diff --git a/modules/claude-licence-manager/README.md b/modules/claude-licence-manager/README.md
index 1148eef35..6f7a2a6cb 100644
--- a/modules/claude-licence-manager/README.md
+++ b/modules/claude-licence-manager/README.md
@@ -55,10 +55,10 @@ reads alone and answers every act with "the carry-over has not ended"; a failed
 ## Switching on usage
 
 Every `usage_minutes` the manager reads each subscription's usage with its access token from the vault: the session,
-weekly and sonnet windows, each with its reset time. A licence's room is 100 less the higher of its session and weekly
-percentages, known only when it was read within `usage_stale_minutes` and its refresh is healthy. When a reading puts
-a licence with consumers at or above `switch_at_pct`, every consumer bound to it moves, in one act, to the licence
-with the most room whose windows are both below `room_below_pct`: one `binding.changed` per consumer, one
+weekly and sonnet windows, each with its reset time. A licence's room is 100 less its weekly percentage alone (the session
+window takes no part in room, the switch, the warning or the conditions: the vendor retired the session limit), known only when it was read within `usage_stale_minutes` and its refresh is healthy. When a reading puts
+a licence with consumers at or above `switch_at_pct` in its weekly window, every consumer bound to it moves, in one act, to the licence
+with the most room whose weekly window is below `room_below_pct`: one `binding.changed` per consumer, one
 `licence.switched`, and one `operator-channel.tell`. A consumer is never moved back by the rule.
 
 Its conditions are said on the operator channel's condition subject, the router deciding where they go:
diff --git a/modules/claude-licence-manager/cmd/claude-licence-manager/conditions.go b/modules/claude-licence-manager/cmd/claude-licence-manager/conditions.go
index 59ddae278..4e53daaa0 100644
--- a/modules/claude-licence-manager/cmd/claude-licence-manager/conditions.go
+++ b/modules/claude-licence-manager/cmd/claude-licence-manager/conditions.go
@@ -227,16 +227,16 @@ func (m *Manager) unread(l Licence, s Settings) (string, bool) {
 func (m *Manager) roomWords(o Licence, s Settings) string {
 	room, known := Room(o, m.Now(), s)
 	switch {
-	case known && (*o.Usage.SessionPct >= s.RoomBelow || *o.Usage.WeeklyPct >= s.RoomBelow):
-		return fmt.Sprintf("has %g %% room, a window not below %g %%", room, s.RoomBelow)
+	case known && *o.Usage.WeeklyPct >= s.RoomBelow:
+		return fmt.Sprintf("has %g %% room, its weekly window not below %g %%", room, s.RoomBelow)
 	case known:
 		return fmt.Sprintf("has %g %% room", room)
 	case o.Kind != "subscription":
 		return "is an API key, whose room is never known"
 	case o.Usage == nil || o.Usage.ReadAt == "":
 		return "has no reading"
-	case o.Usage.SessionPct == nil || o.Usage.WeeklyPct == nil:
-		return "has no session or weekly window in its reading"
+	case o.Usage.WeeklyPct == nil:
+		return "has no weekly window in its reading"
 	case o.Failures >= s.FailuresToNotify || (o.RefreshExpiresAt != 0 && o.RefreshExpiresAt <= m.Now().UnixMilli()):
 		return "does not refresh"
 	}
diff --git a/modules/claude-licence-manager/cmd/claude-licence-manager/conditions_test.go b/modules/claude-licence-manager/cmd/claude-licence-manager/conditions_test.go
index 6fbe66679..1fab35649 100644
--- a/modules/claude-licence-manager/cmd/claude-licence-manager/conditions_test.go
+++ b/modules/claude-licence-manager/cmd/claude-licence-manager/conditions_test.go
@@ -140,7 +140,7 @@ func TestNoRoomIsSaidOnceAndClearedByRoom(t *testing.T) {
 	ctx := context.Background()
 	mm := fourOnA(t)
 	_, said := saying(mm)
-	_ = mm.store.SaveLicence(ctx, sub("b", read(95, 20)))
+	_ = mm.store.SaveLicence(ctx, sub("b", read(20, 95)))
 	_ = mm.store.SaveLicence(ctx, sub("c", read(40, 99)))
 	for range 2 {
 		_ = mm.m.SayConditions(ctx, false)
@@ -158,7 +158,7 @@ func TestNoRoomIsSaidOnceAndClearedByRoom(t *testing.T) {
 	if c.Severity != occ.SeverityUrgent || c.Headline != "No licence has room for 4 machines" ||
 		c.Needs != "add a licence, or wait for a's weekly window to reset at 2026-11-14T09:00:00Z" ||
 		!strings.Contains(c.Explanation, "a is at 99 % of its weekly window, with ace, g14, laptop, server bound to it") ||
-		!strings.Contains(c.Explanation, "b has 5 % room, a window not below 90 %") ||
+		!strings.Contains(c.Explanation, "b has 5 % room, its weekly window not below 90 %") ||
 		c.Resolved != "ace, g14, laptop, server have a licence with room again" {
 		t.Fatalf("no-room %+v", c)
 	}
@@ -178,7 +178,7 @@ func TestNearLimitIsSaidOncePerCrossing(t *testing.T) {
 	key := "licence.a.near-limit"
 	var last oc.Condition
 	for _, w := range []float64{80, 89, 91, 91, 95} {
-		_ = mm.store.SaveLicence(ctx, sub("a", read(10, w)))
+		_ = mm.store.SaveLicence(ctx, sub("a", read(95, w))) // a session at 95 % takes no part (C4)
 		_ = mm.m.SayConditions(ctx, false)
 		for _, s := range *said {
 			if s.Key == key {
@@ -191,8 +191,8 @@ func TestNearLimitIsSaidOncePerCrossing(t *testing.T) {
 		!strings.Contains(last.Explanation, "which resets at 2026-11-14T09:00:00Z") {
 		t.Fatalf("said %v, last %+v", of(*said, key), last)
 	}
-	_ = mm.store.SaveLicence(ctx, sub("b", read(95, 0)))
-	_ = mm.store.SaveLicence(ctx, sub("c", read(95, 0)))
+	_ = mm.store.SaveLicence(ctx, sub("b", read(0, 95)))
+	_ = mm.store.SaveLicence(ctx, sub("c", read(0, 95)))
 	_ = mm.m.SayConditions(ctx, false)
 	if c := (*said)[len(*said)-1]; c.Key != key || c.Needs != "no other licence has room" {
 		t.Fatalf("with no target said %+v", c)
diff --git a/modules/claude-licence-manager/cmd/claude-licence-manager/room.go b/modules/claude-licence-manager/cmd/claude-licence-manager/room.go
index caa24142f..587448141 100644
--- a/modules/claude-licence-manager/cmd/claude-licence-manager/room.go
+++ b/modules/claude-licence-manager/cmd/claude-licence-manager/room.go
@@ -1,18 +1,15 @@
 package main
 
-// A licence's room (design 39 bus-and-switch §25, §48): 100 less the higher of its session and weekly percentages in
-// its latest reading, known only for a subscription read successfully within usage_stale_minutes, whose refresh has not
+// A licence's room (design 39 bus-and-switch §25, §48, C4): 100 less its weekly percentage in its latest reading, the
+// session window taking no part (the vendor retired the session limit), known only for a subscription read successfully within usage_stale_minutes, whose refresh has not
 // failed failures_to_notify times in a row and whose refresh token has not expired. An API key's room is never known,
 // so it is never a target.
 
-import (
-	"math"
-	"time"
-)
+import "time"
 
 // Room is a licence's room at now, and whether it is known.
 func Room(l Licence, now time.Time, s Settings) (float64, bool) {
-	if l.Kind != "subscription" || l.Usage == nil || l.Usage.SessionPct == nil || l.Usage.WeeklyPct == nil {
+	if l.Kind != "subscription" || l.Usage == nil || l.Usage.WeeklyPct == nil {
 		return 0, false
 	}
 	read, err := time.Parse(time.RFC3339Nano, l.Usage.ReadAt)
@@ -22,5 +19,5 @@ func Room(l Licence, now time.Time, s Settings) (float64, bool) {
 	if l.Failures >= s.FailuresToNotify || (l.RefreshExpiresAt != 0 && l.RefreshExpiresAt <= now.UnixMilli()) {
 		return 0, false
 	}
-	return 100 - math.Max(*l.Usage.SessionPct, *l.Usage.WeeklyPct), true
+	return 100 - *l.Usage.WeeklyPct, true
 }
diff --git a/modules/claude-licence-manager/cmd/claude-licence-manager/room_test.go b/modules/claude-licence-manager/cmd/claude-licence-manager/room_test.go
index aeafc0005..de14c71da 100644
--- a/modules/claude-licence-manager/cmd/claude-licence-manager/room_test.go
+++ b/modules/claude-licence-manager/cmd/claude-licence-manager/room_test.go
@@ -89,7 +89,7 @@ func TestAFailedReadingKeepsThePercentages(t *testing.T) {
 	}
 }
 
-// design 39 bus-and-switch §25/AC1, §48: a table of readings, ages and healths and the room each gives.
+// design 39 bus-and-switch §25/AC1, §48, C4: a table of readings, ages and healths and the room each gives.
 func TestTheRoomOfEachLicence(t *testing.T) {
 	now := t0
 	pct := func(v float64) *float64 { return &v }
@@ -102,8 +102,10 @@ func TestTheRoomOfEachLicence(t *testing.T) {
 		room  float64
 		known bool
 	}{
-		{"the higher window counts", Licence{Kind: "subscription", Usage: read(41, 97, time.Minute)}, 3, true},
-		{"the session can be the higher", Licence{Kind: "subscription", Usage: read(80, 20, time.Minute)}, 20, true},
+		{"the weekly window counts", Licence{Kind: "subscription", Usage: read(41, 97, time.Minute)}, 3, true},
+		{"the session takes no part (C4)", Licence{Kind: "subscription", Usage: read(80, 20, time.Minute)}, 80, true},
+		{"no session window, weekly 33 (C4)", Licence{Kind: "subscription", Usage: &UsageReading{WeeklyPct: pct(33),
+			ReadAt: now.Format(time.RFC3339Nano)}}, 67, true},
 		{"read at the stale bound", Licence{Kind: "subscription", Usage: read(10, 10, 15*time.Minute)}, 90, true},
 		{"read before the stale bound", Licence{Kind: "subscription", Usage: read(10, 10, 16*time.Minute)}, 0, false},
 		{"a failure since keeps the room", Licence{Kind: "subscription", Usage: func() *UsageReading {
diff --git a/modules/claude-licence-manager/cmd/claude-licence-manager/switching.go b/modules/claude-licence-manager/cmd/claude-licence-manager/switching.go
index 13027e4be..45bbc8ae6 100644
--- a/modules/claude-licence-manager/cmd/claude-licence-manager/switching.go
+++ b/modules/claude-licence-manager/cmd/claude-licence-manager/switching.go
@@ -1,9 +1,9 @@
 package main
 
 // The switch rule (design 39 bus-and-switch §26, §27, §28, §32): after a reading of licence L, when switch_auto is on and
-// L, with one or more consumers bound to it, is at or above switch_at_pct in its session or weekly window, every
-// consumer bound to L moves, in one act, to the other licence with known room whose windows are both below
-// room_below_pct and that has the most room, the first by name on a tie. The act is said as one licence.switched, a
+// L, with one or more consumers bound to it, is at or above switch_at_pct in its weekly window (C4: the session window takes
+// no part), every consumer bound to L moves, in one act, to the other licence with known room whose weekly window is
+// below room_below_pct and that has the most room, the first by name on a tie. The act is said as one licence.switched, a
 // binding.changed per consumer, one audit entry switched, and told to the operator. A consumer is only ever moved off
 // a licence at its threshold, so none flaps between two.
 
@@ -61,24 +61,17 @@ func consumersOf(licence string, bindings []Binding) []string {
 	return consumers
 }
 
-// windowAt is l's window at or above pct, the higher of the two, the session window on a tie (B36): its name,
-// percentage and reset; ok false when neither is.
+// windowAt is l's weekly window when it is at or above pct (C4: the session window takes no part): its name,
+// percentage and reset; ok false when it is not.
 func windowAt(u *UsageReading, pct float64) (window string, at float64, resetsAt string, ok bool) {
-	if u == nil {
+	if u == nil || u.WeeklyPct == nil || *u.WeeklyPct < pct {
 		return "", 0, "", false
 	}
-	session, weekly := u.SessionPct, u.WeeklyPct
-	switch {
-	case session != nil && *session >= pct && (weekly == nil || *session >= *weekly):
-		return "session", *session, u.SessionResetsAt, true
-	case weekly != nil && *weekly >= pct:
-		return "weekly", *weekly, u.WeeklyResetsAt, true
-	}
-	return "", 0, "", false
+	return "weekly", *u.WeeklyPct, u.WeeklyResetsAt, true
 }
 
-// targetFor is the licence §26 moves l's consumers to: among the others with known room whose windows are both below
-// room_below_pct, the one with the most room, the first by name on a tie; empty when none has room.
+// targetFor is the licence §26 moves l's consumers to: among the others with known room whose weekly window is below
+// room_below_pct (C4), the one with the most room, the first by name on a tie; empty when none has room.
 func (m *Manager) targetFor(l Licence, licences []Licence, s Settings) (string, float64) {
 	others := append([]Licence(nil), licences...)
 	sort.Slice(others, func(i, j int) bool { return others[i].Name < others[j].Name })
@@ -88,7 +81,7 @@ func (m *Manager) targetFor(l Licence, licences []Licence, s Settings) (string,
 			continue
 		}
 		room, known := Room(o, m.Now(), s)
-		if !known || *o.Usage.SessionPct >= s.RoomBelow || *o.Usage.WeeklyPct >= s.RoomBelow || room <= best {
+		if !known || *o.Usage.WeeklyPct >= s.RoomBelow || room <= best {
 			continue
 		}
 		best, to = room, o.Name
diff --git a/modules/claude-licence-manager/cmd/claude-licence-manager/switching_test.go b/modules/claude-licence-manager/cmd/claude-licence-manager/switching_test.go
index 3dfa8e8da..40757860a 100644
--- a/modules/claude-licence-manager/cmd/claude-licence-manager/switching_test.go
+++ b/modules/claude-licence-manager/cmd/claude-licence-manager/switching_test.go
@@ -14,11 +14,18 @@ func read(session, weekly float64) *UsageReading {
 		WeeklyResetsAt: "2026-11-14T09:00:00Z", ReadAt: t0.UTC().Format(time.RFC3339Nano)}
 }
 
+// weekly is a reading with no session window, as the vendor answers since the session limit was retired (C4).
+func weekly(pct float64) *UsageReading {
+	u := read(0, pct)
+	u.SessionPct, u.SessionResetsAt = nil, ""
+	return u
+}
+
 func sub(name string, u *UsageReading) Licence {
 	return Licence{Name: name, Kind: "subscription", Generation: 1, Usage: u}
 }
 
-// design 39 bus-and-switch §26/AC1, §25, §48: a table of licences, readings and bindings and the moves each gives.
+// design 39 bus-and-switch §26/AC1, §25, §48, C4: a table of licences, readings and bindings and the moves each gives.
 func TestTheRuleMovesEachTable(t *testing.T) {
 	mm := newMesh(t)
 	on := func(consumers ...string) []Binding {
@@ -41,12 +48,15 @@ func TestTheRuleMovesEachTable(t *testing.T) {
 		{"no consumer", []Licence{sub("a", read(99, 99)), sub("b", read(0, 0))}, nil, "", "", false, 0},
 		{"the weekly window at 99", []Licence{sub("a", read(40, 99)), sub("b", read(10, 30)), sub("c", read(5, 20))},
 			on("x", "y", "z", "w"), "c", "weekly", false, 4},
-		{"the session window at 100", []Licence{sub("a", read(100, 50)), sub("b", read(10, 30))}, on("x"), "b", "session", false, 1},
-		{"a tie goes to the first by name", []Licence{sub("a", read(99, 0)), sub("c", read(10, 10)), sub("b", read(10, 10))},
-			on("x"), "b", "session", false, 1},
-		{"a target's windows both below room_below_pct", []Licence{sub("a", read(99, 0)), sub("b", read(0, 90)),
-			sub("c", read(89, 89))}, on("x"), "c", "session", false, 1},
-		{"no other licence has room", []Licence{sub("a", read(99, 0)), sub("b", read(95, 0)),
+		{"the session window at 100 moves nothing (C4)", []Licence{sub("a", read(100, 50)), sub("b", read(10, 30))},
+			on("x"), "", "", false, 0},
+		{"no session window, weekly 99, to weekly 33 (C4)", []Licence{sub("a", weekly(99)), sub("b", weekly(33))},
+			on("x", "y"), "b", "weekly", false, 2},
+		{"a tie goes to the first by name", []Licence{sub("a", read(0, 99)), sub("c", read(10, 10)), sub("b", read(10, 10))},
+			on("x"), "b", "weekly", false, 1},
+		{"a target's weekly below room_below_pct, its session not counted (C4)", []Licence{sub("a", read(0, 99)),
+			sub("b", read(0, 90)), sub("c", read(95, 89))}, on("x"), "c", "weekly", false, 1},
+		{"no other licence has room", []Licence{sub("a", read(0, 99)), sub("b", read(0, 95)),
 			{Name: "k", Kind: "api-key", Generation: 1}}, on("x"), "", "", true, 0},
 		{"an unread licence is no target", []Licence{sub("a", read(0, 99)), sub("b", nil)}, on("x"), "", "", true, 0},
 	} {
@@ -65,7 +75,7 @@ func TestTheRuleMovesEachTable(t *testing.T) {
 func fourOnA(t *testing.T) *miniMesh {
 	mm := newMesh(t)
 	ctx := context.Background()
-	for _, l := range []Licence{sub("a", read(40, 99)), sub("b", read(30, 20)), sub("c", read(40, 10))} {
+	for _, l := range []Licence{sub("a", read(40, 99)), sub("b", read(30, 30)), sub("c", read(40, 40))} {
 		_ = mm.store.SaveLicence(ctx, l)
 	}
 	for _, c := range []string{"ace", "g14", "laptop", "server"} {
diff --git a/modules/claude-licence-manager/cmd/claude-licence-manager/whole_integration_test.go b/modules/claude-licence-manager/cmd/claude-licence-manager/whole_integration_test.go
index f9c750658..a9606cd64 100644
--- a/modules/claude-licence-manager/cmd/claude-licence-manager/whole_integration_test.go
+++ b/modules/claude-licence-manager/cmd/claude-licence-manager/whole_integration_test.go
@@ -211,13 +211,13 @@ func fillTodaysRows(t *testing.T, conn *pgx.Conn) {
 type vendor struct {
 	mu     sync.Mutex
 	calls  int
-	logins map[string][2]string  // refresh token: the next access token and the account
-	usage  map[string][2]float64 // access token: session and weekly percentages
+	logins map[string][2]string // refresh token: the next access token and the account
+	usage  map[string]float64   // access token: the weekly percentage; the session window is answered empty (C4)
 	server *httptest.Server
 }
 
 func newVendor(t *testing.T) *vendor {
-	v := &vendor{logins: map[string][2]string{}, usage: map[string][2]float64{}}
+	v := &vendor{logins: map[string][2]string{}, usage: map[string]float64{}}
 	v.server = httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		v.mu.Lock()
 		defer v.mu.Unlock()
@@ -240,16 +240,17 @@ func newVendor(t *testing.T) *vendor {
 			return
 		}
 		resets := time.Now().Add(3 * time.Hour).UTC().Format(time.RFC3339)
-		_ = json.NewEncoder(w).Encode(map[string]any{"five_hour": map[string]any{"utilization": u[0], "resets_at": resets},
-			"seven_day": map[string]any{"utilization": u[1], "resets_at": resets}})
+		// As the vendor answers since it retired the session limit: the session window with no utilization (C4).
+		_ = json.NewEncoder(w).Encode(map[string]any{"five_hour": map[string]any{"utilization": nil, "resets_at": nil},
+			"seven_day": map[string]any{"utilization": u, "resets_at": resets}})
 	}))
 	t.Cleanup(v.server.Close)
 	return v
 }
 
-func (v *vendor) set(access string, session, weekly float64) {
+func (v *vendor) set(access string, weekly float64) {
 	v.mu.Lock()
-	v.usage[access] = [2]float64{session, weekly}
+	v.usage[access] = weekly
 	v.mu.Unlock()
 }
 
@@ -1065,8 +1066,8 @@ func TestAReadingAtTheThresholdMovesEveryConsumer(t *testing.T) {
 	m.mu.Lock()
 	carried := m.count("binding.changed")
 	m.mu.Unlock()
-	m.vendor.set("at-b", 10, 20)
-	m.vendor.set("at-a", 99, 50)
+	m.vendor.set("at-b", 20)
+	m.vendor.set("at-a", 99)
 	p.must("licences_read_usage", map[string]any{"licence": licenceB})
 	p.must("licences_read_usage", map[string]any{"licence": licenceA})
 	m.until("the four consumers moved", func() bool { return m.count("binding.changed") >= carried+4 })
@@ -1098,8 +1099,8 @@ func TestAReadingAtTheThresholdMovesEveryConsumer(t *testing.T) {
 
 	// Every licence at its threshold: the consumers have nowhere to go.
 	noRoom := "licence." + KeyFor(licenceB) + ".no-room"
-	m.vendor.set("at-a", 99, 50)
-	m.vendor.set("at-b", 99, 60)
+	m.vendor.set("at-a", 99)
+	m.vendor.set("at-b", 99)
 	p.must("licences_read_usage", map[string]any{"licence": licenceA})
 	p.must("licences_read_usage", map[string]any{"licence": licenceB})
 	m.until("no-room is raised", func() bool { return len(m.conditionsOf(noRoom)) > 0 })
@@ -1110,7 +1111,7 @@ func TestAReadingAtTheThresholdMovesEveryConsumer(t *testing.T) {
 		t.Errorf("no-room said %+v", r)
 	}
 	// A reading with room: the next reading of the full licence moves its consumers, and no-room is cleared.
-	m.vendor.set("at-a", 5, 30)
+	m.vendor.set("at-a", 30)
 	p.must("licences_read_usage", map[string]any{"licence": licenceA})
 	p.must("licences_read_usage", map[string]any{"licence": licenceB})
 	m.until("no-room is cleared", func() bool {
@@ -1159,8 +1160,8 @@ func TestANewLoginIsAdoptedListedAndATarget(t *testing.T) {
 	}
 
 	// The full licence is read first: nothing has room yet, so its consumer stays.
-	m.vendor.set("at-old", 99, 40)
-	m.vendor.set("at-team", 10, 5)
+	m.vendor.set("at-old", 99)
+	m.vendor.set("at-team", 5)
 	p.must("licences_read_usage", map[string]any{"licence": licenceA})
 	p.must("licences_read_usage", map[string]any{"licence": "team@example.org"})
 	var listed []map[string]any
diff --git a/modules/claude-licence-manager/module.json b/modules/claude-licence-manager/module.json
index 4a1a86e16..5d6fe9d52 100644
--- a/modules/claude-licence-manager/module.json
+++ b/modules/claude-licence-manager/module.json
@@ -186,13 +186,13 @@
     },
     "switch_auto": {
       "type": "boolean",
-      "description": "Whether the manager moves every consumer off a licence whose session or weekly usage reaches switch_at_pct, to the licence with the most room; off, it still raises its no-room and near-limit conditions.",
+      "description": "Whether the manager moves every consumer off a licence whose weekly usage reaches switch_at_pct, to the licence with the most room; off, it still raises its no-room and near-limit conditions.",
       "trusted": true,
       "default": true
     },
     "switch_at_pct": {
       "type": "number",
-      "description": "The session or weekly usage of a licence, in percent, at which its consumers are moved to the licence with the most room.",
+      "description": "The weekly usage of a licence, in percent, at which its consumers are moved to the licence with the most room.",
       "minimum": 1,
       "maximum": 100,
       "trusted": true,
@@ -200,7 +200,7 @@
     },
     "room_below_pct": {
       "type": "number",
-      "description": "What both the session and the weekly usage of a licence must be below, in percent, for it to be a target of a switch.",
+      "description": "What the weekly usage of a licence must be below, in percent, for it to be a target of a switch.",
       "minimum": 1,
       "maximum": 100,
       "trusted": true,
@@ -208,7 +208,7 @@
     },
     "warn_at_pct": {
       "type": "number",
-      "description": "The session or weekly usage of a licence with consumers, in percent, at which it is warned about once.",
+      "description": "The weekly usage of a licence with consumers, in percent, at which it is warned about once.",
       "minimum": 1,
       "maximum": 100,
       "trusted": true,