diff --git a/Makefile b/Makefile
index 1a734d7f..317906fc 100644
--- a/Makefile
+++ b/Makefile
@@ -434,17 +434,31 @@ test-compiler: $(WWFIXTURE_BIN) $(WRAPPER_TOOLS) $(COMPILER_WRAPPER_BINS)
 		echo "compiler artifact $$t"; BIN=$(CURDIR)/$(BIN) $(CURDIR)/$$t; \
 	done
 
-test-lang: $(BIN)/ww $(BIN)/w6c $(BIN)/w6a $(BIN)/w6l $(LIB)/libwwrt.a
-	@set -e; for f in $(wildcard test/lang/*_test.ww); do \
-		echo "ww test $$f"; $(BIN)/ww test $$f; \
-	done
+# One phony target per language/library test file so `make -jN`
+# parallelizes the suites, each in its own persistent -w workdir so only
+# changed packages rebuild. Tests always execute — the workdir caches
+# builds, never results.
+LANG_TEST_FILES = $(wildcard test/lang/*_test.ww)
+LANG_TEST_TARGETS = $(LANG_TEST_FILES:%=wwtest/%)
+LIBRARY_TEST_TARGETS = $(LIBRARY_TESTS:%=wwtest/%)
 
-test-library: $(BIN)/ww $(BIN)/w6c $(BIN)/w6a $(BIN)/w6l \
-		$(LIB)/libwwrt.a $(BIN)/w6c_ww $(LIBRARY_STANDALONE_SOURCES)
-	@set -e; for f in $(LIBRARY_TESTS); do \
-		echo "ww test $$f"; \
-		$(BIN)/ww test -I $(CURDIR)/lib/ww $$f; \
-	done
+$(LANG_TEST_TARGETS): wwtest/%: $(BIN)/ww \
+		$(BIN)/w6c $(BIN)/w6a $(BIN)/w6l $(LIB)/libwwrt.a
+	@echo "ww test $*"
+	@mkdir -p $(WWBUILD)/wwtest/$(subst /,_,$*)
+	@$(BIN)/ww test -w $(WWBUILD)/wwtest/$(subst /,_,$*) $*
+
+$(LIBRARY_TEST_TARGETS): wwtest/%: $(BIN)/ww \
+		$(BIN)/w6c $(BIN)/w6a $(BIN)/w6l $(LIB)/libwwrt.a
+	@echo "ww test $*"
+	@mkdir -p $(WWBUILD)/wwtest/$(subst /,_,$*)
+	@$(BIN)/ww test -w $(WWBUILD)/wwtest/$(subst /,_,$*) \
+		-I $(CURDIR)/lib/ww $*
+
+test-lang: $(LANG_TEST_TARGETS)
+
+test-library: $(LIBRARY_TEST_TARGETS) $(BIN)/w6c $(BIN)/w6c_ww \
+		$(LIBRARY_STANDALONE_SOURCES)
 	@set -e; for f in $(LIBRARY_STANDALONE_SOURCES); do \
 		echo "library compile c $$f"; \
 		$(CURDIR)/$(BIN)/w6c $(CURDIR)/$$f > /dev/null; \
@@ -807,6 +821,7 @@ nocc:
 .PHONY: all cstage wwstage wwfixture test-wwfixture-process test-wwfixture \
 	test test-unit test-compiler-smoke test-compiler test-package \
 	test-lang test-library test-commit test-lang-byteid \
+	$(LANG_TEST_TARGETS) $(LIBRARY_TEST_TARGETS) \
 	test-data-byteid test-native-byteid test-byteid \
 	test-bootstrap-native test-bootstrap test-incremental \
 	test-platform test-all install clean bootstrap nocc bootstrap-snapshot