diff --git a/README.md b/README.md
index 71c4ab0..124b356 100644
--- a/README.md
+++ b/README.md
@@ -99,11 +99,11 @@ Columns:
 
 ### `git-wt migrate`
 
-Bring existing branch worktrees under `git-wt` management.
+Bring existing Git worktrees under `git-wt` management.
 
 - Moves the main worktree into `<root>/main/<repo-name>` when it is still a plain clone at `<root>` or on the old layout at `<root>/main`.
-- Creates managed worktrees for local branches that do not already have one.
 - Renames existing non-managed branch worktrees into the managed path format.
+- Does not create worktrees for local branches that do not already have one.
 
 Use `--prompt` | `-p` to review the proposed migrations before applying them.
 
diff --git a/internal/gitwt/gitwt_migrate.go b/internal/gitwt/gitwt_migrate.go
index 9477bf8..e34773c 100644
--- a/internal/gitwt/gitwt_migrate.go
+++ b/internal/gitwt/gitwt_migrate.go
@@ -259,8 +259,7 @@ func migrationCandidatesFromRepository(repository *Repository) ([]migrateCandida
 		return nil, fmt.Errorf("get current directory: %w", err)
 	}
 
-	branchesByWorktree := make(map[string]string, len(porcelainWorktrees))
-	candidates := make([]migrateCandidate, 0)
+	candidates := make([]migrateCandidate, 0, len(porcelainWorktrees))
 	for _, porcelainWorktree := range porcelainWorktrees {
 		if porcelainWorktree.BranchRef == "" {
 			continue
@@ -271,7 +270,6 @@ func migrationCandidatesFromRepository(repository *Repository) ([]migrateCandida
 			continue
 		}
 
-		branchesByWorktree[branchName] = porcelainWorktree.Path
 		if filepath.Clean(porcelainWorktree.Path) == filepath.Clean(mainPath) {
 			continue
 		}
@@ -291,25 +289,6 @@ func migrationCandidatesFromRepository(repository *Repository) ([]migrateCandida
 		})
 	}
 
-	branches, err := repository.localBranches()
-	if err != nil {
-		return nil, err
-	}
-
-	for _, branchName := range branches {
-		if _, ok := branchesByWorktree[branchName]; ok {
-			continue
-		}
-
-		targetPath := managedWorktreePath(mainPath, branchName)
-		candidates = append(candidates, migrateCandidate{
-			Action:            "create",
-			Name:              branchName,
-			TargetPath:        targetPath,
-			DisplayTargetPath: currentRelativePath(currentDirectory, targetPath),
-		})
-	}
-
 	slices.SortFunc(candidates, func(left, right migrateCandidate) int {
 		return cmp.Compare(left.Name, right.Name)
 	})
diff --git a/internal/gitwt/gitwt_test.go b/internal/gitwt/gitwt_test.go
index 017ae67..a828133 100644
--- a/internal/gitwt/gitwt_test.go
+++ b/internal/gitwt/gitwt_test.go
@@ -905,6 +905,8 @@ func TestListFailsWhenBranchHasNoUpstream(t *testing.T) {
 
 	testRepository := newTestRepository(t)
 	testRepository.createLocalBranch(t, branchName)
+	legacyPath := filepath.Join(testRepository.rootPath, "legacy-no-upstream")
+	runGitCommand(t, testRepository.mainPath, "worktree", "add", legacyPath, branchName)
 	testRepository.runGitWT(t, "migrate")
 
 	result := testRepository.runGitWT(t, "list")
@@ -1143,7 +1145,7 @@ func TestMigrateMovesPlainCloneMainIntoNestedLayout(t *testing.T) {
 	}
 }
 
-func TestMigratePlainCloneCreatesBranchWorktreesUnderRoot(t *testing.T) {
+func TestMigratePlainCloneLeavesExistingBranchesWithoutWorktrees(t *testing.T) {
 	const branchName = "dev"
 
 	testRepository := newPlainCloneTestRepository(t)
@@ -1158,13 +1160,9 @@ func TestMigratePlainCloneCreatesBranchWorktreesUnderRoot(t *testing.T) {
 	}
 
 	testRepository.assertPathPresent(t, nestedMainPath)
-	testRepository.assertPathPresent(t, nestedBranchPath)
+	testRepository.assertPathMissing(t, nestedBranchPath)
 	assertCurrentBranchAtPath(t, nestedMainPath, "main")
-	assertCurrentBranchAtPath(t, nestedBranchPath, branchName)
 	assertMainWorktreePath(t, nestedMainPath)
-	if filepath.Dir(filepath.Dir(nestedBranchPath)) != testRepository.rootPath {
-		t.Fatalf("expected branch worktree under plain clone root %s, got %s", testRepository.rootPath, nestedBranchPath)
-	}
 }
 
 func TestMigrateMovesMainAndOldLayoutFeatureWorktrees(t *testing.T) {
@@ -1194,7 +1192,7 @@ func TestMigrateMovesMainAndOldLayoutFeatureWorktrees(t *testing.T) {
 	}
 }
 
-func TestMigrateCreatesWorktreesForExistingBranches(t *testing.T) {
+func TestMigrateDoesNotCreateWorktreesForExistingBranches(t *testing.T) {
 	const branchOne = "feature/alpha"
 	const branchTwo = "feature/beta"
 
@@ -1207,10 +1205,8 @@ func TestMigrateCreatesWorktreesForExistingBranches(t *testing.T) {
 		t.Fatalf("migrate failed: %v\n%s", result.err, result.stderr)
 	}
 
-	testRepository.assertPathPresent(t, testRepository.worktreePath(branchOne))
-	testRepository.assertPathPresent(t, testRepository.worktreePath(branchTwo))
-	assertCurrentBranchAtPath(t, testRepository.worktreePath(branchOne), branchOne)
-	assertCurrentBranchAtPath(t, testRepository.worktreePath(branchTwo), branchTwo)
+	testRepository.assertPathMissing(t, testRepository.worktreePath(branchOne))
+	testRepository.assertPathMissing(t, testRepository.worktreePath(branchTwo))
 	testRepository.assertPathPresent(t, testRepository.mainPath)
 	assertCurrentBranchAtPath(t, testRepository.mainPath, "main")
 }