diff --git a/internal/session/log_test.go b/internal/session/log_test.go
new file mode 100644
index 0000000..64175ad
--- /dev/null
+++ b/internal/session/log_test.go
@@ -0,0 +1,169 @@
+package session
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestFormatDuration(t *testing.T) {
+	tests := []struct {
+		d    time.Duration
+		want string
+	}{
+		{5 * time.Second, "5s"},
+		{65 * time.Second, "1m 5s"},
+		{3661 * time.Second, "1h 1m 1s"},
+		{0, "0s"},
+	}
+
+	for _, tt := range tests {
+		got := FormatDuration(tt.d)
+		if got != tt.want {
+			t.Errorf("FormatDuration(%v) = %q, want %q", tt.d, got, tt.want)
+		}
+	}
+}
+
+func TestFormatSessionEntry(t *testing.T) {
+	start := time.Date(2026, 4, 5, 14, 30, 22, 0, time.UTC)
+	end := time.Date(2026, 4, 5, 15, 45, 10, 0, time.UTC)
+
+	info := &SessionInfo{
+		Agent:     "claude",
+		Mode:      "local",
+		StartTime: start,
+		EndTime:   end,
+		Diff: &ManifestDiff{
+			Added:    []string{"output/migration-plan.md", "output/schema.sql"},
+			Modified: []string{"notes.md", "CLAUDE.md"},
+			Deleted:  nil,
+		},
+	}
+
+	entry := FormatSessionEntry(info)
+
+	// Check required fields
+	checks := []string{
+		"Session 2026-04-05 14:30:22",
+		"Agent:    claude",
+		"Mode:     local",
+		"Start:    2026-04-05 14:30:22",
+		"End:      2026-04-05 15:45:10",
+		"Duration: 1h 14m 48s",
+		"output/migration-plan.md",
+		"output/schema.sql",
+		"notes.md",
+		"CLAUDE.md",
+		"Notes updated: yes",
+	}
+	for _, check := range checks {
+		if !strings.Contains(entry, check) {
+			t.Errorf("entry missing %q", check)
+		}
+	}
+
+	// Deleted should show (none)
+	if !strings.Contains(entry, "Deleted:\n  (none)") {
+		t.Error("expected '(none)' for empty deleted section")
+	}
+}
+
+func TestFormatSessionEntryShortNoChanges(t *testing.T) {
+	start := time.Date(2026, 4, 5, 14, 30, 22, 0, time.UTC)
+	end := start.Add(2 * time.Second)
+
+	info := &SessionInfo{
+		Agent:     "claude",
+		Mode:      "local",
+		StartTime: start,
+		EndTime:   end,
+		Diff:      &ManifestDiff{},
+	}
+
+	entry := FormatSessionEntry(info)
+	if !strings.Contains(entry, "No changes detected") {
+		t.Error("short session with no changes should have 'No changes detected' note")
+	}
+}
+
+func TestAppendSessionLog(t *testing.T) {
+	dir := t.TempDir()
+	os.MkdirAll(filepath.Join(dir, "logs"), 0755)
+
+	start := time.Date(2026, 4, 5, 14, 30, 22, 0, time.UTC)
+	end := time.Date(2026, 4, 5, 15, 0, 0, 0, time.UTC)
+
+	info := &SessionInfo{
+		Agent:     "claude",
+		Mode:      "local",
+		StartTime: start,
+		EndTime:   end,
+		Diff: &ManifestDiff{
+			Added: []string{"output/result.md"},
+		},
+	}
+
+	if err := AppendSessionLog(dir, info); err != nil {
+		t.Fatalf("AppendSessionLog: %v", err)
+	}
+
+	// Append a second entry
+	info2 := &SessionInfo{
+		Agent:     "shell",
+		Mode:      "local",
+		StartTime: end,
+		EndTime:   end.Add(time.Hour),
+		Diff:      &ManifestDiff{},
+	}
+
+	if err := AppendSessionLog(dir, info2); err != nil {
+		t.Fatalf("AppendSessionLog 2: %v", err)
+	}
+
+	data, _ := os.ReadFile(filepath.Join(dir, "logs", "sessions.log"))
+	content := string(data)
+
+	// Should contain both sessions
+	if strings.Count(content, "── Session") != 2 {
+		t.Errorf("expected 2 session entries, got %d", strings.Count(content, "── Session"))
+	}
+}
+
+func TestManifestCleanupOnSuccess(t *testing.T) {
+	dir := t.TempDir()
+	os.MkdirAll(filepath.Join(dir, ".ctask"), 0755)
+	os.MkdirAll(filepath.Join(dir, "logs"), 0755)
+
+	mPath := filepath.Join(dir, ".ctask", "manifest-start.json")
+
+	now := time.Now().UTC().Truncate(time.Second)
+	m := &Manifest{
+		CapturedAt: now,
+		Files:      []FileEntry{{Path: "notes.md", Size: 100, Mtime: now}},
+	}
+	WriteManifest(mPath, m)
+
+	// Simulate successful logging
+	info := &SessionInfo{
+		Agent:     "claude",
+		Mode:      "local",
+		StartTime: now,
+		EndTime:   now.Add(time.Minute),
+		Diff:      &ManifestDiff{},
+	}
+
+	err := AppendSessionLog(dir, info)
+	if err != nil {
+		t.Fatalf("AppendSessionLog: %v", err)
+	}
+
+	// Clean up manifest (as session.Run does)
+	os.Remove(mPath)
+
+	if _, err := os.Stat(mPath); !os.IsNotExist(err) {
+		t.Error("manifest should be cleaned up after successful logging")
+	}
+}
diff --git a/internal/session/manifest.go b/internal/session/manifest.go
index 5912518..e6b4e38 100644
--- a/internal/session/manifest.go
+++ b/internal/session/manifest.go
@@ -32,7 +32,7 @@ func ignoredPath(relPath string) bool {
 		return true
 	}
 	// Ignore sessions.log (ctask's own logging)
-	if relPath == filepath.Join("logs", "sessions.log") {
+	if relPath == "logs/sessions.log" || relPath == "logs\\sessions.log" {
 		return true
 	}
 	return false
diff --git a/internal/session/manifest_test.go b/internal/session/manifest_test.go
new file mode 100644
index 0000000..13c309a
--- /dev/null
+++ b/internal/session/manifest_test.go
@@ -0,0 +1,179 @@
+package session
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+func TestCaptureManifest(t *testing.T) {
+	dir := t.TempDir()
+
+	// Create some files
+	os.WriteFile(filepath.Join(dir, "notes.md"), []byte("hello"), 0644)
+	os.WriteFile(filepath.Join(dir, "task.yaml"), []byte("meta"), 0644)
+	os.MkdirAll(filepath.Join(dir, "output"), 0755)
+	os.WriteFile(filepath.Join(dir, "output", "result.txt"), []byte("result"), 0644)
+
+	m, err := CaptureManifest(dir)
+	if err != nil {
+		t.Fatalf("CaptureManifest: %v", err)
+	}
+
+	if len(m.Files) != 3 {
+		t.Errorf("expected 3 files, got %d", len(m.Files))
+	}
+
+	// Verify paths are forward-slash normalized
+	for _, f := range m.Files {
+		if filepath.IsAbs(f.Path) {
+			t.Errorf("expected relative path, got %q", f.Path)
+		}
+	}
+}
+
+func TestCaptureManifestExcludesCtaskDir(t *testing.T) {
+	dir := t.TempDir()
+
+	os.WriteFile(filepath.Join(dir, "notes.md"), []byte("hello"), 0644)
+	os.MkdirAll(filepath.Join(dir, ".ctask"), 0755)
+	os.WriteFile(filepath.Join(dir, ".ctask", "manifest-start.json"), []byte("{}"), 0644)
+
+	m, err := CaptureManifest(dir)
+	if err != nil {
+		t.Fatalf("CaptureManifest: %v", err)
+	}
+
+	for _, f := range m.Files {
+		if f.Path == ".ctask/manifest-start.json" {
+			t.Error(".ctask/ contents should be excluded from manifest")
+		}
+	}
+}
+
+func TestWriteAndReadManifest(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, ".ctask", "manifest-start.json")
+
+	now := time.Now().UTC().Truncate(time.Second)
+	m := &Manifest{
+		CapturedAt: now,
+		Files: []FileEntry{
+			{Path: "notes.md", Size: 100, Mtime: now},
+		},
+	}
+
+	if err := WriteManifest(path, m); err != nil {
+		t.Fatalf("WriteManifest: %v", err)
+	}
+
+	got, err := ReadManifest(path)
+	if err != nil {
+		t.Fatalf("ReadManifest: %v", err)
+	}
+
+	if len(got.Files) != 1 {
+		t.Fatalf("expected 1 file, got %d", len(got.Files))
+	}
+	if got.Files[0].Path != "notes.md" {
+		t.Errorf("path: got %q", got.Files[0].Path)
+	}
+}
+
+func TestDiffManifests(t *testing.T) {
+	now := time.Now().UTC().Truncate(time.Second)
+	later := now.Add(time.Minute)
+
+	start := &Manifest{
+		CapturedAt: now,
+		Files: []FileEntry{
+			{Path: "notes.md", Size: 100, Mtime: now},
+			{Path: "CLAUDE.md", Size: 200, Mtime: now},
+			{Path: "old-file.txt", Size: 50, Mtime: now},
+		},
+	}
+
+	end := &Manifest{
+		CapturedAt: later,
+		Files: []FileEntry{
+			{Path: "notes.md", Size: 150, Mtime: later},   // modified (size + mtime)
+			{Path: "CLAUDE.md", Size: 200, Mtime: now},     // unchanged
+			{Path: "output/result.md", Size: 300, Mtime: later}, // added
+		},
+	}
+
+	diff := DiffManifests(start, end)
+
+	if len(diff.Added) != 1 || diff.Added[0] != "output/result.md" {
+		t.Errorf("Added: got %v, want [output/result.md]", diff.Added)
+	}
+
+	if len(diff.Modified) != 1 || diff.Modified[0] != "notes.md" {
+		t.Errorf("Modified: got %v, want [notes.md]", diff.Modified)
+	}
+
+	if len(diff.Deleted) != 1 || diff.Deleted[0] != "old-file.txt" {
+		t.Errorf("Deleted: got %v, want [old-file.txt]", diff.Deleted)
+	}
+}
+
+func TestDiffManifestsIgnoreRules(t *testing.T) {
+	now := time.Now().UTC().Truncate(time.Second)
+	later := now.Add(time.Minute)
+
+	start := &Manifest{
+		CapturedAt: now,
+		Files: []FileEntry{
+			{Path: "notes.md", Size: 100, Mtime: now},
+			{Path: "task.yaml", Size: 200, Mtime: now},
+			{Path: "logs/sessions.log", Size: 50, Mtime: now},
+			{Path: ".ctask/manifest-start.json", Size: 300, Mtime: now},
+		},
+	}
+
+	end := &Manifest{
+		CapturedAt: later,
+		Files: []FileEntry{
+			{Path: "notes.md", Size: 100, Mtime: now},      // unchanged
+			{Path: "task.yaml", Size: 250, Mtime: later},    // changed but ignored
+			{Path: "logs/sessions.log", Size: 100, Mtime: later}, // changed but ignored
+			{Path: ".ctask/manifest-start.json", Size: 300, Mtime: now}, // ignored
+		},
+	}
+
+	diff := DiffManifests(start, end)
+
+	if len(diff.Added) != 0 {
+		t.Errorf("Added should be empty (ignore rules), got %v", diff.Added)
+	}
+	if len(diff.Modified) != 0 {
+		t.Errorf("Modified should be empty (ignore rules), got %v", diff.Modified)
+	}
+	if len(diff.Deleted) != 0 {
+		t.Errorf("Deleted should be empty (ignore rules), got %v", diff.Deleted)
+	}
+}
+
+func TestNotesUpdated(t *testing.T) {
+	diff := &ManifestDiff{
+		Modified: []string{"CLAUDE.md", "notes.md"},
+	}
+	if !NotesUpdated(diff) {
+		t.Error("expected NotesUpdated=true when notes.md in Modified")
+	}
+
+	diff2 := &ManifestDiff{
+		Modified: []string{"CLAUDE.md"},
+	}
+	if NotesUpdated(diff2) {
+		t.Error("expected NotesUpdated=false when notes.md not changed")
+	}
+
+	diff3 := &ManifestDiff{
+		Added: []string{"notes.md"},
+	}
+	if !NotesUpdated(diff3) {
+		t.Error("expected NotesUpdated=true when notes.md in Added")
+	}
+}