diff --git a/internal/tui/model.go b/internal/tui/model.go
index 4299d73..ffe4e1a 100644
--- a/internal/tui/model.go
+++ b/internal/tui/model.go
@@ -4,13 +4,13 @@ import (
 	"fmt"
 	"time"
 
+	"git.ryuvia.com/niklas/terdut-tui/internal/api"
 	"github.com/charmbracelet/bubbles/help"
 	"github.com/charmbracelet/bubbles/table"
 	"github.com/charmbracelet/bubbles/textinput"
 	"github.com/charmbracelet/bubbles/viewport"
 	tea "github.com/charmbracelet/bubbletea"
 	"github.com/charmbracelet/lipgloss"
-	"git.ryuvia.com/niklas/terdut-tui/internal/api"
 )
 
 // ── Enums ──────────────────────────────────────────────────────────────────
@@ -354,27 +354,45 @@ func defaultTableStyles() table.Styles {
 	return s
 }
 
+// setRows replaces a table's rows and keeps its cursor in a state the rest of
+// this package can rely on: valid whenever the table has any rows at all.
+//
+// bubbles does not do that on its own. SetRows only clamps the cursor *down*
+// (`if m.cursor > len(rows)-1`), so setting zero rows drives it to -1 and
+// nothing ever brings it back — filling the table later leaves -1 in place,
+// because -1 is not greater than len-1. Every table here is rebuilt from empty
+// once at startup, when the first WindowSizeMsg arrives before any fetch has
+// returned, so without this every cursor is -1 until the user happens to press
+// up or down. Indexing a slice with that panics, which is exactly what
+// assigning an on-call week did.
+func setRows(t *table.Model, rows []table.Row) {
+	t.SetRows(rows)
+	if len(rows) > 0 && t.Cursor() < 0 {
+		t.SetCursor(0)
+	}
+}
+
 func (m *Model) rebuildIncidentTable() {
 	m.incidentTable.SetColumns(incidentColumns(m.width))
-	m.incidentTable.SetRows(incidentRows(m.incidents))
+	setRows(&m.incidentTable, incidentRows(m.incidents))
 	m.incidentTable.SetHeight(tableHeight(m.height, 8))
 }
 
 func (m *Model) rebuildTable() {
 	m.alertTable.SetColumns(alertColumns(m.width))
-	m.alertTable.SetRows(alertRows(m.alerts))
+	setRows(&m.alertTable, alertRows(m.alerts))
 	m.alertTable.SetHeight(tableHeight(m.height, 8))
 }
 
 func (m *Model) rebuildArchivedTable() {
 	m.archivedTable.SetColumns(incidentColumns(m.width))
-	m.archivedTable.SetRows(incidentRows(m.archivedIncidents))
+	setRows(&m.archivedTable, incidentRows(m.archivedIncidents))
 	m.archivedTable.SetHeight(tableHeight(m.height, 8))
 }
 
 func (m *Model) rebuildScheduleTable() {
 	m.scheduleTable.SetColumns(scheduleColumns(m.width))
-	m.scheduleTable.SetRows(scheduleRows(m.scheduleDays))
+	setRows(&m.scheduleTable, scheduleRows(m.scheduleDays))
 	m.scheduleTable.SetHeight(tableHeight(m.height, 10))
 }
 
@@ -384,7 +402,7 @@ func (m *Model) rebuildUserPickerTable() {
 	for i, u := range m.users {
 		rows[i] = table.Row{u.Username, u.Email}
 	}
-	m.userPickerTable.SetRows(rows)
+	setRows(&m.userPickerTable, rows)
 	m.userPickerTable.SetHeight(tableHeight(m.height, 10))
 }
 
@@ -398,7 +416,7 @@ func (m *Model) rebuildUserManageTable() {
 		}
 		rows[i] = table.Row{u.Username, u.Email, topic, u.CreatedAt.UTC().Format("2006-01-02")}
 	}
-	m.userManageTable.SetRows(rows)
+	setRows(&m.userManageTable, rows)
 	m.userManageTable.SetHeight(tableHeight(m.height, 10))
 }
 
diff --git a/internal/tui/model_test.go b/internal/tui/model_test.go
index 2cec137..8c9cb9a 100644
--- a/internal/tui/model_test.go
+++ b/internal/tui/model_test.go
@@ -4,8 +4,8 @@ import (
 	"testing"
 	"time"
 
-	"github.com/charmbracelet/bubbles/table"
 	"git.ryuvia.com/niklas/terdut-tui/internal/api"
+	"github.com/charmbracelet/bubbles/table"
 )
 
 func TestNextFilter(t *testing.T) {
diff --git a/internal/tui/styles.go b/internal/tui/styles.go
index f3a1eae..ea52c17 100644
--- a/internal/tui/styles.go
+++ b/internal/tui/styles.go
@@ -3,8 +3,8 @@ package tui
 import (
 	"strings"
 
-	"github.com/charmbracelet/lipgloss"
 	"git.ryuvia.com/niklas/terdut-tui/internal/api"
+	"github.com/charmbracelet/lipgloss"
 )
 
 var (
diff --git a/internal/tui/update.go b/internal/tui/update.go
index d8712a3..1c38aba 100644
--- a/internal/tui/update.go
+++ b/internal/tui/update.go
@@ -4,10 +4,10 @@ import (
 	"strconv"
 	"strings"
 
+	"git.ryuvia.com/niklas/terdut-tui/internal/api"
 	"github.com/atotto/clipboard"
 	"github.com/charmbracelet/bubbles/viewport"
 	tea "github.com/charmbracelet/bubbletea"
-	"git.ryuvia.com/niklas/terdut-tui/internal/api"
 )
 
 func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
@@ -468,7 +468,7 @@ func (m Model) handleDashboardKey(msg tea.KeyMsg) (Model, tea.Cmd) {
 				return m, nil
 			}
 			cursor := m.scheduleTable.Cursor()
-			if cursor >= len(m.scheduleDays) {
+			if cursor < 0 || cursor >= len(m.scheduleDays) {
 				return m, nil
 			}
 			day := m.scheduleDays[cursor]
@@ -484,7 +484,7 @@ func (m Model) handleDashboardKey(msg tea.KeyMsg) (Model, tea.Cmd) {
 				return m, nil
 			}
 			cursor := m.userManageTable.Cursor()
-			if cursor >= len(m.users) {
+			if cursor < 0 || cursor >= len(m.users) {
 				return m, nil
 			}
 			m.selectedUser = m.users[cursor]
@@ -510,7 +510,7 @@ func (m Model) handleDashboardKey(msg tea.KeyMsg) (Model, tea.Cmd) {
 			return m, nil
 		}
 		cursor := m.userManageTable.Cursor()
-		if cursor >= len(m.users) {
+		if cursor < 0 || cursor >= len(m.users) {
 			return m, nil
 		}
 		m.selectedUser = m.users[cursor]
@@ -527,7 +527,7 @@ func (m Model) handleDashboardKey(msg tea.KeyMsg) (Model, tea.Cmd) {
 			return m, nil
 		}
 		cursor := m.userManageTable.Cursor()
-		if cursor >= len(m.users) {
+		if cursor < 0 || cursor >= len(m.users) {
 			return m, nil
 		}
 		m.selectedUser = m.users[cursor]
@@ -893,7 +893,7 @@ func (m Model) handleUserPickerKey(msg tea.KeyMsg) (Model, tea.Cmd) {
 		}
 
 		scheduleCursor := m.scheduleTable.Cursor()
-		if scheduleCursor >= len(m.scheduleDays) {
+		if scheduleCursor < 0 || scheduleCursor >= len(m.scheduleDays) {
 			m.mode = modeDashboard
 			return m, nil
 		}
diff --git a/internal/tui/update_test.go b/internal/tui/update_test.go
index acc2e9a..1091aac 100644
--- a/internal/tui/update_test.go
+++ b/internal/tui/update_test.go
@@ -5,8 +5,8 @@ import (
 	"testing"
 	"time"
 
-	tea "github.com/charmbracelet/bubbletea"
 	"git.ryuvia.com/niklas/terdut-tui/internal/api"
+	tea "github.com/charmbracelet/bubbletea"
 )
 
 // press sends one key and returns the resulting model and command. A nil command
@@ -676,3 +676,50 @@ func containsAll(s string, subs ...string) bool {
 	}
 	return true
 }
+
+// The bug: assigning an on-call week panicked with "index out of range [-1]"
+// on a perfectly normal schedule, as long as nobody had moved the cursor first.
+//
+// The cause is not in this package. bubbles' SetRows clamps the cursor down but
+// never up, so the empty rebuild every table gets from the first WindowSizeMsg
+// -- which arrives before any fetch returns -- pins the cursor at -1, and
+// loading real rows afterwards leaves it there. Pressing up or down hid it,
+// which is why every existing test missed it: they all call SetCursor, and
+// SetCursor clamps.
+//
+// So this test must NOT touch the cursor. It reproduces the real order of
+// events: size first, data second, keys third.
+func TestSchedule_AssignWeekAfterStartupSizingDoesNotPanic(t *testing.T) {
+	m := NewModel(nil, "http://test", time.Minute)
+	m.connected = true
+	m.activeSection = sectionSchedule
+	m.scheduleWindow = time.Date(2026, 7, 27, 0, 0, 0, 0, time.UTC)
+
+	// 1. Terminal size arrives while every table is still empty.
+	next, _ := m.Update(tea.WindowSizeMsg{Width: 120, Height: 40})
+	m = next.(Model)
+
+	// 2. The schedule and the user list land.
+	next, _ = m.Update(scheduleFetchedMsg{entries: []api.ScheduleEntry{}})
+	m = next.(Model)
+	next, _ = m.Update(usersFetchedMsg{users: []api.User{
+		{ID: 1, Username: "niklas", Email: "n@example.com"},
+	}})
+	m = next.(Model)
+
+	if got := m.scheduleTable.Cursor(); got < 0 {
+		t.Fatalf("schedule cursor is %d after loading %d days; a populated table must have a usable cursor",
+			got, len(m.scheduleDays))
+	}
+
+	// 3. Assign the week to the first user, without ever moving a cursor.
+	m, _ = press(t, m, "W")
+	if m.mode != modeUserPicker {
+		t.Fatalf("W did not open the user picker, got mode %v", m.mode)
+	}
+	m, _ = press(t, m, "enter") // panicked here
+
+	if m.mode == modeUserPicker {
+		t.Fatal("enter left the picker open; the assignment never went anywhere")
+	}
+}
diff --git a/internal/tui/view.go b/internal/tui/view.go
index 378b844..452bc37 100644
--- a/internal/tui/view.go
+++ b/internal/tui/view.go
@@ -6,8 +6,8 @@ import (
 	"strings"
 	"time"
 
-	"github.com/charmbracelet/lipgloss"
 	"git.ryuvia.com/niklas/terdut-tui/internal/api"
+	"github.com/charmbracelet/lipgloss"
 )
 
 // Order must match the section constants — renderTabs indexes this by ordinal.
diff --git a/internal/tui/view_test.go b/internal/tui/view_test.go
index f2570a0..ff74968 100644
--- a/internal/tui/view_test.go
+++ b/internal/tui/view_test.go
@@ -6,8 +6,8 @@ import (
 	"testing"
 	"time"
 
-	tea "github.com/charmbracelet/bubbletea"
 	"git.ryuvia.com/niklas/terdut-tui/internal/api"
+	tea "github.com/charmbracelet/bubbletea"
 )
 
 // ansi matches the escape sequences lipgloss emits when it decides the output
diff --git a/main.go b/main.go
index 57e4678..7adab91 100644
--- a/main.go
+++ b/main.go
@@ -5,11 +5,11 @@ import (
 	"fmt"
 	"os"
 
-	tea "github.com/charmbracelet/bubbletea"
 	"git.ryuvia.com/niklas/terdut-tui/internal/api"
 	"git.ryuvia.com/niklas/terdut-tui/internal/config"
 	"git.ryuvia.com/niklas/terdut-tui/internal/tui"
 	"git.ryuvia.com/niklas/terdut-tui/internal/updater"
+	tea "github.com/charmbracelet/bubbletea"
 )
 
 var version = "dev"