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backend/internal/auth/kimi/kimi.go

@@ -0,0 +1,436 @@
+// Package kimi provides authentication and token management for Kimi (Moonshot AI) API.
+// It handles the RFC 8628 OAuth2 Device Authorization Grant flow for secure authentication.
+package kimi
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"runtime"
+	"strings"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/router-for-me/CLIProxyAPI/v7/internal/buildinfo"
+	"github.com/router-for-me/CLIProxyAPI/v7/internal/config"
+	"github.com/router-for-me/CLIProxyAPI/v7/internal/util"
+	log "github.com/sirupsen/logrus"
+	"golang.org/x/sync/singleflight"
+)
+
+const (
+	// kimiClientID is Kimi Code's OAuth client ID.
+	kimiClientID = "17e5f671-d194-4dfb-9706-5516cb48c098"
+	// kimiOAuthHost is the OAuth server endpoint.
+	kimiOAuthHost = "https://auth.kimi.com"
+	// kimiDeviceCodeURL is the endpoint for requesting device codes.
+	kimiDeviceCodeURL = kimiOAuthHost + "/api/oauth/device_authorization"
+	// kimiTokenURL is the endpoint for exchanging device codes for tokens.
+	kimiTokenURL = kimiOAuthHost + "/api/oauth/token"
+	// KimiAPIBaseURL is the base URL for Kimi API requests.
+	KimiAPIBaseURL = "https://api.kimi.com/coding"
+	// defaultPollInterval is the default interval for polling token endpoint.
+	defaultPollInterval = 5 * time.Second
+	// maxPollDuration is the maximum time to wait for user authorization.
+	maxPollDuration = 15 * time.Minute
+	// refreshThresholdSeconds is when to refresh token before expiry (5 minutes).
+	refreshThresholdSeconds = 300
+)
+
+var kimiRefreshGroup singleflight.Group
+
+// KimiAuth handles Kimi authentication flow.
+type KimiAuth struct {
+	deviceClient *DeviceFlowClient
+	cfg          *config.Config
+}
+
+// NewKimiAuth creates a new KimiAuth service instance.
+func NewKimiAuth(cfg *config.Config) *KimiAuth {
+	return &KimiAuth{
+		deviceClient: NewDeviceFlowClient(cfg),
+		cfg:          cfg,
+	}
+}
+
+// StartDeviceFlow initiates the device flow authentication.
+func (k *KimiAuth) StartDeviceFlow(ctx context.Context) (*DeviceCodeResponse, error) {
+	return k.deviceClient.RequestDeviceCode(ctx)
+}
+
+// WaitForAuthorization polls for user authorization and returns the auth bundle.
+func (k *KimiAuth) WaitForAuthorization(ctx context.Context, deviceCode *DeviceCodeResponse) (*KimiAuthBundle, error) {
+	tokenData, err := k.deviceClient.PollForToken(ctx, deviceCode)
+	if err != nil {
+		return nil, err
+	}
+
+	return &KimiAuthBundle{
+		TokenData: tokenData,
+		DeviceID:  k.deviceClient.deviceID,
+	}, nil
+}
+
+// CreateTokenStorage creates a new KimiTokenStorage from auth bundle.
+func (k *KimiAuth) CreateTokenStorage(bundle *KimiAuthBundle) *KimiTokenStorage {
+	expired := ""
+	if bundle.TokenData.ExpiresAt > 0 {
+		expired = time.Unix(bundle.TokenData.ExpiresAt, 0).UTC().Format(time.RFC3339)
+	}
+	return &KimiTokenStorage{
+		AccessToken:  bundle.TokenData.AccessToken,
+		RefreshToken: bundle.TokenData.RefreshToken,
+		TokenType:    bundle.TokenData.TokenType,
+		Scope:        bundle.TokenData.Scope,
+		DeviceID:     strings.TrimSpace(bundle.DeviceID),
+		Expired:      expired,
+		Type:         "kimi",
+	}
+}
+
+// DeviceFlowClient handles the OAuth2 device flow for Kimi.
+type DeviceFlowClient struct {
+	httpClient *http.Client
+	cfg        *config.Config
+	deviceID   string
+}
+
+// NewDeviceFlowClient creates a new device flow client.
+func NewDeviceFlowClient(cfg *config.Config) *DeviceFlowClient {
+	return NewDeviceFlowClientWithDeviceID(cfg, "")
+}
+
+// NewDeviceFlowClientWithDeviceID creates a new device flow client with the specified device ID.
+func NewDeviceFlowClientWithDeviceID(cfg *config.Config, deviceID string) *DeviceFlowClient {
+	return NewDeviceFlowClientWithDeviceIDAndProxyURL(cfg, deviceID, "")
+}
+
+// NewDeviceFlowClientWithDeviceIDAndProxyURL creates a new device flow client with a proxy override.
+// proxyURL takes precedence over cfg.ProxyURL when non-empty.
+func NewDeviceFlowClientWithDeviceIDAndProxyURL(cfg *config.Config, deviceID string, proxyURL string) *DeviceFlowClient {
+	client := &http.Client{Timeout: 30 * time.Second}
+	effectiveProxyURL := strings.TrimSpace(proxyURL)
+	var sdkCfg config.SDKConfig
+	if cfg != nil {
+		sdkCfg = cfg.SDKConfig
+		if effectiveProxyURL == "" {
+			effectiveProxyURL = strings.TrimSpace(cfg.ProxyURL)
+		}
+	}
+	sdkCfg.ProxyURL = effectiveProxyURL
+	client = util.SetProxy(&sdkCfg, client)
+
+	resolvedDeviceID := strings.TrimSpace(deviceID)
+	if resolvedDeviceID == "" {
+		resolvedDeviceID = getOrCreateDeviceID()
+	}
+	return &DeviceFlowClient{
+		httpClient: client,
+		cfg:        cfg,
+		deviceID:   resolvedDeviceID,
+	}
+}
+
+// getOrCreateDeviceID returns an in-memory device ID for the current authentication flow.
+func getOrCreateDeviceID() string {
+	return uuid.New().String()
+}
+
+// getDeviceModel returns a device model string.
+func getDeviceModel() string {
+	osName := runtime.GOOS
+	arch := runtime.GOARCH
+
+	switch osName {
+	case "darwin":
+		return fmt.Sprintf("macOS %s", arch)
+	case "windows":
+		return fmt.Sprintf("Windows %s", arch)
+	case "linux":
+		return fmt.Sprintf("Linux %s", arch)
+	default:
+		return fmt.Sprintf("%s %s", osName, arch)
+	}
+}
+
+// getHostname returns the machine hostname.
+func getHostname() string {
+	hostname, err := os.Hostname()
+	if err != nil {
+		return "unknown"
+	}
+	return hostname
+}
+
+// commonHeaders returns headers required for Kimi API requests.
+func (c *DeviceFlowClient) commonHeaders() map[string]string {
+	return map[string]string{
+		"X-Msh-Platform":     "CLIProxyAPI",
+		"X-Msh-Version":      buildinfo.Version,
+		"X-Msh-Device-Name":  getHostname(),
+		"X-Msh-Device-Model": getDeviceModel(),
+		"X-Msh-Device-Id":    c.deviceID,
+	}
+}
+
+// RequestDeviceCode initiates the device flow by requesting a device code from Kimi.
+func (c *DeviceFlowClient) RequestDeviceCode(ctx context.Context) (*DeviceCodeResponse, error) {
+	data := url.Values{}
+	data.Set("client_id", kimiClientID)
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, kimiDeviceCodeURL, strings.NewReader(data.Encode()))
+	if err != nil {
+		return nil, fmt.Errorf("kimi: failed to create device code request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	req.Header.Set("Accept", "application/json")
+	for k, v := range c.commonHeaders() {
+		req.Header.Set(k, v)
+	}
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("kimi: device code request failed: %w", err)
+	}
+	defer func() {
+		if errClose := resp.Body.Close(); errClose != nil {
+			log.Errorf("kimi device code: close body error: %v", errClose)
+		}
+	}()
+
+	bodyBytes, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("kimi: failed to read device code response: %w", err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("kimi: device code request failed with status %d: %s", resp.StatusCode, string(bodyBytes))
+	}
+
+	var deviceCode DeviceCodeResponse
+	if err = json.Unmarshal(bodyBytes, &deviceCode); err != nil {
+		return nil, fmt.Errorf("kimi: failed to parse device code response: %w", err)
+	}
+
+	return &deviceCode, nil
+}
+
+// PollForToken polls the token endpoint until the user authorizes or the device code expires.
+func (c *DeviceFlowClient) PollForToken(ctx context.Context, deviceCode *DeviceCodeResponse) (*KimiTokenData, error) {
+	if deviceCode == nil {
+		return nil, fmt.Errorf("kimi: device code is nil")
+	}
+
+	interval := time.Duration(deviceCode.Interval) * time.Second
+	if interval < defaultPollInterval {
+		interval = defaultPollInterval
+	}
+
+	deadline := time.Now().Add(maxPollDuration)
+	if deviceCode.ExpiresIn > 0 {
+		codeDeadline := time.Now().Add(time.Duration(deviceCode.ExpiresIn) * time.Second)
+		if codeDeadline.Before(deadline) {
+			deadline = codeDeadline
+		}
+	}
+
+	ticker := time.NewTicker(interval)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return nil, fmt.Errorf("kimi: context cancelled: %w", ctx.Err())
+		case <-ticker.C:
+			if time.Now().After(deadline) {
+				return nil, fmt.Errorf("kimi: device code expired")
+			}
+
+			token, pollErr, shouldContinue := c.exchangeDeviceCode(ctx, deviceCode.DeviceCode)
+			if token != nil {
+				return token, nil
+			}
+			if !shouldContinue {
+				return nil, pollErr
+			}
+			// Continue polling
+		}
+	}
+}
+
+// exchangeDeviceCode attempts to exchange the device code for an access token.
+// Returns (token, error, shouldContinue).
+func (c *DeviceFlowClient) exchangeDeviceCode(ctx context.Context, deviceCode string) (*KimiTokenData, error, bool) {
+	data := url.Values{}
+	data.Set("client_id", kimiClientID)
+	data.Set("device_code", deviceCode)
+	data.Set("grant_type", "urn:ietf:params:oauth:grant-type:device_code")
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, kimiTokenURL, strings.NewReader(data.Encode()))
+	if err != nil {
+		return nil, fmt.Errorf("kimi: failed to create token request: %w", err), false
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	req.Header.Set("Accept", "application/json")
+	for k, v := range c.commonHeaders() {
+		req.Header.Set(k, v)
+	}
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("kimi: token request failed: %w", err), false
+	}
+	defer func() {
+		if errClose := resp.Body.Close(); errClose != nil {
+			log.Errorf("kimi token exchange: close body error: %v", errClose)
+		}
+	}()
+
+	bodyBytes, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("kimi: failed to read token response: %w", err), false
+	}
+
+	// Parse response - Kimi returns 200 for both success and pending states
+	var oauthResp struct {
+		Error            string  `json:"error"`
+		ErrorDescription string  `json:"error_description"`
+		AccessToken      string  `json:"access_token"`
+		RefreshToken     string  `json:"refresh_token"`
+		TokenType        string  `json:"token_type"`
+		ExpiresIn        float64 `json:"expires_in"`
+		Scope            string  `json:"scope"`
+	}
+
+	if err = json.Unmarshal(bodyBytes, &oauthResp); err != nil {
+		return nil, fmt.Errorf("kimi: failed to parse token response: %w", err), false
+	}
+
+	if oauthResp.Error != "" {
+		switch oauthResp.Error {
+		case "authorization_pending":
+			return nil, nil, true // Continue polling
+		case "slow_down":
+			return nil, nil, true // Continue polling (with increased interval handled by caller)
+		case "expired_token":
+			return nil, fmt.Errorf("kimi: device code expired"), false
+		case "access_denied":
+			return nil, fmt.Errorf("kimi: access denied by user"), false
+		default:
+			return nil, fmt.Errorf("kimi: OAuth error: %s - %s", oauthResp.Error, oauthResp.ErrorDescription), false
+		}
+	}
+
+	if oauthResp.AccessToken == "" {
+		return nil, fmt.Errorf("kimi: empty access token in response"), false
+	}
+
+	var expiresAt int64
+	if oauthResp.ExpiresIn > 0 {
+		expiresAt = time.Now().Unix() + int64(oauthResp.ExpiresIn)
+	}
+
+	return &KimiTokenData{
+		AccessToken:  oauthResp.AccessToken,
+		RefreshToken: oauthResp.RefreshToken,
+		TokenType:    oauthResp.TokenType,
+		ExpiresAt:    expiresAt,
+		Scope:        oauthResp.Scope,
+	}, nil, false
+}
+
+// RefreshToken exchanges a refresh token for a new access token.
+func (c *DeviceFlowClient) RefreshToken(ctx context.Context, refreshToken string) (*KimiTokenData, error) {
+	if strings.TrimSpace(refreshToken) == "" {
+		return nil, fmt.Errorf("kimi: refresh token is required")
+	}
+	if ctx == nil {
+		ctx = context.Background()
+	}
+	refreshToken = strings.TrimSpace(refreshToken)
+
+	result, err, _ := kimiRefreshGroup.Do(refreshToken, func() (interface{}, error) {
+		return c.refreshTokenSingleFlight(context.WithoutCancel(ctx), refreshToken)
+	})
+	if err != nil {
+		return nil, err
+	}
+	tokenData, ok := result.(*KimiTokenData)
+	if !ok || tokenData == nil {
+		return nil, fmt.Errorf("kimi: refresh token failed: invalid single-flight result")
+	}
+	return tokenData, nil
+}
+
+func (c *DeviceFlowClient) refreshTokenSingleFlight(ctx context.Context, refreshToken string) (*KimiTokenData, error) {
+	data := url.Values{}
+	data.Set("client_id", kimiClientID)
+	data.Set("grant_type", "refresh_token")
+	data.Set("refresh_token", refreshToken)
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, kimiTokenURL, strings.NewReader(data.Encode()))
+	if err != nil {
+		return nil, fmt.Errorf("kimi: failed to create refresh request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	req.Header.Set("Accept", "application/json")
+	for k, v := range c.commonHeaders() {
+		req.Header.Set(k, v)
+	}
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("kimi: refresh request failed: %w", err)
+	}
+	defer func() {
+		if errClose := resp.Body.Close(); errClose != nil {
+			log.Errorf("kimi refresh token: close body error: %v", errClose)
+		}
+	}()
+
+	bodyBytes, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("kimi: failed to read refresh response: %w", err)
+	}
+
+	if resp.StatusCode == http.StatusUnauthorized || resp.StatusCode == http.StatusForbidden {
+		return nil, fmt.Errorf("kimi: refresh token rejected (status %d)", resp.StatusCode)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("kimi: refresh failed with status %d: %s", resp.StatusCode, string(bodyBytes))
+	}
+
+	var tokenResp struct {
+		AccessToken  string  `json:"access_token"`
+		RefreshToken string  `json:"refresh_token"`
+		TokenType    string  `json:"token_type"`
+		ExpiresIn    float64 `json:"expires_in"`
+		Scope        string  `json:"scope"`
+	}
+
+	if err = json.Unmarshal(bodyBytes, &tokenResp); err != nil {
+		return nil, fmt.Errorf("kimi: failed to parse refresh response: %w", err)
+	}
+
+	if tokenResp.AccessToken == "" {
+		return nil, fmt.Errorf("kimi: empty access token in refresh response")
+	}
+
+	var expiresAt int64
+	if tokenResp.ExpiresIn > 0 {
+		expiresAt = time.Now().Unix() + int64(tokenResp.ExpiresIn)
+	}
+
+	return &KimiTokenData{
+		AccessToken:  tokenResp.AccessToken,
+		RefreshToken: tokenResp.RefreshToken,
+		TokenType:    tokenResp.TokenType,
+		ExpiresAt:    expiresAt,
+		Scope:        tokenResp.Scope,
+	}, nil
+}

backend/internal/auth/kimi/kimi_proxy_test.go

@@ -0,0 +1,42 @@
+package kimi
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/router-for-me/CLIProxyAPI/v7/internal/config"
+)
+
+func TestNewDeviceFlowClientWithDeviceIDAndProxyURL_OverrideDirectDisablesProxy(t *testing.T) {
+	cfg := &config.Config{SDKConfig: config.SDKConfig{ProxyURL: "http://proxy.example.com:8080"}}
+	client := NewDeviceFlowClientWithDeviceIDAndProxyURL(cfg, "device-1", "direct")
+
+	transport, ok := client.httpClient.Transport.(*http.Transport)
+	if !ok || transport == nil {
+		t.Fatalf("expected http.Transport, got %T", client.httpClient.Transport)
+	}
+	if transport.Proxy != nil {
+		t.Fatal("expected direct transport to disable proxy function")
+	}
+}
+
+func TestNewDeviceFlowClientWithDeviceIDAndProxyURL_OverrideProxyTakesPrecedence(t *testing.T) {
+	cfg := &config.Config{SDKConfig: config.SDKConfig{ProxyURL: "http://global.example.com:8080"}}
+	client := NewDeviceFlowClientWithDeviceIDAndProxyURL(cfg, "device-1", "http://override.example.com:8081")
+
+	transport, ok := client.httpClient.Transport.(*http.Transport)
+	if !ok || transport == nil {
+		t.Fatalf("expected http.Transport, got %T", client.httpClient.Transport)
+	}
+	req, errReq := http.NewRequest(http.MethodGet, "https://example.com", nil)
+	if errReq != nil {
+		t.Fatalf("new request: %v", errReq)
+	}
+	proxyURL, errProxy := transport.Proxy(req)
+	if errProxy != nil {
+		t.Fatalf("proxy func: %v", errProxy)
+	}
+	if proxyURL == nil || proxyURL.String() != "http://override.example.com:8081" {
+		t.Fatalf("proxy URL = %v, want http://override.example.com:8081", proxyURL)
+	}
+}

backend/internal/auth/kimi/kimi_refresh_test.go

@@ -0,0 +1,89 @@
+package kimi
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"golang.org/x/sync/singleflight"
+)
+
+type kimiRoundTripFunc func(*http.Request) (*http.Response, error)
+
+func (f kimiRoundTripFunc) RoundTrip(req *http.Request) (*http.Response, error) {
+	return f(req)
+}
+
+func resetKimiRefreshGroupForTest() {
+	kimiRefreshGroup = singleflight.Group{}
+}
+
+func TestRefreshToken_DeduplicatesConcurrentRefreshAcrossInstances(t *testing.T) {
+	resetKimiRefreshGroupForTest()
+	t.Cleanup(resetKimiRefreshGroupForTest)
+
+	var calls int32
+	started := make(chan struct{})
+	release := make(chan struct{})
+	var once sync.Once
+
+	transport := kimiRoundTripFunc(func(req *http.Request) (*http.Response, error) {
+		atomic.AddInt32(&calls, 1)
+		once.Do(func() { close(started) })
+		<-release
+		return &http.Response{
+			StatusCode: http.StatusOK,
+			Body: io.NopCloser(strings.NewReader(`{
+				"access_token":"new-access",
+				"refresh_token":"new-refresh",
+				"token_type":"Bearer",
+				"expires_in":3600
+			}`)),
+			Header:  make(http.Header),
+			Request: req,
+		}, nil
+	})
+	clientA := &DeviceFlowClient{httpClient: &http.Client{Transport: transport}}
+	clientB := &DeviceFlowClient{httpClient: &http.Client{Transport: transport}}
+
+	results := make(chan *KimiTokenData, 2)
+	errs := make(chan error, 2)
+	runRefresh := func(client *DeviceFlowClient, launched chan<- struct{}) {
+		if launched != nil {
+			close(launched)
+		}
+		tokenData, errRefresh := client.RefreshToken(context.Background(), "shared-refresh-token")
+		results <- tokenData
+		errs <- errRefresh
+	}
+
+	go runRefresh(clientA, nil)
+	<-started
+
+	secondLaunched := make(chan struct{})
+	go runRefresh(clientB, secondLaunched)
+	<-secondLaunched
+	time.Sleep(20 * time.Millisecond)
+	if got := atomic.LoadInt32(&calls); got != 1 {
+		t.Fatalf("expected concurrent refresh to share a single upstream call, got %d", got)
+	}
+	close(release)
+
+	for i := 0; i < 2; i++ {
+		if errRefresh := <-errs; errRefresh != nil {
+			t.Fatalf("expected refresh to succeed, got %v", errRefresh)
+		}
+		tokenData := <-results
+		if tokenData == nil || tokenData.AccessToken != "new-access" || tokenData.RefreshToken != "new-refresh" {
+			t.Fatalf("unexpected token data: %#v", tokenData)
+		}
+	}
+	if got := atomic.LoadInt32(&calls); got != 1 {
+		t.Fatalf("expected both refresh callers to share a single upstream call, got %d", got)
+	}
+}

backend/internal/auth/kimi/token.go

@@ -0,0 +1,134 @@
+// Package kimi provides authentication and token management functionality
+// for Kimi (Moonshot AI) services. It handles OAuth2 device flow token storage,
+// serialization, and retrieval for maintaining authenticated sessions with the Kimi API.
+package kimi
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"time"
+
+	"github.com/router-for-me/CLIProxyAPI/v7/internal/misc"
+	log "github.com/sirupsen/logrus"
+)
+
+// KimiTokenStorage stores OAuth2 token information for Kimi API authentication.
+type KimiTokenStorage struct {
+	// AccessToken is the OAuth2 access token used for authenticating API requests.
+	AccessToken string `json:"access_token"`
+	// RefreshToken is the OAuth2 refresh token used to obtain new access tokens.
+	RefreshToken string `json:"refresh_token"`
+	// TokenType is the type of token, typically "Bearer".
+	TokenType string `json:"token_type"`
+	// Scope is the OAuth2 scope granted to the token.
+	Scope string `json:"scope,omitempty"`
+	// DeviceID is the OAuth device flow identifier used for Kimi requests.
+	DeviceID string `json:"device_id,omitempty"`
+	// Expired is the RFC3339 timestamp when the access token expires.
+	Expired string `json:"expired,omitempty"`
+	// Type indicates the authentication provider type, always "kimi" for this storage.
+	Type string `json:"type"`
+
+	// Metadata holds arbitrary key-value pairs injected via hooks.
+	// It is not exported to JSON directly to allow flattening during serialization.
+	Metadata map[string]any `json:"-"`
+}
+
+// SetMetadata allows external callers to inject metadata into the storage before saving.
+func (ts *KimiTokenStorage) SetMetadata(meta map[string]any) {
+	ts.Metadata = meta
+}
+
+// KimiTokenData holds the raw OAuth token response from Kimi.
+type KimiTokenData struct {
+	// AccessToken is the OAuth2 access token.
+	AccessToken string `json:"access_token"`
+	// RefreshToken is the OAuth2 refresh token.
+	RefreshToken string `json:"refresh_token"`
+	// TokenType is the type of token, typically "Bearer".
+	TokenType string `json:"token_type"`
+	// ExpiresAt is the Unix timestamp when the token expires.
+	ExpiresAt int64 `json:"expires_at"`
+	// Scope is the OAuth2 scope granted to the token.
+	Scope string `json:"scope"`
+}
+
+// KimiAuthBundle bundles authentication data for storage.
+type KimiAuthBundle struct {
+	// TokenData contains the OAuth token information.
+	TokenData *KimiTokenData
+	// DeviceID is the device identifier used during OAuth device flow.
+	DeviceID string
+}
+
+// DeviceCodeResponse represents Kimi's device code response.
+type DeviceCodeResponse struct {
+	// DeviceCode is the device verification code.
+	DeviceCode string `json:"device_code"`
+	// UserCode is the code the user must enter at the verification URI.
+	UserCode string `json:"user_code"`
+	// VerificationURI is the URL where the user should enter the code.
+	VerificationURI string `json:"verification_uri,omitempty"`
+	// VerificationURIComplete is the URL with the code pre-filled.
+	VerificationURIComplete string `json:"verification_uri_complete"`
+	// ExpiresIn is the number of seconds until the device code expires.
+	ExpiresIn int `json:"expires_in"`
+	// Interval is the minimum number of seconds to wait between polling requests.
+	Interval int `json:"interval"`
+}
+
+// SaveTokenToFile serializes the Kimi token storage to a JSON file.
+func (ts *KimiTokenStorage) SaveTokenToFile(authFilePath string) error {
+	misc.LogSavingCredentials(authFilePath)
+	ts.Type = "kimi"
+
+	if err := os.MkdirAll(filepath.Dir(authFilePath), 0700); err != nil {
+		return fmt.Errorf("failed to create directory: %v", err)
+	}
+
+	// Merge metadata using helper
+	data, errMerge := misc.MergeMetadata(ts, ts.Metadata)
+	if errMerge != nil {
+		return fmt.Errorf("failed to merge metadata: %w", errMerge)
+	}
+
+	f, err := os.Create(authFilePath)
+	if err != nil {
+		return fmt.Errorf("failed to create token file: %w", err)
+	}
+	defer func() {
+		if errClose := f.Close(); errClose != nil {
+			log.Errorf("kimi token storage: close token file error: %v", errClose)
+		}
+	}()
+
+	encoder := json.NewEncoder(f)
+	encoder.SetIndent("", "  ")
+	if err = encoder.Encode(data); err != nil {
+		return fmt.Errorf("failed to write token to file: %w", err)
+	}
+	return nil
+}
+
+// IsExpired checks if the token has expired.
+func (ts *KimiTokenStorage) IsExpired() bool {
+	if ts.Expired == "" {
+		return false // No expiry set, assume valid
+	}
+	t, err := time.Parse(time.RFC3339, ts.Expired)
+	if err != nil {
+		return true // Has expiry string but can't parse
+	}
+	// Consider expired if within refresh threshold
+	return time.Now().Add(time.Duration(refreshThresholdSeconds) * time.Second).After(t)
+}
+
+// NeedsRefresh checks if the token should be refreshed.
+func (ts *KimiTokenStorage) NeedsRefresh() bool {
+	if ts.RefreshToken == "" {
+		return false // Can't refresh without refresh token
+	}
+	return ts.IsExpired()
+}