Harden TUI transcript scroll and pin reporting

go/tui/internal/protocol/commands_test.go

@@ -1257,6 +1257,35 @@ func TestDecodeAgentChatSkipsRetiredMessagesSection(t *testing.T) {
 	}
 }
 
+func TestDecodeAgentChatInputFocusedSectionRoundTripAndDefault(t *testing.T) {
+	for _, test := range []struct {
+		name     string
+		sections [][]byte
+		want     bool
+	}{
+		{name: "focused", sections: [][]byte{section(0x01, []byte{1, 0}), section(0x09, []byte{1})}, want: true},
+		{name: "not focused", sections: [][]byte{section(0x01, []byte{1, 0}), section(0x09, []byte{0})}, want: false},
+		{name: "absent defaults false", sections: [][]byte{section(0x01, []byte{1, 0})}, want: false},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			payload := []byte{generated.OPGuiAgentChat, byte(len(test.sections))}
+			for _, encoded := range test.sections {
+				payload = append(payload, encoded...)
+			}
+			command, err := DecodeCommand(payload)
+			if err != nil {
+				t.Fatalf("DecodeCommand returned error: %v", err)
+			}
+			if command.Size != len(payload) {
+				t.Fatalf("consumed = %d, want %d", command.Size, len(payload))
+			}
+			if got := command.Chrome.AgentChat.InputFocused; got != test.want {
+				t.Fatalf("InputFocused = %v, want %v", got, test.want)
+			}
+		})
+	}
+}
+
 func TestDecodeAgentTimelineChrome(t *testing.T) {
 	timelinePayload := []byte{1, 0xFF, 0xFF, 1, 3}
 	timelinePayload = append(timelinePayload, string8("apply_patch")...)

go/tui/internal/protocol/events_test.go

@@ -135,6 +135,24 @@ func TestEncodeGUIFloatPopupDismiss(t *testing.T) {
 	}
 }
 
+func TestEncodeGUIChatPinTransitions(t *testing.T) {
+	tests := []struct {
+		name string
+		got  []byte
+		want []byte
+	}{
+		{"scrolled away", EncodeGUIChatScrolledAwayFromBottom(), []byte{generated.OPGuiAction, generated.GUIActionChatScrolledAwayFromBottom}},
+		{"returned", EncodeGUIChatReturnedToBottom(), []byte{generated.OPGuiAction, generated.GUIActionChatReturnedToBottom}},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			if !bytes.Equal(test.got, test.want) {
+				t.Fatalf("packet = %v, want %v", test.got, test.want)
+			}
+		})
+	}
+}
+
 func TestEncodeScrollBatchDown(t *testing.T) {
 	got := EncodeScrollBatch(42, 3, 0)
 	want := []byte{generated.OPScrollBatch, 0, 42, 0, 3, 0}

go/tui/internal/ui/agent_chat_panel.go

@@ -154,13 +154,7 @@ func agentColumnGap() int {
 func (m Model) renderAgentMainColumn(chat protocol.AgentChat, width int, budget int, empty bool) []string {
 	lines := make([]string, 0, budget)
 	composer := m.renderAgentComposer(chat, width)
-	composerHeight := min(len(composer), max(budget, 0))
-	transcriptBudget := max(budget-composerHeight, 0)
-	statusHeight := 0
-	if transcriptBudget >= 4 {
-		statusHeight = 1
-	}
-	contentBudget := max(transcriptBudget-statusHeight, 0)
+	composerHeight, statusHeight, contentBudget, messageBudget := agentMainColumnBudgets(chat, len(composer), budget)
 	messageCount := len(m.agentTranscriptMessages())
 	sparse := messageCount <= 1 && chat.Pending == "" && strings.TrimSpace(chat.Prompt) == ""
 	if chat.Pending != "" && len(lines) < contentBudget {
@@ -171,7 +165,7 @@ func (m Model) renderAgentMainColumn(chat protocol.AgentChat, width int, budget
 		lines = append(lines, m.renderAgentTranscriptHeader(width))
 	}
 
-	messageLines := m.renderAgentResidentTranscript(max(contentBudget-len(lines), 0), width)
+	messageLines := m.renderAgentResidentTranscript(messageBudget, width)
 	lines = append(lines, messageLines...)
 
 	if empty && len(lines) < contentBudget {
@@ -190,6 +184,39 @@ func (m Model) renderAgentMainColumn(chat protocol.AgentChat, width int, budget
 	return takeLines(lines, budget)
 }
 
+func agentMainColumnBudgets(chat protocol.AgentChat, composerRows int, budget int) (composerHeight int, statusHeight int, contentBudget int, messageBudget int) {
+	composerHeight = min(composerRows, max(budget, 0))
+	transcriptBudget := max(budget-composerHeight, 0)
+	if transcriptBudget >= 4 {
+		statusHeight = 1
+	}
+	contentBudget = max(transcriptBudget-statusHeight, 0)
+	chromeRows := 1
+	if chat.Pending != "" {
+		chromeRows++
+	}
+	messageBudget = max(contentBudget-chromeRows, 0)
+	return composerHeight, statusHeight, contentBudget, messageBudget
+}
+
+func (m Model) agentTranscriptPageSize() int {
+	chat, ok := m.agentChat()
+	if !ok {
+		return 1
+	}
+	limit := m.bodyHeight()
+	panelWidth := max(m.width-2, 1)
+	mainWidth := panelWidth
+	if agentDetailsVisible(panelWidth) && limit > 5 {
+		detailWidth := agentDetailsWidth(panelWidth)
+		mainWidth = max(panelWidth-detailWidth-agentColumnGap(), 40)
+	}
+	mainBudget := max(limit-1, 0)
+	composerRows := len(m.renderAgentComposer(chat, mainWidth))
+	_, _, _, messageBudget := agentMainColumnBudgets(chat, composerRows, mainBudget)
+	return max(messageBudget, 1)
+}
+
 func (m Model) renderAgentBlankLine(width int) string {
 	p := m.palette()
 	return lipgloss.NewStyle().Background(p.AgentPanel()).Width(width).Render(strings.Repeat(" ", max(width, 1)))
@@ -210,6 +237,12 @@ func (m Model) renderAgentTranscriptHeader(width int) string {
 	return lipgloss.NewStyle().Background(p.AgentPanel()).Width(width).Render(fitStyled(label+rule, width))
 }
 
+func (m Model) renderAgentEarlierMessagesHidden(width int) string {
+	p := m.palette()
+	label := " earlier messages hidden "
+	return lipgloss.NewStyle().Foreground(p.Muted()).Background(p.AgentPanel()).Width(width).Align(lipgloss.Center).Render(fit(label, width))
+}
+
 func (m Model) renderAgentTranscriptStatus(chat protocol.AgentChat, width int) string {
 	p := m.palette()
 	messageCount := len(m.agentTranscriptMessages())
@@ -518,7 +551,7 @@ func (m Model) renderAgentNotice(label string, text string, width int) string {
 // agentTranscriptMessages is the transcript rendering source: the resident 0x86
 // store (#2654).
 func (m Model) agentTranscriptMessages() []protocol.AgentChatMessage {
-	if m.transcript != nil && len(m.transcript.messages) > 0 {
+	if m.transcript != nil && m.transcript.hasEpoch {
 		return m.transcript.messages
 	}
 	return nil

go/tui/internal/ui/agent_transcript.go

@@ -11,7 +11,10 @@ import (
 // and the reading anchor. Styled rows are disposable renderer state and live in
 // agentTranscriptRenderer instead.
 type residentTranscript struct {
-	epoch     uint32
+	epoch uint32
+	// hasEpoch is the received-a-frame flag. It stays true for a legitimate
+	// empty 0x86 transcript, so callers never confuse empty resident data with
+	// the pre-seed state that existed before this epoch's full replacement.
 	hasEpoch  bool
 	messages  []protocol.AgentChatMessage
 	entries   []transcriptEntry
@@ -22,7 +25,7 @@ type residentTranscript struct {
 	pinned        bool
 	anchor        transcriptAnchor
 	pendingScroll int
-	pinTransition int
+	pinTransition pinEdge
 	animatedCount int
 }
 
@@ -43,8 +46,10 @@ type transcriptAnchor struct {
 	row  int
 }
 
+type pinEdge uint8
+
 const (
-	pinNone = iota
+	pinNone pinEdge = iota
 	pinScrolledAway
 	pinReturned
 )
@@ -102,6 +107,10 @@ func (t *residentTranscript) apply(frame protocol.AgentTranscript) transcriptDro
 		t.epoch = frame.Epoch
 		t.hasEpoch = true
 		if epochChanged {
+			// An epoch flip is an authoritative session/reset transition. Both
+			// BEAM epoch sources independently reset follow-bottom, so discard a
+			// stale local edge and re-pin without reporting a new intent.
+			t.pinTransition = pinNone
 			t.pinToBottom()
 		} else {
 			t.reconcileAnchor(oldEntries)
@@ -329,7 +338,7 @@ func (t *residentTranscript) rebuildSlotIndex() {
 
 func (t *residentTranscript) reconcileAnchor(oldEntries []transcriptEntry) {
 	if len(t.entries) == 0 {
-		t.pinToBottom()
+		t.returnToBottom()
 		return
 	}
 	if t.pinned || t.anchor.slot == 0 {
@@ -374,6 +383,14 @@ func (t *residentTranscript) pinToBottom() {
 	t.pendingScroll = 0
 }
 
+func (t *residentTranscript) returnToBottom() {
+	wasPinned := t.pinned
+	t.pinToBottom()
+	if !wasPinned {
+		t.recordPinTransition(pinReturned)
+	}
+}
+
 func indexEntryByID(entries []transcriptEntry, id uint32) int {
 	if id == 0 {
 		return -1
@@ -390,7 +407,13 @@ func (t *residentTranscript) scrollBy(rows int) {
 	t.pendingScroll += rows
 }
 
-func (t *residentTranscript) takePinTransition() int {
+func (t *residentTranscript) discardPendingScroll() int {
+	rows := t.pendingScroll
+	t.pendingScroll = 0
+	return rows
+}
+
+func (t *residentTranscript) takePinTransition() pinEdge {
 	transition := t.pinTransition
 	t.pinTransition = pinNone
 	return transition
@@ -400,7 +423,7 @@ func (t *residentTranscript) hasAnimatedMessages() bool {
 	return t != nil && t.animatedCount > 0
 }
 
-func (t *residentTranscript) recordPinTransition(transition int) {
+func (t *residentTranscript) recordPinTransition(transition pinEdge) {
 	if transition != pinNone {
 		t.pinTransition = transition
 	}