diff --git a/test/wcc/950_selfcheck.c b/test/wcc/950_selfcheck.c
index 300166fb..f60ec55c 100644
--- a/test/wcc/950_selfcheck.c
+++ b/test/wcc/950_selfcheck.c
@@ -9,32 +9,48 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <errno.h>
 #include <unistd.h>
 #include <sys/wait.h>
 #include "wwtestpkg.h"
 
 static int
-runcap(const char *cmd, char **outerr, size_t *outlen)
+runcap(const char *cmd, char **outerr, size_t *outlen, int *outrc)
 {
 	char tmp[256];
 	snprintf(tmp, sizeof tmp, "/tmp/wwd_sc_%d", getpid());
 	char full[2048];
 	snprintf(full, sizeof full, "%s 2>%s 1>/dev/null", cmd, tmp);
+	int ret = -1;
+	FILE *f = NULL;
+	char *b = NULL;
+	long n = 0;
 	int rc = system(full);
-	FILE *f = fopen(tmp, "rb");
-	if (!f) { unlink(tmp); return -1; }
-	fseek(f, 0, SEEK_END);
-	long n = ftell(f);
-	fseek(f, 0, SEEK_SET);
-	char *b = malloc((size_t)n + 1);
-	if (!b) { fclose(f); unlink(tmp); return -1; }
-	if (fread(b, 1, (size_t)n, f) != (size_t)n) {
-		free(b); fclose(f); unlink(tmp); return -1;
-	}
+	if (rc == -1 || !WIFEXITED(rc)) goto cleanup;
+	f = fopen(tmp, "rb");
+	if (!f) { perror(tmp); goto cleanup; }
+	if (fseek(f, 0, SEEK_END) != 0) { perror(tmp); goto cleanup; }
+	n = ftell(f);
+	if (n < 0) { perror(tmp); goto cleanup; }
+	if (fseek(f, 0, SEEK_SET) != 0) { perror(tmp); goto cleanup; }
+	b = malloc((size_t)n + 1);
+	if (!b) goto cleanup;
+	if (fread(b, 1, (size_t)n, f) != (size_t)n) goto cleanup;
 	b[n] = '\0';
-	fclose(f); unlink(tmp);
-	*outerr = b; *outlen = (size_t)n;
-	(void)rc;
+	ret = 0;
+
+cleanup:
+	/* the shell may never have created tmp (fork failure). */
+	if (f) fclose(f);
+	if (unlink(tmp) != 0 && errno != ENOENT) {
+		perror(tmp);
+		ret = -1;
+	}
+	if (ret != 0) {
+		free(b);
+		return -1;
+	}
+	*outerr = b; *outlen = (size_t)n; *outrc = WEXITSTATUS(rc);
 	return 0;
 }
 
@@ -44,7 +60,15 @@ writefile(const char *path, const char *src)
 	FILE *f = fopen(path, "wb");
 	if (!f) return -1;
 	wwtest_fputs(src, f);
-	fclose(f);
+	/* wwtest_fputs is void; ferror + fclose's flush surface a short
+	 * write (ENOSPC) that would otherwise compile a truncated fixture. */
+	int werr = ferror(f) != 0;
+	if (fclose(f) != 0 || werr) {
+		perror(path);
+		if (unlink(path) != 0 && errno != ENOENT)
+			perror(path);
+		return -1;
+	}
 	return 0;
 }
 
@@ -168,9 +192,15 @@ main(void)
 	if (!bin) bin = "out/bin";
 	char wwdump[2048];
 	snprintf(wwdump, sizeof wwdump, "%s/wwdump_ww", bin);
+	/* bootstrap gate: a missing selfhost checker must FAIL, not skip. */
+	if (access(wwdump, X_OK) != 0) {
+		fprintf(stderr, "selfcheck: %s missing or not executable\n",
+		    wwdump);
+		return 1;
+	}
 
 	int n = sizeof rows / sizeof rows[0];
-	int fail = 0;
+	int fail = 0, cleanfail = 0;
 	for (int i = 0; i < n; i++) {
 		char path[64];
 		snprintf(path, sizeof path, "/tmp/wwd_sc_%d_%d.ww", getpid(), i);
@@ -178,7 +208,12 @@ main(void)
 		char cmd[2048];
 		snprintf(cmd, sizeof cmd, "%s -r %s", wwdump, path);
 		char *err = NULL; size_t elen = 0;
-		runcap(cmd, &err, &elen);
+		int xrc = -1;
+		if (runcap(cmd, &err, &elen, &xrc) != 0) {
+			fprintf(stderr, "row %d: capture failed\n", i);
+			fail++;
+			goto rowcleanup;
+		}
 		const char *want = rows[i].expect;
 		int got_match = (err && want && strstr(err, want) != NULL);
 		int expected_no_err = (want == NULL);
@@ -201,7 +236,9 @@ main(void)
 		err_present = err_present || (err && strstr(err,
 		    "return: not assignable") != NULL);
 		int ok;
-		if (expected_no_err) ok = !err_present;
+		/* a checker that dies with empty stderr must not pass a
+		 * no-error row: require a clean exit too. */
+		if (expected_no_err) ok = !err_present && xrc == 0;
 		else                 ok = got_match;
 		if (!ok) {
 			fprintf(stderr,
@@ -209,13 +246,21 @@ main(void)
 			    i, want ? want : "(no error)", err ? err : "(empty)");
 			fail++;
 		}
+rowcleanup:
 		free(err);
-		unlink(path);
+		if (unlink(path) != 0 && errno != ENOENT) {
+			perror(path);
+			cleanfail = 1;
+		}
 	}
 	if (fail) {
 		fprintf(stderr, "%d/%d selfcheck rows failed\n", fail, n);
 		return 1;
 	}
+	if (cleanfail) {
+		fprintf(stderr, "selfcheck: cleanup failed\n");
+		return 1;
+	}
 	printf("selfcheck: %d/%d ok\n", n, n);
 	return 0;
 }
diff --git a/test/wcc/991_w6a_ww.c b/test/wcc/991_w6a_ww.c
index 0b34e0b3..09a42bd4 100644
--- a/test/wcc/991_w6a_ww.c
+++ b/test/wcc/991_w6a_ww.c
@@ -14,6 +14,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <errno.h>
 #include <unistd.h>
 #include <glob.h>
 #include <sys/wait.h>
@@ -63,34 +64,47 @@ static int
 diff_one(const char *bin, const char *src)
 {
 	char co[64], wo[64], cmd[2048];
+	char *bc = NULL, *bw = NULL;
+	size_t nc = 0, nw = 0;
+	int rc = -1;
 	snprintf(co, sizeof co, "/tmp/wwa_%d_c.o", getpid());
 	snprintf(wo, sizeof wo, "/tmp/wwa_%d_w.o", getpid());
 
 	snprintf(cmd, sizeof cmd, "timeout 180 %s/w6a -o %s %s 2>/dev/null", bin, co, src);
 	if (runwait(cmd) != 0) {
 		fprintf(stderr, "w6a_ww FAIL: C w6a errored on %s\n", src);
-		unlink(co);
-		return -1;
+		goto cleanup;
 	}
 	snprintf(cmd, sizeof cmd, "timeout 180 %s/w6a_ww -o %s %s 2>/dev/null", bin, wo, src);
 	if (runwait(cmd) != 0) {
 		fprintf(stderr, "w6a_ww FAIL: ww w6a errored on %s\n", src);
-		unlink(co); unlink(wo);
-		return -1;
+		goto cleanup;
 	}
-	char *bc = NULL, *bw = NULL;
-	size_t nc = 0, nw = 0;
-	int rc = 0;
 	if (slurp(co, &bc, &nc) < 0 || slurp(wo, &bw, &nw) < 0) {
 		fprintf(stderr, "w6a_ww FAIL: cannot read .o for %s\n", src);
-		rc = -1;
+	} else if (nc == 0) {
+		fprintf(stderr, "w6a_ww FAIL: empty .o for %s\n", src);
 	} else if (nc != nw || memcmp(bc, bw, nc) != 0) {
 		fprintf(stderr, "w6a_ww FAIL: %s — C %zu vs ww %zu bytes\n",
 		    src, nc, nw);
-		rc = -1;
-	}
+	} else
+		rc = 0;
+
+cleanup:
 	free(bc); free(bw);
-	unlink(co); unlink(wo);
+	/* co/wo are reused across corpus files; a stale .o left behind
+	 * would be slurped as a later file's output. */
+	int cleanfail = 0;
+	if (unlink(co) != 0 && errno != ENOENT) {
+		perror(co);
+		cleanfail = 1;
+	}
+	if (unlink(wo) != 0 && errno != ENOENT) {
+		perror(wo);
+		cleanfail = 1;
+	}
+	if (cleanfail && rc == 0)
+		rc = -1;
 	return rc;
 }
 
@@ -112,6 +126,9 @@ main(void)
 	 * intentionally contains package main plus legacy file-import packages,
 	 * so it is not a directory-package root. */
 	char stem[256], cmd[4096];
+	int fail = 0;
+	int n = 0;
+	int gen = 0;
 	snprintf(stem, sizeof stem, "/tmp/wwa_%d_sh", getpid());
 	snprintf(cmd, sizeof cmd,
 	    "timeout 400 %s/ww build -o %s "
@@ -120,7 +137,9 @@ main(void)
 	if (runwait(cmd) != 0) {
 		fprintf(stderr,
 		    "w6a_ww FAIL: cannot sep-build selfhost/cmd/w6a/main.ww\n");
-		return 1;
+		/* a failed build can leave a partial stem/.sepwork tree. */
+		fail = 1;
+		goto cleanup;
 	}
 
 	/* hand-written runtime — small, covers MOVQ/LEAQ/CALL/SYSCALL/RET;
@@ -129,8 +148,6 @@ main(void)
 		"rt/start.s", "rt/syscall.s", "rt/abort.s",
 		"rt/alloc.s", "rt/streq.s", NULL,
 	};
-	int fail = 0;
-	int n = 0;
 	for (int i = 0; rtfiles[i]; i++) {
 		char p[2048];
 		snprintf(p, sizeof p, "%s/%s", cwd, rtfiles[i]);
@@ -152,17 +169,32 @@ main(void)
 			if (sz <= 0) continue;
 			if (diff_one(bin, g.gl_pathv[i]) != 0) fail++;
 			n++;
+			gen++;
 		}
 		globfree(&g);
 	}
+	/* the PASS banner claims generated-asm coverage; an empty glob
+	 * (or all-empty units) must not go green on the rt corpus alone. */
+	if (gen == 0) {
+		fprintf(stderr,
+		    "w6a_ww FAIL: no non-empty generated .s under %s.sepwork\n",
+		    stem);
+		fail++;
+	}
 
+cleanup:
 	snprintf(cmd, sizeof cmd, "rm -rf %s.sepwork %s", stem, stem);
-	if (system(cmd)) {}
+	int cleanfail = runwait(cmd) != 0;
+	if (cleanfail)
+		fprintf(stderr, "w6a_ww: cleanup of %s{,.sepwork} failed\n",
+		    stem);
 
 	if (fail) {
 		fprintf(stderr, "w6a_ww: %d/%d diff(s) failed\n", fail, n);
 		return 1;
 	}
+	if (cleanfail)
+		return 1;
 	printf("w6a_ww: byte-identical to C w6a on %d corpus files "
 	    "(rt/*.s + selfhost/cmd/w6a sep-built .s)\n", n);
 	return 0;
diff --git a/test/wcc/992_w6l_ww.c b/test/wcc/992_w6l_ww.c
index 59b415f0..1991825b 100644
--- a/test/wcc/992_w6l_ww.c
+++ b/test/wcc/992_w6l_ww.c
@@ -12,6 +12,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <errno.h>
 #include <unistd.h>
 #include <sys/wait.h>
 
@@ -68,11 +69,15 @@ slurp(const char *path, char **outbuf, size_t *outlen)
  * + reverse-topo .a resolution — a stronger link than the old single
  * main.o. */
 static int
-build_and_diff(const char *bin, const char *cwd, const char *tool)
+build_and_diff(const char *bin, const char *cwd, const char *tool, int id)
 {
 	char cstem[256], wstem[256], cmd[4096];
-	snprintf(cstem, sizeof cstem, "/tmp/wwl_%d_c", getpid());
-	snprintf(wstem, sizeof wstem, "/tmp/wwl_%d_w", getpid());
+	snprintf(cstem, sizeof cstem, "/tmp/wwl_%d_%d_c", getpid(), id);
+	snprintf(wstem, sizeof wstem, "/tmp/wwl_%d_%d_w", getpid(), id);
+
+	char *bc = NULL, *bw = NULL;
+	size_t nc = 0, nw = 0;
+	int rc = 0;
 
 	snprintf(cmd, sizeof cmd,
 	    "timeout 300 %s/ww build -o %s "
@@ -80,7 +85,8 @@ build_and_diff(const char *bin, const char *cwd, const char *tool)
 	    bin, cstem, cwd, tool);
 	if (runwait(cmd) != 0) {
 		fprintf(stderr, "w6l_ww FAIL: C-link sep-build of %s\n", tool);
-		return -1;
+		rc = -1;
+		goto cleanup;
 	}
 	snprintf(cmd, sizeof cmd,
 	    "WW_W6L=%s/w6l_ww timeout 300 %s/ww build "
@@ -88,25 +94,43 @@ build_and_diff(const char *bin, const char *cwd, const char *tool)
 	    bin, bin, wstem, cwd, tool);
 	if (runwait(cmd) != 0) {
 		fprintf(stderr, "w6l_ww FAIL: ww-link sep-build of %s\n", tool);
-		snprintf(cmd, sizeof cmd, "rm -rf %s %s.sepwork", cstem, cstem);
-		if (system(cmd)) {}
-		return -1;
+		rc = -1;
+		goto cleanup;
 	}
-	char *bc = NULL, *bw = NULL;
-	size_t nc = 0, nw = 0;
-	int rc = 0;
 	if (slurp(cstem, &bc, &nc) < 0 || slurp(wstem, &bw, &nw) < 0) {
 		fprintf(stderr, "w6l_ww FAIL: cannot read output for %s\n", tool);
 		rc = -1;
+	} else if (nc == 0) {
+		fprintf(stderr, "w6l_ww FAIL: empty output for %s\n", tool);
+		rc = -1;
 	} else if (nc != nw || memcmp(bc, bw, nc) != 0) {
 		fprintf(stderr, "w6l_ww FAIL: %s — C %zu vs ww %zu bytes\n",
 		    tool, nc, nw);
 		rc = -1;
 	}
 	free(bc); free(bw);
-	snprintf(cmd, sizeof cmd, "rm -rf %s %s %s.sepwork %s.sepwork",
-	    cstem, wstem, cstem, wstem);
-	if (system(cmd)) {}
+
+cleanup:
+	/* `ww build` retains these exact caller-owned scratch trees; a
+	 * never-created pid+id-keyed path is harmless to remove, so one
+	 * funnel covers every exit. */
+	int cleanfail = 0;
+	if (unlink(cstem) != 0 && errno != ENOENT) {
+		perror(cstem);
+		cleanfail = 1;
+	}
+	if (unlink(wstem) != 0 && errno != ENOENT) {
+		perror(wstem);
+		cleanfail = 1;
+	}
+	snprintf(cmd, sizeof cmd, "rm -rf %s.sepwork %s.sepwork",
+	    cstem, wstem);
+	if (runwait(cmd) != 0)
+		cleanfail = 1;
+	if (cleanfail)
+		fprintf(stderr, "w6l_ww: cleanup failed for %s\n", tool);
+	if (cleanfail && rc == 0)
+		rc = -1;
 	return rc;
 }
 
@@ -130,7 +154,7 @@ main(void)
 	int fail = 0;
 	int n = 0;
 	for (int i = 0; tools[i]; i++) {
-		if (build_and_diff(bin, cwd, tools[i]) != 0) fail++;
+		if (build_and_diff(bin, cwd, tools[i], i) != 0) fail++;
 		n++;
 	}
 	if (fail) {
diff --git a/test/wcc/993_ww_ww.c b/test/wcc/993_ww_ww.c
index ba86a399..1b0ec1e1 100644
--- a/test/wcc/993_ww_ww.c
+++ b/test/wcc/993_ww_ww.c
@@ -14,6 +14,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <errno.h>
 #include <unistd.h>
 #include <sys/stat.h>
 #include <sys/wait.h>
@@ -48,11 +49,14 @@ slurp_eq(const char *a, const char *b)
 	FILE *fb = fopen(b, "rb");
 	if (!fa || !fb) { if (fa) fclose(fa); if (fb) fclose(fb); return -1; }
 	int rc = 0;
+	int any = 0;
 	for (;;) {
 		int ca = fgetc(fa);
 		int cb = fgetc(fb);
 		if (ca != cb) { rc = -1; break; }
-		if (ca == EOF) break;
+		/* a produced executable can never be legitimately empty. */
+		if (ca == EOF) { if (!any) rc = -1; break; }
+		any = 1;
 	}
 	fclose(fa); fclose(fb);
 	return rc;
@@ -92,29 +96,35 @@ diff_one(const char *bin, const char *cwd, const char *label,
 	snprintf(dw, sizeof dw, "/tmp/ww_d_%d_w", getpid());
 
 	char cmd[256];
+	int rc = -1;
 	snprintf(cmd, sizeof cmd, "rm -rf %s %s && mkdir -p %s %s", dc, dw, dc, dw);
-	if (runwait(cmd) != 0) return -1;
+	if (runwait(cmd) != 0) goto cleanup;
 
 	if (build_via(bin, "ww",    src, dc, incs, out_basename) != 0) {
 		fprintf(stderr, "ww_ww FAIL: C ww errored on %s\n", label);
-		return -1;
+		goto cleanup;
 	}
 	if (build_via(bin, "ww_ww", src, dw, incs, out_basename) != 0) {
 		fprintf(stderr, "ww_ww FAIL: ww ww errored on %s\n", label);
-		return -1;
+		goto cleanup;
 	}
 
 	char co[1024], wo[1024];
 	snprintf(co, sizeof co, "%s/%s", dc, out_basename);
 	snprintf(wo, sizeof wo, "%s/%s", dw, out_basename);
 
-	int rc = 0;
-	if (slurp_eq(co, wo) != 0) {
+	if (slurp_eq(co, wo) != 0)
 		fprintf(stderr, "ww_ww FAIL: %s — driver outputs differ\n", label);
-		rc = -1;
-	}
+	else
+		rc = 0;
+
+cleanup:
+	/* `ww build` retains the caller-owned .sepwork tree inside the
+	 * workdir; rm -rf of the exact pid-keyed pair covers it, and is
+	 * safe even after a partial mkdir. */
 	snprintf(cmd, sizeof cmd, "rm -rf %s %s", dc, dw);
-	runwait(cmd);
+	if (runwait(cmd) != 0 && rc == 0)
+		rc = -1;
 	(void)cwd;
 	return rc;
 }
@@ -132,12 +142,21 @@ run_exit_code(const char *bin, const char *driver, int code)
 	if (!f) return -1;
 	fprintf(f, "package main;\nexport fn main() i32 = {\n\treturn %d;\n};\n",
 	    code);
-	fclose(f);
+	if (fclose(f) != 0) {
+		perror(src);
+		if (unlink(src) != 0 && errno != ENOENT)
+			perror(src);
+		return -1;
+	}
 
 	char cmd[256];
 	snprintf(cmd, sizeof cmd, "%s/%s run %s 2>/dev/null", bin, driver, src);
 	int rc = runwait(cmd);
-	unlink(src);
+	if (unlink(src) != 0 && errno != ENOENT) {
+		perror(src);
+		if (rc == code)
+			rc = -1;
+	}
 	return rc;
 }
 
@@ -152,14 +171,28 @@ run_build_fail(const char *bin, const char *driver)
 	char src[64];
 	snprintf(src, sizeof src, "/tmp/ww_badbuild_%d.ww", getpid());
 	FILE *f = fopen(src, "w");
-	if (!f) return -1;
+	if (!f) {
+		perror(src);
+		return -1;
+	}
 	wwtest_fputs("export fn main() i32 = {\n\treturn 1\n", f);	/* no ; no } */
-	fclose(f);
+	if (fclose(f) != 0) {
+		perror(src);
+		if (unlink(src) != 0 && errno != ENOENT)
+			perror(src);
+		return -1;
+	}
 
 	char cmd[256];
 	snprintf(cmd, sizeof cmd, "%s/%s run %s 2>/dev/null", bin, driver, src);
 	int rc = runwait(cmd);
-	unlink(src);
+	if (unlink(src) != 0 && errno != ENOENT) {
+		perror(src);
+		/* cleanup failure maps onto the -1 sentinel the caller rejects;
+		 * a real rc==0 (driver failed to fail) keeps its diagnostic. */
+		if (rc != 0)
+			rc = -1;
+	}
 	return rc;
 }
 
@@ -173,13 +206,21 @@ run_missing_pkg(const char *bin, const char *driver)
 {
 	char tmpdir[80], src[160], errf[160], outbin[160], rmcmd[200];
 	snprintf(tmpdir, sizeof tmpdir, "/tmp/ww_mp_%s_%d", driver, getpid());
-	mkdir(tmpdir, 0755);
+	if (mkdir(tmpdir, 0755) != 0) {
+		perror(tmpdir);
+		return 1;
+	}
 	snprintf(src,    sizeof src,    "%s/mp.ww", tmpdir);
 	snprintf(errf,   sizeof errf,   "%s/mp.err", tmpdir);
 	snprintf(outbin, sizeof outbin, "%s/mp", tmpdir);
 	snprintf(rmcmd,  sizeof rmcmd,  "rm -rf %s", tmpdir);
 	FILE *f = fopen(src, "w");
-	if (!f) { runwait(rmcmd); return 1; }
+	if (!f) {
+		perror(src);
+		if (runwait(rmcmd) != 0)
+			fprintf(stderr, "ww_ww: cleanup of %s failed\n", tmpdir);
+		return 1;
+	}
 	wwtest_fputs("import nosuchpkg;\nexport fn main() i32 = { return 0; };\n", f);
 	fclose(f);
 
@@ -200,12 +241,16 @@ run_missing_pkg(const char *bin, const char *driver)
 		buf[n] = '\0';
 		found = strstr(buf, "cannot find package nosuchpkg") != NULL;
 	}
-	runwait(rmcmd);
+	int cleanfail = runwait(rmcmd) != 0;
 	if (rc == 0 || !found) {
 		fprintf(stderr, "ww_ww FAIL: %s missing-pkg rc=%d found=%d "
 		    "(want nonzero + 'cannot find package')\n", driver, rc, found);
 		return 1;
 	}
+	if (cleanfail) {
+		fprintf(stderr, "ww_ww: cleanup of %s failed\n", tmpdir);
+		return 1;
+	}
 	return 0;
 }
 
@@ -232,7 +277,12 @@ main(void)
 		    "\tos.write(1, \"hi\\n\".ptr, 3u64);\n"
 		    "\treturn 0;\n"
 		    "};\n", f);
-		fclose(f);
+		if (fclose(f) != 0) {
+			perror(hello_src);
+			if (unlink(hello_src) != 0 && errno != ENOENT)
+				perror(hello_src);
+			return 1;
+		}
 	}
 
 	struct {
@@ -260,13 +310,17 @@ main(void)
 
 	int fail = 0;
 	int n = 0;
+	int cleanfail = 0;
 	for (int i = 0; cases[i].label; i++) {
 		if (diff_one(bin, cwd, cases[i].label, cases[i].src,
 		    cases[i].out, cases[i].incs) != 0)
 			fail++;
 		n++;
 	}
-	unlink(hello_src);
+	if (unlink(hello_src) != 0 && errno != ENOENT) {
+		perror(hello_src);
+		cleanfail = 1;
+	}
 
 	/* #16: `ww_ww run` must propagate the child program's real exit code.
 	 * Table-driven; the non-zero rows fail under the old collapse-to-1.
@@ -296,7 +350,9 @@ main(void)
 	 * failure (non-zero), and both drivers must agree. */
 	int cbad = run_build_fail(bin, "ww");
 	int wbad = run_build_fail(bin, "ww_ww");
-	if (cbad == 0 || wbad == 0 || cbad != wbad) {
+	/* <= 0 rejects the -1 staging/cleanup sentinel: equal sentinels must
+	 * not pass as build-fail parity when neither driver ever ran. */
+	if (cbad <= 0 || wbad <= 0 || cbad != wbad) {
 		fprintf(stderr, "ww_ww FAIL: build-fail exit C ww=%d ww_ww=%d "
 		    "(want equal and non-zero)\n", cbad, wbad);
 		rcfail++;
@@ -307,7 +363,7 @@ main(void)
 	rcfail += run_missing_pkg(bin, "ww");
 	rcfail += run_missing_pkg(bin, "ww_ww");
 
-	if (fail || rcfail) {
+	if (fail || rcfail || cleanfail) {
 		fprintf(stderr, "ww_ww: %d/%d diff(s) failed, %d exit-code "
 		    "row(s) failed\n", fail, n, rcfail);
 		return 1;
diff --git a/test/wcc/994_w6c_ww.c b/test/wcc/994_w6c_ww.c
index dd6598c1..ed4b9d3f 100644
--- a/test/wcc/994_w6c_ww.c
+++ b/test/wcc/994_w6c_ww.c
@@ -15,6 +15,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <errno.h>
 #include <unistd.h>
 #include <sys/wait.h>
 #include <dirent.h>
@@ -65,6 +66,9 @@ static int
 diff_one(const char *bin, const char *label, const char *src)
 {
 	char ws[64], cs[64], cmd[2048];
+	char *bw = NULL, *bc = NULL;
+	size_t nw = 0, nc = 0;
+	int rc = -1;
 	snprintf(ws, sizeof ws, "/tmp/wwc6_%d_w.s", getpid());
 	snprintf(cs, sizeof cs, "/tmp/wwc6_%d_c.s", getpid());
 
@@ -72,28 +76,37 @@ diff_one(const char *bin, const char *label, const char *src)
 	    bin, src, ws);
 	if (runwait(cmd) != 0) {
 		fprintf(stderr, "w6c_ww FAIL: wwdump_ww -c errored on %s\n", label);
-		unlink(ws);
-		return -1;
+		goto cleanup;
 	}
 	snprintf(cmd, sizeof cmd, "timeout 180 %s/w6c_ww -o %s %s 2>/dev/null", bin, cs, src);
 	if (runwait(cmd) != 0) {
 		fprintf(stderr, "w6c_ww FAIL: w6c_ww errored on %s\n", label);
-		unlink(ws); unlink(cs);
-		return -1;
+		goto cleanup;
 	}
-	char *bw = NULL, *bc = NULL;
-	size_t nw = 0, nc = 0;
-	int rc = 0;
 	if (slurp(ws, &bw, &nw) < 0 || slurp(cs, &bc, &nc) < 0) {
 		fprintf(stderr, "w6c_ww FAIL: cannot read .s for %s\n", label);
-		rc = -1;
+	} else if (nw == 0) {
+		fprintf(stderr, "w6c_ww FAIL: empty .s for %s\n", label);
 	} else if (nw != nc || memcmp(bw, bc, nw) != 0) {
 		fprintf(stderr, "w6c_ww FAIL: %s — wwdump_ww %zu vs w6c_ww %zu bytes\n",
 		    label, nw, nc);
-		rc = -1;
-	}
+	} else
+		rc = 0;
+
+cleanup:
 	free(bw); free(bc);
-	unlink(ws); unlink(cs);
+	/* cs may not exist when w6c_ww never ran or died before -o. */
+	int cleanfail = 0;
+	if (unlink(ws) != 0 && errno != ENOENT) {
+		perror(ws);
+		cleanfail = 1;
+	}
+	if (unlink(cs) != 0 && errno != ENOENT) {
+		perror(cs);
+		cleanfail = 1;
+	}
+	if (cleanfail && rc == 0)
+		rc = -1;
 	return rc;
 }
 
@@ -103,7 +116,15 @@ write_file(const char *path, const char *content)
 	FILE *f = fopen(path, "wb");
 	if (!f) return -1;
 	wwtest_fputs(content, f);
-	fclose(f);
+	/* wwtest_fputs is void; ferror is the only short-write witness. */
+	int bad = ferror(f);
+	if (fclose(f) != 0) bad = 1;
+	if (bad) {
+		perror(path);
+		if (unlink(path) != 0 && errno != ENOENT)
+			perror(path);
+		return -1;
+	}
 	return 0;
 }
 
@@ -282,7 +303,10 @@ main(void)
 		snprintf(src, sizeof src, "/tmp/wwc6_%d_%d.ww", getpid(), i);
 		if (write_file(src, progs[i].src) != 0) { fail++; n++; continue; }
 		if (diff_one(bin, progs[i].label, src) != 0) fail++;
-		unlink(src);
+		if (unlink(src) != 0 && errno != ENOENT) {
+			perror(src);
+			fail++;
+		}
 		n++;
 	}
 
@@ -321,7 +345,14 @@ main(void)
 			    bad[i].label);
 			fail++;
 		}
-		unlink(src); unlink(s);
+		if (unlink(src) != 0 && errno != ENOENT) {
+			perror(src);
+			fail++;
+		}
+		if (unlink(s) != 0 && errno != ENOENT) {
+			perror(s);
+			fail++;
+		}
 		n++;
 	}
 
@@ -371,7 +402,11 @@ main(void)
 		for (int s = 0; s < 2; s++) {
 			snprintf(cmd, sizeof cmd, "rm -rf %s %s.sepwork %s.cache",
 			    stg[s].prog, stg[s].prog, stg[s].prog);
-			runwait(cmd);
+			if (runwait(cmd) != 0) {
+				fprintf(stderr, "Tier-C: cleanup %s failed\n",
+				    stg[s].prog);
+				fail++;
+			}
 		}
 	}
 
diff --git a/test/wcc/995_self_rebuild.c b/test/wcc/995_self_rebuild.c
index 2e072c8b..d1a81f22 100644
--- a/test/wcc/995_self_rebuild.c
+++ b/test/wcc/995_self_rebuild.c
@@ -18,6 +18,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <sys/stat.h>
 #include <sys/wait.h>
 
 static int
@@ -53,12 +54,16 @@ slurp_eq(const char *a, const char *b)
 		return -1;
 	}
 	int rc = 0;
+	size_t nb = 0;
 	for (;;) {
 		int ca = fgetc(fa);
 		int cb = fgetc(fb);
 		if (ca != cb) { rc = -1; break; }
 		if (ca == EOF) break;
+		nb++;
 	}
+	/* two 0-byte artifacts must not compare green (pkgcache 0-byte poison). */
+	if (rc == 0 && nb == 0) rc = -1;
 	fclose(fa); fclose(fb);
 	return rc;
 }
@@ -93,10 +98,10 @@ spawn_build(const char *bin, const char *cwd, struct buildjob *j)
 {
 	snprintf(j->workdir, sizeof j->workdir, "/tmp/wwsr_%d_%s",
 	    getpid(), j->tool);
-	char setup[256];
-	snprintf(setup, sizeof setup, "rm -rf %s && mkdir -p %s",
-	    j->workdir, j->workdir);
-	if (runwait(setup) != 0) return -1;
+	if (mkdir(j->workdir, 0755) != 0) {
+		perror(j->workdir);
+		return -1;
+	}
 
 	char cmd[4096];
 	if (j->inc_local && j->inc_local[0]) {
@@ -115,7 +120,14 @@ spawn_build(const char *bin, const char *cwd, struct buildjob *j)
 	}
 
 	pid_t p = fork();
-	if (p < 0) return -1;
+	if (p < 0) {
+		char clean[128];
+		snprintf(clean, sizeof clean, "rm -rf %s", j->workdir);
+		if (runwait(clean) != 0)
+			fprintf(stderr, "self-rebuild: cleanup %s failed\n",
+			    j->workdir);
+		return -1;
+	}
 	if (p == 0) {
 		int rc = system(cmd);
 		if (rc == -1) _exit(1);
@@ -162,7 +174,11 @@ collect_build(const char *bin, struct buildjob *j)
 
 	char cleanup[128];
 	snprintf(cleanup, sizeof cleanup, "rm -rf %s", j->workdir);
-	runwait(cleanup);
+	int cleanfail = runwait(cleanup) != 0;
+	if (cleanfail)
+		fprintf(stderr, "self-rebuild: cleanup %s failed\n", j->workdir);
+	if (cleanfail && rc == 0)
+		rc = -1;
 	return rc;
 }
 
diff --git a/test/wcc/996_dyn_ww.c b/test/wcc/996_dyn_ww.c
index 87e07ad3..af7245fc 100644
--- a/test/wcc/996_dyn_ww.c
+++ b/test/wcc/996_dyn_ww.c
@@ -10,6 +10,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <errno.h>
 #include <unistd.h>
 #include <sys/wait.h>
 
@@ -67,22 +68,23 @@ main(void)
 	 * private /tmp stem (NOT next to the tracked example source), then
 	 * link <stem>.sepwork/__root.o — the self-contained single-package
 	 * object the flip emits in place of the old next-to-source .o. */
-	char cmd[4096], mbstem[256], mbobj[320];
+	char cmd[4096], mbstem[256], mbobj[320], co[64], wo[64];
 	snprintf(mbstem, sizeof mbstem, "/tmp/wwld_%d_mb", getpid());
 	snprintf(mbobj, sizeof mbobj, "%s.sepwork/__root.o", mbstem);
+	snprintf(co, sizeof co, "/tmp/wwld_%d_c", getpid());
+	snprintf(wo, sizeof wo, "/tmp/wwld_%d_w", getpid());
+
+	int rc = 0;
 	snprintf(cmd, sizeof cmd,
 	    "cd %s/examples/mandelbrot && %s/ww build "
 	    "-o %s mandelbrot.ww -L /usr/lib -l c >/dev/null 2>&1",
 	    cwd, bin, mbstem);
 	if (runwait(cmd) != 0) {
 		fprintf(stderr, "w6l_ww-dyn FAIL: cannot build mandelbrot.o via C driver\n");
-		return 1;
+		rc = 1;
+		goto cleanup;
 	}
 
-	char co[64], wo[64];
-	snprintf(co, sizeof co, "/tmp/wwld_%d_c", getpid());
-	snprintf(wo, sizeof wo, "/tmp/wwld_%d_w", getpid());
-
 	/* C-side w6l with the dynamic flags. */
 	snprintf(cmd, sizeof cmd,
 	    "%s/w6l -o %s %s -L /usr/lib "
@@ -90,8 +92,8 @@ main(void)
 	    bin, co, mbobj, cwd);
 	if (runwait(cmd) != 0) {
 		fprintf(stderr, "w6l_ww-dyn FAIL: C w6l errored\n");
-		unlink(co);
-		return 1;
+		rc = 1;
+		goto cleanup;
 	}
 
 	/* ww-side w6l with the same flags. */
@@ -101,16 +103,18 @@ main(void)
 	    bin, wo, mbobj, cwd);
 	if (runwait(cmd) != 0) {
 		fprintf(stderr, "w6l_ww-dyn FAIL: ww w6l errored\n");
-		unlink(co); unlink(wo);
-		return 1;
+		rc = 1;
+		goto cleanup;
 	}
 
 	char *bc = NULL, *bw = NULL;
 	size_t nc = 0, nw = 0;
-	int rc = 0;
 	if (slurp(co, &bc, &nc) < 0 || slurp(wo, &bw, &nw) < 0) {
 		fprintf(stderr, "w6l_ww-dyn FAIL: cannot read outputs\n");
 		rc = 1;
+	} else if (nc == 0) {
+		fprintf(stderr, "w6l_ww-dyn FAIL: empty outputs\n");
+		rc = 1;
 	} else if (nc != nw || memcmp(bc, bw, nc) != 0) {
 		fprintf(stderr, "w6l_ww-dyn FAIL: C %zu vs ww %zu bytes\n",
 		    nc, nw);
@@ -121,9 +125,24 @@ main(void)
 		    "%zu bytes)\n", nc);
 	}
 	free(bc); free(bw);
-	unlink(co); unlink(wo);
-	/* #93: the sep scratch + tmpdir-owned outputs. */
-	snprintf(cmd, sizeof cmd, "rm -rf %s.sepwork %s", mbstem, mbstem);
-	if (system(cmd)) {}
+
+cleanup:
+	/* #93: `ww build` retains this exact caller-owned scratch tree. */
+	snprintf(cmd, sizeof cmd, "rm -rf %s.sepwork", mbstem);
+	int cleanfail = runwait(cmd) != 0;
+	if (unlink(co) != 0 && errno != ENOENT) {
+		perror(co);
+		cleanfail = 1;
+	}
+	if (unlink(wo) != 0 && errno != ENOENT) {
+		perror(wo);
+		cleanfail = 1;
+	}
+	if (unlink(mbstem) != 0 && errno != ENOENT) {
+		perror(mbstem);
+		cleanfail = 1;
+	}
+	if (cleanfail && rc == 0)
+		rc = 1;
 	return rc;
 }