diff --git a/cmd/server/main.go b/cmd/server/main.go
index 78259928..0a941b7c 100644
--- a/cmd/server/main.go
+++ b/cmd/server/main.go
@@ -57,6 +57,7 @@ func main() {
 	var iflowLogin bool
 	var noBrowser bool
 	var projectID string
+	var vertexImport string
 	var configPath string
 	var password string
 
@@ -69,6 +70,7 @@ func main() {
 	flag.BoolVar(&noBrowser, "no-browser", false, "Don't open browser automatically for OAuth")
 	flag.StringVar(&projectID, "project_id", "", "Project ID (Gemini only, not required)")
 	flag.StringVar(&configPath, "config", DefaultConfigPath, "Configure File Path")
+	flag.StringVar(&vertexImport, "vertex-import", "", "Import Vertex service account key JSON file")
 	flag.StringVar(&password, "password", "", "")
 
 	flag.CommandLine.Usage = func() {
@@ -417,7 +419,10 @@ func main() {
 
 	// Handle different command modes based on the provided flags.
 
-	if login {
+	if vertexImport != "" {
+		// Handle Vertex service account import
+		cmd.DoVertexImport(cfg, vertexImport)
+	} else if login {
 		// Handle Google/Gemini login
 		cmd.DoLogin(cfg, projectID, options)
 	} else if codexLogin {
diff --git a/internal/auth/vertex/keyutil.go b/internal/auth/vertex/keyutil.go
new file mode 100644
index 00000000..a10ade17
--- /dev/null
+++ b/internal/auth/vertex/keyutil.go
@@ -0,0 +1,208 @@
+package vertex
+
+import (
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/json"
+	"encoding/pem"
+	"fmt"
+	"strings"
+)
+
+// NormalizeServiceAccountJSON normalizes the given JSON-encoded service account payload.
+// It returns the normalized JSON (with sanitized private_key) or, if normalization fails,
+// the original bytes and the encountered error.
+func NormalizeServiceAccountJSON(raw []byte) ([]byte, error) {
+	if len(raw) == 0 {
+		return raw, nil
+	}
+	var payload map[string]any
+	if err := json.Unmarshal(raw, &payload); err != nil {
+		return raw, err
+	}
+	normalized, err := NormalizeServiceAccountMap(payload)
+	if err != nil {
+		return raw, err
+	}
+	out, err := json.Marshal(normalized)
+	if err != nil {
+		return raw, err
+	}
+	return out, nil
+}
+
+// NormalizeServiceAccountMap returns a copy of the given service account map with
+// a sanitized private_key field that is guaranteed to contain a valid RSA PRIVATE KEY PEM block.
+func NormalizeServiceAccountMap(sa map[string]any) (map[string]any, error) {
+	if sa == nil {
+		return nil, fmt.Errorf("service account payload is empty")
+	}
+	pk, _ := sa["private_key"].(string)
+	if strings.TrimSpace(pk) == "" {
+		return nil, fmt.Errorf("service account missing private_key")
+	}
+	normalized, err := sanitizePrivateKey(pk)
+	if err != nil {
+		return nil, err
+	}
+	clone := make(map[string]any, len(sa))
+	for k, v := range sa {
+		clone[k] = v
+	}
+	clone["private_key"] = normalized
+	return clone, nil
+}
+
+func sanitizePrivateKey(raw string) (string, error) {
+	pk := strings.ReplaceAll(raw, "\r\n", "\n")
+	pk = strings.ReplaceAll(pk, "\r", "\n")
+	pk = stripANSIEscape(pk)
+	pk = strings.ToValidUTF8(pk, "")
+	pk = strings.TrimSpace(pk)
+
+	normalized := pk
+	if block, _ := pem.Decode([]byte(pk)); block == nil {
+		// Attempt to reconstruct from the textual payload.
+		if reconstructed, err := rebuildPEM(pk); err == nil {
+			normalized = reconstructed
+		} else {
+			return "", fmt.Errorf("private_key is not valid pem: %w", err)
+		}
+	}
+
+	block, _ := pem.Decode([]byte(normalized))
+	if block == nil {
+		return "", fmt.Errorf("private_key pem decode failed")
+	}
+
+	rsaBlock, err := ensureRSAPrivateKey(block)
+	if err != nil {
+		return "", err
+	}
+	return string(pem.EncodeToMemory(rsaBlock)), nil
+}
+
+func ensureRSAPrivateKey(block *pem.Block) (*pem.Block, error) {
+	if block == nil {
+		return nil, fmt.Errorf("pem block is nil")
+	}
+
+	if block.Type == "RSA PRIVATE KEY" {
+		if _, err := x509.ParsePKCS1PrivateKey(block.Bytes); err != nil {
+			return nil, fmt.Errorf("private_key invalid rsa: %w", err)
+		}
+		return block, nil
+	}
+
+	if block.Type == "PRIVATE KEY" {
+		key, err := x509.ParsePKCS8PrivateKey(block.Bytes)
+		if err != nil {
+			return nil, fmt.Errorf("private_key invalid pkcs8: %w", err)
+		}
+		rsaKey, ok := key.(*rsa.PrivateKey)
+		if !ok {
+			return nil, fmt.Errorf("private_key is not an RSA key")
+		}
+		der := x509.MarshalPKCS1PrivateKey(rsaKey)
+		return &pem.Block{Type: "RSA PRIVATE KEY", Bytes: der}, nil
+	}
+
+	// Attempt auto-detection: try PKCS#1 first, then PKCS#8.
+	if rsaKey, err := x509.ParsePKCS1PrivateKey(block.Bytes); err == nil {
+		der := x509.MarshalPKCS1PrivateKey(rsaKey)
+		return &pem.Block{Type: "RSA PRIVATE KEY", Bytes: der}, nil
+	}
+	if key, err := x509.ParsePKCS8PrivateKey(block.Bytes); err == nil {
+		if rsaKey, ok := key.(*rsa.PrivateKey); ok {
+			der := x509.MarshalPKCS1PrivateKey(rsaKey)
+			return &pem.Block{Type: "RSA PRIVATE KEY", Bytes: der}, nil
+		}
+	}
+	return nil, fmt.Errorf("private_key uses unsupported format")
+}
+
+func rebuildPEM(raw string) (string, error) {
+	kind := "PRIVATE KEY"
+	if strings.Contains(raw, "RSA PRIVATE KEY") {
+		kind = "RSA PRIVATE KEY"
+	}
+	header := "-----BEGIN " + kind + "-----"
+	footer := "-----END " + kind + "-----"
+	start := strings.Index(raw, header)
+	end := strings.Index(raw, footer)
+	if start < 0 || end <= start {
+		return "", fmt.Errorf("missing pem markers")
+	}
+	body := raw[start+len(header) : end]
+	payload := filterBase64(body)
+	if payload == "" {
+		return "", fmt.Errorf("private_key base64 payload empty")
+	}
+	der, err := base64.StdEncoding.DecodeString(payload)
+	if err != nil {
+		return "", fmt.Errorf("private_key base64 decode failed: %w", err)
+	}
+	block := &pem.Block{Type: kind, Bytes: der}
+	return string(pem.EncodeToMemory(block)), nil
+}
+
+func filterBase64(s string) string {
+	var b strings.Builder
+	for _, r := range s {
+		switch {
+		case r >= 'A' && r <= 'Z':
+			b.WriteRune(r)
+		case r >= 'a' && r <= 'z':
+			b.WriteRune(r)
+		case r >= '0' && r <= '9':
+			b.WriteRune(r)
+		case r == '+' || r == '/' || r == '=':
+			b.WriteRune(r)
+		default:
+			// skip
+		}
+	}
+	return b.String()
+}
+
+func stripANSIEscape(s string) string {
+	in := []rune(s)
+	var out []rune
+	for i := 0; i < len(in); i++ {
+		r := in[i]
+		if r != 0x1b {
+			out = append(out, r)
+			continue
+		}
+		if i+1 >= len(in) {
+			continue
+		}
+		next := in[i+1]
+		switch next {
+		case ']':
+			i += 2
+			for i < len(in) {
+				if in[i] == 0x07 {
+					break
+				}
+				if in[i] == 0x1b && i+1 < len(in) && in[i+1] == '\\' {
+					i++
+					break
+				}
+				i++
+			}
+		case '[':
+			i += 2
+			for i < len(in) {
+				if (in[i] >= 'A' && in[i] <= 'Z') || (in[i] >= 'a' && in[i] <= 'z') {
+					break
+				}
+				i++
+			}
+		default:
+			// skip single ESC
+		}
+	}
+	return string(out)
+}
diff --git a/internal/auth/vertex/vertex_credentials.go b/internal/auth/vertex/vertex_credentials.go
new file mode 100644
index 00000000..4853d340
--- /dev/null
+++ b/internal/auth/vertex/vertex_credentials.go
@@ -0,0 +1,66 @@
+// Package vertex provides token storage for Google Vertex AI Gemini via service account credentials.
+// It serialises service account JSON into an auth file that is consumed by the runtime executor.
+package vertex
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/router-for-me/CLIProxyAPI/v6/internal/misc"
+	log "github.com/sirupsen/logrus"
+)
+
+// VertexCredentialStorage stores the service account JSON for Vertex AI access.
+// The content is persisted verbatim under the "service_account" key, together with
+// helper fields for project, location and email to improve logging and discovery.
+type VertexCredentialStorage struct {
+	// ServiceAccount holds the parsed service account JSON content.
+	ServiceAccount map[string]any `json:"service_account"`
+
+	// ProjectID is derived from the service account JSON (project_id).
+	ProjectID string `json:"project_id"`
+
+	// Email is the client_email from the service account JSON.
+	Email string `json:"email"`
+
+	// Location optionally sets a default region (e.g., us-central1) for Vertex endpoints.
+	Location string `json:"location,omitempty"`
+
+	// Type is the provider identifier stored alongside credentials. Always "vertex".
+	Type string `json:"type"`
+}
+
+// SaveTokenToFile writes the credential payload to the given file path in JSON format.
+// It ensures the parent directory exists and logs the operation for transparency.
+func (s *VertexCredentialStorage) SaveTokenToFile(authFilePath string) error {
+	misc.LogSavingCredentials(authFilePath)
+	if s == nil {
+		return fmt.Errorf("vertex credential: storage is nil")
+	}
+	if s.ServiceAccount == nil {
+		return fmt.Errorf("vertex credential: service account content is empty")
+	}
+	// Ensure we tag the file with the provider type.
+	s.Type = "vertex"
+
+	if err := os.MkdirAll(filepath.Dir(authFilePath), 0o700); err != nil {
+		return fmt.Errorf("vertex credential: create directory failed: %w", err)
+	}
+	f, err := os.Create(authFilePath)
+	if err != nil {
+		return fmt.Errorf("vertex credential: create file failed: %w", err)
+	}
+	defer func() {
+		if errClose := f.Close(); errClose != nil {
+			log.Errorf("vertex credential: failed to close file: %v", errClose)
+		}
+	}()
+	enc := json.NewEncoder(f)
+	enc.SetIndent("", "  ")
+	if err = enc.Encode(s); err != nil {
+		return fmt.Errorf("vertex credential: encode failed: %w", err)
+	}
+	return nil
+}
diff --git a/internal/cmd/vertex_import.go b/internal/cmd/vertex_import.go
new file mode 100644
index 00000000..ebb32d0c
--- /dev/null
+++ b/internal/cmd/vertex_import.go
@@ -0,0 +1,123 @@
+// Package cmd contains CLI helpers. This file implements importing a Vertex AI
+// service account JSON into the auth store as a dedicated "vertex" credential.
+package cmd
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/router-for-me/CLIProxyAPI/v6/internal/auth/vertex"
+	"github.com/router-for-me/CLIProxyAPI/v6/internal/config"
+	"github.com/router-for-me/CLIProxyAPI/v6/internal/util"
+	sdkAuth "github.com/router-for-me/CLIProxyAPI/v6/sdk/auth"
+	coreauth "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/auth"
+	log "github.com/sirupsen/logrus"
+)
+
+// DoVertexImport imports a Google Cloud service account key JSON and persists
+// it as a "vertex" provider credential. The file content is embedded in the auth
+// file to allow portable deployment across stores.
+func DoVertexImport(cfg *config.Config, keyPath string) {
+	if cfg == nil {
+		cfg = &config.Config{}
+	}
+	if resolved, errResolve := util.ResolveAuthDir(cfg.AuthDir); errResolve == nil {
+		cfg.AuthDir = resolved
+	}
+	rawPath := strings.TrimSpace(keyPath)
+	if rawPath == "" {
+		log.Fatalf("vertex-import: missing service account key path")
+		return
+	}
+	data, errRead := os.ReadFile(rawPath)
+	if errRead != nil {
+		log.Fatalf("vertex-import: read file failed: %v", errRead)
+		return
+	}
+	var sa map[string]any
+	if errUnmarshal := json.Unmarshal(data, &sa); errUnmarshal != nil {
+		log.Fatalf("vertex-import: invalid service account json: %v", errUnmarshal)
+		return
+	}
+	// Validate and normalize private_key before saving
+	normalizedSA, errFix := vertex.NormalizeServiceAccountMap(sa)
+	if errFix != nil {
+		log.Fatalf("vertex-import: %v", errFix)
+		return
+	}
+	sa = normalizedSA
+	email, _ := sa["client_email"].(string)
+	projectID, _ := sa["project_id"].(string)
+	if strings.TrimSpace(projectID) == "" {
+		log.Fatalf("vertex-import: project_id missing in service account json")
+		return
+	}
+	if strings.TrimSpace(email) == "" {
+		// Keep empty email but warn
+		log.Warn("vertex-import: client_email missing in service account json")
+	}
+	// Default location if not provided by user. Can be edited in the saved file later.
+	location := "us-central1"
+
+	fileName := fmt.Sprintf("vertex-%s.json", sanitizeFilePart(projectID))
+	// Build auth record
+	storage := &vertex.VertexCredentialStorage{
+		ServiceAccount: sa,
+		ProjectID:      projectID,
+		Email:          email,
+		Location:       location,
+	}
+	metadata := map[string]any{
+		"service_account": sa,
+		"project_id":      projectID,
+		"email":           email,
+		"location":        location,
+		"type":            "vertex",
+		"label":           labelForVertex(projectID, email),
+	}
+	record := &coreauth.Auth{
+		ID:       fileName,
+		Provider: "vertex",
+		FileName: fileName,
+		Storage:  storage,
+		Metadata: metadata,
+	}
+
+	store := sdkAuth.GetTokenStore()
+	if setter, ok := store.(interface{ SetBaseDir(string) }); ok {
+		setter.SetBaseDir(cfg.AuthDir)
+	}
+	path, errSave := store.Save(context.Background(), record)
+	if errSave != nil {
+		log.Fatalf("vertex-import: save credential failed: %v", errSave)
+		return
+	}
+	fmt.Printf("Vertex credentials imported: %s\n", path)
+}
+
+func sanitizeFilePart(s string) string {
+	out := strings.TrimSpace(s)
+	replacers := []string{"/", "_", "\\", "_", ":", "_", " ", "-"}
+	for i := 0; i < len(replacers); i += 2 {
+		out = strings.ReplaceAll(out, replacers[i], replacers[i+1])
+	}
+	return out
+}
+
+func labelForVertex(projectID, email string) string {
+	p := strings.TrimSpace(projectID)
+	e := strings.TrimSpace(email)
+	if p != "" && e != "" {
+		return fmt.Sprintf("%s (%s)", p, e)
+	}
+	if p != "" {
+		return p
+	}
+	if e != "" {
+		return e
+	}
+	return "vertex"
+}
diff --git a/internal/runtime/executor/gemini_vertex_executor.go b/internal/runtime/executor/gemini_vertex_executor.go
new file mode 100644
index 00000000..4e606390
--- /dev/null
+++ b/internal/runtime/executor/gemini_vertex_executor.go
@@ -0,0 +1,421 @@
+// Package executor contains provider executors. This file implements the Vertex AI
+// Gemini executor that talks to Google Vertex AI endpoints using service account
+// credentials imported by the CLI.
+package executor
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+
+	vertexauth "github.com/router-for-me/CLIProxyAPI/v6/internal/auth/vertex"
+	"github.com/router-for-me/CLIProxyAPI/v6/internal/config"
+	"github.com/router-for-me/CLIProxyAPI/v6/internal/util"
+	cliproxyauth "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/auth"
+	cliproxyexecutor "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/executor"
+	sdktranslator "github.com/router-for-me/CLIProxyAPI/v6/sdk/translator"
+	log "github.com/sirupsen/logrus"
+	"github.com/tidwall/gjson"
+	"github.com/tidwall/sjson"
+	"golang.org/x/oauth2/google"
+)
+
+const (
+	// vertexAPIVersion aligns with current public Vertex Generative AI API.
+	vertexAPIVersion = "v1"
+)
+
+// GeminiVertexExecutor sends requests to Vertex AI Gemini endpoints using service account credentials.
+type GeminiVertexExecutor struct {
+	cfg *config.Config
+}
+
+// NewGeminiVertexExecutor constructs the Vertex executor.
+func NewGeminiVertexExecutor(cfg *config.Config) *GeminiVertexExecutor {
+	return &GeminiVertexExecutor{cfg: cfg}
+}
+
+// Identifier returns provider key for manager routing.
+func (e *GeminiVertexExecutor) Identifier() string { return "vertex" }
+
+// PrepareRequest is a no-op for Vertex.
+func (e *GeminiVertexExecutor) PrepareRequest(_ *http.Request, _ *cliproxyauth.Auth) error {
+	return nil
+}
+
+// Execute handles non-streaming requests.
+func (e *GeminiVertexExecutor) Execute(ctx context.Context, auth *cliproxyauth.Auth, req cliproxyexecutor.Request, opts cliproxyexecutor.Options) (resp cliproxyexecutor.Response, err error) {
+	projectID, location, saJSON, errCreds := vertexCreds(auth)
+	if errCreds != nil {
+		return resp, errCreds
+	}
+
+	reporter := newUsageReporter(ctx, e.Identifier(), req.Model, auth)
+	defer reporter.trackFailure(ctx, &err)
+
+	from := opts.SourceFormat
+	to := sdktranslator.FromString("gemini")
+	body := sdktranslator.TranslateRequest(from, to, req.Model, bytes.Clone(req.Payload), false)
+	if budgetOverride, includeOverride, ok := util.GeminiThinkingFromMetadata(req.Metadata); ok && util.ModelSupportsThinking(req.Model) {
+		if budgetOverride != nil {
+			norm := util.NormalizeThinkingBudget(req.Model, *budgetOverride)
+			budgetOverride = &norm
+		}
+		body = util.ApplyGeminiThinkingConfig(body, budgetOverride, includeOverride)
+	}
+	body = util.StripThinkingConfigIfUnsupported(req.Model, body)
+	body = fixGeminiImageAspectRatio(req.Model, body)
+
+	action := "generateContent"
+	if req.Metadata != nil {
+		if a, _ := req.Metadata["action"].(string); a == "countTokens" {
+			action = "countTokens"
+		}
+	}
+	baseURL := vertexBaseURL(location)
+	url := fmt.Sprintf("%s/%s/projects/%s/locations/%s/publishers/google/models/%s:%s", baseURL, vertexAPIVersion, projectID, location, req.Model, action)
+	if opts.Alt != "" && action != "countTokens" {
+		url = url + fmt.Sprintf("?$alt=%s", opts.Alt)
+	}
+	body, _ = sjson.DeleteBytes(body, "session_id")
+
+	httpReq, errNewReq := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(body))
+	if errNewReq != nil {
+		return resp, errNewReq
+	}
+	httpReq.Header.Set("Content-Type", "application/json")
+	if token, errTok := vertexAccessToken(ctx, saJSON); errTok == nil && token != "" {
+		httpReq.Header.Set("Authorization", "Bearer "+token)
+	} else if errTok != nil {
+		log.Errorf("vertex executor: access token error: %v", errTok)
+		return resp, statusErr{code: 500, msg: "internal server error"}
+	}
+	applyGeminiHeaders(httpReq, auth)
+
+	var authID, authLabel, authType, authValue string
+	if auth != nil {
+		authID = auth.ID
+		authLabel = auth.Label
+		authType, authValue = auth.AccountInfo()
+	}
+	recordAPIRequest(ctx, e.cfg, upstreamRequestLog{
+		URL:       url,
+		Method:    http.MethodPost,
+		Headers:   httpReq.Header.Clone(),
+		Body:      body,
+		Provider:  e.Identifier(),
+		AuthID:    authID,
+		AuthLabel: authLabel,
+		AuthType:  authType,
+		AuthValue: authValue,
+	})
+
+	httpClient := newProxyAwareHTTPClient(ctx, e.cfg, auth, 0)
+	httpResp, errDo := httpClient.Do(httpReq)
+	if errDo != nil {
+		recordAPIResponseError(ctx, e.cfg, errDo)
+		return resp, errDo
+	}
+	defer func() {
+		if errClose := httpResp.Body.Close(); errClose != nil {
+			log.Errorf("vertex executor: close response body error: %v", errClose)
+		}
+	}()
+	recordAPIResponseMetadata(ctx, e.cfg, httpResp.StatusCode, httpResp.Header.Clone())
+	if httpResp.StatusCode < 200 || httpResp.StatusCode >= 300 {
+		b, _ := io.ReadAll(httpResp.Body)
+		appendAPIResponseChunk(ctx, e.cfg, b)
+		log.Debugf("request error, error status: %d, error body: %s", httpResp.StatusCode, summarizeErrorBody(httpResp.Header.Get("Content-Type"), b))
+		err = statusErr{code: httpResp.StatusCode, msg: string(b)}
+		return resp, err
+	}
+	data, errRead := io.ReadAll(httpResp.Body)
+	if errRead != nil {
+		recordAPIResponseError(ctx, e.cfg, errRead)
+		return resp, errRead
+	}
+	appendAPIResponseChunk(ctx, e.cfg, data)
+	reporter.publish(ctx, parseGeminiUsage(data))
+	var param any
+	out := sdktranslator.TranslateNonStream(ctx, to, from, req.Model, bytes.Clone(opts.OriginalRequest), body, data, &param)
+	resp = cliproxyexecutor.Response{Payload: []byte(out)}
+	return resp, nil
+}
+
+// ExecuteStream handles SSE streaming for Vertex.
+func (e *GeminiVertexExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.Auth, req cliproxyexecutor.Request, opts cliproxyexecutor.Options) (stream <-chan cliproxyexecutor.StreamChunk, err error) {
+	projectID, location, saJSON, errCreds := vertexCreds(auth)
+	if errCreds != nil {
+		return nil, errCreds
+	}
+
+	reporter := newUsageReporter(ctx, e.Identifier(), req.Model, auth)
+	defer reporter.trackFailure(ctx, &err)
+
+	from := opts.SourceFormat
+	to := sdktranslator.FromString("gemini")
+	body := sdktranslator.TranslateRequest(from, to, req.Model, bytes.Clone(req.Payload), true)
+	if budgetOverride, includeOverride, ok := util.GeminiThinkingFromMetadata(req.Metadata); ok && util.ModelSupportsThinking(req.Model) {
+		if budgetOverride != nil {
+			norm := util.NormalizeThinkingBudget(req.Model, *budgetOverride)
+			budgetOverride = &norm
+		}
+		body = util.ApplyGeminiThinkingConfig(body, budgetOverride, includeOverride)
+	}
+	body = util.StripThinkingConfigIfUnsupported(req.Model, body)
+	body = fixGeminiImageAspectRatio(req.Model, body)
+
+	baseURL := vertexBaseURL(location)
+	url := fmt.Sprintf("%s/%s/projects/%s/locations/%s/publishers/google/models/%s:%s", baseURL, vertexAPIVersion, projectID, location, req.Model, "streamGenerateContent")
+	if opts.Alt == "" {
+		url = url + "?alt=sse"
+	} else {
+		url = url + fmt.Sprintf("?$alt=%s", opts.Alt)
+	}
+	body, _ = sjson.DeleteBytes(body, "session_id")
+
+	httpReq, errNewReq := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(body))
+	if errNewReq != nil {
+		return nil, errNewReq
+	}
+	httpReq.Header.Set("Content-Type", "application/json")
+	if token, errTok := vertexAccessToken(ctx, saJSON); errTok == nil && token != "" {
+		httpReq.Header.Set("Authorization", "Bearer "+token)
+	} else if errTok != nil {
+		log.Errorf("vertex executor: access token error: %v", errTok)
+		return nil, statusErr{code: 500, msg: "internal server error"}
+	}
+	applyGeminiHeaders(httpReq, auth)
+
+	var authID, authLabel, authType, authValue string
+	if auth != nil {
+		authID = auth.ID
+		authLabel = auth.Label
+		authType, authValue = auth.AccountInfo()
+	}
+	recordAPIRequest(ctx, e.cfg, upstreamRequestLog{
+		URL:       url,
+		Method:    http.MethodPost,
+		Headers:   httpReq.Header.Clone(),
+		Body:      body,
+		Provider:  e.Identifier(),
+		AuthID:    authID,
+		AuthLabel: authLabel,
+		AuthType:  authType,
+		AuthValue: authValue,
+	})
+
+	httpClient := newProxyAwareHTTPClient(ctx, e.cfg, auth, 0)
+	httpResp, errDo := httpClient.Do(httpReq)
+	if errDo != nil {
+		recordAPIResponseError(ctx, e.cfg, errDo)
+		return nil, errDo
+	}
+	recordAPIResponseMetadata(ctx, e.cfg, httpResp.StatusCode, httpResp.Header.Clone())
+	if httpResp.StatusCode < 200 || httpResp.StatusCode >= 300 {
+		b, _ := io.ReadAll(httpResp.Body)
+		appendAPIResponseChunk(ctx, e.cfg, b)
+		log.Debugf("request error, error status: %d, error body: %s", httpResp.StatusCode, summarizeErrorBody(httpResp.Header.Get("Content-Type"), b))
+		if errClose := httpResp.Body.Close(); errClose != nil {
+			log.Errorf("vertex executor: close response body error: %v", errClose)
+		}
+		return nil, statusErr{code: httpResp.StatusCode, msg: string(b)}
+	}
+
+	out := make(chan cliproxyexecutor.StreamChunk)
+	stream = out
+	go func() {
+		defer close(out)
+		defer func() {
+			if errClose := httpResp.Body.Close(); errClose != nil {
+				log.Errorf("vertex executor: close response body error: %v", errClose)
+			}
+		}()
+		scanner := bufio.NewScanner(httpResp.Body)
+		buf := make([]byte, 20_971_520)
+		scanner.Buffer(buf, 20_971_520)
+		var param any
+		for scanner.Scan() {
+			line := scanner.Bytes()
+			appendAPIResponseChunk(ctx, e.cfg, line)
+			if detail, ok := parseGeminiStreamUsage(line); ok {
+				reporter.publish(ctx, detail)
+			}
+			lines := sdktranslator.TranslateStream(ctx, to, from, req.Model, bytes.Clone(opts.OriginalRequest), body, bytes.Clone(line), &param)
+			for i := range lines {
+				out <- cliproxyexecutor.StreamChunk{Payload: []byte(lines[i])}
+			}
+		}
+		lines := sdktranslator.TranslateStream(ctx, to, from, req.Model, bytes.Clone(opts.OriginalRequest), body, []byte("[DONE]"), &param)
+		for i := range lines {
+			out <- cliproxyexecutor.StreamChunk{Payload: []byte(lines[i])}
+		}
+		if errScan := scanner.Err(); errScan != nil {
+			recordAPIResponseError(ctx, e.cfg, errScan)
+			reporter.publishFailure(ctx)
+			out <- cliproxyexecutor.StreamChunk{Err: errScan}
+		}
+	}()
+	return stream, nil
+}
+
+// CountTokens calls Vertex countTokens endpoint.
+func (e *GeminiVertexExecutor) CountTokens(ctx context.Context, auth *cliproxyauth.Auth, req cliproxyexecutor.Request, opts cliproxyexecutor.Options) (cliproxyexecutor.Response, error) {
+	projectID, location, saJSON, errCreds := vertexCreds(auth)
+	if errCreds != nil {
+		return cliproxyexecutor.Response{}, errCreds
+	}
+	from := opts.SourceFormat
+	to := sdktranslator.FromString("gemini")
+	translatedReq := sdktranslator.TranslateRequest(from, to, req.Model, bytes.Clone(req.Payload), false)
+	if budgetOverride, includeOverride, ok := util.GeminiThinkingFromMetadata(req.Metadata); ok && util.ModelSupportsThinking(req.Model) {
+		if budgetOverride != nil {
+			norm := util.NormalizeThinkingBudget(req.Model, *budgetOverride)
+			budgetOverride = &norm
+		}
+		translatedReq = util.ApplyGeminiThinkingConfig(translatedReq, budgetOverride, includeOverride)
+	}
+	translatedReq = util.StripThinkingConfigIfUnsupported(req.Model, translatedReq)
+	translatedReq = fixGeminiImageAspectRatio(req.Model, translatedReq)
+	respCtx := context.WithValue(ctx, "alt", opts.Alt)
+	translatedReq, _ = sjson.DeleteBytes(translatedReq, "tools")
+	translatedReq, _ = sjson.DeleteBytes(translatedReq, "generationConfig")
+	translatedReq, _ = sjson.DeleteBytes(translatedReq, "safetySettings")
+
+	baseURL := vertexBaseURL(location)
+	url := fmt.Sprintf("%s/%s/projects/%s/locations/%s/publishers/google/models/%s:%s", baseURL, vertexAPIVersion, projectID, location, req.Model, "countTokens")
+
+	httpReq, errNewReq := http.NewRequestWithContext(respCtx, http.MethodPost, url, bytes.NewReader(translatedReq))
+	if errNewReq != nil {
+		return cliproxyexecutor.Response{}, errNewReq
+	}
+	httpReq.Header.Set("Content-Type", "application/json")
+	if token, errTok := vertexAccessToken(ctx, saJSON); errTok == nil && token != "" {
+		httpReq.Header.Set("Authorization", "Bearer "+token)
+	} else if errTok != nil {
+		log.Errorf("vertex executor: access token error: %v", errTok)
+		return cliproxyexecutor.Response{}, statusErr{code: 500, msg: "internal server error"}
+	}
+	applyGeminiHeaders(httpReq, auth)
+
+	var authID, authLabel, authType, authValue string
+	if auth != nil {
+		authID = auth.ID
+		authLabel = auth.Label
+		authType, authValue = auth.AccountInfo()
+	}
+	recordAPIRequest(ctx, e.cfg, upstreamRequestLog{
+		URL:       url,
+		Method:    http.MethodPost,
+		Headers:   httpReq.Header.Clone(),
+		Body:      translatedReq,
+		Provider:  e.Identifier(),
+		AuthID:    authID,
+		AuthLabel: authLabel,
+		AuthType:  authType,
+		AuthValue: authValue,
+	})
+
+	httpClient := newProxyAwareHTTPClient(ctx, e.cfg, auth, 0)
+	httpResp, errDo := httpClient.Do(httpReq)
+	if errDo != nil {
+		recordAPIResponseError(ctx, e.cfg, errDo)
+		return cliproxyexecutor.Response{}, errDo
+	}
+	defer func() {
+		if errClose := httpResp.Body.Close(); errClose != nil {
+			log.Errorf("vertex executor: close response body error: %v", errClose)
+		}
+	}()
+	recordAPIResponseMetadata(ctx, e.cfg, httpResp.StatusCode, httpResp.Header.Clone())
+	if httpResp.StatusCode < 200 || httpResp.StatusCode >= 300 {
+		b, _ := io.ReadAll(httpResp.Body)
+		appendAPIResponseChunk(ctx, e.cfg, b)
+		log.Debugf("request error, error status: %d, error body: %s", httpResp.StatusCode, summarizeErrorBody(httpResp.Header.Get("Content-Type"), b))
+		return cliproxyexecutor.Response{}, statusErr{code: httpResp.StatusCode, msg: string(b)}
+	}
+	data, errRead := io.ReadAll(httpResp.Body)
+	if errRead != nil {
+		recordAPIResponseError(ctx, e.cfg, errRead)
+		return cliproxyexecutor.Response{}, errRead
+	}
+	appendAPIResponseChunk(ctx, e.cfg, data)
+	if httpResp.StatusCode < 200 || httpResp.StatusCode >= 300 {
+		log.Debugf("request error, error status: %d, error body: %s", httpResp.StatusCode, summarizeErrorBody(httpResp.Header.Get("Content-Type"), data))
+		return cliproxyexecutor.Response{}, statusErr{code: httpResp.StatusCode, msg: string(data)}
+	}
+	count := gjson.GetBytes(data, "totalTokens").Int()
+	out := sdktranslator.TranslateTokenCount(ctx, to, from, count, data)
+	return cliproxyexecutor.Response{Payload: []byte(out)}, nil
+}
+
+// Refresh is a no-op for service account based credentials.
+func (e *GeminiVertexExecutor) Refresh(_ context.Context, auth *cliproxyauth.Auth) (*cliproxyauth.Auth, error) {
+	return auth, nil
+}
+
+// vertexCreds extracts project, location and raw service account JSON from auth metadata.
+func vertexCreds(a *cliproxyauth.Auth) (projectID, location string, serviceAccountJSON []byte, err error) {
+	if a == nil || a.Metadata == nil {
+		return "", "", nil, fmt.Errorf("vertex executor: missing auth metadata")
+	}
+	if v, ok := a.Metadata["project_id"].(string); ok {
+		projectID = strings.TrimSpace(v)
+	}
+	if projectID == "" {
+		// Some service accounts may use "project"; still prefer standard field
+		if v, ok := a.Metadata["project"].(string); ok {
+			projectID = strings.TrimSpace(v)
+		}
+	}
+	if projectID == "" {
+		return "", "", nil, fmt.Errorf("vertex executor: missing project_id in credentials")
+	}
+	if v, ok := a.Metadata["location"].(string); ok && strings.TrimSpace(v) != "" {
+		location = strings.TrimSpace(v)
+	} else {
+		location = "us-central1"
+	}
+	var sa map[string]any
+	if raw, ok := a.Metadata["service_account"].(map[string]any); ok {
+		sa = raw
+	}
+	if sa == nil {
+		return "", "", nil, fmt.Errorf("vertex executor: missing service_account in credentials")
+	}
+	normalized, errNorm := vertexauth.NormalizeServiceAccountMap(sa)
+	if errNorm != nil {
+		return "", "", nil, fmt.Errorf("vertex executor: %w", errNorm)
+	}
+	saJSON, errMarshal := json.Marshal(normalized)
+	if errMarshal != nil {
+		return "", "", nil, fmt.Errorf("vertex executor: marshal service_account failed: %w", errMarshal)
+	}
+	return projectID, location, saJSON, nil
+}
+
+func vertexBaseURL(location string) string {
+	loc := strings.TrimSpace(location)
+	if loc == "" {
+		loc = "us-central1"
+	}
+	return fmt.Sprintf("https://%s-aiplatform.googleapis.com", loc)
+}
+
+func vertexAccessToken(ctx context.Context, saJSON []byte) (string, error) {
+	// Use cloud-platform scope for Vertex AI.
+	creds, errCreds := google.CredentialsFromJSON(ctx, saJSON, "https://www.googleapis.com/auth/cloud-platform")
+	if errCreds != nil {
+		return "", fmt.Errorf("vertex executor: parse service account json failed: %w", errCreds)
+	}
+	tok, errTok := creds.TokenSource.Token()
+	if errTok != nil {
+		return "", fmt.Errorf("vertex executor: get access token failed: %w", errTok)
+	}
+	return tok.AccessToken, nil
+}
diff --git a/sdk/cliproxy/service.go b/sdk/cliproxy/service.go
index 84d15ffe..57ad3295 100644
--- a/sdk/cliproxy/service.go
+++ b/sdk/cliproxy/service.go
@@ -324,6 +324,8 @@ func (s *Service) ensureExecutorsForAuth(a *coreauth.Auth) {
 	switch strings.ToLower(a.Provider) {
 	case "gemini":
 		s.coreManager.RegisterExecutor(executor.NewGeminiExecutor(s.cfg))
+	case "vertex":
+		s.coreManager.RegisterExecutor(executor.NewGeminiVertexExecutor(s.cfg))
 	case "gemini-cli":
 		s.coreManager.RegisterExecutor(executor.NewGeminiCLIExecutor(s.cfg))
 	case "aistudio":
@@ -619,6 +621,9 @@ func (s *Service) registerModelsForAuth(a *coreauth.Auth) {
 	switch provider {
 	case "gemini":
 		models = registry.GetGeminiModels()
+	case "vertex":
+		// Vertex AI Gemini supports the same model identifiers as Gemini.
+		models = registry.GetGeminiModels()
 	case "gemini-cli":
 		models = registry.GetGeminiCLIModels()
 	case "aistudio":