diff --git a/.ai/architecture.md b/.ai/architecture.md
index 6adccfb..2dc1b5f 100644
--- a/.ai/architecture.md
+++ b/.ai/architecture.md
@@ -160,10 +160,11 @@ HTTP/e2e naming и расположение — в [Testing](conventions/testing
 
 `*.module.ts` задаёт DI boundary; `*.api.ts` перечисляет используемые другими
 модулями providers, функции и типы. Внешний production import идёт через этот
-API или файл Nest module. Чистые `integrations/tbank/decimal.ts` и
+API или файл Nest module. Чистые `integrations/tbank/decimal.ts`,
+`integrations/tbank/tbank-protocol.ts`, `integrations/tbank/tbank-error-code.ts` и
 `modules/investments/operations/domain/operations-sync-plan.ts` — отдельные
-публичные входы для protobuf conversion и interval rules: импорт расчётов
-не загружает DI/Prisma.
+публичные входы для protobuf conversion, protocol/error vocabulary и interval
+rules: импорт этих значений и расчётов не загружает DI/Prisma.
 Внутри модуля используй прямые локальные импорты.
 Tests могут импортировать внутренний owner для проверки поведения и mocks.
 Новый export требует текущего потребителя; controller и persistence остаются
@@ -251,7 +252,12 @@ OpenAPI enum metadata и runtime validation должны читать тот ж
 Исключения для индексов, default values, enum/type declarations и readonly
 properties заданы в ESLint config. Test fixtures/expected values остаются inline,
 остальные lint правила продолжают действовать. Numeric policy получает предметное имя и единицы;
-semantic magic strings проверяются conventions/review без нового инструмента.
+Machine codes и protocol values задаются строковыми enum у владельца.
+`no-restricted-syntax` запрещает inline-коды и значения известных protocol families
+в production TS; `no-unsafe-enum-comparison` проверяет сравнения enum.
+Внешние открытые строки проверяются на boundary без cast и без потери unknown fallback.
+Tests сохраняют независимые literal wire assertions; обычный текст и env keys
+не считаются кодами. Новые словари требуют проверки владельца и расширения selectors.
 
 ## Logging
 
diff --git a/.ai/conventions/engineering.md b/.ai/conventions/engineering.md
index 98f5a1b..b100e4f 100644
--- a/.ai/conventions/engineering.md
+++ b/.ai/conventions/engineering.md
@@ -29,7 +29,8 @@ owner и 1–3 примера. Код показывает механизм; с
 ## Domain values
 
 Finite business vocabulary принадлежит одному domain/module/entity owner.
-Переиспользуй его symbols; для нового словаря без аналога — `as const` + union.
+Переиспользуй его symbols; для machine codes и protocol values используй
+строковые `enum`, для структуры с разными payload — discriminated union.
 Сохраняй wire values; generated/external enums не переписывай вручную.
 Numeric policy называй по смыслу и единицам. Индексы, `Math.max(value, 0)` и
 обычные labels не выноси в constants без semantic benefit.
diff --git a/.ai/conventions/integrations.md b/.ai/conventions/integrations.md
index d742ab0..9b5f4d5 100644
--- a/.ai/conventions/integrations.md
+++ b/.ai/conventions/integrations.md
@@ -22,7 +22,9 @@ RPC, credentials/access и resilience. Эти владельцы не объед
 
 Преобразование provider records происходит на boundary: например,
 `tbank-portfolio.mapper.ts` и `bond-money.mapper.ts`; protobuf decimal helper
-остаётся отдельным чистым входом integration. Domain получает внутренние
+остаётся отдельным чистым входом integration. `tbank-protocol.ts` и
+`tbank-error-code.ts` также импортируются напрямую: их enums и guards
+не должны загружать DI/Prisma через service exports. Domain получает внутренние
 значения и не импортирует gRPC/SDK types. Не добавляй новый adapter на каждый
 client или mapper для простого копирования полей. Даты/units/nano разбираются
 на границе клиента/его mapping, а не становятся моделью чистых расчётов.
diff --git a/eslint.config.mjs b/eslint.config.mjs
index d5955f1..1e01eab 100644
--- a/eslint.config.mjs
+++ b/eslint.config.mjs
@@ -107,4 +107,47 @@ export default defineConfig(
       'jest/expect-expect': ['error', { assertFunctionNames: ['expect', '**.expect'] }],
     },
   },
+  {
+    files: [
+      'src/**/*.ts',
+    ],
+    ignores: [
+      '**/*.spec.ts',
+      'test/**/*.ts',
+    ],
+    rules: {
+      'no-restricted-syntax': [
+        'error',
+        {
+          selector: 'Literal[value=/^(?:(?:INSTRUMENT_ID_TYPE|INSTRUMENT_TYPE|OPERATION_STATE|OPERATION_TYPE|ACCOUNT_STATUS|ACCOUNT_TYPE|CANDLE_INTERVAL|COUPON_TYPE|BANK|INVALID)_[A-Z0-9]+(?:_[A-Z0-9]+)*|[A-Z][A-Z0-9_]*_(?:ERROR|UNAVAILABLE|NOT_FOUND|NOT_CONNECTED|CONFLICT|AMBIGUOUS|REGISTERED)|P[0-9]{4}|UNAUTHORIZED|FORBIDDEN|BAD_REQUEST|NOT_FOUND|UNSUPPORTED_MEDIA_TYPE)$/]:not(TSEnumMember > Literal)',
+          message: 'Use the owning enum member for machine codes and protocol values.',
+        },
+        {
+          selector: 'TemplateElement[value.cooked=/^(?:(?:INSTRUMENT_ID_TYPE|INSTRUMENT_TYPE|OPERATION_STATE|OPERATION_TYPE|ACCOUNT_STATUS|ACCOUNT_TYPE|CANDLE_INTERVAL|COUPON_TYPE|BANK|INVALID)_[A-Z0-9]+(?:_[A-Z0-9]+)*|[A-Z][A-Z0-9_]*_(?:ERROR|UNAVAILABLE|NOT_FOUND|NOT_CONNECTED|CONFLICT|AMBIGUOUS|REGISTERED)|P[0-9]{4}|UNAUTHORIZED|FORBIDDEN|BAD_REQUEST|NOT_FOUND|UNSUPPORTED_MEDIA_TYPE)$/]:not(TSEnumMember TemplateElement)',
+          message: 'Use the owning enum member instead of a template machine code.',
+        },
+        {
+          selector: 'Property:matches([key.name=/^(code|errorCode|idType|instrumentKind)$/], [key.value=/^(code|errorCode|idType|instrumentKind)$/]) > Literal.value[value=type(string)]',
+          message: 'Use an enum member instead of an inline code or protocol value.',
+        },
+        {
+          selector: 'Property:matches([key.name=/^(code|errorCode|idType|instrumentKind)$/], [key.value=/^(code|errorCode|idType|instrumentKind)$/]) > TemplateLiteral.value',
+          message: 'Use an enum member instead of constructing a code or protocol value.',
+        },
+        {
+          selector: 'Property[computed=false][key.name=/^(OPERATION_TYPE|ACCOUNT_TYPE)_/]',
+          message: 'Use a computed enum member as the protocol mapping key.',
+        },
+        {
+          selector: 'BinaryExpression:has(> :matches(MemberExpression[property.name=/^(code|errorCode)$/], Identifier[name=/^(code|errorCode)$/])) > Literal[value=type(string)]',
+          message: 'Compare codes with their enum members, not string literals.',
+        },
+        {
+          selector: 'PropertyDefinition[definite=true], VariableDeclarator[definite=true]',
+          message: 'Definite assignment assertions are forbidden. Initialize owned values; use declare only for externally populated DTO fields.',
+        },
+      ],
+      '@typescript-eslint/no-unsafe-enum-comparison': 'error',
+    },
+  },
 );
diff --git a/src/common/decorators/api-safe-error-response.decorator.ts b/src/common/decorators/api-safe-error-response.decorator.ts
index 81300b4..1c2ec64 100644
--- a/src/common/decorators/api-safe-error-response.decorator.ts
+++ b/src/common/decorators/api-safe-error-response.decorator.ts
@@ -7,11 +7,13 @@ import {
   getSchemaPath,
 } from '@nestjs/swagger';
 
+import { HttpErrorCode } from '../error-code';
+
 export class ProblemDetailsDto {
   @ApiProperty({ example: 401 })
   declare status: number;
 
-  @ApiProperty({ example: 'UNAUTHORIZED' })
+  @ApiProperty({ example: HttpErrorCode.Unauthorized })
   declare code: string;
 
   // eslint-disable-next-line @darraghor/nestjs-typed/api-property-returning-array-should-set-array -- Raw OpenAPI items schema already declares type: array.
diff --git a/src/common/error-code.ts b/src/common/error-code.ts
new file mode 100644
index 0000000..db48c8a
--- /dev/null
+++ b/src/common/error-code.ts
@@ -0,0 +1,8 @@
+export enum HttpErrorCode {
+  BadRequest = 'BAD_REQUEST',
+  InternalServerError = 'INTERNAL_SERVER_ERROR',
+  NotFound = 'NOT_FOUND',
+  Unauthorized = 'UNAUTHORIZED',
+  UnsupportedMediaType = 'UNSUPPORTED_MEDIA_TYPE',
+  ValidationError = 'VALIDATION_ERROR',
+}
diff --git a/src/common/filters/http-exception.filter.ts b/src/common/filters/http-exception.filter.ts
index e228b30..2130736 100644
--- a/src/common/filters/http-exception.filter.ts
+++ b/src/common/filters/http-exception.filter.ts
@@ -9,6 +9,8 @@ import {
   ValidationError,
 } from '@nestjs/common';
 
+import { HttpErrorCode } from '../error-code';
+
 @Catch()
 export class HttpExceptionFilter implements ExceptionFilter {
   catch(exception: unknown, host: ArgumentsHost): void {
@@ -25,7 +27,7 @@ export class HttpExceptionFilter implements ExceptionFilter {
       (payload as { message?: unknown })?.message,
     );
     const code = isValidation
-      ? 'VALIDATION_ERROR'
+      ? HttpErrorCode.ValidationError
       : this.codeFor(status, payload);
     response.locals ??= {};
     response.locals.publicErrorCode = code;
@@ -53,12 +55,12 @@ export class HttpExceptionFilter implements ExceptionFilter {
     return (
       // eslint-disable-next-line security/detect-object-injection -- The lookup key is a numeric HTTP status, never a property name from the request.
       {
-        400: 'BAD_REQUEST',
-        401: 'UNAUTHORIZED',
-        404: 'NOT_FOUND',
-        415: 'UNSUPPORTED_MEDIA_TYPE',
-        500: 'INTERNAL_SERVER_ERROR',
-      }[status] ?? 'INTERNAL_SERVER_ERROR'
+        400: HttpErrorCode.BadRequest,
+        401: HttpErrorCode.Unauthorized,
+        404: HttpErrorCode.NotFound,
+        415: HttpErrorCode.UnsupportedMediaType,
+        500: HttpErrorCode.InternalServerError,
+      }[status] ?? HttpErrorCode.InternalServerError
     );
   }
 
diff --git a/src/integrations/moex/moex.client.ts b/src/integrations/moex/moex.client.ts
index 5b5d561..61f1f0e 100644
--- a/src/integrations/moex/moex.client.ts
+++ b/src/integrations/moex/moex.client.ts
@@ -1,6 +1,8 @@
 import { Injectable, ServiceUnavailableException } from '@nestjs/common';
 import { constants as httpStatus } from 'node:http2';
 
+enum MoexErrorCode { Unavailable = 'MOEX_UNAVAILABLE' }
+
 const MIN_PRICE_PERCENT_EXCLUSIVE = 0;
 const FIRST_PAGE_OFFSET = 0;
 const EXPECTED_CURSOR_ROWS = 1;
@@ -152,7 +154,7 @@ export class MoexClient {
         pageSize === EMPTY_PAGE_SIZE ||
         current.length !== Math.min(pageSize, total - start)
       ) {
-        throw new ServiceUnavailableException({ code: 'MOEX_UNAVAILABLE' });
+        throw new ServiceUnavailableException({ code: MoexErrorCode.Unavailable });
       }
       if (index + pageSize >= total) return rows;
       start = index + pageSize;
@@ -172,22 +174,22 @@ export class MoexClient {
       }
       return body as IssResponse;
     } catch {
-      throw new ServiceUnavailableException({ code: 'MOEX_UNAVAILABLE' });
+      throw new ServiceUnavailableException({ code: MoexErrorCode.Unavailable });
     }
   }
 }
 
 function parseRows(block: IssBlock | undefined): Record<string, unknown>[] {
   if (!Array.isArray(block?.columns) || !Array.isArray(block?.data)) {
-    throw new ServiceUnavailableException({ code: 'MOEX_UNAVAILABLE' });
+    throw new ServiceUnavailableException({ code: MoexErrorCode.Unavailable });
   }
   const columns = block.columns;
   if (!columns.every((column) => typeof column === 'string')) {
-    throw new ServiceUnavailableException({ code: 'MOEX_UNAVAILABLE' });
+    throw new ServiceUnavailableException({ code: MoexErrorCode.Unavailable });
   }
   return block.data.map((values) => {
     if (!Array.isArray(values) || values.length !== columns.length) {
-      throw new ServiceUnavailableException({ code: 'MOEX_UNAVAILABLE' });
+      throw new ServiceUnavailableException({ code: MoexErrorCode.Unavailable });
     }
     return Object.fromEntries(
       // eslint-disable-next-line security/detect-object-injection -- Keys are fixed MOEX block names; row indexes come from the validated columns array.
diff --git a/src/integrations/ncr/ncr-ratings.client.ts b/src/integrations/ncr/ncr-ratings.client.ts
index 257b58d..a5f110e 100644
--- a/src/integrations/ncr/ncr-ratings.client.ts
+++ b/src/integrations/ncr/ncr-ratings.client.ts
@@ -4,6 +4,8 @@ import { LRUCache } from 'lru-cache';
 
 import { ISO_DATE_LENGTH, ISO_DATE_START } from '../../common/time';
 
+enum NcrErrorCode { Unavailable = 'NCR_UNAVAILABLE' }
+
 const EXPECTED_REGISTRY_TABLES = 1;
 const RATING_COLUMN = 2;
 
@@ -41,7 +43,7 @@ export class NcrRatingsClient {
         if (this.cache.get('registry') === pending) {
           this.cache.set('registry', pending, { ttl: 60_000 });
         }
-        throw new ServiceUnavailableException({ code: 'NCR_UNAVAILABLE' });
+        throw new ServiceUnavailableException({ code: NcrErrorCode.Unavailable });
       });
       this.cache.set('registry', pending);
     }
diff --git a/src/integrations/tbank/instrument-metadata.repository.ts b/src/integrations/tbank/instrument-metadata.repository.ts
index 7fc6819..4e8933f 100644
--- a/src/integrations/tbank/instrument-metadata.repository.ts
+++ b/src/integrations/tbank/instrument-metadata.repository.ts
@@ -11,6 +11,7 @@ import type { TbankSyncAttempt } from './tbank-access.service';
 import type { TbankInstrument } from './tbank.client';
 
 import { PrismaService } from '../../prisma/prisma.service';
+import { TbankErrorCode } from './tbank-error-code';
 import { tbankSourceTtlMs } from './tbank-source.policy';
 
 const FIRST_BATCH_OFFSET = 0;
@@ -276,7 +277,7 @@ export class InstrumentMetadataRepository {
       },
       data: {
         state: success ? 'complete' : 'failed',
-        errorCode: success ? null : 'TBANK_UNAVAILABLE',
+        errorCode: success ? null : TbankErrorCode.Unavailable,
       },
     });
     if (success) {
@@ -286,7 +287,7 @@ export class InstrumentMetadataRepository {
           state: 'running',
           connection: { invalidToken: true },
         },
-        data: { state: 'failed', errorCode: 'INVALID_TBANK_TOKEN' },
+        data: { state: 'failed', errorCode: TbankErrorCode.InvalidToken },
       });
     }
   }
diff --git a/src/integrations/tbank/instrument-metadata.service.ts b/src/integrations/tbank/instrument-metadata.service.ts
index ee3c4a9..9dfb08a 100644
--- a/src/integrations/tbank/instrument-metadata.service.ts
+++ b/src/integrations/tbank/instrument-metadata.service.ts
@@ -12,6 +12,7 @@ import {
   TbankAccessService,
   type TbankSyncAttempt,
 } from './tbank-access.service';
+import { isTbankErrorCode, TbankErrorCode } from './tbank-error-code';
 import { TbankClient, type TbankInstrument } from './tbank.client';
 export { metadataKey } from './instrument-metadata.repository';
 export type { MetadataIdentity } from './instrument-metadata.repository';
@@ -131,7 +132,7 @@ export class InstrumentMetadataService {
                 if (
                   !identity.figi ||
                   (error instanceof Error &&
-                    error.message === 'INVALID_TBANK_TOKEN')
+                    isTbankErrorCode(error.message, TbankErrorCode.InvalidToken))
                 ) {
                   throw error;
                 }
@@ -191,11 +192,11 @@ export class InstrumentMetadataService {
             );
           }
         } catch (error) {
-          if (error instanceof Error && error.message === 'INVALID_TBANK_TOKEN') {
+          if (error instanceof Error && isTbankErrorCode(error.message, TbankErrorCode.InvalidToken)) {
             await this.access.rejectMembershipToken(attempt);
           } else {
             this.logger.event('warn', 'instrument-metadata.failed', {
-              code: 'TBANK_UNAVAILABLE',
+              code: TbankErrorCode.Unavailable,
             });
           }
         }
@@ -209,7 +210,7 @@ export class InstrumentMetadataService {
       }
     } catch {
       this.logger.event('error', 'instrument-metadata.persistence-failed', {
-        code: 'TBANK_UNAVAILABLE',
+        code: TbankErrorCode.Unavailable,
       });
       this.active.clear();
       this.producers.clear();
diff --git a/src/integrations/tbank/tbank-access.service.ts b/src/integrations/tbank/tbank-access.service.ts
index 588c9cb..eed498a 100644
--- a/src/integrations/tbank/tbank-access.service.ts
+++ b/src/integrations/tbank/tbank-access.service.ts
@@ -10,6 +10,7 @@ import type { TbankAccount } from './tbank.client';
 
 import { PrismaService } from '../../prisma/prisma.service';
 import { supportedTbankAccounts } from './tbank-account.policy';
+import { TbankErrorCode } from './tbank-error-code';
 import { tbankSourceNeedsRefresh } from './tbank-source.policy';
 import { TbankTokenService } from './tbank-token.service';
 
@@ -103,7 +104,7 @@ export class TbankAccessService {
         state: 'running',
         connection: { invalidToken: false },
       },
-      data: { state: 'failed', errorCode: 'TBANK_UNAVAILABLE' },
+      data: { state: 'failed', errorCode: TbankErrorCode.Unavailable },
     });
     return result.count === EXPECTED_UPDATED_CONNECTIONS;
   }
@@ -205,7 +206,7 @@ export class TbankAccessService {
     return this.prisma.$transaction(async (tx) => {
       const claimed = await tx.tbankSyncWork.updateMany({
         where: { ...attempt, state: 'running' },
-        data: { state: 'failed', errorCode: 'INVALID_TBANK_TOKEN' },
+        data: { state: 'failed', errorCode: TbankErrorCode.InvalidToken },
       });
       if (!claimed.count) return false;
       await tx.tbankConnection.update({
@@ -236,10 +237,10 @@ export class TbankAccessService {
       },
     });
     if (!connection) {
-      throw new ConflictException({ code: 'TBANK_NOT_CONNECTED' });
+      throw new ConflictException({ code: TbankErrorCode.NotConnected });
     }
     if (connection.invalidToken) {
-      throw new BadRequestException({ code: 'INVALID_TBANK_TOKEN' });
+      throw new BadRequestException({ code: TbankErrorCode.InvalidToken });
     }
     if (
       connection.membershipAt &&
diff --git a/src/integrations/tbank/tbank-account.policy.ts b/src/integrations/tbank/tbank-account.policy.ts
index eb456e2..816ae98 100644
--- a/src/integrations/tbank/tbank-account.policy.ts
+++ b/src/integrations/tbank/tbank-account.policy.ts
@@ -1,14 +1,15 @@
 import { ISO_DATE_LENGTH, ISO_DATE_START, MILLISECONDS_PER_SECOND } from '../../common/time';
+import { TbankAccountType } from './tbank-protocol';
 import { TbankAccount } from './tbank.client';
 
 const accountTypes = {
-  ACCOUNT_TYPE_TINKOFF: { type: 'BROKERAGE', name: 'Брокерский счет' },
-  ACCOUNT_TYPE_TINKOFF_IIS: {
+  [TbankAccountType.Tinkoff]: { type: 'BROKERAGE', name: 'Брокерский счет' },
+  [TbankAccountType.TinkoffIis]: {
     type: 'INDIVIDUAL_INVESTMENT',
     name: 'ИИС',
   },
-  ACCOUNT_TYPE_INVEST_BOX: { type: 'INVEST_BOX', name: 'Инвесткопилка' },
-  ACCOUNT_TYPE_INVEST_FUND: {
+  [TbankAccountType.InvestBox]: { type: 'INVEST_BOX', name: 'Инвесткопилка' },
+  [TbankAccountType.InvestFund]: {
     type: 'MONEY_MARKET_FUND',
     name: 'Фонд денежного рынка',
   },
diff --git a/src/integrations/tbank/tbank-error-code.ts b/src/integrations/tbank/tbank-error-code.ts
new file mode 100644
index 0000000..f74ecb0
--- /dev/null
+++ b/src/integrations/tbank/tbank-error-code.ts
@@ -0,0 +1,10 @@
+export enum TbankErrorCode {
+  InvalidToken = 'INVALID_TBANK_TOKEN',
+  NotConnected = 'TBANK_NOT_CONNECTED',
+  Unavailable = 'TBANK_UNAVAILABLE',
+}
+
+// Error messages and persisted codes cross an open string boundary.
+export function isTbankErrorCode(value: unknown, expected: TbankErrorCode): boolean {
+  return value === expected;
+}
diff --git a/src/integrations/tbank/tbank-membership.service.ts b/src/integrations/tbank/tbank-membership.service.ts
index 784c3cc..625372d 100644
--- a/src/integrations/tbank/tbank-membership.service.ts
+++ b/src/integrations/tbank/tbank-membership.service.ts
@@ -6,6 +6,7 @@ import {
   TbankAccessService,
   type TbankSyncAttempt,
 } from './tbank-access.service';
+import { isTbankErrorCode, TbankErrorCode } from './tbank-error-code';
 import { TbankClient } from './tbank.client';
 
 @Injectable()
@@ -37,7 +38,7 @@ export class TbankMembershipService {
           .catch(() =>
             this.logger.event('error', 'tbank.membership.persistence_failed', {
               userId,
-              code: 'TBANK_UNAVAILABLE',
+              code: TbankErrorCode.Unavailable,
             }),
           )
           .finally(() => this.active.delete(attemptId));
@@ -62,7 +63,7 @@ export class TbankMembershipService {
     } catch (error) {
       await this.access.failMembership(
         attempt,
-        error instanceof Error && error.message === 'INVALID_TBANK_TOKEN',
+        error instanceof Error && isTbankErrorCode(error.message, TbankErrorCode.InvalidToken),
       );
     }
   }
diff --git a/src/integrations/tbank/tbank-protocol.spec.ts b/src/integrations/tbank/tbank-protocol.spec.ts
new file mode 100644
index 0000000..e34be02
--- /dev/null
+++ b/src/integrations/tbank/tbank-protocol.spec.ts
@@ -0,0 +1,42 @@
+import { loadSync } from '@grpc/proto-loader';
+import { join } from 'node:path';
+
+import { isTbankErrorCode, TbankErrorCode } from './tbank-error-code';
+import {
+  InstrumentIdType,
+  isTbankProtocolValue,
+  TbankAccountStatus,
+  TbankAccountType,
+  TbankCandleInterval,
+  TbankCouponType,
+  TbankInstrumentType,
+  TbankOperationState,
+  TbankOperationType,
+} from './tbank-protocol';
+
+it('uses the string enum values declared by the vendored protocol', () => {
+  const directory = join(__dirname, 'proto/contracts');
+  const definitions = loadSync(['users.proto', 'instruments.proto', 'operations.proto', 'marketdata.proto'].map((file) => join(directory, file)), { includeDirs: [directory], enums: String });
+  for (const [name, values] of Object.entries({
+    InstrumentIdType,
+    InstrumentType: TbankInstrumentType,
+    AccountStatus: TbankAccountStatus,
+    AccountType: TbankAccountType,
+    CandleInterval: TbankCandleInterval,
+    CouponType: TbankCouponType,
+    OperationState: TbankOperationState,
+    OperationType: TbankOperationType,
+  })) {
+    const definition = definitions[`tinkoff.public.invest.api.contract.v1.${name}`];
+    expect(definition).toHaveProperty('format', 'Protocol Buffer 3 EnumDescriptorProto');
+    const descriptor = definition as { type: { value: { name: string }[] } };
+    expect(descriptor.type.value.map((member) => member.name)).toEqual(expect.arrayContaining(Object.values(values)));
+  }
+});
+
+it('recognizes supported wire values without accepting unknown ones', () => {
+  expect(isTbankProtocolValue('OPERATION_STATE_EXECUTED', TbankOperationState.Executed)).toBe(true);
+  expect(isTbankProtocolValue('NEW_UPSTREAM_STATE', TbankOperationState.Executed)).toBe(false);
+  expect(isTbankErrorCode('INVALID_TBANK_TOKEN', TbankErrorCode.InvalidToken)).toBe(true);
+  expect(isTbankErrorCode('NEW_UPSTREAM_ERROR', TbankErrorCode.InvalidToken)).toBe(false);
+});
diff --git a/src/integrations/tbank/tbank-protocol.ts b/src/integrations/tbank/tbank-protocol.ts
new file mode 100644
index 0000000..ebfbaf8
--- /dev/null
+++ b/src/integrations/tbank/tbank-protocol.ts
@@ -0,0 +1,70 @@
+// String wire values for the protocol subset used by this integration.
+// proto-loader decodes enums as strings; vendor contracts remain the source.
+export enum InstrumentIdType {
+  Figi = 'INSTRUMENT_ID_TYPE_FIGI',
+  Uid = 'INSTRUMENT_ID_TYPE_UID',
+}
+
+export enum TbankInstrumentType {
+  Bond = 'INSTRUMENT_TYPE_BOND',
+  Share = 'INSTRUMENT_TYPE_SHARE',
+}
+
+export enum TbankAccountStatus {
+  Open = 'ACCOUNT_STATUS_OPEN',
+}
+
+export enum TbankAccountType {
+  InvestBox = 'ACCOUNT_TYPE_INVEST_BOX',
+  InvestFund = 'ACCOUNT_TYPE_INVEST_FUND',
+  Tinkoff = 'ACCOUNT_TYPE_TINKOFF',
+  TinkoffIis = 'ACCOUNT_TYPE_TINKOFF_IIS',
+}
+
+export enum TbankCandleInterval {
+  Day = 'CANDLE_INTERVAL_DAY',
+}
+
+export enum TbankOperationState {
+  Executed = 'OPERATION_STATE_EXECUTED',
+}
+
+export enum TbankCouponType {
+  Floating = 'COUPON_TYPE_FLOATING',
+  Unspecified = 'COUPON_TYPE_UNSPECIFIED',
+}
+
+export enum TbankOperationType {
+  BondTax = 'OPERATION_TYPE_BOND_TAX',
+  BrokerFee = 'OPERATION_TYPE_BROKER_FEE',
+  Buy = 'OPERATION_TYPE_BUY',
+  BuyCard = 'OPERATION_TYPE_BUY_CARD',
+  BuyMargin = 'OPERATION_TYPE_BUY_MARGIN',
+  Coupon = 'OPERATION_TYPE_COUPON',
+  DivExt = 'OPERATION_TYPE_DIV_EXT',
+  Dividend = 'OPERATION_TYPE_DIVIDEND',
+  DividendTax = 'OPERATION_TYPE_DIVIDEND_TAX',
+  DividendTransfer = 'OPERATION_TYPE_DIVIDEND_TRANSFER',
+  Input = 'OPERATION_TYPE_INPUT',
+  InputSecurities = 'OPERATION_TYPE_INPUT_SECURITIES',
+  MarginFee = 'OPERATION_TYPE_MARGIN_FEE',
+  Output = 'OPERATION_TYPE_OUTPUT',
+  OutputSecurities = 'OPERATION_TYPE_OUTPUT_SECURITIES',
+  Sell = 'OPERATION_TYPE_SELL',
+  SellCard = 'OPERATION_TYPE_SELL_CARD',
+  SellMargin = 'OPERATION_TYPE_SELL_MARGIN',
+  ServiceFee = 'OPERATION_TYPE_SERVICE_FEE',
+  SuccessFee = 'OPERATION_TYPE_SUCCESS_FEE',
+  Tax = 'OPERATION_TYPE_TAX',
+  TransBsBs = 'OPERATION_TYPE_TRANS_BS_BS',
+  TransIisBs = 'OPERATION_TYPE_TRANS_IIS_BS',
+  Unspecified = 'OPERATION_TYPE_UNSPECIFIED',
+}
+
+// Provider responses may contain values newer than our supported protocol subset.
+export function isTbankProtocolValue(
+  value: unknown,
+  expected: TbankCouponType | TbankInstrumentType | TbankOperationState | TbankOperationType,
+): boolean {
+  return value === expected;
+}
diff --git a/src/integrations/tbank/tbank-token.service.ts b/src/integrations/tbank/tbank-token.service.ts
index e029e07..92e80b5 100644
--- a/src/integrations/tbank/tbank-token.service.ts
+++ b/src/integrations/tbank/tbank-token.service.ts
@@ -2,6 +2,7 @@ import { BadRequestException, Injectable } from '@nestjs/common';
 import { ConfigService } from '@nestjs/config';
 
 import { Environment } from '../../config/env.validation';
+import { isTbankErrorCode, TbankErrorCode } from './tbank-error-code';
 import { TbankCrypto } from './tbank.crypto';
 
 @Injectable()
@@ -26,8 +27,8 @@ export class TbankTokenService {
     try {
       return await operation();
     } catch (error) {
-      if (error instanceof Error && error.message === 'INVALID_TBANK_TOKEN') {
-        throw new BadRequestException({ code: 'INVALID_TBANK_TOKEN' });
+      if (error instanceof Error && isTbankErrorCode(error.message, TbankErrorCode.InvalidToken)) {
+        throw new BadRequestException({ code: TbankErrorCode.InvalidToken });
       }
       throw error;
     }
diff --git a/src/integrations/tbank/tbank.client.spec.ts b/src/integrations/tbank/tbank.client.spec.ts
index 525ab85..56b6fb6 100644
--- a/src/integrations/tbank/tbank.client.spec.ts
+++ b/src/integrations/tbank/tbank.client.spec.ts
@@ -1,6 +1,7 @@
 import { status } from '@grpc/grpc-js';
 import { NotFoundException, ServiceUnavailableException } from '@nestjs/common';
 
+import { TbankOperationState } from './tbank-protocol';
 import { TbankClient } from './tbank.client';
 
 describe('TbankClient operations', () => {
@@ -10,7 +11,7 @@ describe('TbankClient operations', () => {
     to: { seconds: '2' },
     cursor: 'cursor',
     limit: 10,
-    state: 'OPERATION_STATE_EXECUTED' as const,
+    state: TbankOperationState.Executed,
   };
 
   it('passes a cursor operations request to OperationsService', async () => {
diff --git a/src/integrations/tbank/tbank.client.ts b/src/integrations/tbank/tbank.client.ts
index 3cdcfb8..a3ff196 100644
--- a/src/integrations/tbank/tbank.client.ts
+++ b/src/integrations/tbank/tbank.client.ts
@@ -29,6 +29,14 @@ import type {
 import { StructuredLogger } from '../../common/logging/structured-logger.service';
 import { MILLISECONDS_PER_SECOND } from '../../common/time';
 import { Environment } from '../../config/env.validation';
+import { TbankErrorCode } from './tbank-error-code';
+import {
+  InstrumentIdType,
+  TbankAccountStatus,
+  TbankCandleInterval,
+  TbankInstrumentType,
+  TbankOperationState,
+} from './tbank-protocol';
 
 const INITIAL_REQUEST_COUNT = 0;
 const MIN_RATE_DELAY_MS = 1;
@@ -115,7 +123,7 @@ export type TbankOperationsByCursorRequest = {
   from?: TbankTimestamp;
   instrumentId?: string;
   limit?: number;
-  state: 'OPERATION_STATE_EXECUTED';
+  state: TbankOperationState.Executed;
   to?: TbankTimestamp;
 };
 export type TbankOperationsByCursorResponse = {
@@ -256,7 +264,7 @@ export class TbankClient {
       token,
       this.users,
       'getAccounts',
-      { status: 'ACCOUNT_STATUS_OPEN' },
+      { status: TbankAccountStatus.Open },
     ).then((response) => response.accounts ?? []);
   }
 
@@ -279,14 +287,14 @@ export class TbankClient {
     token: string,
     figi: string,
   ): Promise<null | TbankInstrument> {
-    return this.getInstrument(token, 'INSTRUMENT_ID_TYPE_FIGI', figi);
+    return this.getInstrument(token, InstrumentIdType.Figi, figi);
   }
 
   getInstrumentByUid(
     token: string,
     instrumentUid: string,
   ): Promise<null | TbankInstrument> {
-    return this.getInstrument(token, 'INSTRUMENT_ID_TYPE_UID', instrumentUid);
+    return this.getInstrument(token, InstrumentIdType.Uid, instrumentUid);
   }
 
   getDividends(
@@ -314,7 +322,7 @@ export class TbankClient {
       'findInstrument',
       {
         query,
-        instrumentKind: 'INSTRUMENT_TYPE_SHARE',
+        instrumentKind: TbankInstrumentType.Share,
       },
     ).then((response) => response.instruments ?? []);
   }
@@ -326,7 +334,7 @@ export class TbankClient {
       'findInstrument',
       {
         query,
-        instrumentKind: 'INSTRUMENT_TYPE_BOND',
+        instrumentKind: TbankInstrumentType.Bond,
       },
     ).then((response) => response.instruments ?? []);
   }
@@ -337,7 +345,7 @@ export class TbankClient {
       this.sparseInstruments,
       'bondBy',
       {
-        idType: 'INSTRUMENT_ID_TYPE_UID',
+        idType: InstrumentIdType.Uid,
         id: uid,
       },
     ).then((response) => response.instrument ?? null);
@@ -367,7 +375,7 @@ export class TbankClient {
       this.instruments,
       'shareBy',
       {
-        idType: 'INSTRUMENT_ID_TYPE_UID',
+        idType: InstrumentIdType.Uid,
         id: uid,
       },
     ).then((response) => response.instrument ?? null);
@@ -446,7 +454,7 @@ export class TbankClient {
         to: {
           seconds: String(Math.floor(to.valueOf() / MILLISECONDS_PER_SECOND)),
         },
-        interval: 'CANDLE_INTERVAL_DAY',
+        interval: TbankCandleInterval.Day,
         limit: 2400,
       },
     ).then((response) => response.candles ?? []);
@@ -454,7 +462,7 @@ export class TbankClient {
 
   private async getInstrument(
     token: string,
-    idType: 'INSTRUMENT_ID_TYPE_FIGI' | 'INSTRUMENT_ID_TYPE_UID',
+    idType: InstrumentIdType,
     id: string,
   ): Promise<null | TbankInstrument> {
     try {
@@ -484,7 +492,7 @@ export class TbankClient {
       const queueFull = this.queue.size >= MAX_QUEUE_SIZE;
       try {
         if (queueFull) {
-          throw new ServiceUnavailableException({ code: 'TBANK_UNAVAILABLE' });
+          throw new ServiceUnavailableException({ code: TbankErrorCode.Unavailable });
         }
         const response = await this.queue.run(() =>
           this.request<Response>(token, client, method, request),
@@ -498,7 +506,7 @@ export class TbankClient {
       } catch (error) {
         const grpcCode = (error as ServiceError).code;
         const failureContext = queueFull
-          ? { code: 'TBANK_UNAVAILABLE' }
+          ? { code: TbankErrorCode.Unavailable }
           : { grpcCode };
         const retryable = queueFull
           ? metadataCall
@@ -534,7 +542,7 @@ export class TbankClient {
           [status.PERMISSION_DENIED, status.UNAUTHENTICATED].includes(grpcCode)
         ) {
           // eslint-disable-next-line preserve-caught-error -- Discard raw upstream authentication errors at the integration boundary.
-          throw new Error('INVALID_TBANK_TOKEN');
+          throw new Error(TbankErrorCode.InvalidToken);
         }
         if (
           grpcCode === status.NOT_FOUND &&
@@ -542,10 +550,10 @@ export class TbankClient {
         ) {
           throw new NotFoundException();
         }
-        throw new ServiceUnavailableException({ code: 'TBANK_UNAVAILABLE' });
+        throw new ServiceUnavailableException({ code: TbankErrorCode.Unavailable });
       }
     }
-    throw new ServiceUnavailableException({ code: 'TBANK_UNAVAILABLE' });
+    throw new ServiceUnavailableException({ code: TbankErrorCode.Unavailable });
   }
 
   private request<Response>(
diff --git a/src/modules/auth/application/auth-error-code.ts b/src/modules/auth/application/auth-error-code.ts
new file mode 100644
index 0000000..0b3bcc7
--- /dev/null
+++ b/src/modules/auth/application/auth-error-code.ts
@@ -0,0 +1,4 @@
+export enum AuthErrorCode {
+  EmailAlreadyRegistered = 'EMAIL_ALREADY_REGISTERED',
+  InvalidCredentials = 'INVALID_CREDENTIALS',
+}
diff --git a/src/modules/auth/application/auth.service.ts b/src/modules/auth/application/auth.service.ts
index 19baedb..8410ab6 100644
--- a/src/modules/auth/application/auth.service.ts
+++ b/src/modules/auth/application/auth.service.ts
@@ -8,7 +8,10 @@ import * as bcrypt from 'bcrypt';
 import { createHash, randomUUID } from 'crypto';
 
 import { Session, User } from '../../../../generated/prisma/client';
+import { HttpErrorCode } from '../../../common/error-code';
+import { isPrismaErrorCode, PrismaErrorCode } from '../../../prisma/prisma-error-code';
 import { PrismaService } from '../../../prisma/prisma.service';
+import { AuthErrorCode } from './auth-error-code';
 import { AuthUser, RefreshPayload } from './auth.types';
 
 const EXPECTED_ROTATED_SESSIONS = 1;
@@ -37,7 +40,7 @@ export class AuthService {
       where: { email },
     });
     if (existing) {
-      throw new ConflictException({ code: 'EMAIL_ALREADY_REGISTERED' });
+      throw new ConflictException({ code: AuthErrorCode.EmailAlreadyRegistered });
     }
 
     let user: User;
@@ -51,7 +54,7 @@ export class AuthService {
       });
     } catch (error) {
       if (isUniqueConstraintError(error)) {
-        throw new ConflictException({ code: 'EMAIL_ALREADY_REGISTERED' });
+        throw new ConflictException({ code: AuthErrorCode.EmailAlreadyRegistered });
       }
       throw error;
     }
@@ -70,7 +73,7 @@ export class AuthService {
       user?.passwordHash ?? DUMMY_PASSWORD_HASH,
     );
     if (!user || !valid) {
-      throw new UnauthorizedException({ code: 'INVALID_CREDENTIALS' });
+      throw new UnauthorizedException({ code: AuthErrorCode.InvalidCredentials });
     }
     return this.createSession(user);
   }
@@ -84,10 +87,10 @@ export class AuthService {
         algorithms: ['HS256'],
       });
     } catch {
-      throw new UnauthorizedException({ code: 'UNAUTHORIZED' });
+      throw new UnauthorizedException({ code: HttpErrorCode.Unauthorized });
     }
     if (payload.type !== 'refresh') {
-      throw new UnauthorizedException({ code: 'UNAUTHORIZED' });
+      throw new UnauthorizedException({ code: HttpErrorCode.Unauthorized });
     }
     const session = await this.prisma.session.findUnique({
       where: { id: payload.sid },
@@ -102,10 +105,10 @@ export class AuthService {
       if (session && !session.revokedAt) {
         await this.prisma.session.delete({ where: { id: session.id } });
       }
-      throw new UnauthorizedException({ code: 'UNAUTHORIZED' });
+      throw new UnauthorizedException({ code: HttpErrorCode.Unauthorized });
     }
     if (session.refreshTokenHash !== this.hash(token)) {
-      throw new UnauthorizedException({ code: 'UNAUTHORIZED' });
+      throw new UnauthorizedException({ code: HttpErrorCode.Unauthorized });
     }
     return this.rotateSession(session, session.refreshTokenHash);
   }
@@ -142,7 +145,7 @@ export class AuthService {
 
   async userById(id: string): Promise<User> {
     const user = await this.prisma.user.findUnique({ where: { id } });
-    if (!user) throw new UnauthorizedException({ code: 'UNAUTHORIZED' });
+    if (!user) throw new UnauthorizedException({ code: HttpErrorCode.Unauthorized });
     return user;
   }
 
@@ -183,7 +186,7 @@ export class AuthService {
         data,
       });
       if (updated.count !== EXPECTED_ROTATED_SESSIONS) {
-        throw new UnauthorizedException({ code: 'UNAUTHORIZED' });
+        throw new UnauthorizedException({ code: HttpErrorCode.Unauthorized });
       }
     } else {
       await this.prisma.session.update({ where: { id: session.id }, data });
@@ -208,6 +211,6 @@ function isUniqueConstraintError(error: unknown): boolean {
     typeof error === 'object' &&
     error !== null &&
     'code' in error &&
-    (error as { code?: unknown }).code === 'P2002'
+    isPrismaErrorCode(error.code, PrismaErrorCode.UniqueConstraint)
   );
 }
diff --git a/src/modules/auth/infrastructure/jwt.strategy.ts b/src/modules/auth/infrastructure/jwt.strategy.ts
index 96110de..ce4cfd9 100644
--- a/src/modules/auth/infrastructure/jwt.strategy.ts
+++ b/src/modules/auth/infrastructure/jwt.strategy.ts
@@ -3,6 +3,7 @@ import { ConfigService } from '@nestjs/config';
 import { PassportStrategy } from '@nestjs/passport';
 import { ExtractJwt, Strategy } from 'passport-jwt';
 
+import { HttpErrorCode } from '../../../common/error-code';
 import { Environment } from '../../../config/env.validation';
 import { AccessPayload } from '../application/auth.types';
 
@@ -19,7 +20,7 @@ export class JwtStrategy extends PassportStrategy(Strategy) {
 
   validate(payload: AccessPayload): AccessPayload {
     if (payload.type !== 'access') {
-      throw new UnauthorizedException({ code: 'UNAUTHORIZED' });
+      throw new UnauthorizedException({ code: HttpErrorCode.Unauthorized });
     }
     return payload;
   }
diff --git a/src/modules/auth/presentation/auth.controller.ts b/src/modules/auth/presentation/auth.controller.ts
index c169f0e..8f78326 100644
--- a/src/modules/auth/presentation/auth.controller.ts
+++ b/src/modules/auth/presentation/auth.controller.ts
@@ -21,6 +21,7 @@ import {
 } from '@nestjs/swagger';
 
 import { ApiProblemResponses } from '../../../common/decorators/api-safe-error-response.decorator';
+import { HttpErrorCode } from '../../../common/error-code';
 import { AuthService } from '../application/auth.service';
 import { AccessPayload } from '../application/auth.types';
 import { CredentialsDto } from './auth.dto';
@@ -86,7 +87,7 @@ export class AuthController {
   ) {
     try {
       const token = this.refreshToken(request);
-      if (!token) throw new UnauthorizedException({ code: 'UNAUTHORIZED' });
+      if (!token) throw new UnauthorizedException({ code: HttpErrorCode.Unauthorized });
       return this.respond(response, await this.auth.refresh(token));
     } catch (error) {
       if (error instanceof UnauthorizedException) this.clearCookie(response);
diff --git a/src/modules/banking/bank-cards/application/bank-card-input.ts b/src/modules/banking/bank-cards/application/bank-card-input.ts
index 8bb0dd6..0fe28ac 100644
--- a/src/modules/banking/bank-cards/application/bank-card-input.ts
+++ b/src/modules/banking/bank-cards/application/bank-card-input.ts
@@ -22,24 +22,23 @@ import {
 const NEXT_MONTH_OFFSET = 1;
 const PREVIOUS_MONTH_LAST_DAY = 0;
 
-export const BankErrorCode = {
-  InvalidInput: 'BANK_INVALID_INPUT',
-  VersionConflict: 'BANK_VERSION_CONFLICT',
-  NotFound: 'BANK_NOT_FOUND',
-  InvalidMoney: 'BANK_INVALID_MONEY',
-  InvalidDate: 'BANK_INVALID_DATE',
-  ImmutableOperation: 'BANK_IMMUTABLE_OPERATION',
-  InvalidRefund: 'BANK_INVALID_REFUND',
-  RefundLimit: 'BANK_REFUND_LIMIT',
-  DependentRefunds: 'BANK_DEPENDENT_REFUNDS',
-  IntentConflict: 'BANK_INTENT_CONFLICT',
-  OperationDeleted: 'BANK_OPERATION_DELETED',
-  CardArchived: 'BANK_CARD_ARCHIVED',
-  OpeningDateConflict: 'BANK_OPENING_DATE_CONFLICT',
-  WriteConflict: 'BANK_WRITE_CONFLICT',
-  DuplicateCategory: 'BANK_DUPLICATE_CATEGORY',
-} as const;
-export type BankErrorCode = (typeof BankErrorCode)[keyof typeof BankErrorCode];
+export enum BankErrorCode {
+  CardArchived = 'BANK_CARD_ARCHIVED',
+  DependentRefunds = 'BANK_DEPENDENT_REFUNDS',
+  DuplicateCategory = 'BANK_DUPLICATE_CATEGORY',
+  ImmutableOperation = 'BANK_IMMUTABLE_OPERATION',
+  IntentConflict = 'BANK_INTENT_CONFLICT',
+  InvalidDate = 'BANK_INVALID_DATE',
+  InvalidInput = 'BANK_INVALID_INPUT',
+  InvalidMoney = 'BANK_INVALID_MONEY',
+  InvalidRefund = 'BANK_INVALID_REFUND',
+  NotFound = 'BANK_NOT_FOUND',
+  OpeningDateConflict = 'BANK_OPENING_DATE_CONFLICT',
+  OperationDeleted = 'BANK_OPERATION_DELETED',
+  RefundLimit = 'BANK_REFUND_LIMIT',
+  VersionConflict = 'BANK_VERSION_CONFLICT',
+  WriteConflict = 'BANK_WRITE_CONFLICT',
+}
 
 export function fail(code: BankErrorCode = BankErrorCode.InvalidInput): never {
   throw new BadRequestException({ code });
diff --git a/src/modules/banking/bank-cards/infrastructure/bank-cards.repository.ts b/src/modules/banking/bank-cards/infrastructure/bank-cards.repository.ts
index 52a54e4..95a29ad 100644
--- a/src/modules/banking/bank-cards/infrastructure/bank-cards.repository.ts
+++ b/src/modules/banking/bank-cards/infrastructure/bank-cards.repository.ts
@@ -2,6 +2,7 @@ import { Injectable } from '@nestjs/common';
 import { randomUUID } from 'node:crypto';
 
 import { Prisma } from '../../../../../generated/prisma/client';
+import { isPrismaErrorCode, PrismaErrorCode } from '../../../../prisma/prisma-error-code';
 import { PrismaService } from '../../../../prisma/prisma.service';
 import {
   BankErrorCode,
@@ -44,15 +45,15 @@ export class BankCardsRepository {
             ? error.code
             : '';
         const busy =
-          code === 'P2034' ||
-          code === 'P2028' ||
+          isPrismaErrorCode(code, PrismaErrorCode.WriteConflict) ||
+          isPrismaErrorCode(code, PrismaErrorCode.TransactionFailure) ||
           (error instanceof Error &&
             /SQLITE_BUSY|database is locked/.test(error.message));
-        if ((busy || code === 'P2002') && attempt < MAX_WRITE_RETRY_COUNT) {
+        if ((busy || isPrismaErrorCode(code, PrismaErrorCode.UniqueConstraint)) && attempt < MAX_WRITE_RETRY_COUNT) {
           continue;
         }
         if (busy) conflict(BankErrorCode.WriteConflict);
-        if (code === 'P2002') conflict(BankErrorCode.DuplicateCategory);
+        if (isPrismaErrorCode(code, PrismaErrorCode.UniqueConstraint)) conflict(BankErrorCode.DuplicateCategory);
         throw error;
       }
     }
diff --git a/src/modules/investments/income/income-analytics.service.ts b/src/modules/investments/income/income-analytics.service.ts
index 0c8e551..480e37c 100644
--- a/src/modules/investments/income/income-analytics.service.ts
+++ b/src/modules/investments/income/income-analytics.service.ts
@@ -8,6 +8,7 @@ import {
   formatDecimal,
   subtract,
 } from '../../../common/decimal';
+import { isTbankProtocolValue, TbankOperationType } from '../../../integrations/tbank/tbank-protocol';
 import { DateOnlyRange, moscowDate } from '../investment-calendar';
 import { investmentResourceMeta } from '../investment-resource.mapper';
 import {
@@ -165,7 +166,7 @@ function qualifying(entries: BrokerageOperationDto[]): BrokerageOperationDto[] {
   return entries.filter(
     (entry) =>
       Boolean(entry.payment) &&
-      ['OPERATION_TYPE_COUPON', 'OPERATION_TYPE_DIVIDEND'].includes(entry.type),
+      [TbankOperationType.Coupon, TbankOperationType.Dividend].some((type) => isTbankProtocolValue(entry.type, type)),
   );
 }
 
@@ -184,7 +185,7 @@ function totals(entries: BrokerageOperationDto[]): IncomeCurrencySummaryDto[] {
     if (!entry.payment) continue;
     const total = values.get(entry.payment.currency) ?? zeroTotal();
     const value = decimalFromString(entry.payment.value);
-    if (entry.type === 'OPERATION_TYPE_COUPON') {
+    if (isTbankProtocolValue(entry.type, TbankOperationType.Coupon)) {
       total.coupon = add(total.coupon, value);
     } else total.dividend = add(total.dividend, value);
     values.set(entry.payment.currency, total);
diff --git a/src/modules/investments/income/income-period.ts b/src/modules/investments/income/income-period.ts
index 32f91699..b4522f6 100644
--- a/src/modules/investments/income/income-period.ts
+++ b/src/modules/investments/income/income-period.ts
@@ -8,6 +8,8 @@ import {
   utcDate,
 } from '../investment-calendar';
 
+enum IncomeErrorCode { InvalidPeriod = 'INVALID_INCOME_PERIOD' }
+
 const MONDAY_WEEKDAY_INDEX = 1;
 const INCLUSIVE_DAY_OFFSET = 1;
 const NEXT_DAY_OFFSET = 1;
@@ -163,5 +165,5 @@ function yearAgo(range: DateOnlyRange): DateOnlyRange | null {
 }
 
 function invalidPeriod(): BadRequestException {
-  return new BadRequestException({ code: 'INVALID_INCOME_PERIOD' });
+  return new BadRequestException({ code: IncomeErrorCode.InvalidPeriod });
 }
diff --git a/src/modules/investments/instruments/application/candle.service.ts b/src/modules/investments/instruments/application/candle.service.ts
index 9566d4e..1c8f778 100644
--- a/src/modules/investments/instruments/application/candle.service.ts
+++ b/src/modules/investments/instruments/application/candle.service.ts
@@ -9,6 +9,7 @@ import { formatDecimal } from '../../../../common/decimal';
 import { StructuredLogger } from '../../../../common/logging/structured-logger.service';
 import { MILLISECONDS_PER_DAY } from '../../../../common/time';
 import { decimal } from '../../../../integrations/tbank/decimal';
+import { isTbankErrorCode, TbankErrorCode } from '../../../../integrations/tbank/tbank-error-code';
 import {
   TbankAccessService,
   TbankClient,
@@ -23,6 +24,7 @@ import {
   candleWindows,
   utcDay,
 } from '../domain/candle-coverage';
+import { InstrumentErrorCode } from '../domain/instrument-error-code';
 import { CandleRepository } from '../infrastructure/candle.repository';
 import { CatalogEnrichmentService } from './catalog-enrichment.service';
 import { timestamp } from './instrument-market';
@@ -71,8 +73,8 @@ function rangeFor(
       throw new ServiceUnavailableException({
         code:
           input.instrumentType === 'share'
-            ? 'STOCK_HISTORY_START_UNAVAILABLE'
-            : 'BOND_HISTORY_START_UNAVAILABLE',
+            ? InstrumentErrorCode.StockHistoryStartUnavailable
+            : InstrumentErrorCode.BondHistoryStartUnavailable,
       });
     }
     from.setTime(utcDay(new Date(history)).valueOf());
@@ -448,7 +450,7 @@ export class CandleService {
         const producer = this.queue.shift();
         if (!producer) break;
         let success = false;
-        let code = 'TBANK_UNAVAILABLE';
+        let code: string = TbankErrorCode.Unavailable;
         try {
           const result = await this.load(producer);
           if (result === null) {
@@ -457,7 +459,7 @@ export class CandleService {
           }
           success = result;
         } catch (error) {
-          if (error instanceof Error && error.message === 'INVALID_TBANK_TOKEN') {
+          if (error instanceof Error && isTbankErrorCode(error.message, TbankErrorCode.InvalidToken)) {
             await this.access.rejectMembershipToken(producer.attempt);
           }
           if (error instanceof ServiceUnavailableException) {
@@ -523,7 +525,7 @@ export class CandleService {
       }
     } catch {
       this.logger.event('error', 'candles.persistence-failed', {
-        code: 'TBANK_UNAVAILABLE',
+        code: TbankErrorCode.Unavailable,
       });
     } finally {
       this.active.clear();
diff --git a/src/modules/investments/instruments/application/catalog-discovery.service.ts b/src/modules/investments/instruments/application/catalog-discovery.service.ts
index 6105b3a..9286681 100644
--- a/src/modules/investments/instruments/application/catalog-discovery.service.ts
+++ b/src/modules/investments/instruments/application/catalog-discovery.service.ts
@@ -6,6 +6,7 @@ import {
 import { randomUUID } from 'node:crypto';
 
 import { StructuredLogger } from '../../../../common/logging/structured-logger.service';
+import { isTbankErrorCode, TbankErrorCode } from '../../../../integrations/tbank/tbank-error-code';
 import {
   TbankAccessService,
   TbankClient,
@@ -14,6 +15,7 @@ import {
   type TbankSyncAttempt,
 } from '../../../../integrations/tbank/tbank.api';
 import { investmentResourceMeta } from '../../investment-resource.mapper';
+import { InstrumentErrorCode } from '../domain/instrument-error-code';
 import {
   CatalogDiscoveryRepository,
   catalogQuery,
@@ -209,8 +211,8 @@ export class CatalogDiscoveryService {
       throw new ConflictException({
         code:
           instrumentType === 'share'
-            ? 'STOCK_TICKER_AMBIGUOUS'
-            : 'BOND_TICKER_AMBIGUOUS',
+            ? InstrumentErrorCode.StockTickerAmbiguous
+            : InstrumentErrorCode.BondTickerAmbiguous,
       });
     }
     const result = lookup.data
@@ -357,11 +359,11 @@ export class CatalogDiscoveryService {
             );
           }
         } catch (error) {
-          if (error instanceof Error && error.message === 'INVALID_TBANK_TOKEN') {
+          if (error instanceof Error && isTbankErrorCode(error.message, TbankErrorCode.InvalidToken)) {
             await this.access.rejectMembershipToken(attempt);
           } else {
             this.logger.event('warn', 'catalog-discovery.failed', {
-              code: 'TBANK_UNAVAILABLE',
+              code: TbankErrorCode.Unavailable,
             });
           }
         }
@@ -395,7 +397,7 @@ export class CatalogDiscoveryService {
       this.producers.clear();
       this.queue.length = 0;
       this.logger.event('error', 'catalog-discovery.persistence-failed', {
-        code: 'TBANK_UNAVAILABLE',
+        code: TbankErrorCode.Unavailable,
       });
     } finally {
       this.running = false;
diff --git a/src/modules/investments/instruments/application/catalog-enrichment.service.ts b/src/modules/investments/instruments/application/catalog-enrichment.service.ts
index 1b8e892..cfc78a0 100644
--- a/src/modules/investments/instruments/application/catalog-enrichment.service.ts
+++ b/src/modules/investments/instruments/application/catalog-enrichment.service.ts
@@ -14,6 +14,7 @@ import {
 import { type MoexBondEvent, MoexClient } from '../../../../integrations/moex/moex.api';
 import { NcrRatingsClient } from '../../../../integrations/ncr/ncr.api';
 import { decimal } from '../../../../integrations/tbank/decimal';
+import { isTbankErrorCode, TbankErrorCode } from '../../../../integrations/tbank/tbank-error-code';
 import {
   TbankAccessService,
   type TbankBond,
@@ -520,11 +521,11 @@ export class CatalogEnrichmentService {
           }
         } catch (error) {
           failed = true;
-          if (error instanceof Error && error.message === 'INVALID_TBANK_TOKEN') {
+          if (error instanceof Error && isTbankErrorCode(error.message, TbankErrorCode.InvalidToken)) {
             await this.access.rejectMembershipToken(producer.attempt);
           } else {
             this.logger.event('warn', 'catalog-enrichment.failed', {
-              code: 'TBANK_UNAVAILABLE',
+              code: TbankErrorCode.Unavailable,
             });
           }
         }
@@ -572,7 +573,7 @@ export class CatalogEnrichmentService {
       this.producers.clear();
       this.queue.length = 0;
       this.logger.event('error', 'catalog-enrichment.persistence-failed', {
-        code: 'TBANK_UNAVAILABLE',
+        code: TbankErrorCode.Unavailable,
       });
     } finally {
       this.running = false;
diff --git a/src/modules/investments/instruments/application/catalog-selection.ts b/src/modules/investments/instruments/application/catalog-selection.ts
index 2928a9e..471dbe4 100644
--- a/src/modules/investments/instruments/application/catalog-selection.ts
+++ b/src/modules/investments/instruments/application/catalog-selection.ts
@@ -1,5 +1,7 @@
 import type { TbankShare } from '../../../../integrations/tbank/tbank.api';
 
+import { TbankInstrumentType } from '../../../../integrations/tbank/tbank-protocol';
+
 export const catalogSearchLimit = 30;
 
 export function selectCatalogInstruments<T extends TbankShare>(
@@ -10,8 +12,8 @@ export function selectCatalogInstruments<T extends TbankShare>(
   const seen = new Set<string>();
   const kind =
     instrumentType === 'share'
-      ? 'INSTRUMENT_TYPE_SHARE'
-      : 'INSTRUMENT_TYPE_BOND';
+      ? TbankInstrumentType.Share
+      : TbankInstrumentType.Bond;
   const preferredClass = instrumentType === 'share' ? 'TQBR' : 'TQOB';
   return found
     .filter(
diff --git a/src/modules/investments/instruments/bonds/application/bond-income.service.ts b/src/modules/investments/instruments/bonds/application/bond-income.service.ts
index ab09102..b96b7d9 100644
--- a/src/modules/investments/instruments/bonds/application/bond-income.service.ts
+++ b/src/modules/investments/instruments/bonds/application/bond-income.service.ts
@@ -7,6 +7,7 @@ import {
   multiply,
 } from '../../../../../common/decimal';
 import { ISO_DATE_LENGTH, ISO_DATE_START } from '../../../../../common/time';
+import { isTbankProtocolValue, TbankCouponType } from '../../../../../integrations/tbank/tbank-protocol';
 import {
   TbankAccessService,
   type TbankBond,
@@ -241,10 +242,10 @@ export function bondMetrics(
         )
       : null;
   const couponType =
-    next?.couponType && next.couponType !== 'COUPON_TYPE_UNSPECIFIED'
+    next?.couponType && !isTbankProtocolValue(next.couponType, TbankCouponType.Unspecified)
       ? next.couponType
       : instrument.floatingCouponFlag === true
-        ? 'COUPON_TYPE_FLOATING'
+        ? TbankCouponType.Floating
         : null;
   return {
     creditRating,
diff --git a/src/modules/investments/instruments/domain/instrument-error-code.ts b/src/modules/investments/instruments/domain/instrument-error-code.ts
new file mode 100644
index 0000000..3f5f103
--- /dev/null
+++ b/src/modules/investments/instruments/domain/instrument-error-code.ts
@@ -0,0 +1,6 @@
+export enum InstrumentErrorCode {
+  BondHistoryStartUnavailable = 'BOND_HISTORY_START_UNAVAILABLE',
+  BondTickerAmbiguous = 'BOND_TICKER_AMBIGUOUS',
+  StockHistoryStartUnavailable = 'STOCK_HISTORY_START_UNAVAILABLE',
+  StockTickerAmbiguous = 'STOCK_TICKER_AMBIGUOUS',
+}
diff --git a/src/modules/investments/instruments/infrastructure/catalog-discovery.repository.ts b/src/modules/investments/instruments/infrastructure/catalog-discovery.repository.ts
index 46fe512..43547bf 100644
--- a/src/modules/investments/instruments/infrastructure/catalog-discovery.repository.ts
+++ b/src/modules/investments/instruments/infrastructure/catalog-discovery.repository.ts
@@ -3,12 +3,9 @@ import { randomUUID } from 'node:crypto';
 import { isDeepStrictEqual } from 'node:util';
 
 import type { Prisma } from '../../../../../generated/prisma/client';
-import type {
-  TbankBond,
-  TbankShare,
-  TbankSyncAttempt,
-} from '../../../../integrations/tbank/tbank.api';
+import type { TbankBond, TbankShare, TbankSyncAttempt } from '../../../../integrations/tbank/tbank.api';
 
+import { TbankErrorCode } from '../../../../integrations/tbank/tbank-error-code';
 import { PrismaService } from '../../../../prisma/prisma.service';
 
 const UNCHANGED_REVISION_INCREMENT = 0;
@@ -462,7 +459,7 @@ export class CatalogDiscoveryRepository {
           state: 'running',
           connection: { invalidToken: true },
         },
-        data: { state: 'failed', errorCode: 'INVALID_TBANK_TOKEN' },
+        data: { state: 'failed', errorCode: TbankErrorCode.InvalidToken },
       });
       await tx.tbankSyncWork.updateMany({
         where: {
@@ -472,7 +469,7 @@ export class CatalogDiscoveryRepository {
         },
         data: {
           state: success ? 'complete' : 'failed',
-          errorCode: success ? null : 'TBANK_UNAVAILABLE',
+          errorCode: success ? null : TbankErrorCode.Unavailable,
         },
       });
     });
diff --git a/src/modules/investments/operations/application/brokerage-operations-sync.service.ts b/src/modules/investments/operations/application/brokerage-operations-sync.service.ts
index fdaad98..4207384 100644
--- a/src/modules/investments/operations/application/brokerage-operations-sync.service.ts
+++ b/src/modules/investments/operations/application/brokerage-operations-sync.service.ts
@@ -3,10 +3,9 @@ import { randomUUID } from 'node:crypto';
 
 import { StructuredLogger } from '../../../../common/logging/structured-logger.service';
 import { MILLISECONDS_PER_SECOND } from '../../../../common/time';
-import {
-  TbankAccessService,
-  TbankClient,
-} from '../../../../integrations/tbank/tbank.api';
+import { isTbankErrorCode, TbankErrorCode } from '../../../../integrations/tbank/tbank-error-code';
+import { TbankOperationState } from '../../../../integrations/tbank/tbank-protocol';
+import { TbankAccessService, TbankClient } from '../../../../integrations/tbank/tbank.api';
 import { accountHistory } from '../../investment-sync-plan';
 import {
   type OperationInterval,
@@ -208,7 +207,7 @@ export class BrokerageOperationsSyncService {
           this.logger.event(
             'error',
             'tbank.operations.sync.persistence_failed',
-            { userId: attempt.userId, code: 'TBANK_UNAVAILABLE' },
+            { userId: attempt.userId, code: TbankErrorCode.Unavailable },
           );
         }
         const next = pending ? await this.repository.pending(attempt) : null;
@@ -272,7 +271,7 @@ export class BrokerageOperationsSyncService {
           : {}),
         cursor,
         limit: operationsPageSize,
-        state: 'OPERATION_STATE_EXECUTED',
+        state: TbankOperationState.Executed,
       });
       if (
         !(await this.repository.stagePage(attempt, interval, cursor, response))
@@ -297,7 +296,7 @@ export class BrokerageOperationsSyncService {
     } catch (error) {
       await this.repository.fail(
         attempt,
-        error instanceof Error && error.message === 'INVALID_TBANK_TOKEN',
+        error instanceof Error && isTbankErrorCode(error.message, TbankErrorCode.InvalidToken),
       );
       return false;
     }
diff --git a/src/modules/investments/operations/application/brokerage-operations.service.ts b/src/modules/investments/operations/application/brokerage-operations.service.ts
index 3a43f43..800dc29 100644
--- a/src/modules/investments/operations/application/brokerage-operations.service.ts
+++ b/src/modules/investments/operations/application/brokerage-operations.service.ts
@@ -17,6 +17,7 @@ import {
   ledgerRange,
   planInvestmentScreen,
 } from '../../investment-sync-plan';
+import { OperationErrorCode } from '../domain/operation-error-code';
 import {
   operationIntervalsOverlap,
   operationsSyncPriority,
@@ -442,7 +443,7 @@ export class BrokerageOperationsService {
       }
       return cursor as LocalOperationsCursor;
     } catch {
-      throw new BadRequestException({ code: 'INVALID_OPERATIONS_CURSOR' });
+      throw new BadRequestException({ code: OperationErrorCode.InvalidOperationsCursor });
     }
   }
 
diff --git a/src/modules/investments/operations/domain/operation-error-code.ts b/src/modules/investments/operations/domain/operation-error-code.ts
new file mode 100644
index 0000000..b3c10d4
--- /dev/null
+++ b/src/modules/investments/operations/domain/operation-error-code.ts
@@ -0,0 +1,3 @@
+export enum OperationErrorCode {
+  InvalidOperationsCursor = 'INVALID_OPERATIONS_CURSOR',
+}
diff --git a/src/modules/investments/operations/infrastructure/brokerage-operation.mapper.ts b/src/modules/investments/operations/infrastructure/brokerage-operation.mapper.ts
index 17782cb..5d2a752 100644
--- a/src/modules/investments/operations/infrastructure/brokerage-operation.mapper.ts
+++ b/src/modules/investments/operations/infrastructure/brokerage-operation.mapper.ts
@@ -1,10 +1,8 @@
 import { formatDecimal } from '../../../../common/decimal';
 import { MILLISECONDS_PER_SECOND } from '../../../../common/time';
 import { decimal } from '../../../../integrations/tbank/decimal';
-import {
-  TbankMoney,
-  TbankOperationItem,
-} from '../../../../integrations/tbank/tbank.api';
+import { TbankOperationType } from '../../../../integrations/tbank/tbank-protocol';
+import { TbankMoney, TbankOperationItem } from '../../../../integrations/tbank/tbank.api';
 import {
   BrokerageOperationDto,
   OperationCategory,
@@ -15,29 +13,29 @@ const MISSING_TIMESTAMP_COMPONENT = 0;
 const NANOSECONDS_PER_MILLISECOND = 1_000_000;
 
 const types: Record<string, OperationCategory> = {
-  OPERATION_TYPE_BUY: 'trade',
-  OPERATION_TYPE_BUY_CARD: 'trade',
-  OPERATION_TYPE_SELL: 'trade',
-  OPERATION_TYPE_SELL_CARD: 'trade',
-  OPERATION_TYPE_BUY_MARGIN: 'trade',
-  OPERATION_TYPE_SELL_MARGIN: 'trade',
-  OPERATION_TYPE_COUPON: 'income',
-  OPERATION_TYPE_DIVIDEND: 'income',
-  OPERATION_TYPE_DIVIDEND_TRANSFER: 'income',
-  OPERATION_TYPE_DIV_EXT: 'income',
-  OPERATION_TYPE_TRANS_IIS_BS: 'transfer',
-  OPERATION_TYPE_TRANS_BS_BS: 'transfer',
-  OPERATION_TYPE_BOND_TAX: 'tax',
-  OPERATION_TYPE_TAX: 'tax',
-  OPERATION_TYPE_DIVIDEND_TAX: 'tax',
-  OPERATION_TYPE_SERVICE_FEE: 'fee',
-  OPERATION_TYPE_MARGIN_FEE: 'fee',
-  OPERATION_TYPE_BROKER_FEE: 'fee',
-  OPERATION_TYPE_SUCCESS_FEE: 'fee',
-  OPERATION_TYPE_INPUT: 'transfer',
-  OPERATION_TYPE_OUTPUT: 'transfer',
-  OPERATION_TYPE_INPUT_SECURITIES: 'transfer',
-  OPERATION_TYPE_OUTPUT_SECURITIES: 'transfer',
+  [TbankOperationType.Buy]: 'trade',
+  [TbankOperationType.BuyCard]: 'trade',
+  [TbankOperationType.Sell]: 'trade',
+  [TbankOperationType.SellCard]: 'trade',
+  [TbankOperationType.BuyMargin]: 'trade',
+  [TbankOperationType.SellMargin]: 'trade',
+  [TbankOperationType.Coupon]: 'income',
+  [TbankOperationType.Dividend]: 'income',
+  [TbankOperationType.DividendTransfer]: 'income',
+  [TbankOperationType.DivExt]: 'income',
+  [TbankOperationType.TransIisBs]: 'transfer',
+  [TbankOperationType.TransBsBs]: 'transfer',
+  [TbankOperationType.BondTax]: 'tax',
+  [TbankOperationType.Tax]: 'tax',
+  [TbankOperationType.DividendTax]: 'tax',
+  [TbankOperationType.ServiceFee]: 'fee',
+  [TbankOperationType.MarginFee]: 'fee',
+  [TbankOperationType.BrokerFee]: 'fee',
+  [TbankOperationType.SuccessFee]: 'fee',
+  [TbankOperationType.Input]: 'transfer',
+  [TbankOperationType.Output]: 'transfer',
+  [TbankOperationType.InputSecurities]: 'transfer',
+  [TbankOperationType.OutputSecurities]: 'transfer',
 };
 
 export function operationCategory(type: string | undefined): OperationCategory {
@@ -51,7 +49,7 @@ export function mapBrokerageOperation(
   return {
     id: operation.id ?? operation.cursor ?? '',
     occurredAt: occurredAt.toISOString(),
-    type: operation.type ?? 'OPERATION_TYPE_UNSPECIFIED',
+    type: operation.type ?? TbankOperationType.Unspecified,
     category: operationCategory(operation.type),
     description: operation.description?.trim() || operation.name?.trim() || '',
     figi: text(operation.figi),
diff --git a/src/modules/investments/operations/infrastructure/brokerage-operations.repository.ts b/src/modules/investments/operations/infrastructure/brokerage-operations.repository.ts
index 5c08d06..7181714 100644
--- a/src/modules/investments/operations/infrastructure/brokerage-operations.repository.ts
+++ b/src/modules/investments/operations/infrastructure/brokerage-operations.repository.ts
@@ -12,12 +12,15 @@ import type {
   TbankOperationsByCursorResponse,
 } from '../../../../integrations/tbank/tbank.api';
 
+import { TbankErrorCode } from '../../../../integrations/tbank/tbank-error-code';
+import { isTbankProtocolValue, TbankOperationState } from '../../../../integrations/tbank/tbank-protocol';
 import { PrismaService } from '../../../../prisma/prisma.service';
 import {
   dateOnlyBounds,
   DateOnlyRange,
   moscowDate,
 } from '../../investment-calendar';
+import { OperationErrorCode } from '../domain/operation-error-code';
 import {
   type OperationInterval,
   operationIntervals,
@@ -137,7 +140,7 @@ export class BrokerageOperationsRepository {
         )
         .digest('base64url');
       if (input.cursor && input.cursor.binding !== binding) {
-        throw new BadRequestException({ code: 'INVALID_OPERATIONS_CURSOR' });
+        throw new BadRequestException({ code: OperationErrorCode.InvalidOperationsCursor });
       }
       const scope = {
         userId: input.userId,
@@ -615,7 +618,7 @@ export class BrokerageOperationsRepository {
         where: { id: attempt.id },
         data: {
           state: 'failed',
-          errorCode: invalidToken ? 'INVALID_TBANK_TOKEN' : 'TBANK_UNAVAILABLE',
+          errorCode: invalidToken ? TbankErrorCode.InvalidToken : TbankErrorCode.Unavailable,
         },
       });
       if (invalidToken) {
@@ -784,7 +787,7 @@ export class BrokerageOperationsRepository {
           }
           const rows = staged.filter((row) => {
             const state = (row.payload as TbankOperationItem).state;
-            return !state || state === 'OPERATION_STATE_EXECUTED';
+            return !state || isTbankProtocolValue(state, TbankOperationState.Executed);
           });
           const scope = {
             userId: attempt.userId,
diff --git a/src/modules/investments/portfolio/application/portfolio.service.ts b/src/modules/investments/portfolio/application/portfolio.service.ts
index e6930dc..8da8363 100644
--- a/src/modules/investments/portfolio/application/portfolio.service.ts
+++ b/src/modules/investments/portfolio/application/portfolio.service.ts
@@ -17,6 +17,7 @@ import { RequestContextService } from '../../../../common/logging/request-contex
 import { StructuredLogger } from '../../../../common/logging/structured-logger.service';
 import { MoneyDto } from '../../../../common/money.dto';
 import { decimal } from '../../../../integrations/tbank/decimal';
+import { isTbankErrorCode, TbankErrorCode } from '../../../../integrations/tbank/tbank-error-code';
 import {
   InstrumentMetadataService,
   type MetadataIdentity,
@@ -387,7 +388,7 @@ export class PortfolioService {
           } catch (error) {
             if (
               error instanceof Error &&
-              error.message === 'INVALID_TBANK_TOKEN'
+              isTbankErrorCode(error.message, TbankErrorCode.InvalidToken)
             ) {
               await this.access.rejectMembershipToken(attempt);
             } else await this.repository.fail(attempt);
@@ -412,7 +413,7 @@ export class PortfolioService {
   async get(userId: string, accountId: string): Promise<PortfolioDto> {
     const result = await this.read(userId, accountId);
     if (!result.data) {
-      throw new ServiceUnavailableException({ code: 'TBANK_UNAVAILABLE' });
+      throw new ServiceUnavailableException({ code: TbankErrorCode.Unavailable });
     }
     return result.data;
   }
diff --git a/src/modules/investments/portfolio/infrastructure/portfolio.repository.ts b/src/modules/investments/portfolio/infrastructure/portfolio.repository.ts
index 22f3b5a..682e9de 100644
--- a/src/modules/investments/portfolio/infrastructure/portfolio.repository.ts
+++ b/src/modules/investments/portfolio/infrastructure/portfolio.repository.ts
@@ -4,10 +4,8 @@ import { randomUUID } from 'node:crypto';
 import type { Prisma } from '../../../../../generated/prisma/client';
 import type { PortfolioDto } from '../presentation/portfolio.dto';
 
-import {
-  tbankSourceNeedsRefresh,
-  tbankSourceTtlMs,
-} from '../../../../integrations/tbank/tbank.api';
+import { TbankErrorCode } from '../../../../integrations/tbank/tbank-error-code';
+import { tbankSourceNeedsRefresh, tbankSourceTtlMs } from '../../../../integrations/tbank/tbank.api';
 import { PrismaService } from '../../../../prisma/prisma.service';
 
 const EXPECTED_UPDATED_ACCOUNTS = 1;
@@ -152,7 +150,7 @@ export class PortfolioRepository {
         state: 'running',
         connection: { invalidToken: false },
       },
-      data: { state: 'failed', errorCode: 'TBANK_UNAVAILABLE' },
+      data: { state: 'failed', errorCode: TbankErrorCode.Unavailable },
     });
     return result.count === EXPECTED_UPDATED_ACCOUNTS;
   }
diff --git a/src/modules/investments/tbank-connection/tbank-connection.service.ts b/src/modules/investments/tbank-connection/tbank-connection.service.ts
index 9bd15ad..cbde0b4 100644
--- a/src/modules/investments/tbank-connection/tbank-connection.service.ts
+++ b/src/modules/investments/tbank-connection/tbank-connection.service.ts
@@ -1,5 +1,6 @@
 import { BadRequestException, Inject, Injectable } from '@nestjs/common';
 
+import { HttpErrorCode } from '../../../common/error-code';
 import {
   supportedTbankAccounts,
   TbankClient,
@@ -29,7 +30,7 @@ export class TbankConnectionService {
 
   async put(userId: string, value: string) {
     const token = value.trim();
-    if (!token) throw new BadRequestException({ code: 'VALIDATION_ERROR' });
+    if (!token) throw new BadRequestException({ code: HttpErrorCode.ValidationError });
     const accounts = await this.tokens.translateInvalidToken(() =>
       this.tbank.validateToken(token),
     );
diff --git a/src/modules/investments/tbank-sync/tbank-sync.service.ts b/src/modules/investments/tbank-sync/tbank-sync.service.ts
index dcd94e7..96f0682 100644
--- a/src/modules/investments/tbank-sync/tbank-sync.service.ts
+++ b/src/modules/investments/tbank-sync/tbank-sync.service.ts
@@ -9,6 +9,7 @@ import { randomUUID } from 'node:crypto';
 import type { InvestmentResourceMetaDto } from '../investment-resource.dto';
 
 import { ISO_DATE_LENGTH, ISO_DATE_START } from '../../../common/time';
+import { TbankErrorCode } from '../../../integrations/tbank/tbank-error-code';
 import {
   InstrumentMetadataService,
   TbankAccessService,
@@ -325,7 +326,7 @@ export class TbankSyncService {
       await this.repository.progress(attempt, children, true);
     } catch {
       await this.repository
-        .progress(attempt, children, true, 'TBANK_UNAVAILABLE')
+        .progress(attempt, children, true, TbankErrorCode.Unavailable)
         .catch(() => undefined);
     }
   }
diff --git a/src/modules/investments/upcoming-events/upcoming-events.service.ts b/src/modules/investments/upcoming-events/upcoming-events.service.ts
index dc30d92..1f61e3f 100644
--- a/src/modules/investments/upcoming-events/upcoming-events.service.ts
+++ b/src/modules/investments/upcoming-events/upcoming-events.service.ts
@@ -31,6 +31,8 @@ import {
   UpcomingEventsQueryDto,
 } from './upcoming-events.dto';
 
+enum EventsErrorCode { InvalidPeriod = 'INVALID_EVENTS_PERIOD' }
+
 const FIRST_BATCH_OFFSET = 0;
 
 const DEFAULT_EVENT_WINDOW_DAYS = 30;
@@ -267,7 +269,7 @@ function dateWindow(query: UpcomingEventsQueryDto) {
   end.setUTCDate(end.getUTCDate() + DEFAULT_EVENT_WINDOW_DAYS);
   const to = query.to ?? end.toISOString().slice(ISO_DATE_START, ISO_DATE_LENGTH);
   if (from > to) {
-    throw new BadRequestException({ code: 'INVALID_EVENTS_PERIOD' });
+    throw new BadRequestException({ code: EventsErrorCode.InvalidPeriod });
   }
   return { from, to };
 }
diff --git a/src/prisma/prisma-error-code.ts b/src/prisma/prisma-error-code.ts
new file mode 100644
index 0000000..20843e3
--- /dev/null
+++ b/src/prisma/prisma-error-code.ts
@@ -0,0 +1,9 @@
+export enum PrismaErrorCode {
+  TransactionFailure = 'P2028',
+  UniqueConstraint = 'P2002',
+  WriteConflict = 'P2034',
+}
+
+export function isPrismaErrorCode(value: unknown, expected: PrismaErrorCode): boolean {
+  return value === expected;
+}
diff --git a/test/eslint-config.cjs b/test/eslint-config.cjs
index c186465..c574386 100644
--- a/test/eslint-config.cjs
+++ b/test/eslint-config.cjs
@@ -61,3 +61,27 @@ test('numeric literals require names, including previously ignored numbers and b
     assert.ok(!named.messages.some(({ ruleId }) => ruleId === '@typescript-eslint/no-magic-numbers'), literal);
   }
 });
+
+// Single-use codes must be caught too; fixture literals remain independent wire assertions.
+test('machine codes require enum members without banning ordinary text or Prisma selects', async () => {
+  const eslint = new ESLint();
+  const filePath = 'src/main.ts';
+  for (const code of ['export function check(code: string) { return code === "one-off-code"; }', 'export const result = `MOEX_UNAVAILABLE`;', 'export const result = { code: "one-off-code" };', 'export const result = { "errorCode": "one-off-code" };', 'export const result = { code: `dynamic-${Date.now()}` };', 'export const result = "MOEX_UNAVAILABLE";', 'export const result = ["INSTRUMENT_ID_TYPE_FIGI"];', 'export const result = { OPERATION_TYPE_COUPON: "income" };']) {
+    const [result] = await eslint.lintText(code, { filePath });
+    assert.equal(result.fatalErrorCount, 0, code);
+    assert.ok(result.messages.some(({ ruleId }) => ruleId === 'no-restricted-syntax'), code);
+  }
+  for (const code of [
+    'enum Code { Unavailable = "MOEX_UNAVAILABLE" } export const result = { code: Code.Unavailable };',
+    'export const select = { code: true, errorCode: true };',
+    'export const label = "Please try again"; export const key = "JWT_SECRET";',
+  ]) {
+    const [result] = await eslint.lintText(code, { filePath });
+    assert.equal(result.fatalErrorCount, 0, code);
+    assert.ok(!result.messages.some(({ ruleId }) => ruleId === 'no-restricted-syntax'), code);
+  }
+  const [fixture] = await eslint.lintText('export const result = { code: "MOEX_UNAVAILABLE" };', { filePath: 'src/integrations/moex/moex.client.spec.ts' });
+  assert.ok(!fixture.messages.some(({ ruleId }) => ruleId === 'no-restricted-syntax'));
+  const [comparison] = await eslint.lintText('enum Code { Ready = "ready" } export function check(code: Code) { return code === "ready"; }', { filePath });
+  assert.ok(comparison.messages.some(({ ruleId }) => ruleId === '@typescript-eslint/no-unsafe-enum-comparison'));
+});