Give the words' zone through a seam, so no test writes time.Local under the race detector (novox/hq issue 443)

cmd/mesh-controller/delivery_conditions.go

@@ -61,6 +61,10 @@ type waitingCheck struct {
 // wordsNow is the time the words are said at, which says whether a time needs its day; a seam a test replaces.
 var wordsNow = time.Now
 
+// wordsZone is the zone a stalled line's times are said in: the controller's local zone, as every other time in its
+// messages. A seam a test replaces, so that no test writes time.Local, which every goroutine of the package reads.
+var wordsZone = func() *time.Location { return time.Local }
+
 // operatorsOnly is whether the table leaves H2 nothing to do for the line: the state is the operator's.
 func (l stalledLine) operatorsOnly() bool { return l.H2 == "" || strings.HasPrefix(l.H2, "none") }
 

cmd/mesh-controller/plain_words.go

@@ -921,7 +921,7 @@ func sinceWords(since string) string {
 	if err != nil {
 		return ", since a time the forge did not say"
 	}
-	local, today := at.Local(), wordsNow().Local()
+	local, today := at.In(wordsZone()), wordsNow().In(wordsZone())
 	if local.YearDay() == today.YearDay() && local.Year() == today.Year() {
 		return " since " + local.Format("15:04")
 	}

cmd/mesh-controller/plain_words_test.go

@@ -408,10 +408,12 @@ func TestAnUnansweredMergeCheckSaysWhichCheckAndWhatToDo(t *testing.T) {
 // the finished words it gave before, and the controller words it in its local zone, as every other time in a message.
 // The line is the one mesh-delivery says, as in the report of issue 443, with the checks it now carries.
 func TestAnUnansweredMergeChecksTimeIsSaidInLocalTime(t *testing.T) {
-	was, wasNow := time.Local, wordsNow
+	// The operator's zone given through the seam, never by writing time.Local: other tests' goroutines read it, and
-	time.Local = time.FixedZone("CEST", 2*60*60)
+	// the build seat runs the suite under the race detector.
+	wasZone, wasNow := wordsZone, wordsNow
+	wordsZone = func() *time.Location { return time.FixedZone("CEST", 2*60*60) }
 	wordsNow = func() time.Time { return time.Date(2026, 10, 11, 1, 12, 39, 0, time.UTC) }
-	t.Cleanup(func() { time.Local, wordsNow = was, wasNow })
+	t.Cleanup(func() { wordsZone, wordsNow = wasZone, wasNow })
 
 	var l stalledLine
 	if err := json.Unmarshal([]byte(`{"id":"novox/mesh-controller@c11222026a3b","number":212,"state":"unanswered",`+