diff --git a/deploy/buildtools/buildafi.py b/deploy/buildtools/buildafi.py
index 7d44e261ad..aca2e8d9fc 100644
--- a/deploy/buildtools/buildafi.py
+++ b/deploy/buildtools/buildafi.py
@@ -70,12 +70,12 @@ def replace_rtl_local(conf, buildconfig):
     build_driver(conf, buildconfig)
 
 def gen_replace_rtl_script(conf, buildconfig):
-    """ Run SBT assembly to create FAT jar to send to build hosts along with config-specific shell-script
-        to execute the FAT jar
+    """ Generate config-specific replace-rtl.sh script and any prerequisites to send to build hosts
+        for running Chisel->Verilog generation and population of cl_firesim template in aws-fpga hdk
 
     THIS ALWAYS RUNS LOCALLY"""
 
-    rootLogger.info("Generating FAT jar and replace-rtl.sh for " + str(buildconfig.get_chisel_triplet()))
+    rootLogger.info("Generating replace-rtl.sh for " + str(buildconfig.get_chisel_triplet()))
     sim_local(buildconfig.make_recipe("--quiet gen-replace-rtl-script"))
 
 def build_driver(conf, buildconfig):
@@ -124,14 +124,13 @@ def on_build_failure():
     fpgabuilddir = "hdk/cl/developer_designs/cl_" + buildconfig.get_chisel_triplet()
     fpgatemplatedir = 'hdk/cl/developer_designs/cl_firesim'
     generated_dir = get_sim_makevar(buildconfig, 'GENERATED_DIR')
-    fat_jar = get_sim_makevar(buildconfig, 'FAT_JAR')
+    gen_classpath = get_sim_makevar(buildconfig, 'GEN_CLASSPATH')
 
     # first, copy aws-fpga to the build instance. it will live in
     # the same path on the build host as on the manager
     with StreamLogger('stdout'), StreamLogger('stderr'):
         run('mkdir -p ' + ddir)
         run('mkdir -p ' + generated_dir)
-        run('mkdir -p ' + dirname(fat_jar))
         run('mkdir -p ' + aws_fpga_root)
         run('mkdir -p ' + pjoin(aws_fpga_root, fpgatemplatedir))
         run('mkdir -p ' + pjoin(aws_fpga_root, fpgabuilddir))
@@ -164,18 +163,21 @@ def on_build_failure():
                           extra_opts="-l", capture=True)
             rootLogger.debug(rsync_cap)
             rootLogger.debug(rsync_cap.stderr)
-            # sync the fat jar
-            rsync_cap = rsync_project(local_dir=fat_jar,
-                          remote_dir=fat_jar,
-                          ssh_opts="-o StrictHostKeyChecking=no",
-                          extra_opts="-l", capture=True)
-            rootLogger.debug(rsync_cap)
-            rootLogger.debug(rsync_cap.stderr)
+            # sync all components of the generator classpath
+            # classpath members are directories or archives
+            for e in gen_classpath.split(":"):
+                run('mkdir -p ' + dirname(e))
+                rsync_cap = rsync_project(local_dir=e,
+                              remote_dir=e,
+                              ssh_opts="-o StrictHostKeyChecking=no",
+                              extra_opts="-l", capture=True)
+                rootLogger.debug(rsync_cap)
+                rootLogger.debug(rsync_cap.stderr)
         with InfoStreamLogger('stdout'), InfoStreamLogger('stderr'):
             # install java and dtc on the build host
             sudo('yum install -y java dtc')
             # run the replace-rtl.sh script
-            rootLogger.info("Running process to build verilog from FAT jar.")
+            rootLogger.info("Running Verilog generation via: " + pjoin(generated_dir,'replace-rtl.sh'))
             run('bash -xe ' + pjoin(generated_dir,'replace-rtl.sh'))
         with StreamLogger('stdout'), StreamLogger('stderr'):
             # rsync generated_dir back to manager
diff --git a/sim/Makefile b/sim/Makefile
index edabb84f73..7ead53ef90 100644
--- a/sim/Makefile
+++ b/sim/Makefile
@@ -29,8 +29,7 @@ TARGET_PROJECT_MAKEFRAG ?= $(firesim_base_dir)/src/main/makefrag/$(TARGET_PROJEC
 PLATFORM ?= f1
 
 # If TARGET_PROJECT_MAKEFRAG requires additional PROJECT-specific artifacts in GENERATED_DIR before
-# Chisel->FIRRTL->Verilog is run, register them as prereqs of the pre-elaboration target.  
-# See src/main/makefrag/firesim/Makefrag's BOOTROM_TARGETS for an example
+# Chisel->FIRRTL->Verilog is run, add them to PRE_ELABORATION_TARGETS to register them as prereqs
 PRE_ELABORATION_TARGETS =
 
 ifdef FIRESIM_STANDALONE
@@ -99,8 +98,8 @@ ifdef ENABLE_SBT_THIN_CLIENT
     # continue to use SBT for main class invocations of the generator and goldengate
     run_main = run_scala_main
 else
-    # recipes for generator and gg using sbt are calls out to FAT_JAR instead of SBT
-    run_main = cd $(base_dir) && java $(JAVA_OPTS) -cp $(FAT_JAR) $(2) $(3)
+    # recipes for generator and gg are now java invocations using GEN_CLASSPATH instead of SBT
+    run_main = cd $(base_dir) && java $(JAVA_OPTS) -cp $(GEN_CLASSPATH) $(2) $(3)
 endif
 
 # Include target-specific sources and input generation recipes
diff --git a/sim/src/main/makefrag/fasedtests/Makefrag b/sim/src/main/makefrag/fasedtests/Makefrag
index 881ddf15b6..35d2af4812 100644
--- a/sim/src/main/makefrag/fasedtests/Makefrag
+++ b/sim/src/main/makefrag/fasedtests/Makefrag
@@ -15,9 +15,9 @@ TARGET_CONFIG ?= DefaultConfig
 PLATFORM_CONFIG_PACKAGE ?= firesim.fasedtests
 PLATFORM_CONFIG ?= DefaultF1Config
 
-name_tuple    := $(DESIGN)-$(TARGET_CONFIG)-$(PLATFORM_CONFIG)
-GENERATED_DIR := $(firesim_base_dir)/generated-src/$(PLATFORM)/$(name_tuple)
-OUTPUT_DIR    := $(firesim_base_dir)/output/$(PLATFORM)/$(name_tuple)
+name_tuple    ?= $(DESIGN)-$(TARGET_CONFIG)-$(PLATFORM_CONFIG)
+GENERATED_DIR ?= $(firesim_base_dir)/generated-src/$(PLATFORM)/$(name_tuple)
+OUTPUT_DIR    ?= $(firesim_base_dir)/output/$(PLATFORM)/$(name_tuple)
 
 ##################
 # RTL Generation #
@@ -31,10 +31,6 @@ HEADER  := $(GENERATED_DIR)/$(DESIGN)-const.h
 
 CONF_NAME ?= runtime.conf
 firesim_sbt_project := {file:${firesim_base_dir}/}firesim
-FAT_JAR := $(firesim_base_dir)/generated-src/firesim.jar
-PRE_ELABORATION_TARGETS += $(FAT_JAR)
-
-
 
 chisel_src_dirs = \
 		$(addprefix $(firesim_base_dir)/,. midas midas/targetutils firesim-lib) \
@@ -43,12 +39,40 @@ chisel_src_dirs = \
 chisel_srcs = $(foreach submodule,$(chisel_src_dirs),\
 	$(shell find $(submodule)/ -iname "[!.]*.scala" -print 2> /dev/null | grep 'src/main/scala'))
 
-# don't search for implicit rules to make the chisel_srcs (reduces useless output in --debug=i)
+# don't search for implicit rules to make the chisel_srcs (reduces useless output in make --debug)
 $(chisel_srcs): ;
 
-$(FAT_JAR): $(chisel_srcs) $(SCALA_BUILDTOOL_DEPS)
+GEN_CLASSPATH_ORDERONLY_DEPS ?=
+
+ifndef GEN_CLASSPATH
+  GEN_CLASSPATH = $(firesim_base_dir)/generated-src/firesim.jar
+  jardir = $(dir $(GEN_CLASSPATH))
+  GEN_CLASSPATH_ORDERONLY_DEPS += $(jardir)
+
+  $(jardir):
 	mkdir -p $(@D)
-	$(SBT) "project $(firesim_sbt_project)" 'set assemblyOutputPath in assembly := file("$(FAT_JAR)")' assembly
+
+endif
+GEN_CLASSPATH_DEPS ?= $(chisel_srcs) $(SCALA_BUILDTOOL_DEPS)
+
+# if GEN_CLASSPATH is a true java classpath, it can be colon-delimited list of paths (on *nix)
+GEN_CLASSPATH_TARGETS ?= $(subst :, ,$(GEN_CLASSPATH))
+
+ifndef ENABLE_SBT_THIN_CLIENT
+  PRE_ELABORATION_TARGETS += $(GEN_CLASSPATH_TARGETS)
+endif
+
+GEN_CLASSPATH_RECIPE ?= cd $(base_dir) && $(SBT) "project $(firesim_sbt_project); set assemblyOutputPath in assembly := file(\"$(GEN_CLASSPATH)\"); assembly"
+
+
+# empty recipe to help make understand multiple targets come from single invocation
+# without using the new (4.3) '&:' grouped targets
+# see https://stackoverflow.com/a/41710495
+$(GEN_CLASSPATH_TARGETS):  classpath.intermediate ;
+
+.SECONDARY: classpath.intermediate
+classpath.intermediate:  $(GEN_CLASSPATH_DEPS) | $(GEN_CLASSPATH_ORDERONLY_DEPS)
+	$(GEN_CLASSPATH_RECIPE)
 
 # empty recipe to help make understand multiple targets come from single invocation
 # without using the new (4.3) '&:' grouped targets
diff --git a/sim/src/main/makefrag/firesim/Makefrag b/sim/src/main/makefrag/firesim/Makefrag
index 30809bb7a6..e26f1cfeb5 100644
--- a/sim/src/main/makefrag/firesim/Makefrag
+++ b/sim/src/main/makefrag/firesim/Makefrag
@@ -54,6 +54,38 @@ PRE_ELABORATION_TARGETS += $(BOOTROM_TARGETS)
 # Don't search for implicit rules to build the scala sources or bootrom sources (reduces useless output in --debug)
 $(SCALA_SOURCES) $(addprefix $(CHIPYARD_ROMDIR)/, $(BOOTROM_FILES)): ;
 
+GEN_CLASSPATH_ORDERONLY_DEPS ?=
+
+ifndef GEN_CLASSPATH
+  GEN_CLASSPATH = $(firesim_base_dir)/generated-src/firechip.jar
+  jardir = $(dir $(GEN_CLASSPATH))
+  GEN_CLASSPATH_ORDERONLY_DEPS += $(jardir)
+
+  $(jardir):
+	mkdir -p $(@D)
+
+endif
+GEN_CLASSPATH_DEPS ?= $(chisel_srcs) $(SCALA_BUILDTOOL_DEPS)
+
+# if GEN_CLASSPATH is a true java classpath, it can be colon-delimited list of paths (on *nix)
+GEN_CLASSPATH_TARGETS ?= $(subst :, ,$(GEN_CLASSPATH))
+
+ifndef ENABLE_SBT_THIN_CLIENT
+  PRE_ELABORATION_TARGETS += $(GEN_CLASSPATH_TARGETS)
+endif
+
+GEN_CLASSPATH_RECIPE ?= cd $(base_dir) && $(SBT) "project $(firesim_sbt_project); set assemblyOutputPath in assembly := file(\"$(GEN_CLASSPATH)\"); assembly"
+
+
+# empty recipe to help make understand multiple targets come from single invocation
+# without using the new (4.3) '&:' grouped targets
+# see https://stackoverflow.com/a/41710495
+$(GEN_CLASSPATH_TARGETS):  classpath.intermediate ;
+
+.SECONDARY: classpath.intermediate
+classpath.intermediate:  $(GEN_CLASSPATH_DEPS) | $(GEN_CLASSPATH_ORDERONLY_DEPS)
+	$(GEN_CLASSPATH_RECIPE)
+
 GENERATOR_NAME ?= chipyard.Generator
 GENERATOR_ARGS ?= \
 		--target-dir $(GENERATED_DIR) \
@@ -61,18 +93,7 @@ GENERATOR_ARGS ?= \
 		--top-module $(DESIGN_PACKAGE).$(DESIGN) \
 		--legacy-configs $(TARGET_CONFIG_PACKAGE):$(TARGET_CONFIG)
 
-FAT_JAR ?= $(firesim_base_dir)/generated-src/firechip.jar
-FAT_JAR_DEPS ?= $(SCALA_SOURCES) $(SCALA_BUILDTOOL_DEPS)
-FAT_JAR_RECIPE ?= cd $(base_dir) && $(SBT) "project $(firesim_sbt_project); set assemblyOutputPath in assembly := file(\"$(FAT_JAR)\"); assembly"
-
-fat_jar_dir := $(dir $(FAT_JAR))
-$(fat_jar_dir):
-	mkdir -p $@
 
-$(FAT_JAR):  $(FAT_JAR_DEPS) | $(fat_jar_dir)
-	$(FAT_JAR_RECIPE)
-
-PRE_ELABORATION_TARGETS += $(FAT_JAR)
 
 # empty recipe to help make understand multiple targets come from single invocation
 # without using the new (4.3) '&:' grouped targets see https://stackoverflow.com/a/41710495
@@ -82,7 +103,6 @@ $(FIRRTL_FILE) $(ANNO_FILE): $(FIRRTL_FILE).intermediate ;
 $(FIRRTL_FILE).intermediate: $(SCALA_SOURCES) $(PRE_ELABORATION_TARGETS) | $(GENERATED_DIR)
 	$(call run_main,$(firesim_sbt_project),$(GENERATOR_NAME),$(GENERATOR_ARGS))
 
-
 # DOC include start: Bridge Build System Changes
 ##########################
 # Driver Sources & Flags #
diff --git a/sim/src/main/makefrag/midasexamples/Makefrag b/sim/src/main/makefrag/midasexamples/Makefrag
index 3609505b8d..1885b552f7 100644
--- a/sim/src/main/makefrag/midasexamples/Makefrag
+++ b/sim/src/main/makefrag/midasexamples/Makefrag
@@ -10,9 +10,9 @@ TARGET_CONFIG ?= NoConfig
 PLATFORM_CONFIG_PACKAGE ?= firesim.midasexamples
 PLATFORM_CONFIG ?= DefaultF1Config
 
-name_tuple    := $(DESIGN)-$(TARGET_CONFIG)-$(PLATFORM_CONFIG)
-GENERATED_DIR := $(firesim_base_dir)/generated-src/$(PLATFORM)/$(name_tuple)
-OUTPUT_DIR    := $(firesim_base_dir)/output/$(PLATFORM)/$(name_tuple)
+name_tuple    ?= $(DESIGN)-$(TARGET_CONFIG)-$(PLATFORM_CONFIG)
+GENERATED_DIR ?= $(firesim_base_dir)/generated-src/$(PLATFORM)/$(name_tuple)
+OUTPUT_DIR    ?= $(firesim_base_dir)/output/$(PLATFORM)/$(name_tuple)
 
 ##########################
 # RTL Generation         #
@@ -30,10 +30,6 @@ else
 	firesim_sbt_project := {file:${firesim_base_dir}/}firesim
 endif
 
-# FAT_JAR is applicable across config tuples but is tied to the sbt project
-FAT_JAR := $(firesim_base_dir)/generated-src/firesim.jar
-PRE_ELABORATION_TARGETS += $(FAT_JAR)
-
 chisel_src_dirs = \
 		$(addprefix $(firesim_base_dir)/,. midas midas/targetutils firesim-lib) \
 		$(addprefix $(chipyard_dir)/generators/, chipyard rocket-chip/src, rocket-chip/api-config-chipsalliance)
@@ -44,9 +40,42 @@ chisel_srcs = $(foreach submodule,$(chisel_src_dirs),\
 # don't search for implicit rules to make the chisel_srcs (reduces useless output in --debug=i)
 $(chisel_srcs): ;
 
-$(FAT_JAR):  $(chisel_srcs) $(SCALA_BUILDTOOL_DEPS)
+GEN_CLASSPATH_ORDERONLY_DEPS ?=
+
+# GEN_CLASSPATH is applicable across config tuples but is tied to the sbt project
+ifndef GEN_CLASSPATH
+  GEN_CLASSPATH = $(firesim_base_dir)/generated-src/firesim.jar
+  jardir = $(dir $(GEN_CLASSPATH))
+  GEN_CLASSPATH_ORDERONLY_DEPS += $(jardir)
+
+  $(jardir):
+	mkdir -p $(@D)
+
+endif
+GEN_CLASSPATH_DEPS ?= $(chisel_srcs) $(SCALA_BUILDTOOL_DEPS)
+
+# if GEN_CLASSPATH is a true java classpath, it can be colon-delimited list of paths (on *nix)
+GEN_CLASSPATH_TARGETS ?= $(subst :, ,$(GEN_CLASSPATH))
+
+ifndef ENABLE_SBT_THIN_CLIENT
+  PRE_ELABORATION_TARGETS += $(GEN_CLASSPATH_TARGETS)
+endif
+
+GEN_CLASSPATH_RECIPE ?= cd $(base_dir) && $(SBT) "project $(firesim_sbt_project); set assemblyOutputPath in assembly := file(\"$(GEN_CLASSPATH)\"); assembly"
+
+
+# empty recipe to help make understand multiple targets come from single invocation
+# without using the new (4.3) '&:' grouped targets
+# see https://stackoverflow.com/a/41710495
+$(GEN_CLASSPATH_TARGETS):  classpath.intermediate ;
+
+.SECONDARY: classpath.intermediate
+classpath.intermediate:  $(GEN_CLASSPATH_DEPS) | $(GEN_CLASSPATH_ORDERONLY_DEPS)
+	$(GEN_CLASSPATH_RECIPE)
+
+$(GEN_CLASSPATH):  $(chisel_srcs) $(SCALA_BUILDTOOL_DEPS)
 	mkdir -p $(@D)
-	$(SBT) "project $(firesim_sbt_project)" 'set assemblyOutputPath in assembly := file("$(FAT_JAR)")' assembly
+	$(SBT) "project $(firesim_sbt_project)" 'set assemblyOutputPath in assembly := file("$(GEN_CLASSPATH)")' assembly
 
 CONF_NAME ?= runtime.conf
 
diff --git a/sim/target-agnostic.mk b/sim/target-agnostic.mk
index 32b47a0652..fe577d6f03 100644
--- a/sim/target-agnostic.mk
+++ b/sim/target-agnostic.mk
@@ -1,8 +1,10 @@
 # See LICENSE for license details.
 
 # FireSim MAKEFRAG interface - Compulsory variables follow
-# The FAT JAR created using sbt assembly
-FAT_JAR ?=
+# The Generator CLASSPATH used in java invocation to run generator and goldengate. Can be:
+#  - FAT JAR created using sbt assembly
+#  - An actual Java classpath created some other way
+GEN_CLASSPATH ?=
 # The directory into which generated verilog and headers will be dumped
 # RTL simulations will also be built here
 GENERATED_DIR ?=
@@ -85,11 +87,9 @@ $(VERILOG).intermediate: $(FIRRTL_FILE) $(ANNO_FILE) $(PRE_ELABORATION_TARGETS)
 # to generate a runtime configuration that is compatible with the generated
 # hardware (BridgeModule). Useful for modelling a memory system that differs from the default.
 .PHONY: conf
-conf: $(fame_annos) $(FAT_JAR)
+conf: $(fame_annos) $(GEN_CLASSPATH)
 	mkdir -p $(GENERATED_DIR)
-	# Runtime configuration generator must run under SBT currently; When
-	# launched via bloop some Console input and output is lost.
-	cd $(base_dir) && java $(JAVA_OPTS) -cp $(FAT_JAR) midas.stage.RuntimeConfigGeneratorMain \
+	cd $(base_dir) && java $(JAVA_OPTS) -cp $(GEN_CLASSPATH) midas.stage.RuntimeConfigGeneratorMain \
 		-td $(GENERATED_DIR) \
 		-faf $(fame_annos) \
 		-ggcp $(PLATFORM_CONFIG_PACKAGE) \
@@ -234,13 +234,13 @@ fpga: $(fpga_v) $(base_dir)/scripts/checkpoints/$(name_tuple)
 
 # Generate a script that can be run remotely on a build host by manager assuming only the following
 # are copied (recursively with Fabric's rsync_project) to the build-host:
-# - $(FAT_JAR)
+# - $(GEN_CLASSPATH)
 # - $(GENERATED_DIR)
 # - $(board_dir)/cl_firesim
 # The script will be run with 'bash -xe' to approximate the behavior of make shell execution
 #  --no-print-directory avoids some info print statements that aren't actual commands
-#  --assume-new=$(FAT_JAR) ensures that the script consistently generates the commands for
-#  $(FAT_JAR) -> replace-rtl, regardless of whether they need to be done.  This is done so that
+#  --assume-new=$(PRE_ELABORATION_TARGETS) ensures that the script consistently generates the commands for
+#  $(PRE_ELABORATION_TARGETS) -> replace-rtl, regardless of whether they need to be done.  This is done so that
 #  replace-rtl.sh should always be legit commands and we don't have to handle shortcuts for output
 #  that look like "make: Nothing to be done for `replace-rtl'."
 .PHONY: gen-replace-rtl-script