diff --git a/cmd/attach.go b/cmd/attach.go
new file mode 100644
index 0000000..39a7cf5
--- /dev/null
+++ b/cmd/attach.go
@@ -0,0 +1,61 @@
+package cmd
+
+import (
+	"fmt"
+	"path/filepath"
+	"time"
+
+	"github.com/spf13/cobra"
+	"github.com/warrenronsiek/ctask/internal/config"
+	"github.com/warrenronsiek/ctask/internal/workspace"
+)
+
+var attachCmd = &cobra.Command{
+	Use:          "attach <workspace>",
+	Short:        "Attach to a workspace via tmux (always uses persistent session, regardless of CTASK_SESSION_MODE)",
+	Args:         cobra.ExactArgs(1),
+	SilenceUsage: true,
+	RunE:         runAttach,
+}
+
+var (
+	attachAgent string
+	attachForce bool
+)
+
+func init() {
+	attachCmd.Flags().StringVarP(&attachAgent, "agent", "a", "", "Override agent command")
+	attachCmd.Flags().BoolVar(&attachForce, "force", false, "Skip active-session and stale-workspace warnings (owner-create path only)")
+	attachCmd.ValidArgsFunction = completeWorkspaces(completionActive)
+	rootCmd.AddCommand(attachCmd)
+}
+
+func runAttach(cmd *cobra.Command, args []string) error {
+	roots := config.SearchRoots()
+	// Active-only resolution per spec §9 (matches resume's completion filter).
+	ws := resolveOne(roots, args[0], false)
+
+	// updated_at bump (existing v0.4 behavior).
+	now := time.Now().UTC().Truncate(time.Second)
+	ws.Meta.UpdatedAt = now
+	metaPath := filepath.Join(ws.Path, "task.yaml")
+	if err := workspace.WriteMetaLocked(metaPath, ws.Meta); err != nil {
+		return fmt.Errorf("updating metadata: %w", err)
+	}
+
+	agent := attachAgent
+	if agent == "" {
+		agent = ws.Meta.Agent
+	}
+
+	return runWorkspaceEntry(WorkspaceEntryOptions{
+		WsPath:           ws.Path,
+		WsRoot:           ws.Root,
+		WsMeta:           ws.Meta,
+		Agent:            agent,
+		Shell:            false, // attach defaults to agent
+		Force:            attachForce,
+		AlwaysPersistent: true, // attach is always tmux, regardless of env
+		CommandName:      "attach",
+	})
+}
diff --git a/cmd/attach_test.go b/cmd/attach_test.go
new file mode 100644
index 0000000..c6903b9
--- /dev/null
+++ b/cmd/attach_test.go
@@ -0,0 +1,102 @@
+package cmd
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/spf13/cobra"
+	"github.com/warrenronsiek/ctask/internal/workspace"
+)
+
+// Tests in this file mutate runWorkspaceEntry. Do not run with t.Parallel().
+
+func TestAttachCommandRegistered(t *testing.T) {
+	var found *cobra.Command
+	for _, c := range rootCmd.Commands() {
+		if c.Name() == "attach" {
+			found = c
+			break
+		}
+	}
+	if found == nil {
+		t.Fatal("attach command not registered")
+	}
+}
+
+func TestAttachRefusesDirectFlag(t *testing.T) {
+	for _, c := range rootCmd.Commands() {
+		if c.Name() != "attach" {
+			continue
+		}
+		if c.Flags().Lookup("direct") != nil {
+			t.Error("--direct flag must NOT exist on attach (always-tmux)")
+		}
+		if c.ValidArgsFunction == nil {
+			t.Error("attach must have ValidArgsFunction for tab completion")
+		}
+		return
+	}
+	t.Fatal("attach command not registered")
+}
+
+// attach must call runWorkspaceEntry with AlwaysPersistent: true,
+// Shell: false (defaults to agent), and CommandName: "attach". We use a
+// fresh workspace fixture so resolveOne returns a real workspace, then
+// stub runWorkspaceEntry to capture the opts.
+func TestAttachForwardsToEntryHelperWithAlwaysPersistent(t *testing.T) {
+	root := t.TempDir()
+	wsDir := filepath.Join(root, "general", "2026-05-08_attach-fwd-demo")
+	if err := os.MkdirAll(wsDir, 0755); err != nil {
+		t.Fatalf("mkdir: %v", err)
+	}
+	now := time.Now().UTC().Truncate(time.Second)
+	meta := &workspace.TaskMeta{
+		ID: "t", Slug: "attach-fwd-demo", Title: "attach-fwd-demo",
+		CreatedAt: now, UpdatedAt: now,
+		Status: "active", Category: "general", Type: "task",
+		Mode: "local", Agent: "claude",
+	}
+	if err := workspace.WriteMeta(filepath.Join(wsDir, "task.yaml"), meta); err != nil {
+		t.Fatalf("WriteMeta: %v", err)
+	}
+
+	prevRoot := os.Getenv("CTASK_ROOT")
+	os.Setenv("CTASK_ROOT", root)
+	t.Cleanup(func() {
+		if prevRoot == "" {
+			os.Unsetenv("CTASK_ROOT")
+		} else {
+			os.Setenv("CTASK_ROOT", prevRoot)
+		}
+	})
+
+	var captured WorkspaceEntryOptions
+	orig := runWorkspaceEntry
+	runWorkspaceEntry = func(opts WorkspaceEntryOptions) error {
+		captured = opts
+		return nil
+	}
+	t.Cleanup(func() { runWorkspaceEntry = orig })
+
+	prevAgent, prevForce := attachAgent, attachForce
+	attachAgent, attachForce = "", false
+	t.Cleanup(func() {
+		attachAgent = prevAgent
+		attachForce = prevForce
+	})
+
+	if err := runAttach(attachCmd, []string{"attach-fwd-demo"}); err != nil {
+		t.Fatalf("runAttach: %v", err)
+	}
+	if !captured.AlwaysPersistent {
+		t.Error("attach must set AlwaysPersistent=true")
+	}
+	if captured.Shell {
+		t.Error("attach defaults to agent, Shell must be false")
+	}
+	if captured.CommandName != "attach" {
+		t.Errorf("CommandName: got %q, want %q", captured.CommandName, "attach")
+	}
+}