diff --git a/test/devloop.sh b/test/devloop.sh
index a4054ad..ed713ac 100755
--- a/test/devloop.sh
+++ b/test/devloop.sh
@@ -69,8 +69,9 @@ for s in "$@"; do
 	PGC_SKIP_BUILD=1 PGC_PORT=$((PGC_PORT_LO + RANDOM % (PGC_PORT_HI - PGC_PORT_LO))) \
 		bash "test/${s}.sh" "$PGC"
 	_rc=$?
-	# 2 is pgc_summary's skipped state (#447), not a failure.
-	if [ "$_rc" != 0 ] && [ "$_rc" != 2 ]; then
+	# 66 is pgc_summary's skipped state, not a failure. Not 2: bash returns 2 on
+	# a parse error, so treating 2 as a skip hides a broken suite file.
+	if [ "$_rc" != 0 ] && [ "$_rc" != 66 ]; then
 		rc=1
 	fi
 done
diff --git a/test/lib.sh b/test/lib.sh
index c6f5001..231fb05 100755
--- a/test/lib.sh
+++ b/test/lib.sh
@@ -30,6 +30,22 @@
 PGC_FAIL=0
 PGC_CHECKS=0
 
+# The status pgc_summary uses for "ran no checks".
+#
+# NOT 2. #448 used 2 and that was wrong: 2 is a status suites already produce for
+# unrelated reasons. bash exits 2 on a parse error in the suite file (verified),
+# and the suites that run under `set -euo pipefail` -- smoke, phase2 through
+# phase6, audit -- abort with whatever status the failing command returned, so a
+# dead postmaster or a typo became "ran no checks" and every runner reported the
+# major green. That is precisely the lie #447 was opened to remove, relocated one
+# layer down.
+#
+# 66 is not produced by bash (1, 2, 126, 127, 128+n), by psql (1, 2, 3), or by
+# make. It cannot be made collision-proof -- `set -e` propagates any status an
+# aborting command returns -- so the runners ALSO require the SKIPPED line in the
+# log before believing it. Two independent signals, because one was not enough.
+PGC_EXIT_SKIPPED=66
+
 # ---- cluster identity helpers ----------------------------------------------
 
 # Normalize a directory for comparison. `cd && pwd -P` is POSIX; realpath -m is
@@ -639,7 +655,7 @@ pgc_summary() {
 	fi
 	if [ "$PGC_CHECKS" = "0" ]; then
 		echo "$(basename "$0"): SKIPPED (ran no checks)"
-		exit 2
+		exit $PGC_EXIT_SKIPPED
 	fi
 	echo "$(basename "$0"): PASSED"
 	exit 0
diff --git a/test/native_parquet_streaming.sh b/test/native_parquet_streaming.sh
index f4206ab..7d95d27 100755
--- a/test/native_parquet_streaming.sh
+++ b/test/native_parquet_streaming.sh
@@ -60,9 +60,12 @@ if os.path.getsize(big) != SIZE:
     sys.exit(4)
 PY
 then
-	echo "SKIP  could not build the oversized sparse file"
-	pgc_summary
-	exit 0
+	# An environment that cannot build the file is a box that cannot gate this
+	# suite, not a major without the feature. The pyarrow gate thirty lines above
+	# was converted and this one was missed, so a low-space or non-sparse
+	# filesystem quietly took the 1GB-palloc ceiling and the 1600MB-hole guard out
+	# of the run while the major still reported PASS.
+	pgc_skip sparse_file "could not build the oversized sparse file"
 fi
 
 # errtext QUERY -> the raised ERROR line, or "NO ERROR"
diff --git a/test/native_repack.sh b/test/native_repack.sh
index 9ec7dab..77cccb0 100755
--- a/test/native_repack.sh
+++ b/test/native_repack.sh
@@ -46,7 +46,20 @@ pgc_setup "${1:-/usr/local/pg19/bin/pg_config}"
 # Version gate, and it must be VISIBLE. A suite that silently passes on 15 to 18
 # is the failure mode this project keeps finding.
 srv="$(q 'SHOW server_version_num')"
-if [ "${srv:-0}" -lt 190000 ]; then
+# An empty answer is a cluster that stopped talking, not PostgreSQL 18. ${srv:-0}
+# made those identical, so a dead postmaster reported SKIPPED and the major passed.
+#
+# The failure is raised only when it happens, rather than as a check that always
+# runs: a passing check would put PGC_CHECKS at 1, and this suite's whole verdict
+# on an older major depends on it being 0. Asserting the premise must not destroy
+# the skip it guards.
+if ! pgc_is_number "$srv"; then
+	PGC_CHECKS=$((PGC_CHECKS + 1))
+	PGC_FAIL=1
+	echo "FAIL  the server did not answer 'SHOW server_version_num': got [$srv]"
+	pgc_summary
+fi
+if [ "$srv" -lt 190000 ]; then
 	echo "SKIP  REPACK requires PostgreSQL 19 (server_version_num=$srv)"
 	pgc_summary
 fi
diff --git a/test/pg19_vacuum_options.sh b/test/pg19_vacuum_options.sh
index ec485c7..8fa5399 100755
--- a/test/pg19_vacuum_options.sh
+++ b/test/pg19_vacuum_options.sh
@@ -32,7 +32,20 @@ set -uo pipefail
 pgc_setup "${1:-/usr/local/pg19/bin/pg_config}"
 
 srv="$(q 'SHOW server_version_num')"
-if [ "${srv:-0}" -lt 190000 ]; then
+# An empty answer is a cluster that stopped talking, not PostgreSQL 18. ${srv:-0}
+# made those identical, so a dead postmaster reported SKIPPED and the major passed.
+#
+# The failure is raised only when it happens, rather than as a check that always
+# runs: a passing check would put PGC_CHECKS at 1, and this suite's whole verdict
+# on an older major depends on it being 0. Asserting the premise must not destroy
+# the skip it guards.
+if ! pgc_is_number "$srv"; then
+	PGC_CHECKS=$((PGC_CHECKS + 1))
+	PGC_FAIL=1
+	echo "FAIL  the server did not answer 'SHOW server_version_num': got [$srv]"
+	pgc_summary
+fi
+if [ "$srv" -lt 190000 ]; then
 	echo "SKIP  parallel autovacuum requires PostgreSQL 19 (server_version_num=$srv)"
 	pgc_summary
 fi
diff --git a/test/run_all_versions.sh b/test/run_all_versions.sh
index 9de01bd..821151c 100755
--- a/test/run_all_versions.sh
+++ b/test/run_all_versions.sh
@@ -434,10 +434,15 @@ for pgc in "${CONFIGS[@]}"; do
 		# its assertions untrustworthy, only slower.
 		if [ "${PGC_SKIP_TIMING:-0}" = 1 ] && is_timing_suite "$s"; then
 			echo "  SKIP  $s (PGC_SKIP_TIMING)"
-			# 2, not 0. This suite did not run, and since #447 the collector has
-			# a state that says so. Recording it as a pass was the same lie the
-			# zero-check suites were telling, just written by the driver.
-			echo 2 >"$builddir/${s}.rc"
+			# 66, not 0. This suite did not run, and the collector has a state
+			# that says so. Recording it as a pass was the same lie the zero-check
+			# suites were telling, just written by the driver.
+			#
+			# The log is written too, because the collector requires the marker as
+			# well as the status: this branch never executes the suite, so nothing
+			# else would produce one and the run would be classified a failure.
+			echo 66 >"$builddir/${s}.rc"
+			echo "$s.sh: SKIPPED (ran no checks)" >"$builddir/${s}.log"
 			continue
 		fi
 		port=$((BASE_PORT++))
@@ -456,7 +461,7 @@ for pgc in "${CONFIGS[@]}"; do
 			echo "  PASS  $s"
 			results+="$s=PASS "
 			suites_ran=$((suites_ran + 1))
-		elif [ "$_rc" = 2 ]; then
+		elif [ "$_rc" = 66 ] && grep -q 'SKIPPED (ran no checks)' "$builddir/${s}.log" 2>/dev/null; then
 			# Exit 2 is pgc_summary's third state: the suite ran no checks (#447).
 			# Not a pass, because it asserted nothing. Not a failure, because a
 			# major without the feature and a box without an optional dependency
diff --git a/test/run_coverage.sh b/test/run_coverage.sh
index a3dbaec..e0e8c9d 100755
--- a/test/run_coverage.sh
+++ b/test/run_coverage.sh
@@ -81,12 +81,17 @@ port="$(pgc_pick_port)"
 pass=0; fail=0; failed=""; skip=0; skipped=""
 for s in $SUITES; do
 	port=$((port + 1))
-	PGC_SKIP_BUILD=1 PGC_PORT="$port" \
+	# PGC_SKIP_TIMING, because a --coverage build is instrumented and its wall
+	# clock means nothing. The wall-clock suites assert ratios and absolute
+	# timeouts; run here without the flag they fail for the instrumentation rather
+	# than for the code, and this runner discovers every test/*.sh including any
+	# added later. The matrix is where those numbers are taken.
+	PGC_SKIP_BUILD=1 PGC_SKIP_TIMING=1 PGC_PORT="$port" \
 		bash "$SRCDIR/test/${s}.sh" "$PGC" >"$OUT/${s}.log" 2>&1
 	rc=$?
 	if [ "$rc" = 0 ]; then
 		pass=$((pass + 1))
-	elif [ "$rc" = 2 ]; then
+	elif [ "$rc" = 66 ] && grep -q 'SKIPPED (ran no checks)' "$OUT/${s}.log" 2>/dev/null; then
 		# Ran no checks (#447). It contributed no coverage either, so counting it
 		# as a pass overstates what this report measured.
 		skip=$((skip + 1)); skipped="$skipped $s"
@@ -95,6 +100,13 @@ for s in $SUITES; do
 	fi
 done
 echo "-- suites: $pass passed, $fail failed${failed:+ ($failed)}, $skip skipped${skipped:+ ($skipped)}"
+# A coverage report built from nothing is not a coverage report. run_san grew this
+# guard and this runner did not, so its only verdict was "nothing failed" -- which
+# a box where every suite aborts satisfies perfectly.
+if [ "$pass" = 0 ]; then
+	echo "-- NO SUITE RAN, so this measures no coverage"
+	fail=$((fail + 1))
+fi
 
 echo "-- collect"
 lcov --directory "$SRCDIR/src" --capture --output-file "$OUT/coverage.info" \
diff --git a/test/run_san.sh b/test/run_san.sh
index bf3e35a..a669b2d 100644
--- a/test/run_san.sh
+++ b/test/run_san.sh
@@ -97,11 +97,14 @@ for s in $SUITES; do
 	# A sanitizer report reaches here two ways: the backend aborts (SIGABRT, so the
 	# suite's own crash checks or a nonzero rc), or the text appears in the output.
 	san="$(printf '%s' "$out" | grep -icE 'runtime error:|AddressSanitizer|UndefinedBehaviorSanitizer|SUMMARY: .*Sanitizer|terminated by signal 6')"
-	if [ "$rc" = 2 ] && [ "$san" = 0 ]; then
-		# pgc_summary's skipped state (#447): the suite ran no checks. Five of
-		# this runner's default subset are pyarrow-gated, so on a sanitizer image
-		# without pyarrow this is the difference between "no sanitizer findings"
-		# and "nothing was sanitized".
+	if [ "$rc" = 66 ] && [ "$san" = 0 ] && \
+	   printf '%s' "$out" | grep -q 'SKIPPED (ran no checks)'; then
+		# pgc_summary's skipped state: the suite ran no checks.
+		#
+		# This does NOT cover the pyarrow-gated suites, and an earlier version of
+		# this comment claimed it did. Since a missing dependency FAILS, pgc_skip
+		# exits 1, not here. What reaches this branch is a suite with nothing to
+		# assert on this build, which is a different thing and a rarer one.
 		skipped=$((skipped + 1))
 		echo "  SKIP  $s  (ran no checks)"
 	elif [ "$rc" != 0 ] || [ "$san" != 0 ]; then
@@ -116,11 +119,12 @@ done
 echo "-- $ran suites under sanitizers, $fail failed, $skipped ran no checks"
 if [ "$fail" != 0 ]; then
 	echo "SANITIZER GATE FAILED"
-elif [ "$skipped" = "$ran" ]; then
-	# Every suite skipped means nothing was sanitized. Five of the default subset
-	# are pyarrow-gated, so an image without pyarrow could otherwise report the
-	# gate passed having exercised no decode path at all (#447).
-	echo "SANITIZER GATE RAN NOTHING, which is not a pass"
+elif [ "$skipped" != 0 ]; then
+	# ANY skip, not just all of them. The previous form fired only when every
+	# suite skipped, so 22 of 23 skipped still printed PASSED -- a gate reporting
+	# on a surface it had almost entirely not exercised. A sanitizer run is worth
+	# what it covered, so an incomplete one is not a pass.
+	echo "SANITIZER GATE INCOMPLETE: $skipped of $ran suites ran no checks"
 	fail=1
 else
 	echo "SANITIZER GATE PASSED"