diff --git a/backend/internal/handler/admin/account_codex_agent_identity_import_test.go b/backend/internal/handler/admin/account_codex_agent_identity_import_test.go
index 85d1a21f4a..2407fe3f92 100644
--- a/backend/internal/handler/admin/account_codex_agent_identity_import_test.go
+++ b/backend/internal/handler/admin/account_codex_agent_identity_import_test.go
@@ -47,6 +47,99 @@ func TestNormalizeCodexImportEntryAcceptsAgentIdentityAuthJSON(t *testing.T) {
 	require.NotEmpty(t, item.WarningTexts)
 }
 
+func TestBuildCodexAgentIdentityKeysUseChatGPTAccountOnly(t *testing.T) {
+	keys := buildCodexAgentIdentityKeys("team-a")
+	require.Equal(t, []string{"account:team-a"}, keys)
+}
+
+func TestCodexAgentIdentityIndexSeparatesTeamsForSameUser(t *testing.T) {
+	existing := service.Account{
+		ID: 1,
+		Credentials: map[string]any{
+			"auth_mode":          service.OpenAIAuthModeAgentIdentity,
+			"chatgpt_account_id": "team-a",
+			"chatgpt_user_id":    "same-user",
+			"agent_runtime_id":   "runtime-a",
+		},
+	}
+	index := buildCodexAccountIndex([]service.Account{existing})
+
+	teamBKeys := buildCodexAgentIdentityKeys("team-b")
+	matched, _ := index.Find(teamBKeys, "same-user")
+	require.Nil(t, matched)
+
+	teamAKeys := buildCodexAgentIdentityKeys("team-a")
+	matched, matchedKey := index.Find(teamAKeys, "same-user")
+	require.NotNil(t, matched)
+	require.Equal(t, int64(1), matched.ID)
+	require.Equal(t, "account:team-a", matchedKey)
+}
+
+func TestImportCodexSessionsKeepsAgentIdentityTeamsSeparate(t *testing.T) {
+	first := buildAgentIdentityImportValue(t, "runtime-a", "team-a", "same-user", "task-a")
+	second := buildAgentIdentityImportValue(t, "runtime-b", "team-b", "same-user", "task-b")
+	svc := newCodexImportMemoryAdminService(nil)
+	handler := NewAccountHandler(svc, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil)
+
+	result, err := handler.importCodexSessions(context.Background(), CodexSessionImportRequest{
+		SkipDefaultGroupBind: boolPtr(true),
+	}, []codexImportEntry{{Index: 1, Value: first}, {Index: 2, Value: second}})
+	require.NoError(t, err)
+	require.Equal(t, 2, result.Created)
+	require.Zero(t, result.Updated)
+	require.Zero(t, result.Skipped)
+	require.Len(t, svc.createdAccounts, 2)
+}
+
+func TestImportCodexSessionsMergesAgentIdentityRuntimesForSameTeam(t *testing.T) {
+	first := buildAgentIdentityImportValue(t, "runtime-a", "team-a", "same-user", "task-a")
+	second := buildAgentIdentityImportValue(t, "runtime-b", "team-a", "same-user", "task-b")
+	firstIdentity := first["agent_identity"].(map[string]any)
+	existing := service.Account{
+		ID:       41,
+		Platform: service.PlatformOpenAI,
+		Type:     service.AccountTypeOAuth,
+		Credentials: map[string]any{
+			"auth_mode":          service.OpenAIAuthModeAgentIdentity,
+			"agent_runtime_id":   firstIdentity["agent_runtime_id"],
+			"agent_private_key":  firstIdentity["agent_private_key"],
+			"task_id":            firstIdentity["task_id"],
+			"chatgpt_account_id": firstIdentity["account_id"],
+			"chatgpt_user_id":    firstIdentity["chatgpt_user_id"],
+		},
+	}
+	svc := newCodexImportMemoryAdminService([]service.Account{existing})
+	handler := NewAccountHandler(svc, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil)
+
+	result, err := handler.importCodexSessions(context.Background(), CodexSessionImportRequest{
+		SkipDefaultGroupBind: boolPtr(true),
+	}, []codexImportEntry{{Index: 1, Value: second}})
+	require.NoError(t, err)
+	require.Zero(t, result.Created)
+	require.Equal(t, 1, result.Updated)
+	require.Len(t, svc.updatedAccounts, 1)
+	require.Equal(t, "runtime-b", svc.updatedAccounts[0].input.Credentials["agent_runtime_id"])
+	require.Equal(t, "task-b", svc.updatedAccounts[0].input.Credentials["task_id"])
+}
+
+func buildAgentIdentityImportValue(t *testing.T, runtimeID, accountID, userID, taskID string) map[string]any {
+	t.Helper()
+	_, privateKey, err := ed25519.GenerateKey(rand.Reader)
+	require.NoError(t, err)
+	der, err := x509.MarshalPKCS8PrivateKey(privateKey)
+	require.NoError(t, err)
+	return map[string]any{
+		"auth_mode": "agentIdentity",
+		"agent_identity": map[string]any{
+			"agent_runtime_id":  runtimeID,
+			"agent_private_key": base64.StdEncoding.EncodeToString(der),
+			"task_id":           taskID,
+			"account_id":        accountID,
+			"chatgpt_user_id":   userID,
+		},
+	}
+}
+
 func TestImportCodexSessionsCreatesAgentIdentityWithoutOAuthExpiry(t *testing.T) {
 	_, privateKey, err := ed25519.GenerateKey(rand.Reader)
 	require.NoError(t, err)
diff --git a/backend/internal/handler/admin/account_codex_import.go b/backend/internal/handler/admin/account_codex_import.go
index aa471494f1..ba37ef3309 100644
--- a/backend/internal/handler/admin/account_codex_import.go
+++ b/backend/internal/handler/admin/account_codex_import.go
@@ -532,7 +532,7 @@ func normalizeCodexImportEntry(entry codexImportEntry) (*codexImportAccount, err
 			if item.AgentTaskID == "" {
 				item.WarningTexts = append(item.WarningTexts, "未包含 task_id，首次请求会使用现有 runtime 注册新 task")
 			}
-			item.IdentityKeys = buildCodexAgentIdentityKeys(item.AccountID, item.UserID, item.Email, item.AgentRuntimeID)
+			item.IdentityKeys = buildCodexAgentIdentityKeys(item.AccountID)
 			item.Name = buildCodexImportAccountName(item, entry.Index)
 			return item, nil
 		}
@@ -894,12 +894,17 @@ func buildCodexImportIdentityKeys(accountID, userID, email, accessToken, refresh
 	return buildCodexStoredIdentityKeys(accountID, userID, email, accessToken)
 }
 
-func buildCodexAgentIdentityKeys(accountID, userID, email, runtimeID string) []string {
-	keys := buildCodexStoredIdentityKeys(accountID, userID, email, "")
-	if runtimeID = strings.TrimSpace(runtimeID); runtimeID != "" {
-		keys = append([]string{"agent:" + runtimeID}, keys...)
+func buildCodexAgentIdentityKeys(accountID string) []string {
+	// Agent Identity credentials belonging to the same ChatGPT account are
+	// intentionally merged, while the same user may own multiple accounts.
+	// Do not use user/email/runtime as fallback keys here: user_id is shared
+	// across Team workspaces and runtime_id changes when a new runtime is
+	// registered for the same account.
+	accountID = strings.TrimSpace(accountID)
+	if accountID == "" {
+		return nil
 	}
-	return keys
+	return []string{"account:" + accountID}
 }
 
 // buildCodexStoredIdentityKeys 生成存量账号索引键，保留 user/account 维度，