diff --git a/cmd/build.go b/cmd/build.go
index 7ecb4c3b..c8461e32 100644
--- a/cmd/build.go
+++ b/cmd/build.go
@@ -214,6 +214,9 @@ func buildInternal(ctx context.Context, inv cmdutil.InvocationContext, opts ...B
 	groupRootCommands(rootCmd)
 
 	installUnknownSubcommandGuard(rootCmd)
+	// Bare `lark-cli` in an interactive terminal offers an interactive upgrade
+	// before printing help; non-bare invocations and non-TTY are unaffected.
+	installRootUpgradePrompt(f, rootCmd)
 
 	if mode := f.ResolveStrictMode(ctx); mode.IsActive() && !cfg.skipStrictMode {
 		pruneForStrictMode(rootCmd, mode)
diff --git a/cmd/root_upgrade.go b/cmd/root_upgrade.go
new file mode 100644
index 00000000..eadec786
--- /dev/null
+++ b/cmd/root_upgrade.go
@@ -0,0 +1,90 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package cmd
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"strings"
+
+	"github.com/larksuite/cli/internal/build"
+	"github.com/larksuite/cli/internal/cmdutil"
+	"github.com/larksuite/cli/internal/update"
+	"github.com/spf13/cobra"
+)
+
+// runRootUpgrade locates the registered `update` subcommand and runs it, so the
+// interactive root-command upgrade reuses exactly `lark-cli update` behavior
+// (install-method detection, output, error handling). Package-level var so
+// tests can stub it and avoid real network / self-update.
+var runRootUpgrade = func(cmd *cobra.Command) {
+	for _, c := range cmd.Root().Commands() {
+		if c.Name() == "update" && c.RunE != nil {
+			_ = c.RunE(c, nil) // update prints its own output/errors; swallow here
+			return
+		}
+	}
+}
+
+// isBareRootInvocation reports whether this is a bare `lark-cli` (no subcommand,
+// no flags) — the only invocation that triggers the interactive upgrade prompt.
+// Mirrors unknownSubcommandRunE's "bare group prints help" branch: args empty
+// AND no flag tokens in the raw invocation.
+func isBareRootInvocation(args []string) bool {
+	return len(args) == 0 && len(flagTokensInArgs(rawInvocationArgs)) == 0
+}
+
+// readYes reads one line and reports whether it is an affirmative y/yes.
+// EOF / empty / anything else → false (default No, matching the [y/N] prompt).
+func readYes(r io.Reader) bool {
+	line, _ := bufio.NewReader(r).ReadString('\n')
+	switch strings.ToLower(strings.TrimSpace(line)) {
+	case "y", "yes":
+		return true
+	default:
+		return false
+	}
+}
+
+// offerRootUpgrade prompts for an interactive upgrade when running bare
+// `lark-cli` in an interactive terminal with a cached newer version. Every
+// failure is swallowed — it must never affect help output or the exit code.
+func offerRootUpgrade(f *cmdutil.Factory, cmd *cobra.Command) {
+	ios := f.IOStreams
+	// Gates 1/2/3: need to read stdin AND show the prompt on stderr, and require
+	// stdout TTY too so this only fires in a pure foreground terminal session.
+	if !ios.IsTerminal || !ios.OutIsTerminal || !ios.StderrIsTerminal {
+		return
+	}
+	// Gate 4: cached newer version. CheckCached applies opt-out (shouldSkip)
+	// and the IsNewer/semver validation chain; it reads the on-disk cache that
+	// the 24h-throttled RefreshCache maintains (CheckCached itself has no TTL).
+	info := update.CheckCached(build.Version)
+	if info == nil {
+		return
+	}
+	fmt.Fprintf(ios.ErrOut, "lark-cli %s available (current %s). Upgrade now? [y/N]: ", info.Latest, info.Current)
+	if !readYes(ios.In) {
+		return
+	}
+	runRootUpgrade(cmd)
+}
+
+// installRootUpgradePrompt wraps the root command's RunE (set to
+// unknownSubcommandRunE by installUnknownSubcommandGuard) so a bare `lark-cli`
+// invocation offers an interactive upgrade before printing help. Non-bare
+// invocations are passed straight through, unchanged.
+func installRootUpgradePrompt(f *cmdutil.Factory, root *cobra.Command) {
+	inner := root.RunE
+	if inner == nil {
+		return
+	}
+	root.RunE = func(cmd *cobra.Command, args []string) error {
+		if isBareRootInvocation(args) {
+			offerRootUpgrade(f, cmd)
+		}
+		return inner(cmd, args)
+	}
+}
diff --git a/cmd/root_upgrade_test.go b/cmd/root_upgrade_test.go
new file mode 100644
index 00000000..bc28b858
--- /dev/null
+++ b/cmd/root_upgrade_test.go
@@ -0,0 +1,191 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package cmd
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/larksuite/cli/internal/build"
+	"github.com/larksuite/cli/internal/cmdutil"
+	"github.com/larksuite/cli/internal/core"
+	"github.com/spf13/cobra"
+)
+
+func writeUpdateState(t *testing.T, dir, latest string) {
+	t.Helper()
+	data := fmt.Sprintf(`{"latest_version":%q,"checked_at":%d}`, latest, time.Now().Unix())
+	if err := os.WriteFile(filepath.Join(dir, "update-state.json"), []byte(data), 0o644); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestReadYes(t *testing.T) {
+	cases := map[string]bool{
+		"y\n": true, "Y\n": true, "yes\n": true, "YES\n": true, " y \n": true,
+		"n\n": false, "\n": false, "": false, "nope\n": false, "yeah\n": false,
+	}
+	for in, want := range cases {
+		if got := readYes(strings.NewReader(in)); got != want {
+			t.Errorf("readYes(%q) = %v, want %v", in, got, want)
+		}
+	}
+}
+
+func TestIsBareRootInvocation(t *testing.T) {
+	orig := rawInvocationArgs
+	t.Cleanup(func() { rawInvocationArgs = orig })
+
+	rawInvocationArgs = nil
+	if !isBareRootInvocation([]string{}) {
+		t.Error("empty args + no raw flag tokens should be bare")
+	}
+	rawInvocationArgs = []string{"--profile", "x"}
+	if isBareRootInvocation([]string{}) {
+		t.Error("flag token present → not bare")
+	}
+	rawInvocationArgs = nil
+	if isBareRootInvocation([]string{"im"}) {
+		t.Error("positional arg → not bare")
+	}
+}
+
+func TestOfferRootUpgrade(t *testing.T) {
+	origV := build.Version
+	build.Version = "1.0.0" // release version so shouldSkip()==false
+	t.Cleanup(func() { build.Version = origV })
+
+	origRun := runRootUpgrade
+	t.Cleanup(func() { runRootUpgrade = origRun })
+
+	// This test builds a Factory literal (no NewDefault), so it never runs
+	// workspace detection; pin the process-global workspace to Local so
+	// statePath() resolves under LARKSUITE_CLI_CONFIG_DIR rather than a stale
+	// subdir inherited from a prior test in the package.
+	origWS := core.CurrentWorkspace()
+	t.Cleanup(func() { core.SetCurrentWorkspace(origWS) })
+	core.SetCurrentWorkspace(core.WorkspaceLocal)
+
+	cases := []struct {
+		name                string
+		in, out, err        bool
+		input               string
+		latest              string // "" → no state file (CheckCached nil)
+		optOut              bool
+		wantPrompt, wantRun bool
+	}{
+		{"all-tty+y", true, true, true, "y\n", "2.0.0", false, true, true},
+		{"all-tty+yes", true, true, true, "yes\n", "2.0.0", false, true, true},
+		{"all-tty+n", true, true, true, "n\n", "2.0.0", false, true, false},
+		{"all-tty+empty", true, true, true, "\n", "2.0.0", false, true, false},
+		{"all-tty+eof", true, true, true, "", "2.0.0", false, true, false},
+		{"stdin-not-tty", false, true, true, "y\n", "2.0.0", false, false, false},
+		{"stdout-not-tty", true, false, true, "y\n", "2.0.0", false, false, false},
+		{"stderr-not-tty", true, true, false, "y\n", "2.0.0", false, false, false},
+		{"no-newer-version", true, true, true, "y\n", "", false, false, false},
+		{"already-latest", true, true, true, "y\n", "1.0.0", false, false, false}, // post-upgrade: current == cached latest → no prompt
+		{"cache-older-than-current", true, true, true, "y\n", "0.9.0", false, false, false},
+		{"opt-out", true, true, true, "y\n", "2.0.0", true, false, false},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			dir := t.TempDir()
+			t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+			// Clear env that update.shouldSkip treats as "suppress" so the
+			// test is deterministic regardless of host (GitHub Actions sets
+			// CI=true, which would otherwise suppress the prompt).
+			t.Setenv("CI", "")
+			t.Setenv("BUILD_NUMBER", "")
+			t.Setenv("RUN_ID", "")
+			t.Setenv("LARKSUITE_CLI_NO_UPDATE_NOTIFIER", "")
+			if tc.latest != "" {
+				writeUpdateState(t, dir, tc.latest)
+			}
+			if tc.optOut {
+				t.Setenv("LARKSUITE_CLI_NO_UPDATE_NOTIFIER", "1")
+			}
+			called := false
+			runRootUpgrade = func(*cobra.Command) { called = true }
+
+			var errBuf bytes.Buffer
+			f := &cmdutil.Factory{IOStreams: &cmdutil.IOStreams{
+				In:               strings.NewReader(tc.input),
+				Out:              &bytes.Buffer{},
+				ErrOut:           &errBuf,
+				IsTerminal:       tc.in,
+				OutIsTerminal:    tc.out,
+				StderrIsTerminal: tc.err,
+			}}
+			offerRootUpgrade(f, &cobra.Command{})
+
+			gotPrompt := strings.Contains(errBuf.String(), "available")
+			if gotPrompt != tc.wantPrompt {
+				t.Errorf("prompt: got %v want %v (stderr=%q)", gotPrompt, tc.wantPrompt, errBuf.String())
+			}
+			if called != tc.wantRun {
+				t.Errorf("runRootUpgrade called: got %v want %v", called, tc.wantRun)
+			}
+		})
+	}
+}
+
+func TestInstallRootUpgradePromptPreservesInner(t *testing.T) {
+	orig := rawInvocationArgs
+	t.Cleanup(func() { rawInvocationArgs = orig })
+	rawInvocationArgs = nil
+
+	innerCalls := 0
+	root := &cobra.Command{Use: "lark-cli"}
+	root.RunE = func(cmd *cobra.Command, args []string) error { innerCalls++; return nil }
+
+	f := &cmdutil.Factory{IOStreams: &cmdutil.IOStreams{
+		In: strings.NewReader(""), Out: &bytes.Buffer{}, ErrOut: &bytes.Buffer{},
+	}}
+	installRootUpgradePrompt(f, root)
+
+	if err := root.RunE(root, []string{}); err != nil {
+		t.Fatalf("bare RunE err = %v", err)
+	}
+	if err := root.RunE(root, []string{"im"}); err != nil {
+		t.Fatalf("non-bare RunE err = %v", err)
+	}
+	if innerCalls != 2 {
+		t.Errorf("inner RunE should run for both bare and non-bare, got %d", innerCalls)
+	}
+}
+
+// TestRunRootUpgradeDispatchesToUpdate covers the real runRootUpgrade dispatch
+// path (not the stub used elsewhere): from any command it must locate the
+// registered "update" subcommand via cmd.Root() and invoke its RunE.
+func TestRunRootUpgradeDispatchesToUpdate(t *testing.T) {
+	root := &cobra.Command{Use: "lark-cli"}
+	ran := 0
+	root.AddCommand(&cobra.Command{Use: "update", RunE: func(*cobra.Command, []string) error { ran++; return nil }})
+	child := &cobra.Command{Use: "im"}
+	root.AddCommand(child)
+
+	runRootUpgrade(child) // child.Root() resolves to root, which has "update"
+
+	if ran != 1 {
+		t.Errorf("runRootUpgrade should locate and run update's RunE once, got %d", ran)
+	}
+}
+
+// TestInstallRootUpgradePromptNilInnerNoop covers the inner == nil guard:
+// when root has no RunE, installRootUpgradePrompt must not wrap it.
+func TestInstallRootUpgradePromptNilInnerNoop(t *testing.T) {
+	root := &cobra.Command{Use: "lark-cli"} // RunE is nil
+	f := &cmdutil.Factory{IOStreams: &cmdutil.IOStreams{
+		In: strings.NewReader(""), Out: &bytes.Buffer{}, ErrOut: &bytes.Buffer{},
+	}}
+	installRootUpgradePrompt(f, root)
+	if root.RunE != nil {
+		t.Error("installRootUpgradePrompt must not wrap a nil RunE (inner==nil guard)")
+	}
+}
diff --git a/internal/cmdutil/iostreams.go b/internal/cmdutil/iostreams.go
index a067b67d..b5f7c65a 100644
--- a/internal/cmdutil/iostreams.go
+++ b/internal/cmdutil/iostreams.go
@@ -18,6 +18,9 @@ type IOStreams struct {
 	Out        io.Writer
 	ErrOut     io.Writer
 	IsTerminal bool
+	// OutIsTerminal reports whether Out is an interactive terminal. Mirrors
+	// IsTerminal; computed once in NewIOStreams and assignable directly in tests.
+	OutIsTerminal bool
 	// StderrIsTerminal reports whether ErrOut is an interactive terminal.
 	// Advisory warnings written to stderr (e.g. the proxy notice) gate on this
 	// so they stay out of non-interactive output (pipes, CI, agent runs).
@@ -27,19 +30,24 @@ type IOStreams struct {
 }
 
 // NewIOStreams builds an IOStreams from arbitrary readers/writers.
-// IsTerminal / StderrIsTerminal are derived from in's / errOut's underlying
-// *os.File, if any; non-file streams (bytes.Buffer, strings.Reader, …) yield
-// false.
+// IsTerminal / OutIsTerminal / StderrIsTerminal are each derived from the
+// underlying *os.File of in / out / errOut respectively; non-file
+// readers/writers (bytes.Buffer, strings.Reader, …) yield false.
 func NewIOStreams(in io.Reader, out, errOut io.Writer) *IOStreams {
-	isTerminal := false
-	if f, ok := in.(*os.File); ok {
-		isTerminal = term.IsTerminal(int(f.Fd()))
+	fileIsTerminal := func(v any) bool {
+		if f, ok := v.(*os.File); ok {
+			return term.IsTerminal(int(f.Fd()))
+		}
+		return false
 	}
-	stderrIsTerminal := false
-	if f, ok := errOut.(*os.File); ok {
-		stderrIsTerminal = term.IsTerminal(int(f.Fd()))
+	return &IOStreams{
+		In:               in,
+		Out:              out,
+		ErrOut:           errOut,
+		IsTerminal:       fileIsTerminal(in),
+		OutIsTerminal:    fileIsTerminal(out),
+		StderrIsTerminal: fileIsTerminal(errOut),
 	}
-	return &IOStreams{In: in, Out: out, ErrOut: errOut, IsTerminal: isTerminal, StderrIsTerminal: stderrIsTerminal}
 }
 
 // SystemIO creates an IOStreams wired to the process's standard file descriptors.
diff --git a/internal/cmdutil/iostreams_test.go b/internal/cmdutil/iostreams_test.go
new file mode 100644
index 00000000..bf6910d9
--- /dev/null
+++ b/internal/cmdutil/iostreams_test.go
@@ -0,0 +1,31 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package cmdutil
+
+import (
+	"bytes"
+	"os"
+	"testing"
+)
+
+func TestNewIOStreamsTerminalFlagsNonFile(t *testing.T) {
+	s := NewIOStreams(&bytes.Buffer{}, &bytes.Buffer{}, &bytes.Buffer{})
+	if s.IsTerminal || s.OutIsTerminal || s.StderrIsTerminal {
+		t.Errorf("non-file streams must not be terminals: in=%v out=%v err=%v",
+			s.IsTerminal, s.OutIsTerminal, s.StderrIsTerminal)
+	}
+}
+
+func TestNewIOStreamsTerminalFlagsPipe(t *testing.T) {
+	r, w, err := os.Pipe()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer r.Close()
+	defer w.Close()
+	s := NewIOStreams(r, w, w)
+	if s.OutIsTerminal || s.StderrIsTerminal {
+		t.Errorf("os.Pipe must not be a terminal: out=%v err=%v", s.OutIsTerminal, s.StderrIsTerminal)
+	}
+}