diff --git a/internal/cli/app.go b/internal/cli/app.go
index 207048b..e1b1f91 100644
--- a/internal/cli/app.go
+++ b/internal/cli/app.go
@@ -108,7 +108,7 @@ func (a *App) handleInput(text string) {
 	})
 	if err != nil {
 		a.ui.AddStatus(
-			"[red]Send error: " + err.Error(),
+			"[red]Send error: " + escape(err.Error()),
 		)
 	}
 }
@@ -166,7 +166,7 @@ func (a *App) dispatchInfoCommand(cmd, args string) {
 		a.cmdWhois(args)
 	default:
 		a.ui.AddStatus(
-			"[red]Unknown command: " + cmd,
+			"[red]Unknown command: " + escape(cmd),
 		)
 	}
 }
@@ -182,7 +182,7 @@ func (a *App) cmdConnect(serverURL string) {
 
 	serverURL = strings.TrimRight(serverURL, "/")
 
-	a.ui.AddStatus("Connecting to " + serverURL + "...")
+	a.ui.AddStatus("Connecting to " + escape(serverURL) + "...")
 
 	a.mu.Lock()
 	nick := a.nick
@@ -192,9 +192,9 @@ func (a *App) cmdConnect(serverURL string) {
 
 	resp, err := client.CreateSession(nick)
 	if err != nil {
-		a.ui.AddStatus(fmt.Sprintf(
-			"[red]Connection failed: %v", err,
-		))
+		a.ui.AddStatus(
+			"[red]Connection failed: " + escape(err.Error()),
+		)
 
 		return
 	}
@@ -218,7 +218,7 @@ func (a *App) cmdConnect(serverURL string) {
 
 	a.ui.AddStatus(fmt.Sprintf(
 		"[green]Connected! Nick: %s, Session: %d",
-		resp.Nick, resp.ID,
+		escape(resp.Nick), resp.ID,
 	))
 	a.ui.SetStatus(resp.Nick, "", "connected")
 
@@ -244,7 +244,7 @@ func (a *App) cmdNick(nick string) {
 		a.mu.Unlock()
 
 		a.ui.AddStatus(
-			"Nick set to " + nick +
+			"Nick set to " + escape(nick) +
 				" (will be used on connect)",
 		)
 
@@ -256,9 +256,9 @@ func (a *App) cmdNick(nick string) {
 		Body:    []string{nick},
 	})
 	if err != nil {
-		a.ui.AddStatus(fmt.Sprintf(
-			"[red]Nick change failed: %v", err,
-		))
+		a.ui.AddStatus(
+			"[red]Nick change failed: " + escape(err.Error()),
+		)
 
 		return
 	}
@@ -269,7 +269,7 @@ func (a *App) cmdNick(nick string) {
 	a.mu.Unlock()
 
 	a.ui.SetStatus(nick, target, "connected")
-	a.ui.AddStatus("Nick changed to " + nick)
+	a.ui.AddStatus("Nick changed to " + escape(nick))
 }
 
 func (a *App) cmdJoin(channel string) {
@@ -297,9 +297,9 @@ func (a *App) cmdJoin(channel string) {
 
 	err := a.client.JoinChannel(channel)
 	if err != nil {
-		a.ui.AddStatus(fmt.Sprintf(
-			"[red]Join failed: %v", err,
-		))
+		a.ui.AddStatus(
+			"[red]Join failed: " + escape(err.Error()),
+		)
 
 		return
 	}
@@ -337,9 +337,9 @@ func (a *App) cmdPart(channel string) {
 
 	err := a.client.PartChannel(channel)
 	if err != nil {
-		a.ui.AddStatus(fmt.Sprintf(
-			"[red]Part failed: %v", err,
-		))
+		a.ui.AddStatus(
+			"[red]Part failed: " + escape(err.Error()),
+		)
 
 		return
 	}
@@ -384,9 +384,9 @@ func (a *App) cmdMsg(args string) {
 		Body:    []string{text},
 	})
 	if err != nil {
-		a.ui.AddStatus(fmt.Sprintf(
-			"[red]Send failed: %v", err,
-		))
+		a.ui.AddStatus(
+			"[red]Send failed: " + escape(err.Error()),
+		)
 	}
 }
 
@@ -439,9 +439,9 @@ func (a *App) cmdTopic(args string) {
 		Body:    []string{args},
 	})
 	if err != nil {
-		a.ui.AddStatus(fmt.Sprintf(
-			"[red]Topic set failed: %v", err,
-		))
+		a.ui.AddStatus(
+			"[red]Topic set failed: " + escape(err.Error()),
+		)
 	}
 }
 
@@ -465,9 +465,9 @@ func (a *App) cmdNames() {
 
 	members, err := a.client.GetMembers(target)
 	if err != nil {
-		a.ui.AddStatus(fmt.Sprintf(
-			"[red]Names failed: %v", err,
-		))
+		a.ui.AddStatus(
+			"[red]Names failed: " + escape(err.Error()),
+		)
 
 		return
 	}
@@ -480,7 +480,7 @@ func (a *App) cmdNames() {
 
 	a.ui.AddLine(target, fmt.Sprintf(
 		"[cyan]*** Members of %s: %s",
-		target, strings.Join(nicks, " "),
+		escape(target), escape(strings.Join(nicks, " ")),
 	))
 }
 
@@ -511,9 +511,9 @@ func (a *App) cmdList() {
 
 	channels, err := a.client.ListChannels()
 	if err != nil {
-		a.ui.AddStatus(fmt.Sprintf(
-			"[red]List failed: %v", err,
-		))
+		a.ui.AddStatus(
+			"[red]List failed: " + escape(err.Error()),
+		)
 
 		return
 	}
@@ -522,7 +522,7 @@ func (a *App) cmdList() {
 
 	for _, ch := range channels {
 		a.ui.AddStatus(fmt.Sprintf(
-			"  %s %s", ch.Name, ch.Topic,
+			"  %s %s", escape(ch.Name), escape(ch.Topic),
 		))
 	}
 
@@ -544,9 +544,9 @@ func (a *App) cmdMotd() {
 		&api.Message{Command: irc.CmdMotd}, //nolint:exhaustruct
 	)
 	if err != nil {
-		a.ui.AddStatus(fmt.Sprintf(
-			"[red]MOTD failed: %v", err,
-		))
+		a.ui.AddStatus(
+			"[red]MOTD failed: " + escape(err.Error()),
+		)
 	}
 }
 
@@ -582,9 +582,9 @@ func (a *App) cmdWho(args string) {
 		},
 	)
 	if err != nil {
-		a.ui.AddStatus(fmt.Sprintf(
-			"[red]WHO failed: %v", err,
-		))
+		a.ui.AddStatus(
+			"[red]WHO failed: " + escape(err.Error()),
+		)
 	}
 }
 
@@ -613,9 +613,9 @@ func (a *App) cmdWhois(args string) {
 		},
 	)
 	if err != nil {
-		a.ui.AddStatus(fmt.Sprintf(
-			"[red]WHOIS failed: %v", err,
-		))
+		a.ui.AddStatus(
+			"[red]WHOIS failed: " + escape(err.Error()),
+		)
 	}
 }
 
@@ -818,7 +818,7 @@ func (a *App) handlePrivmsgEvent(
 
 	a.ui.AddLine(target, fmt.Sprintf(
 		"[gray]%s [green]<%s>[white] %s",
-		timestamp, msg.From, text,
+		timestamp, escape(msg.From), escape(text),
 	))
 }
 
@@ -831,7 +831,7 @@ func (a *App) handleJoinEvent(
 
 	a.ui.AddLine(msg.To, fmt.Sprintf(
 		"[gray]%s [yellow]*** %s has joined %s",
-		timestamp, msg.From, msg.To,
+		timestamp, escape(msg.From), escape(msg.To),
 	))
 }
 
@@ -850,11 +850,11 @@ func (a *App) handlePartEvent(
 
 	line := fmt.Sprintf(
 		"[gray]%s [yellow]*** %s has left %s",
-		timestamp, msg.From, msg.To,
+		timestamp, escape(msg.From), escape(msg.To),
 	)
 
 	if reason != "" {
-		line += " (" + reason + ")"
+		line += " (" + escape(reason) + ")"
 	}
 
 	if msg.From == myNick {
@@ -875,12 +875,12 @@ func (a *App) handleQuitEvent(
 	if reason != "" {
 		a.ui.AddStatus(fmt.Sprintf(
 			"[gray]%s [yellow]*** %s has quit (%s)",
-			timestamp, msg.From, reason,
+			timestamp, escape(msg.From), escape(reason),
 		))
 	} else {
 		a.ui.AddStatus(fmt.Sprintf(
 			"[gray]%s [yellow]*** %s has quit",
-			timestamp, msg.From,
+			timestamp, escape(msg.From),
 		))
 	}
 }
@@ -907,7 +907,7 @@ func (a *App) handleNickEvent(
 
 	a.ui.AddStatus(fmt.Sprintf(
 		"[gray]%s [yellow]*** %s is now known as %s",
-		timestamp, msg.From, newNick,
+		timestamp, escape(msg.From), escape(newNick),
 	))
 }
 
@@ -919,7 +919,7 @@ func (a *App) handleNoticeEvent(
 
 	a.ui.AddStatus(fmt.Sprintf(
 		"[gray]%s [magenta]--%s-- %s",
-		timestamp, msg.From, text,
+		timestamp, escape(msg.From), escape(text),
 	))
 }
 
@@ -935,7 +935,7 @@ func (a *App) handleTopicEvent(
 
 	a.ui.AddLine(msg.To, fmt.Sprintf(
 		"[gray]%s [cyan]*** %s set topic: %s",
-		timestamp, msg.From, text,
+		timestamp, escape(msg.From), escape(text),
 	))
 }
 
@@ -945,10 +945,12 @@ func (a *App) handleDefaultEvent(
 	lines := msg.BodyLines()
 	text := strings.Join(lines, " ")
 
+	// The brackets around the command are escaped with it, as tview
+	// reads a command such as "[MODE]" as a tag.
 	if text != "" {
 		a.ui.AddStatus(fmt.Sprintf(
-			"[gray]%s [white][%s] %s",
-			timestamp, msg.Command, text,
+			"[gray]%s [white]%s %s",
+			timestamp, escape("["+msg.Command+"]"), escape(text),
 		))
 	}
 }
diff --git a/internal/cli/app_internal_test.go b/internal/cli/app_internal_test.go
index 679e67e..0ef43d7 100644
--- a/internal/cli/app_internal_test.go
+++ b/internal/cli/app_internal_test.go
@@ -8,6 +8,7 @@ import (
 	"strings"
 	"testing"
 	"time"
+	"unicode/utf8"
 
 	"github.com/gdamore/tcell/v2"
 	api "sneak.berlin/go/neoirc/internal/cli/api"
@@ -845,6 +846,109 @@ func TestOwnEventFromOtherClient(t *testing.T) {
 	}
 }
 
+// TestBracketsInMessageWindow checks that each kind of line drawn
+// from a server event shows nicks, texts, reasons and topics
+// holding square brackets as written.
+func TestBracketsInMessageWindow(t *testing.T) {
+	t.Parallel()
+
+	// Every event is sent to the channel and has a body of one line.
+	tests := []struct {
+		name    string
+		command string
+		from    string
+		body    string
+		// Whether the line goes to the channel's window rather than
+		// the status window, which is the one shown at start.
+		inChannel bool
+		// How the line ends, after the timestamps.
+		want string
+	}{
+		{
+			name: "message", command: irc.CmdPrivmsg, inChannel: true,
+			from: "bob[|[]", body: "x[^[] [:::y|z] [red]",
+			want: "<bob[|[]> x[^[] [:::y|z] [red]",
+		},
+		{
+			name: "joined", command: irc.CmdJoin, from: "x[^[]", inChannel: true,
+			want: "*** x[^[] has joined #chan",
+		},
+		{
+			name: "left", command: irc.CmdPart, inChannel: true,
+			from: "erin[away]", body: "[:::y|z]",
+			want: "*** erin[away] has left #chan ([:::y|z])",
+		},
+		{
+			name: "topic", command: irc.CmdTopic, inChannel: true,
+			from: "dave[afk]", body: "[red]news",
+			want: "*** dave[afk] set topic: [red]news",
+		},
+		{
+			name: "quit", command: irc.CmdQuit, from: "carol[x]", body: "bye [red]",
+			want: "*** carol[x] has quit (bye [red])",
+		},
+		{
+			name: "nick change", command: irc.CmdNick, from: "erin[m]", body: "erin[x]",
+			want: "*** erin[m] is now known as erin[x]",
+		},
+		{
+			name: "notice", command: irc.CmdNotice, from: "bob[]", body: "[::b]note",
+			want: "--bob[]-- [::b]note",
+		},
+		{
+			name: "other command", command: irc.CmdMode, body: "+v dave[afk]",
+			want: "[MODE] +v dave[afk]",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
+
+			app := &App{ui: NewUI(), nick: testNick}
+			screen := runUI(t, app.ui)
+
+			if test.inChannel {
+				app.ui.SwitchToBuffer(testChannel)
+			}
+
+			app.handleServerMessage(&api.Message{
+				Command: test.command, From: test.from, To: testChannel,
+				Body: []string{test.body},
+			})
+
+			got, _ := shownLine(app.ui, screen)
+			if !strings.HasSuffix(got, test.want) {
+				t.Fatalf("message window shows %q, want it to end %q", got, test.want)
+			}
+		})
+	}
+}
+
+// TestColourTagInMessage checks that a colour tag in a message
+// shows as written and leaves the message text white, as the
+// client draws it.
+func TestColourTagInMessage(t *testing.T) {
+	t.Parallel()
+
+	const want = "<bob> [red]x"
+
+	app := &App{ui: NewUI(), nick: testNick}
+	screen := runUI(t, app.ui)
+	app.ui.SwitchToBuffer(testChannel)
+
+	app.handleServerMessage(&api.Message{
+		Command: irc.CmdPrivmsg, From: testOtherNick, To: testChannel,
+		Body: []string{"[red]x"},
+	})
+
+	got, colour := shownLine(app.ui, screen)
+	if !strings.HasSuffix(got, want) || colour != tcell.ColorWhite {
+		t.Fatalf("message window shows %q, its last character in %v; "+
+			"want it to end %q, in white", got, colour, want)
+	}
+}
+
 // bufferState returns the number of lines in the named
 // buffer and how many of them are unread.
 func bufferState(ui *UI, name string) (int, int) {
@@ -872,6 +976,39 @@ func statusBarText(ui *UI) string {
 	return text
 }
 
+// shownLine returns the first line of the message window as the
+// screen shows it, without the blanks after it, and the colour of
+// its last character.
+func shownLine(
+	ui *UI, screen tcell.SimulationScreen,
+) (string, tcell.Color) {
+	var (
+		text   string
+		colour tcell.Color
+	)
+
+	ui.app.QueueUpdate(func() {
+		cells, width, _ := screen.GetContents()
+
+		var row strings.Builder
+
+		for _, cell := range cells[:width] {
+			row.WriteString(string(cell.Runes))
+		}
+
+		text = strings.TrimRight(row.String(), " ")
+		if text == "" {
+			return
+		}
+
+		// Each character in these tests takes one cell.
+		last := cells[utf8.RuneCountInString(text)-1]
+		colour, _, _ = last.Style.Decompose()
+	})
+
+	return text, colour
+}
+
 // handledLines makes app.ui pass each typed line to
 // app.handleInput, as Run does, and returns a channel that
 // receives each line once it has been handled.
@@ -964,11 +1101,15 @@ func waitPoll(t *testing.T, polled <-chan struct{}, server string) {
 	}
 }
 
-// runUI runs ui on a simulated screen until the test ends.
-func runUI(t *testing.T, ui *UI) {
+// runUI runs ui on a simulated screen until the test ends, and
+// returns the screen.
+//
+//nolint:ireturn // tcell has no exported type for the screen
+func runUI(t *testing.T, ui *UI) tcell.SimulationScreen {
 	t.Helper()
 
-	ui.app.SetScreen(tcell.NewSimulationScreen(""))
+	screen := tcell.NewSimulationScreen("")
+	ui.app.SetScreen(screen)
 
 	// One slot, so that Run's goroutine can end even after the
 	// cleanup below has stopped waiting for it.
@@ -988,4 +1129,6 @@ func runUI(t *testing.T, ui *UI) {
 			t.Error("the UI did not stop: its event loop stopped responding")
 		}
 	})
+
+	return screen
 }
diff --git a/internal/cli/ui.go b/internal/cli/ui.go
index 6f229df..80708a6 100644
--- a/internal/cli/ui.go
+++ b/internal/cli/ui.go
@@ -235,6 +235,16 @@ func (ui *UI) initMessages() {
 	ui.messages.SetBorder(false)
 }
 
+// escape returns text so that the message window shows it exactly
+// as written. It writes each "[" as "[[:]": a "[" followed by
+// another "[" never starts a tag, and the tag "[:]" changes
+// nothing. tview.Escape is not enough: it does not escape a bracket
+// pair holding a symbol such as "|" or "^", and nothing it adds
+// stops a tag with a URL, such as "[:::y|z]".
+func escape(text string) string {
+	return strings.ReplaceAll(text, "[", "[[:]")
+}
+
 func (ui *UI) initStatusBar() {
 	// Colour tags stay off. With them on, tview reads text in
 	// square brackets, such as "[connected]" or part of a nick,