chore: import upstream snapshot with attribution

internal/skillscheck/check.go

@@ -0,0 +1,31 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package skillscheck
+
+import "strings"
+
+// Init runs the synchronous skills version check. Stores a StaleNotice when
+// the local skills state records a version that does not match currentVersion.
+// Safe to call from cmd/root.go before rootCmd.Execute(); zero network, zero
+// subprocess — only a local state file read.
+//
+// Skip rules: see shouldSkip (CI envs, DEV builds, non-release semver,
+// LARKSUITE_CLI_NO_SKILLS_NOTIFIER opt-out).
+func Init(currentVersion string) {
+	SetPending(nil)
+	if shouldSkip(currentVersion) {
+		return
+	}
+	version, ok := ReadSyncedVersion()
+	if !ok {
+		return
+	}
+	if strings.TrimPrefix(strings.TrimPrefix(version, "v"), "V") == strings.TrimPrefix(strings.TrimPrefix(currentVersion, "v"), "V") {
+		return
+	}
+	SetPending(&StaleNotice{
+		Current: version,
+		Target:  currentVersion,
+	})
+}

internal/skillscheck/check_test.go

@@ -0,0 +1,93 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package skillscheck
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func resetPending(t *testing.T) {
+	t.Helper()
+	SetPending(nil)
+	t.Cleanup(func() { SetPending(nil) })
+}
+
+func TestInit_InSync_NoNotice(t *testing.T) {
+	clearSkillsSkipEnv(t)
+	resetPending(t)
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", t.TempDir())
+	if err := WriteState(SkillsState{Version: "1.0.21"}); err != nil {
+		t.Fatal(err)
+	}
+	Init("1.0.21")
+	if got := GetPending(); got != nil {
+		t.Errorf("GetPending() = %+v, want nil (in-sync)", got)
+	}
+}
+
+func TestInit_ColdStart_NoNotice(t *testing.T) {
+	clearSkillsSkipEnv(t)
+	resetPending(t)
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", t.TempDir())
+	Init("1.0.21")
+	if got := GetPending(); got != nil {
+		t.Errorf("GetPending() = %+v, want nil (cold start is silent)", got)
+	}
+}
+
+func TestInit_NormalizedVersion_NoNotice(t *testing.T) {
+	clearSkillsSkipEnv(t)
+	resetPending(t)
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", t.TempDir())
+	if err := WriteState(SkillsState{Version: "1.0.21"}); err != nil {
+		t.Fatal(err)
+	}
+	Init("v1.0.21")
+	if got := GetPending(); got != nil {
+		t.Errorf("GetPending() = %+v, want nil (normalized versions are in-sync)", got)
+	}
+}
+
+func TestInit_Drift_NoticeWithStateVersion(t *testing.T) {
+	clearSkillsSkipEnv(t)
+	resetPending(t)
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", t.TempDir())
+	if err := WriteState(SkillsState{Version: "1.0.20"}); err != nil {
+		t.Fatal(err)
+	}
+	Init("1.0.21")
+	got := GetPending()
+	if got == nil {
+		t.Fatal("GetPending() = nil, want non-nil for drift")
+	}
+	if got.Current != "1.0.20" || got.Target != "1.0.21" {
+		t.Errorf("notice = %+v, want {Current:\"1.0.20\", Target:\"1.0.21\"}", got)
+	}
+}
+
+func TestInit_Skipped_NoNotice(t *testing.T) {
+	clearSkillsSkipEnv(t)
+	resetPending(t)
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", t.TempDir())
+	Init("DEV")
+	if got := GetPending(); got != nil {
+		t.Errorf("GetPending() = %+v, want nil (skip rules met)", got)
+	}
+}
+
+func TestInit_ReadStateError_FailsClosed(t *testing.T) {
+	clearSkillsSkipEnv(t)
+	resetPending(t)
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	if err := os.MkdirAll(filepath.Join(dir, "skills-state.json"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	Init("1.0.21")
+	if got := GetPending(); got != nil {
+		t.Errorf("GetPending() = %+v, want nil (fail closed on I/O error)", got)
+	}
+}

internal/skillscheck/notice.go

@@ -0,0 +1,44 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+// Package skillscheck verifies that the locally installed lark-cli
+// skills are in sync with the running binary version, by comparing
+// the current binary version against skills-state.json. On mismatch it
+// stores a notice for injection into JSON envelopes via output.PendingNotice.
+package skillscheck
+
+import (
+	"fmt"
+	"sync/atomic"
+)
+
+// StaleNotice signals that the locally synced skills version does not
+// match the running binary. Current is the last successfully synced
+// version (always non-empty — Init no longer emits a notice on cold
+// start). Target is the running binary version. Mirrors
+// internal/update.UpdateInfo's pending-notice pattern.
+type StaleNotice struct {
+	Current string `json:"current"`
+	Target  string `json:"target"`
+}
+
+// Message returns a single-line, AI-agent-parseable description of the
+// drift plus the canonical fix command. Mirrors internal/update.UpdateInfo.Message
+// in style ("..., run: lark-cli update" suffix). Current is guaranteed
+// non-empty because Init only emits a StaleNotice for the drift case.
+func (s *StaleNotice) Message() string {
+	return fmt.Sprintf(
+		"lark-cli skills %s out of sync with binary %s, run: lark-cli update",
+		s.Current, s.Target,
+	)
+}
+
+// pending stores the latest stale notice for the current process.
+var pending atomic.Pointer[StaleNotice]
+
+// SetPending stores the stale notice for consumption by output decorators.
+// Pass nil to clear.
+func SetPending(n *StaleNotice) { pending.Store(n) }
+
+// GetPending returns the pending stale notice, or nil.
+func GetPending() *StaleNotice { return pending.Load() }

internal/skillscheck/notice_test.go

@@ -0,0 +1,66 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package skillscheck
+
+import (
+	"sync"
+	"testing"
+)
+
+func TestStaleNotice_Message(t *testing.T) {
+	tests := []struct {
+		name string
+		n    StaleNotice
+		want string
+	}{
+		{
+			"drift",
+			StaleNotice{Current: "1.0.20", Target: "1.0.21"},
+			"lark-cli skills 1.0.20 out of sync with binary 1.0.21, run: lark-cli update",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := tt.n.Message(); got != tt.want {
+				t.Errorf("Message() = %q, want %q", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestSetGetPending(t *testing.T) {
+	SetPending(nil)
+	t.Cleanup(func() { SetPending(nil) })
+
+	if got := GetPending(); got != nil {
+		t.Fatalf("initial GetPending() = %+v, want nil", got)
+	}
+
+	want := &StaleNotice{Current: "1.0.20", Target: "1.0.21"}
+	SetPending(want)
+	got := GetPending()
+	if got == nil || got.Current != "1.0.20" || got.Target != "1.0.21" {
+		t.Errorf("GetPending() = %+v, want %+v", got, want)
+	}
+}
+
+func TestSetGetPending_Concurrent(t *testing.T) {
+	SetPending(nil)
+	t.Cleanup(func() { SetPending(nil) })
+
+	var wg sync.WaitGroup
+	for i := 0; i < 100; i++ {
+		wg.Add(2)
+		go func() {
+			defer wg.Done()
+			SetPending(&StaleNotice{Current: "a", Target: "b"})
+		}()
+		go func() {
+			defer wg.Done()
+			_ = GetPending()
+		}()
+	}
+	wg.Wait()
+	// Just verifying no race; -race flag enforces.
+}

internal/skillscheck/skip.go

@@ -0,0 +1,27 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package skillscheck
+
+import (
+	"os"
+
+	"github.com/larksuite/cli/internal/update"
+)
+
+// shouldSkip returns true when the skills check should be silently
+// suppressed. Mirrors internal/update.shouldSkip semantics but uses
+// a dedicated opt-out env var so users can disable the skills nag
+// without also disabling the binary update nag.
+func shouldSkip(version string) bool {
+	if os.Getenv("LARKSUITE_CLI_NO_SKILLS_NOTIFIER") != "" {
+		return true
+	}
+	if update.IsCIEnv() {
+		return true
+	}
+	if version == "DEV" || version == "dev" || version == "" {
+		return true
+	}
+	return !update.IsRelease(version)
+}

internal/skillscheck/skip_test.go

@@ -0,0 +1,68 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package skillscheck
+
+import (
+	"os"
+	"testing"
+)
+
+// clearSkillsSkipEnv unsets the env vars shouldSkip checks so the
+// host environment cannot pollute test results.
+func clearSkillsSkipEnv(t *testing.T) {
+	t.Helper()
+	for _, key := range []string{"LARKSUITE_CLI_NO_SKILLS_NOTIFIER", "CI", "BUILD_NUMBER", "RUN_ID"} {
+		t.Setenv(key, "")
+		os.Unsetenv(key)
+	}
+}
+
+func TestShouldSkip(t *testing.T) {
+	tests := []struct {
+		name    string
+		setup   func(t *testing.T)
+		version string
+		want    bool
+	}{
+		{"release_no_skip", clearSkillsSkipEnv, "1.0.21", false},
+		{"dev_uppercase", clearSkillsSkipEnv, "DEV", true},
+		{"dev_lowercase", clearSkillsSkipEnv, "dev", true},
+		{"empty_version", clearSkillsSkipEnv, "", true},
+		{"git_describe", clearSkillsSkipEnv, "1.0.0-12-g9b933f1-dirty", true},
+		{"opt_out", func(t *testing.T) {
+			clearSkillsSkipEnv(t)
+			t.Setenv("LARKSUITE_CLI_NO_SKILLS_NOTIFIER", "1")
+		}, "1.0.21", true},
+		{"ci_env", func(t *testing.T) {
+			clearSkillsSkipEnv(t)
+			t.Setenv("CI", "true")
+		}, "1.0.21", true},
+		{"build_number_env", func(t *testing.T) {
+			clearSkillsSkipEnv(t)
+			t.Setenv("BUILD_NUMBER", "42")
+		}, "1.0.21", true},
+		{"run_id_env", func(t *testing.T) {
+			clearSkillsSkipEnv(t)
+			t.Setenv("RUN_ID", "abc")
+		}, "1.0.21", true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			tt.setup(t)
+			if got := shouldSkip(tt.version); got != tt.want {
+				t.Errorf("shouldSkip(%q) = %v, want %v", tt.version, got, tt.want)
+			}
+		})
+	}
+}
+
+// Independent opt-out: LARKSUITE_CLI_NO_SKILLS_NOTIFIER must NOT be
+// affected by LARKSUITE_CLI_NO_UPDATE_NOTIFIER (different env vars).
+func TestShouldSkip_OptOutIsIndependent(t *testing.T) {
+	clearSkillsSkipEnv(t)
+	t.Setenv("LARKSUITE_CLI_NO_UPDATE_NOTIFIER", "1") // update opt-out, not us
+	if shouldSkip("1.0.21") {
+		t.Error("shouldSkip(release) = true with only LARKSUITE_CLI_NO_UPDATE_NOTIFIER set, want false")
+	}
+}

internal/skillscheck/state.go

@@ -0,0 +1,92 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package skillscheck
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io/fs"
+	"path/filepath"
+
+	"github.com/larksuite/cli/internal/core"
+	"github.com/larksuite/cli/internal/validate"
+	"github.com/larksuite/cli/internal/vfs"
+)
+
+const (
+	stateFile = "skills-state.json"
+)
+
+var ErrUnreadableState = errors.New("skills state is unreadable")
+
+type SkillsState struct {
+	Version              string   `json:"version"`
+	OfficialSkills       []string `json:"official_skills"`
+	UpdatedSkills        []string `json:"updated_skills"`
+	AddedOfficialSkills  []string `json:"added_official_skills"`
+	SkippedDeletedSkills []string `json:"skipped_deleted_skills"`
+	UpdatedAt            string   `json:"updated_at"`
+}
+
+func statePath() string {
+	return filepath.Join(core.GetBaseConfigDir(), stateFile)
+}
+
+func ReadState() (*SkillsState, bool, error) {
+	data, err := vfs.ReadFile(statePath())
+	if err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
+			return nil, false, nil
+		}
+		return nil, false, err
+	}
+
+	var raw map[string]interface{}
+	if err := json.Unmarshal(data, &raw); err != nil {
+		return nil, false, fmt.Errorf("%w: %v", ErrUnreadableState, err)
+	}
+
+	var state SkillsState
+	if err := json.Unmarshal(data, &state); err != nil {
+		return nil, false, fmt.Errorf("%w: %v", ErrUnreadableState, err)
+	}
+	return &state, true, nil
+}
+
+func WriteState(state SkillsState) error {
+	state.ensureNonNilSlices()
+
+	if err := vfs.MkdirAll(core.GetBaseConfigDir(), 0o700); err != nil {
+		return err
+	}
+	data, err := json.MarshalIndent(state, "", "  ")
+	if err != nil {
+		return err
+	}
+	return validate.AtomicWrite(statePath(), append(data, '\n'), 0o644)
+}
+
+func ReadSyncedVersion() (string, bool) {
+	state, ok, err := ReadState()
+	if err != nil || !ok || state.Version == "" {
+		return "", false
+	}
+	return state.Version, true
+}
+
+func (s *SkillsState) ensureNonNilSlices() {
+	if s.OfficialSkills == nil {
+		s.OfficialSkills = []string{}
+	}
+	if s.UpdatedSkills == nil {
+		s.UpdatedSkills = []string{}
+	}
+	if s.AddedOfficialSkills == nil {
+		s.AddedOfficialSkills = []string{}
+	}
+	if s.SkippedDeletedSkills == nil {
+		s.SkippedDeletedSkills = []string{}
+	}
+}

internal/skillscheck/state_test.go

@@ -0,0 +1,139 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package skillscheck
+
+import (
+	"encoding/json"
+	"errors"
+	"os"
+	"path/filepath"
+	"reflect"
+	"testing"
+)
+
+func TestReadState_Missing(t *testing.T) {
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", t.TempDir())
+
+	state, ok, err := ReadState()
+	if err != nil {
+		t.Fatalf("ReadState() err = %v, want nil for missing file", err)
+	}
+	if ok {
+		t.Fatal("ReadState() ok = true, want false for missing file")
+	}
+	if state != nil {
+		t.Fatalf("ReadState() state = %#v, want nil for missing file", state)
+	}
+}
+
+func TestReadState_Valid(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	want := SkillsState{
+		Version:              "1.2.3",
+		OfficialSkills:       []string{"lark-doc", "lark-im"},
+		UpdatedSkills:        []string{"lark-doc"},
+		AddedOfficialSkills:  []string{"lark-task"},
+		SkippedDeletedSkills: []string{"custom-skill"},
+		UpdatedAt:            "2026-05-18T10:00:00Z",
+	}
+	data, err := json.Marshal(want)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(dir, stateFile), data, 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	got, ok, err := ReadState()
+	if err != nil {
+		t.Fatalf("ReadState() err = %v, want nil", err)
+	}
+	if !ok {
+		t.Fatal("ReadState() ok = false, want true")
+	}
+	if got == nil {
+		t.Fatal("ReadState() state = nil, want state")
+	}
+	if !reflect.DeepEqual(*got, want) {
+		t.Fatalf("ReadState() state = %#v, want %#v", *got, want)
+	}
+}
+
+func TestReadState_CorruptStateUnreadable(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	if err := os.WriteFile(filepath.Join(dir, stateFile), []byte(`{"version":`), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	state, ok, err := ReadState()
+	if !errors.Is(err, ErrUnreadableState) {
+		t.Fatalf("ReadState() err = %v, want ErrUnreadableState", err)
+	}
+	if ok {
+		t.Fatal("ReadState() ok = true, want false")
+	}
+	if state != nil {
+		t.Fatalf("ReadState() state = %#v, want nil", state)
+	}
+}
+
+func TestWriteState_CreatesDirAndWritesState(t *testing.T) {
+	dir := filepath.Join(t.TempDir(), "nested")
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+
+	state := SkillsState{
+		Version:   "1.2.3",
+		UpdatedAt: "2026-05-18T10:00:00Z",
+	}
+	if err := WriteState(state); err != nil {
+		t.Fatalf("WriteState() err = %v, want nil", err)
+	}
+
+	raw, err := os.ReadFile(filepath.Join(dir, stateFile))
+	if err != nil {
+		t.Fatal(err)
+	}
+	var got SkillsState
+	if err := json.Unmarshal(raw, &got); err != nil {
+		t.Fatalf("written state is invalid JSON: %v", err)
+	}
+	if got.Version != state.Version {
+		t.Fatalf("version = %q, want %q", got.Version, state.Version)
+	}
+	if got.OfficialSkills == nil {
+		t.Fatal("official_skills decoded as nil, want empty slice")
+	}
+	if got.UpdatedSkills == nil {
+		t.Fatal("updated_skills decoded as nil, want empty slice")
+	}
+	if got.AddedOfficialSkills == nil {
+		t.Fatal("added_skills decoded as nil, want empty slice")
+	}
+	if got.SkippedDeletedSkills == nil {
+		t.Fatal("skipped_deleted_skills decoded as nil, want empty slice")
+	}
+}
+
+func TestReadSyncedVersionFromState(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+
+	if got, ok := ReadSyncedVersion(); ok || got != "" {
+		t.Fatalf("ReadSyncedVersion() = (%q, %v), want (\"\", false) for missing state", got, ok)
+	}
+	if err := WriteState(SkillsState{Version: "1.2.3"}); err != nil {
+		t.Fatal(err)
+	}
+	if got, ok := ReadSyncedVersion(); !ok || got != "1.2.3" {
+		t.Fatalf("ReadSyncedVersion() = (%q, %v), want (\"1.2.3\", true)", got, ok)
+	}
+	if err := WriteState(SkillsState{}); err != nil {
+		t.Fatal(err)
+	}
+	if got, ok := ReadSyncedVersion(); ok || got != "" {
+		t.Fatalf("ReadSyncedVersion() = (%q, %v), want (\"\", false) for empty version", got, ok)
+	}
+}

internal/skillscheck/sync.go

@@ -0,0 +1,503 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package skillscheck
+
+import (
+	"encoding/json"
+	"fmt"
+	"regexp"
+	"sort"
+	"strings"
+	"time"
+
+	"github.com/larksuite/cli/internal/selfupdate"
+)
+
+var (
+	skillNamePattern = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9_:-]*(@[^\s]+)?$`)
+	ansiPattern      = regexp.MustCompile(`\x1b\[[0-?]*[ -/]*[@-~]`)
+)
+
+type SyncInput struct {
+	Version        string
+	OfficialSkills []string
+	LocalSkills    []string
+	PreviousState  *SkillsState
+	StateReadable  bool
+	Force          bool
+}
+
+type SyncPlan struct {
+	Version        string
+	OfficialSkills []string
+	ToUpdate       []string
+	Added          []string
+	SkippedDeleted []string
+}
+
+func stripANSI(s string) string {
+	return ansiPattern.ReplaceAllString(s, "")
+}
+
+func ParseSkillsList(text string) []string {
+	text = stripANSI(text)
+	lines := strings.Split(text, "\n")
+
+	// Detect format type
+	hasGlobalSkills := strings.Contains(text, "Global Skills")
+	hasAvailableSkills := strings.Contains(text, "Available Skills")
+
+	if hasGlobalSkills {
+		// Format 1: locally installed skills list from "npx -y skills ls -g"
+		return parseGlobalSkillsList(lines)
+	} else if hasAvailableSkills {
+		// Format 2: official skills list from "npx -y skills add ... --list"
+		return parseOfficialSkillsList(lines)
+	}
+	return nil
+}
+
+func ParseGlobalSkillsJSON(text string) []string {
+	type globalSkill struct {
+		Name string `json:"name"`
+	}
+
+	var skills []globalSkill
+	if err := json.Unmarshal([]byte(text), &skills); err != nil {
+		return nil
+	}
+
+	seen := map[string]bool{}
+	for _, skill := range skills {
+		candidate := strings.TrimSpace(skill.Name)
+		if candidate == "" || !skillNamePattern.MatchString(candidate) {
+			continue
+		}
+		seen[candidate] = true
+	}
+
+	return sortedKeys(seen)
+}
+
+func ParseOfficialSkillsIndexJSON(text string) ([]string, error) {
+	type officialSkill struct {
+		Name string `json:"name"`
+	}
+	type officialIndex struct {
+		Skills []officialSkill `json:"skills"`
+	}
+
+	var index officialIndex
+	if err := json.Unmarshal([]byte(text), &index); err != nil {
+		return nil, err
+	}
+
+	seen := map[string]bool{}
+	for _, skill := range index.Skills {
+		candidate := strings.TrimSpace(skill.Name)
+		if skillNamePattern.MatchString(candidate) {
+			seen[candidate] = true
+		}
+	}
+
+	return sortedKeys(seen), nil
+}
+
+// parseGlobalSkillsList parses the output of "npx -y skills ls -g"
+func parseGlobalSkillsList(lines []string) []string {
+	seen := map[string]bool{}
+
+	for _, line := range lines {
+		trimmed := strings.TrimSpace(line)
+
+		// Skip header
+		if strings.HasPrefix(trimmed, "Global Skills") {
+			continue
+		}
+
+		// Skip empty lines
+		if trimmed == "" {
+			continue
+		}
+		if strings.HasPrefix(trimmed, "Tip:") {
+			continue
+		}
+
+		if strings.HasPrefix(trimmed, "Agents:") {
+			continue
+		}
+
+		if isGlobalSkillsSectionHeader(trimmed) {
+			continue
+		}
+
+		// Extract skill name, format is typically "skill-name /path/to/skill"
+		parts := strings.Fields(trimmed)
+		if len(parts) == 0 {
+			continue
+		}
+
+		candidate := parts[0]
+
+		// Validate and add
+		if candidate == "" || !skillNamePattern.MatchString(candidate) {
+			continue
+		}
+		seen[candidate] = true
+	}
+
+	return sortedKeys(seen)
+}
+
+func isGlobalSkillsSectionHeader(line string) bool {
+	switch line {
+	case "General", "Project", "Local":
+		return true
+	default:
+		return false
+	}
+}
+
+// parseOfficialSkillsList parses the output of "npx -y skills add ... --list"
+func parseOfficialSkillsList(lines []string) []string {
+	seen := map[string]bool{}
+	inAvailableSection := false
+
+	for _, line := range lines {
+		// Check if we've reached the "Available Skills" section
+		if strings.Contains(line, "Available Skills") {
+			inAvailableSection = true
+			continue
+		}
+
+		if !inAvailableSection {
+			continue
+		}
+
+		// Process lines containing "│", e.g. " │    lark-approval "
+		if strings.Contains(line, "│") {
+			// Remove all "│" characters and spaces, extract the first valid token in order
+			parts := strings.FieldsFunc(line, func(r rune) bool {
+				return r == '│' || r == ' '
+			})
+
+			if len(parts) > 0 {
+				candidate := parts[0]
+				if skillNamePattern.MatchString(candidate) {
+					seen[candidate] = true
+				}
+			}
+		}
+	}
+
+	return sortedKeys(seen)
+}
+
+func PlanSync(input SyncInput) SyncPlan {
+	official := uniqueSorted(input.OfficialSkills)
+	if input.Force {
+		return SyncPlan{
+			Version:        input.Version,
+			OfficialSkills: official,
+			ToUpdate:       official,
+			Added:          []string{},
+			SkippedDeleted: []string{},
+		}
+	}
+
+	officialSet := toSet(official)
+	installedOfficial := intersection(input.LocalSkills, officialSet)
+
+	previousOfficial := []string{}
+	if input.StateReadable && input.PreviousState != nil {
+		previousOfficial = input.PreviousState.OfficialSkills
+	}
+	previousSet := toSet(previousOfficial)
+
+	newAddedOfficial := []string{}
+	for _, skill := range official {
+		if !previousSet[skill] {
+			newAddedOfficial = append(newAddedOfficial, skill)
+		}
+	}
+
+	updateSet := toSet(installedOfficial)
+	for _, skill := range newAddedOfficial {
+		updateSet[skill] = true
+	}
+	toUpdate := sortedKeys(updateSet)
+	updateSet = toSet(toUpdate)
+
+	skipped := []string{}
+	for _, skill := range official {
+		if !updateSet[skill] {
+			skipped = append(skipped, skill)
+		}
+	}
+
+	return SyncPlan{
+		Version:        input.Version,
+		OfficialSkills: official,
+		ToUpdate:       toUpdate,
+		Added:          uniqueSorted(newAddedOfficial),
+		SkippedDeleted: skipped,
+	}
+}
+
+type SkillsRunner interface {
+	ListOfficialSkillsIndex() *selfupdate.NpmResult
+	ListOfficialSkills() *selfupdate.NpmResult
+	ListGlobalSkillsJSON() *selfupdate.NpmResult
+	ListGlobalSkills() *selfupdate.NpmResult
+	InstallSkill(nameList []string) *selfupdate.NpmResult
+	InstallAllSkills() *selfupdate.NpmResult
+}
+
+type SyncOptions struct {
+	Version string
+	Force   bool
+	Runner  SkillsRunner
+	Now     func() time.Time
+}
+
+type SyncResult struct {
+	Action         string
+	Official       []string
+	Updated        []string
+	Added          []string
+	SkippedDeleted []string
+	Failed         []string
+	Err            error
+	Detail         string
+	Force          bool
+}
+
+func SyncSkills(opts SyncOptions) *SyncResult {
+	if opts.Now == nil {
+		opts.Now = time.Now
+	}
+	if opts.Runner == nil {
+		return &SyncResult{Action: "failed", Err: fmt.Errorf("skills runner is nil")}
+	}
+
+	// --- Step 1: List official skills ---
+	official, reason, ok := listOfficialSkills(opts.Runner)
+	if !ok {
+		return fallbackFullInstall(opts, reason, nil)
+	}
+
+	// --- Step 2: List local (installed) skills ---
+	local, ok := listLocalSkills(opts.Runner)
+	if !ok {
+		return fallbackFullInstall(opts, "local skills list failed or parsed as empty", official)
+	}
+
+	// --- Step 3: Read previous state ---
+	previous, readable, err := ReadState()
+	if err != nil {
+		readable = false
+		previous = nil
+	}
+
+	plan := PlanSync(SyncInput{
+		Version:        opts.Version,
+		OfficialSkills: official,
+		LocalSkills:    local,
+		PreviousState:  previous,
+		StateReadable:  readable,
+		Force:          opts.Force,
+	})
+
+	result := &SyncResult{
+		Action:         "synced",
+		Official:       plan.OfficialSkills,
+		Updated:        plan.ToUpdate,
+		Added:          plan.Added,
+		SkippedDeleted: plan.SkippedDeleted,
+		Force:          opts.Force,
+	}
+
+	if len(plan.ToUpdate) == 0 {
+		return fallbackFullInstall(opts, "toUpdate skills empty fallback", official)
+	}
+
+	if len(plan.ToUpdate) > 0 {
+		installResult := opts.Runner.InstallSkill(plan.ToUpdate)
+		if installResult == nil || installResult.Err != nil {
+			return fallbackFullInstall(opts, resultDetail(installResult), official)
+		}
+	}
+
+	state := SkillsState{
+		Version:              opts.Version,
+		OfficialSkills:       plan.OfficialSkills,
+		UpdatedSkills:        plan.ToUpdate,
+		AddedOfficialSkills:  plan.Added,
+		SkippedDeletedSkills: plan.SkippedDeleted,
+		UpdatedAt:            opts.Now().UTC().Format(time.RFC3339),
+	}
+	if err := WriteState(state); err != nil {
+		result.Action = "failed"
+		result.Err = fmt.Errorf("skills synced but state not written: %w", err)
+		return result
+	}
+
+	return result
+}
+
+func listOfficialSkills(runner SkillsRunner) ([]string, string, bool) {
+	reasons := []string{}
+
+	indexResult := runner.ListOfficialSkillsIndex()
+	if indexResult == nil || indexResult.Err != nil {
+		reasons = append(reasons, "official skills index failed: "+resultDetail(indexResult))
+	} else {
+		official, err := ParseOfficialSkillsIndexJSON(indexResult.Stdout.String())
+		if err != nil {
+			reasons = append(reasons, "official skills index JSON invalid: "+err.Error())
+		} else if len(official) > 0 {
+			return official, "", true
+		} else {
+			reasons = append(reasons, "official skills index contains no skills")
+		}
+	}
+
+	officialResult := runner.ListOfficialSkills()
+	if officialResult == nil || officialResult.Err != nil {
+		reasons = append(reasons, "official skills list failed: "+resultDetail(officialResult))
+		return nil, strings.Join(reasons, "; "), false
+	}
+	official := ParseSkillsList(officialResult.Stdout.String())
+	if len(official) > 0 {
+		return official, "", true
+	}
+	if strings.TrimSpace(officialResult.Stdout.String()) != "" {
+		reasons = append(reasons, "official skills list parsed as empty despite non-empty stdout")
+	} else {
+		reasons = append(reasons, "official skills list returned no skills")
+	}
+	return nil, strings.Join(reasons, "; "), false
+}
+
+func listLocalSkills(runner SkillsRunner) ([]string, bool) {
+	jsonResult := runner.ListGlobalSkillsJSON()
+	if jsonResult != nil && jsonResult.Err == nil {
+		if local := ParseGlobalSkillsJSON(jsonResult.Stdout.String()); len(local) > 0 {
+			return local, true
+		}
+	}
+
+	textResult := runner.ListGlobalSkills()
+	if textResult != nil && textResult.Err == nil {
+		if local := ParseSkillsList(textResult.Stdout.String()); len(local) > 0 {
+			return local, true
+		}
+	}
+
+	return nil, false
+}
+
+// fallbackFullInstall performs a full skills install (npx -y skills add <source> -g -y)
+// when incremental sync is not possible. On success it writes a state file so that
+// subsequent syncs can use incremental mode. When official is non-nil the state
+// records the full official list; otherwise a minimal state (version only) is
+// written to break the fallback loop.
+func fallbackFullInstall(opts SyncOptions, reason string, official []string) *SyncResult {
+	installResult := opts.Runner.InstallAllSkills()
+	if installResult == nil {
+		return &SyncResult{
+			Action: "fallback_failed",
+			Err:    fmt.Errorf("full skills install failed: empty result (reason: %s)", reason),
+			Detail: reason,
+			Force:  opts.Force,
+		}
+	}
+	if installResult.Err != nil {
+		return &SyncResult{
+			Action: "fallback_failed",
+			Err:    fmt.Errorf("full skills install failed: %w (reason: %s)", installResult.Err, reason),
+			Detail: reason + "\n" + resultDetail(installResult),
+			Force:  opts.Force,
+		}
+	}
+
+	state := SkillsState{
+		Version:              opts.Version,
+		OfficialSkills:       official,
+		UpdatedSkills:        official,
+		AddedOfficialSkills:  official,
+		SkippedDeletedSkills: []string{},
+		UpdatedAt:            opts.Now().UTC().Format(time.RFC3339),
+	}
+	if writeErr := WriteState(state); writeErr != nil {
+		return &SyncResult{
+			Action:         "fallback_synced",
+			Official:       official,
+			Updated:        official,
+			Added:          official,
+			SkippedDeleted: []string{},
+			Detail:         reason + "\nstate write failed: " + writeErr.Error(),
+			Force:          opts.Force,
+		}
+	}
+
+	return &SyncResult{
+		Action:         "fallback_synced",
+		Official:       official,
+		Updated:        official,
+		Added:          official,
+		SkippedDeleted: []string{},
+		Detail:         reason,
+		Force:          opts.Force,
+	}
+}
+
+func resultDetail(result *selfupdate.NpmResult) string {
+	if result == nil {
+		return ""
+	}
+	parts := []string{}
+	if output := strings.TrimSpace(result.CombinedOutput()); output != "" {
+		parts = append(parts, output)
+	}
+	if result.Err != nil {
+		parts = append(parts, result.Err.Error())
+	}
+	return strings.Join(parts, "\n")
+}
+
+func uniqueSorted(values []string) []string {
+	return sortedKeys(toSet(values))
+}
+
+func toSet(values []string) map[string]bool {
+	out := map[string]bool{}
+	for _, value := range values {
+		value = strings.TrimSpace(value)
+		if value != "" {
+			out[value] = true
+		}
+	}
+	return out
+}
+
+// result = { x | x ∈ values ∧ x ∈ allowed }
+func intersection(values []string, allowed map[string]bool) []string {
+	out := map[string]bool{}
+	for _, value := range values {
+		if allowed[value] {
+			out[value] = true
+		}
+	}
+	return sortedKeys(out)
+}
+
+func sortedKeys(values map[string]bool) []string {
+	out := make([]string, 0, len(values))
+	for value := range values {
+		out = append(out, value)
+	}
+	sort.Strings(out)
+	return out
+}

internal/skillscheck/sync_test.go

@@ -0,0 +1,855 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package skillscheck
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/larksuite/cli/internal/selfupdate"
+)
+
+func TestParseSkillsListIgnoresUnsupportedFormat(t *testing.T) {
+	input := `Installed skills:
+- lark-calendar
+- lark-mail
+lark-im
+custom-skill
+lark-base@1.0.0
+lark-cli-harness:dev@0.1.0
+`
+	got := ParseSkillsList(input)
+	if len(got) != 0 {
+		t.Fatalf("ParseSkillsList() = %#v, want empty result for unsupported format", got)
+	}
+}
+
+func TestParseOfficialSkillsListAcceptsNonLarkOfficialNames(t *testing.T) {
+	input := `Available Skills
+│    lark-calendar
+│    official-shared
+│    bad/name
+`
+	got := ParseSkillsList(input)
+	want := []string{"lark-calendar", "official-shared"}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("ParseSkillsList() (Available Skills) = %#v, want %#v", got, want)
+	}
+}
+
+func TestParseGlobalSkillsList(t *testing.T) {
+	input := `Global Skills
+
+lark-approval ~/.agents/skills/lark-approval
+  Agents: TRAE CN, TRAE, TRAE-SOLO, TRAE CLI, TRAE CLI (Coco) +3 more
+lark-attendance ~/.agents/skills/lark-attendance
+  Agents: TRAE CN, TRAE, TRAE-SOLO, TRAE CLI, TRAE CLI (Coco) +3 more
+lark-base ~/.agents/skills/lark-base
+  Agents: TRAE CN, TRAE, TRAE-SOLO, TRAE CLI, TRAE CLI (Coco) +3 more
+lark-calendar ~/.agents/skills/lark-calendar
+  Agents: TRAE CN, TRAE, TRAE-SOLO, TRAE CLI, TRAE CLI (Coco) +3 more
+dogfood ~/.hermes/skills/dogfood
+  Agents: Hermes Agent
+yuanbao ~/.hermes/skills/yuanbao
+  Agents: Hermes Agent
+`
+	got := ParseSkillsList(input)
+	want := []string{"dogfood", "lark-approval", "lark-attendance", "lark-base", "lark-calendar", "yuanbao"}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("ParseSkillsList() (Global Skills) = %#v, want %#v", got, want)
+	}
+}
+
+func TestParseGlobalSkillsListWithANSI(t *testing.T) {
+	input := "\x1b[1mGlobal Skills\x1b[0m\n\n" +
+		"\x1b[36mlark-calendar\x1b[0m \x1b[38;5;102m~/.agents/skills/lark-calendar\x1b[0m\n" +
+		"  \x1b[38;5;102mAgents:\x1b[0m TRAE CN, TRAE +3 more\n" +
+		"\x1b[36mdogfood\x1b[0m \x1b[38;5;102m~/.hermes/skills/dogfood\x1b[0m\n" +
+		"  \x1b[38;5;102mAgents:\x1b[0m Hermes Agent\n" +
+		"\nTip: Use the -y flag to run in non-interactive mode (for CI and AI agents).\n"
+	got := ParseSkillsList(input)
+	want := []string{"dogfood", "lark-calendar"}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("ParseSkillsList() (ANSI Global Skills) = %#v, want %#v", got, want)
+	}
+}
+
+func TestParseGlobalSkillsListWithIndentedGroupedRows(t *testing.T) {
+	input := `Global Skills
+
+General
+  lark-apps ~/.agents/skills/lark-apps
+  lark-base ~/.agents/skills/lark-base
+`
+	got := ParseSkillsList(input)
+	want := []string{"lark-apps", "lark-base"}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("ParseSkillsList() (indented Global Skills) = %#v, want %#v", got, want)
+	}
+}
+
+func TestParseGlobalSkillsJSON(t *testing.T) {
+	input := `[
+  {"name":"lark-calendar","path":"/Users/example/.agents/skills/lark-calendar","scope":"global","agents":["Codex"]},
+  {"name":"lark-mail@1.2.3","path":"/Users/example/.agents/skills/lark-mail","scope":"global","agents":["Codex"]},
+  {"name":"lark-calendar","path":"/Users/example/.agents/skills/lark-calendar","scope":"global","agents":["Codex"]},
+  {"name":"  lark-base  ","path":"/Users/example/.agents/skills/lark-base","scope":"global","agents":["Codex"]},
+  {"name":""},
+  {"name":"   "},
+  {"name":"bad skill"}
+]`
+	got := ParseGlobalSkillsJSON(input)
+	want := []string{"lark-base", "lark-calendar", "lark-mail@1.2.3"}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("ParseGlobalSkillsJSON() = %#v, want %#v", got, want)
+	}
+}
+
+func TestParseGlobalSkillsJSONInvalidOrUnsupported(t *testing.T) {
+	for _, input := range []string{
+		`not json`,
+		`{"name":"lark-calendar"}`,
+		`[]`,
+	} {
+		if got := ParseGlobalSkillsJSON(input); len(got) != 0 {
+			t.Fatalf("ParseGlobalSkillsJSON(%q) = %#v, want empty", input, got)
+		}
+	}
+}
+
+func TestParseOfficialSkillsIndexJSON(t *testing.T) {
+	input := `{
+  "skills": [
+    {"name":"lark-calendar","description":"Calendar","files":["SKILL.md"]},
+    {"name":"lark-mail","description":"Mail","files":["SKILL.md","references/lark-mail-search.md"]},
+    {"name":"  lark-base  ","description":"Base","files":[]},
+    {"name":"lark-calendar","description":"duplicate","files":["SKILL.md"]},
+    {"name":"custom-skill","description":"not official","files":["SKILL.md"]},
+    {"name":"bad skill","description":"invalid","files":["SKILL.md"]},
+    {"name":"","description":"empty","files":["SKILL.md"]}
+  ]
+}`
+	got, err := ParseOfficialSkillsIndexJSON(input)
+	if err != nil {
+		t.Fatalf("ParseOfficialSkillsIndexJSON() err = %v, want nil", err)
+	}
+	want := []string{"custom-skill", "lark-base", "lark-calendar", "lark-mail"}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("ParseOfficialSkillsIndexJSON() = %#v, want %#v", got, want)
+	}
+}
+
+func TestParseOfficialSkillsIndexJSONInvalidOrUnsupported(t *testing.T) {
+	for _, input := range []string{
+		`not json`,
+		`[{"name":"lark-calendar"}]`,
+		`{"name":"lark-calendar"}`,
+		`{"skills":[]}`,
+		`{"skills":[{"name":"bad skill"}]}`,
+	} {
+		got, err := ParseOfficialSkillsIndexJSON(input)
+		if err == nil && len(got) != 0 {
+			t.Fatalf("ParseOfficialSkillsIndexJSON(%q) = %#v, want empty", input, got)
+		}
+	}
+}
+
+func TestPlanNormal_WithReadableStatePreservesDeletedAndAddsNew(t *testing.T) {
+	previous := &SkillsState{OfficialSkills: []string{"lark-calendar", "lark-mail"}}
+	got := PlanSync(SyncInput{
+		Version:        "1.0.33",
+		OfficialSkills: []string{"lark-calendar", "lark-mail", "lark-new"},
+		LocalSkills:    []string{"lark-calendar", "lark-custom"},
+		PreviousState:  previous,
+		StateReadable:  true,
+		Force:          false,
+	})
+
+	assertStrings(t, got.ToUpdate, []string{"lark-calendar", "lark-new"})
+	assertStrings(t, got.Added, []string{"lark-new"})
+	assertStrings(t, got.SkippedDeleted, []string{"lark-mail"})
+}
+
+func TestPlanNormal_MissingStateInstallsAllOfficial(t *testing.T) {
+	got := PlanSync(SyncInput{
+		Version:        "1.0.33",
+		OfficialSkills: []string{"lark-calendar", "lark-mail", "lark-new"},
+		LocalSkills:    []string{"lark-calendar"},
+		StateReadable:  false,
+		Force:          false,
+	})
+
+	assertStrings(t, got.ToUpdate, []string{"lark-calendar", "lark-mail", "lark-new"})
+	assertStrings(t, got.Added, []string{"lark-calendar", "lark-mail", "lark-new"})
+	assertStrings(t, got.SkippedDeleted, []string{})
+}
+
+func TestPlanForceRestoresAllOfficial(t *testing.T) {
+	got := PlanSync(SyncInput{
+		Version:        "1.0.33",
+		OfficialSkills: []string{"lark-calendar", "lark-mail", "lark-new"},
+		LocalSkills:    []string{"lark-calendar"},
+		PreviousState:  &SkillsState{OfficialSkills: []string{"lark-calendar", "lark-mail"}},
+		StateReadable:  true,
+		Force:          true,
+	})
+
+	assertStrings(t, got.ToUpdate, []string{"lark-calendar", "lark-mail", "lark-new"})
+	assertStrings(t, got.Added, []string{})
+	assertStrings(t, got.SkippedDeleted, []string{})
+}
+
+type fakeSkillsRunner struct {
+	officialIndexOut string
+	officialOut      string
+	globalJSONOut    string
+	globalOut        string
+	officialIndexErr error
+	officialErr      error
+	globalJSONErr    error
+	globalErr        error
+	installErr       error
+	installAllErr    error
+	installed        [][]string
+	installedAll     int
+	listedIndex      int
+	listedOfficial   int
+	listedGlobalJSON int
+	listedGlobalText int
+}
+
+func officialSkillsOutput(names ...string) string {
+	var b strings.Builder
+	b.WriteString("Available Skills\n")
+	for _, name := range names {
+		b.WriteString("│    ")
+		b.WriteString(name)
+		b.WriteString("\n")
+	}
+	return b.String()
+}
+
+func officialSkillsIndexOutput(names ...string) string {
+	var b strings.Builder
+	b.WriteString(`{"skills":[`)
+	for i, name := range names {
+		if i > 0 {
+			b.WriteString(",")
+		}
+		fmt.Fprintf(&b, `{"name":%q,"description":"test skill","files":["SKILL.md"]}`, name)
+	}
+	b.WriteString(`]}`)
+	return b.String()
+}
+
+func globalSkillsOutput(names ...string) string {
+	var b strings.Builder
+	b.WriteString("Global Skills\n\n")
+	for _, name := range names {
+		b.WriteString(name)
+		b.WriteString(" ~/.agents/skills/")
+		b.WriteString(name)
+		b.WriteString("\n  Agents: Claude Code\n")
+	}
+	return b.String()
+}
+
+func globalSkillsJSONOutput(names ...string) string {
+	var b strings.Builder
+	b.WriteString("[")
+	for i, name := range names {
+		if i > 0 {
+			b.WriteString(",")
+		}
+		fmt.Fprintf(&b, `{"name":%q,"path":"/Users/example/.agents/skills/%s","scope":"global","agents":["Codex"]}`, name, name)
+	}
+	b.WriteString("]")
+	return b.String()
+}
+
+func (f *fakeSkillsRunner) ListOfficialSkillsIndex() *selfupdate.NpmResult {
+	f.listedIndex++
+	r := &selfupdate.NpmResult{}
+	r.Stdout.WriteString(f.officialIndexOut)
+	r.Err = f.officialIndexErr
+	return r
+}
+
+func (f *fakeSkillsRunner) ListOfficialSkills() *selfupdate.NpmResult {
+	f.listedOfficial++
+	r := &selfupdate.NpmResult{}
+	r.Stdout.WriteString(f.officialOut)
+	r.Err = f.officialErr
+	return r
+}
+
+func (f *fakeSkillsRunner) ListGlobalSkillsJSON() *selfupdate.NpmResult {
+	f.listedGlobalJSON++
+	r := &selfupdate.NpmResult{}
+	r.Stdout.WriteString(f.globalJSONOut)
+	r.Err = f.globalJSONErr
+	return r
+}
+
+func (f *fakeSkillsRunner) ListGlobalSkills() *selfupdate.NpmResult {
+	f.listedGlobalText++
+	r := &selfupdate.NpmResult{}
+	r.Stdout.WriteString(f.globalOut)
+	r.Err = f.globalErr
+	return r
+}
+
+func (f *fakeSkillsRunner) InstallSkill(nameList []string) *selfupdate.NpmResult {
+	f.installed = append(f.installed, nameList)
+	r := &selfupdate.NpmResult{}
+	r.Err = f.installErr
+	return r
+}
+
+func (f *fakeSkillsRunner) InstallAllSkills() *selfupdate.NpmResult {
+	f.installedAll++
+	r := &selfupdate.NpmResult{}
+	r.Err = f.installAllErr
+	return r
+}
+
+func TestSyncSkills_WritesStateAndDoesNotWriteStamp(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	if err := WriteState(SkillsState{
+		Version:        "1.0.30",
+		OfficialSkills: []string{"lark-calendar", "lark-mail"},
+		UpdatedAt:      "2026-05-18T00:00:00Z",
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	runner := &fakeSkillsRunner{
+		officialIndexOut: officialSkillsIndexOutput("lark-calendar", "lark-mail", "lark-new"),
+		officialOut:      officialSkillsOutput("lark-calendar", "lark-mail", "lark-new"),
+		globalJSONOut:    globalSkillsJSONOutput("lark-calendar", "lark-custom"),
+		globalOut:        globalSkillsOutput("lark-mail"),
+	}
+	result := SyncSkills(SyncOptions{
+		Version: "1.0.33",
+		Runner:  runner,
+		Now:     func() time.Time { return time.Date(2026, 5, 18, 12, 0, 0, 0, time.UTC) },
+	})
+
+	if result.Err != nil {
+		t.Fatalf("SyncSkills() err = %v, want nil", result.Err)
+	}
+	assertStrings(t, runner.installed[0], []string{"lark-calendar", "lark-new"})
+	if runner.listedGlobalJSON != 1 {
+		t.Fatalf("listedGlobalJSON = %d, want 1", runner.listedGlobalJSON)
+	}
+	if runner.listedGlobalText != 0 {
+		t.Fatalf("listedGlobalText = %d, want 0 when JSON list succeeds", runner.listedGlobalText)
+	}
+
+	state, readable, err := ReadState()
+	if err != nil || !readable {
+		t.Fatalf("ReadState() = (_, %v, %v), want readable", readable, err)
+	}
+	assertStrings(t, state.OfficialSkills, []string{"lark-calendar", "lark-mail", "lark-new"})
+	assertStrings(t, state.UpdatedSkills, []string{"lark-calendar", "lark-new"})
+	assertStrings(t, state.AddedOfficialSkills, []string{"lark-new"})
+	assertStrings(t, state.SkippedDeletedSkills, []string{"lark-mail"})
+	if _, err := os.Stat(filepath.Join(dir, "skills.stamp")); !os.IsNotExist(err) {
+		t.Fatalf("skills.stamp exists or stat failed with unexpected err: %v", err)
+	}
+}
+
+func TestSyncSkills_OfficialIndexSuccessSkipsOfficialListCommand(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	runner := &fakeSkillsRunner{
+		officialIndexOut: officialSkillsIndexOutput("lark-calendar", "lark-mail", "lark-new"),
+		officialOut:      officialSkillsOutput("lark-should-not-be-used"),
+		globalJSONOut:    globalSkillsJSONOutput("lark-calendar"),
+		globalOut:        globalSkillsOutput("lark-mail"),
+	}
+
+	result := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner, Now: time.Now})
+	if result.Err != nil {
+		t.Fatalf("SyncSkills() err = %v, want nil", result.Err)
+	}
+	assertStrings(t, result.Official, []string{"lark-calendar", "lark-mail", "lark-new"})
+	assertStrings(t, runner.installed[0], []string{"lark-calendar", "lark-mail", "lark-new"})
+	if runner.listedIndex != 1 {
+		t.Fatalf("listedIndex = %d, want 1", runner.listedIndex)
+	}
+	if runner.listedOfficial != 0 {
+		t.Fatalf("listedOfficial = %d, want 0 when index succeeds", runner.listedOfficial)
+	}
+}
+
+func TestSyncSkills_OfficialIndexFailureFallsBackToOfficialList(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	runner := &fakeSkillsRunner{
+		officialIndexErr: fmt.Errorf("index unavailable"),
+		officialOut:      officialSkillsOutput("lark-calendar", "lark-mail"),
+		globalJSONOut:    globalSkillsJSONOutput("lark-calendar"),
+	}
+
+	result := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner, Now: time.Now})
+	if result.Err != nil {
+		t.Fatalf("SyncSkills() err = %v, want nil", result.Err)
+	}
+	assertStrings(t, result.Official, []string{"lark-calendar", "lark-mail"})
+	if runner.listedIndex != 1 || runner.listedOfficial != 1 {
+		t.Fatalf("listed index/official = %d/%d, want 1/1", runner.listedIndex, runner.listedOfficial)
+	}
+	if runner.installedAll != 0 {
+		t.Fatalf("installedAll = %d, want 0", runner.installedAll)
+	}
+}
+
+func TestSyncSkills_OfficialIndexEmptyFallsBackToOfficialList(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	runner := &fakeSkillsRunner{
+		officialIndexOut: `{"skills":[]}`,
+		officialOut:      officialSkillsOutput("lark-calendar", "lark-mail"),
+		globalJSONOut:    globalSkillsJSONOutput("lark-calendar"),
+	}
+
+	result := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner, Now: time.Now})
+	if result.Err != nil {
+		t.Fatalf("SyncSkills() err = %v, want nil", result.Err)
+	}
+	assertStrings(t, result.Official, []string{"lark-calendar", "lark-mail"})
+	if runner.listedIndex != 1 || runner.listedOfficial != 1 {
+		t.Fatalf("listed index/official = %d/%d, want 1/1", runner.listedIndex, runner.listedOfficial)
+	}
+}
+
+func TestSyncSkills_OfficialDiscoveryFailuresFallBackToFullInstallWithReasons(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	runner := &fakeSkillsRunner{
+		officialIndexErr: fmt.Errorf("index unavailable"),
+		officialErr:      fmt.Errorf("list failed"),
+		installAllErr:    nil,
+	}
+
+	result := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner, Now: time.Now})
+	if result.Action != "fallback_synced" {
+		t.Fatalf("SyncSkills() action = %q, want fallback_synced", result.Action)
+	}
+	if runner.installedAll != 1 {
+		t.Fatalf("installedAll = %d, want 1", runner.installedAll)
+	}
+	if !strings.Contains(result.Detail, "official skills index failed") || !strings.Contains(result.Detail, "official skills list failed") {
+		t.Fatalf("SyncSkills() detail = %q, want both discovery failure reasons", result.Detail)
+	}
+}
+
+func TestSyncSkills_OfficialDiscoveryEmptyFallsBackToFullInstallWithReasons(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	runner := &fakeSkillsRunner{
+		officialIndexOut: `{"skills":[]}`,
+		installAllErr:    nil,
+	}
+
+	result := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner, Now: time.Now})
+	if result.Action != "fallback_synced" {
+		t.Fatalf("SyncSkills() action = %q, want fallback_synced", result.Action)
+	}
+	if runner.installedAll != 1 {
+		t.Fatalf("installedAll = %d, want 1", runner.installedAll)
+	}
+	if !strings.Contains(result.Detail, "official skills index contains no skills") || !strings.Contains(result.Detail, "official skills list returned no skills") {
+		t.Fatalf("SyncSkills() detail = %q, want both empty discovery reasons", result.Detail)
+	}
+}
+
+func TestSyncSkills_ListOfficialFailureFallsBackToFullInstall(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	runner := &fakeSkillsRunner{
+		officialIndexErr: fmt.Errorf("index unavailable"),
+		officialErr:      fmt.Errorf("list failed"),
+		installAllErr:    nil,
+	}
+
+	result := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner, Now: time.Now})
+	if result.Action != "fallback_synced" {
+		t.Fatalf("SyncSkills() action = %q, want fallback_synced", result.Action)
+	}
+	if runner.installedAll != 1 {
+		t.Fatalf("installedAll = %d, want 1", runner.installedAll)
+	}
+	if len(runner.installed) != 0 {
+		t.Fatalf("installed = %#v, want no incremental installs", runner.installed)
+	}
+
+	state, readable, err := ReadState()
+	if err != nil || !readable {
+		t.Fatalf("ReadState() = (_, %v, %v), want readable", readable, err)
+	}
+	if state.Version != "1.0.33" {
+		t.Fatalf("state.Version = %q, want %q", state.Version, "1.0.33")
+	}
+	assertStrings(t, state.OfficialSkills, []string{})
+}
+
+func TestSyncSkills_ListOfficialFailureAndFullInstallFails(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	runner := &fakeSkillsRunner{
+		officialIndexErr: fmt.Errorf("index unavailable"),
+		officialErr:      fmt.Errorf("list failed"),
+		installAllErr:    fmt.Errorf("full install failed"),
+	}
+
+	result := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner, Now: time.Now})
+	if result.Action != "fallback_failed" {
+		t.Fatalf("SyncSkills() action = %q, want fallback_failed", result.Action)
+	}
+	if result.Err == nil {
+		t.Fatalf("SyncSkills() err = nil, want error")
+	}
+	if !strings.Contains(result.Err.Error(), "full skills install failed") {
+		t.Fatalf("SyncSkills() err = %v, want full install failure", result.Err)
+	}
+}
+
+func TestSyncSkills_GlobalJSONFailureFallsBackToTextList(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	runner := &fakeSkillsRunner{
+		officialIndexOut: officialSkillsIndexOutput("lark-calendar", "lark-mail"),
+		officialOut:      officialSkillsOutput("lark-calendar", "lark-mail"),
+		globalJSONErr:    fmt.Errorf("json list failed"),
+		globalOut:        globalSkillsOutput("lark-calendar"),
+	}
+
+	result := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner, Now: time.Now})
+	if result.Err != nil {
+		t.Fatalf("SyncSkills() err = %v, want nil", result.Err)
+	}
+	if result.Action != "synced" {
+		t.Fatalf("SyncSkills() action = %q, want synced", result.Action)
+	}
+	assertStrings(t, result.Updated, []string{"lark-calendar", "lark-mail"})
+	if runner.listedGlobalJSON != 1 || runner.listedGlobalText != 1 {
+		t.Fatalf("listed JSON/text = %d/%d, want 1/1", runner.listedGlobalJSON, runner.listedGlobalText)
+	}
+	if runner.installedAll != 0 {
+		t.Fatalf("installedAll = %d, want 0", runner.installedAll)
+	}
+}
+
+func TestSyncSkills_LocalListsFailureFallsBackToFullInstall(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	runner := &fakeSkillsRunner{
+		officialIndexOut: officialSkillsIndexOutput("lark-calendar", "lark-mail"),
+		officialOut:      officialSkillsOutput("lark-calendar", "lark-mail"),
+		globalJSONErr:    fmt.Errorf("json list failed with /Users/example/.agents/skills/lark-calendar agents Codex"),
+		globalErr:        fmt.Errorf("text list failed with /Users/example/.agents/skills/lark-mail agents Codex"),
+	}
+
+	result := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner, Now: time.Now})
+	if result.Action != "fallback_synced" {
+		t.Fatalf("SyncSkills() action = %q, want fallback_synced", result.Action)
+	}
+	if len(runner.installed) != 0 {
+		t.Fatalf("installed = %#v, want no incremental installs", runner.installed)
+	}
+	if runner.installedAll != 1 {
+		t.Fatalf("installedAll = %d, want 1", runner.installedAll)
+	}
+	if strings.Contains(result.Detail, "/Users/example") || strings.Contains(result.Detail, "agents") {
+		t.Fatalf("SyncSkills() detail leaks local command output: %q", result.Detail)
+	}
+}
+
+func TestSyncSkills_ParseEmptyLocalListsFallBackToFullInstall(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	runner := &fakeSkillsRunner{
+		officialIndexOut: officialSkillsIndexOutput("lark-calendar", "lark-mail"),
+		officialOut:      officialSkillsOutput("lark-calendar", "lark-mail"),
+		globalJSONOut:    `[]`,
+		globalOut:        "Some unrecognized output format\n",
+	}
+
+	result := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner, Now: time.Now})
+	if result.Action != "fallback_synced" {
+		t.Fatalf("SyncSkills() action = %q, want fallback_synced", result.Action)
+	}
+	if len(runner.installed) != 0 {
+		t.Fatalf("installed = %#v, want no incremental installs", runner.installed)
+	}
+	if runner.installedAll != 1 {
+		t.Fatalf("installedAll = %d, want 1", runner.installedAll)
+	}
+}
+
+func TestSyncSkills_EmptyToUpdateFallsBackToFullInstall(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	if err := WriteState(SkillsState{
+		Version:        "1.0.30",
+		OfficialSkills: []string{"lark-calendar", "lark-mail"},
+		UpdatedAt:      "2026-05-18T00:00:00Z",
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	runner := &fakeSkillsRunner{
+		officialIndexOut: officialSkillsIndexOutput("lark-calendar", "lark-mail"),
+		officialOut:      officialSkillsOutput("lark-calendar", "lark-mail"),
+		globalOut:        globalSkillsOutput(),
+		installAllErr:    nil,
+	}
+
+	result := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner, Now: time.Now})
+	if result.Action != "fallback_synced" {
+		t.Fatalf("SyncSkills() action = %q, want fallback_synced", result.Action)
+	}
+	if len(runner.installed) != 0 {
+		t.Fatalf("installed = %#v, want no incremental installs", runner.installed)
+	}
+	if runner.installedAll != 1 {
+		t.Fatalf("installedAll = %d, want 1 (fallback triggered)", runner.installedAll)
+	}
+	assertStrings(t, result.Official, []string{"lark-calendar", "lark-mail"})
+	assertStrings(t, result.Updated, []string{"lark-calendar", "lark-mail"})
+	assertStrings(t, result.Added, []string{"lark-calendar", "lark-mail"})
+	assertStrings(t, result.SkippedDeleted, []string{})
+}
+
+func TestSyncSkills_InstallFailureFallsBackToFullInstall(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	runner := &fakeSkillsRunner{
+		officialIndexOut: officialSkillsIndexOutput("lark-calendar", "lark-mail"),
+		officialOut:      officialSkillsOutput("lark-calendar", "lark-mail"),
+		globalJSONOut:    globalSkillsJSONOutput("lark-calendar", "lark-mail"),
+		globalOut:        globalSkillsOutput("lark-calendar", "lark-mail"),
+		installErr:       fmt.Errorf("incremental boom"),
+		installAllErr:    nil,
+	}
+
+	result := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner, Now: time.Now})
+	if result.Action != "fallback_synced" {
+		t.Fatalf("SyncSkills() action = %q, want fallback_synced", result.Action)
+	}
+	if len(runner.installed) != 1 {
+		t.Fatalf("installed = %d calls, want 1", len(runner.installed))
+	}
+	if runner.installedAll != 1 {
+		t.Fatalf("installedAll = %d, want 1 (fallback triggered)", runner.installedAll)
+	}
+
+	state, readable, err := ReadState()
+	if err != nil || !readable {
+		t.Fatalf("ReadState() = (_, %v, %v), want readable", readable, err)
+	}
+	if state.Version != "1.0.33" {
+		t.Fatalf("state.Version = %q, want %q", state.Version, "1.0.33")
+	}
+	assertStrings(t, state.OfficialSkills, []string{"lark-calendar", "lark-mail"})
+}
+
+func TestSyncSkills_InstallFailureAndFullInstallFails(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	runner := &fakeSkillsRunner{
+		officialIndexOut: officialSkillsIndexOutput("lark-calendar", "lark-mail"),
+		officialOut:      officialSkillsOutput("lark-calendar", "lark-mail"),
+		globalJSONOut:    globalSkillsJSONOutput("lark-calendar", "lark-mail"),
+		globalOut:        globalSkillsOutput("lark-calendar", "lark-mail"),
+		installErr:       fmt.Errorf("incremental boom"),
+		installAllErr:    fmt.Errorf("full install boom"),
+	}
+
+	result := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner, Now: time.Now})
+	if result.Action != "fallback_failed" {
+		t.Fatalf("SyncSkills() action = %q, want fallback_failed", result.Action)
+	}
+	if result.Err == nil {
+		t.Fatalf("SyncSkills() err = nil, want error")
+	}
+	if !strings.Contains(result.Detail, "incremental boom") {
+		t.Fatalf("SyncSkills() detail = %q, want incremental error text", result.Detail)
+	}
+	if !strings.Contains(result.Err.Error(), "full skills install failed") {
+		t.Fatalf("SyncSkills() err = %v, want full install failure", result.Err)
+	}
+}
+
+func TestSyncSkills_NilRunnerFails(t *testing.T) {
+	result := SyncSkills(SyncOptions{Version: "1.0.33", Now: time.Now})
+	if result.Err == nil || !strings.Contains(result.Err.Error(), "skills runner is nil") {
+		t.Fatalf("SyncSkills() err = %v, want nil runner failure", result.Err)
+	}
+}
+
+func TestSyncSkills_ParseEmptyWithNonEmptyStdoutFallsBack(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	runner := &fakeSkillsRunner{
+		officialIndexErr: fmt.Errorf("index unavailable"),
+		officialOut:      "Some unrecognized output format\n",
+		installAllErr:    nil,
+	}
+
+	result := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner, Now: time.Now})
+	if result.Action != "fallback_synced" {
+		t.Fatalf("SyncSkills() action = %q, want fallback_synced", result.Action)
+	}
+	if runner.installedAll != 1 {
+		t.Fatalf("installedAll = %d, want 1", runner.installedAll)
+	}
+}
+
+func TestSyncSkills_ParseEmptyWithNonEmptyStdoutAndFullInstallFails(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	runner := &fakeSkillsRunner{
+		officialIndexErr: fmt.Errorf("index unavailable"),
+		officialOut:      "Some unrecognized output format\n",
+		installAllErr:    fmt.Errorf("full install failed"),
+	}
+
+	result := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner, Now: time.Now})
+	if result.Action != "fallback_failed" {
+		t.Fatalf("SyncSkills() action = %q, want fallback_failed", result.Action)
+	}
+	if result.Err == nil {
+		t.Fatalf("SyncSkills() err = nil, want error")
+	}
+}
+
+func assertStrings(t *testing.T, got, want []string) {
+	t.Helper()
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("got %#v, want %#v", got, want)
+	}
+}
+
+func TestSyncSkills_FallbackWithUnknownOfficialWritesMinimalState(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	runner := &fakeSkillsRunner{
+		officialIndexErr: fmt.Errorf("index unavailable"),
+		officialOut:      "Some unrecognized output format\n",
+		installAllErr:    nil,
+	}
+
+	result := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner, Now: time.Now})
+	if result.Action != "fallback_synced" {
+		t.Fatalf("SyncSkills() action = %q, want fallback_synced", result.Action)
+	}
+
+	state, readable, err := ReadState()
+	if err != nil || !readable {
+		t.Fatalf("ReadState() = (_, %v, %v), want readable", readable, err)
+	}
+	if state.Version != "1.0.33" {
+		t.Fatalf("state.Version = %q, want %q", state.Version, "1.0.33")
+	}
+	assertStrings(t, state.OfficialSkills, []string{})
+	assertStrings(t, state.UpdatedSkills, []string{})
+	assertStrings(t, state.AddedOfficialSkills, []string{})
+}
+
+func TestSyncSkills_FallbackWithKnownOfficialWritesFullState(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	runner := &fakeSkillsRunner{
+		officialIndexOut: officialSkillsIndexOutput("lark-calendar", "lark-mail"),
+		officialOut:      officialSkillsOutput("lark-calendar", "lark-mail"),
+		globalJSONOut:    globalSkillsJSONOutput("lark-calendar", "lark-mail"),
+		globalOut:        globalSkillsOutput("lark-calendar", "lark-mail"),
+		installErr:       fmt.Errorf("incremental boom"),
+		installAllErr:    nil,
+	}
+
+	result := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner, Now: time.Now})
+	if result.Action != "fallback_synced" {
+		t.Fatalf("SyncSkills() action = %q, want fallback_synced", result.Action)
+	}
+
+	state, readable, err := ReadState()
+	if err != nil || !readable {
+		t.Fatalf("ReadState() = (_, %v, %v), want readable", readable, err)
+	}
+	assertStrings(t, state.OfficialSkills, []string{"lark-calendar", "lark-mail"})
+	assertStrings(t, state.UpdatedSkills, []string{"lark-calendar", "lark-mail"})
+	assertStrings(t, state.AddedOfficialSkills, []string{"lark-calendar", "lark-mail"})
+}
+
+func TestSyncSkills_FallbackResultContainsMetadata(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	runner := &fakeSkillsRunner{
+		officialIndexOut: officialSkillsIndexOutput("lark-calendar", "lark-mail"),
+		officialOut:      officialSkillsOutput("lark-calendar", "lark-mail"),
+		globalJSONOut:    globalSkillsJSONOutput("lark-calendar", "lark-mail"),
+		globalOut:        globalSkillsOutput("lark-calendar", "lark-mail"),
+		installErr:       fmt.Errorf("incremental boom"),
+		installAllErr:    nil,
+	}
+
+	result := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner, Now: time.Now})
+	if result.Action != "fallback_synced" {
+		t.Fatalf("SyncSkills() action = %q, want fallback_synced", result.Action)
+	}
+	assertStrings(t, result.Official, []string{"lark-calendar", "lark-mail"})
+	assertStrings(t, result.Updated, []string{"lark-calendar", "lark-mail"})
+	assertStrings(t, result.Added, []string{"lark-calendar", "lark-mail"})
+	assertStrings(t, result.SkippedDeleted, []string{})
+	if !strings.Contains(result.Detail, "incremental boom") {
+		t.Fatalf("SyncSkills() detail = %q, want incremental error text", result.Detail)
+	}
+}
+
+func TestSyncSkills_FallbackBreaksDegradationLoop(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("LARKSUITE_CLI_CONFIG_DIR", dir)
+	runner := &fakeSkillsRunner{
+		officialIndexErr: fmt.Errorf("index unavailable"),
+		officialErr:      fmt.Errorf("list failed"),
+		installAllErr:    nil,
+	}
+
+	result1 := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner, Now: time.Now})
+	if result1.Action != "fallback_synced" {
+		t.Fatalf("first sync: action = %q, want fallback_synced", result1.Action)
+	}
+
+	state, readable, err := ReadState()
+	if err != nil || !readable {
+		t.Fatalf("ReadState() after first sync = (_, %v, %v), want readable", readable, err)
+	}
+	if state.Version != "1.0.33" {
+		t.Fatalf("state.Version = %q, want %q", state.Version, "1.0.33")
+	}
+
+	runner2 := &fakeSkillsRunner{
+		officialIndexOut: officialSkillsIndexOutput("lark-calendar", "lark-mail"),
+		officialOut:      officialSkillsOutput("lark-calendar", "lark-mail"),
+		globalJSONOut:    globalSkillsJSONOutput("lark-calendar", "lark-mail"),
+		globalOut:        globalSkillsOutput("lark-calendar", "lark-mail"),
+	}
+	result2 := SyncSkills(SyncOptions{Version: "1.0.33", Runner: runner2, Now: time.Now})
+	if result2.Action != "synced" {
+		t.Fatalf("second sync: action = %q, want synced (no fallback loop)", result2.Action)
+	}
+	if runner2.installedAll != 0 {
+		t.Fatalf("second sync: installedAll = %d, want 0 (incremental, not fallback)", runner2.installedAll)
+	}
+}