Read the load average through LOADAVG_FILE so the probe tests are host-independent

The "flags nothing on a quiet machine" case read the real /proc/loadavg and
went red whenever a game was running on the host (22/16 during a BeamNG
session), and the "flags a load at/above thread count" case had to SKIP
whenever the host was idle. Same override pattern as JOURNALD_CONF_DIR: the
harness writes a fixture, both cases now assert deterministically, and a
missing file degrades to 0 as before.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SS8M5wk88nJTXxDWz61KKk

docs/superpowers/evidence/perf-probes-loadavg-fixture-2026-09-14.json

@@ -0,0 +1,29 @@
+{
+  "intent": "Make the arch_perf_probes lib tests independent of the host's real load average so the pre-push ci-mirror gate is not red whenever a game is running.",
+  "scope": [
+    "linux_configuration/fixes/lib/arch_perf_probes.sh (LOADAVG_FILE override, default /proc/loadavg)",
+    "linux_configuration/fixes/lib/tests/arch_perf_harness.sh (fixture written by arch_reset)",
+    "linux_configuration/fixes/lib/tests/test_arch_perf_probes.sh (deterministic load cases)"
+  ],
+  "changes": [
+    "collect_basics reads the 1-minute load from ${LOADAVG_FILE:-/proc/loadavg}; behaviour on the host is unchanged",
+    "The harness exports LOADAVG_FILE into TEST_TMPDIR and arch_reset writes a quiet fixture (0.10)",
+    "The load test now asserts the (16/16) finding from a 16.50 fixture instead of SKIPping when the host is idle; a missing file case asserts no finding"
+  ],
+  "verification": [
+    {
+      "command": "./linux_configuration/fixes/lib/tests/test_arch_perf_probes.sh",
+      "result": "pass",
+      "evidence": "arch_perf_probes (basics/governor): 17 passed, 0 failed (was 16 with one SKIP, and 1 failed at host load 22/16)"
+    },
+    {
+      "command": "./linux_configuration/fixes/lib/tests/run_all.sh (host load ~19/16, BeamNG running)",
+      "result": "pass",
+      "evidence": "All fixes lib test files passed."
+    }
+  ],
+  "risks": ["None on the host: the default path is the real /proc/loadavg"],
+  "rollback": [
+    "git revert the commit; the tests return to reading the real load and go red under host load"
+  ]
+}

linux_configuration/fixes/lib/arch_perf_probes.sh

@@ -19,7 +19,9 @@ collect_basics() {
 	local cpu_count
 	cpu_count=$(getconf _NPROCESSORS_ONLN 2>/dev/null || echo 1)
 	local load1
-	load1=$(awk '{print int($1)}' /proc/loadavg 2>/dev/null || echo 0)
+	# Overridable so the tests do not depend on the host being idle: the
+	# "quiet machine" case went red whenever a game was running on the host.
+	load1=$(awk '{print int($1)}' "${LOADAVG_FILE:-/proc/loadavg}" 2>/dev/null || echo 0)
 	if [[ ${load1:-0} -ge ${cpu_count:-1} ]]; then
 		add_finding "1-minute load average is at/above CPU thread count (${load1}/${cpu_count}); background tasks may be saturating the system."
 	fi

linux_configuration/fixes/lib/tests/arch_perf_harness.sh

@@ -37,6 +37,9 @@ export REPORT_FILE="${TEST_TMPDIR}/report.log"
 export JOURNALD_CONF_DIR="${TEST_TMPDIR}/journald.conf.d"
 export SYSTEMD_UNIT_DIR="${TEST_TMPDIR}/systemd_units"
 export ORGANIZE_SCRIPT_CANDIDATES="${TEST_TMPDIR}/organize_downloads.sh"
+# collect_basics reads the 1-minute load from here; a fixture, not the real
+# /proc/loadavg, or the "quiet machine" case depends on nothing else running.
+export LOADAVG_FILE="${TEST_TMPDIR}/loadavg"
 export APPLY_SAFE_FIXES="false"
 export INSTALL_TOOLS="false"
 declare -a FINDINGS=()
@@ -85,6 +88,7 @@ arch_reset() {
 	rm -rf "${JOURNALD_CONF_DIR}" "${SYSTEMD_UNIT_DIR}"
 	mkdir -p "${JOURNALD_CONF_DIR}" "${SYSTEMD_UNIT_DIR}"
 	rm -f "${ORGANIZE_SCRIPT_CANDIDATES}"
+	echo "0.10 0.20 0.30 1/100 1" >"${LOADAVG_FILE}"
 	_t_full_path
 	_arch_default_stubs
 }

linux_configuration/fixes/lib/tests/test_arch_perf_probes.sh

@@ -67,20 +67,25 @@ _t_contains "$findings" "ACPI errors detected" \
 _t_contains "$findings" "Xorg is using high CPU (45%)" \
 	"collect_basics: flags a CPU-hungry Xorg"
 
-# A load average at or above the thread count is flagged. /proc/loadavg is
-# read directly by the lib, so the case is driven by a low CPU count instead.
+# A load average at or above the thread count is flagged.
 arch_reset
-_t_stub getconf 'echo 1'
+_t_stub getconf 'echo 16'
 _t_stub systemctl 'exit 0'
 _t_stub journalctl 'exit 0'
 _t_stub ps 'echo none'
+echo "16.50 12.00 9.00 3/900 1" >"${LOADAVG_FILE}"
 collect_basics
-if [[ $(awk '{print int($1)}' /proc/loadavg) -ge 1 ]]; then
-	_t_contains "$(_t_findings)" "load average is at/above CPU thread count" \
-		"collect_basics: flags a load average at or above the thread count"
-else
-	_t_pass "collect_basics: SKIP load case (this host's 1-minute load is below 1)"
-fi
+_t_contains "$(_t_findings)" "load average is at/above CPU thread count (16/16)" \
+	"collect_basics: flags a load average at or above the thread count"
+
+# An unreadable load file degrades to 0 rather than aborting the probe.
+arch_reset
+_t_stub systemctl 'exit 0'
+_t_stub journalctl 'exit 0'
+_t_stub ps 'echo none'
+rm -f "${LOADAVG_FILE}"
+collect_basics
+_t_eq "" "$(_t_findings)" "collect_basics: missing load file is not a finding"
 
 # --- check_cpu_governor -----------------------------------------------------