_collections_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libupb_collections_lib$(SHARED_VERSION_CORE).so.36
+	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libupb_collections_lib.so.37 -o $(LIBDIR)/$(CONFIG)/libupb_collections_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBUPB_COLLECTIONS_LIB_OBJS) $(LDLIBS)
+	$(Q) ln -sf $(SHARED_PREFIX)upb_collections_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libupb_collections_lib$(SHARED_VERSION_CORE).so.37
 	$(Q) ln -sf $(SHARED_PREFIX)upb_collections_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libupb_collections_lib$(SHARED_VERSION_CORE).so
 endif
 endif
@@ -2626,8 +2626,8 @@ $(LIBDIR)/$(CONFIG)/libupb_json_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE): $(
 ifeq ($(SYSTEM),Darwin)
 	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -install_name $(SHARED_PREFIX)upb_json_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) -dynamiclib -o $(LIBDIR)/$(CONFIG)/libupb_json_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBUPB_JSON_LIB_OBJS) $(LIBDIR)/$(CONFIG)/libutf8_range_lib.a $(LDLIBS)
 else
-	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libupb_json_lib.so.36 -o $(LIBDIR)/$(CONFIG)/libupb_json_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBUPB_JSON_LIB_OBJS) $(LIBDIR)/$(CONFIG)/libutf8_range_lib.a $(LDLIBS)
-	$(Q) ln -sf $(SHARED_PREFIX)upb_json_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libupb_json_lib$(SHARED_VERSION_CORE).so.36
+	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libupb_json_lib.so.37 -o $(LIBDIR)/$(CONFIG)/libupb_json_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBUPB_JSON_LIB_OBJS) $(LIBDIR)/$(CONFIG)/libutf8_range_lib.a $(LDLIBS)
+	$(Q) ln -sf $(SHARED_PREFIX)upb_json_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libupb_json_lib$(SHARED_VERSION_CORE).so.37
 	$(Q) ln -sf $(SHARED_PREFIX)upb_json_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libupb_json_lib$(SHARED_VERSION_CORE).so
 endif
 endif
@@ -2716,8 +2716,8 @@ $(LIBDIR)/$(CONFIG)/libupb_textformat_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_COR
 ifeq ($(SYSTEM),Darwin)
 	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -install_name $(SHARED_PREFIX)upb_textformat_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) -dynamiclib -o $(LIBDIR)/$(CONFIG)/libupb_textformat_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBUPB_TEXTFORMAT_LIB_OBJS) $(LIBDIR)/$(CONFIG)/libutf8_range_lib.a $(LDLIBS)
 else
-	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libupb_textformat_lib.so.36 -o $(LIBDIR)/$(CONFIG)/libupb_textformat_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBUPB_TEXTFORMAT_LIB_OBJS) $(LIBDIR)/$(CONFIG)/libutf8_range_lib.a $(LDLIBS)
-	$(Q) ln -sf $(SHARED_PREFIX)upb_textformat_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libupb_textformat_lib$(SHARED_VERSION_CORE).so.36
+	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libupb_textformat_lib.so.37 -o $(LIBDIR)/$(CONFIG)/libupb_textformat_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBUPB_TEXTFORMAT_LIB_OBJS) $(LIBDIR)/$(CONFIG)/libutf8_range_lib.a $(LDLIBS)
+	$(Q) ln -sf $(SHARED_PREFIX)upb_textformat_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libupb_textformat_lib$(SHARED_VERSION_CORE).so.37
 	$(Q) ln -sf $(SHARED_PREFIX)upb_textformat_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libupb_textformat_lib$(SHARED_VERSION_CORE).so
 endif
 endif
@@ -2764,8 +2764,8 @@ $(LIBDIR)/$(CONFIG)/libutf8_range_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE):
 ifeq ($(SYSTEM),Darwin)
 	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -install_name $(SHARED_PREFIX)utf8_range_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) -dynamiclib -o $(LIBDIR)/$(CONFIG)/libutf8_range_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBUTF8_RANGE_LIB_OBJS) $(LDLIBS)
 else
-	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libutf8_range_lib.so.36 -o $(LIBDIR)/$(CONFIG)/libutf8_range_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBUTF8_RANGE_LIB_OBJS) $(LDLIBS)
-	$(Q) ln -sf $(SHARED_PREFIX)utf8_range_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libutf8_range_lib$(SHARED_VERSION_CORE).so.36
+	$(Q) $(LDXX) $(LDFLAGS) -L$(LIBDIR)/$(CONFIG) -shared -Wl,-soname,libutf8_range_lib.so.37 -o $(LIBDIR)/$(CONFIG)/libutf8_range_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBUTF8_RANGE_LIB_OBJS) $(LDLIBS)
+	$(Q) ln -sf $(SHARED_PREFIX)utf8_range_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libutf8_range_lib$(SHARED_VERSION_CORE).so.37
 	$(Q) ln -sf $(SHARED_PREFIX)utf8_range_lib$(SHARED_VERSION_CORE).$(SHARED_EXT_CORE) $(LIBDIR)/$(CONFIG)/libutf8_range_lib$(SHARED_VERSION_CORE).so
 endif
 endif
diff --git a/OWNERS b/OWNERS
deleted file mode 100644
index cdbc4bec0ed..00000000000
--- a/OWNERS
+++ /dev/null
@@ -1,3 +0,0 @@
-# Top level ownership
-@markdroth **/OWNERS
-@a11r **/OWNERS
diff --git a/_metadata.py b/_metadata.py
index a21f0695e23..cdc48b2f276 100644
--- a/_metadata.py
+++ b/_metadata.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/_metadata.py.template`!!!
 
-__version__ = """1.60.0.dev0"""
+__version__ = """1.61.0.dev0"""
diff --git a/bazel/googleapis.BUILD b/bazel/googleapis.BUILD
index dc7e05f7424..ee9473b1526 100644
--- a/bazel/googleapis.BUILD
+++ b/bazel/googleapis.BUILD
@@ -15,7 +15,7 @@
 licenses(["notice"])
 
 package(
-    default_visibility = ["//visibility:public"]
+    default_visibility = ["//visibility:public"],
 )
 
 # This is needed for the dependency on google_cloud_cpp to work.
diff --git a/build_autogenerated.yaml b/build_autogenerated.yaml
index f437de380a7..bd2a9aa0bbd 100644
--- a/build_autogenerated.yaml
+++ b/build_autogenerated.yaml
@@ -10835,6 +10835,20 @@ targets:
   deps:
   - gtest
   - grpc_test_util
+- name: inter_activity_latch_test
+  gtest: true
+  build: test
+  language: c++
+  headers:
+  - src/core/lib/promise/event_engine_wakeup_scheduler.h
+  - src/core/lib/promise/inter_activity_latch.h
+  - src/core/lib/promise/wait_set.h
+  src:
+  - test/core/promise/inter_activity_latch_test.cc
+  deps:
+  - gtest
+  - grpc
+  uses_polling: false
 - name: inter_activity_pipe_test
   gtest: true
   build: test
@@ -12434,7 +12448,9 @@ targets:
   gtest: true
   build: test
   language: c++
-  headers: []
+  headers:
+  - src/core/lib/promise/inter_activity_latch.h
+  - src/core/lib/promise/wait_set.h
   src:
   - test/core/promise/party_test.cc
   deps:
diff --git a/build_config.rb b/build_config.rb
index 43b209efe7b..a0dce5c6bc8 100644
--- a/build_config.rb
+++ b/build_config.rb
@@ -13,5 +13,5 @@
 # limitations under the License.
 
 module GrpcBuildConfig
-  CORE_WINDOWS_DLL = '/tmp/libs/opt/grpc-36.dll'
+  CORE_WINDOWS_DLL = '/tmp/libs/opt/grpc-37.dll'
 end
diff --git a/build_handwritten.yaml b/build_handwritten.yaml
index fc4811e96ec..a700fdd2da7 100644
--- a/build_handwritten.yaml
+++ b/build_handwritten.yaml
@@ -12,11 +12,11 @@ settings:
   '#08': Use "-preN" suffixes to identify pre-release versions
   '#09': Per-language overrides are possible with (eg) ruby_version tag here
   '#10': See the expand_version.py for all the quirks here
-  core_version: 36.0.0
+  core_version: 37.0.0
   csharp_major_version: 2
-  g_stands_for: gjallarhorn
+  g_stands_for: grand
   protobuf_version: 3.25.0
-  version: 1.60.0-dev
+  version: 1.61.0-dev
 configs:
   asan:
     CC: clang
diff --git a/config.m4 b/config.m4
index 7d94e19baa0..01455fdd842 100644
--- a/config.m4
+++ b/config.m4
@@ -1348,7 +1348,7 @@ if test "$PHP_GRPC" != "no"; then
     -D_HAS_EXCEPTIONS=0 -DNOMINMAX -DGRPC_ARES=0 \
     -DGRPC_POSIX_FORK_ALLOW_PTHREAD_ATFORK=1 \
     -DGRPC_XDS_USER_AGENT_NAME_SUFFIX='"\"PHP\""' \
-    -DGRPC_XDS_USER_AGENT_VERSION_SUFFIX='"\"1.60.0dev\""')
+    -DGRPC_XDS_USER_AGENT_VERSION_SUFFIX='"\"1.61.0dev\""')
 
   PHP_ADD_BUILD_DIR($ext_builddir/src/core/ext/filters/backend_metrics)
   PHP_ADD_BUILD_DIR($ext_builddir/src/core/ext/filters/census)
diff --git a/doc/g_stands_for.md b/doc/g_stands_for.md
index 1278143e2f0..6c4ab101081 100644
--- a/doc/g_stands_for.md
+++ b/doc/g_stands_for.md
@@ -59,4 +59,5 @@
 - 1.57 'g' stands for ['grounded'](https://github.com/grpc/grpc/tree/v1.57.x)
 - 1.58 'g' stands for ['goku'](https://github.com/grpc/grpc/tree/v1.58.x)
 - 1.59 'g' stands for ['generative'](https://github.com/grpc/grpc/tree/v1.59.x)
-- 1.60 'g' stands for ['gjallarhorn'](https://github.com/grpc/grpc/tree/master)
+- 1.60 'g' stands for ['gjallarhorn'](https://github.com/grpc/grpc/tree/v1.60.x)
+- 1.61 'g' stands for ['grand'](https://github.com/grpc/grpc/tree/master)
diff --git a/gRPC-C++.podspec b/gRPC-C++.podspec
index aed03261891..1d2d74a2782 100644
--- a/gRPC-C++.podspec
+++ b/gRPC-C++.podspec
@@ -22,7 +22,7 @@
 Pod::Spec.new do |s|
   s.name     = 'gRPC-C++'
   # TODO (mxyan): use version that match gRPC version when pod is stabilized
-  version = '1.60.0-dev'
+  version = '1.61.0-dev'
   s.version  = version
   s.summary  = 'gRPC C++ library'
   s.homepage = 'https://grpc.io'
diff --git a/gRPC-Core.podspec b/gRPC-Core.podspec
index cc836aa8179..2e787990646 100644
--- a/gRPC-Core.podspec
+++ b/gRPC-Core.podspec
@@ -21,7 +21,7 @@
 
 Pod::Spec.new do |s|
   s.name     = 'gRPC-Core'
-  version = '1.60.0-dev'
+  version = '1.61.0-dev'
   s.version  = version
   s.summary  = 'Core cross-platform gRPC library, written in C'
   s.homepage = 'https://grpc.io'
diff --git a/gRPC-ProtoRPC.podspec b/gRPC-ProtoRPC.podspec
index 93efa37861a..13c652e7795 100644
--- a/gRPC-ProtoRPC.podspec
+++ b/gRPC-ProtoRPC.podspec
@@ -21,7 +21,7 @@
 
 Pod::Spec.new do |s|
   s.name     = 'gRPC-ProtoRPC'
-  version = '1.60.0-dev'
+  version = '1.61.0-dev'
   s.version  = version
   s.summary  = 'RPC library for Protocol Buffers, based on gRPC'
   s.homepage = 'https://grpc.io'
diff --git a/gRPC-RxLibrary.podspec b/gRPC-RxLibrary.podspec
index b1f3f328f4d..cb28e76f547 100644
--- a/gRPC-RxLibrary.podspec
+++ b/gRPC-RxLibrary.podspec
@@ -21,7 +21,7 @@
 
 Pod::Spec.new do |s|
   s.name     = 'gRPC-RxLibrary'
-  version = '1.60.0-dev'
+  version = '1.61.0-dev'
   s.version  = version
   s.summary  = 'Reactive Extensions library for iOS/OSX.'
   s.homepage = 'https://grpc.io'
diff --git a/gRPC.podspec b/gRPC.podspec
index e917a3a4e36..2be61d98270 100644
--- a/gRPC.podspec
+++ b/gRPC.podspec
@@ -20,7 +20,7 @@
 
 Pod::Spec.new do |s|
   s.name     = 'gRPC'
-  version = '1.60.0-dev'
+  version = '1.61.0-dev'
   s.version  = version
   s.summary  = 'gRPC client library for iOS/OSX'
   s.homepage = 'https://grpc.io'
diff --git a/include/grpc/impl/channel_arg_names.h b/include/grpc/impl/channel_arg_names.h
index def07be248d..b4cece27c9e 100644
--- a/include/grpc/impl/channel_arg_names.h
+++ b/include/grpc/impl/channel_arg_names.h
@@ -15,7 +15,7 @@
 #ifndef GRPC_IMPL_CHANNEL_ARG_NAMES_H
 #define GRPC_IMPL_CHANNEL_ARG_NAMES_H
 
-// IWYU pragma: private, include "third_party/grpc/include/grpc/grpc.h"
+// IWYU pragma: private, include <grpc/grpc.h>
 // IWYU pragma: friend "src/.*"
 // IWYU pragma: friend "test/.*"
 
diff --git a/include/grpcpp/version_info.h b/include/grpcpp/version_info.h
index a1ee36a0fe3..85fb6219a70 100644
--- a/include/grpcpp/version_info.h
+++ b/include/grpcpp/version_info.h
@@ -19,9 +19,9 @@
 #define GRPCPP_VERSION_INFO_H
 
 #define GRPC_CPP_VERSION_MAJOR 1
-#define GRPC_CPP_VERSION_MINOR 60
+#define GRPC_CPP_VERSION_MINOR 61
 #define GRPC_CPP_VERSION_PATCH 0
 #define GRPC_CPP_VERSION_TAG "dev"
-#define GRPC_CPP_VERSION_STRING "1.60.0-dev"
+#define GRPC_CPP_VERSION_STRING "1.61.0-dev"
 
 #endif  // GRPCPP_VERSION_INFO_H
diff --git a/package.xml b/package.xml
index 94df95ed04d..4ff9ece3cdd 100644
--- a/package.xml
+++ b/package.xml
@@ -13,8 +13,8 @@
  <date>2019-09-24</date>
  <time>16:06:07</time>
  <version>
-  <release>1.60.0dev</release>
-  <api>1.60.0dev</api>
+  <release>1.61.0dev</release>
+  <api>1.61.0dev</api>
  </version>
  <stability>
   <release>beta</release>
@@ -22,7 +22,7 @@
  </stability>
  <license>Apache 2.0</license>
  <notes>
-- gRPC Core 1.60.0 update
+- gRPC Core 1.61.0 update
  </notes>
  <contents>
   <dir baseinstalldir="/" name="/">
diff --git a/src/core/BUILD b/src/core/BUILD
index 3df1d40375b..351f101b819 100644
--- a/src/core/BUILD
+++ b/src/core/BUILD
@@ -478,6 +478,7 @@ grpc_cc_library(
         "arena",
         "construct_destruct",
         "context",
+        "poll",
         "promise_factory",
         "promise_trace",
         "ref_counted",
@@ -874,6 +875,25 @@ grpc_cc_library(
     ],
 )
 
+grpc_cc_library(
+    name = "inter_activity_latch",
+    external_deps = [
+        "absl/base:core_headers",
+        "absl/strings",
+    ],
+    language = "c++",
+    public_hdrs = [
+        "lib/promise/inter_activity_latch.h",
+    ],
+    deps = [
+        "activity",
+        "poll",
+        "promise_trace",
+        "wait_set",
+        "//:gpr",
+    ],
+)
+
 grpc_cc_library(
     name = "interceptor_list",
     hdrs = [
@@ -4120,6 +4140,7 @@ grpc_cc_library(
     external_deps = [
         "absl/base:core_headers",
         "absl/container:inlined_vector",
+        "absl/functional:function_ref",
         "absl/status",
         "absl/status:statusor",
         "absl/strings",
@@ -4647,6 +4668,7 @@ grpc_cc_library(
         "ext/filters/client_channel/lb_policy/xds/xds_cluster_resolver.cc",
     ],
     external_deps = [
+        "absl/functional:function_ref",
         "absl/status",
         "absl/status:statusor",
         "absl/strings",
@@ -4669,6 +4691,7 @@ grpc_cc_library(
         "no_destruct",
         "pollset_set",
         "ref_counted_string",
+        "resolved_address",
         "validation_errors",
         "//:channel_arg_names",
         "//:config",
@@ -4817,6 +4840,7 @@ grpc_cc_library(
         "ext/filters/client_channel/lb_policy/address_filtering.h",
     ],
     external_deps = [
+        "absl/functional:function_ref",
         "absl/status:statusor",
         "absl/strings",
     ],
@@ -4825,6 +4849,7 @@ grpc_cc_library(
         "channel_args",
         "ref_counted",
         "ref_counted_string",
+        "resolved_address",
         "//:endpoint_addresses",
         "//:gpr_platform",
         "//:ref_counted_ptr",
@@ -4894,6 +4919,7 @@ grpc_cc_library(
         "lb_policy",
         "subchannel_interface",
         "//:debug_location",
+        "//:endpoint_addresses",
         "//:gpr",
         "//:grpc_base",
         "//:ref_counted_ptr",
@@ -4911,7 +4937,7 @@ grpc_cc_library(
         "ext/filters/client_channel/lb_policy/endpoint_list.h",
     ],
     external_deps = [
-        "absl/functional:any_invocable",
+        "absl/functional:function_ref",
         "absl/status",
         "absl/status:statusor",
         "absl/types:optional",
@@ -5305,6 +5331,7 @@ grpc_cc_library(
     ],
     external_deps = [
         "absl/base:core_headers",
+        "absl/functional:function_ref",
         "absl/status",
         "absl/status:statusor",
         "absl/strings",
diff --git a/src/core/ext/filters/client_channel/client_channel.cc b/src/core/ext/filters/client_channel/client_channel.cc
index 991cbee4fc8..b5064ceb20f 100644
--- a/src/core/ext/filters/client_channel/client_channel.cc
+++ b/src/core/ext/filters/client_channel/client_channel.cc
@@ -1599,7 +1599,12 @@ absl::Status ClientChannel::CreateOrUpdateLbPolicyLocked(
     Resolver::Result result) {
   // Construct update.
   LoadBalancingPolicy::UpdateArgs update_args;
-  update_args.addresses = std::move(result.addresses);
+  if (!result.addresses.ok()) {
+    update_args.addresses = result.addresses.status();
+  } else {
+    update_args.addresses = std::make_shared<EndpointAddressesListIterator>(
+        std::move(*result.addresses));
+  }
   update_args.config = std::move(lb_policy_config);
   update_args.resolution_note = std::move(result.resolution_note);
   // Remove the config selector from channel args so that we're not holding
diff --git a/src/core/ext/filters/client_channel/lb_policy/address_filtering.cc b/src/core/ext/filters/client_channel/lb_policy/address_filtering.cc
index b6e8396b95e..bac15550d2d 100644
--- a/src/core/ext/filters/client_channel/lb_policy/address_filtering.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/address_filtering.cc
@@ -20,11 +20,13 @@
 
 #include <stddef.h>
 
-#include <algorithm>
 #include <utility>
 
+#include "absl/functional/function_ref.h"
+
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/gprpp/ref_counted_ptr.h"
+#include "src/core/lib/iomgr/resolved_address.h"
 
 namespace grpc_core {
 
@@ -43,32 +45,63 @@ int HierarchicalPathArg::ChannelArgsCompare(const HierarchicalPathArg* a,
   return 0;
 }
 
+namespace {
+
+class HierarchicalAddressIterator : public EndpointAddressesIterator {
+ public:
+  HierarchicalAddressIterator(
+      std::shared_ptr<EndpointAddressesIterator> parent_it,
+      RefCountedStringValue child_name)
+      : parent_it_(std::move(parent_it)), child_name_(std::move(child_name)) {}
+
+  void ForEach(absl::FunctionRef<void(const EndpointAddresses&)> callback)
+      const override {
+    RefCountedPtr<HierarchicalPathArg> remaining_path_attr;
+    parent_it_->ForEach([&](const EndpointAddresses& endpoint) {
+      const auto* path_arg = endpoint.args().GetObject<HierarchicalPathArg>();
+      if (path_arg == nullptr) return;
+      const std::vector<RefCountedStringValue>& path = path_arg->path();
+      auto it = path.begin();
+      if (it == path.end()) return;
+      if (*it != child_name_) return;
+      ChannelArgs args = endpoint.args();
+      ++it;
+      if (it != path.end()) {
+        std::vector<RefCountedStringValue> remaining_path(it, path.end());
+        if (remaining_path_attr == nullptr ||
+            remaining_path_attr->path() != remaining_path) {
+          remaining_path_attr =
+              MakeRefCounted<HierarchicalPathArg>(std::move(remaining_path));
+        }
+        args = args.SetObject(remaining_path_attr);
+      }
+      callback(EndpointAddresses(endpoint.addresses(), args));
+    });
+  }
+
+ private:
+  std::shared_ptr<EndpointAddressesIterator> parent_it_;
+  RefCountedStringValue child_name_;
+};
+
+}  // namespace
+
 absl::StatusOr<HierarchicalAddressMap> MakeHierarchicalAddressMap(
-    const absl::StatusOr<EndpointAddressesList>& addresses) {
+    absl::StatusOr<std::shared_ptr<EndpointAddressesIterator>> addresses) {
   if (!addresses.ok()) return addresses.status();
   HierarchicalAddressMap result;
-  RefCountedPtr<HierarchicalPathArg> remaining_path_attr;
-  for (const EndpointAddresses& endpoint_addresses : *addresses) {
-    const auto* path_arg =
-        endpoint_addresses.args().GetObject<HierarchicalPathArg>();
-    if (path_arg == nullptr) continue;
+  (*addresses)->ForEach([&](const EndpointAddresses& endpoint) {
+    const auto* path_arg = endpoint.args().GetObject<HierarchicalPathArg>();
+    if (path_arg == nullptr) return;
     const std::vector<RefCountedStringValue>& path = path_arg->path();
     auto it = path.begin();
-    if (it == path.end()) continue;
-    EndpointAddressesList& target_list = result[*it];
-    ChannelArgs args = endpoint_addresses.args();
-    ++it;
-    if (it != path.end()) {
-      std::vector<RefCountedStringValue> remaining_path(it, path.end());
-      if (remaining_path_attr == nullptr ||
-          remaining_path_attr->path() != remaining_path) {
-        remaining_path_attr =
-            MakeRefCounted<HierarchicalPathArg>(std::move(remaining_path));
-      }
-      args = args.SetObject(remaining_path_attr);
+    if (it == path.end()) return;
+    auto& target_list = result[*it];
+    if (target_list == nullptr) {
+      target_list =
+          std::make_shared<HierarchicalAddressIterator>(*addresses, *it);
     }
-    target_list.emplace_back(endpoint_addresses.addresses(), args);
-  }
+  });
   return result;
 }
 
diff --git a/src/core/ext/filters/client_channel/lb_policy/address_filtering.h b/src/core/ext/filters/client_channel/lb_policy/address_filtering.h
index d0e2faae294..924261669bd 100644
--- a/src/core/ext/filters/client_channel/lb_policy/address_filtering.h
+++ b/src/core/ext/filters/client_channel/lb_policy/address_filtering.h
@@ -20,6 +20,7 @@
 #include <grpc/support/port_platform.h>
 
 #include <map>
+#include <memory>
 #include <utility>
 #include <vector>
 
@@ -105,12 +106,12 @@ class HierarchicalPathArg : public RefCounted<HierarchicalPathArg> {
 // A map from the next path element to the endpoint addresses that fall
 // under that path element.
 using HierarchicalAddressMap =
-    std::map<RefCountedStringValue, EndpointAddressesList,
+    std::map<RefCountedStringValue, std::shared_ptr<EndpointAddressesIterator>,
              RefCountedStringValueLessThan>;
 
 // Splits up the addresses into a separate list for each child.
 absl::StatusOr<HierarchicalAddressMap> MakeHierarchicalAddressMap(
-    const absl::StatusOr<EndpointAddressesList>& addresses);
+    absl::StatusOr<std::shared_ptr<EndpointAddressesIterator>> addresses);
 
 }  // namespace grpc_core
 
diff --git a/src/core/ext/filters/client_channel/lb_policy/endpoint_list.cc b/src/core/ext/filters/client_channel/lb_policy/endpoint_list.cc
index 2c878bb2db0..7f2ecdd69f0 100644
--- a/src/core/ext/filters/client_channel/lb_policy/endpoint_list.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/endpoint_list.cc
@@ -118,7 +118,7 @@ void EndpointList::Endpoint::Init(
   GPR_ASSERT(config.ok());
   // Update child policy.
   LoadBalancingPolicy::UpdateArgs update_args;
-  update_args.addresses.emplace().emplace_back(addresses);
+  update_args.addresses = std::make_shared<SingleEndpointIterator>(addresses);
   update_args.args = child_args;
   update_args.config = std::move(*config);
   // TODO(roth): If the child reports a non-OK status with the update,
@@ -163,15 +163,16 @@ RefCountedPtr<SubchannelInterface> EndpointList::Endpoint::CreateSubchannel(
 //
 
 void EndpointList::Init(
-    const EndpointAddressesList& endpoints, const ChannelArgs& args,
-    absl::AnyInvocable<OrphanablePtr<Endpoint>(RefCountedPtr<EndpointList>,
-                                               const EndpointAddresses&,
-                                               const ChannelArgs&)>
+    EndpointAddressesIterator* endpoints, const ChannelArgs& args,
+    absl::FunctionRef<OrphanablePtr<Endpoint>(RefCountedPtr<EndpointList>,
+                                              const EndpointAddresses&,
+                                              const ChannelArgs&)>
         create_endpoint) {
-  for (const EndpointAddresses& addresses : endpoints) {
+  if (endpoints == nullptr) return;
+  endpoints->ForEach([&](const EndpointAddresses& endpoint) {
     endpoints_.push_back(
-        create_endpoint(Ref(DEBUG_LOCATION, "Endpoint"), addresses, args));
-  }
+        create_endpoint(Ref(DEBUG_LOCATION, "Endpoint"), endpoint, args));
+  });
 }
 
 void EndpointList::ResetBackoffLocked() {
diff --git a/src/core/ext/filters/client_channel/lb_policy/endpoint_list.h b/src/core/ext/filters/client_channel/lb_policy/endpoint_list.h
index df31bc39c0e..c814d9f50eb 100644
--- a/src/core/ext/filters/client_channel/lb_policy/endpoint_list.h
+++ b/src/core/ext/filters/client_channel/lb_policy/endpoint_list.h
@@ -25,7 +25,7 @@
 #include <utility>
 #include <vector>
 
-#include "absl/functional/any_invocable.h"
+#include "absl/functional/function_ref.h"
 #include "absl/status/status.h"
 #include "absl/types/optional.h"
 
@@ -53,7 +53,7 @@ namespace grpc_core {
 class MyEndpointList : public EndpointList {
  public:
   MyEndpointList(RefCountedPtr<MyLbPolicy> lb_policy,
-                 const EndpointAddressesList& endpoints,
+                 EndpointAddressesIterator* endpoints,
                  const ChannelArgs& args)
       : EndpointList(std::move(lb_policy),
                      GRPC_TRACE_FLAG_ENABLED(grpc_my_tracer)
@@ -184,8 +184,8 @@ class EndpointList : public InternallyRefCounted<EndpointList> {
   EndpointList(RefCountedPtr<LoadBalancingPolicy> policy, const char* tracer)
       : policy_(std::move(policy)), tracer_(tracer) {}
 
-  void Init(const EndpointAddressesList& endpoints, const ChannelArgs& args,
-            absl::AnyInvocable<OrphanablePtr<Endpoint>(
+  void Init(EndpointAddressesIterator* endpoints, const ChannelArgs& args,
+            absl::FunctionRef<OrphanablePtr<Endpoint>(
                 RefCountedPtr<EndpointList>, const EndpointAddresses&,
                 const ChannelArgs&)>
                 create_endpoint);
diff --git a/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb.cc b/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb.cc
index 4d3ebc1455d..0f4c7675f89 100644
--- a/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb.cc
@@ -72,6 +72,7 @@
 #include <vector>
 
 #include "absl/container/inlined_vector.h"
+#include "absl/functional/function_ref.h"
 #include "absl/status/status.h"
 #include "absl/status/statusor.h"
 #include "absl/strings/str_cat.h"
@@ -384,9 +385,9 @@ class GrpcLb : public LoadBalancingPolicy {
     // Returns a text representation suitable for logging.
     std::string AsText() const;
 
-    // Extracts all non-drop entries into an EndpointAddressesList.
-    EndpointAddressesList GetServerAddressList(
-        GrpcLbClientStats* client_stats) const;
+    // Extracts all non-drop entries into an EndpointAddressesIterator.
+    std::shared_ptr<EndpointAddressesIterator> GetServerAddressList(
+        GrpcLbClientStats* client_stats);
 
     // Returns true if the serverlist contains at least one drop entry and
     // no backend address entries.
@@ -400,6 +401,8 @@ class GrpcLb : public LoadBalancingPolicy {
     const char* ShouldDrop();
 
    private:
+    class AddressIterator;
+
     std::vector<GrpcLbServer> serverlist_;
 
     // Accessed from the picker, so needs synchronization.
@@ -504,6 +507,8 @@ class GrpcLb : public LoadBalancingPolicy {
     RefCountedPtr<GrpcLb> parent_;
   };
 
+  class NullLbTokenEndpointIterator;
+
   void ShutdownLocked() override;
 
   // Helper functions used in UpdateLocked().
@@ -569,7 +574,8 @@ class GrpcLb : public LoadBalancingPolicy {
   // Whether we're in fallback mode.
   bool fallback_mode_ = false;
   // The backend addresses from the resolver.
-  absl::StatusOr<EndpointAddressesList> fallback_backend_addresses_;
+  absl::StatusOr<std::shared_ptr<NullLbTokenEndpointIterator>>
+      fallback_backend_addresses_;
   // The last resolution note from our parent.
   // To be passed to child policy when fallback_backend_addresses_ is empty.
   std::string resolution_note_;
@@ -594,11 +600,30 @@ class GrpcLb : public LoadBalancingPolicy {
 };
 
 //
-// GrpcLb::Serverlist
+// GrpcLb::Serverlist::AddressIterator
 //
 
-bool GrpcLb::Serverlist::operator==(const Serverlist& other) const {
-  return serverlist_ == other.serverlist_;
+bool IsServerValid(const GrpcLbServer& server, size_t idx, bool log) {
+  if (server.drop) return false;
+  if (GPR_UNLIKELY(server.port >> 16 != 0)) {
+    if (log) {
+      gpr_log(GPR_ERROR,
+              "Invalid port '%d' at index %" PRIuPTR
+              " of serverlist. Ignoring.",
+              server.port, idx);
+    }
+    return false;
+  }
+  if (GPR_UNLIKELY(server.ip_size != 4 && server.ip_size != 16)) {
+    if (log) {
+      gpr_log(GPR_ERROR,
+              "Expected IP to be 4 or 16 bytes, got %d at index %" PRIuPTR
+              " of serverlist. Ignoring",
+              server.ip_size, idx);
+    }
+    return false;
+  }
+  return true;
 }
 
 void ParseServer(const GrpcLbServer& server, grpc_resolved_address* addr) {
@@ -623,6 +648,53 @@ void ParseServer(const GrpcLbServer& server, grpc_resolved_address* addr) {
   }
 }
 
+class GrpcLb::Serverlist::AddressIterator : public EndpointAddressesIterator {
+ public:
+  AddressIterator(RefCountedPtr<Serverlist> serverlist,
+                  RefCountedPtr<GrpcLbClientStats> client_stats)
+      : serverlist_(std::move(serverlist)),
+        client_stats_(std::move(client_stats)) {}
+
+  void ForEach(absl::FunctionRef<void(const EndpointAddresses&)> callback)
+      const override {
+    for (size_t i = 0; i < serverlist_->serverlist_.size(); ++i) {
+      const GrpcLbServer& server = serverlist_->serverlist_[i];
+      if (!IsServerValid(server, i, false)) continue;
+      // Address processing.
+      grpc_resolved_address addr;
+      ParseServer(server, &addr);
+      // LB token processing.
+      const size_t lb_token_length = strnlen(
+          server.load_balance_token, GPR_ARRAY_SIZE(server.load_balance_token));
+      std::string lb_token(server.load_balance_token, lb_token_length);
+      if (lb_token.empty()) {
+        auto addr_uri = grpc_sockaddr_to_uri(&addr);
+        gpr_log(GPR_INFO,
+                "Missing LB token for backend address '%s'. The empty token "
+                "will be used instead",
+                addr_uri.ok() ? addr_uri->c_str()
+                              : addr_uri.status().ToString().c_str());
+      }
+      // Return address with a channel arg containing LB token and stats object.
+      callback(EndpointAddresses(
+          addr, ChannelArgs().SetObject(MakeRefCounted<TokenAndClientStatsArg>(
+                    std::move(lb_token), client_stats_))));
+    }
+  }
+
+ private:
+  RefCountedPtr<Serverlist> serverlist_;
+  RefCountedPtr<GrpcLbClientStats> client_stats_;
+};
+
+//
+// GrpcLb::Serverlist
+//
+
+bool GrpcLb::Serverlist::operator==(const Serverlist& other) const {
+  return serverlist_ == other.serverlist_;
+}
+
 std::string GrpcLb::Serverlist::AsText() const {
   std::vector<std::string> entries;
   for (size_t i = 0; i < serverlist_.size(); ++i) {
@@ -642,59 +714,12 @@ std::string GrpcLb::Serverlist::AsText() const {
   return absl::StrJoin(entries, "");
 }
 
-bool IsServerValid(const GrpcLbServer& server, size_t idx, bool log) {
-  if (server.drop) return false;
-  if (GPR_UNLIKELY(server.port >> 16 != 0)) {
-    if (log) {
-      gpr_log(GPR_ERROR,
-              "Invalid port '%d' at index %" PRIuPTR
-              " of serverlist. Ignoring.",
-              server.port, idx);
-    }
-    return false;
-  }
-  if (GPR_UNLIKELY(server.ip_size != 4 && server.ip_size != 16)) {
-    if (log) {
-      gpr_log(GPR_ERROR,
-              "Expected IP to be 4 or 16 bytes, got %d at index %" PRIuPTR
-              " of serverlist. Ignoring",
-              server.ip_size, idx);
-    }
-    return false;
-  }
-  return true;
-}
-
 // Returns addresses extracted from the serverlist.
-EndpointAddressesList GrpcLb::Serverlist::GetServerAddressList(
-    GrpcLbClientStats* client_stats) const {
+std::shared_ptr<EndpointAddressesIterator>
+GrpcLb::Serverlist::GetServerAddressList(GrpcLbClientStats* client_stats) {
   RefCountedPtr<GrpcLbClientStats> stats;
   if (client_stats != nullptr) stats = client_stats->Ref();
-  EndpointAddressesList endpoints;
-  for (size_t i = 0; i < serverlist_.size(); ++i) {
-    const GrpcLbServer& server = serverlist_[i];
-    if (!IsServerValid(server, i, false)) continue;
-    // Address processing.
-    grpc_resolved_address addr;
-    ParseServer(server, &addr);
-    // LB token processing.
-    const size_t lb_token_length = strnlen(
-        server.load_balance_token, GPR_ARRAY_SIZE(server.load_balance_token));
-    std::string lb_token(server.load_balance_token, lb_token_length);
-    if (lb_token.empty()) {
-      auto addr_uri = grpc_sockaddr_to_uri(&addr);
-      gpr_log(GPR_INFO,
-              "Missing LB token for backend address '%s'. The empty token will "
-              "be used instead",
-              addr_uri.ok() ? addr_uri->c_str()
-                            : addr_uri.status().ToString().c_str());
-    }
-    // Add address with a channel arg containing LB token and stats object.
-    endpoints.emplace_back(
-        addr, ChannelArgs().SetObject(MakeRefCounted<TokenAndClientStatsArg>(
-                  std::move(lb_token), stats)));
-  }
-  return endpoints;
+  return std::make_shared<AddressIterator>(Ref(), std::move(stats));
 }
 
 bool GrpcLb::Serverlist::ContainsAllDropEntries() const {
@@ -1503,6 +1528,31 @@ void GrpcLb::ResetBackoffLocked() {
   }
 }
 
+// Endpoint iterator wrapper to add null LB token attribute.
+class GrpcLb::NullLbTokenEndpointIterator : public EndpointAddressesIterator {
+ public:
+  explicit NullLbTokenEndpointIterator(
+      std::shared_ptr<EndpointAddressesIterator> parent_it)
+      : parent_it_(std::move(parent_it)) {}
+
+  void ForEach(absl::FunctionRef<void(const EndpointAddresses&)> callback)
+      const override {
+    parent_it_->ForEach([&](const EndpointAddresses& endpoint) {
+      if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_glb_trace)) {
+        gpr_log(GPR_INFO, "[grpclb %p] fallback address: %s", this,
+                endpoint.ToString().c_str());
+      }
+      callback(EndpointAddresses(endpoint.addresses(),
+                                 endpoint.args().SetObject(empty_token_)));
+    });
+  }
+
+ private:
+  std::shared_ptr<EndpointAddressesIterator> parent_it_;
+  RefCountedPtr<TokenAndClientStatsArg> empty_token_ =
+      MakeRefCounted<TokenAndClientStatsArg>("", nullptr);
+};
+
 absl::Status GrpcLb::UpdateLocked(UpdateArgs args) {
   if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_glb_trace)) {
     gpr_log(GPR_INFO, "[grpclb %p] received update", this);
@@ -1512,19 +1562,11 @@ absl::Status GrpcLb::UpdateLocked(UpdateArgs args) {
   GPR_ASSERT(config_ != nullptr);
   args_ = std::move(args.args);
   // Update fallback address list.
-  fallback_backend_addresses_ = std::move(args.addresses);
-  if (fallback_backend_addresses_.ok()) {
-    // Add null LB token attributes.
-    for (EndpointAddresses& endpoint : *fallback_backend_addresses_) {
-      endpoint = EndpointAddresses(
-          endpoint.addresses(),
-          endpoint.args().SetObject(
-              MakeRefCounted<TokenAndClientStatsArg>("", nullptr)));
-      if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_glb_trace)) {
-        gpr_log(GPR_INFO, "[grpclb %p] fallback address: %s", this,
-                endpoint.ToString().c_str());
-      }
-    }
+  if (!args.addresses.ok()) {
+    fallback_backend_addresses_ = args.addresses.status();
+  } else {
+    fallback_backend_addresses_ = std::make_shared<NullLbTokenEndpointIterator>(
+        std::move(*args.addresses));
   }
   resolution_note_ = std::move(args.resolution_note);
   // Update balancer channel.
@@ -1756,6 +1798,12 @@ OrphanablePtr<LoadBalancingPolicy> GrpcLb::CreateChildPolicyLocked(
   return lb_policy;
 }
 
+bool EndpointIteratorIsEmpty(const EndpointAddressesIterator& endpoints) {
+  bool empty = true;
+  endpoints.ForEach([&](const EndpointAddresses&) { empty = false; });
+  return empty;
+}
+
 void GrpcLb::CreateOrUpdateChildPolicyLocked() {
   if (shutting_down_) return;
   // Construct update args.
@@ -1769,16 +1817,17 @@ void GrpcLb::CreateOrUpdateChildPolicyLocked() {
     // picks.
     update_args.addresses = fallback_backend_addresses_;
     if (fallback_backend_addresses_.ok() &&
-        fallback_backend_addresses_->empty()) {
+        EndpointIteratorIsEmpty(**fallback_backend_addresses_)) {
       update_args.resolution_note = absl::StrCat(
-          "grpclb in fallback mode without any balancer addresses: ",
+          "grpclb in fallback mode without any fallback addresses: ",
           resolution_note_);
     }
   } else {
     update_args.addresses = serverlist_->GetServerAddressList(
         lb_calld_ == nullptr ? nullptr : lb_calld_->client_stats());
     is_backend_from_grpclb_load_balancer = true;
-    if (update_args.addresses.ok() && update_args.addresses->empty()) {
+    if (update_args.addresses.ok() &&
+        EndpointIteratorIsEmpty(**update_args.addresses)) {
       update_args.resolution_note = "empty serverlist from grpclb balancer";
     }
   }
diff --git a/src/core/ext/filters/client_channel/lb_policy/outlier_detection/outlier_detection.cc b/src/core/ext/filters/client_channel/lb_policy/outlier_detection/outlier_detection.cc
index 8569f24019d..656332b2128 100644
--- a/src/core/ext/filters/client_channel/lb_policy/outlier_detection/outlier_detection.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/outlier_detection/outlier_detection.cc
@@ -661,7 +661,7 @@ absl::Status OutlierDetectionLb::UpdateLocked(UpdateArgs args) {
   if (args.addresses.ok()) {
     std::set<EndpointAddressSet> current_endpoints;
     std::set<grpc_resolved_address, ResolvedAddressLessThan> current_addresses;
-    for (const EndpointAddresses& endpoint : *args.addresses) {
+    (*args.addresses)->ForEach([&](const EndpointAddresses& endpoint) {
       EndpointAddressSet key(endpoint.addresses());
       current_endpoints.emplace(key);
       for (const grpc_resolved_address& address : endpoint.addresses()) {
@@ -708,7 +708,7 @@ absl::Status OutlierDetectionLb::UpdateLocked(UpdateArgs args) {
         }
         it->second->DisableEjection();
       }
-    }
+    });
     // Remove any entries we no longer need in the subchannel map.
     for (auto it = subchannel_state_map_.begin();
          it != subchannel_state_map_.end();) {
@@ -753,7 +753,6 @@ absl::Status OutlierDetectionLb::UpdateLocked(UpdateArgs args) {
   update_args.addresses = std::move(args.addresses);
   update_args.resolution_note = std::move(args.resolution_note);
   update_args.config = config_->child_policy();
-  // Update the policy.
   update_args.args = std::move(args.args);
   if (GRPC_TRACE_FLAG_ENABLED(grpc_outlier_detection_lb_trace)) {
     gpr_log(GPR_INFO,
diff --git a/src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc b/src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc
index 577744a3fff..e51248faa9c 100644
--- a/src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc
@@ -21,7 +21,6 @@
 #include <inttypes.h>
 #include <string.h>
 
-#include <algorithm>
 #include <memory>
 #include <set>
 #include <string>
@@ -114,7 +113,7 @@ class PickFirst : public LoadBalancingPolicy {
    public:
     class SubchannelData {
      public:
-      SubchannelData(SubchannelList* subchannel_list,
+      SubchannelData(SubchannelList* subchannel_list, size_t index,
                      RefCountedPtr<SubchannelInterface> subchannel);
 
       SubchannelInterface* subchannel() const { return subchannel_.get(); }
@@ -125,12 +124,6 @@ class PickFirst : public LoadBalancingPolicy {
         return connectivity_status_;
       }
 
-      // Returns the index into the subchannel list of this object.
-      size_t Index() const {
-        return static_cast<size_t>(this -
-                                   &subchannel_list_->subchannels_.front());
-      }
-
       // Resets the connection backoff.
       void ResetBackoffLocked() {
         if (subchannel_ != nullptr) subchannel_->ResetBackoff();
@@ -153,10 +146,8 @@ class PickFirst : public LoadBalancingPolicy {
       class Watcher
           : public SubchannelInterface::ConnectivityStateWatcherInterface {
        public:
-        Watcher(SubchannelData* subchannel_data,
-                RefCountedPtr<SubchannelList> subchannel_list)
-            : subchannel_data_(subchannel_data),
-              subchannel_list_(std::move(subchannel_list)) {}
+        Watcher(RefCountedPtr<SubchannelList> subchannel_list, size_t index)
+            : subchannel_list_(std::move(subchannel_list)), index_(index) {}
 
         ~Watcher() override {
           subchannel_list_.reset(DEBUG_LOCATION, "Watcher dtor");
@@ -164,8 +155,8 @@ class PickFirst : public LoadBalancingPolicy {
 
         void OnConnectivityStateChange(grpc_connectivity_state new_state,
                                        absl::Status status) override {
-          subchannel_data_->OnConnectivityStateChange(new_state,
-                                                      std::move(status));
+          subchannel_list_->subchannels_[index_].OnConnectivityStateChange(
+              new_state, std::move(status));
         }
 
         grpc_pollset_set* interested_parties() override {
@@ -173,8 +164,8 @@ class PickFirst : public LoadBalancingPolicy {
         }
 
        private:
-        SubchannelData* subchannel_data_;
         RefCountedPtr<SubchannelList> subchannel_list_;
+        const size_t index_;
       };
 
       // This method will be invoked once soon after instantiation to report
@@ -193,6 +184,7 @@ class PickFirst : public LoadBalancingPolicy {
 
       // Backpointer to owning subchannel list.  Not owned.
       SubchannelList* subchannel_list_;
+      const size_t index_;
       // The subchannel.
       RefCountedPtr<SubchannelInterface> subchannel_;
       // Will be non-null when the subchannel's state is being watched.
@@ -205,7 +197,8 @@ class PickFirst : public LoadBalancingPolicy {
     };
 
     SubchannelList(RefCountedPtr<PickFirst> policy,
-                   EndpointAddressesList addresses, const ChannelArgs& args);
+                   EndpointAddressesIterator* addresses,
+                   const ChannelArgs& args);
 
     ~SubchannelList() override;
 
@@ -413,9 +406,9 @@ void PickFirst::ResetBackoffLocked() {
 
 void PickFirst::AttemptToConnectUsingLatestUpdateArgsLocked() {
   // Create a subchannel list from latest_update_args_.
-  EndpointAddressesList addresses;
+  EndpointAddressesIterator* addresses = nullptr;
   if (latest_update_args_.addresses.ok()) {
-    addresses = *latest_update_args_.addresses;
+    addresses = latest_update_args_.addresses->get();
   }
   // Replace latest_pending_subchannel_list_.
   if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_pick_first_trace) &&
@@ -425,7 +418,7 @@ void PickFirst::AttemptToConnectUsingLatestUpdateArgsLocked() {
             latest_pending_subchannel_list_.get());
   }
   latest_pending_subchannel_list_ = MakeOrphanable<SubchannelList>(
-      Ref(), std::move(addresses), latest_update_args_.args);
+      Ref(), addresses, latest_update_args_.args);
   // Empty update or no valid subchannels.  Put the channel in
   // TRANSIENT_FAILURE and request re-resolution.
   if (latest_pending_subchannel_list_->size() == 0) {
@@ -483,9 +476,7 @@ class AddressFamilyIterator {
 absl::Status PickFirst::UpdateLocked(UpdateArgs args) {
   if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_pick_first_trace)) {
     if (args.addresses.ok()) {
-      gpr_log(GPR_INFO,
-              "Pick First %p received update with %" PRIuPTR " addresses", this,
-              args.addresses->size());
+      gpr_log(GPR_INFO, "Pick First %p received update", this);
     } else {
       gpr_log(GPR_INFO, "Pick First %p received update with address error: %s",
               this, args.addresses.status().ToString().c_str());
@@ -495,51 +486,59 @@ absl::Status PickFirst::UpdateLocked(UpdateArgs args) {
   absl::Status status;
   if (!args.addresses.ok()) {
     status = args.addresses.status();
-  } else if (args.addresses->empty()) {
-    status = absl::UnavailableError("address list must not be empty");
   } else {
-    // Shuffle the list if needed.
-    auto config = static_cast<PickFirstConfig*>(args.config.get());
-    if (config->shuffle_addresses()) {
-      absl::c_shuffle(*args.addresses, bit_gen_);
-    }
-    // Flatten the list so that we have one address per endpoint.
-    // While we're iterating, also determine the desired address family
-    // order and the index of the first element of each family, for use in
-    // the interleaving below.
-    std::set<absl::string_view> address_families;
-    std::vector<AddressFamilyIterator> address_family_order;
     EndpointAddressesList endpoints;
-    for (const auto& endpoint : *args.addresses) {
-      for (const auto& address : endpoint.addresses()) {
-        endpoints.emplace_back(address, endpoint.args());
-        if (IsPickFirstHappyEyeballsEnabled()) {
-          absl::string_view scheme = GetAddressFamily(address);
-          bool inserted = address_families.insert(scheme).second;
-          if (inserted) {
-            address_family_order.emplace_back(scheme, endpoints.size() - 1);
+    (*args.addresses)->ForEach([&](const EndpointAddresses& endpoint) {
+      endpoints.push_back(endpoint);
+    });
+    if (endpoints.empty()) {
+      status = absl::UnavailableError("address list must not be empty");
+    } else {
+      // Shuffle the list if needed.
+      auto config = static_cast<PickFirstConfig*>(args.config.get());
+      if (config->shuffle_addresses()) {
+        absl::c_shuffle(endpoints, bit_gen_);
+      }
+      // Flatten the list so that we have one address per endpoint.
+      // While we're iterating, also determine the desired address family
+      // order and the index of the first element of each family, for use in
+      // the interleaving below.
+      std::set<absl::string_view> address_families;
+      std::vector<AddressFamilyIterator> address_family_order;
+      EndpointAddressesList flattened_endpoints;
+      for (const auto& endpoint : endpoints) {
+        for (const auto& address : endpoint.addresses()) {
+          flattened_endpoints.emplace_back(address, endpoint.args());
+          if (IsPickFirstHappyEyeballsEnabled()) {
+            absl::string_view scheme = GetAddressFamily(address);
+            bool inserted = address_families.insert(scheme).second;
+            if (inserted) {
+              address_family_order.emplace_back(scheme,
+                                                flattened_endpoints.size() - 1);
+            }
           }
         }
       }
-    }
-    // Interleave addresses as per RFC-8305 section 4.
-    if (IsPickFirstHappyEyeballsEnabled()) {
-      EndpointAddressesList interleaved_endpoints;
-      interleaved_endpoints.reserve(endpoints.size());
-      std::vector<bool> endpoints_moved(endpoints.size());
-      size_t scheme_index = 0;
-      for (size_t i = 0; i < endpoints.size(); ++i) {
-        EndpointAddresses* endpoint;
-        do {
-          auto& iterator = address_family_order[scheme_index++ %
-                                                address_family_order.size()];
-          endpoint = iterator.Next(endpoints, &endpoints_moved);
-        } while (endpoint == nullptr);
-        interleaved_endpoints.emplace_back(std::move(*endpoint));
+      endpoints = std::move(flattened_endpoints);
+      // Interleave addresses as per RFC-8305 section 4.
+      if (IsPickFirstHappyEyeballsEnabled()) {
+        EndpointAddressesList interleaved_endpoints;
+        interleaved_endpoints.reserve(endpoints.size());
+        std::vector<bool> endpoints_moved(endpoints.size());
+        size_t scheme_index = 0;
+        for (size_t i = 0; i < endpoints.size(); ++i) {
+          EndpointAddresses* endpoint;
+          do {
+            auto& iterator = address_family_order[scheme_index++ %
+                                                  address_family_order.size()];
+            endpoint = iterator.Next(endpoints, &endpoints_moved);
+          } while (endpoint == nullptr);
+          interleaved_endpoints.emplace_back(std::move(*endpoint));
+        }
+        endpoints = std::move(interleaved_endpoints);
       }
-      args.addresses = std::move(interleaved_endpoints);
-    } else {
-      args.addresses = std::move(endpoints);
+      args.addresses =
+          std::make_shared<EndpointAddressesListIterator>(std::move(endpoints));
     }
   }
   // If the update contains a resolver error and we have a previous update
@@ -617,18 +616,20 @@ void PickFirst::HealthWatcher::OnConnectivityStateChange(
 //
 
 PickFirst::SubchannelList::SubchannelData::SubchannelData(
-    SubchannelList* subchannel_list,
+    SubchannelList* subchannel_list, size_t index,
     RefCountedPtr<SubchannelInterface> subchannel)
-    : subchannel_list_(subchannel_list), subchannel_(std::move(subchannel)) {
+    : subchannel_list_(subchannel_list),
+      index_(index),
+      subchannel_(std::move(subchannel)) {
   if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_pick_first_trace)) {
     gpr_log(GPR_INFO,
             "[PF %p] subchannel list %p index %" PRIuPTR
             " (subchannel %p): starting watch",
-            subchannel_list_->policy_.get(), subchannel_list_,
-            subchannel_list_->size(), subchannel_.get());
+            subchannel_list_->policy_.get(), subchannel_list_, index_,
+            subchannel_.get());
   }
   auto watcher = std::make_unique<Watcher>(
-      this, subchannel_list_->Ref(DEBUG_LOCATION, "Watcher"));
+      subchannel_list_->Ref(DEBUG_LOCATION, "Watcher"), index_);
   pending_watcher_ = watcher.get();
   subchannel_->WatchConnectivityState(std::move(watcher));
 }
@@ -639,7 +640,7 @@ void PickFirst::SubchannelList::SubchannelData::ShutdownLocked() {
       gpr_log(GPR_INFO,
               "[PF %p] subchannel list %p index %" PRIuPTR " of %" PRIuPTR
               " (subchannel %p): cancelling watch and unreffing subchannel",
-              subchannel_list_->policy_.get(), subchannel_list_, Index(),
+              subchannel_list_->policy_.get(), subchannel_list_, index_,
               subchannel_list_->size(), subchannel_.get());
     }
     subchannel_->CancelConnectivityStateWatch(pending_watcher_);
@@ -659,7 +660,7 @@ void PickFirst::SubchannelList::SubchannelData::OnConnectivityStateChange(
         "status=%s, shutting_down=%d, pending_watcher=%p, "
         "seen_transient_failure=%d, p->selected_=%p, "
         "p->subchannel_list_=%p, p->latest_pending_subchannel_list_=%p",
-        p, subchannel_list_, Index(), subchannel_list_->size(),
+        p, subchannel_list_, index_, subchannel_list_->size(),
         subchannel_.get(),
         (connectivity_state_.has_value()
              ? ConnectivityStateName(*connectivity_state_)
@@ -771,7 +772,7 @@ void PickFirst::SubchannelList::SubchannelData::OnConnectivityStateChange(
   if (!IsPickFirstHappyEyeballsEnabled()) {
     // Ignore any other updates for subchannels we're not currently trying to
     // connect to.
-    if (Index() != subchannel_list_->attempting_index_) return;
+    if (index_ != subchannel_list_->attempting_index_) return;
     // React to the connectivity state.
     ReactToConnectivityStateLocked();
     return;
@@ -784,7 +785,7 @@ void PickFirst::SubchannelList::SubchannelData::OnConnectivityStateChange(
       if (!prev_seen_transient_failure && seen_transient_failure_) {
         // If a connection attempt fails before the timer fires, then
         // cancel the timer and start connecting on the next subchannel.
-        if (Index() == subchannel_list_->attempting_index_) {
+        if (index_ == subchannel_list_->attempting_index_) {
           if (subchannel_list_->timer_handle_.has_value()) {
             p->channel_control_helper()->GetEventEngine()->Cancel(
                 *subchannel_list_->timer_handle_);
@@ -858,7 +859,7 @@ void PickFirst::SubchannelList::SubchannelData::
       // We skip subchannels in state TRANSIENT_FAILURE to avoid a
       // large recursion that could overflow the stack.
       SubchannelData* found_subchannel = nullptr;
-      for (size_t next_index = Index() + 1;
+      for (size_t next_index = index_ + 1;
            next_index < subchannel_list_->size(); ++next_index) {
         SubchannelData* sc = &subchannel_list_->subchannels_[next_index];
         GPR_ASSERT(sc->connectivity_state_.has_value());
@@ -946,14 +947,14 @@ void PickFirst::SubchannelList::SubchannelData::RequestConnectionWithTimer() {
     GPR_ASSERT(connectivity_state_ == GRPC_CHANNEL_CONNECTING);
   }
   // If this is not the last subchannel in the list, start the timer.
-  if (Index() != subchannel_list_->size() - 1) {
+  if (index_ != subchannel_list_->size() - 1) {
     PickFirst* p = subchannel_list_->policy_.get();
     if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_pick_first_trace)) {
       gpr_log(GPR_INFO,
               "Pick First %p subchannel list %p: starting Connection "
               "Attempt Delay timer for %" PRId64 "ms for index %" PRIuPTR,
               p, subchannel_list_, p->connection_attempt_delay_.millis(),
-              Index());
+              index_);
     }
     subchannel_list_->timer_handle_ =
         p->channel_control_helper()->GetEventEngine()->RunAfter(
@@ -1041,7 +1042,7 @@ void PickFirst::SubchannelList::SubchannelData::ProcessUnselectedReadyLocked() {
   }
   // Unref all other subchannels in the list.
   for (size_t i = 0; i < subchannel_list_->size(); ++i) {
-    if (i != Index()) {
+    if (i != index_) {
       subchannel_list_->subchannels_[i].ShutdownLocked();
     }
   }
@@ -1052,7 +1053,7 @@ void PickFirst::SubchannelList::SubchannelData::ProcessUnselectedReadyLocked() {
 //
 
 PickFirst::SubchannelList::SubchannelList(RefCountedPtr<PickFirst> policy,
-                                          EndpointAddressesList addresses,
+                                          EndpointAddressesIterator* addresses,
                                           const ChannelArgs& args)
     : InternallyRefCounted<SubchannelList>(
           GRPC_TRACE_FLAG_ENABLED(grpc_lb_pick_first_trace) ? "SubchannelList"
@@ -1062,14 +1063,12 @@ PickFirst::SubchannelList::SubchannelList(RefCountedPtr<PickFirst> policy,
                 .Remove(
                     GRPC_ARG_INTERNAL_PICK_FIRST_OMIT_STATUS_MESSAGE_PREFIX)) {
   if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_pick_first_trace)) {
-    gpr_log(GPR_INFO,
-            "[PF %p] Creating subchannel list %p for %" PRIuPTR
-            " subchannels - channel args: %s",
-            policy_.get(), this, addresses.size(), args_.ToString().c_str());
+    gpr_log(GPR_INFO, "[PF %p] Creating subchannel list %p - channel args: %s",
+            policy_.get(), this, args_.ToString().c_str());
   }
-  subchannels_.reserve(addresses.size());
+  if (addresses == nullptr) return;
   // Create a subchannel for each address.
-  for (const EndpointAddresses& address : addresses) {
+  addresses->ForEach([&](const EndpointAddresses& address) {
     GPR_ASSERT(address.addresses().size() == 1);
     RefCountedPtr<SubchannelInterface> subchannel =
         policy_->channel_control_helper()->CreateSubchannel(
@@ -1081,7 +1080,7 @@ PickFirst::SubchannelList::SubchannelList(RefCountedPtr<PickFirst> policy,
                 "[PF %p] could not create subchannel for address %s, ignoring",
                 policy_.get(), address.ToString().c_str());
       }
-      continue;
+      return;
     }
     if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_pick_first_trace)) {
       gpr_log(GPR_INFO,
@@ -1090,8 +1089,8 @@ PickFirst::SubchannelList::SubchannelList(RefCountedPtr<PickFirst> policy,
               policy_.get(), this, subchannels_.size(), subchannel.get(),
               address.ToString().c_str());
     }
-    subchannels_.emplace_back(this, std::move(subchannel));
-  }
+    subchannels_.emplace_back(this, subchannels_.size(), std::move(subchannel));
+  });
 }
 
 PickFirst::SubchannelList::~SubchannelList() {
diff --git a/src/core/ext/filters/client_channel/lb_policy/priority/priority.cc b/src/core/ext/filters/client_channel/lb_policy/priority/priority.cc
index e1e21072bc0..cdfe6adceaf 100644
--- a/src/core/ext/filters/client_channel/lb_policy/priority/priority.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/priority/priority.cc
@@ -684,7 +684,8 @@ absl::Status PriorityLb::ChildPriority::UpdateLocked(
   if (priority_policy_->addresses_.ok()) {
     auto it = priority_policy_->addresses_->find(name_);
     if (it == priority_policy_->addresses_->end()) {
-      update_args.addresses.emplace();
+      update_args.addresses = std::make_shared<EndpointAddressesListIterator>(
+          EndpointAddressesList());
     } else {
       update_args.addresses = it->second;
     }
diff --git a/src/core/ext/filters/client_channel/lb_policy/ring_hash/ring_hash.cc b/src/core/ext/filters/client_channel/lb_policy/ring_hash/ring_hash.cc
index 5881f168c86..c1c52c7de5f 100644
--- a/src/core/ext/filters/client_channel/lb_policy/ring_hash/ring_hash.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/ring_hash/ring_hash.cc
@@ -554,7 +554,8 @@ void RingHash::RingHashEndpoint::UpdateChildPolicyLocked() {
   GPR_ASSERT(config.ok());
   // Update child policy.
   LoadBalancingPolicy::UpdateArgs update_args;
-  update_args.addresses.emplace().emplace_back(ring_hash_->endpoints_[index_]);
+  update_args.addresses =
+      std::make_shared<SingleEndpointIterator>(ring_hash_->endpoints_[index_]);
   update_args.args = ring_hash_->args_;
   update_args.config = std::move(*config);
   // TODO(roth): If the child reports a non-OK status with the update,
@@ -622,18 +623,14 @@ absl::Status RingHash::UpdateLocked(UpdateArgs args) {
   // Check address list.
   if (args.addresses.ok()) {
     if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_ring_hash_trace)) {
-      gpr_log(GPR_INFO, "[RH %p] received update with %" PRIuPTR " addresses",
-              this, args.addresses->size());
+      gpr_log(GPR_INFO, "[RH %p] received update", this);
     }
     // De-dup endpoints, taking weight into account.
     endpoints_.clear();
-    endpoints_.reserve(args.addresses->size());
     std::map<EndpointAddressSet, size_t> endpoint_indices;
-    size_t num_skipped = 0;
-    for (size_t i = 0; i < args.addresses->size(); ++i) {
-      EndpointAddresses& endpoint = (*args.addresses)[i];
+    (*args.addresses)->ForEach([&](const EndpointAddresses& endpoint) {
       const EndpointAddressSet key(endpoint.addresses());
-      auto p = endpoint_indices.emplace(key, i - num_skipped);
+      auto p = endpoint_indices.emplace(key, endpoints_.size());
       if (!p.second) {
         // Duplicate endpoint.  Combine weights and skip the dup.
         EndpointAddresses& prev_endpoint = endpoints_[p.first->second];
@@ -651,11 +648,10 @@ absl::Status RingHash::UpdateLocked(UpdateArgs args) {
             prev_endpoint.addresses(),
             prev_endpoint.args().Set(GRPC_ARG_ADDRESS_WEIGHT,
                                      weight_arg + prev_weight_arg));
-        ++num_skipped;
       } else {
-        endpoints_.push_back(std::move(endpoint));
+        endpoints_.push_back(endpoint);
       }
-    }
+    });
   } else {
     if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_ring_hash_trace)) {
       gpr_log(GPR_INFO, "[RH %p] received update with addresses error: %s",
diff --git a/src/core/ext/filters/client_channel/lb_policy/rls/rls.cc b/src/core/ext/filters/client_channel/lb_policy/rls/rls.cc
index f51ef89a0be..1521fafcfc4 100644
--- a/src/core/ext/filters/client_channel/lb_policy/rls/rls.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/rls/rls.cc
@@ -707,7 +707,7 @@ class RlsLb : public LoadBalancingPolicy {
   OrphanablePtr<RlsChannel> rls_channel_ ABSL_GUARDED_BY(mu_);
 
   // Accessed only from within WorkSerializer.
-  absl::StatusOr<EndpointAddressesList> addresses_;
+  absl::StatusOr<std::shared_ptr<EndpointAddressesIterator>> addresses_;
   ChannelArgs channel_args_;
   RefCountedPtr<RlsLbConfig> config_;
   RefCountedPtr<ChildPolicyWrapper> default_child_policy_;
@@ -1858,6 +1858,27 @@ RlsLb::RlsLb(Args args) : LoadBalancingPolicy(std::move(args)), cache_(this) {
   }
 }
 
+bool EndpointsEqual(
+    const absl::StatusOr<std::shared_ptr<EndpointAddressesIterator>> endpoints1,
+    const absl::StatusOr<std::shared_ptr<EndpointAddressesIterator>>
+        endpoints2) {
+  if (endpoints1.status() != endpoints2.status()) return false;
+  if (endpoints1.ok()) {
+    std::vector<EndpointAddresses> e1_list;
+    (*endpoints1)->ForEach([&](const EndpointAddresses& endpoint) {
+      e1_list.push_back(endpoint);
+    });
+    size_t i = 0;
+    bool different = false;
+    (*endpoints2)->ForEach([&](const EndpointAddresses& endpoint) {
+      if (endpoint != e1_list[i++]) different = true;
+    });
+    if (different) return false;
+    if (i != e1_list.size()) return false;
+  }
+  return true;
+}
+
 absl::Status RlsLb::UpdateLocked(UpdateArgs args) {
   if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_rls_trace)) {
     gpr_log(GPR_INFO, "[rlslb %p] policy updated", this);
@@ -1875,7 +1896,7 @@ absl::Status RlsLb::UpdateLocked(UpdateArgs args) {
   // Swap out addresses.
   // If the new address list is an error and we have an existing address list,
   // stick with the existing addresses.
-  absl::StatusOr<EndpointAddressesList> old_addresses;
+  absl::StatusOr<std::shared_ptr<EndpointAddressesIterator>> old_addresses;
   if (args.addresses.ok()) {
     old_addresses = std::move(addresses_);
     addresses_ = std::move(args.addresses);
@@ -1888,7 +1909,7 @@ absl::Status RlsLb::UpdateLocked(UpdateArgs args) {
   bool update_child_policies =
       old_config == nullptr ||
       old_config->child_policy_config() != config_->child_policy_config() ||
-      old_addresses != addresses_ || args.args != channel_args_;
+      !EndpointsEqual(old_addresses, addresses_) || args.args != channel_args_;
   // If default target changes, swap out child policy.
   bool created_default_child = false;
   if (old_config == nullptr ||
diff --git a/src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.cc b/src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.cc
index 51e89c8e5b3..1c893fb1dcb 100644
--- a/src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.cc
@@ -125,14 +125,14 @@ class OldRoundRobin : public LoadBalancingPolicy {
       : public SubchannelList<RoundRobinSubchannelList,
                               RoundRobinSubchannelData> {
    public:
-    RoundRobinSubchannelList(OldRoundRobin* policy, ServerAddressList addresses,
+    RoundRobinSubchannelList(OldRoundRobin* policy,
+                             EndpointAddressesIterator* addresses,
                              const ChannelArgs& args)
         : SubchannelList(policy,
                          (GRPC_TRACE_FLAG_ENABLED(grpc_lb_round_robin_trace)
                               ? "RoundRobinSubchannelList"
                               : nullptr),
-                         std::move(addresses), policy->channel_control_helper(),
-                         args) {
+                         addresses, policy->channel_control_helper(), args) {
       // Need to maintain a ref to the LB policy as long as we maintain
       // any references to subchannels, since the subchannels'
       // pollset_sets will include the LB policy's pollset_set.
@@ -277,13 +277,12 @@ void OldRoundRobin::ResetBackoffLocked() {
 }
 
 absl::Status OldRoundRobin::UpdateLocked(UpdateArgs args) {
-  ServerAddressList addresses;
+  EndpointAddressesIterator* addresses = nullptr;
   if (args.addresses.ok()) {
     if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_round_robin_trace)) {
-      gpr_log(GPR_INFO, "[RR %p] received update with %" PRIuPTR " addresses",
-              this, args.addresses->size());
+      gpr_log(GPR_INFO, "[RR %p] received update", this);
     }
-    addresses = std::move(*args.addresses);
+    addresses = args.addresses->get();
   } else {
     if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_round_robin_trace)) {
       gpr_log(GPR_INFO, "[RR %p] received update with address error: %s", this,
@@ -299,8 +298,8 @@ absl::Status OldRoundRobin::UpdateLocked(UpdateArgs args) {
     gpr_log(GPR_INFO, "[RR %p] replacing previous pending subchannel list %p",
             this, latest_pending_subchannel_list_.get());
   }
-  latest_pending_subchannel_list_ = MakeRefCounted<RoundRobinSubchannelList>(
-      this, std::move(addresses), args.args);
+  latest_pending_subchannel_list_ =
+      MakeRefCounted<RoundRobinSubchannelList>(this, addresses, args.args);
   latest_pending_subchannel_list_->StartWatchingLocked(args.args);
   // If the new list is empty, immediately promote it to
   // subchannel_list_ and report TRANSIENT_FAILURE.
@@ -524,7 +523,7 @@ class RoundRobin : public LoadBalancingPolicy {
   class RoundRobinEndpointList : public EndpointList {
    public:
     RoundRobinEndpointList(RefCountedPtr<RoundRobin> round_robin,
-                           const EndpointAddressesList& endpoints,
+                           EndpointAddressesIterator* endpoints,
                            const ChannelArgs& args)
         : EndpointList(std::move(round_robin),
                        GRPC_TRACE_FLAG_ENABLED(grpc_lb_round_robin_trace)
@@ -687,13 +686,12 @@ void RoundRobin::ResetBackoffLocked() {
 }
 
 absl::Status RoundRobin::UpdateLocked(UpdateArgs args) {
-  EndpointAddressesList addresses;
+  EndpointAddressesIterator* addresses = nullptr;
   if (args.addresses.ok()) {
     if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_round_robin_trace)) {
-      gpr_log(GPR_INFO, "[RR %p] received update with %" PRIuPTR " endpoints",
-              this, args.addresses->size());
+      gpr_log(GPR_INFO, "[RR %p] received update", this);
     }
-    addresses = std::move(*args.addresses);
+    addresses = args.addresses->get();
   } else {
     if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_round_robin_trace)) {
       gpr_log(GPR_INFO, "[RR %p] received update with address error: %s", this,
@@ -710,8 +708,7 @@ absl::Status RoundRobin::UpdateLocked(UpdateArgs args) {
             latest_pending_endpoint_list_.get());
   }
   latest_pending_endpoint_list_ = MakeOrphanable<RoundRobinEndpointList>(
-      Ref(DEBUG_LOCATION, "RoundRobinEndpointList"), std::move(addresses),
-      args.args);
+      Ref(DEBUG_LOCATION, "RoundRobinEndpointList"), addresses, args.args);
   // If the new list is empty, immediately promote it to
   // endpoint_list_ and report TRANSIENT_FAILURE.
   if (latest_pending_endpoint_list_->size() == 0) {
diff --git a/src/core/ext/filters/client_channel/lb_policy/subchannel_list.h b/src/core/ext/filters/client_channel/lb_policy/subchannel_list.h
index cb52ad92daa..b5076a9f492 100644
--- a/src/core/ext/filters/client_channel/lb_policy/subchannel_list.h
+++ b/src/core/ext/filters/client_channel/lb_policy/subchannel_list.h
@@ -42,6 +42,7 @@
 #include "src/core/lib/iomgr/iomgr_fwd.h"
 #include "src/core/lib/load_balancing/lb_policy.h"
 #include "src/core/lib/load_balancing/subchannel_interface.h"
+#include "src/core/lib/resolver/endpoint_addresses.h"
 #include "src/core/lib/resolver/server_address.h"
 #include "src/core/lib/transport/connectivity_state.h"
 
@@ -208,7 +209,7 @@ class SubchannelList : public DualRefCounted<SubchannelListType> {
 
  protected:
   SubchannelList(LoadBalancingPolicy* policy, const char* tracer,
-                 ServerAddressList addresses,
+                 EndpointAddressesIterator* addresses,
                  LoadBalancingPolicy::ChannelControlHelper* helper,
                  const ChannelArgs& args);
 
@@ -365,19 +366,18 @@ void SubchannelData<SubchannelListType, SubchannelDataType>::ShutdownLocked() {
 template <typename SubchannelListType, typename SubchannelDataType>
 SubchannelList<SubchannelListType, SubchannelDataType>::SubchannelList(
     LoadBalancingPolicy* policy, const char* tracer,
-    ServerAddressList addresses,
+    EndpointAddressesIterator* addresses,
     LoadBalancingPolicy::ChannelControlHelper* helper, const ChannelArgs& args)
     : DualRefCounted<SubchannelListType>(tracer),
       policy_(policy),
       tracer_(tracer) {
   if (GPR_UNLIKELY(tracer_ != nullptr)) {
-    gpr_log(GPR_INFO,
-            "[%s %p] Creating subchannel list %p for %" PRIuPTR " subchannels",
-            tracer_, policy, this, addresses.size());
+    gpr_log(GPR_INFO, "[%s %p] Creating subchannel list %p", tracer_, policy,
+            this);
   }
-  subchannels_.reserve(addresses.size());
+  if (addresses == nullptr) return;
   // Create a subchannel for each address.
-  for (ServerAddress address : addresses) {
+  addresses->ForEach([&](const EndpointAddresses& address) {
     RefCountedPtr<SubchannelInterface> subchannel =
         helper->CreateSubchannel(address.address(), address.args(), args);
     if (subchannel == nullptr) {
@@ -387,7 +387,7 @@ SubchannelList<SubchannelListType, SubchannelDataType>::SubchannelList(
                 "[%s %p] could not create subchannel for address %s, ignoring",
                 tracer_, policy_, address.ToString().c_str());
       }
-      continue;
+      return;
     }
     if (GPR_UNLIKELY(tracer_ != nullptr)) {
       gpr_log(GPR_INFO,
@@ -397,8 +397,8 @@ SubchannelList<SubchannelListType, SubchannelDataType>::SubchannelList(
               address.ToString().c_str());
     }
     subchannels_.emplace_back();
-    subchannels_.back().Init(this, std::move(address), std::move(subchannel));
-  }
+    subchannels_.back().Init(this, address, std::move(subchannel));
+  });
 }
 
 template <typename SubchannelListType, typename SubchannelDataType>
diff --git a/src/core/ext/filters/client_channel/lb_policy/weighted_round_robin/weighted_round_robin.cc b/src/core/ext/filters/client_channel/lb_policy/weighted_round_robin/weighted_round_robin.cc
index 102cd6aa7cf..aa2c6f5bb66 100644
--- a/src/core/ext/filters/client_channel/lb_policy/weighted_round_robin/weighted_round_robin.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/weighted_round_robin/weighted_round_robin.cc
@@ -247,14 +247,13 @@ class OldWeightedRoundRobin : public LoadBalancingPolicy {
                               WeightedRoundRobinSubchannelData> {
    public:
     WeightedRoundRobinSubchannelList(OldWeightedRoundRobin* policy,
-                                     ServerAddressList addresses,
+                                     EndpointAddressesIterator* addresses,
                                      const ChannelArgs& args)
         : SubchannelList(policy,
                          (GRPC_TRACE_FLAG_ENABLED(grpc_lb_wrr_trace)
                               ? "WeightedRoundRobinSubchannelList"
                               : nullptr),
-                         std::move(addresses), policy->channel_control_helper(),
-                         args) {
+                         addresses, policy->channel_control_helper(), args) {
       // Need to maintain a ref to the LB policy as long as we maintain
       // any references to subchannels, since the subchannels'
       // pollset_sets will include the LB policy's pollset_set.
@@ -675,11 +674,10 @@ void OldWeightedRoundRobin::ResetBackoffLocked() {
 absl::Status OldWeightedRoundRobin::UpdateLocked(UpdateArgs args) {
   global_stats().IncrementWrrUpdates();
   config_ = std::move(args.config);
-  ServerAddressList addresses;
+  std::shared_ptr<EndpointAddressesIterator> addresses;
   if (args.addresses.ok()) {
     if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_wrr_trace)) {
-      gpr_log(GPR_INFO, "[WRR %p] received update with %" PRIuPTR " addresses",
-              this, args.addresses->size());
+      gpr_log(GPR_INFO, "[WRR %p] received update", this);
     }
     // Weed out duplicate addresses.  Also sort the addresses so that if
     // the set of the addresses don't change, their indexes in the
@@ -698,10 +696,12 @@ absl::Status OldWeightedRoundRobin::UpdateLocked(UpdateArgs args) {
         return memcmp(addr1.addr, addr2.addr, addr1.len) < 0;
       }
     };
-    std::set<ServerAddress, AddressLessThan> ordered_addresses(
-        args.addresses->begin(), args.addresses->end());
-    addresses =
-        ServerAddressList(ordered_addresses.begin(), ordered_addresses.end());
+    std::set<ServerAddress, AddressLessThan> ordered_addresses;
+    (*args.addresses)->ForEach([&](const EndpointAddresses& endpoint) {
+      ordered_addresses.insert(endpoint);
+    });
+    addresses = std::make_shared<EndpointAddressesListIterator>(
+        ServerAddressList(ordered_addresses.begin(), ordered_addresses.end()));
   } else {
     if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_wrr_trace)) {
       gpr_log(GPR_INFO, "[WRR %p] received update with address error: %s", this,
@@ -718,8 +718,8 @@ absl::Status OldWeightedRoundRobin::UpdateLocked(UpdateArgs args) {
             this, latest_pending_subchannel_list_.get());
   }
   latest_pending_subchannel_list_ =
-      MakeRefCounted<WeightedRoundRobinSubchannelList>(
-          this, std::move(addresses), args.args);
+      MakeRefCounted<WeightedRoundRobinSubchannelList>(this, addresses.get(),
+                                                       args.args);
   latest_pending_subchannel_list_->StartWatchingLocked(args.args);
   // If the new list is empty, immediately promote it to
   // subchannel_list_ and report TRANSIENT_FAILURE.
@@ -1079,7 +1079,7 @@ class WeightedRoundRobin : public LoadBalancingPolicy {
     };
 
     WrrEndpointList(RefCountedPtr<WeightedRoundRobin> wrr,
-                    const EndpointAddressesList& endpoints,
+                    EndpointAddressesIterator* endpoints,
                     const ChannelArgs& args)
         : EndpointList(std::move(wrr),
                        GRPC_TRACE_FLAG_ENABLED(grpc_lb_wrr_trace)
@@ -1516,11 +1516,10 @@ void WeightedRoundRobin::ResetBackoffLocked() {
 absl::Status WeightedRoundRobin::UpdateLocked(UpdateArgs args) {
   global_stats().IncrementWrrUpdates();
   config_ = std::move(args.config);
-  EndpointAddressesList addresses;
+  std::shared_ptr<EndpointAddressesIterator> addresses;
   if (args.addresses.ok()) {
     if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_wrr_trace)) {
-      gpr_log(GPR_INFO, "[WRR %p] received update with %" PRIuPTR " addresses",
-              this, args.addresses->size());
+      gpr_log(GPR_INFO, "[WRR %p] received update", this);
     }
     // Weed out duplicate endpoints.  Also sort the endpoints so that if
     // the set of endpoints doesn't change, their indexes in the endpoint
@@ -1539,10 +1538,13 @@ absl::Status WeightedRoundRobin::UpdateLocked(UpdateArgs args) {
         return e1 < e2;
       }
     };
-    std::set<EndpointAddresses, EndpointAddressesLessThan> ordered_addresses(
-        args.addresses->begin(), args.addresses->end());
-    addresses = EndpointAddressesList(ordered_addresses.begin(),
-                                      ordered_addresses.end());
+    std::set<EndpointAddresses, EndpointAddressesLessThan> ordered_addresses;
+    (*args.addresses)->ForEach([&](const EndpointAddresses& endpoint) {
+      ordered_addresses.insert(endpoint);
+    });
+    addresses =
+        std::make_shared<EndpointAddressesListIterator>(EndpointAddressesList(
+            ordered_addresses.begin(), ordered_addresses.end()));
   } else {
     if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_wrr_trace)) {
       gpr_log(GPR_INFO, "[WRR %p] received update with address error: %s", this,
@@ -1559,7 +1561,7 @@ absl::Status WeightedRoundRobin::UpdateLocked(UpdateArgs args) {
             this, latest_pending_endpoint_list_.get());
   }
   latest_pending_endpoint_list_ =
-      MakeOrphanable<WrrEndpointList>(Ref(), std::move(addresses), args.args);
+      MakeOrphanable<WrrEndpointList>(Ref(), addresses.get(), args.args);
   // If the new list is empty, immediately promote it to
   // endpoint_list_ and report TRANSIENT_FAILURE.
   if (latest_pending_endpoint_list_->size() == 0) {
diff --git a/src/core/ext/filters/client_channel/lb_policy/weighted_target/weighted_target.cc b/src/core/ext/filters/client_channel/lb_policy/weighted_target/weighted_target.cc
index eecd112445a..0639ce9b094 100644
--- a/src/core/ext/filters/client_channel/lb_policy/weighted_target/weighted_target.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/weighted_target/weighted_target.cc
@@ -157,10 +157,10 @@ class WeightedTargetLb : public LoadBalancingPolicy {
 
     void Orphan() override;
 
-    absl::Status UpdateLocked(const WeightedTargetLbConfig::ChildConfig& config,
-                              absl::StatusOr<EndpointAddressesList> addresses,
-                              const std::string& resolution_note,
-                              const ChannelArgs& args);
+    absl::Status UpdateLocked(
+        const WeightedTargetLbConfig::ChildConfig& config,
+        absl::StatusOr<std::shared_ptr<EndpointAddressesIterator>> addresses,
+        const std::string& resolution_note, const ChannelArgs& args);
     void ResetBackoffLocked();
     void DeactivateLocked();
 
@@ -338,11 +338,12 @@ absl::Status WeightedTargetLb::UpdateLocked(UpdateArgs args) {
       target = MakeOrphanable<WeightedChild>(
           Ref(DEBUG_LOCATION, "WeightedChild"), name);
     }
-    absl::StatusOr<EndpointAddressesList> addresses;
+    absl::StatusOr<std::shared_ptr<EndpointAddressesIterator>> addresses;
     if (address_map.ok()) {
       auto it = address_map->find(name);
       if (it == address_map->end()) {
-        addresses.emplace();
+        addresses = std::make_shared<EndpointAddressesListIterator>(
+            EndpointAddressesList());
       } else {
         addresses = std::move(it->second);
       }
@@ -589,7 +590,7 @@ WeightedTargetLb::WeightedChild::CreateChildPolicyLocked(
 
 absl::Status WeightedTargetLb::WeightedChild::UpdateLocked(
     const WeightedTargetLbConfig::ChildConfig& config,
-    absl::StatusOr<EndpointAddressesList> addresses,
+    absl::StatusOr<std::shared_ptr<EndpointAddressesIterator>> addresses,
     const std::string& resolution_note, const ChannelArgs& args) {
   if (weighted_target_policy_->shutting_down_) return absl::OkStatus();
   // Update child weight.
diff --git a/src/core/ext/filters/client_channel/lb_policy/xds/cds.cc b/src/core/ext/filters/client_channel/lb_policy/xds/cds.cc
index f1278b98ae4..7e42338d70d 100644
--- a/src/core/ext/filters/client_channel/lb_policy/xds/cds.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/xds/cds.cc
@@ -199,8 +199,24 @@ class CdsLb : public LoadBalancingPolicy {
   // The root of the tree is config_->cluster().
   std::map<std::string, WatcherState> watchers_;
 
+  // TODO(roth, yashkt): These are here because we need to handle
+  // pollset_set linkage as clusters are added or removed from the
+  // XdsCertificateProvider.  However, in the aggregate cluster case,
+  // there may be multiple clusters in the same cert provider, and we're
+  // only tracking the cert providers for the most recent underlying
+  // cluster here.  I think this is a bug that could cause us to starve
+  // the underlying cert providers of polling.  However, it is not
+  // actually causing any problem in practice today, because (a) we have
+  // no cert provider impl that relies on gRPC's polling and (b)
+  // probably no one is actually configuring an aggregate cluster with
+  // different cert providers in different underlying clusters.
+  // Hopefully, this problem won't be an issue in practice until after
+  // the EventEngine migration is done, at which point the need for
+  // handling pollset_set linkage will go away, and these fields can
+  // simply be removed.
   RefCountedPtr<grpc_tls_certificate_provider> root_certificate_provider_;
   RefCountedPtr<grpc_tls_certificate_provider> identity_certificate_provider_;
+
   RefCountedPtr<XdsCertificateProvider> xds_certificate_provider_;
 
   // Child LB policy.
diff --git a/src/core/ext/filters/client_channel/lb_policy/xds/xds_cluster_impl.cc b/src/core/ext/filters/client_channel/lb_policy/xds/xds_cluster_impl.cc
index 50740151c9d..8548de565d6 100644
--- a/src/core/ext/filters/client_channel/lb_policy/xds/xds_cluster_impl.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/xds/xds_cluster_impl.cc
@@ -250,7 +250,7 @@ class XdsClusterImplLb : public LoadBalancingPolicy {
   OrphanablePtr<LoadBalancingPolicy> CreateChildPolicyLocked(
       const ChannelArgs& args);
   absl::Status UpdateChildPolicyLocked(
-      absl::StatusOr<EndpointAddressesList> addresses,
+      absl::StatusOr<std::shared_ptr<EndpointAddressesIterator>> addresses,
       std::string resolution_note, const ChannelArgs& args);
 
   void MaybeUpdatePickerLocked();
@@ -569,7 +569,7 @@ OrphanablePtr<LoadBalancingPolicy> XdsClusterImplLb::CreateChildPolicyLocked(
 }
 
 absl::Status XdsClusterImplLb::UpdateChildPolicyLocked(
-    absl::StatusOr<EndpointAddressesList> addresses,
+    absl::StatusOr<std::shared_ptr<EndpointAddressesIterator>> addresses,
     std::string resolution_note, const ChannelArgs& args) {
   // Create policy if needed.
   if (child_policy_ == nullptr) {
diff --git a/src/core/ext/filters/client_channel/lb_policy/xds/xds_cluster_manager.cc b/src/core/ext/filters/client_channel/lb_policy/xds/xds_cluster_manager.cc
index 4f6e8611b5a..e613b3eb0d2 100644
--- a/src/core/ext/filters/client_channel/lb_policy/xds/xds_cluster_manager.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/xds/xds_cluster_manager.cc
@@ -149,7 +149,8 @@ class XdsClusterManagerLb : public LoadBalancingPolicy {
 
     absl::Status UpdateLocked(
         RefCountedPtr<LoadBalancingPolicy::Config> config,
-        const absl::StatusOr<EndpointAddressesList>& addresses,
+        const absl::StatusOr<std::shared_ptr<EndpointAddressesIterator>>&
+            addresses,
         const ChannelArgs& args);
     void ExitIdleLocked();
     void ResetBackoffLocked();
@@ -482,7 +483,7 @@ XdsClusterManagerLb::ClusterChild::CreateChildPolicyLocked(
 
 absl::Status XdsClusterManagerLb::ClusterChild::UpdateLocked(
     RefCountedPtr<LoadBalancingPolicy::Config> config,
-    const absl::StatusOr<EndpointAddressesList>& addresses,
+    const absl::StatusOr<std::shared_ptr<EndpointAddressesIterator>>& addresses,
     const ChannelArgs& args) {
   if (xds_cluster_manager_policy_->shutting_down_) return absl::OkStatus();
   // Update child weight.
diff --git a/src/core/ext/filters/client_channel/lb_policy/xds/xds_cluster_resolver.cc b/src/core/ext/filters/client_channel/lb_policy/xds/xds_cluster_resolver.cc
index 42f8673e724..6a58213347a 100644
--- a/src/core/ext/filters/client_channel/lb_policy/xds/xds_cluster_resolver.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/xds/xds_cluster_resolver.cc
@@ -28,6 +28,7 @@
 #include <utility>
 #include <vector>
 
+#include "absl/functional/function_ref.h"
 #include "absl/status/status.h"
 #include "absl/status/statusor.h"
 #include "absl/strings/str_cat.h"
@@ -61,6 +62,7 @@
 #include "src/core/lib/gprpp/validation_errors.h"
 #include "src/core/lib/gprpp/work_serializer.h"
 #include "src/core/lib/iomgr/pollset_set.h"
+#include "src/core/lib/iomgr/resolved_address.h"
 #include "src/core/lib/json/json.h"
 #include "src/core/lib/json/json_args.h"
 #include "src/core/lib/json/json_object_loader.h"
@@ -390,7 +392,7 @@ class XdsClusterResolverLb : public LoadBalancingPolicy {
   absl::Status UpdateChildPolicyLocked();
   OrphanablePtr<LoadBalancingPolicy> CreateChildPolicyLocked(
       const ChannelArgs& args);
-  EndpointAddressesList CreateChildPolicyAddressesLocked();
+  std::shared_ptr<EndpointAddressesIterator> CreateChildPolicyAddressesLocked();
   std::string CreateChildPolicyResolutionNoteLocked();
   RefCountedPtr<Config> CreateChildPolicyConfigLocked();
   ChannelArgs CreateChildPolicyArgsLocked(const ChannelArgs& args_in);
@@ -529,10 +531,16 @@ XdsClusterResolverLb::DiscoveryMechanismEntry::config() const {
       ->config_->discovery_mechanisms()[discovery_mechanism->index()];
 }
 
+std::string MakeChildPolicyName(absl::string_view cluster_name,
+                                size_t child_number) {
+  return absl::StrCat("{cluster=", cluster_name,
+                      ", child_number=", child_number, "}");
+}
+
 std::string XdsClusterResolverLb::DiscoveryMechanismEntry::GetChildPolicyName(
     size_t priority) const {
-  return absl::StrCat("{cluster=", config().cluster_name,
-                      ", child_number=", priority_child_numbers[priority], "}");
+  return MakeChildPolicyName(config().cluster_name,
+                             priority_child_numbers[priority]);
 }
 
 //
@@ -768,39 +776,76 @@ void XdsClusterResolverLb::OnResourceDoesNotExist(size_t index,
 // child policy-related methods
 //
 
-EndpointAddressesList XdsClusterResolverLb::CreateChildPolicyAddressesLocked() {
-  EndpointAddressesList addresses;
-  for (const auto& discovery_entry : discovery_mechanisms_) {
-    const auto& priority_list =
-        GetUpdatePriorityList(*discovery_entry.latest_update);
-    for (size_t priority = 0; priority < priority_list.size(); ++priority) {
-      const auto& priority_entry = priority_list[priority];
-      std::string priority_child_name =
-          discovery_entry.GetChildPolicyName(priority);
-      for (const auto& p : priority_entry.localities) {
-        const auto& locality_name = p.first;
-        const auto& locality = p.second;
-        std::vector<RefCountedStringValue> hierarchical_path = {
-            RefCountedStringValue(priority_child_name),
-            RefCountedStringValue(locality_name->AsHumanReadableString())};
-        auto hierarchical_path_attr =
-            MakeRefCounted<HierarchicalPathArg>(std::move(hierarchical_path));
-        for (const auto& endpoint : locality.endpoints) {
-          uint32_t endpoint_weight =
-              locality.lb_weight *
-              endpoint.args().GetInt(GRPC_ARG_ADDRESS_WEIGHT).value_or(1);
-          addresses.emplace_back(
-              endpoint.addresses(),
-              endpoint.args()
-                  .SetObject(hierarchical_path_attr)
-                  .Set(GRPC_ARG_ADDRESS_WEIGHT, endpoint_weight)
-                  .SetObject(locality_name->Ref())
-                  .Set(GRPC_ARG_XDS_LOCALITY_WEIGHT, locality.lb_weight));
+class PriorityEndpointIterator : public EndpointAddressesIterator {
+ public:
+  struct DiscoveryMechanismResult {
+    std::shared_ptr<const XdsEndpointResource> update;
+    std::string cluster_name;
+    std::vector<size_t /*child_number*/> priority_child_numbers;
+
+    DiscoveryMechanismResult(
+        std::shared_ptr<const XdsEndpointResource> resource,
+        std::string cluster, std::vector<size_t> child_numbers)
+        : update(std::move(resource)),
+          cluster_name(std::move(cluster)),
+          priority_child_numbers(std::move(child_numbers)) {}
+
+    std::string GetChildPolicyName(size_t priority) const {
+      return MakeChildPolicyName(cluster_name,
+                                 priority_child_numbers[priority]);
+    }
+  };
+
+  explicit PriorityEndpointIterator(
+      std::vector<DiscoveryMechanismResult> results)
+      : results_(std::move(results)) {}
+
+  void ForEach(absl::FunctionRef<void(const EndpointAddresses&)> callback)
+      const override {
+    for (const auto& entry : results_) {
+      const auto& priority_list = GetUpdatePriorityList(*entry.update);
+      for (size_t priority = 0; priority < priority_list.size(); ++priority) {
+        const auto& priority_entry = priority_list[priority];
+        std::string priority_child_name = entry.GetChildPolicyName(priority);
+        for (const auto& p : priority_entry.localities) {
+          const auto& locality_name = p.first;
+          const auto& locality = p.second;
+          std::vector<RefCountedStringValue> hierarchical_path = {
+              RefCountedStringValue(priority_child_name),
+              RefCountedStringValue(locality_name->AsHumanReadableString())};
+          auto hierarchical_path_attr =
+              MakeRefCounted<HierarchicalPathArg>(std::move(hierarchical_path));
+          for (const auto& endpoint : locality.endpoints) {
+            uint32_t endpoint_weight =
+                locality.lb_weight *
+                endpoint.args().GetInt(GRPC_ARG_ADDRESS_WEIGHT).value_or(1);
+            callback(EndpointAddresses(
+                endpoint.addresses(),
+                endpoint.args()
+                    .SetObject(hierarchical_path_attr)
+                    .Set(GRPC_ARG_ADDRESS_WEIGHT, endpoint_weight)
+                    .SetObject(locality_name->Ref())
+                    .Set(GRPC_ARG_XDS_LOCALITY_WEIGHT, locality.lb_weight)));
+          }
         }
       }
     }
   }
-  return addresses;
+
+ private:
+  std::vector<DiscoveryMechanismResult> results_;
+};
+
+std::shared_ptr<EndpointAddressesIterator>
+XdsClusterResolverLb::CreateChildPolicyAddressesLocked() {
+  std::vector<PriorityEndpointIterator::DiscoveryMechanismResult> entries;
+  entries.reserve(discovery_mechanisms_.size());
+  for (const auto& discovery_entry : discovery_mechanisms_) {
+    entries.emplace_back(discovery_entry.latest_update,
+                         discovery_entry.config().cluster_name,
+                         discovery_entry.priority_child_numbers);
+  }
+  return std::make_shared<PriorityEndpointIterator>(std::move(entries));
 }
 
 std::string XdsClusterResolverLb::CreateChildPolicyResolutionNoteLocked() {
diff --git a/src/core/ext/filters/client_channel/lb_policy/xds/xds_override_host.cc b/src/core/ext/filters/client_channel/lb_policy/xds/xds_override_host.cc
index 7a1c6792a6c..c42219b4c42 100644
--- a/src/core/ext/filters/client_channel/lb_policy/xds/xds_override_host.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/xds/xds_override_host.cc
@@ -18,7 +18,6 @@
 
 #include "src/core/ext/filters/client_channel/lb_policy/xds/xds_override_host.h"
 
-#include <inttypes.h>
 #include <stddef.h>
 
 #include <algorithm>
@@ -34,6 +33,7 @@
 #include <vector>
 
 #include "absl/base/thread_annotations.h"
+#include "absl/functional/function_ref.h"
 #include "absl/status/status.h"
 #include "absl/status/statusor.h"
 #include "absl/strings/str_cat.h"
@@ -300,8 +300,7 @@ class XdsOverrideHostLb : public LoadBalancingPolicy {
 
   void MaybeUpdatePickerLocked();
 
-  absl::StatusOr<EndpointAddressesList> UpdateAddressMap(
-      absl::StatusOr<EndpointAddressesList> endpoints);
+  void UpdateAddressMap(const EndpointAddressesIterator& endpoints);
 
   RefCountedPtr<SubchannelWrapper> AdoptSubchannel(
       const grpc_resolved_address& address,
@@ -508,12 +507,36 @@ void XdsOverrideHostLb::ResetBackoffLocked() {
   if (child_policy_ != nullptr) child_policy_->ResetBackoffLocked();
 }
 
+// Wraps the endpoint iterator and filters out endpoints in state DRAINING.
+class ChildEndpointIterator : public EndpointAddressesIterator {
+ public:
+  explicit ChildEndpointIterator(
+      std::shared_ptr<EndpointAddressesIterator> parent_it)
+      : parent_it_(std::move(parent_it)) {}
+
+  void ForEach(absl::FunctionRef<void(const EndpointAddresses&)> callback)
+      const override {
+    parent_it_->ForEach([&](const EndpointAddresses& endpoint) {
+      XdsHealthStatus status = GetEndpointHealthStatus(endpoint);
+      if (status.status() != XdsHealthStatus::kDraining) {
+        if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_xds_override_host_trace)) {
+          gpr_log(GPR_INFO,
+                  "[xds_override_host_lb %p] endpoint %s: not draining, "
+                  "passing to child",
+                  this, endpoint.ToString().c_str());
+        }
+        callback(endpoint);
+      }
+    });
+  }
+
+ private:
+  std::shared_ptr<EndpointAddressesIterator> parent_it_;
+};
+
 absl::Status XdsOverrideHostLb::UpdateLocked(UpdateArgs args) {
   if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_xds_override_host_trace)) {
-    gpr_log(GPR_INFO,
-            "[xds_override_host_lb %p] Received update with %" PRIuPTR
-            " addresses",
-            this, args.addresses.ok() ? args.addresses->size() : 0);
+    gpr_log(GPR_INFO, "[xds_override_host_lb %p] Received update", this);
   }
   auto old_config = std::move(config_);
   // Update config.
@@ -521,13 +544,24 @@ absl::Status XdsOverrideHostLb::UpdateLocked(UpdateArgs args) {
   if (config_ == nullptr) {
     return absl::InvalidArgumentError("Missing policy config");
   }
+  // Update address map and wrap endpoint iterator for child policy.
+  if (args.addresses.ok()) {
+    UpdateAddressMap(**args.addresses);
+    args.addresses =
+        std::make_shared<ChildEndpointIterator>(std::move(*args.addresses));
+  } else {
+    if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_xds_override_host_trace)) {
+      gpr_log(GPR_INFO, "[xds_override_host_lb %p] address error: %s", this,
+              args.addresses.status().ToString().c_str());
+    }
+  }
   // Create child policy if needed.
   if (child_policy_ == nullptr) {
     child_policy_ = CreateChildPolicyLocked(args.args);
   }
   // Update child policy.
   UpdateArgs update_args;
-  update_args.addresses = UpdateAddressMap(std::move(args.addresses));
+  update_args.addresses = std::move(args.addresses);
   update_args.resolution_note = std::move(args.resolution_note);
   update_args.config = config_->child_config();
   update_args.args = std::move(args.args);
@@ -578,18 +612,9 @@ OrphanablePtr<LoadBalancingPolicy> XdsOverrideHostLb::CreateChildPolicyLocked(
   return lb_policy;
 }
 
-absl::StatusOr<EndpointAddressesList> XdsOverrideHostLb::UpdateAddressMap(
-    absl::StatusOr<EndpointAddressesList> endpoints) {
-  if (!endpoints.ok()) {
-    if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_xds_override_host_trace)) {
-      gpr_log(GPR_INFO, "[xds_override_host_lb %p] address error: %s", this,
-              endpoints.status().ToString().c_str());
-    }
-    return endpoints;
-  }
-  // Construct the list of addresses to pass to the child policy and a
-  // map of address info from which to update subchannel_map_.
-  EndpointAddressesList child_addresses;
+void XdsOverrideHostLb::UpdateAddressMap(
+    const EndpointAddressesIterator& endpoints) {
+  // Construct a map of address info from which to update subchannel_map_.
   struct AddressInfo {
     XdsHealthStatus eds_health_status;
     RefCountedStringValue address_list;
@@ -597,25 +622,18 @@ absl::StatusOr<EndpointAddressesList> XdsOverrideHostLb::UpdateAddressMap(
         : eds_health_status(status), address_list(std::move(addresses)) {}
   };
   std::map<const std::string, AddressInfo> addresses_for_map;
-  for (const auto& endpoint : *endpoints) {
+  endpoints.ForEach([&](const EndpointAddresses& endpoint) {
     XdsHealthStatus status = GetEndpointHealthStatus(endpoint);
-    if (status.status() != XdsHealthStatus::kDraining) {
-      if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_xds_override_host_trace)) {
-        gpr_log(GPR_INFO,
-                "[xds_override_host_lb %p] endpoint %s: not draining, "
-                "passing to child",
-                this, endpoint.ToString().c_str());
-      }
-      child_addresses.push_back(endpoint);
-    } else if (!config_->override_host_status_set().Contains(status)) {
-      // Skip draining hosts if not in the override status set.
+    // Skip draining hosts if not in the override status set.
+    if (status.status() == XdsHealthStatus::kDraining &&
+        !config_->override_host_status_set().Contains(status)) {
       if (GRPC_TRACE_FLAG_ENABLED(grpc_lb_xds_override_host_trace)) {
         gpr_log(GPR_INFO,
                 "[xds_override_host_lb %p] endpoint %s: draining but not in "
                 "override_host_status set -- ignoring",
                 this, endpoint.ToString().c_str());
       }
-      continue;
+      return;
     }
     std::vector<std::string> addresses;
     addresses.reserve(endpoint.addresses().size());
@@ -641,7 +659,7 @@ absl::StatusOr<EndpointAddressesList> XdsOverrideHostLb::UpdateAddressMap(
           std::piecewise_construct, std::forward_as_tuple(addresses[i]),
           std::forward_as_tuple(status, std::move(address_list)));
     }
-  }
+  });
   // Now grab the lock and update subchannel_map_ from addresses_for_map.
   {
     MutexLock lock(&subchannel_map_mu_);
@@ -688,7 +706,6 @@ absl::StatusOr<EndpointAddressesList> XdsOverrideHostLb::UpdateAddressMap(
       it->second.set_address_list(std::move(address_info.address_list));
     }
   }
-  return child_addresses;
 }
 
 RefCountedPtr<XdsOverrideHostLb::SubchannelWrapper>
diff --git a/src/core/ext/filters/client_channel/lb_policy/xds/xds_wrr_locality.cc b/src/core/ext/filters/client_channel/lb_policy/xds/xds_wrr_locality.cc
index 26f0ec9084a..2d346217e47 100644
--- a/src/core/ext/filters/client_channel/lb_policy/xds/xds_wrr_locality.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/xds/xds_wrr_locality.cc
@@ -21,7 +21,6 @@
 #include <memory>
 #include <string>
 #include <utility>
-#include <vector>
 
 #include "absl/status/status.h"
 #include "absl/status/statusor.h"
@@ -170,10 +169,10 @@ absl::Status XdsWrrLocalityLb::UpdateLocked(UpdateArgs args) {
   // Scan the addresses to find the weight for each locality.
   std::map<std::string, uint32_t> locality_weights;
   if (args.addresses.ok()) {
-    for (const auto& address : *args.addresses) {
-      auto* locality_name = address.args().GetObject<XdsLocalityName>();
+    (*args.addresses)->ForEach([&](const EndpointAddresses& endpoint) {
+      auto* locality_name = endpoint.args().GetObject<XdsLocalityName>();
       uint32_t weight =
-          address.args().GetInt(GRPC_ARG_XDS_LOCALITY_WEIGHT).value_or(0);
+          endpoint.args().GetInt(GRPC_ARG_XDS_LOCALITY_WEIGHT).value_or(0);
       if (locality_name != nullptr && weight > 0) {
         auto p = locality_weights.emplace(
             locality_name->AsHumanReadableString(), weight);
@@ -184,7 +183,7 @@ absl::Status XdsWrrLocalityLb::UpdateLocked(UpdateArgs args) {
                   p.first->first.c_str(), p.first->second, weight);
         }
       }
-    }
+    });
   }
   // Construct the config for the weighted_target policy.
   Json::Object weighted_targets;
diff --git a/src/core/lib/event_engine/posix_engine/timer_manager.cc b/src/core/lib/event_engine/posix_engine/timer_manager.cc
index 2962f7a2eb9..4df2dc7ba28 100644
--- a/src/core/lib/event_engine/posix_engine/timer_manager.cc
+++ b/src/core/lib/event_engine/posix_engine/timer_manager.cc
@@ -30,7 +30,6 @@
 #include <grpc/support/time.h>
 
 #include "src/core/lib/debug/trace.h"
-#include "src/core/lib/gprpp/thd.h"
 
 static thread_local bool g_timer_thread;
 
@@ -67,41 +66,32 @@ bool TimerManager::WaitUntil(grpc_core::Timestamp next) {
 }
 
 void TimerManager::MainLoop() {
-  for (;;) {
-    grpc_core::Timestamp next = grpc_core::Timestamp::InfFuture();
-    absl::optional<std::vector<experimental::EventEngine::Closure*>>
-        check_result = timer_list_->TimerCheck(&next);
-    GPR_ASSERT(check_result.has_value() &&
-               "ERROR: More than one MainLoop is running.");
-    if (!check_result->empty()) {
-      RunSomeTimers(std::move(*check_result));
-      continue;
-    }
-    if (!WaitUntil(next)) break;
+  grpc_core::Timestamp next = grpc_core::Timestamp::InfFuture();
+  absl::optional<std::vector<experimental::EventEngine::Closure*>>
+      check_result = timer_list_->TimerCheck(&next);
+  GPR_ASSERT(check_result.has_value() &&
+             "ERROR: More than one MainLoop is running.");
+  bool timers_found = !check_result->empty();
+  if (timers_found) {
+    RunSomeTimers(std::move(*check_result));
   }
-  main_loop_exit_signal_->Notify();
+  thread_pool_->Run([this, next, timers_found]() {
+    if (!timers_found && !WaitUntil(next)) {
+      main_loop_exit_signal_->Notify();
+      return;
+    }
+    MainLoop();
+  });
 }
 
 bool TimerManager::IsTimerManagerThread() { return g_timer_thread; }
 
-void TimerManager::StartMainLoopThread() {
-  main_thread_ = grpc_core::Thread(
-      "timer_manager",
-      [](void* arg) {
-        auto self = static_cast<TimerManager*>(arg);
-        self->MainLoop();
-      },
-      this, nullptr,
-      grpc_core::Thread::Options().set_tracked(false).set_joinable(false));
-  main_thread_.Start();
-}
-
 TimerManager::TimerManager(
     std::shared_ptr<grpc_event_engine::experimental::ThreadPool> thread_pool)
     : host_(this), thread_pool_(std::move(thread_pool)) {
   timer_list_ = std::make_unique<TimerList>(&host_);
   main_loop_exit_signal_.emplace();
-  StartMainLoopThread();
+  thread_pool_->Run([this]() { MainLoop(); });
 }
 
 grpc_core::Timestamp TimerManager::Host::Now() {
@@ -162,7 +152,7 @@ void TimerManager::RestartPostFork() {
   }
   shutdown_ = false;
   main_loop_exit_signal_.emplace();
-  StartMainLoopThread();
+  thread_pool_->Run([this]() { MainLoop(); });
 }
 
 void TimerManager::PrepareFork() { Shutdown(); }
diff --git a/src/core/lib/event_engine/posix_engine/timer_manager.h b/src/core/lib/event_engine/posix_engine/timer_manager.h
index 89d547a5ce7..5cd634c51b0 100644
--- a/src/core/lib/event_engine/posix_engine/timer_manager.h
+++ b/src/core/lib/event_engine/posix_engine/timer_manager.h
@@ -36,7 +36,6 @@
 #include "src/core/lib/event_engine/thread_pool/thread_pool.h"
 #include "src/core/lib/gprpp/notification.h"
 #include "src/core/lib/gprpp/sync.h"
-#include "src/core/lib/gprpp/thd.h"
 #include "src/core/lib/gprpp/time.h"
 
 namespace grpc_event_engine {
@@ -80,7 +79,6 @@ class TimerManager final : public grpc_event_engine::experimental::Forkable {
     TimerManager* const timer_manager_;
   };
 
-  void StartMainLoopThread();
   void RestartPostFork();
   void MainLoop();
   void RunSomeTimers(std::vector<experimental::EventEngine::Closure*> timers);
@@ -103,7 +101,6 @@ class TimerManager final : public grpc_event_engine::experimental::Forkable {
   uint64_t wakeups_ ABSL_GUARDED_BY(mu_) = false;
   // actual timer implementation
   std::unique_ptr<TimerList> timer_list_;
-  grpc_core::Thread main_thread_;
   std::shared_ptr<grpc_event_engine::experimental::ThreadPool> thread_pool_;
   absl::optional<grpc_core::Notification> main_loop_exit_signal_;
 };
diff --git a/src/core/lib/gprpp/ref_counted_string.h b/src/core/lib/gprpp/ref_counted_string.h
index 62fb15ded98..dbe32b113da 100644
--- a/src/core/lib/gprpp/ref_counted_string.h
+++ b/src/core/lib/gprpp/ref_counted_string.h
@@ -104,6 +104,19 @@ inline bool operator==(const RefCountedStringValue& lhs,
   return lhs.as_string_view() == rhs.as_string_view();
 }
 
+inline bool operator!=(const RefCountedStringValue& lhs,
+                       absl::string_view rhs) {
+  return lhs.as_string_view() != rhs;
+}
+inline bool operator!=(absl::string_view lhs,
+                       const RefCountedStringValue& rhs) {
+  return lhs != rhs.as_string_view();
+}
+inline bool operator!=(const RefCountedStringValue& lhs,
+                       const RefCountedStringValue& rhs) {
+  return lhs.as_string_view() != rhs.as_string_view();
+}
+
 inline bool operator<(const RefCountedStringValue& lhs, absl::string_view rhs) {
   return lhs.as_string_view() < rhs;
 }
diff --git a/src/core/lib/load_balancing/lb_policy.h b/src/core/lib/load_balancing/lb_policy.h
index 2422339274e..a36280c163b 100644
--- a/src/core/lib/load_balancing/lb_policy.h
+++ b/src/core/lib/load_balancing/lb_policy.h
@@ -346,7 +346,7 @@ class LoadBalancingPolicy : public InternallyRefCounted<LoadBalancingPolicy> {
   struct UpdateArgs {
     /// A list of endpoints, each with one or more address, or an error
     /// indicating a failure to obtain the list of addresses.
-    absl::StatusOr<EndpointAddressesList> addresses;
+    absl::StatusOr<std::shared_ptr<EndpointAddressesIterator>> addresses;
     /// The LB policy config.
     RefCountedPtr<Config> config;
     /// A human-readable note providing context about the name resolution that
diff --git a/src/core/lib/promise/activity.cc b/src/core/lib/promise/activity.cc
index 7beaeb1c704..60024b536cb 100644
--- a/src/core/lib/promise/activity.cc
+++ b/src/core/lib/promise/activity.cc
@@ -25,7 +25,6 @@
 #include "absl/strings/str_join.h"
 
 #include "src/core/lib/gprpp/atomic_utils.h"
-#include "src/core/lib/gprpp/crash.h"
 
 namespace grpc_core {
 
@@ -84,7 +83,23 @@ class FreestandingActivity::Handle final : public Wakeable {
   }
 
   void WakeupAsync(WakeupMask) override ABSL_LOCKS_EXCLUDED(mu_) {
-    Crash("not implemented");
+    mu_.Lock();
+    // Note that activity refcount can drop to zero, but we could win the lock
+    // against DropActivity, so we need to only increase activities refcount if
+    // it is non-zero.
+    if (activity_ && activity_->RefIfNonzero()) {
+      FreestandingActivity* activity = activity_;
+      mu_.Unlock();
+      // Activity still exists and we have a reference: wake it up, which will
+      // drop the ref.
+      activity->WakeupAsync(0);
+    } else {
+      // Could not get the activity - it's either gone or going. No need to wake
+      // it up!
+      mu_.Unlock();
+    }
+    // Drop the ref to the handle (we have one ref = one wakeup semantics).
+    Unref();
   }
 
   void Drop(WakeupMask) override { Unref(); }
diff --git a/src/core/lib/promise/activity.h b/src/core/lib/promise/activity.h
index 4325207d93d..a05ddab8afb 100644
--- a/src/core/lib/promise/activity.h
+++ b/src/core/lib/promise/activity.h
@@ -32,7 +32,6 @@
 #include <grpc/support/log.h>
 
 #include "src/core/lib/gprpp/construct_destruct.h"
-#include "src/core/lib/gprpp/crash.h"
 #include "src/core/lib/gprpp/no_destruct.h"
 #include "src/core/lib/gprpp/orphanable.h"
 #include "src/core/lib/gprpp/sync.h"
@@ -502,7 +501,7 @@ class PromiseActivity final
   // the activity to an external threadpool to run. If the activity is already
   // running on this thread, a note is taken of such and the activity is
   // repolled if it doesn't complete.
-  void Wakeup(WakeupMask) final {
+  void Wakeup(WakeupMask m) final {
     // If there is an active activity, but hey it's us, flag that and we'll loop
     // in RunLoop (that's calling from above here!).
     if (Activity::is_current()) {
@@ -511,6 +510,10 @@ class PromiseActivity final
       WakeupComplete();
       return;
     }
+    WakeupAsync(m);
+  }
+
+  void WakeupAsync(WakeupMask) final {
     if (!wakeup_scheduled_.exchange(true, std::memory_order_acq_rel)) {
       // Can't safely run, so ask to run later.
       this->ScheduleWakeup();
@@ -520,8 +523,6 @@ class PromiseActivity final
     }
   }
 
-  void WakeupAsync(WakeupMask) final { Crash("not implemented"); }
-
   // Drop a wakeup
   void Drop(WakeupMask) final { this->WakeupComplete(); }
 
diff --git a/src/core/lib/promise/inter_activity_latch.h b/src/core/lib/promise/inter_activity_latch.h
new file mode 100644
index 00000000000..8c31c8a1625
--- /dev/null
+++ b/src/core/lib/promise/inter_activity_latch.h
@@ -0,0 +1,98 @@
+// Copyright 2021 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef GRPC_SRC_CORE_LIB_PROMISE_INTER_ACTIVITY_LATCH_H
+#define GRPC_SRC_CORE_LIB_PROMISE_INTER_ACTIVITY_LATCH_H
+
+#include <grpc/support/port_platform.h>
+
+#include <stdint.h>
+
+#include <string>
+
+#include "absl/base/thread_annotations.h"
+#include "absl/strings/str_cat.h"
+
+#include <grpc/support/log.h>
+
+#include "src/core/lib/gprpp/sync.h"
+#include "src/core/lib/promise/activity.h"
+#include "src/core/lib/promise/poll.h"
+#include "src/core/lib/promise/trace.h"
+#include "src/core/lib/promise/wait_set.h"
+
+namespace grpc_core {
+
+// A latch providing true cross activity wakeups
+template <typename T>
+class InterActivityLatch;
+
+template <>
+class InterActivityLatch<void> {
+ public:
+  InterActivityLatch() = default;
+  InterActivityLatch(const InterActivityLatch&) = delete;
+  InterActivityLatch& operator=(const InterActivityLatch&) = delete;
+
+  // Produce a promise to wait for this latch.
+  auto Wait() {
+    return [this]() -> Poll<Empty> {
+      MutexLock lock(&mu_);
+      if (grpc_trace_promise_primitives.enabled()) {
+        gpr_log(GPR_INFO, "%sPollWait %s", DebugTag().c_str(),
+                StateString().c_str());
+      }
+      if (is_set_) {
+        return Empty{};
+      } else {
+        return waiters_.AddPending(Activity::current()->MakeNonOwningWaker());
+      }
+    };
+  }
+
+  // Set the latch.
+  void Set() {
+    MutexLock lock(&mu_);
+    if (grpc_trace_promise_primitives.enabled()) {
+      gpr_log(GPR_INFO, "%sSet %s", DebugTag().c_str(), StateString().c_str());
+    }
+    is_set_ = true;
+    waiters_.WakeupAsync();
+  }
+
+  bool IsSet() const ABSL_LOCKS_EXCLUDED(mu_) {
+    MutexLock lock(&mu_);
+    return is_set_;
+  }
+
+ private:
+  std::string DebugTag() {
+    return absl::StrCat(Activity::current()->DebugTag(),
+                        " INTER_ACTIVITY_LATCH[0x",
+                        reinterpret_cast<uintptr_t>(this), "]: ");
+  }
+
+  std::string StateString() ABSL_EXCLUSIVE_LOCKS_REQUIRED(mu_) {
+    return absl::StrCat("is_set:", is_set_);
+  }
+
+  mutable Mutex mu_;
+  // True if we have a value set, false otherwise.
+  bool is_set_ = false;
+  WaitSet waiters_ ABSL_GUARDED_BY(mu_);
+};
+
+}  // namespace grpc_core
+
+#endif  // GRPC_SRC_CORE_LIB_PROMISE_INTER_ACTIVITY_LATCH_H
diff --git a/src/core/lib/promise/latch.h b/src/core/lib/promise/latch.h
index a8f911809f5..4ade84b8939 100644
--- a/src/core/lib/promise/latch.h
+++ b/src/core/lib/promise/latch.h
@@ -37,6 +37,7 @@ namespace grpc_core {
 // Initially the Latch is unset.
 // It can be waited upon by the Wait method, which produces a Promise that
 // resolves when the Latch is Set to a value of type T.
+// Latches only work correctly within a single activity.
 template <typename T>
 class Latch {
  public:
@@ -204,6 +205,9 @@ class Latch<void> {
   IntraActivityWaiter waiter_;
 };
 
+template <typename T>
+using LatchWaitPromise = decltype(std::declval<Latch<T>>().Wait());
+
 // A Latch that can have its value observed by outside threads, but only waited
 // upon from inside a single activity.
 template <typename T>
@@ -268,9 +272,6 @@ class ExternallyObservableLatch<void> {
   IntraActivityWaiter waiter_;
 };
 
-template <typename T>
-using LatchWaitPromise = decltype(std::declval<Latch<T>>().Wait());
-
 }  // namespace grpc_core
 
 #endif  // GRPC_SRC_CORE_LIB_PROMISE_LATCH_H
diff --git a/src/core/lib/promise/party.cc b/src/core/lib/promise/party.cc
index 040afbfe9a3..275d06445a4 100644
--- a/src/core/lib/promise/party.cc
+++ b/src/core/lib/promise/party.cc
@@ -247,7 +247,7 @@ bool Party::RunParty() {
     }
     // Poll the participant.
     currently_polling_ = i;
-    bool done = participant->Poll();
+    bool done = participant->PollParticipantPromise();
     currently_polling_ = kNotPolling;
     if (done) {
       if (!name.empty()) {
diff --git a/src/core/lib/promise/party.h b/src/core/lib/promise/party.h
index 493a00925d1..1ff098f3aa3 100644
--- a/src/core/lib/promise/party.h
+++ b/src/core/lib/promise/party.h
@@ -24,6 +24,7 @@
 #include <string>
 #include <utility>
 
+#include "absl/base/attributes.h"
 #include "absl/base/thread_annotations.h"
 #include "absl/strings/string_view.h"
 
@@ -38,6 +39,7 @@
 #include "src/core/lib/promise/activity.h"
 #include "src/core/lib/promise/context.h"
 #include "src/core/lib/promise/detail/promise_factory.h"
+#include "src/core/lib/promise/poll.h"
 #include "src/core/lib/promise/trace.h"
 #include "src/core/lib/resource_quota/arena.h"
 
@@ -298,7 +300,7 @@ class Party : public Activity, private Wakeable {
     explicit Participant(absl::string_view name) : name_(name) {}
     // Poll the participant. Return true if complete.
     // Participant should take care of its own deallocation in this case.
-    virtual bool Poll() = 0;
+    virtual bool PollParticipantPromise() = 0;
 
     // Destroy the participant before finishing.
     virtual void Destroy() = 0;
@@ -330,6 +332,9 @@ class Party : public Activity, private Wakeable {
   void Spawn(absl::string_view name, Factory promise_factory,
              OnComplete on_complete);
 
+  template <typename Factory>
+  auto SpawnWaitable(absl::string_view name, Factory factory);
+
   void Orphan() final { Crash("unused"); }
 
   // Activity implementation: not allowed to be overridden by derived types.
@@ -414,7 +419,7 @@ class Party : public Activity, private Wakeable {
       }
     }
 
-    bool Poll() override {
+    bool PollParticipantPromise() override {
       if (!started_) {
         auto p = factory_.Make();
         Destruct(&factory_);
@@ -441,6 +446,89 @@ class Party : public Activity, private Wakeable {
     bool started_ = false;
   };
 
+  template <typename SuppliedFactory>
+  class PromiseParticipantImpl final
+      : public RefCounted<PromiseParticipantImpl<SuppliedFactory>,
+                          NonPolymorphicRefCount>,
+        public Participant {
+    using Factory = promise_detail::OncePromiseFactory<void, SuppliedFactory>;
+    using Promise = typename Factory::Promise;
+    using Result = typename Promise::Result;
+
+   public:
+    PromiseParticipantImpl(absl::string_view name,
+                           SuppliedFactory promise_factory)
+        : Participant(name) {
+      Construct(&factory_, std::move(promise_factory));
+    }
+
+    ~PromiseParticipantImpl() {
+      switch (state_.load(std::memory_order_acquire)) {
+        case State::kFactory:
+          Destruct(&factory_);
+          break;
+        case State::kPromise:
+          Destruct(&promise_);
+          break;
+        case State::kResult:
+          Destruct(&result_);
+          break;
+      }
+    }
+
+    // Inside party poll: drive from factory -> promise -> result
+    bool PollParticipantPromise() override {
+      switch (state_.load(std::memory_order_relaxed)) {
+        case State::kFactory: {
+          auto p = factory_.Make();
+          Destruct(&factory_);
+          Construct(&promise_, std::move(p));
+          state_.store(State::kPromise, std::memory_order_relaxed);
+        }
+          ABSL_FALLTHROUGH_INTENDED;
+        case State::kPromise: {
+          auto p = promise_();
+          if (auto* r = p.value_if_ready()) {
+            Destruct(&promise_);
+            Construct(&result_, std::move(*r));
+            state_.store(State::kResult, std::memory_order_release);
+            waiter_.Wakeup();
+            this->Unref();
+            return true;
+          }
+          return false;
+        }
+        case State::kResult:
+          Crash(
+              "unreachable: promises should not be repolled after completion");
+      }
+    }
+
+    // Outside party poll: check whether the spawning party has completed this
+    // promise.
+    Poll<Result> PollCompletion() {
+      switch (state_.load(std::memory_order_acquire)) {
+        case State::kFactory:
+        case State::kPromise:
+          return Pending{};
+        case State::kResult:
+          return std::move(result_);
+      }
+    }
+
+    void Destroy() override { this->Unref(); }
+
+   private:
+    enum class State : uint8_t { kFactory, kPromise, kResult };
+    union {
+      GPR_NO_UNIQUE_ADDRESS Factory factory_;
+      GPR_NO_UNIQUE_ADDRESS Promise promise_;
+      GPR_NO_UNIQUE_ADDRESS Result result_;
+    };
+    Waker waiter_{Activity::current()->MakeOwningWaker()};
+    std::atomic<State> state_{State::kFactory};
+  };
+
   // Notification that the party has finished and this instance can be deleted.
   // Derived types should arrange to call CancelRemainingParticipants during
   // this sequence.
@@ -502,6 +590,17 @@ void Party::Spawn(absl::string_view name, Factory promise_factory,
                           std::move(on_complete));
 }
 
+template <typename Factory>
+auto Party::SpawnWaitable(absl::string_view name, Factory promise_factory) {
+  auto participant = MakeRefCounted<PromiseParticipantImpl<Factory>>(
+      name, std::move(promise_factory));
+  Participant* p = participant->Ref().release();
+  AddParticipants(&p, 1);
+  return [participant = std::move(participant)]() mutable {
+    return participant->PollCompletion();
+  };
+}
+
 }  // namespace grpc_core
 
 #endif  // GRPC_SRC_CORE_LIB_PROMISE_PARTY_H
diff --git a/src/core/lib/promise/wait_set.h b/src/core/lib/promise/wait_set.h
index 2f978e5750a..bf1adc6c1c2 100644
--- a/src/core/lib/promise/wait_set.h
+++ b/src/core/lib/promise/wait_set.h
@@ -69,6 +69,12 @@ class WaitSet final {
     return ret;
   }
 
+  void WakeupAsync() {
+    while (!pending_.empty()) {
+      pending_.extract(pending_.begin()).value().WakeupAsync();
+    }
+  }
+
  private:
   // Handles to activities that need to be awoken.
   WakerSet pending_;
diff --git a/src/core/lib/resolver/endpoint_addresses.cc b/src/core/lib/resolver/endpoint_addresses.cc
index 7995163ad5d..7b5f4c0a329 100644
--- a/src/core/lib/resolver/endpoint_addresses.cc
+++ b/src/core/lib/resolver/endpoint_addresses.cc
@@ -22,7 +22,6 @@
 
 #include <string.h>
 
-#include <algorithm>
 #include <string>
 #include <utility>
 #include <vector>
diff --git a/src/core/lib/resolver/endpoint_addresses.h b/src/core/lib/resolver/endpoint_addresses.h
index 9d0d7c6edb8..5746df19c5b 100644
--- a/src/core/lib/resolver/endpoint_addresses.h
+++ b/src/core/lib/resolver/endpoint_addresses.h
@@ -23,8 +23,11 @@
 
 #include <set>
 #include <string>
+#include <utility>
 #include <vector>
 
+#include "absl/functional/function_ref.h"
+
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/iomgr/resolved_address.h"
 
@@ -64,6 +67,9 @@ class EndpointAddresses {
   bool operator==(const EndpointAddresses& other) const {
     return Cmp(other) == 0;
   }
+  bool operator!=(const EndpointAddresses& other) const {
+    return Cmp(other) != 0;
+  }
   bool operator<(const EndpointAddresses& other) const {
     return Cmp(other) < 0;
   }
@@ -111,6 +117,48 @@ class EndpointAddressSet {
   std::set<grpc_resolved_address, ResolvedAddressLessThan> addresses_;
 };
 
+// An iterator interface for endpoints.
+class EndpointAddressesIterator {
+ public:
+  virtual ~EndpointAddressesIterator() = default;
+
+  // Invokes callback once for each endpoint.
+  virtual void ForEach(
+      absl::FunctionRef<void(const EndpointAddresses&)> callback) const = 0;
+};
+
+// Iterator over a fixed list of endpoints.
+class EndpointAddressesListIterator : public EndpointAddressesIterator {
+ public:
+  explicit EndpointAddressesListIterator(EndpointAddressesList endpoints)
+      : endpoints_(std::move(endpoints)) {}
+
+  void ForEach(absl::FunctionRef<void(const EndpointAddresses&)> callback)
+      const override {
+    for (const auto& endpoint : endpoints_) {
+      callback(endpoint);
+    }
+  }
+
+ private:
+  EndpointAddressesList endpoints_;
+};
+
+// Iterator that returns only a single endpoint.
+class SingleEndpointIterator : public EndpointAddressesIterator {
+ public:
+  explicit SingleEndpointIterator(EndpointAddresses endpoint)
+      : endpoint_(std::move(endpoint)) {}
+
+  void ForEach(absl::FunctionRef<void(const EndpointAddresses&)> callback)
+      const override {
+    callback(endpoint_);
+  }
+
+ private:
+  EndpointAddresses endpoint_;
+};
+
 }  // namespace grpc_core
 
 #endif  // GRPC_SRC_CORE_LIB_RESOLVER_ENDPOINT_ADDRESSES_H
diff --git a/src/core/lib/surface/version.cc b/src/core/lib/surface/version.cc
index e3000e5d51f..8e4af533e16 100644
--- a/src/core/lib/surface/version.cc
+++ b/src/core/lib/surface/version.cc
@@ -23,6 +23,6 @@
 
 #include <grpc/grpc.h>
 
-const char* grpc_version_string(void) { return "36.0.0"; }
+const char* grpc_version_string(void) { return "37.0.0"; }
 
-const char* grpc_g_stands_for(void) { return "gjallarhorn"; }
+const char* grpc_g_stands_for(void) { return "grand"; }
diff --git a/src/csharp/build/dependencies.props b/src/csharp/build/dependencies.props
index b52c6a8a44a..11a1cfa9faf 100644
--- a/src/csharp/build/dependencies.props
+++ b/src/csharp/build/dependencies.props
@@ -1,7 +1,7 @@
 <!-- This file is generated -->
 <Project>
   <PropertyGroup>
-    <GrpcCsharpVersion>2.60.0-dev</GrpcCsharpVersion>
+    <GrpcCsharpVersion>2.61.0-dev</GrpcCsharpVersion>
     <GoogleProtobufVersion>3.25.0</GoogleProtobufVersion>
   </PropertyGroup>
 </Project>
diff --git a/src/objective-c/!ProtoCompiler-gRPCCppPlugin.podspec b/src/objective-c/!ProtoCompiler-gRPCCppPlugin.podspec
index 8dc3d59a0aa..2a0a4515b76 100644
--- a/src/objective-c/!ProtoCompiler-gRPCCppPlugin.podspec
+++ b/src/objective-c/!ProtoCompiler-gRPCCppPlugin.podspec
@@ -42,7 +42,7 @@ Pod::Spec.new do |s|
   # exclamation mark ensures that other "regular" pods will be able to find it as it'll be installed
   # before them.
   s.name     = '!ProtoCompiler-gRPCCppPlugin'
-  v = '1.60.0-dev'
+  v = '1.61.0-dev'
   s.version  = v
   s.summary  = 'The gRPC ProtoC plugin generates C++ files from .proto services.'
   s.description = <<-DESC
diff --git a/src/objective-c/!ProtoCompiler-gRPCPlugin.podspec b/src/objective-c/!ProtoCompiler-gRPCPlugin.podspec
index 5fcd86421a4..684d14ea056 100644
--- a/src/objective-c/!ProtoCompiler-gRPCPlugin.podspec
+++ b/src/objective-c/!ProtoCompiler-gRPCPlugin.podspec
@@ -42,7 +42,7 @@ Pod::Spec.new do |s|
   # exclamation mark ensures that other "regular" pods will be able to find it as it'll be installed
   # before them.
   s.name     = '!ProtoCompiler-gRPCPlugin'
-  v = '1.60.0-dev'
+  v = '1.61.0-dev'
   s.version  = v
   s.summary  = 'The gRPC ProtoC plugin generates Objective-C files from .proto services.'
   s.description = <<-DESC
diff --git a/src/objective-c/GRPCClient/version.h b/src/objective-c/GRPCClient/version.h
index 82f8c5ae08a..0d9beef527e 100644
--- a/src/objective-c/GRPCClient/version.h
+++ b/src/objective-c/GRPCClient/version.h
@@ -22,4 +22,4 @@
 // instead. This file can be regenerated from the template by running
 // `tools/buildgen/generate_projects.sh`.
 
-#define GRPC_OBJC_VERSION_STRING @"1.60.0-dev"
+#define GRPC_OBJC_VERSION_STRING @"1.61.0-dev"
diff --git a/src/objective-c/RxLibrary/GRXConcurrentWriteable.m b/src/objective-c/RxLibrary/GRXConcurrentWriteable.m
index 115195463de..9686c7567a7 100644
--- a/src/objective-c/RxLibrary/GRXConcurrentWriteable.m
+++ b/src/objective-c/RxLibrary/GRXConcurrentWriteable.m
@@ -18,7 +18,7 @@
 
 #import "GRXConcurrentWriteable.h"
 
-#import <RxLibrary/GRXWriteable.h>
+#import "GRXWriteable.h"
 
 @interface GRXConcurrentWriteable ()
 // This is atomic so that cancellation can nillify it from any thread.
diff --git a/src/objective-c/RxLibrary/GRXMappingWriter.h b/src/objective-c/RxLibrary/GRXMappingWriter.h
index a344f966228..90a6e29ef21 100644
--- a/src/objective-c/RxLibrary/GRXMappingWriter.h
+++ b/src/objective-c/RxLibrary/GRXMappingWriter.h
@@ -16,7 +16,7 @@
  *
  */
 
-#import "RxLibrary/GRXForwardingWriter.h"
+#import "GRXForwardingWriter.h"
 
 /** A "proxy" writer that transforms all the values of its input writer by using a mapping function.
  */
diff --git a/src/objective-c/tests/Common/GRPCBlockCallbackResponseHandler.m b/src/objective-c/tests/Common/GRPCBlockCallbackResponseHandler.m
index c797b0e91bc..39ceabad907 100644
--- a/src/objective-c/tests/Common/GRPCBlockCallbackResponseHandler.m
+++ b/src/objective-c/tests/Common/GRPCBlockCallbackResponseHandler.m
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#import "GRPCBlockCallbackResponseHandler.h"
+#import <GRPCClient/GRPCBlockCallbackResponseHandler.h>
 
 @implementation GRPCBlockCallbackResponseHandler {
   void (^_initialMetadataCallback)(NSDictionary *);
diff --git a/src/objective-c/tests/version.h b/src/objective-c/tests/version.h
index 796b5cee691..f9576295fb4 100644
--- a/src/objective-c/tests/version.h
+++ b/src/objective-c/tests/version.h
@@ -22,5 +22,5 @@
 // instead. This file can be regenerated from the template by running
 // `tools/buildgen/generate_projects.sh`.
 
-#define GRPC_OBJC_VERSION_STRING @"1.60.0-dev"
-#define GRPC_C_VERSION_STRING @"36.0.0"
+#define GRPC_OBJC_VERSION_STRING @"1.61.0-dev"
+#define GRPC_C_VERSION_STRING @"37.0.0"
diff --git a/src/php/composer.json b/src/php/composer.json
index 774bacbd822..3759c51b3cd 100644
--- a/src/php/composer.json
+++ b/src/php/composer.json
@@ -2,7 +2,7 @@
   "name": "grpc/grpc-dev",
   "description": "gRPC library for PHP - for Development use only",
   "license": "Apache-2.0",
-  "version": "1.60.0",
+  "version": "1.61.0",
   "require": {
     "php": ">=7.0.0",
     "google/protobuf": "^v3.3.0"
diff --git a/src/php/ext/grpc/version.h b/src/php/ext/grpc/version.h
index a5f408a4fdd..c153307a14c 100644
--- a/src/php/ext/grpc/version.h
+++ b/src/php/ext/grpc/version.h
@@ -20,6 +20,6 @@
 #ifndef VERSION_H
 #define VERSION_H
 
-#define PHP_GRPC_VERSION "1.60.0dev"
+#define PHP_GRPC_VERSION "1.61.0dev"
 
 #endif /* VERSION_H */
diff --git a/src/proto/grpc/testing/BUILD b/src/proto/grpc/testing/BUILD
index 0f7bbbecf63..41ab62e76e2 100644
--- a/src/proto/grpc/testing/BUILD
+++ b/src/proto/grpc/testing/BUILD
@@ -12,9 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+load("//bazel:python_rules.bzl", "py_grpc_library", "py_proto_library")
 load("@rules_proto//proto:defs.bzl", "proto_library")
 load("//bazel:grpc_build_system.bzl", "grpc_package", "grpc_proto_library")
-load("//bazel:python_rules.bzl", "py_grpc_library", "py_proto_library")
 
 licenses(["notice"])
 
diff --git a/src/proto/grpc/testing/xds/v3/BUILD b/src/proto/grpc/testing/xds/v3/BUILD
index 9c02b2a9f6c..f72941136cc 100644
--- a/src/proto/grpc/testing/xds/v3/BUILD
+++ b/src/proto/grpc/testing/xds/v3/BUILD
@@ -12,8 +12,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-load("//bazel:grpc_build_system.bzl", "grpc_package", "grpc_proto_library")
 load("//bazel:python_rules.bzl", "py_grpc_library", "py_proto_library")
+load("//bazel:grpc_build_system.bzl", "grpc_package", "grpc_proto_library")
 
 licenses(["notice"])
 
diff --git a/src/python/grpcio/grpc/_grpcio_metadata.py b/src/python/grpcio/grpc/_grpcio_metadata.py
index 246281c9f8f..0878cfbe7b7 100644
--- a/src/python/grpcio/grpc/_grpcio_metadata.py
+++ b/src/python/grpcio/grpc/_grpcio_metadata.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio/grpc/_grpcio_metadata.py.template`!!!
 
-__version__ = """1.60.0.dev0"""
+__version__ = """1.61.0.dev0"""
diff --git a/src/python/grpcio/grpc_version.py b/src/python/grpcio/grpc_version.py
index 3bd28105138..a82549b1dd6 100644
--- a/src/python/grpcio/grpc_version.py
+++ b/src/python/grpcio/grpc_version.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio/grpc_version.py.template`!!!
 
-VERSION = '1.60.0.dev0'
+VERSION = '1.61.0.dev0'
diff --git a/src/python/grpcio_admin/grpc_version.py b/src/python/grpcio_admin/grpc_version.py
index 34ff73ffc2e..953344d81c0 100644
--- a/src/python/grpcio_admin/grpc_version.py
+++ b/src/python/grpcio_admin/grpc_version.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio_admin/grpc_version.py.template`!!!
 
-VERSION = '1.60.0.dev0'
+VERSION = '1.61.0.dev0'
diff --git a/src/python/grpcio_channelz/grpc_version.py b/src/python/grpcio_channelz/grpc_version.py
index 460e8b3ec68..1cac50e1c9c 100644
--- a/src/python/grpcio_channelz/grpc_version.py
+++ b/src/python/grpcio_channelz/grpc_version.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio_channelz/grpc_version.py.template`!!!
 
-VERSION = '1.60.0.dev0'
+VERSION = '1.61.0.dev0'
diff --git a/src/python/grpcio_csds/grpc_version.py b/src/python/grpcio_csds/grpc_version.py
index e9eb1c4b04e..d3033c7128d 100644
--- a/src/python/grpcio_csds/grpc_version.py
+++ b/src/python/grpcio_csds/grpc_version.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio_csds/grpc_version.py.template`!!!
 
-VERSION = '1.60.0.dev0'
+VERSION = '1.61.0.dev0'
diff --git a/src/python/grpcio_health_checking/grpc_version.py b/src/python/grpcio_health_checking/grpc_version.py
index 5f113326532..aaf86b43c40 100644
--- a/src/python/grpcio_health_checking/grpc_version.py
+++ b/src/python/grpcio_health_checking/grpc_version.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio_health_checking/grpc_version.py.template`!!!
 
-VERSION = '1.60.0.dev0'
+VERSION = '1.61.0.dev0'
diff --git a/src/python/grpcio_reflection/grpc_version.py b/src/python/grpcio_reflection/grpc_version.py
index 28ad64a08c1..bb056c9abe9 100644
--- a/src/python/grpcio_reflection/grpc_version.py
+++ b/src/python/grpcio_reflection/grpc_version.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio_reflection/grpc_version.py.template`!!!
 
-VERSION = '1.60.0.dev0'
+VERSION = '1.61.0.dev0'
diff --git a/src/python/grpcio_status/grpc_version.py b/src/python/grpcio_status/grpc_version.py
index 741a4e2ca18..0f107a38e4c 100644
--- a/src/python/grpcio_status/grpc_version.py
+++ b/src/python/grpcio_status/grpc_version.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio_status/grpc_version.py.template`!!!
 
-VERSION = '1.60.0.dev0'
+VERSION = '1.61.0.dev0'
diff --git a/src/python/grpcio_testing/grpc_version.py b/src/python/grpcio_testing/grpc_version.py
index c9ddf97b431..46e15d74475 100644
--- a/src/python/grpcio_testing/grpc_version.py
+++ b/src/python/grpcio_testing/grpc_version.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio_testing/grpc_version.py.template`!!!
 
-VERSION = '1.60.0.dev0'
+VERSION = '1.61.0.dev0'
diff --git a/src/python/grpcio_tests/grpc_version.py b/src/python/grpcio_tests/grpc_version.py
index 8e56fb6983d..3badf3ad39a 100644
--- a/src/python/grpcio_tests/grpc_version.py
+++ b/src/python/grpcio_tests/grpc_version.py
@@ -14,4 +14,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio_tests/grpc_version.py.template`!!!
 
-VERSION = '1.60.0.dev0'
+VERSION = '1.61.0.dev0'
diff --git a/src/ruby/lib/grpc/version.rb b/src/ruby/lib/grpc/version.rb
index 58b49ea1367..1468a96a3bd 100644
--- a/src/ruby/lib/grpc/version.rb
+++ b/src/ruby/lib/grpc/version.rb
@@ -14,5 +14,5 @@
 
 # GRPC contains the General RPC module.
 module GRPC
-  VERSION = '1.60.0.dev'
+  VERSION = '1.61.0.dev'
 end
diff --git a/src/ruby/nativedebug/version.rb b/src/ruby/nativedebug/version.rb
index 2cdfd263fe2..6a5c24b0784 100644
--- a/src/ruby/nativedebug/version.rb
+++ b/src/ruby/nativedebug/version.rb
@@ -14,6 +14,6 @@
 
 module GRPC
   module NativeDebug
-    VERSION = '1.60.0.dev'
+    VERSION = '1.61.0.dev'
   end
 end
diff --git a/src/ruby/tools/version.rb b/src/ruby/tools/version.rb
index 619ce83d7a5..d14e6df41cf 100644
--- a/src/ruby/tools/version.rb
+++ b/src/ruby/tools/version.rb
@@ -14,6 +14,6 @@
 
 module GRPC
   module Tools
-    VERSION = '1.60.0.dev'
+    VERSION = '1.61.0.dev'
   end
 end
diff --git a/test/core/client_channel/lb_policy/lb_policy_test_lib.h b/test/core/client_channel/lb_policy/lb_policy_test_lib.h
index 81365410c48..27d7f38285b 100644
--- a/test/core/client_channel/lb_policy/lb_policy_test_lib.h
+++ b/test/core/client_channel/lb_policy/lb_policy_test_lib.h
@@ -773,7 +773,8 @@ class LoadBalancingPolicyTest : public ::testing::Test {
       absl::Span<const EndpointAddresses> endpoints,
       RefCountedPtr<LoadBalancingPolicy::Config> config) {
     LoadBalancingPolicy::UpdateArgs update;
-    update.addresses.emplace(endpoints.begin(), endpoints.end());
+    update.addresses = std::make_shared<EndpointAddressesListIterator>(
+        EndpointAddressesList(endpoints.begin(), endpoints.end()));
     update.config = std::move(config);
     return update;
   }
diff --git a/test/core/client_channel/lb_policy/xds_override_host_test.cc b/test/core/client_channel/lb_policy/xds_override_host_test.cc
index f3bf82fc6be..7e9d45d7f63 100644
--- a/test/core/client_channel/lb_policy/xds_override_host_test.cc
+++ b/test/core/client_channel/lb_policy/xds_override_host_test.cc
@@ -99,11 +99,13 @@ class XdsOverrideHostTest : public LoadBalancingPolicyTest {
                                                                   "HEALTHY"}) {
     LoadBalancingPolicy::UpdateArgs update;
     update.config = MakeXdsOverrideHostConfig(override_host_status);
-    update.addresses.emplace();
+    EndpointAddressesList endpoints;
     for (auto address_and_status : addresses_and_statuses) {
-      update.addresses->push_back(MakeAddressWithHealthStatus(
+      endpoints.push_back(MakeAddressWithHealthStatus(
           address_and_status.first, address_and_status.second));
     }
+    update.addresses =
+        std::make_shared<EndpointAddressesListIterator>(std::move(endpoints));
     EXPECT_EQ(ApplyUpdate(update, lb_policy()), absl::OkStatus());
   }
 
diff --git a/test/core/promise/BUILD b/test/core/promise/BUILD
index 5073d060b01..2370dfdc4a7 100644
--- a/test/core/promise/BUILD
+++ b/test/core/promise/BUILD
@@ -419,6 +419,27 @@ grpc_cc_test(
     ],
 )
 
+grpc_cc_test(
+    name = "inter_activity_latch_test",
+    srcs = ["inter_activity_latch_test.cc"],
+    external_deps = [
+        "absl/status",
+        "gtest",
+    ],
+    language = "c++",
+    tags = ["promise_test"],
+    uses_event_engine = False,
+    uses_polling = False,
+    deps = [
+        "//:grpc",
+        "//src/core:default_event_engine",
+        "//src/core:event_engine_wakeup_scheduler",
+        "//src/core:inter_activity_latch",
+        "//src/core:notification",
+        "//src/core:seq",
+    ],
+)
+
 grpc_cc_test(
     name = "mpsc_test",
     srcs = ["mpsc_test.cc"],
@@ -591,6 +612,7 @@ grpc_cc_test(
         "//src/core:context",
         "//src/core:default_event_engine",
         "//src/core:event_engine_memory_allocator",
+        "//src/core:inter_activity_latch",
         "//src/core:memory_quota",
         "//src/core:notification",
         "//src/core:poll",
diff --git a/test/core/promise/inter_activity_latch_test.cc b/test/core/promise/inter_activity_latch_test.cc
new file mode 100644
index 00000000000..087489b240e
--- /dev/null
+++ b/test/core/promise/inter_activity_latch_test.cc
@@ -0,0 +1,103 @@
+// Copyright 2023 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "src/core/lib/promise/inter_activity_latch.h"
+
+#include "absl/status/status.h"
+#include "gtest/gtest.h"
+
+#include <grpc/grpc.h>
+
+#include "src/core/lib/event_engine/default_event_engine.h"
+#include "src/core/lib/gprpp/notification.h"
+#include "src/core/lib/promise/event_engine_wakeup_scheduler.h"
+#include "src/core/lib/promise/seq.h"
+
+using grpc_event_engine::experimental::GetDefaultEventEngine;
+
+namespace grpc_core {
+namespace {
+
+TEST(InterActivityLatchTest, Works) {
+  InterActivityLatch<void> latch;
+
+  // Start some waiting activities
+  Notification n1;
+  auto a1 = MakeActivity(
+      [&] {
+        return Seq(latch.Wait(), [&](Empty) {
+          n1.Notify();
+          return absl::OkStatus();
+        });
+      },
+      EventEngineWakeupScheduler{GetDefaultEventEngine()}, [](absl::Status) {});
+  Notification n2;
+  auto a2 = MakeActivity(
+      [&] {
+        return Seq(latch.Wait(), [&](Empty) {
+          n2.Notify();
+          return absl::OkStatus();
+        });
+      },
+      EventEngineWakeupScheduler{GetDefaultEventEngine()}, [](absl::Status) {});
+  Notification n3;
+  auto a3 = MakeActivity(
+      [&] {
+        return Seq(latch.Wait(), [&](Empty) {
+          n3.Notify();
+          return absl::OkStatus();
+        });
+      },
+      EventEngineWakeupScheduler{GetDefaultEventEngine()}, [](absl::Status) {});
+
+  ASSERT_FALSE(n1.HasBeenNotified());
+  ASSERT_FALSE(n2.HasBeenNotified());
+  ASSERT_FALSE(n3.HasBeenNotified());
+
+  // Start a setting activity
+  auto kicker = MakeActivity(
+      [&] {
+        latch.Set();
+        return absl::OkStatus();
+      },
+      EventEngineWakeupScheduler{GetDefaultEventEngine()}, [](absl::Status) {});
+
+  // Start another waiting activity
+  Notification n4;
+  auto a4 = MakeActivity(
+      [&] {
+        return Seq(latch.Wait(), [&](Empty) {
+          n4.Notify();
+          return absl::OkStatus();
+        });
+      },
+      EventEngineWakeupScheduler{GetDefaultEventEngine()}, [](absl::Status) {});
+
+  // Everything should finish
+  n1.WaitForNotification();
+  n2.WaitForNotification();
+  n3.WaitForNotification();
+  n4.WaitForNotification();
+}
+
+}  // namespace
+}  // namespace grpc_core
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  grpc_init();  // for GetDefaultEventEngine
+  int r = RUN_ALL_TESTS();
+  grpc_shutdown();
+  return r;
+}
diff --git a/test/core/promise/party_test.cc b/test/core/promise/party_test.cc
index a15b10a985b..551443ac4d5 100644
--- a/test/core/promise/party_test.cc
+++ b/test/core/promise/party_test.cc
@@ -36,6 +36,7 @@
 #include "src/core/lib/gprpp/time.h"
 #include "src/core/lib/iomgr/exec_ctx.h"
 #include "src/core/lib/promise/context.h"
+#include "src/core/lib/promise/inter_activity_latch.h"
 #include "src/core/lib/promise/poll.h"
 #include "src/core/lib/promise/seq.h"
 #include "src/core/lib/promise/sleep.h"
@@ -298,6 +299,31 @@ TEST_F(PartyTest, CanSpawnAndRun) {
   n.WaitForNotification();
 }
 
+TEST_F(PartyTest, CanSpawnWaitableAndRun) {
+  auto party1 = MakeRefCounted<TestParty>();
+  auto party2 = MakeRefCounted<TestParty>();
+  Notification n;
+  InterActivityLatch<void> done;
+  // Spawn a task on party1 that will wait for a task on party2.
+  // The party2 task will wait on the latch `done`.
+  party1->Spawn(
+      "party1_main",
+      [&party2, &done]() {
+        return party2->SpawnWaitable("party2_main",
+                                     [&done]() { return done.Wait(); });
+      },
+      [&n](Empty) { n.Notify(); });
+  ASSERT_FALSE(n.HasBeenNotified());
+  party1->Spawn(
+      "party1_notify_latch",
+      [&done]() {
+        done.Set();
+        return Empty{};
+      },
+      [](Empty) {});
+  n.WaitForNotification();
+}
+
 TEST_F(PartyTest, CanSpawnFromSpawn) {
   auto party = MakeRefCounted<TestParty>();
   Notification n1;
diff --git a/test/core/util/test_lb_policies.cc b/test/core/util/test_lb_policies.cc
index 8fb255d65ed..f7e5abe6e2c 100644
--- a/test/core/util/test_lb_policies.cc
+++ b/test/core/util/test_lb_policies.cc
@@ -414,17 +414,19 @@ class FixedAddressLoadBalancingPolicy : public ForwardingLoadBalancingPolicy {
             config->address().c_str());
     auto uri = URI::Parse(config->address());
     args.config.reset();
-    args.addresses = EndpointAddressesList();
+    EndpointAddressesList addresses;
     if (uri.ok()) {
       grpc_resolved_address address;
       GPR_ASSERT(grpc_parse_uri(*uri, &address));
-      args.addresses->emplace_back(address, ChannelArgs());
+      addresses.emplace_back(address, ChannelArgs());
     } else {
       gpr_log(GPR_ERROR,
               "%s: could not parse URI (%s), using empty address list",
               kFixedAddressLbPolicyName, uri.status().ToString().c_str());
       args.resolution_note = "no address in fixed_address_lb policy";
     }
+    args.addresses =
+        std::make_shared<EndpointAddressesListIterator>(std::move(addresses));
     return ForwardingLoadBalancingPolicy::UpdateLocked(std::move(args));
   }
 
diff --git a/test/cpp/end2end/xds/xds_end2end_test.cc b/test/cpp/end2end/xds/xds_end2end_test.cc
index f4e6e1cdbf8..b66416061d7 100644
--- a/test/cpp/end2end/xds/xds_end2end_test.cc
+++ b/test/cpp/end2end/xds/xds_end2end_test.cc
@@ -13,13 +13,10 @@
 // limitations under the License.
 //
 
-// TODO(roth): Split this file up into a common test framework and a set
-// of test files that use that framework.  Need to figure out the best
-// way to split up the tests.  One option would be to split it up by xDS
-// resource type; another approach would be to have all of the "core"
-// xDS functionality in one file and then move specific features to
-// their own files (e.g., mTLS security, fault injection, circuit
-// breaking, etc).
+// TODO(yashkt): Split this file up into (at least) the following pieces:
+// - xDS-enabled server functionality
+// - mTLS functionality on both client and server
+// - RBAC
 
 #include <deque>
 #include <memory>
@@ -324,34 +321,14 @@ class XdsSecurityTest : public XdsEnd2endTest {
     balancer_->ads_service()->SetEdsResource(BuildEdsResource(args));
   }
 
-  // Sends CDS updates with the new security configuration and verifies that
-  // after propagation, this new configuration is used for connections. If \a
-  // identity_instance_name and \a root_instance_name are both empty,
-  // connections are expected to use fallback credentials.
-  void UpdateAndVerifyXdsSecurityConfiguration(
+  void MaybeSetUpstreamTlsContextOnCluster(
       absl::string_view root_instance_name,
       absl::string_view root_certificate_name,
       absl::string_view identity_instance_name,
       absl::string_view identity_certificate_name,
-      const std::vector<StringMatcher>& san_matchers,
-      const std::vector<std::string>& expected_authenticated_identity,
-      bool test_expects_failure = false) {
-    // Change the backend and use a unique service name to use so that we know
-    // that the CDS update was applied.
-    std::string service_name = absl::StrCat(
-        "eds_service_name",
-        absl::FormatTime("%H%M%E3S", absl::Now(), absl::LocalTimeZone()));
-    backend_index_ = (backend_index_ + 1) % 2;
-    EdsResourceArgs args({
-        {"locality0",
-         CreateEndpointsForBackends(backend_index_, backend_index_ + 1)},
-    });
-    balancer_->ads_service()->SetEdsResource(
-        BuildEdsResource(args, service_name.c_str()));
-    auto cluster = default_cluster_;
-    cluster.mutable_eds_cluster_config()->set_service_name(service_name);
+      const std::vector<StringMatcher>& san_matchers, Cluster* cluster) {
     if (!identity_instance_name.empty() || !root_instance_name.empty()) {
-      auto* transport_socket = cluster.mutable_transport_socket();
+      auto* transport_socket = cluster->mutable_transport_socket();
       transport_socket->set_name("envoy.transport_sockets.tls");
       UpstreamTlsContext upstream_tls_context;
       if (!identity_instance_name.empty()) {
@@ -382,6 +359,37 @@ class XdsSecurityTest : public XdsEnd2endTest {
       }
       transport_socket->mutable_typed_config()->PackFrom(upstream_tls_context);
     }
+  }
+
+  // Sends CDS updates with the new security configuration and verifies that
+  // after propagation, this new configuration is used for connections. If \a
+  // identity_instance_name and \a root_instance_name are both empty,
+  // connections are expected to use fallback credentials.
+  void UpdateAndVerifyXdsSecurityConfiguration(
+      absl::string_view root_instance_name,
+      absl::string_view root_certificate_name,
+      absl::string_view identity_instance_name,
+      absl::string_view identity_certificate_name,
+      const std::vector<StringMatcher>& san_matchers,
+      const std::vector<std::string>& expected_authenticated_identity,
+      bool test_expects_failure = false) {
+    // Change the backend and use a unique service name to use so that we know
+    // that the CDS update was applied.
+    std::string service_name = absl::StrCat(
+        "eds_service_name",
+        absl::FormatTime("%H%M%E3S", absl::Now(), absl::LocalTimeZone()));
+    backend_index_ = (backend_index_ + 1) % 2;
+    EdsResourceArgs args({
+        {"locality0",
+         CreateEndpointsForBackends(backend_index_, backend_index_ + 1)},
+    });
+    balancer_->ads_service()->SetEdsResource(
+        BuildEdsResource(args, service_name.c_str()));
+    auto cluster = default_cluster_;
+    cluster.mutable_eds_cluster_config()->set_service_name(service_name);
+    MaybeSetUpstreamTlsContextOnCluster(
+        root_instance_name, root_certificate_name, identity_instance_name,
+        identity_certificate_name, san_matchers, &cluster);
     balancer_->ads_service()->SetCdsResource(cluster);
     // The updates might take time to have an effect, so use a retry loop.
     if (test_expects_failure) {
@@ -730,6 +738,63 @@ TEST_P(XdsSecurityTest, TestFileWatcherCertificateProvider) {
                                           authenticated_identity_);
 }
 
+TEST_P(XdsSecurityTest, MtlsWithAggregateCluster) {
+  g_fake1_cert_data_map->Set({{"", {root_cert_, identity_pair_}}});
+  g_fake2_cert_data_map->Set({{"", {root_cert_, fallback_identity_pair_}}});
+  // Set up aggregate cluster.
+  const char* kNewCluster1Name = "new_cluster_1";
+  const char* kNewEdsService1Name = "new_eds_service_name_1";
+  const char* kNewCluster2Name = "new_cluster_2";
+  const char* kNewEdsService2Name = "new_eds_service_name_2";
+  // Populate new EDS resources.
+  EdsResourceArgs args1({
+      {"locality0", CreateEndpointsForBackends(0, 1)},
+  });
+  EdsResourceArgs args2({
+      {"locality0", CreateEndpointsForBackends(1, 2)},
+  });
+  balancer_->ads_service()->SetEdsResource(
+      BuildEdsResource(args1, kNewEdsService1Name));
+  balancer_->ads_service()->SetEdsResource(
+      BuildEdsResource(args2, kNewEdsService2Name));
+  // Populate new CDS resources.
+  Cluster new_cluster1 = default_cluster_;
+  new_cluster1.set_name(kNewCluster1Name);
+  new_cluster1.mutable_eds_cluster_config()->set_service_name(
+      kNewEdsService1Name);
+  MaybeSetUpstreamTlsContextOnCluster("fake_plugin1", "", "fake_plugin1", "",
+                                      {}, &new_cluster1);
+  balancer_->ads_service()->SetCdsResource(new_cluster1);
+  Cluster new_cluster2 = default_cluster_;
+  new_cluster2.set_name(kNewCluster2Name);
+  new_cluster2.mutable_eds_cluster_config()->set_service_name(
+      kNewEdsService2Name);
+  MaybeSetUpstreamTlsContextOnCluster("fake_plugin1", "", "fake_plugin2", "",
+                                      {}, &new_cluster2);
+  balancer_->ads_service()->SetCdsResource(new_cluster2);
+  // Create Aggregate Cluster
+  auto cluster = default_cluster_;
+  auto* custom_cluster = cluster.mutable_cluster_type();
+  custom_cluster->set_name("envoy.clusters.aggregate");
+  envoy::extensions::clusters::aggregate::v3::ClusterConfig cluster_config;
+  cluster_config.add_clusters(kNewCluster1Name);
+  cluster_config.add_clusters(kNewCluster2Name);
+  custom_cluster->mutable_typed_config()->PackFrom(cluster_config);
+  balancer_->ads_service()->SetCdsResource(cluster);
+  // RPC should go to backend 0.
+  CheckRpcSendOk(DEBUG_LOCATION);
+  EXPECT_EQ(backends_[0]->backend_service()->request_count(), 1);
+  // Make sure the backend saw the right client identity.
+  EXPECT_EQ(backends_[0]->backend_service()->last_peer_identity(),
+            authenticated_identity_);
+  // Now stop backend 0 and wait for backend 1.
+  ShutdownBackend(0);
+  WaitForBackend(DEBUG_LOCATION, 1);
+  // Make sure the backend saw the right client identity.
+  EXPECT_EQ(backends_[1]->backend_service()->last_peer_identity(),
+            fallback_authenticated_identity_);
+}
+
 class XdsEnabledServerTest : public XdsEnd2endTest {
  protected:
   void SetUp() override {}  // No-op -- individual tests do this themselves.
diff --git a/tools/distrib/python/grpc_version.py b/tools/distrib/python/grpc_version.py
index facf4d07719..7c78587c40e 100644
--- a/tools/distrib/python/grpc_version.py
+++ b/tools/distrib/python/grpc_version.py
@@ -14,5 +14,5 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/tools/distrib/python/grpcio_tools/grpc_version.py.template`!!!
 
-VERSION = '1.60.0.dev0'
+VERSION = '1.61.0.dev0'
 PROTOBUF_VERSION = '3.25.0'
diff --git a/tools/distrib/python/grpcio_tools/grpc_version.py b/tools/distrib/python/grpcio_tools/grpc_version.py
index 6dfd45881fa..f7f3637710e 100644
--- a/tools/distrib/python/grpcio_tools/grpc_version.py
+++ b/tools/distrib/python/grpcio_tools/grpc_version.py
@@ -14,5 +14,5 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/tools/distrib/python/grpcio_tools/grpc_version.py.template`!!!
 
-VERSION = '1.60.0.dev0'
+VERSION = '1.61.0.dev0'
 PROTOBUF_VERSION = '3.25.0'
diff --git a/tools/distrib/python/xds_protos/grpc_version.py b/tools/distrib/python/xds_protos/grpc_version.py
index ed0511384ea..008611094fc 100644
--- a/tools/distrib/python/xds_protos/grpc_version.py
+++ b/tools/distrib/python/xds_protos/grpc_version.py
@@ -14,5 +14,5 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/tools/distrib/python/grpcio_tools/grpc_version.py.template`!!!
 
-VERSION = '1.60.0.dev0'
+VERSION = '1.61.0.dev0'
 PROTOBUF_VERSION = '3.25.0'
diff --git a/tools/doxygen/Doxyfile.c++ b/tools/doxygen/Doxyfile.c++
index 63dbd861883..42eec93cf59 100644
--- a/tools/doxygen/Doxyfile.c++
+++ b/tools/doxygen/Doxyfile.c++
@@ -40,7 +40,7 @@ PROJECT_NAME           = "GRPC C++"
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = 1.60.0-dev
+PROJECT_NUMBER         = 1.61.0-dev
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a
diff --git a/tools/doxygen/Doxyfile.c++.internal b/tools/doxygen/Doxyfile.c++.internal
index b7725a474c1..5905f239563 100644
--- a/tools/doxygen/Doxyfile.c++.internal
+++ b/tools/doxygen/Doxyfile.c++.internal
@@ -40,7 +40,7 @@ PROJECT_NAME           = "GRPC C++"
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = 1.60.0-dev
+PROJECT_NUMBER         = 1.61.0-dev
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a
diff --git a/tools/doxygen/Doxyfile.core b/tools/doxygen/Doxyfile.core
index 91c4e7c623f..6dac1787b71 100644
--- a/tools/doxygen/Doxyfile.core
+++ b/tools/doxygen/Doxyfile.core
@@ -40,7 +40,7 @@ PROJECT_NAME           = "GRPC Core"
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = 36.0.0
+PROJECT_NUMBER         = 37.0.0
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a
diff --git a/tools/doxygen/Doxyfile.core.internal b/tools/doxygen/Doxyfile.core.internal
index f3ba303c93f..aa35ecb50b3 100644
--- a/tools/doxygen/Doxyfile.core.internal
+++ b/tools/doxygen/Doxyfile.core.internal
@@ -40,7 +40,7 @@ PROJECT_NAME           = "GRPC Core"
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = 36.0.0
+PROJECT_NUMBER         = 37.0.0
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a
diff --git a/tools/doxygen/Doxyfile.objc b/tools/doxygen/Doxyfile.objc
index 91af4390c3c..3fff76f4afe 100644
--- a/tools/doxygen/Doxyfile.objc
+++ b/tools/doxygen/Doxyfile.objc
@@ -40,7 +40,7 @@ PROJECT_NAME           = "GRPC Objective-C"
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = 1.60.0-dev
+PROJECT_NUMBER         = 1.61.0-dev
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a
diff --git a/tools/doxygen/Doxyfile.objc.internal b/tools/doxygen/Doxyfile.objc.internal
index fcd6f45dc1d..14320b033a7 100644
--- a/tools/doxygen/Doxyfile.objc.internal
+++ b/tools/doxygen/Doxyfile.objc.internal
@@ -40,7 +40,7 @@ PROJECT_NAME           = "GRPC Objective-C"
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = 1.60.0-dev
+PROJECT_NUMBER         = 1.61.0-dev
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a
diff --git a/tools/doxygen/Doxyfile.php b/tools/doxygen/Doxyfile.php
index 296e31698b2..1299b7e96c4 100644
--- a/tools/doxygen/Doxyfile.php
+++ b/tools/doxygen/Doxyfile.php
@@ -40,7 +40,7 @@ PROJECT_NAME           = "GRPC PHP"
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = 1.60.0-dev
+PROJECT_NUMBER         = 1.61.0-dev
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a
diff --git a/tools/internal_ci/windows/pull_request/grpc_distribtests_cpp_dll.cfg b/tools/internal_ci/windows/pull_request/grpc_distribtests_cpp_dll.cfg
index b673e13ba11..32cb3c2544d 100644
--- a/tools/internal_ci/windows/pull_request/grpc_distribtests_cpp_dll.cfg
+++ b/tools/internal_ci/windows/pull_request/grpc_distribtests_cpp_dll.cfg
@@ -15,7 +15,7 @@
 # Config file for the internal CI (in protobuf text format)
 
 # Location of the continuous shell script in repository.
-build_file: "grpc/tools/internal_ci/windows/grpc_distribtests_standalone.bat"
+build_file: "grpc/tools/internal_ci/windows/grpc_distribtests_cpp_dll.bat"
 timeout_mins: 120
 action {
   define_artifacts {
diff --git a/tools/run_tests/generated/tests.json b/tools/run_tests/generated/tests.json
index f84a171ea9f..35bdddc0eb0 100644
--- a/tools/run_tests/generated/tests.json
+++ b/tools/run_tests/generated/tests.json
@@ -4987,6 +4987,30 @@
     ],
     "uses_polling": true
   },
+  {
+    "args": [],
+    "benchmark": false,
+    "ci_platforms": [
+      "linux",
+      "mac",
+      "posix",
+      "windows"
+    ],
+    "cpu_cost": 1.0,
+    "exclude_configs": [],
+    "exclude_iomgrs": [],
+    "flaky": false,
+    "gtest": true,
+    "language": "c++",
+    "name": "inter_activity_latch_test",
+    "platforms": [
+      "linux",
+      "mac",
+      "posix",
+      "windows"
+    ],
+    "uses_polling": false
+  },
   {
     "args": [],
     "benchmark": false,