diff --git a/backend/internal/service/upstream_models.go b/backend/internal/service/upstream_models.go
index df926b0297..3941794860 100644
--- a/backend/internal/service/upstream_models.go
+++ b/backend/internal/service/upstream_models.go
@@ -343,6 +343,9 @@ func (s *AccountTestService) buildAntigravityAPIKeyModelsRequest(ctx context.Con
 }
 
 func (s *AccountTestService) buildOpenAIUpstreamModelsRequest(ctx context.Context, account *Account) (*http.Request, error) {
+	if account.IsOpenAIOAuth() {
+		return s.buildOpenAIOAuthUpstreamModelsRequest(ctx, account)
+	}
 	if account.Type != AccountTypeAPIKey {
 		return nil, newUpstreamModelSyncUnsupportedError(
 			fmt.Sprintf("Unsupported OpenAI account type for upstream model sync: %s", account.Type), nil,
@@ -375,6 +378,68 @@ func (s *AccountTestService) buildOpenAIUpstreamModelsRequest(ctx context.Contex
 	return req, nil
 }
 
+// buildOpenAIOAuthUpstreamModelsRequest uses ChatGPT's Codex model manifest.
+// OAuth subscriptions do not expose the public Platform API /v1/models endpoint,
+// so treating them like API-key accounts makes the admin sync button fail locally.
+func (s *AccountTestService) buildOpenAIOAuthUpstreamModelsRequest(ctx context.Context, account *Account) (*http.Request, error) {
+	credentialAccount, err := resolveCredentialAccount(ctx, s.accountRepo, account)
+	if err != nil {
+		return nil, newUpstreamModelSyncConfigError("Failed to resolve OpenAI account credentials", err)
+	}
+	if !credentialAccount.IsOpenAIOAuth() {
+		return nil, newUpstreamModelSyncUnsupportedError(
+			fmt.Sprintf("Unsupported OpenAI account type for upstream model sync: %s", credentialAccount.Type), nil,
+		)
+	}
+
+	modelsURL, err := buildCodexModelsManifestURL(
+		chatgptCodexModelsURL,
+		false,
+		CodexCanonicalClientVersion(),
+	)
+	if err != nil {
+		return nil, newUpstreamModelSyncConfigError("Invalid OpenAI Codex model list URL", err)
+	}
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, modelsURL.String(), nil)
+	if err != nil {
+		return nil, newUpstreamModelSyncConfigError("Invalid OpenAI Codex model list request", err)
+	}
+
+	if credentialAccount.IsOpenAIAgentIdentity() {
+		authHeaders, authErr := buildAgentIdentityAuthenticationHeaders(
+			ctx,
+			s.accountRepo,
+			s.agentIdentityWS,
+			&s.agentIdentityTaskMu,
+			credentialAccount,
+		)
+		if authErr != nil {
+			return nil, newUpstreamModelSyncUpstreamError("Failed to build OpenAI Agent Identity authentication", authErr)
+		}
+		for key, values := range authHeaders {
+			for _, value := range values {
+				req.Header.Add(key, value)
+			}
+		}
+	} else {
+		accessToken := strings.TrimSpace(credentialAccount.GetOpenAIAccessToken())
+		if accessToken == "" {
+			return nil, newUpstreamModelSyncConfigError("No OpenAI access token is available", nil)
+		}
+		req.Header.Set("Authorization", "Bearer "+accessToken)
+	}
+
+	identity := resolveCodexOutboundIdentity(credentialAccount.GetOpenAIUserAgent())
+	req.Header.Set("Accept", "application/json")
+	req.Header.Set("Originator", identity.originator)
+	req.Header.Set("User-Agent", identity.userAgent)
+	req.Header.Set("Version", identity.version)
+	setOpenAIChatGPTAccountHeaders(req.Header, credentialAccount)
+	credentialAccount.ApplyHeaderOverrides(req.Header)
+	enforceCodexIdentityHeadersWithUA(req.Header, credentialAccount.GetOpenAIUserAgent())
+	return req, nil
+}
+
 func (s *AccountTestService) buildGeminiUpstreamModelsRequest(ctx context.Context, account *Account) (*http.Request, error) {
 	baseURL := account.GetGeminiBaseURL(geminicli.AIStudioBaseURL)
 	if strings.TrimSpace(baseURL) == "" {
@@ -498,6 +563,7 @@ func buildGeminiModelsURL(base string) string {
 
 type upstreamModelEntry struct {
 	ID           string          `json:"id"`
+	Slug         string          `json:"slug"`
 	Model        string          `json:"model"`
 	ModelID      string          `json:"modelId"`
 	ModelIDSnake string          `json:"model_id"`
@@ -561,6 +627,9 @@ func extractUpstreamModelIDsWithSelector(body []byte, selectID func(upstreamMode
 
 func upstreamModelEntryID(entry upstreamModelEntry) string {
 	modelID := strings.TrimSpace(entry.ID)
+	if modelID == "" {
+		modelID = strings.TrimSpace(entry.Slug)
+	}
 	if modelID == "" {
 		modelID = strings.TrimSpace(entry.Name)
 	}
diff --git a/backend/internal/service/upstream_models_test.go b/backend/internal/service/upstream_models_test.go
index 031d09b574..b6f3cb3f95 100644
--- a/backend/internal/service/upstream_models_test.go
+++ b/backend/internal/service/upstream_models_test.go
@@ -140,6 +140,11 @@ func TestExtractUpstreamModelIDs(t *testing.T) {
 			body: `{"data":[{"id":"canonical-id","model":"display-model"}]}`,
 			want: []string{"canonical-id"},
 		},
+		{
+			name: "codex manifest uses slug",
+			body: `{"models":[{"slug":"gpt-5.6-sol"},{"slug":"gpt-5.5-codex"}]}`,
+			want: []string{"gpt-5.5-codex", "gpt-5.6-sol"},
+		},
 	}
 
 	for _, tt := range tests {
@@ -154,6 +159,53 @@ func TestExtractUpstreamModelIDs(t *testing.T) {
 	}
 }
 
+func TestBuildUpstreamModelsRequestSupportsOpenAIOAuth(t *testing.T) {
+	svc := &AccountTestService{cfg: upstreamModelSyncTestConfig()}
+	account := &Account{
+		ID:       11,
+		Platform: PlatformOpenAI,
+		Type:     AccountTypeOAuth,
+		Credentials: map[string]any{
+			"access_token":       "openai-oauth-token",
+			"chatgpt_account_id": "chatgpt-account",
+		},
+	}
+
+	req, err := svc.buildUpstreamModelsRequest(context.Background(), account)
+	require.NoError(t, err)
+	require.Equal(t, chatgptCodexModelsURL, req.URL.Scheme+"://"+req.URL.Host+req.URL.Path)
+	require.NotEmpty(t, req.URL.Query().Get("client_version"))
+	require.Equal(t, "Bearer openai-oauth-token", req.Header.Get("Authorization"))
+	require.Equal(t, "chatgpt-account", req.Header.Get("chatgpt-account-id"))
+	require.NotEmpty(t, req.Header.Get("Originator"))
+	require.NotEmpty(t, req.Header.Get("User-Agent"))
+	require.NotEmpty(t, req.Header.Get("Version"))
+}
+
+func TestFetchUpstreamSupportedModelsParsesOpenAIOAuthManifest(t *testing.T) {
+	upstream := &httpUpstreamRecorder{resp: &http.Response{
+		StatusCode: http.StatusOK,
+		Header:     http.Header{"Content-Type": []string{"application/json"}},
+		Body:       io.NopCloser(strings.NewReader(`{"models":[{"slug":"gpt-5.6-sol"},{"slug":"gpt-5.5-codex"}]}`)),
+	}}
+	svc := &AccountTestService{
+		httpUpstream: upstream,
+		cfg:          upstreamModelSyncTestConfig(),
+	}
+
+	models, err := svc.FetchUpstreamSupportedModels(context.Background(), &Account{
+		ID:       12,
+		Platform: PlatformOpenAI,
+		Type:     AccountTypeOAuth,
+		Credentials: map[string]any{
+			"access_token": "openai-oauth-token",
+		},
+	})
+	require.NoError(t, err)
+	require.Equal(t, []string{"gpt-5.5-codex", "gpt-5.6-sol"}, models)
+	require.Equal(t, "Bearer openai-oauth-token", upstream.lastReq.Header.Get("Authorization"))
+}
+
 func TestExtractGrokUpstreamModelIDs(t *testing.T) {
 	t.Parallel()