diff --git a/modules/mesh-mail-reader/cmd/mesh-mail-reader/main.go b/modules/mesh-mail-reader/cmd/mesh-mail-reader/main.go
index 2104558e..9f88737f 100644
--- a/modules/mesh-mail-reader/cmd/mesh-mail-reader/main.go
+++ b/modules/mesh-mail-reader/cmd/mesh-mail-reader/main.go
@@ -74,6 +74,7 @@ func main() {
 	b := &Bundle{Env: envFromOS(), Store: store.get}
 	go hearLoop(store.get, stdio.Subscribe, time.Sleep)
 	go batchLoop(store.get)
+	go removeEachNight(store.get, time.Now, time.Sleep, logf)
 	if err := stdio.ServeOn("", b.Tools(), os.Stdin, os.Stdout); err != nil {
 		logf("[mesh-mail-reader] %v", err)
 		os.Exit(1)
diff --git a/modules/mesh-mail-reader/cmd/mesh-mail-reader/prune.go b/modules/mesh-mail-reader/cmd/mesh-mail-reader/prune.go
new file mode 100644
index 00000000..de0f347f
--- /dev/null
+++ b/modules/mesh-mail-reader/cmd/mesh-mail-reader/prune.go
@@ -0,0 +1,49 @@
+package main
+
+// The nightly removal (novox/hq ADR 0517 §9, issue 1858): the action log keeps a line 365 days; each night at
+// 03:00 (Europe/Brussels) the older ones are removed, and the journal says how many. Handling and reminders
+// need no removal of their own: they go with their entry (ADR 0517 §10, the schema's on delete cascade).
+
+import (
+	"context"
+	"time"
+)
+
+// ActionsKeptFor is how long an action line is kept.
+const ActionsKeptFor = 365 * 24 * time.Hour
+
+// RemoveOldActions removes the lines older than ActionsKeptFor, answering how many.
+func RemoveOldActions(ctx context.Context, store Store, now time.Time, logf func(string, ...any)) (int64, error) {
+	removed, err := store.RemoveActionsBefore(ctx, now.Add(-ActionsKeptFor))
+	if err != nil {
+		return 0, err
+	}
+	logf("[mesh-mail-reader] the nightly removal: %d action lines older than 365 days removed", removed)
+	return removed, nil
+}
+
+// nextNight is the next 03:00 in the operator's zone after now.
+func nextNight(now time.Time) time.Time {
+	local := now.In(Brussels)
+	night := time.Date(local.Year(), local.Month(), local.Day(), 3, 0, 0, 0, Brussels)
+	if !night.After(now) {
+		night = time.Date(local.Year(), local.Month(), local.Day()+1, 3, 0, 0, 0, Brussels)
+	}
+	return night
+}
+
+// removeEachNight runs the removal at once, then each night, forever; a failure is said and tried again the
+// next night.
+func removeEachNight(storeFor func(context.Context) (Store, error), now func() time.Time, sleep func(time.Duration), logf func(string, ...any)) {
+	for {
+		ctx := context.Background()
+		store, err := storeFor(ctx)
+		if err == nil {
+			_, err = RemoveOldActions(ctx, store, now(), logf)
+		}
+		if err != nil {
+			logf("[mesh-mail-reader] the nightly removal failed: %v; it tries again the next night", err)
+		}
+		sleep(nextNight(now()).Sub(now()))
+	}
+}
diff --git a/modules/mesh-mail-reader/cmd/mesh-mail-reader/prune_test.go b/modules/mesh-mail-reader/cmd/mesh-mail-reader/prune_test.go
new file mode 100644
index 00000000..b32516fa
--- /dev/null
+++ b/modules/mesh-mail-reader/cmd/mesh-mail-reader/prune_test.go
@@ -0,0 +1,46 @@
+package main
+
+// Issue 1858/AC7 (novox/hq ADR 0517 §9): each night, the action lines older than 365 days are removed.
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+// 1858/AC7: the removal drops the lines older than 365 days, and keeps the rest.
+func TestTheNightlyRemovalDropsLinesOlderThan365Days(t *testing.T) {
+	ctx := context.Background()
+	store := newMemStore()
+	now := brusselsAt(2026, 10, 22, 3, 0)
+	for _, age := range []time.Duration{366 * 24 * time.Hour, 365*24*time.Hour + time.Minute, 365*24*time.Hour - time.Hour, time.Hour} {
+		_ = store.Record(ctx, ActionLine{What: ActPageOpened, Mode: "work", At: now.Add(-age)})
+	}
+	removed, err := RemoveOldActions(ctx, store, now, noopLogf)
+	if err != nil {
+		t.Fatal(err)
+	}
+	left := lines(t, store)
+	if removed != 2 || len(left) != 2 {
+		t.Fatalf("removed %d, %d left; want 2 removed (older than 365 days) and 2 kept", removed, len(left))
+	}
+	for _, l := range left {
+		if now.Sub(l.At) > ActionsKeptFor {
+			t.Fatalf("kept a line of %s, older than 365 days", l.At)
+		}
+	}
+}
+
+// 1858/AC7: the removal runs each night at 03:00 in the operator's zone: the next one is tonight's, or
+// tomorrow's once tonight's has passed.
+func TestTheRemovalRunsEachNight(t *testing.T) {
+	for _, tc := range []struct{ now, want time.Time }{
+		{brusselsAt(2026, 10, 22, 1, 0), brusselsAt(2026, 10, 22, 3, 0)},
+		{brusselsAt(2026, 10, 22, 3, 0), brusselsAt(2026, 10, 23, 3, 0)},
+		{brusselsAt(2026, 10, 24, 22, 0), brusselsAt(2026, 10, 25, 3, 0)}, // the night the clocks go back
+	} {
+		if got := nextNight(tc.now); !got.Equal(tc.want) {
+			t.Fatalf("nextNight(%s) = %s, want %s", tc.now, got, tc.want)
+		}
+	}
+}