diff --git a/core/main.mk b/core/main.mk
index 7433f90..41d903b 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -10,9 +10,6 @@
 endif
 
 ifndef KATI
-USE_SOONG_UI ?= true
-endif
-ifeq ($(USE_SOONG_UI),true)
 
 host_prebuilts := linux-x86
 ifeq ($(shell uname),Darwin)
@@ -27,7 +24,7 @@
 $(sort $(MAKECMDGOALS)) : run_soong_ui
 	@#empty
 
-else # USE_SOONG_UI
+else # KATI
 
 # Absolute path of the present working direcotry.
 # This overrides the shell variable $PWD, which does not necessarily points to
@@ -47,23 +44,10 @@
 .PHONY: droid_targets
 droid_targets:
 
-# Targets that provide quick help on the build system.
-include $(BUILD_SYSTEM)/help.mk
-
 # Set up various standard variables based on configuration
 # and host information.
 include $(BUILD_SYSTEM)/config.mk
 
-ifndef KATI
-ifdef USE_NINJA
-$(warning USE_NINJA is ignored. Ninja is always used.)
-endif
-
-# Mark this is a ninja build.
-$(shell mkdir -p $(OUT_DIR) && touch $(OUT_DIR)/ninja_build)
-include build/core/ninja.mk
-else # KATI
-
 ifneq ($(filter $(dont_bother_goals), $(MAKECMDGOALS)),)
 dont_bother := true
 endif
@@ -1149,4 +1133,3 @@
 all_link_types:
 
 endif # KATI
-endif # USE_SOONG_UI
diff --git a/core/ninja.mk b/core/ninja.mk
deleted file mode 100644
index af2ede0..0000000
--- a/core/ninja.mk
+++ /dev/null
@@ -1,103 +0,0 @@
-include $(BUILD_SYSTEM)/soong.mk
-
-# Modifier goals we don't need to pass to Ninja.
-.PHONY : $(NINJA_EXCLUDE_GOALS)
-
-define replace_space_and_slash
-$(subst /,_,$(subst $(space),_,$(sort $1)))
-endef
-
-KATI_NINJA_SUFFIX := -$(TARGET_PRODUCT)
-ifneq ($(KATI_GOALS),)
-KATI_NINJA_SUFFIX := $(KATI_NINJA_SUFFIX)-$(call replace_space_and_slash,$(KATI_GOALS))
-endif
-ifneq ($(ONE_SHOT_MAKEFILE),)
-KATI_NINJA_SUFFIX := $(KATI_NINJA_SUFFIX)-mmm-$(call replace_space_and_slash,$(ONE_SHOT_MAKEFILE))
-endif
-
-my_checksum_suffix :=
-my_ninja_suffix_too_long := $(filter 1, $(shell v='$(KATI_NINJA_SUFFIX)' && echo $$(($${$(pound)v} > 64))))
-ifneq ($(my_ninja_suffix_too_long),)
-# Replace the suffix with a checksum if it gets too long.
-my_checksum_suffix := $(KATI_NINJA_SUFFIX)
-KATI_NINJA_SUFFIX := -$(word 1, $(shell echo $(my_checksum_suffix) | $(MD5SUM)))
-endif
-
-KATI_BUILD_NINJA := $(OUT_DIR)/build$(KATI_NINJA_SUFFIX).ninja
-KATI_ENV_SH := $(OUT_DIR)/env$(KATI_NINJA_SUFFIX).sh
-
-# Write out a file mapping checksum to the real suffix.
-ifneq ($(my_checksum_suffix),)
-my_ninja_suffix_file := $(basename $(KATI_BUILD_NINJA)).suf
-$(shell mkdir -p $(dir $(my_ninja_suffix_file)) && \
-    echo $(my_checksum_suffix) > $(my_ninja_suffix_file))
-endif
-
-ifeq (,$(NINJA_STATUS))
-NINJA_STATUS := [%p %f/%t]$(space)
-endif
-
-NINJA_EXTRA_ARGS :=
-
-ifneq (,$(filter showcommands,$(ORIGINAL_MAKECMDGOALS)))
-NINJA_EXTRA_ARGS += "-v"
-endif
-
-# Make multiple rules to generate the same target an error instead of
-# proceeding with undefined behavior.
-NINJA_EXTRA_ARGS += -w dupbuild=err
-
-ifneq ($(filter-out false,$(USE_GOMA)),)
-KATI_MAKEPARALLEL := $(MAKEPARALLEL)
-# Ninja runs remote jobs (i.e., commands which contain gomacc) with
-# this parallelism. Note the parallelism of all other jobs is still
-# limited by the -j flag passed to GNU make.
-NINJA_REMOTE_NUM_JOBS ?= 500
-NINJA_EXTRA_ARGS += -j$(NINJA_REMOTE_NUM_JOBS)
-else
-NINJA_MAKEPARALLEL := $(MAKEPARALLEL) --ninja
-
-# We never want Kati to see MAKEFLAGS, as forcefully overriding variables is
-# terrible. The variables in MAKEFLAGS are still available in the environment,
-# so if part of the build wants input from the user, it should be explicitly
-# checking for an environment variable or using ?=
-#
-# makeparallel already clears MAKEFLAGS, so it's not necessary in the GOMA case
-KATI_MAKEPARALLEL := MAKEFLAGS=
-endif
-
-NINJA_ARGS += $(NINJA_EXTRA_ARGS)
-
-COMBINED_BUILD_NINJA := $(OUT_DIR)/combined$(KATI_NINJA_SUFFIX).ninja
-
-$(COMBINED_BUILD_NINJA): $(KATI_BUILD_NINJA) FORCE
-	$(hide) echo "builddir = $(OUT_DIR)" > $(COMBINED_BUILD_NINJA)
-	$(hide) echo "include $(KATI_BUILD_NINJA)" >> $(COMBINED_BUILD_NINJA)
-	$(hide) echo "include $(SOONG_BUILD_NINJA)" >> $(COMBINED_BUILD_NINJA)
-	$(hide) echo "build $(COMBINED_BUILD_NINJA): phony $(SOONG_BUILD_NINJA)" >> $(COMBINED_BUILD_NINJA)
-
-$(sort $(DEFAULT_GOAL) $(ANDROID_GOALS)) : ninja_wrapper
-	@#empty
-
-.PHONY: ninja_wrapper
-ninja_wrapper: $(COMBINED_BUILD_NINJA) $(MAKEPARALLEL)
-	@echo Starting build with ninja
-	+$(hide) export NINJA_STATUS="$(NINJA_STATUS)" && source $(KATI_ENV_SH) && exec $(NINJA_MAKEPARALLEL) $(NINJA) -d keepdepfile $(NINJA_GOALS) -C $(TOP) -f $(COMBINED_BUILD_NINJA) $(NINJA_ARGS)
-
-# Dummy Android.mk and CleanSpec.mk files so that kati won't recurse into the
-# out directory
-DUMMY_OUT_MKS := $(OUT_DIR)/Android.mk $(OUT_DIR)/CleanSpec.mk
-$(DUMMY_OUT_MKS):
-	@mkdir -p $(dir $@)
-	$(hide) echo '# This file prevents findleaves.py from traversing this directory further' >$@
-
-KATI_FIND_EMULATOR := --use_find_emulator
-ifeq ($(KATI_EMULATE_FIND),false)
-  KATI_FIND_EMULATOR :=
-endif
-$(KATI_BUILD_NINJA): $(CKATI) $(MAKEPARALLEL) $(DUMMY_OUT_MKS) run_soong FORCE
-	@echo Running kati to generate build$(KATI_NINJA_SUFFIX).ninja...
-	+$(hide) $(KATI_MAKEPARALLEL) $(CKATI) --ninja --ninja_dir=$(OUT_DIR) --ninja_suffix=$(KATI_NINJA_SUFFIX) --regen --ignore_optional_include=$(OUT_DIR)/%.P --detect_android_echo $(KATI_FIND_EMULATOR) -f build/core/main.mk $(KATI_GOALS) --gen_all_targets BUILDING_WITH_NINJA=true SOONG_ANDROID_MK=$(SOONG_ANDROID_MK) SOONG_MAKEVARS_MK=$(SOONG_MAKEVARS_MK)
-
-.PHONY: FORCE
-FORCE:
diff --git a/core/soong.mk b/core/soong.mk
deleted file mode 100644
index 4a74f2e..0000000
--- a/core/soong.mk
+++ /dev/null
@@ -1,29 +0,0 @@
-# We need to rebootstrap soong if SOONG_OUT_DIR or the reverse path from
-# SOONG_OUT_DIR to TOP changes
-SOONG_NEEDS_REBOOTSTRAP :=
-ifneq ($(wildcard $(SOONG_BOOTSTRAP)),)
-  ifneq ($(SOONG_OUT_DIR),$(strip $(shell source $(SOONG_BOOTSTRAP); echo $$BUILDDIR)))
-    SOONG_NEEDS_REBOOTSTRAP := FORCE
-    $(warning soong_out_dir changed)
-  endif
-  ifneq ($(strip $(shell build/soong/scripts/reverse_path.py $(SOONG_OUT_DIR))),$(strip $(shell source $(SOONG_BOOTSTRAP); echo $$SRCDIR_FROM_BUILDDIR)))
-    SOONG_NEEDS_REBOOTSTRAP := FORCE
-    $(warning reverse path changed)
-  endif
-endif
-
-# Bootstrap soong.
-$(SOONG_BOOTSTRAP): bootstrap.bash $(SOONG_NEEDS_REBOOTSTRAP)
-	$(hide) mkdir -p $(dir $@)
-	$(hide) BUILDDIR=$(SOONG_OUT_DIR) ./bootstrap.bash
-
-# Tell soong that it is embedded in make
-$(SOONG_IN_MAKE):
-	$(hide) mkdir -p $(dir $@)
-	$(hide) touch $@
-
-# Run Soong, this implicitly create an Android.mk listing all soong outputs as
-# prebuilts.
-.PHONY: run_soong
-run_soong: $(SOONG_BOOTSTRAP) $(SOONG_VARIABLES) $(SOONG_IN_MAKE) FORCE
-	$(hide) SKIP_NINJA=true $(SOONG)