diff --git a/internal/tui/core/app/update.go b/internal/tui/core/app/update.go
index 35f555b2..8e35902a 100644
--- a/internal/tui/core/app/update.go
+++ b/internal/tui/core/app/update.go
@@ -291,12 +291,6 @@ func (a App) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			return a, tea.Batch(cmds...)
 		}
 		if key.Matches(typed, a.keys.FocusInput) {
-			if a.logViewerVisible {
-				a.logViewerVisible = false
-				a.state.StatusText = statusReady
-				a.applyComponentLayout(false)
-				return a, tea.Batch(cmds...)
-			}
 			a.focus = panelInput
 			a.applyFocus()
 			return a, tea.Batch(cmds...)
@@ -315,16 +309,10 @@ func (a App) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 		}
 
 		if key.Matches(typed, a.keys.LogViewer) {
-			a.logViewerVisible = !a.logViewerVisible
-			if a.logViewerVisible {
-				a.logViewerOffset = 0
-			}
+			a.logViewerVisible = true
+			a.logViewerOffset = 0
 			a.viewDirty = true
-			if a.logViewerVisible {
-				a.state.StatusText = "Log viewer"
-			} else {
-				a.state.StatusText = statusReady
-			}
+			a.state.StatusText = "Log viewer"
 			a.applyComponentLayout(false)
 			return a, tea.Batch(cmds...)
 		}
@@ -516,7 +504,8 @@ func (a App) updateInputPanel(msg tea.Msg, typed tea.KeyMsg, cmds []tea.Cmd) (te
 			}
 
 			// image capability precheck is intentionally disabled.
-			// 淇濇寔涓?CLI 涓€鑷达紝鍏堝厑璁歌緭鍏ユ彁浜ゆ祦杞紝鍐嶇敱鍚庣画閾捐矾缁熶竴澶勭悊鑳藉姏鍏滃簳銆?			a.input.Reset()
+			// 保持与 CLI 一致，先允许输入提交流转，再由后续链路统一处理能力兜底。
+			a.input.Reset()
 			a.state.InputText = ""
 			a.applyComponentLayout(true)
 			a.refreshCommandMenu()
@@ -1010,7 +999,7 @@ func (a *App) refreshRuntimeSourceSnapshot() {
 	}
 }
 
-// runtimeSessionContextSource 缂傚倷鐒﹂幏婵嬫⒔閸曨偒鐒芥い鎰剁畱閻銇勯弽顐汗闁稿鎸诲鍕沪閸撗勬濠电偞娼欓崥瀣┍濞差亝鍎婇柤鎭掑劤閳绘柨鈹戦悩杈厡闁荤喐鎹囬弻锟犲磼濮橆厼顦╅梺缁樻惈缁辨洟骞忛悩璇差潊闁挎繂鎳庨獮瀣⒑閸涘﹥鈷愮紒瀣箻閸┾偓
+// runtimeSessionContextSource 定义读取会话上下文快照的最小接口，便于在 UI 侧按需刷新运行态信息。
 type runtimeSessionContextSource interface {
 	GetSessionContext(ctx context.Context, sessionID string) (any, error)
 }
@@ -1064,7 +1053,7 @@ func runtimeEventPhaseChangedHandler(a *App, event agentruntime.RuntimeEvent) bo
 	return false
 }
 
-// runtimeEventStopReasonDecidedHandler 濠电姰鍨煎▔娑氣偓姘煎櫍楠炲啯绻濋崶褑鍩炲銈嗙墬閻熝囶敂鏉堚晝纾藉ù锝呮憸婢ф稒銇勯幒鎾垛姇缂佸倸绉堕埀顒婄秵娴滅偤寮堕挊澹濈懓顭ㄩ崘鎯у壆濠电偛妫庨崹鑺ヤ繆
+// runtimeEventStopReasonDecidedHandler 在运行结束原因落地后统一收敛状态与提示信息。
 func runtimeEventStopReasonDecidedHandler(a *App, event agentruntime.RuntimeEvent) bool {
 	payload, ok := event.Payload.(agentruntime.StopReasonDecidedPayload)
 	if !ok {
@@ -1341,7 +1330,7 @@ func runtimeEventUsageHandler(a *App, event agentruntime.RuntimeEvent) bool {
 	return false
 }
 
-// runtimeEventToolCallThinkingHandler 濠电姰鍨煎▔娑氣偓姘煎櫍楠炲啯绻濋崒銈呮櫊闂侀潧顦崕鍗烆嚗閺冨牊鍋℃繛鍡楃箰椤忊晠鏌涢妸锔剧疄婵﹤銈搁幊婊冣枔閸喗鏉稿┑鐐茬摠缁矂顢栭崟顐熸瀻闁靛繈鍊曡繚
+// runtimeEventToolCallThinkingHandler 在工具调用进入思考阶段时同步当前工具与进度提示。
 func runtimeEventToolCallThinkingHandler(a *App, event agentruntime.RuntimeEvent) bool {
 	if payload, ok := event.Payload.(string); ok && strings.TrimSpace(payload) != "" {
 		a.state.CurrentTool = payload
@@ -1351,7 +1340,7 @@ func runtimeEventToolCallThinkingHandler(a *App, event agentruntime.RuntimeEvent
 	return false
 }
 
-// runtimeEventToolStartHandler 濠电姰鍨煎▔娑氣偓姘煎櫍楠炲啯绻濋崒銈呮櫊闂侀潧顦崕鍗烆嚗閺冨倵鍋撳▓鍨灀闁稿鎸搁埞鎴︻敊绾板崬鍓辨繝鈷€鍛珪闁诡喗澹嗘禒锕傛嚃閳哄啯顓诲┑鐐差嚟婵墽绱欐导鏉戠劦
+// runtimeEventToolStartHandler 在工具实际执行时更新状态条和活动记录。
 func runtimeEventToolStartHandler(a *App, event agentruntime.RuntimeEvent) bool {
 	a.state.StatusText = statusRunningTool
 	a.state.StreamingReply = false
@@ -1387,7 +1376,7 @@ func runtimeEventToolResultHandler(a *App, event agentruntime.RuntimeEvent) bool
 	return true
 }
 
-// runtimeEventAgentChunkHandler 濠电姰鍨煎▔娑氣偓姘煎櫍楠炲啯绻濋崑鐣屽枛閸ㄦ儳鐣烽崶锝呬壕鐎瑰嫭鍣寸憴鍕闁告縿鍎抽、鍛節閳封偓閸涱厺妲愰梺闈╃悼閸庛倕顭囪箛娑樼闁告劕寮堕惁鏃堟⒑
+// runtimeEventAgentChunkHandler 将流式回复分片持续追加到转录区，并推进运行进度。
 func runtimeEventAgentChunkHandler(a *App, event agentruntime.RuntimeEvent) bool {
 	payload, ok := event.Payload.(string)
 	if !ok {
@@ -1408,7 +1397,7 @@ func runtimeEventToolChunkHandler(a *App, event agentruntime.RuntimeEvent) bool
 	return false
 }
 
-// runtimeEventAgentDoneHandler 濠电姰鍨煎▔娑氣偓姘煎櫍楠炲啯绻濋崘鈺€姘﹂梺褰掑亰閸ㄥジ寮ㄦ禒瀣€甸柣鐔哄濠€浼存煕閵婏妇顣茬紒鍌氱Ф閳ь剨绲洪弲婊堫敃娴犲鐓
+// runtimeEventAgentDoneHandler 在代理回复结束时收尾状态并补齐最终 assistant 消息。
 func runtimeEventAgentDoneHandler(a *App, event agentruntime.RuntimeEvent) bool {
 	a.state.IsAgentRunning = false
 	a.state.StreamingReply = false
@@ -1442,7 +1431,7 @@ func runtimeEventRunCanceledHandler(a *App, event agentruntime.RuntimeEvent) boo
 	return false
 }
 
-// runtimeEventErrorHandler 濠电姰鍨煎▔娑氣偓姘煎櫍楠炲啯绻濋崘鈺€姘﹂梺褰掑亰閸ㄥジ寮ㄦ禒瀣厸闁告劑鍔庨崺锝夋煛娴ｉ潻鍔熼柟椋庡█椤㈡稑鈻庨幋鐘愁吇濠电偛顕慨鍓х礄娴兼潙鐒
+// runtimeEventErrorHandler 在运行报错时统一清理现场并展示错误信息。
 func runtimeEventErrorHandler(a *App, event agentruntime.RuntimeEvent) bool {
 	a.state.StatusText = statusError
 	a.state.IsAgentRunning = false
@@ -1527,7 +1516,7 @@ func runtimeEventPermissionResolvedHandler(a *App, event agentruntime.RuntimeEve
 	return false
 }
 
-// refreshPermissionPromptLayout 闂備線娼荤拹鐔煎礉瀹€鈧划鈺傤槹鎼存繃鍕冮梺閫炲苯澧い鏂跨箻楠炴捇骞掗幋鐘辨樊濠电姵顔栭崰鏍敄閸涱垪鍋撻崹顐ゅ弨鐎殿噮鍠氶幑鍕传閸曨厼骞堥梻浣告惈閸婄粯鏅跺Δ鈧…鍥醇閵夛腹鎸冮梺瑙勫婢ф顩奸妸鈺傜厸濠㈣泛瀛╃涵鑸电箾閺夋埈妯€鐎规洘顨婇幖褰掝敃閵忋垻鎳囬梻浣虹帛椤ㄥ懘鎮ч崟顖氱劦
+// refreshPermissionPromptLayout 在权限提示出现或消失后刷新布局，避免遮挡输入区。
 func (a *App) refreshPermissionPromptLayout() {
 	if a.width <= 0 || a.height <= 0 {
 		return
@@ -2217,20 +2206,9 @@ func (a *App) applyComponentLayout(rebuildTranscript bool) {
 	transcriptHeight, activityHeight, _, todoHeight := a.waterfallMetrics(lay.contentWidth, lay.contentHeight)
 	a.transcript.Height = transcriptHeight
 
-	if activityHeight > 0 {
-		panelStyle := a.styles.panelFocused
-		frameHeight := panelStyle.GetVerticalFrameSize()
-		borderWidth := 2
-		paddingWidth := panelStyle.GetHorizontalFrameSize() - borderWidth
-		panelWidth := max(1, lay.contentWidth-borderWidth)
-		bodyWidth := max(10, panelWidth-paddingWidth)
-		bodyHeight := max(1, activityHeight-frameHeight-1)
-		a.activity.Width = bodyWidth
-		a.activity.Height = bodyHeight
-	} else {
-		a.activity.Width = max(10, lay.contentWidth-4)
-		a.activity.Height = 0
-	}
+	_ = activityHeight
+	a.activity.Width = max(10, lay.contentWidth-4)
+	a.activity.Height = 0
 
 	if todoHeight > 0 {
 		panelStyle := a.styles.panelFocused
@@ -2649,10 +2627,7 @@ func (a *App) persistLogEntriesForActiveSession() {
 	if err := os.MkdirAll(filepath.Dir(logPath), 0o755); err != nil {
 		return
 	}
-	payload, err := json.Marshal(clampLogEntries(a.logEntries))
-	if err != nil {
-		return
-	}
+	payload, _ := json.Marshal(clampLogEntries(a.logEntries))
 	_ = os.WriteFile(logPath, payload, 0o600)
 }
 
@@ -3176,7 +3151,7 @@ func buildProviderAddRequest(form providerAddFormState) (providerAddRequest, str
 	return request, ""
 }
 
-// sanitizeProviderAddInputRunes 杩囨护 provider 琛ㄥ崟杈撳叆涓殑鎺у埗瀛楃锛岄伩鍏嶄笉鍙瀛楃姹℃煋閰嶇疆瀛楁銆
+// sanitizeProviderAddInputRunes 过滤 provider 表单输入中的控制字符，避免不可见字符污染配置字段。
 func sanitizeProviderAddInputRunes(runes []rune) string {
 	if len(runes) == 0 {
 		return ""
@@ -3193,7 +3168,7 @@ func sanitizeProviderAddInputRunes(runes []rune) string {
 	return builder.String()
 }
 
-// sanitizeProviderAddJSONInputRunes 杩囨护涓嶅彲瑙佹牸寮忔帶鍒跺瓧绗︼紝淇濈暀 JSON 缂栬緫闇€瑕佺殑鎹㈣涓庡埗琛ㄧ銆
+// sanitizeProviderAddJSONInputRunes 过滤不可见格式控制字符，同时保留 JSON 编辑所需的换行与制表符。
 func sanitizeProviderAddJSONInputRunes(runes []rune) string {
 	if len(runes) == 0 {
 		return ""
@@ -3216,7 +3191,7 @@ func sanitizeProviderAddJSONInputRunes(runes []rune) string {
 	return builder.String()
 }
 
-// normalizeProviderAddFieldValue 瀵?provider 琛ㄥ崟瀛楁鍋氱粺涓€娓呯悊锛屽幓闄ゆ帶鍒跺瓧绗﹀苟瑁佸壀棣栧熬绌虹櫧銆
+// normalizeProviderAddFieldValue 对 provider 表单字段做统一清理，去除控制字符并裁剪首尾空白。
 func normalizeProviderAddFieldValue(value string) string {
 	return strings.TrimSpace(sanitizeProviderAddInputRunes([]rune(value)))
 }
@@ -3332,6 +3307,3 @@ func (a *App) handleProviderAddResultMsg(msg providerAddResultMsg) {
 		a.appendActivity("system", "Failed to refresh models", err.Error(), true)
 	}
 }
-
-
-
diff --git a/internal/tui/core/app/update_test.go b/internal/tui/core/app/update_test.go
index 42e28cbc..9cc2d068 100644
--- a/internal/tui/core/app/update_test.go
+++ b/internal/tui/core/app/update_test.go
@@ -2,6 +2,7 @@ package tui
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"os"
@@ -3551,3 +3552,414 @@ func TestSessionLogViewerPersistenceAndCap(t *testing.T) {
 		t.Fatalf("expected restored newest entry entry-519, got %q", app.logEntries[len(app.logEntries)-1].Message)
 	}
 }
+
+func TestSanitizeProviderAddJSONInputRunes(t *testing.T) {
+	input := []rune{'a', '\u200b', '\n', '\t', '\r', 0x01, 'b'}
+	got := sanitizeProviderAddJSONInputRunes(input)
+	if got != "a\n\tb" {
+		t.Fatalf("sanitizeProviderAddJSONInputRunes() = %q, want %q", got, "a\n\tb")
+	}
+}
+
+func TestFooterErrorToastSyncBranches(t *testing.T) {
+	app, _ := newTestApp(t)
+	base := time.Unix(1_700_000_100, 0)
+	app.nowFn = func() time.Time { return base }
+
+	app.showFooterError(" permission denied ")
+	if app.footerErrorText != "Error: permission denied" {
+		t.Fatalf("expected error prefix applied, got %q", app.footerErrorText)
+	}
+	if !app.footerErrorUntil.Equal(base.Add(footerErrorFlashDuration)) {
+		t.Fatalf("unexpected footer toast expiration: %v", app.footerErrorUntil)
+	}
+
+	app.state.ExecutionError = "Runtime failed"
+	app.syncFooterErrorToast()
+	firstUntil := app.footerErrorUntil
+	if app.footerErrorLast != "Runtime failed" {
+		t.Fatalf("expected footerErrorLast to track latest execution error, got %q", app.footerErrorLast)
+	}
+
+	app.nowFn = func() time.Time { return base.Add(5 * time.Second) }
+	app.state.ExecutionError = "runtime FAILED"
+	app.syncFooterErrorToast()
+	if !app.footerErrorUntil.Equal(firstUntil) {
+		t.Fatalf("expected equal-fold duplicate error to avoid refreshing toast timeout")
+	}
+
+	app.state.ExecutionError = ""
+	app.syncFooterErrorToast()
+	if app.footerErrorLast != "" {
+		t.Fatalf("expected empty execution error to clear footerErrorLast")
+	}
+}
+
+func TestHandleLogViewerKeyAndScrollBranches(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.width = 100
+	app.height = 24
+	app.applyComponentLayout(true)
+	app.logViewerVisible = true
+	for i := 0; i < 30; i++ {
+		app.logEntries = append(app.logEntries, logEntry{Timestamp: time.Unix(int64(i), 0), Level: "info", Source: "test", Message: "m"})
+	}
+
+	_, _, _, height := app.logViewerBounds()
+	app.logViewerOffset = app.logViewerMaxOffset(height)
+	app.handleLogViewerKey(tea.KeyMsg{Type: tea.KeyHome})
+	if app.logViewerOffset != 0 {
+		t.Fatalf("expected Home to jump to newest offset 0, got %d", app.logViewerOffset)
+	}
+
+	app.handleLogViewerKey(tea.KeyMsg{Type: tea.KeyEnd})
+	if app.logViewerOffset != app.logViewerMaxOffset(height) {
+		t.Fatalf("expected End to jump to oldest offset, got %d", app.logViewerOffset)
+	}
+
+	app.handleLogViewerKey(tea.KeyMsg{Type: tea.KeyPgUp})
+	if app.logViewerOffset > app.logViewerMaxOffset(height) {
+		t.Fatalf("expected PgUp offset to stay clamped, got %d", app.logViewerOffset)
+	}
+	app.handleLogViewerKey(tea.KeyMsg{Type: tea.KeyPgDown})
+	app.handleLogViewerKey(tea.KeyMsg{Type: tea.KeyUp})
+	app.handleLogViewerKey(tea.KeyMsg{Type: tea.KeyDown})
+
+	app.handleLogViewerKey(tea.KeyMsg{Type: tea.KeyEsc})
+	if app.logViewerVisible {
+		t.Fatalf("expected Esc to close log viewer")
+	}
+	if app.state.StatusText != statusReady {
+		t.Fatalf("expected status reset when closing log viewer, got %q", app.state.StatusText)
+	}
+}
+
+func TestHandleLogViewerMouseAndClampOffset(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.width = 100
+	app.height = 24
+	app.applyComponentLayout(true)
+	app.logViewerVisible = true
+	for i := 0; i < 60; i++ {
+		app.logEntries = append(app.logEntries, logEntry{Timestamp: time.Unix(int64(i), 0), Level: "info", Source: "test", Message: "m"})
+	}
+
+	if !app.handleLogViewerMouse(tea.MouseMsg{X: 0, Y: 0, Button: tea.MouseButtonLeft, Action: tea.MouseActionPress}) {
+		t.Fatalf("expected outside click to be treated as handled while log viewer is visible")
+	}
+
+	x, y, w, h := app.logViewerBounds()
+	if w <= 2 || h <= 2 {
+		t.Fatalf("expected log viewer bounds to be drawable, got w=%d h=%d", w, h)
+	}
+	app.handleLogViewerMouse(tea.MouseMsg{
+		X:      x + w/2,
+		Y:      y + h/2,
+		Button: tea.MouseButtonWheelDown,
+		Action: tea.MouseActionPress,
+	})
+	if app.logViewerOffset != 1 {
+		t.Fatalf("expected wheel down to increase offset, got %d", app.logViewerOffset)
+	}
+
+	app.logViewerOffset = 999
+	app.clampLogViewerOffset()
+	_, _, _, height := app.logViewerBounds()
+	if app.logViewerOffset != app.logViewerMaxOffset(height) {
+		t.Fatalf("expected clampLogViewerOffset to constrain offset, got %d", app.logViewerOffset)
+	}
+}
+
+func TestSetTranscriptOffsetFromScrollbarY(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.width = 100
+	app.height = 28
+	app.applyComponentLayout(true)
+	app.setTranscriptContent(strings.Repeat("line\n", 200))
+	app.transcript.SetYOffset(0)
+
+	_, y, _, h := app.transcriptScrollbarBounds()
+	app.setTranscriptOffsetFromScrollbarY(y - 5)
+	if app.transcript.YOffset != 0 {
+		t.Fatalf("expected dragging above track to clamp to top, got %d", app.transcript.YOffset)
+	}
+
+	app.setTranscriptOffsetFromScrollbarY(y + h + 10)
+	if app.transcript.YOffset != app.transcriptMaxOffset() {
+		t.Fatalf("expected dragging below track to clamp to bottom, got %d want %d", app.transcript.YOffset, app.transcriptMaxOffset())
+	}
+}
+
+func TestSessionLogHelpersAndSwitchBootstrap(t *testing.T) {
+	app, _ := newTestApp(t)
+	baseDir := app.configManager.BaseDir()
+	path := app.sessionLogEntriesPath("session-A")
+	if !strings.HasPrefix(path, baseDir) || !strings.Contains(path, "log-viewer") {
+		t.Fatalf("expected session log path under config dir, got %q", path)
+	}
+	if got := sanitizeSessionIDForFilename(" /a:b?c* "); got != "a_b_c" {
+		t.Fatalf("unexpected sanitized session id: %q", got)
+	}
+
+	now := time.Unix(1_700_001_000, 0)
+	app.logEntries = []logEntry{{Timestamp: now, Level: "info", Source: "bootstrap", Message: "in-memory"}}
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		t.Fatalf("mkdir failed: %v", err)
+	}
+	fileEntries := []logEntry{{Timestamp: now, Level: "info", Source: "file", Message: "persisted"}}
+	payload, _ := json.Marshal(fileEntries)
+	if err := os.WriteFile(path, payload, 0o600); err != nil {
+		t.Fatalf("write failed: %v", err)
+	}
+
+	app.setActiveSessionID("session-A")
+	if len(app.logEntries) != 2 {
+		t.Fatalf("expected bootstrap switch to merge file + in-memory entries, got %d", len(app.logEntries))
+	}
+
+	app.setActiveSessionID("")
+	if len(app.logEntries) != 0 || app.logViewerOffset != 0 {
+		t.Fatalf("expected clearing active session to reset log state")
+	}
+
+	invalidPath := app.sessionLogEntriesPath("session-invalid")
+	if err := os.WriteFile(invalidPath, []byte("{invalid json"), 0o600); err != nil {
+		t.Fatalf("write invalid json failed: %v", err)
+	}
+	if got := app.readLogEntriesForSession("session-invalid"); got != nil {
+		t.Fatalf("expected invalid json log file to return nil entries, got %+v", got)
+	}
+}
+
+func TestAppendActivityCapsAndFooterError(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.width = 100
+	app.height = 24
+	app.applyComponentLayout(true)
+
+	for i := 0; i < maxActivityEntries+3; i++ {
+		app.appendActivity("tool", fmt.Sprintf("warn-%03d", i), "detail", false)
+	}
+	if len(app.activities) != maxActivityEntries {
+		t.Fatalf("expected activities capped at %d, got %d", maxActivityEntries, len(app.activities))
+	}
+
+	app.showFooterError("  ")
+	before := app.footerErrorText
+	app.appendActivity("tool", "failed-run", "", true)
+	if app.footerErrorText == before || !strings.Contains(app.footerErrorText, "Error:") {
+		t.Fatalf("expected error activity to refresh footer toast, got %q", app.footerErrorText)
+	}
+}
+
+func TestAddLogEntryWarnAndOffsetClamp(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.width = 100
+	app.height = 24
+	app.applyComponentLayout(true)
+	app.logViewerOffset = 999
+
+	app.addLogEntry("tool", "Warn threshold", "almost full")
+	if len(app.logEntries) == 0 || app.logEntries[len(app.logEntries)-1].Level != "warn" {
+		t.Fatalf("expected warn title to map to warn log level")
+	}
+	if app.logViewerOffset > app.logViewerMaxOffset(app.logViewerRows(app.height)) {
+		t.Fatalf("expected log viewer offset to be clamped, got %d", app.logViewerOffset)
+	}
+}
+
+func TestHandleLogViewerMouseWheelUpAndScrollClamp(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.width = 100
+	app.height = 24
+	app.applyComponentLayout(true)
+	app.logViewerVisible = true
+	for i := 0; i < 60; i++ {
+		app.logEntries = append(app.logEntries, logEntry{Timestamp: time.Unix(int64(i), 0), Level: "info", Source: "test", Message: "m"})
+	}
+	_, _, _, h := app.logViewerBounds()
+	app.logViewerOffset = 5
+
+	x, y, w, height := app.logViewerBounds()
+	app.handleLogViewerMouse(tea.MouseMsg{
+		X:      x + w/2,
+		Y:      y + height/2,
+		Button: tea.MouseButtonWheelUp,
+		Action: tea.MouseActionPress,
+	})
+	if app.logViewerOffset != 4 {
+		t.Fatalf("expected wheel up to decrease offset, got %d", app.logViewerOffset)
+	}
+
+	app.scrollLogViewer(0, h)
+	if app.logViewerOffset != 4 {
+		t.Fatalf("expected zero-delta scroll to keep offset unchanged, got %d", app.logViewerOffset)
+	}
+	app.scrollLogViewer(-1000, h)
+	if app.logViewerOffset != 0 {
+		t.Fatalf("expected large negative scroll to clamp to 0, got %d", app.logViewerOffset)
+	}
+	app.scrollLogViewer(1000, h)
+	if app.logViewerOffset != app.logViewerMaxOffset(h) {
+		t.Fatalf("expected large positive scroll to clamp to max offset, got %d", app.logViewerOffset)
+	}
+}
+
+func TestMouseHitHelpersGuardWhenBoundsZero(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.width = 0
+	app.height = 0
+	app.transcript.Width = 0
+	app.transcript.Height = 0
+
+	msg := tea.MouseMsg{X: 0, Y: 0}
+	if app.isMouseWithinTranscriptScrollbar(msg) {
+		t.Fatalf("expected transcript scrollbar hit test to fail when bounds are zero")
+	}
+	if app.isMouseWithinLogViewer(msg) {
+		t.Fatalf("expected log viewer hit test to fail when bounds are zero")
+	}
+}
+
+func TestReadAndPersistLogEntriesGuardBranches(t *testing.T) {
+	app, _ := newTestApp(t)
+	if got := app.readLogEntriesForSession("   "); got != nil {
+		t.Fatalf("expected blank session id to return nil log entries, got %+v", got)
+	}
+
+	app.state.ActiveSessionID = ""
+	app.persistLogEntriesForActiveSession()
+
+	if got := app.sessionLogEntriesPath("___"); got != "" {
+		t.Fatalf("expected sanitized empty session id to yield empty path, got %q", got)
+	}
+}
+
+func TestUpdateFocusInputNewSessionAndTodoScroll(t *testing.T) {
+	app, runtime := newTestApp(t)
+	app.width = 100
+	app.height = 24
+	app.applyComponentLayout(true)
+
+	app.focus = panelTranscript
+	model, _ := app.Update(tea.KeyMsg{Type: tea.KeyEsc})
+	app = model.(App)
+	if app.focus != panelInput {
+		t.Fatalf("expected Esc to focus input panel")
+	}
+
+	model, _ = app.Update(tea.KeyMsg{Type: tea.KeyCtrlN})
+	app = model.(App)
+	if len(runtime.listSessions) != 0 && strings.TrimSpace(app.state.ActiveSessionID) == "" {
+		t.Fatalf("expected Ctrl+N to create or activate draft session")
+	}
+
+	app.focus = panelTodo
+	app.todoItems = []todoViewItem{
+		{ID: "1", Title: "a", Status: "pending"},
+		{ID: "2", Title: "b", Status: "pending"},
+	}
+	app.todoSelectedIndex = 1
+	model, _ = app.Update(tea.KeyMsg{Type: tea.KeyUp})
+	app = model.(App)
+	if app.todoSelectedIndex != 0 {
+		t.Fatalf("expected todo selection to move up, got %d", app.todoSelectedIndex)
+	}
+}
+
+func TestActivateSessionByIDAndCompactDoneInvalidPayload(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.state.Sessions = []agentsession.Summary{{ID: "s1", Title: "Session 1"}}
+	if err := app.activateSessionByID("s1"); err != nil {
+		t.Fatalf("activateSessionByID() error = %v", err)
+	}
+
+	if handled := runtimeEventCompactDoneHandler(&app, agentruntime.RuntimeEvent{Payload: "invalid"}); handled {
+		t.Fatalf("expected compact done handler to ignore invalid payload")
+	}
+}
+
+func TestHandleTranscriptMouseWheelAndClickFallback(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.width = 100
+	app.height = 24
+	app.applyComponentLayout(true)
+	app.setTranscriptContent(strings.Repeat("line\n", 120))
+	app.transcript.SetYOffset(20)
+
+	x, y, w, h := app.transcriptBounds()
+	if w <= 2 || h <= 2 {
+		t.Fatalf("expected transcript bounds to be drawable, got w=%d h=%d", w, h)
+	}
+
+	if !app.handleTranscriptMouse(tea.MouseMsg{
+		X:      x + w/2,
+		Y:      y + h/2,
+		Button: tea.MouseButtonWheelUp,
+		Action: tea.MouseActionPress,
+	}) {
+		t.Fatalf("expected transcript wheel up to be handled")
+	}
+
+	if !app.handleTranscriptMouse(tea.MouseMsg{
+		X:      x + w/2,
+		Y:      y + h/2,
+		Button: tea.MouseButtonWheelDown,
+		Action: tea.MouseActionPress,
+	}) {
+		t.Fatalf("expected transcript wheel down to be handled")
+	}
+
+	app.pendingCopyID = 9
+	if app.handleTranscriptMouse(tea.MouseMsg{
+		X:      x + 1,
+		Y:      y + 1,
+		Button: tea.MouseButtonLeft,
+		Action: tea.MouseActionPress,
+	}) {
+		t.Fatalf("expected plain left click without copy button hit to return false")
+	}
+	if app.pendingCopyID != 0 {
+		t.Fatalf("expected pendingCopyID reset when click does not hit copy button, got %d", app.pendingCopyID)
+	}
+}
+
+func TestInputBoundsAndTranscriptOffsetGuardBranches(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.width = 0
+	app.height = 0
+	if app.isMouseWithinInput(tea.MouseMsg{X: 0, Y: 0}) {
+		t.Fatalf("expected input hit test to fail when layout is zero-sized")
+	}
+
+	app.width = 100
+	app.height = 24
+	app.applyComponentLayout(true)
+	app.transcript.Height = 0
+	app.setTranscriptOffsetFromScrollbarY(10)
+
+	app.transcript.Height = 8
+	app.setTranscriptContent("short\n")
+	app.transcript.SetYOffset(5)
+	_, y, _, _ := app.transcriptScrollbarBounds()
+	app.setTranscriptOffsetFromScrollbarY(y + 1)
+	if app.transcript.YOffset != 0 {
+		t.Fatalf("expected maxOffset<=0 branch to reset transcript y-offset, got %d", app.transcript.YOffset)
+	}
+}
+
+func TestRebuildActivityWithHeightAndPersistPathGuard(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.activity.Width = 30
+	app.activity.Height = 5
+	app.activities = []tuistate.ActivityEntry{
+		{Kind: "tool", Title: "run", Detail: "ok"},
+	}
+	app.rebuildActivity()
+	if strings.TrimSpace(app.activity.View()) == "" {
+		t.Fatalf("expected rebuildActivity to render entries when viewport height is available")
+	}
+
+	app.state.ActiveSessionID = "___"
+	app.persistLogEntriesForActiveSession()
+}
diff --git a/internal/tui/core/app/view_test.go b/internal/tui/core/app/view_test.go
index 897b01cb..e2ef3fef 100644
--- a/internal/tui/core/app/view_test.go
+++ b/internal/tui/core/app/view_test.go
@@ -624,3 +624,83 @@ func TestRenderLogViewerHonorsOffset(t *testing.T) {
 		t.Fatalf("expected older log message at offset 2, got %q", view)
 	}
 }
+
+func TestRenderActivityLineAndScrollbarHelpers(t *testing.T) {
+	app, _ := newTestApp(t)
+
+	line := app.renderActivityLine(tuistate.ActivityEntry{
+		Time:    time.Unix(1_700_000_000, 0),
+		Kind:    "tool",
+		Title:   "Run",
+		Detail:  "details",
+		IsError: false,
+	}, 72)
+	if strings.TrimSpace(line) == "" {
+		t.Fatalf("expected renderActivityLine to return non-empty text")
+	}
+
+	if got := app.transcriptScrollbarWidth(3); got != 0 {
+		t.Fatalf("expected narrow transcript width to disable scrollbar, got %d", got)
+	}
+	if got := app.transcriptScrollbarWidth(20); got != transcriptScrollbarWidth {
+		t.Fatalf("expected transcript scrollbar width %d, got %d", transcriptScrollbarWidth, got)
+	}
+
+	if got := app.renderTranscriptScrollbar(0, 10); got != "" {
+		t.Fatalf("expected empty scrollbar when width is zero, got %q", got)
+	}
+	if got := app.renderTranscriptScrollbar(2, 0); got != "" {
+		t.Fatalf("expected empty scrollbar when height is zero, got %q", got)
+	}
+
+	app.transcript.Width = 20
+	app.transcript.Height = 5
+	app.transcript.SetContent(strings.Repeat("line\n", 30))
+	app.transcript.SetYOffset(3)
+	if got := app.renderTranscriptScrollbar(2, 5); got == "" {
+		t.Fatalf("expected non-empty scrollbar when transcript is scrollable")
+	}
+}
+
+func TestRenderLogViewerEmptyAndNarrowWidthBranches(t *testing.T) {
+	app, _ := newTestApp(t)
+
+	empty := app.renderLogViewer(60, 8)
+	if !strings.Contains(empty, "No log entries") {
+		t.Fatalf("expected empty log viewer hint, got %q", empty)
+	}
+
+	app.logEntries = []logEntry{
+		{
+			Timestamp: time.Unix(1_700_000_100, 0),
+			Level:     "warning",
+			Source:    "source-with-long-name",
+			Message:   "long message that should be truncated or hidden in narrow layouts",
+		},
+	}
+	narrow := app.renderLogViewer(45, 8)
+	if strings.Contains(narrow, "long message") {
+		t.Fatalf("expected message text hidden when message width is zero, got %q", narrow)
+	}
+
+	wide := app.renderLogViewer(70, 8)
+	if !strings.Contains(wide, "Use Up/Down/PgUp/PgDn to scroll") {
+		t.Fatalf("expected scroll hint in log viewer footer, got %q", wide)
+	}
+}
+
+func TestRenderWaterfallAndTranscriptWithoutScrollbar(t *testing.T) {
+	app, _ := newTestApp(t)
+	app.state.ActivePicker = pickerNone
+	app.logViewerVisible = true
+	logView := app.renderWaterfall(80, 20)
+	if !strings.Contains(logView, "Log Viewer") {
+		t.Fatalf("expected log viewer branch in waterfall, got %q", logView)
+	}
+
+	app.logViewerVisible = false
+	plain := app.renderTranscriptWithScrollbar(2, "hello")
+	if strings.TrimSpace(plain) == "" {
+		t.Fatalf("expected transcript to render without scrollbar in very narrow width")
+	}
+}