R-1292: qBittorrent's 50 % rule owns the NORMAL limit only (up_limit through app/preferences), never the current speed mode's slot. Test with the alternative mode on, red-proved. Commit only.

controller/internal/upwatch/explain_test.go

@@ -3,6 +3,7 @@ package upwatch
 import (
 	"context"
 	"encoding/base64"
+	"encoding/json"
 	"fmt"
 	"net/http"
 	"net/http/httptest"
@@ -54,6 +55,20 @@ func fakeQBServer(t *testing.T, pw string, logins *int, expireNext *bool, limit
 			fmt.Sscan(r.Form.Get("limit"), &v)
 			*limit = v / 1024 * 1024
 			w.WriteHeader(200)
+		// R-1292: the 50 % rule reads and writes the NORMAL slot through app/preferences (normal mode here: the same value).
+		case "/api/v2/app/preferences":
+			fmt.Fprintf(w, `{"up_limit":%d,"alt_up_limit":0}`, *limit)
+		case "/api/v2/app/setPreferences":
+			r.ParseForm()
+			var m map[string]int64
+			if err := json.Unmarshal([]byte(r.Form.Get("json")), &m); err != nil {
+				w.WriteHeader(400)
+				return
+			}
+			if v, ok := m["up_limit"]; ok {
+				*limit = v / 1024 * 1024
+			}
+			w.WriteHeader(200)
 		default:
 			w.WriteHeader(404)
 		}

controller/internal/upwatch/line_test.go

@@ -85,8 +85,8 @@ type fakeQB struct {
 	sets []int64
 }
 
-func (f *fakeQB) UploadLimit(context.Context, map[string]string) (int64, error) { return f.cur, nil }
-func (f *fakeQB) SetUploadLimit(_ context.Context, b int64) (int64, error) {
+func (f *fakeQB) NormalLimit(context.Context) (int64, error) { return f.cur, nil }
+func (f *fakeQB) SetNormalLimit(_ context.Context, b int64) (int64, error) {
 	f.sets = append(f.sets, b)
 	f.cur = b / 1024 * 1024 // qBittorrent keeps KiB/s
 	return f.cur, nil

controller/internal/upwatch/linehold.go

@@ -338,6 +338,17 @@ func (q *QBittorrent) WriteLimit(ctx context.Context, l HeldLimit) (HeldLimit, e
 	return q.readSlot(ctx, h, l.Alt)
 }
 
+// NormalLimit / SetNormalLimit are the 50 % rule's side (R-1292): the NORMAL slot (`up_limit`) whatever the mode.
+func (q *QBittorrent) NormalLimit(ctx context.Context) (int64, error) {
+	l, err := q.ReadLimitLike(ctx, HeldLimit{Alt: false})
+	return l.Bytes, err
+}
+
+func (q *QBittorrent) SetNormalLimit(ctx context.Context, bytesPerSec int64) (int64, error) {
+	l, err := q.WriteLimit(ctx, HeldLimit{Bytes: bytesPerSec, Alt: false})
+	return l.Bytes, err
+}
+
 // HoldValue: 1 KiB/s in the slot that applied when the hold began.
 func (q *QBittorrent) HoldValue(prev HeldLimit) HeldLimit {
 	return HeldLimit{Bytes: 1024, Alt: prev.Alt}

controller/internal/upwatch/qblimit.go

@@ -34,10 +34,13 @@ type QBLimitState struct {
 	HouseholdAt string  `json:"household_at,omitempty"`
 }
 
-// QBLimiter is the qBittorrent side the rule needs (the QBittorrent explainer satisfies it).
+// QBLimiter is the qBittorrent side the rule needs (the QBittorrent explainer satisfies it). R-1292: the rule owns the
+// NORMAL slot only (`up_limit` through app/preferences) — `transfer/uploadLimit`/`setUploadLimit` act on the CURRENT
+// speed mode's slot (measured on 5.2.4), so with the household's alternative speed on the rule used to set the
+// alternative limit, and the next switch read as „the household changed it". Never the alternative slot.
 type QBLimiter interface {
-	UploadLimit(ctx context.Context, h map[string]string) (int64, error)
-	SetUploadLimit(ctx context.Context, bytesPerSec int64) (int64, error)
+	NormalLimit(ctx context.Context) (int64, error)
+	SetNormalLimit(ctx context.Context, bytesPerSec int64) (int64, error)
 }
 
 // QBLimitTarget is share × line, in bytes/s.
@@ -51,7 +54,7 @@ func ApplyQBLimit(ctx context.Context, q QBLimiter, st QBLimitState, lineMbps fl
 	if st.Household {
 		return st, "household", nil
 	}
-	cur, err := q.UploadLimit(ctx, nil)
+	cur, err := q.NormalLimit(ctx)
 	if err != nil {
 		return st, "error", err
 	}
@@ -69,7 +72,7 @@ func ApplyQBLimit(ctx context.Context, q QBLimiter, st QBLimitState, lineMbps fl
 	if !lineKnown {
 		return st, "no-line", nil
 	}
-	stored, err := q.SetUploadLimit(ctx, QBLimitTarget(lineMbps, share))
+	stored, err := q.SetNormalLimit(ctx, QBLimitTarget(lineMbps, share))
 	if err != nil {
 		return st, "error", err
 	}

controller/internal/upwatch/qblimit_r1292_test.go

@@ -0,0 +1,58 @@
+package upwatch
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+// R-1292: qBittorrent's 50 % rule owns the NORMAL slot only. With the household's alternative speed on, the rule used
+// to read and write the CURRENT mode's slot (`transfer/uploadLimit`, measured on 5.2.4): it set the alternative limit,
+// and the next switch read as „the household changed it" — the rule stopped for good. The consequences asserted, on the
+// R-1261 fake that behaves like 5.2.4 (fakeQBPrefs): the normal limit is set, the alternative is untouched, and a later
+// switch either way still reads as the box's own limit.
+// RED-PROOF: ApplyQBLimit through UploadLimit/SetUploadLimit (the current mode's slot) → case 1 reads the household's
+// alternative 500 KiB/s as „the household's" and sets nothing; case 2 writes the alternative slot, the normal stays 0.
+
+func r1292Apply(t *testing.T, q *QBittorrent, st QBLimitState) (QBLimitState, string) {
+	t.Helper()
+	ns, act, err := ApplyQBLimit(context.Background(), q, st, 100, true, 0.5, time.Date(2026, 10, 26, 3, 0, 0, 0, time.UTC))
+	if err != nil {
+		t.Fatal(err)
+	}
+	return ns, act
+}
+
+func TestR1292_TheRuleSetsTheNormalSlotWhileTheAlternativeIsOn(t *testing.T) {
+	target := QBLimitTarget(100, 0.5)
+	for _, c := range []struct {
+		name string
+		alt  int64
+	}{{"the household's alternative speed 500 KiB/s", 512000}, {"no alternative limit set", 0}} {
+		t.Run(c.name, func(t *testing.T) {
+			f := &fakeQBPrefs{up: 0, alt: c.alt, altMode: true}
+			srv := f.server(t, "pw-1292")
+			defer srv.Close()
+			q := &QBittorrent{Box: envBox{"qbittorrent/QBT_ADMIN_PASSWORD": "pw-1292"}, URL: srv.URL}
+
+			st, act := r1292Apply(t, q, QBLimitState{})
+			if act != "set" || f.up < target-1024 || f.up > target || st.BoxSetBytes != f.up {
+				t.Fatalf("alternative mode on: the rule must set the NORMAL limit to ~%d (as stored): act %q, normal %d, recorded %d",
+					target, act, f.up, st.BoxSetBytes)
+			}
+			if f.alt != c.alt {
+				t.Fatalf("the alternative limit is the household's: %d → %d", c.alt, f.alt)
+			}
+
+			f.altMode = false // the household switches back to normal speed
+			st, act = r1292Apply(t, q, st)
+			if act != "kept" || st.Household {
+				t.Fatalf("a switch to normal must still read as the box's own limit: act %q, household %v", act, st.Household)
+			}
+			f.altMode = true // and back to the alternative
+			if _, act = r1292Apply(t, q, st); act != "kept" {
+				t.Fatalf("a switch back to the alternative must still read as the box's own limit: act %q", act)
+			}
+		})
+	}
+}