fix(tui): close transcript selection regressions and add coverage tests

internal/tui/core/app/copy_code.go

@@ -269,11 +269,8 @@ func (a App) textSelectionRange(lines []string) (startLine int, startCol int, en
 	if !a.textSelection.active || len(lines) == 0 {
 		return 0, 0, 0, 0, false
 	}
-	sLine, sCol, sOk := a.normalizeSelectionPosition(lines, a.textSelection.startLine, a.textSelection.startCol)
-	eLine, eCol, eOk := a.normalizeSelectionPosition(lines, a.textSelection.endLine, a.textSelection.endCol)
-	if !sOk || !eOk {
-		return 0, 0, 0, 0, false
-	}
+	sLine, sCol, _ := a.normalizeSelectionPosition(lines, a.textSelection.startLine, a.textSelection.startCol)
+	eLine, eCol, _ := a.normalizeSelectionPosition(lines, a.textSelection.endLine, a.textSelection.endCol)
 	if sLine > eLine || (sLine == eLine && sCol > eCol) {
 		sLine, eLine = eLine, sLine
 		sCol, eCol = eCol, sCol
@@ -359,15 +356,6 @@ func (a *App) copySelectionToClipboard() {
 		if i == endLine {
 			to = endCol
 		}
-		if from < 0 {
-			from = 0
-		}
-		if to > lineWidth {
-			to = lineWidth
-		}
-		if to < from {
-			to = from
-		}
 		selectedLines = append(selectedLines, ansi.Cut(plain, from, to))
 	}
 

internal/tui/core/app/copy_code_test.go

@@ -0,0 +1,224 @@
+package tui
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+
+	tea "github.com/charmbracelet/bubbletea"
+	providertypes "neo-code/internal/provider/types"
+)
+
+func TestRebuildTranscriptDoesNotCollapseAssistantAcrossToolBoundary(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.width = 120
+	app.height = 32
+	app.applyComponentLayout(true)
+	app.activeMessages = []providertypes.Message{
+		{Role: roleAssistant, Parts: []providertypes.ContentPart{providertypes.NewTextPart("before tool")}},
+		{Role: roleTool, Parts: []providertypes.ContentPart{providertypes.NewTextPart("tool output")}},
+		{Role: roleAssistant, Parts: []providertypes.ContentPart{providertypes.NewTextPart("after tool")}},
+	}
+
+	app.rebuildTranscript()
+	plain := copyCodeANSIPattern.ReplaceAllString(app.transcriptContent, "")
+	if count := strings.Count(plain, messageTagAgent); count != 2 {
+		t.Fatalf("expected two agent tags across tool boundary, got %d in %q", count, plain)
+	}
+}
+
+func TestHandleTranscriptMouseDragMotionWithButtonNone(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.width = 100
+	app.height = 24
+	app.applyComponentLayout(true)
+	app.setTranscriptContent(strings.Repeat("line\n", 40))
+
+	x, y, _, _ := app.transcriptBounds()
+	if !app.handleTranscriptMouse(tea.MouseMsg{
+		X:      x + 2,
+		Y:      y + 1,
+		Button: tea.MouseButtonLeft,
+		Action: tea.MouseActionPress,
+	}) {
+		t.Fatalf("expected press to begin selection")
+	}
+
+	if !app.handleTranscriptMouse(tea.MouseMsg{
+		X:      x + 6,
+		Y:      y + 2,
+		Button: tea.MouseButtonNone,
+		Action: tea.MouseActionMotion,
+		Type:   tea.MouseMotion,
+	}) {
+		t.Fatalf("expected motion with button none while dragging to be handled")
+	}
+	if app.textSelection.endLine != 2 || app.textSelection.endCol <= app.textSelection.startCol {
+		t.Fatalf("expected selection to update on motion with button none, got line=%d col=%d", app.textSelection.endLine, app.textSelection.endCol)
+	}
+}
+
+func TestHighlightTranscriptContentKeepsStyleWhenZeroWidthOnLine(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.width = 100
+	app.height = 24
+	app.applyComponentLayout(true)
+	app.textSelection.active = true
+	app.textSelection.startLine = 0
+	app.textSelection.startCol = 1
+	app.textSelection.endLine = 1
+	app.textSelection.endCol = 0
+
+	content := "\x1b[31mabc\x1b[0m\n\x1b[32mxyz\x1b[0m"
+	highlighted := app.highlightTranscriptContent(content)
+	lines := strings.Split(highlighted, "\n")
+	if len(lines) != 2 {
+		t.Fatalf("expected two lines, got %d", len(lines))
+	}
+	if !strings.Contains(lines[1], "\x1b[32m") {
+		t.Fatalf("expected zero-width selected line to keep existing ANSI style, got %q", lines[1])
+	}
+}
+
+func TestCopySelectionToClipboardFailureKeepsSelection(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.width = 100
+	app.height = 24
+	app.applyComponentLayout(true)
+	app.setTranscriptContent("hello world")
+	app.textSelection.active = true
+	app.textSelection.startLine = 0
+	app.textSelection.startCol = 0
+	app.textSelection.endLine = 0
+	app.textSelection.endCol = 5
+
+	originalClipboard := clipboardWriteAll
+	clipboardWriteAll = func(string) error {
+		return fmt.Errorf("clipboard failed")
+	}
+	defer func() { clipboardWriteAll = originalClipboard }()
+
+	app.copySelectionToClipboard()
+	if app.state.StatusText != "Failed to copy selection" {
+		t.Fatalf("expected status on copy error, got %q", app.state.StatusText)
+	}
+	if !app.textSelection.active {
+		t.Fatalf("expected selection to remain active on copy failure")
+	}
+}
+
+func TestHandleTranscriptMouseRightClickWithoutSelectionNoop(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.width = 100
+	app.height = 24
+	app.applyComponentLayout(true)
+	app.setTranscriptContent("line")
+	x, y, _, _ := app.transcriptBounds()
+	if app.handleTranscriptMouse(tea.MouseMsg{
+		X:      x + 1,
+		Y:      y + 1,
+		Button: tea.MouseButtonRight,
+		Action: tea.MouseActionPress,
+	}) {
+		t.Fatalf("expected right click without selection to be ignored")
+	}
+}
+
+func TestSelectionHelpersGuardAndClampBranches(t *testing.T) {
+	app, _ := newTestApp(t)
+	if _, _, _, _, ok := app.textSelectionRange([]string{"x"}); ok {
+		t.Fatalf("expected inactive selection to return false")
+	}
+	if _, _, ok := app.normalizeSelectionPosition(nil, 0, 0); ok {
+		t.Fatalf("expected normalizeSelectionPosition to reject empty lines")
+	}
+
+	lines := []string{"abc", "de"}
+	line, col, ok := app.normalizeSelectionPosition(lines, -3, 99)
+	if !ok || line != 0 || col != 3 {
+		t.Fatalf("expected clamp to first line end, got line=%d col=%d ok=%v", line, col, ok)
+	}
+	line, col, ok = app.normalizeSelectionPosition(lines, 9, -4)
+	if !ok || line != 1 || col != 0 {
+		t.Fatalf("expected clamp to last line start, got line=%d col=%d ok=%v", line, col, ok)
+	}
+
+	app.textSelection.active = true
+	app.textSelection.startLine = 1
+	app.textSelection.startCol = 2
+	app.textSelection.endLine = 0
+	app.textSelection.endCol = 1
+	startLine, startCol, endLine, endCol, rangeOK := app.textSelectionRange(lines)
+	if !rangeOK || startLine != 0 || startCol != 1 || endLine != 1 || endCol != 2 {
+		t.Fatalf("expected reversed range to normalize ordering, got %d:%d -> %d:%d ok=%v", startLine, startCol, endLine, endCol, rangeOK)
+	}
+
+	app.textSelection.endLine = app.textSelection.startLine
+	app.textSelection.endCol = app.textSelection.startCol
+	if _, _, _, _, equalOK := app.textSelectionRange(lines); equalOK {
+		t.Fatalf("expected empty range to be treated as no selection")
+	}
+}
+
+func TestSplitMarkdownSegmentsFallbackWhenFenceHasNoCode(t *testing.T) {
+	segments := splitMarkdownSegments("```go\n```")
+	if len(segments) != 1 {
+		t.Fatalf("expected fallback text segment count 1, got %d", len(segments))
+	}
+	if segments[0].Kind != markdownSegmentText {
+		t.Fatalf("expected fallback text segment, got kind=%v", segments[0].Kind)
+	}
+
+	indented := splitIndentedCodeSegments("    \n")
+	if len(indented) != 1 || indented[0].Kind != markdownSegmentText {
+		t.Fatalf("expected blank indented content to stay text, got %+v", indented)
+	}
+}
+
+func TestSelectionPositionAndDragGuardBranches(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.width = 100
+	app.height = 24
+	app.applyComponentLayout(true)
+	app.setTranscriptContent("alpha\nbeta")
+
+	if _, _, ok := app.selectionPositionAtMouse(tea.MouseMsg{X: -1, Y: -1}); ok {
+		t.Fatalf("expected outside transcript mouse position to be rejected")
+	}
+	if app.beginTextSelection(tea.MouseMsg{X: -1, Y: -1}) {
+		t.Fatalf("expected beginTextSelection outside transcript to fail")
+	}
+	if app.updateTextSelection(tea.MouseMsg{X: 0, Y: 0}) {
+		t.Fatalf("expected updateTextSelection to fail when not dragging")
+	}
+	if app.finishTextSelection() {
+		t.Fatalf("expected finishTextSelection to fail when not dragging")
+	}
+
+	x, y, _, _ := app.transcriptBounds()
+	if !app.beginTextSelection(tea.MouseMsg{X: x + 1, Y: y + 1}) {
+		t.Fatalf("expected beginTextSelection to succeed in transcript")
+	}
+	if app.updateTextSelection(tea.MouseMsg{X: x - 2, Y: y - 1}) {
+		t.Fatalf("expected updateTextSelection to fail when mouse moved outside transcript")
+	}
+
+	app.textSelection.endLine = app.textSelection.startLine
+	app.textSelection.endCol = app.textSelection.startCol
+	if !app.finishTextSelection() {
+		t.Fatalf("expected finishTextSelection to handle empty selection")
+	}
+	if app.textSelection.active {
+		t.Fatalf("expected empty finished selection to be cleared")
+	}
+}
+
+func TestCopySelectionToClipboardNoSelectionNoop(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.setTranscriptContent("hello")
+	app.state.StatusText = "unchanged"
+	app.copySelectionToClipboard()
+	if app.state.StatusText != "unchanged" {
+		t.Fatalf("expected no-selection copy to be noop, got status %q", app.state.StatusText)
+	}
+}

internal/tui/core/app/update.go

@@ -1848,7 +1848,7 @@ func (a *App) handleTranscriptMouse(msg tea.MouseMsg) bool {
 	switch {
 	case msg.Button == tea.MouseButtonLeft && msg.Action == tea.MouseActionPress:
 		return a.beginTextSelection(msg)
-	case msg.Button == tea.MouseButtonLeft && (msg.Action == tea.MouseActionMotion || msg.Type == tea.MouseMotion):
+	case (msg.Action == tea.MouseActionMotion || msg.Type == tea.MouseMotion) && a.textSelection.dragging:
 		return a.updateTextSelection(msg)
 	case msg.Action == tea.MouseActionRelease || msg.Type == tea.MouseRelease:
 		return a.finishTextSelection()
@@ -2314,6 +2314,8 @@ func (a *App) rebuildTranscript() {
 	previousRole := ""
 	for _, message := range a.activeMessages {
 		if message.Role == roleTool {
+			// tool 消息在 transcript 中不直接展示，但需要打断 assistant 连续分段。
+			previousRole = roleTool
 			continue
 		}
 		continuation := message.Role == roleAssistant && previousRole == roleAssistant
@@ -2375,7 +2377,6 @@ func (a *App) highlightTranscriptContent(content string) string {
 		selStart = max(0, min(selStart, lineWidth))
 		selEnd = max(selStart, min(selEnd, lineWidth))
 		if selEnd <= selStart {
-			lines[i] = plain
 			continue
 		}
 		prefix := ansi.Cut(plain, 0, selStart)

internal/tui/core/app/view_test.go

@@ -125,6 +125,22 @@ func TestRenderWaterfallThinkingState(t *testing.T) {
 	}
 }
 
+func TestRenderWaterfallSelectionHint(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.state.ActivePicker = pickerNone
+	app.textSelection.active = true
+	app.textSelection.startLine = 0
+	app.textSelection.startCol = 0
+	app.textSelection.endLine = 0
+	app.textSelection.endCol = 1
+	app.setTranscriptContent("hello")
+
+	view := app.renderWaterfall(80, 24)
+	if !strings.Contains(view, "已选择内容，右键复制") {
+		t.Fatalf("expected selection hint in waterfall view")
+	}
+}
+
 func TestApplyComponentLayoutKeepsTranscriptHeightInSyncWithWaterfall(t *testing.T) {
 	app, _ := newTestApp(t)
 	app.width = 100