diff --git a/test/wcc/809_idx_structlit_store.c b/test/wcc/809_idx_structlit_store.c
index cd941bd2..f0b4018e 100644
--- a/test/wcc/809_idx_structlit_store.c
+++ b/test/wcc/809_idx_structlit_store.c
@@ -402,80 +402,82 @@ run_driver(const char *driver, const struct row *r, int i)
 	return got;
 }
 
-/* asm_byte_identical — generate .s via the driver, once with cstage's
- * w6c and once with the wwstage compiler (WW_W6C override; w6a/w6l stay
- * cstage — only the .s is compared), and diff. The driver route — not a
- * bare `w6c src.ww` — so importing rows (callee_capture pulls strings)
- * resolve; the driver leaves src.s NEXT TO the source. Pre-fix the asm
- * was byte-identically WRONG (both stages dropped the fill), so these
- * rows pin only that the converged fix stays symmetric; the runtime
- * rows above carry correctness. */
+/* asm_byte_identical — #103 sep layout: the driver flip moves build
+ * artifacts from next-to-source <stem>.s to a <stem>.sepwork/ scratch
+ * dir, so drive `ww build --sep -o <stem>` twice — once with cstage's w6c
+ * and once with the wwstage compiler (WW_W6C override; w6a/w6l stay
+ * cstage — only the .s is compared) — then concat each build's
+ * per-package .sepwork asm (sorted glob, identical package set:
+ * callee_capture pulls strings, so this is multi-package) and diff. The
+ * driver route — not a bare `w6c src.ww` — so importing rows resolve;
+ * --sep is flip-invariant (green pre- and post-flip). WW_PKGCACHE pins
+ * the package cache to the scratch dir so out/.pkgcache stays untouched.
+ * Pre-fix the asm was byte-identically WRONG (both stages dropped the
+ * fill), so these rows pin only that the converged fix stays symmetric;
+ * the runtime rows above carry correctness. */
 static int
 asm_byte_identical(const char *bin, const struct row *r, int i)
 {
-	char src[64], srcs[64], comb[80], srco[64], tmpdir[64];
-	char cs[64], ws[64], cmd[1024];
-	snprintf(src,    sizeof src,    "/tmp/isls_asm_%d_%d.ww", getpid(), i);
-	snprintf(srcs,   sizeof srcs,   "/tmp/isls_asm_%d_%d.s", getpid(), i);
-	snprintf(srco,   sizeof srco,   "/tmp/isls_asm_%d_%d.o", getpid(), i);
-	snprintf(comb,   sizeof comb,   "/tmp/isls_asm_%d_%d.combined.ww",
-	    getpid(), i);
+	char src[96], tmpdir[64], outc[128], outw[128];
+	char cs[96], ws[96], cmd[1024];
 	snprintf(tmpdir, sizeof tmpdir, "/tmp/isls_asm_%d_d_%d", getpid(), i);
-	snprintf(cs,     sizeof cs,     "/tmp/isls_asm_%d_%d_c.s", getpid(), i);
-	snprintf(ws,     sizeof ws,     "/tmp/isls_asm_%d_%d_w.s", getpid(), i);
+	snprintf(src,    sizeof src,    "%s/main809.ww", tmpdir);
+	snprintf(outc,   sizeof outc,   "%s/main809c", tmpdir);
+	snprintf(outw,   sizeof outw,   "%s/main809w", tmpdir);
+	snprintf(cs,     sizeof cs,     "%s/all_cs.s", tmpdir);
+	snprintf(ws,     sizeof ws,     "%s/all_ww.s", tmpdir);
 
+	mkdir(tmpdir, 0755);
 	FILE *f = fopen(src, "wb");
 	if (!f) return -1;
 	fputs(r->src, f);
 	fclose(f);
-	mkdir(tmpdir, 0755);
 
-	snprintf(cmd, sizeof cmd, "cd %s && %s/ww build %s 2>/dev/null",
-	    tmpdir, bin, src);
-	if (runwait(cmd) != 0 || rename(srcs, cs) != 0) {
-		fprintf(stderr, "row[%s]: cstage driver .s failed\n",
-		    r->label);
-		unlink(src); unlink(srco); unlink(comb); rmdir(tmpdir);
-		return -1;
-	}
-	snprintf(cmd, sizeof cmd,
-	    "cd %s && WW_W6C=%s/w6c_ww %s/ww build %s 2>/dev/null",
-	    tmpdir, bin, bin, src);
-	if (runwait(cmd) != 0 || rename(srcs, ws) != 0) {
-		fprintf(stderr, "row[%s]: wwstage driver .s failed\n",
-		    r->label);
-		unlink(src); unlink(srco); unlink(comb); unlink(cs);
-		rmdir(tmpdir);
-		return -1;
-	}
-
-	FILE *fc = fopen(cs, "rb");
-	FILE *fw = fopen(ws, "rb");
 	int rc = 0;
-	if (!fc || !fw) {
+	snprintf(cmd, sizeof cmd,
+	    "cd %s && WW_PKGCACHE=%s/pkgc_c %s/ww build --sep -o %s %s 2>/dev/null",
+	    tmpdir, tmpdir, bin, outc, src);
+	if (runwait(cmd) != 0) {
+		fprintf(stderr, "row[%s]: cstage sep build failed\n", r->label);
 		rc = -1;
-	} else {
-		for (;;) {
-			int a = fgetc(fc);
-			int b = fgetc(fw);
-			if (a != b) { rc = -1; break; }
-			if (a == EOF) break;
+	}
+	if (rc == 0) {
+		snprintf(cmd, sizeof cmd,
+		    "cd %s && WW_PKGCACHE=%s/pkgc_w WW_W6C=%s/w6c_ww "
+		    "%s/ww build --sep -o %s %s 2>/dev/null",
+		    tmpdir, tmpdir, bin, bin, outw, src);
+		if (runwait(cmd) != 0) {
+			fprintf(stderr, "row[%s]: wwstage sep build failed\n",
+			    r->label);
+			rc = -1;
 		}
 	}
-	if (fc) fclose(fc);
-	if (fw) fclose(fw);
-	if (rc != 0)
-		fprintf(stderr, "row[%s]: cstage vs wwstage asm differs\n",
-		    r->label);
-	{
-		char outbin[128];
-		snprintf(outbin, sizeof outbin, "%s/isls_asm_%d_%d",
-		    tmpdir, getpid(), i);
-		unlink(outbin);
+	if (rc == 0) {
+		snprintf(cmd, sizeof cmd, "cat %s.sepwork/*.s > %s 2>/dev/null",
+		    outc, cs); if (system(cmd)) {}
+		snprintf(cmd, sizeof cmd, "cat %s.sepwork/*.s > %s 2>/dev/null",
+		    outw, ws); if (system(cmd)) {}
+		FILE *fc = fopen(cs, "rb");
+		FILE *fw = fopen(ws, "rb");
+		if (!fc || !fw) {
+			rc = -1;
+		} else {
+			for (;;) {
+				int a = fgetc(fc);
+				int b = fgetc(fw);
+				if (a != b) { rc = -1; break; }
+				if (a == EOF) break;
+			}
+		}
+		if (fc) fclose(fc);
+		if (fw) fclose(fw);
+		if (rc != 0)
+			fprintf(stderr,
+			    "row[%s]: cstage vs wwstage asm differs\n",
+			    r->label);
 	}
-	unlink(src); unlink(srco); unlink(comb);
-	unlink(cs); unlink(ws);
-	rmdir(tmpdir);
+	snprintf(cmd, sizeof cmd, "rm -rf %s", tmpdir);
+	if (system(cmd)) {}
 	return rc;
 }