diff --git a/cmd/entire/cli/migrate.go b/cmd/entire/cli/migrate.go
--- a/cmd/entire/cli/migrate.go
+++ b/cmd/entire/cli/migrate.go
@@ -359,14 +359,18 @@
 		return err
 	}
 
+	latestSessionIdx := -1
+	if len(summary.Sessions) > 0 {
+		latestSessionIdx = len(summary.Sessions) - 1
+	}
+
 	// Legacy v1 layout stores task metadata at checkpoint root: <cp>/tasks/<tool-use-id>/...
-	// Prefer attaching this tree to the latest session in v2.
-	if rootTasksTree, rootTasksErr := v1Tree.Tree("tasks"); rootTasksErr == nil {
-		if len(summary.Sessions) > 0 {
-			latestSessionIdx := len(summary.Sessions) - 1
-			if spliceErr := spliceTasksTreeToV2(repo, v2Store, cpID, latestSessionIdx, rootTasksTree.Hash); spliceErr != nil {
-				return fmt.Errorf("latest session task tree splice failed: %w", spliceErr)
-			}
+	// Attach this to the latest session in v2, and merge with that session's own tasks if present.
+	var rootTasksTree *object.Tree
+	rootTasksSpliced := false
+	if latestSessionIdx >= 0 {
+		if tasksTree, rootTasksErr := v1Tree.Tree("tasks"); rootTasksErr == nil {
+			rootTasksTree = tasksTree
 		}
 	}
 
@@ -382,11 +386,33 @@
 			continue // No tasks directory in this session
 		}
 
-		if spliceErr := spliceTasksTreeToV2(repo, v2Store, cpID, sessionIdx, tasksTree.Hash); spliceErr != nil {
+		tasksTreeHash := tasksTree.Hash
+		if rootTasksTree != nil && sessionIdx == latestSessionIdx {
+			mergedTasksTreeHash, mergeErr := checkpoint.UpdateSubtree(
+				repo,
+				rootTasksTree.Hash,
+				nil,
+				tasksTree.Entries,
+				checkpoint.UpdateSubtreeOptions{MergeMode: checkpoint.MergeKeepExisting},
+			)
+			if mergeErr != nil {
+				return fmt.Errorf("failed to merge root and session task trees for session %d: %w", sessionIdx, mergeErr)
+			}
+			tasksTreeHash = mergedTasksTreeHash
+			rootTasksSpliced = true
+		}
+
+		if spliceErr := spliceTasksTreeToV2(repo, v2Store, cpID, sessionIdx, tasksTreeHash); spliceErr != nil {
 			return fmt.Errorf("session %d task tree splice failed: %w", sessionIdx, spliceErr)
 		}
 	}
 
+	if rootTasksTree != nil && !rootTasksSpliced {
+		if spliceErr := spliceTasksTreeToV2(repo, v2Store, cpID, latestSessionIdx, rootTasksTree.Hash); spliceErr != nil {
+			return fmt.Errorf("latest session task tree splice failed: %w", spliceErr)
+		}
+	}
+
 	return nil
 }
 

diff --git a/cmd/entire/cli/migrate_test.go b/cmd/entire/cli/migrate_test.go
--- a/cmd/entire/cli/migrate_test.go
+++ b/cmd/entire/cli/migrate_test.go
@@ -228,6 +228,52 @@
 	require.NoError(t, taskFileErr, "expected migrated task checkpoint metadata in /full/current")
 }
 
+func TestMigrateCheckpointsV2_TaskMetadataMergesRootAndSessionTasks(t *testing.T) {
+	t.Parallel()
+	repo := initMigrateTestRepo(t)
+	v1Store, v2Store := newMigrateStores(repo)
+
+	cpID := id.MustCheckpointID("c1d2e3f4a5b6")
+
+	metadataDir := t.TempDir()
+	sessionTaskFile := filepath.Join(metadataDir, "tasks", "toolu_01SESSION", "checkpoint.json")
+	require.NoError(t, os.MkdirAll(filepath.Dir(sessionTaskFile), 0o755))
+	require.NoError(t, os.WriteFile(sessionTaskFile, []byte(`{"source":"session"}`), 0o644))
+
+	// Write one v1 task checkpoint that has both:
+	// 1) root-level task metadata (legacy layout, from IsTask/ToolUseID)
+	// 2) session-level task metadata (from MetadataDir copy into session subtree)
+	err := v1Store.WriteCommitted(context.Background(), checkpoint.WriteCommittedOptions{
+		CheckpointID: cpID,
+		SessionID:    "session-task-merge-001",
+		Strategy:     "manual-commit",
+		Transcript:   []byte("{\"type\":\"assistant\",\"message\":\"task merge\"}\n"),
+		Prompts:      []string{"task merge prompt"},
+		IsTask:       true,
+		ToolUseID:    "toolu_01ROOT",
+		MetadataDir:  metadataDir,
+		AuthorName:   "Test",
+		AuthorEmail:  "test@test.com",
+	})
+	require.NoError(t, err)
+
+	var stdout bytes.Buffer
+	result, migrateErr := migrateCheckpointsV2(context.Background(), repo, v1Store, v2Store, &stdout)
+	require.NoError(t, migrateErr)
+	assert.Equal(t, 1, result.migrated)
+
+	_, rootTreeHash, refErr := v2Store.GetRefState(plumbing.ReferenceName(paths.V2FullCurrentRefName))
+	require.NoError(t, refErr)
+	rootTree, treeErr := repo.TreeObject(rootTreeHash)
+	require.NoError(t, treeErr)
+
+	// Both root-level and per-session tasks must exist after migration.
+	_, rootTaskErr := rootTree.File(cpID.Path() + "/0/tasks/toolu_01ROOT/checkpoint.json")
+	require.NoError(t, rootTaskErr, "expected root-level task metadata in /full/current")
+	_, sessionTaskErr := rootTree.File(cpID.Path() + "/0/tasks/toolu_01SESSION/checkpoint.json")
+	require.NoError(t, sessionTaskErr, "expected session-level task metadata in /full/current")
+}
+
 func TestMigrateCheckpointsV2_AllSkippedOnRerun(t *testing.T) {
 	t.Parallel()
 	repo := initMigrateTestRepo(t)