diff --git a/backend/internal/handler/admin/account_codex_import.go b/backend/internal/handler/admin/account_codex_import.go
index 01a5fbfa1c..271bd19470 100644
--- a/backend/internal/handler/admin/account_codex_import.go
+++ b/backend/internal/handler/admin/account_codex_import.go
@@ -115,6 +115,10 @@ func (h *AccountHandler) ImportCodexSession(c *gin.Context) {
 		response.BadRequest(c, "Invalid request: "+err.Error())
 		return
 	}
+	if err := service.ValidateOpenAILongContextBillingExtra(service.PlatformOpenAI, req.Extra); err != nil {
+		response.ErrorFrom(c, err)
+		return
+	}
 	if req.Concurrency != nil && *req.Concurrency < 0 {
 		response.BadRequest(c, "concurrency must be >= 0")
 		return
diff --git a/backend/internal/handler/admin/account_codex_import_test.go b/backend/internal/handler/admin/account_codex_import_test.go
index a52463aa86..96a033d8c3 100644
--- a/backend/internal/handler/admin/account_codex_import_test.go
+++ b/backend/internal/handler/admin/account_codex_import_test.go
@@ -630,6 +630,7 @@ func TestImportCodexSessionsAccessTokenOnlySameUserUpdatesExisting(t *testing.T)
 			"chatgpt_user_id":    "user-1",
 			"access_token":       existingToken,
 		},
+		Extra: map[string]any{"openai_long_context_billing_enabled": false},
 	}})
 	handler := NewAccountHandler(svc, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil)
 	req := CodexSessionImportRequest{SkipDefaultGroupBind: boolPtr(true)}
@@ -650,6 +651,9 @@ func TestImportCodexSessionsAccessTokenOnlySameUserUpdatesExisting(t *testing.T)
 	if len(svc.updatedAccounts) != 1 || svc.updatedAccounts[0].id != 10 {
 		t.Fatalf("updated accounts = %+v, want account 10", svc.updatedAccounts)
 	}
+	if got := svc.updatedAccounts[0].input.Extra["openai_long_context_billing_enabled"]; got != false {
+		t.Fatalf("openai_long_context_billing_enabled = %v, want false", got)
+	}
 }
 
 func TestImportCodexSessionsUpgradesAccessTokenOnlyAccountWithRefreshToken(t *testing.T) {
diff --git a/backend/internal/handler/admin/account_handler.go b/backend/internal/handler/admin/account_handler.go
index a4b0773999..a7089b0107 100644
--- a/backend/internal/handler/admin/account_handler.go
+++ b/backend/internal/handler/admin/account_handler.go
@@ -784,6 +784,10 @@ func (h *AccountHandler) Create(c *gin.Context) {
 		response.BadRequest(c, "Invalid request: "+err.Error())
 		return
 	}
+	if err := service.ValidateOpenAILongContextBillingExtra(req.Platform, req.Extra); err != nil {
+		response.ErrorFrom(c, err)
+		return
+	}
 	if req.RateMultiplier != nil && *req.RateMultiplier < 0 {
 		response.BadRequest(c, "rate_multiplier must be >= 0")
 		return
@@ -1592,6 +1596,12 @@ func (h *AccountHandler) BatchCreate(c *gin.Context) {
 		response.BadRequest(c, "Invalid request: "+err.Error())
 		return
 	}
+	for _, item := range req.Accounts {
+		if err := service.ValidateOpenAILongContextBillingExtra(item.Platform, item.Extra); err != nil {
+			response.ErrorFrom(c, err)
+			return
+		}
+	}
 
 	executeAdminIdempotentJSON(c, "admin.accounts.batch_create", req, service.DefaultWriteIdempotencyTTL(), func(ctx context.Context) (any, error) {
 		success := 0
diff --git a/backend/internal/handler/admin/account_handler_long_context_billing_test.go b/backend/internal/handler/admin/account_handler_long_context_billing_test.go
new file mode 100644
index 0000000000..340d077792
--- /dev/null
+++ b/backend/internal/handler/admin/account_handler_long_context_billing_test.go
@@ -0,0 +1,135 @@
+package admin
+
+import (
+	"bytes"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	infraerrors "github.com/Wei-Shaw/sub2api/internal/pkg/errors"
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/require"
+)
+
+func TestAccountAdminBoundariesRejectMalformedOpenAILongContextBillingValue(t *testing.T) {
+	const malformedExtra = `"extra":{"openai_long_context_billing_enabled":"true"}`
+
+	tests := []struct {
+		name   string
+		method string
+		path   string
+		body   string
+		mount  func(*gin.Engine, *AccountHandler)
+		setup  func(*stubAdminService)
+	}{
+		{
+			name:   "create",
+			method: http.MethodPost,
+			path:   "/accounts",
+			body:   `{"name":"account","platform":"openai","type":"apikey","credentials":{"api_key":"test"},` + malformedExtra + `}`,
+			mount:  func(router *gin.Engine, handler *AccountHandler) { router.POST("/accounts", handler.Create) },
+		},
+		{
+			name:   "update",
+			method: http.MethodPut,
+			path:   "/accounts/1",
+			body:   `{` + malformedExtra + `}`,
+			mount:  func(router *gin.Engine, handler *AccountHandler) { router.PUT("/accounts/:id", handler.Update) },
+			setup: func(stub *stubAdminService) {
+				stub.updateAccountErr = infraerrors.BadRequest("OPENAI_LONG_CONTEXT_BILLING_INVALID", "invalid")
+			},
+		},
+		{
+			name:   "bulk update",
+			method: http.MethodPost,
+			path:   "/accounts/bulk-update",
+			body:   `{"account_ids":[1],` + malformedExtra + `}`,
+			mount: func(router *gin.Engine, handler *AccountHandler) {
+				router.POST("/accounts/bulk-update", handler.BulkUpdate)
+			},
+			setup: func(stub *stubAdminService) {
+				stub.bulkUpdateAccountErr = infraerrors.BadRequest("OPENAI_LONG_CONTEXT_BILLING_INVALID", "invalid")
+			},
+		},
+		{
+			name:   "batch create",
+			method: http.MethodPost,
+			path:   "/accounts/batch",
+			body:   `{"accounts":[{"name":"account","platform":"openai","type":"apikey","credentials":{"api_key":"test"},` + malformedExtra + `}]}`,
+			mount:  func(router *gin.Engine, handler *AccountHandler) { router.POST("/accounts/batch", handler.BatchCreate) },
+		},
+		{
+			name:   "Codex session import",
+			method: http.MethodPost,
+			path:   "/accounts/import-codex-session",
+			body:   `{"content":"token",` + malformedExtra + `}`,
+			mount: func(router *gin.Engine, handler *AccountHandler) {
+				router.POST("/accounts/import-codex-session", handler.ImportCodexSession)
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			gin.SetMode(gin.TestMode)
+			stub := newStubAdminService()
+			if tt.setup != nil {
+				tt.setup(stub)
+			}
+			handler := NewAccountHandler(stub, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil)
+			router := gin.New()
+			tt.mount(router, handler)
+			recorder := httptest.NewRecorder()
+			request := httptest.NewRequest(tt.method, tt.path, bytes.NewBufferString(tt.body))
+			request.Header.Set("Content-Type", "application/json")
+
+			router.ServeHTTP(recorder, request)
+
+			require.Equal(t, http.StatusBadRequest, recorder.Code)
+			var responseBody struct {
+				Reason string `json:"reason"`
+			}
+			require.NoError(t, json.Unmarshal(recorder.Body.Bytes(), &responseBody))
+			require.Equal(t, "OPENAI_LONG_CONTEXT_BILLING_INVALID", responseBody.Reason)
+		})
+	}
+}
+
+func TestAccountCreateBoundaryDoesNotApplyOpenAIValidationToOtherPlatforms(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	handler := NewAccountHandler(newStubAdminService(), nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil)
+	router := gin.New()
+	router.POST("/accounts", handler.Create)
+	recorder := httptest.NewRecorder()
+	request := httptest.NewRequest(http.MethodPost, "/accounts", bytes.NewBufferString(
+		`{"name":"account","platform":"anthropic","type":"apikey","credentials":{"api_key":"test"},"extra":{"openai_long_context_billing_enabled":"provider-owned"}}`,
+	))
+	request.Header.Set("Content-Type", "application/json")
+
+	router.ServeHTTP(recorder, request)
+
+	require.Equal(t, http.StatusOK, recorder.Code)
+}
+
+func TestOpenAIOAuthCodexPATBoundaryRejectsMalformedOpenAILongContextBillingValueBeforeTokenValidation(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	handler := NewOpenAIOAuthHandler(nil, newStubAdminService(), nil)
+	router := gin.New()
+	router.Use(gin.Recovery())
+	router.POST("/openai/create-from-codex-pat", handler.CreateAccountFromCodexPAT)
+	recorder := httptest.NewRecorder()
+	request := httptest.NewRequest(http.MethodPost, "/openai/create-from-codex-pat", bytes.NewBufferString(
+		`{"access_token":"token","extra":{"openai_long_context_billing_enabled":1}}`,
+	))
+	request.Header.Set("Content-Type", "application/json")
+
+	router.ServeHTTP(recorder, request)
+
+	require.Equal(t, http.StatusBadRequest, recorder.Code)
+	var responseBody struct {
+		Reason string `json:"reason"`
+	}
+	require.NoError(t, json.Unmarshal(recorder.Body.Bytes(), &responseBody))
+	require.Equal(t, "OPENAI_LONG_CONTEXT_BILLING_INVALID", responseBody.Reason)
+}
diff --git a/backend/internal/handler/admin/openai_oauth_handler.go b/backend/internal/handler/admin/openai_oauth_handler.go
index d7a756bd00..78d57299b6 100644
--- a/backend/internal/handler/admin/openai_oauth_handler.go
+++ b/backend/internal/handler/admin/openai_oauth_handler.go
@@ -304,6 +304,10 @@ func (h *OpenAIOAuthHandler) CreateAccountFromCodexPAT(c *gin.Context) {
 		response.BadRequest(c, "Invalid request: "+err.Error())
 		return
 	}
+	if err := service.ValidateOpenAILongContextBillingExtra(service.PlatformOpenAI, req.Extra); err != nil {
+		response.ErrorFrom(c, err)
+		return
+	}
 	if req.Concurrency != nil && *req.Concurrency < 0 {
 		response.BadRequest(c, "concurrency must be >= 0")
 		return
diff --git a/backend/internal/repository/openai_long_context_billing_migration_integration_test.go b/backend/internal/repository/openai_long_context_billing_migration_integration_test.go
new file mode 100644
index 0000000000..f325d5c031
--- /dev/null
+++ b/backend/internal/repository/openai_long_context_billing_migration_integration_test.go
@@ -0,0 +1,159 @@
+//go:build integration
+
+package repository
+
+import (
+	"context"
+	"testing"
+
+	dbmigrations "github.com/Wei-Shaw/sub2api/migrations"
+	"github.com/stretchr/testify/require"
+)
+
+func TestMigration175EnforcesOpenAILongContextBillingWriteInvariant(t *testing.T) {
+	tx := testTx(t)
+	ctx := context.Background()
+	migrationSQL, err := dbmigrations.FS.ReadFile("175_default_openai_long_context_billing.sql")
+	require.NoError(t, err)
+	_, err = tx.ExecContext(ctx, `
+DROP TRIGGER IF EXISTS accounts_propagate_openai_long_context_billing_extra ON accounts;
+DROP TRIGGER IF EXISTS accounts_enforce_openai_long_context_billing_extra ON accounts;
+`)
+	require.NoError(t, err)
+
+	var ordinaryID int64
+	require.NoError(t, tx.QueryRowContext(ctx, `
+INSERT INTO accounts (name, platform, type, extra)
+VALUES ('migration-175-ordinary', 'openai', 'oauth', '{}'::jsonb)
+RETURNING id
+`).Scan(&ordinaryID))
+
+	var parentID int64
+	require.NoError(t, tx.QueryRowContext(ctx, `
+INSERT INTO accounts (name, platform, type, extra)
+VALUES ('migration-175-parent', 'openai', 'oauth', '{"openai_long_context_billing_enabled":false}'::jsonb)
+RETURNING id
+`).Scan(&parentID))
+
+	var shadowID int64
+	require.NoError(t, tx.QueryRowContext(ctx, `
+INSERT INTO accounts (name, platform, type, extra, parent_account_id, quota_dimension)
+VALUES ('migration-175-shadow', 'openai', 'oauth', '{}'::jsonb, $1, 'spark')
+RETURNING id
+`, parentID).Scan(&shadowID))
+
+	var malformedLegacyID int64
+	require.NoError(t, tx.QueryRowContext(ctx, `
+INSERT INTO accounts (name, platform, type, extra)
+VALUES ('migration-175-malformed-legacy', 'openai', 'oauth', '{"openai_long_context_billing_enabled":"false"}'::jsonb)
+RETURNING id
+`).Scan(&malformedLegacyID))
+
+	_, err = tx.ExecContext(ctx, string(migrationSQL))
+	require.NoError(t, err)
+	_, err = tx.ExecContext(ctx, string(migrationSQL))
+	require.NoError(t, err)
+
+	var ordinaryEnabled bool
+	require.NoError(t, tx.QueryRowContext(ctx, `
+SELECT (extra->>'openai_long_context_billing_enabled')::boolean
+FROM accounts
+WHERE id = $1
+`, ordinaryID).Scan(&ordinaryEnabled))
+	require.True(t, ordinaryEnabled)
+
+	var shadowEnabled bool
+	require.NoError(t, tx.QueryRowContext(ctx, `
+SELECT (extra->>'openai_long_context_billing_enabled')::boolean
+FROM accounts
+WHERE id = $1
+`, shadowID).Scan(&shadowEnabled))
+	require.False(t, shadowEnabled)
+
+	var initialShadowOutboxEvents int
+	require.NoError(t, tx.QueryRowContext(ctx, `
+SELECT COUNT(*)
+FROM scheduler_outbox
+WHERE event_type = 'account_changed' AND account_id = $1
+`, shadowID).Scan(&initialShadowOutboxEvents))
+	require.Equal(t, 1, initialShadowOutboxEvents)
+
+	var malformedLegacyEnabled bool
+	require.NoError(t, tx.QueryRowContext(ctx, `
+SELECT (extra->>'openai_long_context_billing_enabled')::boolean
+FROM accounts
+WHERE id = $1
+`, malformedLegacyID).Scan(&malformedLegacyEnabled))
+	require.False(t, malformedLegacyEnabled)
+	_, err = tx.ExecContext(ctx, `
+UPDATE accounts
+SET extra = extra || '{"migration_175_unrelated_update":true}'::jsonb
+WHERE id = $1
+`, malformedLegacyID)
+	require.NoError(t, err)
+
+	_, err = tx.ExecContext(ctx, "TRUNCATE scheduler_outbox")
+	require.NoError(t, err)
+	_, err = tx.ExecContext(ctx, `
+UPDATE accounts
+SET extra = '{"legacy_writer_replaced_extra":true}'::jsonb
+WHERE id = $1
+`, parentID)
+	require.NoError(t, err)
+	var parentEnabled bool
+	require.NoError(t, tx.QueryRowContext(ctx, `
+SELECT (extra->>'openai_long_context_billing_enabled')::boolean
+FROM accounts
+WHERE id = $1
+`, parentID).Scan(&parentEnabled))
+	require.False(t, parentEnabled)
+	require.NoError(t, tx.QueryRowContext(ctx, `
+SELECT (extra->>'openai_long_context_billing_enabled')::boolean
+FROM accounts
+WHERE id = $1
+`, shadowID).Scan(&shadowEnabled))
+	require.False(t, shadowEnabled)
+	var preservedOptOutEvents int
+	require.NoError(t, tx.QueryRowContext(ctx, `
+SELECT COUNT(*)
+FROM scheduler_outbox
+WHERE event_type = 'account_changed' AND account_id = $1
+`, shadowID).Scan(&preservedOptOutEvents))
+	require.Zero(t, preservedOptOutEvents)
+
+	require.NoError(t, tx.QueryRowContext(ctx, `
+INSERT INTO accounts (name, platform, type, extra)
+VALUES ('migration-175-rolling-writer', 'openai', 'oauth', '{}'::jsonb)
+RETURNING (extra->>'openai_long_context_billing_enabled')::boolean
+`).Scan(&ordinaryEnabled))
+	require.True(t, ordinaryEnabled)
+
+	_, err = tx.ExecContext(ctx, "TRUNCATE scheduler_outbox")
+	require.NoError(t, err)
+	_, err = tx.ExecContext(ctx, `
+UPDATE accounts
+SET extra = jsonb_set(extra, '{openai_long_context_billing_enabled}', 'true'::jsonb, true)
+WHERE id = $1
+`, parentID)
+	require.NoError(t, err)
+	require.NoError(t, tx.QueryRowContext(ctx, `
+SELECT (extra->>'openai_long_context_billing_enabled')::boolean
+FROM accounts
+WHERE id = $1
+`, shadowID).Scan(&shadowEnabled))
+	require.True(t, shadowEnabled)
+
+	var shadowOutboxEvents int
+	require.NoError(t, tx.QueryRowContext(ctx, `
+SELECT COUNT(*)
+FROM scheduler_outbox
+WHERE event_type = 'account_changed' AND account_id = $1
+`, shadowID).Scan(&shadowOutboxEvents))
+	require.Equal(t, 1, shadowOutboxEvents)
+
+	_, err = tx.ExecContext(ctx, `
+INSERT INTO accounts (name, platform, type, extra)
+VALUES ('migration-175-malformed', 'openai', 'oauth', '{"openai_long_context_billing_enabled":"false"}'::jsonb)
+`)
+	require.ErrorContains(t, err, "openai_long_context_billing_enabled must be a boolean")
+}
diff --git a/backend/internal/service/account.go b/backend/internal/service/account.go
index 27a86a60c6..0653e37bb8 100644
--- a/backend/internal/service/account.go
+++ b/backend/internal/service/account.go
@@ -83,6 +83,8 @@ type Account struct {
 
 type OpenAIEndpointCapability string
 
+const openAILongContextBillingEnabledKey = "openai_long_context_billing_enabled"
+
 const (
 	OpenAIEndpointCapabilityChatCompletions OpenAIEndpointCapability = "chat_completions"
 	OpenAIEndpointCapabilityEmbeddings      OpenAIEndpointCapability = "embeddings"
@@ -1193,10 +1195,14 @@ func (a *Account) IsOpenAI() bool {
 }
 
 func (a *Account) IsOpenAILongContextBillingEnabled() bool {
-	if a == nil || a.Extra == nil {
+	if a == nil || !a.IsOpenAI() {
 		return false
 	}
-	enabled, ok := a.Extra["openai_long_context_billing_enabled"].(bool)
+	raw, exists := a.Extra[openAILongContextBillingEnabledKey]
+	if !exists {
+		return true
+	}
+	enabled, ok := raw.(bool)
 	return ok && enabled
 }
 
diff --git a/backend/internal/service/account_long_context_billing_test.go b/backend/internal/service/account_long_context_billing_test.go
new file mode 100644
index 0000000000..712ff36de6
--- /dev/null
+++ b/backend/internal/service/account_long_context_billing_test.go
@@ -0,0 +1,290 @@
+//go:build unit
+
+package service
+
+import (
+	"context"
+	"net/http"
+	"testing"
+
+	infraerrors "github.com/Wei-Shaw/sub2api/internal/pkg/errors"
+	"github.com/stretchr/testify/require"
+)
+
+func TestAccountIsOpenAILongContextBillingEnabled(t *testing.T) {
+	tests := []struct {
+		name    string
+		account *Account
+		want    bool
+	}{
+		{name: "nil account is disabled", account: nil, want: false},
+		{name: "non OpenAI account is disabled", account: &Account{Platform: PlatformGrok}, want: false},
+		{name: "missing extra defaults enabled", account: &Account{Platform: PlatformOpenAI}, want: true},
+		{name: "missing key defaults enabled", account: &Account{Platform: PlatformOpenAI, Extra: map[string]any{}}, want: true},
+		{name: "explicit true is enabled", account: &Account{Platform: PlatformOpenAI, Extra: map[string]any{"openai_long_context_billing_enabled": true}}, want: true},
+		{name: "explicit false is disabled", account: &Account{Platform: PlatformOpenAI, Extra: map[string]any{"openai_long_context_billing_enabled": false}}, want: false},
+		{name: "malformed value is disabled", account: &Account{Platform: PlatformOpenAI, Extra: map[string]any{"openai_long_context_billing_enabled": "false"}}, want: false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			require.Equal(t, tt.want, tt.account.IsOpenAILongContextBillingEnabled())
+		})
+	}
+}
+
+func TestNormalizeOpenAILongContextBillingExtra(t *testing.T) {
+	t.Run("OpenAI missing key persists enabled default", func(t *testing.T) {
+		extra, err := normalizeOpenAILongContextBillingExtra(PlatformOpenAI, nil)
+
+		require.NoError(t, err)
+		require.Equal(t, true, extra["openai_long_context_billing_enabled"])
+	})
+
+	t.Run("OpenAI explicit false is preserved", func(t *testing.T) {
+		extra, err := normalizeOpenAILongContextBillingExtra(PlatformOpenAI, map[string]any{"openai_long_context_billing_enabled": false})
+
+		require.NoError(t, err)
+		require.Equal(t, false, extra["openai_long_context_billing_enabled"])
+	})
+
+	t.Run("OpenAI malformed value is rejected", func(t *testing.T) {
+		_, err := normalizeOpenAILongContextBillingExtra(PlatformOpenAI, map[string]any{"openai_long_context_billing_enabled": "false"})
+
+		require.Error(t, err)
+		require.Equal(t, http.StatusBadRequest, infraerrors.Code(err))
+	})
+
+	t.Run("non OpenAI extra is unchanged", func(t *testing.T) {
+		extra, err := normalizeOpenAILongContextBillingExtra(PlatformGrok, nil)
+
+		require.NoError(t, err)
+		require.Nil(t, extra)
+	})
+
+	t.Run("non OpenAI malformed value is ignored", func(t *testing.T) {
+		extra := map[string]any{openAILongContextBillingEnabledKey: "provider-owned"}
+		normalized, err := normalizeOpenAILongContextBillingExtra(PlatformAnthropic, extra)
+
+		require.NoError(t, err)
+		require.Equal(t, extra, normalized)
+	})
+}
+
+type longContextBillingRepoStub struct {
+	accountRepoStub
+	account          *Account
+	accounts         []*Account
+	createdAccount   *Account
+	updateExtraCalls int
+	bulkUpdateCalls  int
+}
+
+func (r *longContextBillingRepoStub) Create(_ context.Context, account *Account) error {
+	account.ID = 1
+	r.account = account
+	r.createdAccount = account
+	return nil
+}
+
+func (r *longContextBillingRepoStub) GetByID(_ context.Context, _ int64) (*Account, error) {
+	return r.account, nil
+}
+
+func (r *longContextBillingRepoStub) GetByIDs(_ context.Context, _ []int64) ([]*Account, error) {
+	if r.accounts != nil {
+		return r.accounts, nil
+	}
+	if r.account == nil {
+		return nil, nil
+	}
+	return []*Account{r.account}, nil
+}
+
+func (r *longContextBillingRepoStub) Update(_ context.Context, account *Account) error {
+	r.account = account
+	return nil
+}
+
+func (r *longContextBillingRepoStub) UpdateExtra(_ context.Context, _ int64, _ map[string]any) error {
+	r.updateExtraCalls++
+	return nil
+}
+
+func (r *longContextBillingRepoStub) BulkUpdate(_ context.Context, _ []int64, _ AccountBulkUpdate) (int64, error) {
+	r.bulkUpdateCalls++
+	return 1, nil
+}
+
+func TestAdminServiceCreateAccountDefaultsOpenAILongContextBillingEnabled(t *testing.T) {
+	repo := &longContextBillingRepoStub{}
+	svc := &adminServiceImpl{accountRepo: repo}
+
+	account, err := svc.CreateAccount(context.Background(), &CreateAccountInput{
+		Name:                 "openai-account",
+		Platform:             PlatformOpenAI,
+		Type:                 AccountTypeAPIKey,
+		Credentials:          map[string]any{"api_key": "test"},
+		SkipDefaultGroupBind: true,
+	})
+
+	require.NoError(t, err)
+	require.Same(t, account, repo.createdAccount)
+	require.Equal(t, true, account.Extra[openAILongContextBillingEnabledKey])
+}
+
+func TestAdminServiceCreateAccountRejectsMalformedOpenAILongContextBillingValue(t *testing.T) {
+	repo := &longContextBillingRepoStub{}
+	svc := &adminServiceImpl{accountRepo: repo}
+
+	account, err := svc.CreateAccount(context.Background(), &CreateAccountInput{
+		Platform: PlatformOpenAI,
+		Extra:    map[string]any{openAILongContextBillingEnabledKey: "false"},
+	})
+
+	require.Nil(t, account)
+	require.Equal(t, http.StatusBadRequest, infraerrors.Code(err))
+	require.Nil(t, repo.createdAccount)
+}
+
+func TestAdminServiceUpdateAccountPreservesOpenAILongContextBillingOptOutWhenOmitted(t *testing.T) {
+	repo := &longContextBillingRepoStub{account: &Account{
+		ID:       1,
+		Platform: PlatformOpenAI,
+		Type:     AccountTypeOAuth,
+		Extra:    map[string]any{openAILongContextBillingEnabledKey: false},
+	}}
+	svc := &adminServiceImpl{accountRepo: repo}
+
+	account, err := svc.UpdateAccount(context.Background(), 1, &UpdateAccountInput{Extra: map[string]any{}})
+
+	require.NoError(t, err)
+	require.Equal(t, false, account.Extra[openAILongContextBillingEnabledKey])
+}
+
+func TestAdminServiceUpdateAccountPreservesCodexImportOptOutWhenIncomingDefaultsTrue(t *testing.T) {
+	repo := &longContextBillingRepoStub{account: &Account{
+		ID:          1,
+		Platform:    PlatformOpenAI,
+		Type:        AccountTypeOAuth,
+		Credentials: map[string]any{"access_token": "old-token"},
+		Extra: map[string]any{
+			openAILongContextBillingEnabledKey: false,
+			"import_source":                    "codex_session",
+		},
+	}}
+	svc := &adminServiceImpl{accountRepo: repo}
+
+	account, err := svc.UpdateAccount(context.Background(), 1, &UpdateAccountInput{
+		Credentials: map[string]any{"access_token": "new-token"},
+		Extra: map[string]any{
+			openAILongContextBillingEnabledKey: true,
+			"import_source":                    "codex_session",
+		},
+	})
+
+	require.NoError(t, err)
+	require.Equal(t, false, account.Extra[openAILongContextBillingEnabledKey])
+}
+
+func TestAdminServiceUpdateAccountAllowsExplicitOptInOutsideCodexImport(t *testing.T) {
+	repo := &longContextBillingRepoStub{account: &Account{
+		ID:       1,
+		Platform: PlatformOpenAI,
+		Type:     AccountTypeOAuth,
+		Extra: map[string]any{
+			openAILongContextBillingEnabledKey: false,
+			"import_source":                    "codex_session",
+		},
+	}}
+	svc := &adminServiceImpl{accountRepo: repo}
+
+	account, err := svc.UpdateAccount(context.Background(), 1, &UpdateAccountInput{Extra: map[string]any{
+		openAILongContextBillingEnabledKey: true,
+		"import_source":                    "codex_session",
+	}})
+
+	require.NoError(t, err)
+	require.Equal(t, true, account.Extra[openAILongContextBillingEnabledKey])
+}
+
+func TestAdminServiceUpdateAccountRejectsMalformedOpenAILongContextBillingValue(t *testing.T) {
+	repo := &longContextBillingRepoStub{account: &Account{ID: 1, Platform: PlatformOpenAI}}
+	svc := &adminServiceImpl{accountRepo: repo}
+
+	account, err := svc.UpdateAccount(context.Background(), 1, &UpdateAccountInput{Extra: map[string]any{
+		openAILongContextBillingEnabledKey: 1,
+	}})
+
+	require.Nil(t, account)
+	require.Equal(t, http.StatusBadRequest, infraerrors.Code(err))
+}
+
+func TestAdminServiceUpdateAccountExtraRejectsMalformedOpenAILongContextBillingValue(t *testing.T) {
+	repo := &longContextBillingRepoStub{account: &Account{ID: 1, Platform: PlatformOpenAI}}
+	svc := &adminServiceImpl{accountRepo: repo}
+
+	err := svc.UpdateAccountExtra(context.Background(), 1, map[string]any{
+		openAILongContextBillingEnabledKey: "true",
+	})
+
+	require.Equal(t, http.StatusBadRequest, infraerrors.Code(err))
+	require.Zero(t, repo.updateExtraCalls)
+}
+
+func TestAdminServiceUpdateAccountExtraAllowsProviderOwnedValueForNonOpenAIAccount(t *testing.T) {
+	repo := &longContextBillingRepoStub{account: &Account{ID: 1, Platform: PlatformAnthropic}}
+	svc := &adminServiceImpl{accountRepo: repo}
+
+	err := svc.UpdateAccountExtra(context.Background(), 1, map[string]any{
+		openAILongContextBillingEnabledKey: "provider-owned",
+	})
+
+	require.NoError(t, err)
+	require.Equal(t, 1, repo.updateExtraCalls)
+}
+
+func TestAdminServiceBulkUpdateAccountsRejectsMalformedOpenAILongContextBillingValue(t *testing.T) {
+	repo := &longContextBillingRepoStub{account: &Account{ID: 1, Platform: PlatformOpenAI}}
+	svc := &adminServiceImpl{accountRepo: repo}
+
+	result, err := svc.BulkUpdateAccounts(context.Background(), &BulkUpdateAccountsInput{
+		AccountIDs: []int64{1},
+		Extra:      map[string]any{openAILongContextBillingEnabledKey: []bool{true}},
+	})
+
+	require.Nil(t, result)
+	require.Equal(t, http.StatusBadRequest, infraerrors.Code(err))
+	require.Zero(t, repo.bulkUpdateCalls)
+}
+
+func TestAdminServiceBulkUpdateAccountsAllowsProviderOwnedValueForNonOpenAIAccounts(t *testing.T) {
+	repo := &longContextBillingRepoStub{account: &Account{ID: 1, Platform: PlatformGrok}}
+	svc := &adminServiceImpl{accountRepo: repo}
+
+	result, err := svc.BulkUpdateAccounts(context.Background(), &BulkUpdateAccountsInput{
+		AccountIDs: []int64{1},
+		Extra:      map[string]any{openAILongContextBillingEnabledKey: []string{"provider-owned"}},
+	})
+
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.Equal(t, 1, repo.bulkUpdateCalls)
+}
+
+func TestAdminServiceBulkUpdateAccountsRejectsMalformedValueForMixedTargetsIncludingOpenAI(t *testing.T) {
+	repo := &longContextBillingRepoStub{accounts: []*Account{
+		{ID: 1, Platform: PlatformGrok},
+		{ID: 2, Platform: PlatformOpenAI},
+	}}
+	svc := &adminServiceImpl{accountRepo: repo}
+
+	result, err := svc.BulkUpdateAccounts(context.Background(), &BulkUpdateAccountsInput{
+		AccountIDs: []int64{1, 2},
+		Extra:      map[string]any{openAILongContextBillingEnabledKey: "malformed"},
+	})
+
+	require.Nil(t, result)
+	require.Equal(t, http.StatusBadRequest, infraerrors.Code(err))
+	require.Zero(t, repo.bulkUpdateCalls)
+}
diff --git a/backend/internal/service/admin_account.go b/backend/internal/service/admin_account.go
index 52e5ce719b..59317c3eb4 100644
--- a/backend/internal/service/admin_account.go
+++ b/backend/internal/service/admin_account.go
@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"log/slog"
+	"maps"
 	"net/http"
 	"strconv"
 	"strings"
@@ -68,7 +69,74 @@ func normalizeAccountConcurrency(platform, accountType string, concurrency int)
 	return concurrency
 }
 
+// ValidateOpenAILongContextBillingExtra validates the OpenAI account billing flag when present.
+func ValidateOpenAILongContextBillingExtra(platform string, extra map[string]any) error {
+	if platform != PlatformOpenAI {
+		return nil
+	}
+	raw, exists := extra[openAILongContextBillingEnabledKey]
+	if !exists {
+		return nil
+	}
+	if _, ok := raw.(bool); !ok {
+		return infraerrors.BadRequest(
+			"OPENAI_LONG_CONTEXT_BILLING_INVALID",
+			"openai_long_context_billing_enabled must be a boolean",
+		)
+	}
+	return nil
+}
+
+func normalizeOpenAILongContextBillingExtra(platform string, extra map[string]any) (map[string]any, error) {
+	if platform != PlatformOpenAI {
+		return extra, nil
+	}
+	if err := ValidateOpenAILongContextBillingExtra(platform, extra); err != nil {
+		return nil, err
+	}
+
+	normalized := maps.Clone(extra)
+	if normalized == nil {
+		normalized = make(map[string]any, 1)
+	}
+	_, exists := normalized[openAILongContextBillingEnabledKey]
+	if !exists {
+		normalized[openAILongContextBillingEnabledKey] = true
+	}
+	return normalized, nil
+}
+
+func normalizeOpenAILongContextBillingUpdateExtra(account *Account, input *UpdateAccountInput) (map[string]any, error) {
+	normalized, err := normalizeOpenAILongContextBillingExtra(account.Platform, input.Extra)
+	if err != nil || account.Platform != PlatformOpenAI {
+		return normalized, err
+	}
+
+	_, provided := input.Extra[openAILongContextBillingEnabledKey]
+	current, hasCurrent := account.Extra[openAILongContextBillingEnabledKey].(bool)
+	if !provided {
+		if hasCurrent {
+			normalized[openAILongContextBillingEnabledKey] = current
+		}
+		return normalized, nil
+	}
+
+	incoming := normalized[openAILongContextBillingEnabledKey].(bool)
+	importSource, _ := input.Extra["import_source"].(string)
+	accessToken, _ := input.Credentials["access_token"].(string)
+	isCodexSessionImport := importSource == "codex_session" && strings.TrimSpace(accessToken) != ""
+	if hasCurrent && !current && incoming && isCodexSessionImport {
+		normalized[openAILongContextBillingEnabledKey] = false
+	}
+	return normalized, nil
+}
+
 func (s *adminServiceImpl) CreateAccount(ctx context.Context, input *CreateAccountInput) (*Account, error) {
+	accountExtra, err := normalizeOpenAILongContextBillingExtra(input.Platform, input.Extra)
+	if err != nil {
+		return nil, err
+	}
+
 	// 绑定分组
 	groupIDs := input.GroupIDs
 	// 如果没有指定分组,自动绑定对应平台的默认分组
@@ -103,7 +171,7 @@ func (s *adminServiceImpl) CreateAccount(ctx context.Context, input *CreateAccou
 		Platform:    input.Platform,
 		Type:        input.Type,
 		Credentials: input.Credentials,
-		Extra:       input.Extra,
+		Extra:       accountExtra,
 		ProxyID:     input.ProxyID,
 		Concurrency: normalizeAccountConcurrency(input.Platform, input.Type, input.Concurrency),
 		Priority:    input.Priority,
@@ -183,6 +251,13 @@ func (s *adminServiceImpl) UpdateAccount(ctx context.Context, id int64, input *U
 	if err != nil {
 		return nil, err
 	}
+	var normalizedExtra map[string]any
+	if input.Extra != nil {
+		normalizedExtra, err = normalizeOpenAILongContextBillingUpdateExtra(account, input)
+		if err != nil {
+			return nil, err
+		}
+	}
 	// 安全/身份不变量(影子账号):通用更新路径被 edit/re-auth/refresh/batch 共用,
 	// 必须在此守住,否则仅在创建时的保证可被这些路径绕过。
 	if account.IsCredentialShadow() {
@@ -238,10 +313,10 @@ func (s *adminServiceImpl) UpdateAccount(ctx context.Context, id int64, input *U
 		// 保留配额用量字段，防止编辑账号时意外重置
 		for _, key := range []string{"quota_used", "quota_daily_used", "quota_daily_start", "quota_weekly_used", "quota_weekly_start"} {
 			if v, ok := account.Extra[key]; ok {
-				input.Extra[key] = v
+				normalizedExtra[key] = v
 			}
 		}
-		account.Extra = input.Extra
+		account.Extra = normalizedExtra
 		if account.Platform == PlatformAntigravity && wasOveragesEnabled && !account.IsOveragesEnabled() {
 			delete(account.Extra, "antigravity_credits_overages") // 清理旧版 overages 运行态
 			// 清除 AICredits 限流 key
@@ -353,6 +428,15 @@ func (s *adminServiceImpl) UpdateAccount(ctx context.Context, id int64, input *U
 // UpdateAccountExtra 仅对 Extra JSONB 做 key 级合并，避免覆盖其它运行态键
 // （如 model_rate_limits / passive_usage_* 等）。
 func (s *adminServiceImpl) UpdateAccountExtra(ctx context.Context, id int64, updates map[string]any) error {
+	if _, exists := updates[openAILongContextBillingEnabledKey]; exists {
+		account, err := s.accountRepo.GetByID(ctx, id)
+		if err != nil {
+			return err
+		}
+		if err := ValidateOpenAILongContextBillingExtra(account.Platform, updates); err != nil {
+			return err
+		}
+	}
 	if len(updates) == 0 {
 		return nil
 	}
@@ -386,16 +470,28 @@ func (s *adminServiceImpl) BulkUpdateAccounts(ctx context.Context, input *BulkUp
 	}
 
 	needMixedChannelCheck := input.GroupIDs != nil && !input.SkipMixedChannelCheck
+	_, hasLongContextBillingUpdate := input.Extra[openAILongContextBillingEnabledKey]
 
 	// 预取所有目标账号，供凭据守卫/代理守卫/混合渠道检查共用，避免多次 DB 查询。
 	var cachedTargets []*Account
-	if len(input.Credentials) > 0 || input.ProxyID != nil || needMixedChannelCheck {
+	if len(input.Credentials) > 0 || input.ProxyID != nil || needMixedChannelCheck || hasLongContextBillingUpdate {
 		loaded, err := s.accountRepo.GetByIDs(ctx, input.AccountIDs)
 		if err != nil {
 			return nil, err
 		}
 		cachedTargets = loaded
 	}
+	if hasLongContextBillingUpdate {
+		for _, account := range cachedTargets {
+			if account == nil || account.Platform != PlatformOpenAI {
+				continue
+			}
+			if err := ValidateOpenAILongContextBillingExtra(account.Platform, input.Extra); err != nil {
+				return nil, err
+			}
+			break
+		}
+	}
 
 	// 影子账号绝不持有凭据:批量更新携带凭据时,目标中不得含影子(外审 G5,与单账号
 	// UpdateAccount 守卫对齐)。覆盖显式 IDs 与 filter 解析出的 IDs(此处 AccountIDs 已解析完成)。
@@ -745,6 +841,9 @@ func (s *adminServiceImpl) CreateShadow(ctx context.Context, parentID int64, opt
 		Priority:        priority,
 		Concurrency:     concurrency,
 		Schedulable:     true,
+		Extra: map[string]any{
+			openAILongContextBillingEnabledKey: parent.IsOpenAILongContextBillingEnabled(),
+		},
 	}
 
 	// 5. 持久化（Create 填充 shadow.ID）。并发竞态:预查(步骤2)放行后另一请求抢先建成,本次会撞
diff --git a/backend/internal/service/admin_service_spark_shadow_test.go b/backend/internal/service/admin_service_spark_shadow_test.go
index 6b4017207a..7e29218f88 100644
--- a/backend/internal/service/admin_service_spark_shadow_test.go
+++ b/backend/internal/service/admin_service_spark_shadow_test.go
@@ -157,6 +157,39 @@ func TestCreateShadow(t *testing.T) {
 	require.Error(t, err)
 }
 
+func TestCreateShadowInheritsParentEffectiveOpenAILongContextBillingValue(t *testing.T) {
+	tests := []struct {
+		name        string
+		parentExtra map[string]any
+		want        bool
+	}{
+		{name: "missing parent value defaults enabled", want: true},
+		{name: "explicit parent opt-out is inherited", parentExtra: map[string]any{openAILongContextBillingEnabledKey: false}, want: false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			repo := newSparkShadowRepoStub()
+			svc := &adminServiceImpl{accountRepo: repo}
+			parent := &Account{
+				Name:        "parent",
+				Platform:    PlatformOpenAI,
+				Type:        AccountTypeOAuth,
+				Status:      StatusActive,
+				Credentials: map[string]any{"access_token": "token"},
+				Extra:       tt.parentExtra,
+			}
+			require.NoError(t, repo.Create(context.Background(), parent))
+
+			shadow, err := svc.CreateShadow(context.Background(), parent.ID, ShadowOptions{Name: "shadow"})
+
+			require.NoError(t, err)
+			require.Equal(t, tt.want, shadow.Extra[openAILongContextBillingEnabledKey])
+			require.Equal(t, tt.want, shadow.IsOpenAILongContextBillingEnabled())
+		})
+	}
+}
+
 // TestCreateShadow_BindGroups は BindGroups の後置呼び出しを検証する。
 // 影子账号が指定グループに属し、ListSchedulableByGroupID で取得可能であること。
 func TestCreateShadow_BindGroups(t *testing.T) {
diff --git a/backend/internal/service/crs_sync_long_context_billing_test.go b/backend/internal/service/crs_sync_long_context_billing_test.go
new file mode 100644
index 0000000000..876eb94e6b
--- /dev/null
+++ b/backend/internal/service/crs_sync_long_context_billing_test.go
@@ -0,0 +1,163 @@
+//go:build unit
+
+package service
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/Wei-Shaw/sub2api/internal/config"
+	"github.com/stretchr/testify/require"
+)
+
+type crsLongContextAccountRepo struct {
+	AccountRepository
+	accounts map[string]*Account
+	nextID   int64
+}
+
+type crsOpenAILongContextSource struct {
+	collection  string
+	credentials map[string]any
+	extra       map[string]any
+}
+
+func newCRSLongContextAccountRepo(existing ...*Account) *crsLongContextAccountRepo {
+	repo := &crsLongContextAccountRepo{accounts: make(map[string]*Account)}
+	for _, account := range existing {
+		if account == nil {
+			continue
+		}
+		crsID, _ := account.Extra["crs_account_id"].(string)
+		repo.accounts[crsID] = account
+		if account.ID > repo.nextID {
+			repo.nextID = account.ID
+		}
+	}
+	return repo
+}
+
+func (r *crsLongContextAccountRepo) Create(_ context.Context, account *Account) error {
+	r.nextID++
+	account.ID = r.nextID
+	crsID, _ := account.Extra["crs_account_id"].(string)
+	r.accounts[crsID] = account
+	return nil
+}
+
+func (r *crsLongContextAccountRepo) Update(_ context.Context, account *Account) error {
+	crsID, _ := account.Extra["crs_account_id"].(string)
+	r.accounts[crsID] = account
+	return nil
+}
+
+func (r *crsLongContextAccountRepo) GetByCRSAccountID(_ context.Context, crsID string) (*Account, error) {
+	return r.accounts[crsID], nil
+}
+
+func (r *crsLongContextAccountRepo) ListShadowsByParent(_ context.Context, _ int64) ([]*Account, error) {
+	return nil, nil
+}
+
+func TestCRSSyncOpenAILongContextBilling(t *testing.T) {
+	tests := []struct {
+		name          string
+		collection    string
+		credentials   map[string]any
+		sourceExtra   map[string]any
+		existingExtra map[string]any
+		wantAction    string
+		wantEnabled   bool
+	}{
+		{name: "OAuth create defaults missing value enabled", collection: "openaiOAuthAccounts", credentials: map[string]any{"access_token": "oauth-token"}, wantAction: "created", wantEnabled: true},
+		{name: "OAuth create preserves source false", collection: "openaiOAuthAccounts", credentials: map[string]any{"access_token": "oauth-token"}, sourceExtra: map[string]any{openAILongContextBillingEnabledKey: false}, wantAction: "created"},
+		{name: "OAuth update defaults missing value enabled", collection: "openaiOAuthAccounts", credentials: map[string]any{"access_token": "oauth-token"}, existingExtra: map[string]any{"existing": true}, wantAction: "updated", wantEnabled: true},
+		{name: "OAuth update preserves existing false when source omits value", collection: "openaiOAuthAccounts", credentials: map[string]any{"access_token": "oauth-token"}, existingExtra: map[string]any{openAILongContextBillingEnabledKey: false}, wantAction: "updated"},
+		{name: "OAuth update preserves source false over existing true", collection: "openaiOAuthAccounts", credentials: map[string]any{"access_token": "oauth-token"}, sourceExtra: map[string]any{openAILongContextBillingEnabledKey: false}, existingExtra: map[string]any{openAILongContextBillingEnabledKey: true}, wantAction: "updated"},
+		{name: "OAuth rejects malformed source value", collection: "openaiOAuthAccounts", credentials: map[string]any{"access_token": "oauth-token"}, sourceExtra: map[string]any{openAILongContextBillingEnabledKey: "false"}, wantAction: "failed"},
+		{name: "OAuth rejects malformed existing value", collection: "openaiOAuthAccounts", credentials: map[string]any{"access_token": "oauth-token"}, existingExtra: map[string]any{openAILongContextBillingEnabledKey: "false"}, wantAction: "failed"},
+		{name: "OAuth update rejects malformed source value", collection: "openaiOAuthAccounts", credentials: map[string]any{"access_token": "oauth-token"}, sourceExtra: map[string]any{openAILongContextBillingEnabledKey: "false"}, existingExtra: map[string]any{openAILongContextBillingEnabledKey: true}, wantAction: "failed"},
+		{name: "API key create defaults missing value enabled", collection: "openaiResponsesAccounts", credentials: map[string]any{"api_key": "sk-test"}, wantAction: "created", wantEnabled: true},
+		{name: "API key create preserves source false", collection: "openaiResponsesAccounts", credentials: map[string]any{"api_key": "sk-test"}, sourceExtra: map[string]any{openAILongContextBillingEnabledKey: false}, wantAction: "created"},
+		{name: "API key update defaults missing value enabled", collection: "openaiResponsesAccounts", credentials: map[string]any{"api_key": "sk-test"}, existingExtra: map[string]any{"existing": true}, wantAction: "updated", wantEnabled: true},
+		{name: "API key update preserves existing false when source omits value", collection: "openaiResponsesAccounts", credentials: map[string]any{"api_key": "sk-test"}, existingExtra: map[string]any{openAILongContextBillingEnabledKey: false}, wantAction: "updated"},
+		{name: "API key update preserves source false over existing true", collection: "openaiResponsesAccounts", credentials: map[string]any{"api_key": "sk-test"}, sourceExtra: map[string]any{openAILongContextBillingEnabledKey: false}, existingExtra: map[string]any{openAILongContextBillingEnabledKey: true}, wantAction: "updated"},
+		{name: "API key rejects malformed source value", collection: "openaiResponsesAccounts", credentials: map[string]any{"api_key": "sk-test"}, sourceExtra: map[string]any{openAILongContextBillingEnabledKey: "false"}, wantAction: "failed"},
+		{name: "API key rejects malformed existing value", collection: "openaiResponsesAccounts", credentials: map[string]any{"api_key": "sk-test"}, existingExtra: map[string]any{openAILongContextBillingEnabledKey: "false"}, wantAction: "failed"},
+		{name: "API key update rejects malformed source value", collection: "openaiResponsesAccounts", credentials: map[string]any{"api_key": "sk-test"}, sourceExtra: map[string]any{openAILongContextBillingEnabledKey: "false"}, existingExtra: map[string]any{openAILongContextBillingEnabledKey: true}, wantAction: "failed"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			const crsID = "crs-openai-1"
+			var existing *Account
+			if tt.existingExtra != nil {
+				existingExtra := mergeMap(tt.existingExtra, map[string]any{"crs_account_id": crsID})
+				accountType := AccountTypeOAuth
+				if tt.collection == "openaiResponsesAccounts" {
+					accountType = AccountTypeAPIKey
+				}
+				existing = &Account{ID: 41, Platform: PlatformOpenAI, Type: accountType, Extra: existingExtra}
+			}
+			repo := newCRSLongContextAccountRepo(existing)
+			result := runCRSOpenAILongContextSync(t, repo, crsOpenAILongContextSource{
+				collection:  tt.collection,
+				credentials: tt.credentials,
+				extra:       tt.sourceExtra,
+			})
+
+			require.Len(t, result.Items, 1)
+			require.Equal(t, tt.wantAction, result.Items[0].Action)
+			if tt.wantAction == "failed" {
+				require.Contains(t, result.Items[0].Error, "openai_long_context_billing_enabled must be a boolean")
+				return
+			}
+			stored, ok := repo.accounts[crsID].Extra[openAILongContextBillingEnabledKey]
+			require.True(t, ok)
+			require.Equal(t, tt.wantEnabled, stored)
+		})
+	}
+}
+
+func runCRSOpenAILongContextSync(t *testing.T, repo AccountRepository, source crsOpenAILongContextSource) *SyncFromCRSResult {
+	t.Helper()
+	account := map[string]any{
+		"kind":        "openai",
+		"id":          "crs-openai-1",
+		"name":        "OpenAI CRS",
+		"isActive":    true,
+		"schedulable": true,
+		"credentials": source.credentials,
+	}
+	if source.extra != nil {
+		account["extra"] = source.extra
+	}
+
+	server := httptest.NewServer(http.HandlerFunc(func(response http.ResponseWriter, request *http.Request) {
+		response.Header().Set("Content-Type", "application/json")
+		if request.URL.Path == "/web/auth/login" {
+			_, _ = response.Write([]byte(`{"success":true,"token":"admin-token"}`))
+			return
+		}
+		require.Equal(t, "/admin/sync/export-accounts", request.URL.Path)
+		require.NoError(t, json.NewEncoder(response).Encode(map[string]any{
+			"success": true,
+			"data":    map[string]any{source.collection: []any{account}},
+		}))
+	}))
+	t.Cleanup(server.Close)
+
+	cfg := &config.Config{}
+	cfg.Security.URLAllowlist.AllowInsecureHTTP = true
+	service := NewCRSSyncService(repo, nil, nil, nil, nil, cfg)
+	result, err := service.SyncFromCRS(context.Background(), SyncFromCRSInput{
+		BaseURL:  server.URL,
+		Username: "admin",
+		Password: "password",
+	})
+	require.NoError(t, err)
+	return result
+}
diff --git a/backend/internal/service/crs_sync_service.go b/backend/internal/service/crs_sync_service.go
index edf3cd43d2..d0abc74038 100644
--- a/backend/internal/service/crs_sync_service.go
+++ b/backend/internal/service/crs_sync_service.go
@@ -168,6 +168,7 @@ type crsOpenAIResponsesAccount struct {
 	Status      string         `json:"status"`
 	Proxy       *crsProxy      `json:"proxy"`
 	Credentials map[string]any `json:"credentials"`
+	Extra       map[string]any `json:"extra"`
 }
 
 type crsOpenAIOAuthAccount struct {
@@ -632,6 +633,18 @@ func (s *CRSSyncService) SyncFromCRS(ctx context.Context, input SyncFromCRSInput
 			result.Items = append(result.Items, item)
 			continue
 		}
+		var existingExtra map[string]any
+		if existing != nil {
+			existingExtra = existing.Extra
+		}
+		extra, err = mergeCRSOpenAILongContextBillingExtra(existingExtra, extra)
+		if err != nil {
+			item.Action = "failed"
+			item.Error = err.Error()
+			result.Failed++
+			result.Items = append(result.Items, item)
+			continue
+		}
 
 		if existing == nil {
 			if !shouldCreateAccount(src.ID, selectedSet) {
@@ -670,7 +683,7 @@ func (s *CRSSyncService) SyncFromCRS(ctx context.Context, input SyncFromCRSInput
 			continue
 		}
 
-		existing.Extra = mergeMap(existing.Extra, extra)
+		existing.Extra = extra
 		existing.Name = defaultName(src.Name, src.ID)
 		existing.Platform = PlatformOpenAI
 		existing.Type = AccountTypeOAuth
@@ -751,11 +764,13 @@ func (s *CRSSyncService) SyncFromCRS(ctx context.Context, input SyncFromCRSInput
 		concurrency := 3
 		status := mapCRSStatus(src.IsActive, src.Status)
 
-		extra := map[string]any{
-			"crs_account_id": src.ID,
-			"crs_kind":       src.Kind,
-			"crs_synced_at":  now,
+		extra := make(map[string]any, len(src.Extra)+3)
+		for key, value := range src.Extra {
+			extra[key] = value
 		}
+		extra["crs_account_id"] = src.ID
+		extra["crs_kind"] = src.Kind
+		extra["crs_synced_at"] = now
 
 		existing, err := s.accountRepo.GetByCRSAccountID(ctx, src.ID)
 		if err != nil {
@@ -765,6 +780,18 @@ func (s *CRSSyncService) SyncFromCRS(ctx context.Context, input SyncFromCRSInput
 			result.Items = append(result.Items, item)
 			continue
 		}
+		var existingExtra map[string]any
+		if existing != nil {
+			existingExtra = existing.Extra
+		}
+		extra, err = mergeCRSOpenAILongContextBillingExtra(existingExtra, extra)
+		if err != nil {
+			item.Action = "failed"
+			item.Error = err.Error()
+			result.Failed++
+			result.Items = append(result.Items, item)
+			continue
+		}
 
 		if existing == nil {
 			if !shouldCreateAccount(src.ID, selectedSet) {
@@ -809,7 +836,7 @@ func (s *CRSSyncService) SyncFromCRS(ctx context.Context, input SyncFromCRSInput
 			continue
 		}
 
-		existing.Extra = mergeMap(existing.Extra, extra)
+		existing.Extra = extra
 		existing.Name = defaultName(src.Name, src.ID)
 		existing.Platform = PlatformOpenAI
 		existing.Type = AccountTypeAPIKey
@@ -1098,6 +1125,10 @@ func mergeMap(existing map[string]any, updates map[string]any) map[string]any {
 	return out
 }
 
+func mergeCRSOpenAILongContextBillingExtra(existing, updates map[string]any) (map[string]any, error) {
+	return normalizeOpenAILongContextBillingExtra(PlatformOpenAI, mergeMap(existing, updates))
+}
+
 func (s *CRSSyncService) mapOrCreateProxy(ctx context.Context, enabled bool, cached *[]Proxy, src *crsProxy, defaultName string) (*int64, error) {
 	if !enabled || src == nil {
 		return nil, nil
diff --git a/backend/internal/service/openai_gateway_record_usage_test.go b/backend/internal/service/openai_gateway_record_usage_test.go
index c04104b903..039bfd1605 100644
--- a/backend/internal/service/openai_gateway_record_usage_test.go
+++ b/backend/internal/service/openai_gateway_record_usage_test.go
@@ -39,6 +39,17 @@ type openAIRecordUsageBillingRepoStub struct {
 	lastCtxErr error
 }
 
+type openAIRecordUsageAccountRepoStub struct {
+	AccountRepository
+	account *Account
+	calls   int
+}
+
+func (s *openAIRecordUsageAccountRepoStub) GetByID(_ context.Context, _ int64) (*Account, error) {
+	s.calls++
+	return s.account, nil
+}
+
 func (s *openAIRecordUsageBillingRepoStub) Apply(ctx context.Context, cmd *UsageBillingCommand) (*UsageBillingApplyResult, error) {
 	s.calls++
 	s.lastCmd = cmd
@@ -1045,7 +1056,7 @@ func TestOpenAIGatewayServiceRecordUsage_GPT56SeparatesCacheWriteForBillingAndSt
 	require.InDelta(t, usageRepo.lastLog.TotalCost*1.1, usageRepo.lastLog.ActualCost, 1e-12)
 }
 
-func TestOpenAIGatewayServiceRecordUsage_Gpt54LongContextBillingDisabledByDefault(t *testing.T) {
+func TestOpenAIGatewayServiceRecordUsage_Gpt54LongContextBillingEnabledByDefault(t *testing.T) {
 	usageRepo := &openAIRecordUsageLogRepoStub{inserted: true}
 	userRepo := &openAIRecordUsageUserRepoStub{}
 	subRepo := &openAIRecordUsageSubRepoStub{}
@@ -1063,44 +1074,7 @@ func TestOpenAIGatewayServiceRecordUsage_Gpt54LongContextBillingDisabledByDefaul
 		},
 		APIKey:  &APIKey{ID: 1014},
 		User:    &User{ID: 2014},
-		Account: &Account{ID: 3014},
-	})
-
-	require.NoError(t, err)
-	require.NotNil(t, usageRepo.lastLog)
-
-	expectedInput := 300000 * 2.5e-6
-	expectedOutput := 2000 * 15e-6
-	require.InDelta(t, expectedInput, usageRepo.lastLog.InputCost, 1e-10)
-	require.InDelta(t, expectedOutput, usageRepo.lastLog.OutputCost, 1e-10)
-	require.InDelta(t, expectedInput+expectedOutput, usageRepo.lastLog.TotalCost, 1e-10)
-	require.InDelta(t, (expectedInput+expectedOutput)*1.1, usageRepo.lastLog.ActualCost, 1e-10)
-	require.False(t, usageRepo.lastLog.LongContextBillingApplied)
-	require.Equal(t, 1, userRepo.deductCalls)
-}
-
-func TestOpenAIGatewayServiceRecordUsage_Gpt54LongContextBillingEnabledPerAccount(t *testing.T) {
-	usageRepo := &openAIRecordUsageLogRepoStub{inserted: true}
-	userRepo := &openAIRecordUsageUserRepoStub{}
-	subRepo := &openAIRecordUsageSubRepoStub{}
-	svc := newOpenAIRecordUsageServiceForTest(usageRepo, userRepo, subRepo, nil)
-
-	err := svc.RecordUsage(context.Background(), &OpenAIRecordUsageInput{
-		Result: &OpenAIForwardResult{
-			RequestID: "resp_gpt54_long_context_enabled",
-			Usage: OpenAIUsage{
-				InputTokens:  300000,
-				OutputTokens: 2000,
-			},
-			Model:    "gpt-5.4-2026-03-05",
-			Duration: time.Second,
-		},
-		APIKey: &APIKey{ID: 1015},
-		User:   &User{ID: 2015},
-		Account: &Account{
-			ID:    3015,
-			Extra: map[string]any{"openai_long_context_billing_enabled": true},
-		},
+		Account: &Account{ID: 3014, Platform: PlatformOpenAI},
 	})
 
 	require.NoError(t, err)
@@ -1113,6 +1087,99 @@ func TestOpenAIGatewayServiceRecordUsage_Gpt54LongContextBillingEnabledPerAccoun
 	require.InDelta(t, expectedInput+expectedOutput, usageRepo.lastLog.TotalCost, 1e-10)
 	require.InDelta(t, (expectedInput+expectedOutput)*1.1, usageRepo.lastLog.ActualCost, 1e-10)
 	require.True(t, usageRepo.lastLog.LongContextBillingApplied)
+	require.Equal(t, 1, userRepo.deductCalls)
+}
+
+func TestOpenAIGatewayServiceRecordUsage_Gpt54LongContextBillingDisabledPerAccount(t *testing.T) {
+	usageRepo := &openAIRecordUsageLogRepoStub{inserted: true}
+	userRepo := &openAIRecordUsageUserRepoStub{}
+	subRepo := &openAIRecordUsageSubRepoStub{}
+	svc := newOpenAIRecordUsageServiceForTest(usageRepo, userRepo, subRepo, nil)
+
+	err := svc.RecordUsage(context.Background(), &OpenAIRecordUsageInput{
+		Result: &OpenAIForwardResult{
+			RequestID: "resp_gpt54_long_context_disabled",
+			Usage: OpenAIUsage{
+				InputTokens:  300000,
+				OutputTokens: 2000,
+			},
+			Model:    "gpt-5.4-2026-03-05",
+			Duration: time.Second,
+		},
+		APIKey: &APIKey{ID: 1015},
+		User:   &User{ID: 2015},
+		Account: &Account{
+			ID:       3015,
+			Platform: PlatformOpenAI,
+			Extra:    map[string]any{"openai_long_context_billing_enabled": false},
+		},
+	})
+
+	require.NoError(t, err)
+	require.NotNil(t, usageRepo.lastLog)
+
+	expectedInput := 300000 * 2.5e-6
+	expectedOutput := 2000 * 15e-6
+	require.InDelta(t, expectedInput, usageRepo.lastLog.InputCost, 1e-10)
+	require.InDelta(t, expectedOutput, usageRepo.lastLog.OutputCost, 1e-10)
+	require.InDelta(t, expectedInput+expectedOutput, usageRepo.lastLog.TotalCost, 1e-10)
+	require.InDelta(t, (expectedInput+expectedOutput)*1.1, usageRepo.lastLog.ActualCost, 1e-10)
+	require.False(t, usageRepo.lastLog.LongContextBillingApplied)
+}
+
+func TestOpenAIGatewayServiceRecordUsage_SparkShadowUsesCurrentParentBillingSetting(t *testing.T) {
+	tests := []struct {
+		name          string
+		parentEnabled bool
+	}{
+		{name: "parent opt out overrides stale enabled shadow", parentEnabled: false},
+		{name: "parent opt in overrides stale disabled shadow", parentEnabled: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			usageRepo := &openAIRecordUsageLogRepoStub{inserted: true}
+			accountRepo := &openAIRecordUsageAccountRepoStub{account: &Account{
+				ID:       4016,
+				Platform: PlatformOpenAI,
+				Type:     AccountTypeOAuth,
+				Extra:    map[string]any{openAILongContextBillingEnabledKey: tt.parentEnabled},
+			}}
+			svc := newOpenAIRecordUsageServiceForTest(
+				usageRepo,
+				&openAIRecordUsageUserRepoStub{},
+				&openAIRecordUsageSubRepoStub{},
+				nil,
+			)
+			svc.accountRepo = accountRepo
+			parentID := int64(4016)
+
+			err := svc.RecordUsage(context.Background(), &OpenAIRecordUsageInput{
+				Result: &OpenAIForwardResult{
+					RequestID: "resp_gpt54_shadow_parent_setting",
+					Usage:     OpenAIUsage{InputTokens: 300000, OutputTokens: 2000},
+					Model:     "gpt-5.4-2026-03-05",
+					Duration:  time.Second,
+				},
+				APIKey: &APIKey{ID: 1016},
+				User:   &User{ID: 2016},
+				Account: &Account{
+					ID:              3016,
+					Platform:        PlatformOpenAI,
+					Type:            AccountTypeOAuth,
+					ParentAccountID: &parentID,
+					QuotaDimension:  QuotaDimensionSpark,
+					Extra: map[string]any{
+						openAILongContextBillingEnabledKey: !tt.parentEnabled,
+					},
+				},
+			})
+
+			require.NoError(t, err)
+			require.Equal(t, 1, accountRepo.calls)
+			require.Equal(t, tt.parentEnabled, usageRepo.lastLog.LongContextBillingApplied)
+		})
+	}
 }
 
 func TestOpenAIGatewayServiceRecordUsage_ServiceTierPriorityUsesFastPricing(t *testing.T) {
diff --git a/backend/internal/service/openai_gateway_usage.go b/backend/internal/service/openai_gateway_usage.go
index f030be6b46..410b4d944d 100644
--- a/backend/internal/service/openai_gateway_usage.go
+++ b/backend/internal/service/openai_gateway_usage.go
@@ -178,7 +178,14 @@ func (s *OpenAIGatewayService) RecordUsage(ctx context.Context, input *OpenAIRec
 	if result.ServiceTier != nil {
 		serviceTier = strings.TrimSpace(*result.ServiceTier)
 	}
-	longContextBillingEnabled := account.IsOpenAILongContextBillingEnabled()
+	billingAccount := account
+	if account.IsShadow() {
+		billingAccount, err = resolveCredentialAccount(ctx, s.accountRepo, account)
+		if err != nil {
+			return err
+		}
+	}
+	longContextBillingEnabled := billingAccount.IsOpenAILongContextBillingEnabled()
 	cost, err = s.calculateOpenAIRecordUsageCost(
 		ctx,
 		result,
diff --git a/backend/migrations/175_default_openai_long_context_billing.sql b/backend/migrations/175_default_openai_long_context_billing.sql
new file mode 100644
index 0000000000..48a4f74096
--- /dev/null
+++ b/backend/migrations/175_default_openai_long_context_billing.sql
@@ -0,0 +1,162 @@
+-- Keep mixed-version writers consistent before backfilling rows that already exist.
+CREATE OR REPLACE FUNCTION public.enforce_openai_long_context_billing_extra()
+RETURNS TRIGGER
+LANGUAGE plpgsql
+AS $$
+DECLARE
+    parent_effective_value JSONB;
+BEGIN
+    IF NEW.platform IS DISTINCT FROM 'openai' THEN
+        RETURN NEW;
+    END IF;
+
+    NEW.extra := COALESCE(NEW.extra, '{}'::jsonb);
+    IF NEW.parent_account_id IS NOT NULL AND NEW.quota_dimension = 'spark' THEN
+        SELECT CASE
+            WHEN parent.platform IS DISTINCT FROM 'openai' THEN 'false'::jsonb
+            WHEN NOT (COALESCE(parent.extra, '{}'::jsonb) ? 'openai_long_context_billing_enabled') THEN 'true'::jsonb
+            WHEN jsonb_typeof(parent.extra->'openai_long_context_billing_enabled') = 'boolean'
+                THEN parent.extra->'openai_long_context_billing_enabled'
+            ELSE 'false'::jsonb
+        END
+        INTO parent_effective_value
+        FROM accounts AS parent
+        WHERE parent.id = NEW.parent_account_id;
+
+        NEW.extra := jsonb_set(
+            NEW.extra,
+            '{openai_long_context_billing_enabled}',
+            COALESCE(parent_effective_value, 'false'::jsonb),
+            true
+        );
+    ELSIF NOT (NEW.extra ? 'openai_long_context_billing_enabled')
+        AND TG_OP = 'UPDATE'
+        AND OLD.platform = 'openai'
+        AND jsonb_typeof(OLD.extra->'openai_long_context_billing_enabled') = 'boolean' THEN
+        NEW.extra := jsonb_set(
+            NEW.extra,
+            '{openai_long_context_billing_enabled}',
+            OLD.extra->'openai_long_context_billing_enabled',
+            true
+        );
+    ELSIF NOT (NEW.extra ? 'openai_long_context_billing_enabled') THEN
+        NEW.extra := jsonb_set(
+            NEW.extra,
+            '{openai_long_context_billing_enabled}',
+            'true'::jsonb,
+            true
+        );
+    END IF;
+
+    IF jsonb_typeof(NEW.extra->'openai_long_context_billing_enabled') IS DISTINCT FROM 'boolean' THEN
+        RAISE EXCEPTION 'openai_long_context_billing_enabled must be a boolean'
+            USING ERRCODE = '22023';
+    END IF;
+    RETURN NEW;
+END;
+$$;
+
+CREATE OR REPLACE FUNCTION public.propagate_openai_long_context_billing_extra_to_shadows()
+RETURNS TRIGGER
+LANGUAGE plpgsql
+AS $$
+BEGIN
+    WITH updated_shadows AS (
+        UPDATE accounts AS shadow
+        SET extra = jsonb_set(
+            COALESCE(shadow.extra, '{}'::jsonb),
+            '{openai_long_context_billing_enabled}',
+            NEW.extra->'openai_long_context_billing_enabled',
+            true
+        )
+        WHERE shadow.parent_account_id = NEW.id
+          AND shadow.platform = 'openai'
+          AND shadow.quota_dimension = 'spark'
+          AND shadow.extra->'openai_long_context_billing_enabled'
+              IS DISTINCT FROM NEW.extra->'openai_long_context_billing_enabled'
+        RETURNING shadow.id
+    )
+    INSERT INTO scheduler_outbox (event_type, account_id)
+    SELECT 'account_changed', id
+    FROM updated_shadows;
+    RETURN NULL;
+END;
+$$;
+
+DROP TRIGGER IF EXISTS accounts_enforce_openai_long_context_billing_extra ON accounts;
+CREATE TRIGGER accounts_enforce_openai_long_context_billing_extra
+BEFORE INSERT OR UPDATE OF platform, extra, parent_account_id, quota_dimension
+ON accounts
+FOR EACH ROW
+EXECUTE FUNCTION public.enforce_openai_long_context_billing_extra();
+
+DROP TRIGGER IF EXISTS accounts_propagate_openai_long_context_billing_extra ON accounts;
+CREATE TRIGGER accounts_propagate_openai_long_context_billing_extra
+AFTER UPDATE OF platform, extra
+ON accounts
+FOR EACH ROW
+WHEN (
+    NEW.platform = 'openai'
+    AND NEW.parent_account_id IS NULL
+    AND (
+        OLD.platform IS DISTINCT FROM NEW.platform
+        OR OLD.extra->'openai_long_context_billing_enabled'
+            IS DISTINCT FROM NEW.extra->'openai_long_context_billing_enabled'
+    )
+)
+EXECUTE FUNCTION public.propagate_openai_long_context_billing_extra_to_shadows();
+
+UPDATE accounts
+SET extra = jsonb_set(
+    COALESCE(extra, '{}'::jsonb),
+    '{openai_long_context_billing_enabled}',
+    'false'::jsonb,
+    true
+)
+WHERE platform = 'openai'
+  AND COALESCE(extra, '{}'::jsonb) ? 'openai_long_context_billing_enabled'
+  AND jsonb_typeof(extra->'openai_long_context_billing_enabled') IS DISTINCT FROM 'boolean';
+
+UPDATE accounts
+SET extra = jsonb_set(
+    COALESCE(extra, '{}'::jsonb),
+    '{openai_long_context_billing_enabled}',
+    'true'::jsonb,
+    true
+)
+WHERE platform = 'openai'
+  AND parent_account_id IS NULL
+  AND NOT (COALESCE(extra, '{}'::jsonb) ? 'openai_long_context_billing_enabled');
+
+WITH shadow_values AS (
+    SELECT
+        shadow.id,
+        CASE
+            WHEN parent.platform IS DISTINCT FROM 'openai' THEN 'false'::jsonb
+            WHEN NOT (COALESCE(parent.extra, '{}'::jsonb) ? 'openai_long_context_billing_enabled') THEN 'true'::jsonb
+            WHEN jsonb_typeof(parent.extra->'openai_long_context_billing_enabled') = 'boolean'
+                THEN parent.extra->'openai_long_context_billing_enabled'
+            ELSE 'false'::jsonb
+        END AS effective_value
+    FROM accounts AS shadow
+    JOIN accounts AS parent ON parent.id = shadow.parent_account_id
+    WHERE shadow.platform = 'openai'
+      AND shadow.quota_dimension = 'spark'
+),
+updated_shadows AS (
+    UPDATE accounts AS shadow
+    SET extra = jsonb_set(
+        COALESCE(shadow.extra, '{}'::jsonb),
+        '{openai_long_context_billing_enabled}',
+        shadow_values.effective_value,
+        true
+    )
+    FROM shadow_values
+    WHERE shadow.id = shadow_values.id
+      AND shadow.extra->'openai_long_context_billing_enabled'
+          IS DISTINCT FROM shadow_values.effective_value
+    RETURNING shadow.id
+)
+INSERT INTO scheduler_outbox (event_type, account_id)
+SELECT 'account_changed', id
+FROM updated_shadows;
diff --git a/backend/migrations/openai_long_context_billing_migration_test.go b/backend/migrations/openai_long_context_billing_migration_test.go
new file mode 100644
index 0000000000..212ac15d9d
--- /dev/null
+++ b/backend/migrations/openai_long_context_billing_migration_test.go
@@ -0,0 +1,36 @@
+package migrations
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestMigration175DefaultsOrdinaryOpenAIAndInheritsForSparkShadows(t *testing.T) {
+	content, err := FS.ReadFile("175_default_openai_long_context_billing.sql")
+	require.NoError(t, err)
+
+	sql := string(content)
+	require.Contains(t, sql, "parent_account_id IS NULL")
+	require.Contains(t, sql, "quota_dimension = 'spark'")
+	require.Contains(t, sql, "parent.extra")
+	require.Contains(t, sql, "jsonb_typeof")
+	require.Contains(t, sql, "openai_long_context_billing_enabled")
+}
+
+func TestMigration175GuardsMixedVersionAccountWrites(t *testing.T) {
+	content, err := FS.ReadFile("175_default_openai_long_context_billing.sql")
+	require.NoError(t, err)
+
+	sql := string(content)
+	require.Contains(t, sql, "RETURNS TRIGGER")
+	require.Contains(t, sql, "BEFORE INSERT OR UPDATE")
+	require.Contains(t, sql, "CREATE TRIGGER")
+	require.Contains(t, sql, "must be a boolean")
+	require.Contains(t, sql, "INSERT INTO scheduler_outbox")
+	require.Contains(t, sql, "'account_changed'")
+	require.Contains(t, sql, "jsonb_typeof(extra->'openai_long_context_billing_enabled') IS DISTINCT FROM 'boolean'")
+	require.Contains(t, sql, "WITH shadow_values AS")
+	require.Contains(t, sql, "TG_OP = 'UPDATE'")
+	require.Contains(t, sql, "OLD.extra->'openai_long_context_billing_enabled'")
+}
diff --git a/frontend/src/components/account/CreateAccountModal.vue b/frontend/src/components/account/CreateAccountModal.vue
index 985ceaa731..0412ac8213 100644
--- a/frontend/src/components/account/CreateAccountModal.vue
+++ b/frontend/src/components/account/CreateAccountModal.vue
@@ -3708,7 +3708,7 @@ const fillHeaderOverrideTemplate = () => {
 const interceptWarmupRequests = ref(false)
 const autoPauseOnExpired = ref(true)
 const openaiPassthroughEnabled = ref(false)
-const openAILongContextBillingEnabled = ref(false)
+const openAILongContextBillingEnabled = ref(true)
 const openAICompactMode = ref<OpenAICompactMode>('auto')
 const openAIResponsesMode = ref<OpenAIResponsesMode>('auto')
 const openAIEndpointCapabilities = ref<OpenAIEndpointCapability[]>(['chat_completions', 'embeddings'])
@@ -4563,7 +4563,7 @@ const resetForm = () => {
   interceptWarmupRequests.value = false
   autoPauseOnExpired.value = true
   openaiPassthroughEnabled.value = false
-  openAILongContextBillingEnabled.value = false
+  openAILongContextBillingEnabled.value = true
   openAICompactMode.value = 'auto'
   openAIResponsesMode.value = 'auto'
   openAIEndpointCapabilities.value = ['chat_completions', 'embeddings']
@@ -4646,11 +4646,7 @@ const buildOpenAIExtra = (base?: Record<string, unknown>): Record<string, unknow
     delete extra.openai_passthrough
     delete extra.openai_oauth_passthrough
   }
-  if (openAILongContextBillingEnabled.value) {
-    extra.openai_long_context_billing_enabled = true
-  } else {
-    delete extra.openai_long_context_billing_enabled
-  }
+  extra.openai_long_context_billing_enabled = openAILongContextBillingEnabled.value
 
   if (accountCategory.value === 'oauth-based' && codexCLIOnlyEnabled.value) {
     extra.codex_cli_only = true
@@ -4686,6 +4682,15 @@ const buildOpenAIExtra = (base?: Record<string, unknown>): Record<string, unknow
   return Object.keys(extra).length > 0 ? extra : undefined
 }
 
+const buildOpenAICodexImportExtra = (): Record<string, unknown> | undefined => {
+  const extra = buildOpenAIExtra()
+  if (!extra) {
+    return undefined
+  }
+  delete extra.openai_long_context_billing_enabled
+  return Object.keys(extra).length > 0 ? extra : undefined
+}
+
 const buildAnthropicExtra = (base?: Record<string, unknown>): Record<string, unknown> | undefined => {
   if (form.platform !== 'anthropic' || accountCategory.value !== 'apikey') {
     return base
@@ -5371,7 +5376,7 @@ const handleOpenAIImportCodexSession = async (content: string) => {
   oauthClient.error.value = ''
 
   try {
-    const extra = buildOpenAIExtra()
+    const extra = buildOpenAICodexImportExtra()
     const result = await adminAPI.accounts.importCodexSession({
       content: trimmed,
       name: form.name,
@@ -5449,7 +5454,7 @@ const handleOpenAIImportCodexPAT = async (accessToken: string) => {
   oauthClient.error.value = ''
 
   try {
-    const extra = buildOpenAIExtra()
+    const extra = buildOpenAICodexImportExtra()
     await adminAPI.accounts.createOpenAICodexPAT({
       access_token: trimmed,
       name: form.name,
diff --git a/frontend/src/components/account/EditAccountModal.vue b/frontend/src/components/account/EditAccountModal.vue
index 0433997156..3dfa5c58d8 100644
--- a/frontend/src/components/account/EditAccountModal.vue
+++ b/frontend/src/components/account/EditAccountModal.vue
@@ -2794,7 +2794,7 @@ const customBaseUrl = ref('')
 
 // OpenAI 自动透传开关（OAuth/API Key）
 const openaiPassthroughEnabled = ref(false)
-const openAILongContextBillingEnabled = ref(false)
+const openAILongContextBillingEnabled = ref(true)
 const openAICompactMode = ref<OpenAICompactMode>('auto')
 const openAIResponsesMode = ref<OpenAIResponsesMode>('auto')
 const openAIEndpointCapabilities = ref<OpenAIEndpointCapability[]>(['chat_completions', 'embeddings'])
@@ -3222,7 +3222,7 @@ const syncFormFromAccount = (newAccount: Account | null) => {
 
   // Load OpenAI passthrough toggle (OpenAI OAuth/SetupToken/API Key)
   openaiPassthroughEnabled.value = false
-  openAILongContextBillingEnabled.value = false
+  openAILongContextBillingEnabled.value = true
   openAICompactMode.value = 'auto'
   openAIResponsesMode.value = 'auto'
   openAIEndpointCapabilities.value = ['chat_completions', 'embeddings']
@@ -3237,7 +3237,8 @@ const syncFormFromAccount = (newAccount: Account | null) => {
   webSearchEmulationMode.value = 'default'
   if (newAccount.platform === 'openai' && (newAccount.type === 'oauth' || newAccount.type === 'setup-token' || newAccount.type === 'apikey')) {
     openaiPassthroughEnabled.value = extra?.openai_passthrough === true || extra?.openai_oauth_passthrough === true
-    openAILongContextBillingEnabled.value = extra?.openai_long_context_billing_enabled === true
+    const longContextBillingValue = extra?.openai_long_context_billing_enabled
+    openAILongContextBillingEnabled.value = longContextBillingValue === undefined || longContextBillingValue === true
     openAICompactMode.value = (extra?.openai_compact_mode as OpenAICompactMode) || 'auto'
     if (newAccount.type === 'apikey') {
       openAIResponsesMode.value = normalizeOpenAIResponsesMode(extra?.openai_responses_mode)
diff --git a/frontend/src/components/account/__tests__/CreateAccountModal.spec.ts b/frontend/src/components/account/__tests__/CreateAccountModal.spec.ts
new file mode 100644
index 0000000000..5ff2c7d275
--- /dev/null
+++ b/frontend/src/components/account/__tests__/CreateAccountModal.spec.ts
@@ -0,0 +1,178 @@
+import { defineComponent } from 'vue'
+import { flushPromises, mount } from '@vue/test-utils'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+const {
+  createAccountMock,
+  importCodexSessionMock,
+  createOpenAICodexPATMock,
+} = vi.hoisted(() => ({
+  createAccountMock: vi.fn(),
+  importCodexSessionMock: vi.fn(),
+  createOpenAICodexPATMock: vi.fn(),
+}))
+
+vi.mock('@/stores/app', () => ({
+  useAppStore: () => ({
+    showError: vi.fn(),
+    showSuccess: vi.fn(),
+    showWarning: vi.fn(),
+  }),
+}))
+
+vi.mock('@/stores/auth', () => ({
+  useAuthStore: () => ({ isSimpleMode: true }),
+}))
+
+vi.mock('@/api/admin', () => ({
+  adminAPI: {
+    accounts: {
+      create: createAccountMock,
+      checkMixedChannelRisk: vi.fn().mockResolvedValue({ has_risk: false }),
+      importCodexSession: importCodexSessionMock,
+      createOpenAICodexPAT: createOpenAICodexPATMock,
+    },
+    settings: {
+      getWebSearchEmulationConfig: vi.fn().mockResolvedValue({ enabled: false, providers: [] }),
+      getSettings: vi.fn().mockResolvedValue({}),
+    },
+    tlsFingerprintProfiles: {
+      list: vi.fn().mockResolvedValue([]),
+    },
+  },
+}))
+
+vi.mock('@/api/admin/accounts', () => ({
+  getAntigravityDefaultModelMapping: vi.fn().mockResolvedValue([]),
+}))
+
+vi.mock('vue-i18n', async () => {
+  const actual = await vi.importActual<typeof import('vue-i18n')>('vue-i18n')
+  return {
+    ...actual,
+    useI18n: () => ({ t: (key: string) => key }),
+  }
+})
+
+import CreateAccountModal from '../CreateAccountModal.vue'
+
+const BaseDialogStub = defineComponent({
+  name: 'BaseDialog',
+  props: { show: { type: Boolean, default: false } },
+  template: '<div v-if="show"><slot /><slot name="footer" /></div>',
+})
+
+const OAuthAuthorizationFlowStub = defineComponent({
+  name: 'OAuthAuthorizationFlow',
+  emits: ['import-codex-session', 'import-codex-pat'],
+  template: `
+    <div>
+      <button data-testid="import-codex-session" @click="$emit('import-codex-session', 'session-json')">session</button>
+      <button data-testid="import-codex-pat" @click="$emit('import-codex-pat', 'pat-token')">pat</button>
+    </div>
+  `,
+})
+
+function mountModal() {
+  return mount(CreateAccountModal, {
+    props: { show: true, proxies: [], groups: [] },
+    global: {
+      stubs: {
+        BaseDialog: BaseDialogStub,
+        OAuthAuthorizationFlow: OAuthAuthorizationFlowStub,
+        ConfirmDialog: true,
+        Select: true,
+        Icon: true,
+        PlatformIcon: true,
+        ProxySelector: true,
+        ProxyAdBanner: true,
+        GroupSelector: true,
+        ModelWhitelistSelector: true,
+        QuotaLimitCard: true,
+      },
+    },
+  })
+}
+
+async function selectButtonByText(wrapper: ReturnType<typeof mountModal>, text: string) {
+  const button = wrapper.findAll('button').find((candidate) => candidate.text().includes(text))
+  expect(button).toBeDefined()
+  await button?.trigger('click')
+}
+
+async function submitApiKeyAccount(platform: 'openai' | 'anthropic', disableLongContextBilling = false) {
+  const wrapper = mountModal()
+  await selectButtonByText(wrapper, platform === 'openai' ? 'OpenAI' : 'admin.accounts.claudeConsole')
+  if (platform === 'openai') {
+    await selectButtonByText(wrapper, 'API Key')
+  }
+  await wrapper.get('form#create-account-form input[type="text"]').setValue(`${platform} account`)
+  await wrapper.get('form#create-account-form input[type="password"]').setValue('test-api-key')
+  if (disableLongContextBilling) {
+    await wrapper.get('[data-testid="openai-long-context-billing-toggle"]').trigger('click')
+  }
+  await wrapper.get('form#create-account-form').trigger('submit.prevent')
+  await flushPromises()
+}
+
+async function openCodexImportStep() {
+  const wrapper = mountModal()
+  await selectButtonByText(wrapper, 'OpenAI')
+  await wrapper.get('form#create-account-form input[type="text"]').setValue('Codex import')
+  await wrapper.get('form#create-account-form').trigger('submit.prevent')
+  return wrapper
+}
+
+describe('CreateAccountModal OpenAI long-context billing', () => {
+  beforeEach(() => {
+    createAccountMock.mockReset().mockResolvedValue({})
+    importCodexSessionMock.mockReset().mockResolvedValue({
+      created: 1,
+      updated: 0,
+      skipped: 0,
+      failed: 0,
+      errors: [],
+      warnings: [],
+    })
+    createOpenAICodexPATMock.mockReset().mockResolvedValue({})
+  })
+
+  it('sends true explicitly for normal OpenAI account creation by default', async () => {
+    await submitApiKeyAccount('openai')
+
+    expect(createAccountMock).toHaveBeenCalledTimes(1)
+    expect(createAccountMock.mock.calls[0]?.[0]?.extra?.openai_long_context_billing_enabled).toBe(true)
+  })
+
+  it('sends false explicitly when OpenAI long-context billing is disabled', async () => {
+    await submitApiKeyAccount('openai', true)
+
+    expect(createAccountMock).toHaveBeenCalledTimes(1)
+    expect(createAccountMock.mock.calls[0]?.[0]?.extra?.openai_long_context_billing_enabled).toBe(false)
+  })
+
+  it('omits the OpenAI setting for non-OpenAI account creation', async () => {
+    await submitApiKeyAccount('anthropic')
+
+    expect(createAccountMock).toHaveBeenCalledTimes(1)
+    expect(createAccountMock.mock.calls[0]?.[0]?.extra?.openai_long_context_billing_enabled).toBeUndefined()
+  })
+
+  it('leaves Codex session import billing ownership to the backend', async () => {
+    const wrapper = await openCodexImportStep()
+    await wrapper.get('[data-testid="import-codex-session"]').trigger('click')
+    await flushPromises()
+
+    expect(importCodexSessionMock).toHaveBeenCalledTimes(1)
+    expect(importCodexSessionMock.mock.calls[0]?.[0]?.extra?.openai_long_context_billing_enabled).toBeUndefined()
+  })
+
+  it('leaves Codex PAT import billing ownership to the backend', async () => {
+    const wrapper = await openCodexImportStep()
+    await wrapper.get('[data-testid="import-codex-pat"]').trigger('click')
+    await flushPromises()
+
+    expect(createOpenAICodexPATMock).toHaveBeenCalledTimes(1)
+    expect(createOpenAICodexPATMock.mock.calls[0]?.[0]?.extra?.openai_long_context_billing_enabled).toBeUndefined()
+  })
+})
diff --git a/frontend/src/components/account/__tests__/EditAccountModal.spec.ts b/frontend/src/components/account/__tests__/EditAccountModal.spec.ts
index 7ae9afc2e5..d50912e9a9 100644
--- a/frontend/src/components/account/__tests__/EditAccountModal.spec.ts
+++ b/frontend/src/components/account/__tests__/EditAccountModal.spec.ts
@@ -416,6 +416,63 @@ describe('EditAccountModal', () => {
     expect(updateAccountMock.mock.calls[0]?.[1]?.extra?.openai_long_context_billing_enabled).toBe(false)
   })
 
+  it('defaults legacy OpenAI accounts to long-context billing enabled', async () => {
+    const account = buildAccount()
+    updateAccountMock.mockReset()
+    checkMixedChannelRiskMock.mockReset()
+    checkMixedChannelRiskMock.mockResolvedValue({ has_risk: false })
+    updateAccountMock.mockResolvedValue(account)
+
+    const wrapper = mountModal(account)
+    const toggle = wrapper.get('[data-testid="openai-long-context-billing-toggle"]')
+    expect(toggle.attributes('aria-checked')).toBe('true')
+
+    await wrapper.get('form#edit-account-form').trigger('submit.prevent')
+
+    expect(updateAccountMock).toHaveBeenCalledTimes(1)
+    expect(updateAccountMock.mock.calls[0]?.[1]?.extra?.openai_long_context_billing_enabled).toBe(true)
+  })
+
+  it('preserves an explicit OpenAI long-context billing opt-out', async () => {
+    const account = buildAccount()
+    account.extra = {
+      openai_long_context_billing_enabled: false
+    }
+    updateAccountMock.mockReset()
+    checkMixedChannelRiskMock.mockReset()
+    checkMixedChannelRiskMock.mockResolvedValue({ has_risk: false })
+    updateAccountMock.mockResolvedValue(account)
+
+    const wrapper = mountModal(account)
+    const toggle = wrapper.get('[data-testid="openai-long-context-billing-toggle"]')
+    expect(toggle.attributes('aria-checked')).toBe('false')
+
+    await wrapper.get('form#edit-account-form').trigger('submit.prevent')
+
+    expect(updateAccountMock).toHaveBeenCalledTimes(1)
+    expect(updateAccountMock.mock.calls[0]?.[1]?.extra?.openai_long_context_billing_enabled).toBe(false)
+  })
+
+  it('fails closed for malformed OpenAI long-context billing values', async () => {
+    const account = buildAccount()
+    account.extra = {
+      openai_long_context_billing_enabled: 'false'
+    }
+    updateAccountMock.mockReset()
+    checkMixedChannelRiskMock.mockReset()
+    checkMixedChannelRiskMock.mockResolvedValue({ has_risk: false })
+    updateAccountMock.mockResolvedValue(account)
+
+    const wrapper = mountModal(account)
+
+    expect(wrapper.get('[data-testid="openai-long-context-billing-toggle"]').attributes('aria-checked')).toBe('false')
+
+    await wrapper.get('form#edit-account-form').trigger('submit.prevent')
+
+    expect(updateAccountMock).toHaveBeenCalledTimes(1)
+    expect(updateAccountMock.mock.calls[0]?.[1]?.extra?.openai_long_context_billing_enabled).toBe(false)
+  })
+
   it('loads and submits Grok OAuth model mapping edits', async () => {
     const account = buildGrokOAuthAccount()
     updateAccountMock.mockReset()
diff --git a/frontend/src/i18n/locales/en/admin/accounts.ts b/frontend/src/i18n/locales/en/admin/accounts.ts
index f6d0125a17..6842e29eba 100644
--- a/frontend/src/i18n/locales/en/admin/accounts.ts
+++ b/frontend/src/i18n/locales/en/admin/accounts.ts
@@ -404,7 +404,7 @@ export default {
           'When enabled, this OpenAI account uses automatic passthrough: the gateway forwards request/response as-is and only swaps auth, while keeping billing/concurrency/audit and necessary safety filtering.',
         longContextBilling: 'API long-context pricing',
         longContextBillingDesc:
-          'Disabled by default. Enable only when this account\'s upstream charges OpenAI API long-context rates above the model threshold.',
+          'Enabled by default. Disable only when this account\'s upstream does not charge OpenAI API long-context rates above the model threshold.',
         responsesWebsocketsV2: 'Responses WebSocket v2',
         responsesWebsocketsV2Desc:
           'Disabled by default. Enable to allow responses_websockets_v2 capability (still gated by global and account-type switches).',
diff --git a/frontend/src/i18n/locales/zh/admin/accounts.ts b/frontend/src/i18n/locales/zh/admin/accounts.ts
index 393efce57a..380f793246 100644
--- a/frontend/src/i18n/locales/zh/admin/accounts.ts
+++ b/frontend/src/i18n/locales/zh/admin/accounts.ts
@@ -506,7 +506,7 @@ export default {
         oauthPassthroughDesc:
           '开启后，该 OpenAI 账号将自动透传请求与响应，仅替换认证并保留计费/并发/审计及必要安全过滤；如遇兼容性问题可随时关闭回滚。',
         longContextBilling: 'API 长上下文计费',
-        longContextBillingDesc: '默认关闭。仅当该账号的上游会按模型阈值收取 OpenAI API 长上下文费率时启用。',
+        longContextBillingDesc: '默认开启。仅当该账号的上游不会按模型阈值收取 OpenAI API 长上下文费率时关闭。',
         responsesWebsocketsV2: 'Responses WebSocket v2',
         responsesWebsocketsV2Desc:
           '默认关闭。开启后可启用 responses_websockets_v2 协议能力（受网关全局开关与账号类型开关约束）。',