diff --git a/Changes.md b/Changes.md
index 6c0cf70..fc15e60 100644
--- a/Changes.md
+++ b/Changes.md
@@ -1,5 +1,14 @@
 # Build System Changes for Android.mk/Android.bp Writers
 
+## Soong genrules are now sandboxed
+
+Previously, soong genrules could access any files in the source tree, without specifying them as
+inputs. This makes them incorrect in incremental builds, and incompatible with RBE and Bazel.
+
+Now, genrules are sandboxed so they can only access their listed srcs. Modules denylisted in
+genrule/allowlists.go are exempt from this. You can also set `BUILD_BROKEN_GENRULE_SANDBOXING`
+in board config to disable this behavior.
+
 ## Partitions are no longer affected by previous builds
 
 Partition builds used to include everything in their staging directories, and building an
diff --git a/core/board_config.mk b/core/board_config.mk
index eb4c5ec..a0e5d36 100644
--- a/core/board_config.mk
+++ b/core/board_config.mk
@@ -188,6 +188,7 @@
   BUILD_BROKEN_VENDOR_PROPERTY_NAMESPACE \
   BUILD_BROKEN_VINTF_PRODUCT_COPY_FILES \
   BUILD_BROKEN_INCORRECT_PARTITION_IMAGES \
+  BUILD_BROKEN_GENRULE_SANDBOXING \
 
 _build_broken_var_list += \
   $(foreach m,$(AVAILABLE_BUILD_MODULE_TYPES) \
diff --git a/core/soong_config.mk b/core/soong_config.mk
index f68c741..23e017e 100644
--- a/core/soong_config.mk
+++ b/core/soong_config.mk
@@ -16,6 +16,10 @@
 # PRODUCT_AFDO_PROFILES takes precedence over product-agnostic profiles in AFDO_PROFILES
 ALL_AFDO_PROFILES := $(PRODUCT_AFDO_PROFILES) $(AFDO_PROFILES)
 
+ifneq (,$(filter-out environment undefined,$(origin GENRULE_SANDBOXING)))
+  $(error GENRULE_SANDBOXING can only be provided via an environment variable, use BUILD_BROKEN_GENRULE_SANDBOXING to disable genrule sandboxing in board config)
+endif
+
 ifeq ($(WRITE_SOONG_VARIABLES),true)
 
 # Create soong.variables with copies of makefile settings.  Runs every build,
@@ -281,7 +285,8 @@
 $(call add_json_bool, BuildBrokenClangProperty,            $(filter true,$(BUILD_BROKEN_CLANG_PROPERTY)))
 $(call add_json_bool, BuildBrokenClangAsFlags,             $(filter true,$(BUILD_BROKEN_CLANG_ASFLAGS)))
 $(call add_json_bool, BuildBrokenClangCFlags,              $(filter true,$(BUILD_BROKEN_CLANG_CFLAGS)))
-$(call add_json_bool, GenruleSandboxing,                   $(filter true,$(GENRULE_SANDBOXING)))
+# Use the value of GENRULE_SANDBOXING if set, otherwise use the inverse of BUILD_BROKEN_GENRULE_SANDBOXING
+$(call add_json_bool, GenruleSandboxing,                   $(if $(GENRULE_SANDBOXING),$(filter true,$(GENRULE_SANDBOXING)),$(if $(filter true,$(BUILD_BROKEN_GENRULE_SANDBOXING)),,true)))
 $(call add_json_bool, BuildBrokenEnforceSyspropOwner,      $(filter true,$(BUILD_BROKEN_ENFORCE_SYSPROP_OWNER)))
 $(call add_json_bool, BuildBrokenTrebleSyspropNeverallow,  $(filter true,$(BUILD_BROKEN_TREBLE_SYSPROP_NEVERALLOW)))
 $(call add_json_bool, BuildBrokenUsesSoongPython2Modules,  $(filter true,$(BUILD_BROKEN_USES_SOONG_PYTHON2_MODULES)))