diff --git a/test/sep/importdir_test.ww b/test/sep/importdir_test.ww
index 40ebfd05..4993b078 100644
--- a/test/sep/importdir_test.ww
+++ b/test/sep/importdir_test.ww
@@ -100,11 +100,11 @@ fn samefile(a: str, b: str, why: str) void = {
 	let wantroot: str = strings.concat("//ww:module-reset main\n", appsrc,
 		"\n");
 	if (!testenv.same(wantroot, testenv.readfile(strings.concat(cwork,
-		"__root.unit.ww")))) {
+		"main.unit.ww")))) {
 		fail("root unit is not exactly its owned source");
 	};
 	let keys: []str = ["example.base", "example.bar", "example.foo",
-		"__root"];
+		"main"];
 	let suffixes: []str = [".unit.ww", ".wwi", ".a"];
 	i = 0;
 	for (i < keys.len) {
diff --git a/test/sep/localbuild_test.ww b/test/sep/localbuild_test.ww
index 6d97ee5d..93272dbf 100644
--- a/test/sep/localbuild_test.ww
+++ b/test/sep/localbuild_test.ww
@@ -289,8 +289,8 @@ fn rejectstable(dir: str, label: str, target: str, needle: str) void = {
 	let expectedunit: str = strings.concat("//ww:module-reset main\n",
 		mainsrc, "\n");
 	if (!testenv.same(expectedunit, testenv.readfile(strings.concat(cwork,
-	    "__root.unit.ww"))) || !testenv.same(expectedunit,
-	    testenv.readfile(strings.concat(wwork, "__root.unit.ww")))) {
+	    "main.unit.ww"))) || !testenv.same(expectedunit,
+	    testenv.readfile(strings.concat(wwork, "main.unit.ww")))) {
 		fail("self-contained", "consumer unit was not exactly its owned source");
 	};
 	if (!testenv.exists(strings.concat(cwork, "implementation.a"))
@@ -404,7 +404,7 @@ fn writediamond(td: str, reverse: bool) str = {
 			fail("diamond", "shared package was not interned exactly once");
 		};
 		let unit: str = testenv.readfile(strings.concat(scratch,
-			"__root.unit.ww"));
+			"main.unit.ww"));
 		let rootbody: str = testenv.readfile(strings.concat(main, "/main.ww"));
 		let wantroot: str = strings.concat("//ww:module-reset main\n", rootbody,
 			"\n");
@@ -446,8 +446,8 @@ fn writediamond(td: str, reverse: bool) str = {
 	let firstscratch: str = strings.concat(firstout, ".sepwork/");
 	let shuffledscratch: str = strings.concat(shuffledout, ".sepwork/");
 	if (!testenv.same(testenv.readfile(strings.concat(firstscratch,
-	    "__root.unit.ww")), testenv.readfile(strings.concat(shuffledscratch,
-	    "__root.unit.ww"))) || !testenv.same(testenv.readfile(strings.concat(
+	    "main.unit.ww")), testenv.readfile(strings.concat(shuffledscratch,
+	    "main.unit.ww"))) || !testenv.same(testenv.readfile(strings.concat(
 	    firstscratch, "shared.unit.ww")), testenv.readfile(strings.concat(
 	    shuffledscratch, "shared.unit.ww")))) {
 		fail("diamond", "shuffled enumeration changed package units");
@@ -567,7 +567,7 @@ fn writediamond(td: str, reverse: bool) str = {
 			};
 
 			let rootunit: str = testenv.readfile(strings.concat(work,
-				"__root.unit.ww"));
+				"main.unit.ww"));
 			let depunit: str = testenv.readfile(strings.concat(work,
 				"dep.unit.ww"));
 			if (!testenv.has(rootunit, "//ww:module-reset main\npackage main;")
@@ -580,9 +580,9 @@ fn writediamond(td: str, reverse: bool) str = {
 			    || !testenv.exists(strings.concat(work, "leaf.a"))
 			    || !testenv.exists(strings.concat(work, "dep.wwi"))
 			    || !testenv.exists(strings.concat(work, "dep.a"))
-			    || !testenv.exists(strings.concat(work, "__root.o"))
-			    || !testenv.exists(strings.concat(work, "__root.wwi"))
-			    || !testenv.exists(strings.concat(work, "__root.a"))) {
+			    || !testenv.exists(strings.concat(work, "main.o"))
+			    || !testenv.exists(strings.concat(work, "main.wwi"))
+			    || !testenv.exists(strings.concat(work, "main.a"))) {
 				fail("library-roots", "package artifacts do not match root ownership");
 			};
 			let ctrace: str = testenv.readfile(compilertrace);
@@ -593,13 +593,13 @@ fn writediamond(td: str, reverse: bool) str = {
 			    || testenv.occurrences(ctrace, strings.concat("<", work,
 				"dep.unit.ww>")) != 1
 			    || testenv.occurrences(ctrace, strings.concat("<", work,
-				"__root.unit.ww>")) != 1
+				"main.unit.ww>")) != 1
 			    || testenv.pos(ctrace, strings.concat("<", work,
 				"leaf.unit.ww>")) >= testenv.pos(ctrace, strings.concat("<",
 				work, "dep.unit.ww>"))
 			    || testenv.pos(ctrace, strings.concat("<", work,
 				"dep.unit.ww>")) >= testenv.pos(ctrace, strings.concat("<",
-				work, "__root.unit.ww>"))) {
+				work, "main.unit.ww>"))) {
 				fail("library-roots", "compiler actions were not deterministic postorder");
 			};
 			if (!testenv.has(ctrace, strings.concat(
@@ -608,8 +608,8 @@ fn writediamond(td: str, reverse: bool) str = {
 				"dep.s><", work, "dep.unit.ww>"))
 			    || !testenv.has(ctrace, strings.concat(
 				"BEGIN<--entry><-c><--import><dep><", work,
-				"dep.wwi><-I><", work, "__root.wwi><-o><", work,
-				"__root.s><", work, "__root.unit.ww>"))
+				"dep.wwi><-I><", work, "main.wwi><-o><", work,
+				"main.s><", work, "main.unit.ww>"))
 			    || testenv.occurrences(atrace, "\n") != 3
 			    || !testenv.has(atrace, strings.concat("BEGIN<-o><", work,
 				"dep.o><", work, "dep.s>"))) {
@@ -617,7 +617,7 @@ fn writediamond(td: str, reverse: bool) str = {
 			};
 			if (testenv.occurrences(ltrace, "\n") != 1
 			    || !testenv.has(ltrace, strings.concat("BEGIN<-o><", bin, "><",
-				work, "__root.a>"))
+				work, "main.a>"))
 			    || testenv.pos(ltrace, strings.concat("<", work, "dep.a>")) < 0
 			    || testenv.pos(ltrace, strings.concat("<", work, "leaf.a>"))
 				< testenv.pos(ltrace, strings.concat("<", work, "dep.a>"))
@@ -651,9 +651,9 @@ fn writediamond(td: str, reverse: bool) str = {
 				referencearchive = strings.dup(testenv.readfile(strings.concat(work,
 					"dep.a")));
 				referencerootwwi = strings.dup(testenv.readfile(strings.concat(work,
-					"__root.wwi")));
+					"main.wwi")));
 				referencerootarchive = strings.dup(testenv.readfile(strings.concat(work,
-					"__root.a")));
+					"main.a")));
 				referencebin = strings.dup(testenv.readfile(bin));
 				referencecompiler = strings.dup(ctrace);
 				referenceassembler = strings.dup(atrace);
@@ -665,9 +665,9 @@ fn writediamond(td: str, reverse: bool) str = {
 				    || !testenv.same(referencearchive, testenv.readfile(strings.concat(
 					work, "dep.a")))
 				    || !testenv.same(referencerootwwi,
-					testenv.readfile(strings.concat(work, "__root.wwi")))
+					testenv.readfile(strings.concat(work, "main.wwi")))
 				    || !testenv.same(referencerootarchive,
-					testenv.readfile(strings.concat(work, "__root.a")))
+					testenv.readfile(strings.concat(work, "main.a")))
 				    || !testenv.same(referencebin, testenv.readfile(bin))
 				    || !testenv.same(referencecompiler, ctrace)
 				    || !testenv.same(referenceassembler, atrace)
@@ -727,7 +727,7 @@ fn writediamond(td: str, reverse: bool) str = {
 		testenv.runcommandenv(cwd, td, strings.concat("empty-library-",
 			tags[si]), av, emptyenv, tmo(), &out);
 		let rootunit: str = testenv.readfile(strings.concat(emptywork,
-			"__root.unit.ww"));
+			"main.unit.ww"));
 		let ctrace: str = testenv.readfile(compilertrace);
 		let atrace: str = testenv.readfile(assemblertrace);
 		let ltrace: str = testenv.readfile(linkertrace);
@@ -881,7 +881,7 @@ fn writediamond(td: str, reverse: bool) str = {
 				" cold build failed: ", out.stderr));
 		};
 
-		let rootunitpath: str = strings.concat(work, "/__root.unit.ww");
+		let rootunitpath: str = strings.concat(work, "/main.unit.ww");
 		let depunitpath: str = strings.concat(work, "/dep.unit.ww");
 		let rootunit: str = testenv.readfile(rootunitpath);
 		let depunit: str = testenv.readfile(depunitpath);
@@ -895,8 +895,8 @@ fn writediamond(td: str, reverse: bool) str = {
 		    || !testenv.exists(strings.concat(work, "/leaf.a"))
 		    || !testenv.exists(strings.concat(work, "/dep.wwi"))
 		    || !testenv.exists(strings.concat(work, "/dep.a"))
-		    || !testenv.exists(strings.concat(work, "/__root.wwi"))
-		    || !testenv.exists(strings.concat(work, "/__root.a"))
+		    || !testenv.exists(strings.concat(work, "/main.wwi"))
+		    || !testenv.exists(strings.concat(work, "/main.a"))
 		    || !testenv.same(testenv.readfile(strings.concat(work,
 			"/.wwtool.ww")), testenv.readfile(copied[si]))
 		    || !testenv.same(testenv.readfile(strings.concat(work,
@@ -921,9 +921,9 @@ fn writediamond(td: str, reverse: bool) str = {
 			"/dep.s.new><", work, "/dep.unit.new>"))
 		    || !testenv.has(coldcompiler, strings.concat(
 			"BEGIN<--entry><-c><--import><dep><", work,
-			"/dep.wwi><-I><", work, "/__root.wwi.new><-o><", work,
-			"/__root.s.new><", work,
-			"/__root.unit.new>"))
+			"/dep.wwi><-I><", work, "/main.wwi.new><-o><", work,
+			"/main.s.new><", work,
+			"/main.unit.new>"))
 		    || testenv.occurrences(coldassembler, "\n") != 3
 		    || !testenv.has(coldassembler, strings.concat(
 			"BEGIN<-o><", work, "/dep.o.new><", work,
@@ -932,7 +932,7 @@ fn writediamond(td: str, reverse: bool) str = {
 		};
 		if (testenv.occurrences(coldlinker, "\n") != 1
 		    || !testenv.has(coldlinker, strings.concat("BEGIN<-o><", bin,
-			"><", work, "/__root.a>"))
+			"><", work, "/main.a>"))
 		    || testenv.pos(coldlinker, strings.concat("<", work,
 			"/dep.a>")) < 0
 		    || testenv.pos(coldlinker, strings.concat("<", work,
@@ -965,7 +965,7 @@ fn writediamond(td: str, reverse: bool) str = {
 		    || testenv.occurrences(changedexportcompiler, strings.concat("<", work,
 			"/dep.unit.new>")) != 2
 		    || testenv.occurrences(changedexportcompiler, strings.concat("<", work,
-			"/__root.unit.new>")) != 1
+			"/main.unit.new>")) != 1
 		    || testenv.occurrences(changedexportcompiler, "\n") != 5
 		    || testenv.occurrences(changedexportassembler, "\n") != 5) {
 			fail("driver-identity", "changed export did not stop at an unchanged importer export");
@@ -999,7 +999,7 @@ fn writediamond(td: str, reverse: bool) str = {
 		    || testenv.occurrences(testenv.readfile(compilertrace), strings.concat(
 			"<", work, "/dep.unit.new>")) != 3
 		    || testenv.occurrences(testenv.readfile(compilertrace), strings.concat(
-			"<", work, "/__root.unit.new>")) != 1
+			"<", work, "/main.unit.new>")) != 1
 		    || testenv.occurrences(testenv.readfile(compilertrace), "\n") != 7
 		    || testenv.occurrences(testenv.readfile(assemblertrace), "\n") != 7
 		    || !testenv.same(coldbin, testenv.readfile(bin))) {
@@ -1024,7 +1024,7 @@ fn writediamond(td: str, reverse: bool) str = {
 		    || testenv.occurrences(changedcompiler, strings.concat("<", work,
 			"/dep.unit.new>")) != 4
 		    || testenv.occurrences(changedcompiler, strings.concat("<", work,
-			"/__root.unit.new>")) != 2
+			"/main.unit.new>")) != 2
 		    || testenv.occurrences(changedcompiler, "\n") != 10
 		    || testenv.occurrences(changedassembler, "\n") != 10
 		    || testenv.occurrences(changedlinker, "\n") != 5) {
diff --git a/test/xmod/direnum_test.ww b/test/xmod/direnum_test.ww
index e1613293..fbf02d5a 100644
--- a/test/xmod/direnum_test.ww
+++ b/test/xmod/direnum_test.ww
@@ -17,7 +17,7 @@ package direnum_test;
 //
 // rootorder — a private rootok/ dir built DIRECTLY (z.ww ORDER-Z
 // value()=17 vs a.ww ORDER-A leading comment + main): build exit 0,
-// the binary exits 17, and the driver's <out>.sepwork/__root.unit.ww
+// the binary exits 17, and the driver's <out>.sepwork/rootok.unit.ww
 // stores ORDER-A strictly before ORDER-Z (byte-sorted deterministic
 // source order); the two stages' units are byte-identical.
 //
@@ -143,7 +143,7 @@ fn rejectpair(label: str, td: str, target: str, needle: str) void = {
 			fail("rootorder", strings.concat(drvs[s], " exit != 17"));
 		};
 		units[s] = testenv.readfile(strings.concat(out,
-			".sepwork/__root.unit.ww"));
+			".sepwork/rootok.unit.ww"));
 		let a: i32 = testenv.pos(units[s], "ORDER-A");
 		let z: i32 = testenv.pos(units[s], "ORDER-Z");
 		if (a < 0 || z < 0 || a >= z) {
@@ -153,7 +153,7 @@ fn rejectpair(label: str, td: str, target: str, needle: str) void = {
 		s += 1;
 	};
 	if (!testenv.same(units[0], units[1])) {
-		fail("rootorder", "C/WW __root.unit.ww differ");
+		fail("rootorder", "C/WW rootok.unit.ww differ");
 	};
 	testenv.clean(td);
 };