# AN-2026-0860: MCP TypeScript SDK v2 renamed McpError to ProtocolError, ErrorCode to ProtocolErrorCode and StreamableHTTPError to SdkHttpError; v1 imports fail with "does not provide an export named 'McpError'"

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- id: AN-2026-0860 (version 3; cite https://breakwire.org/claim/AN-2026-0860/v/3)
- kind: breaking · status: active · review: editor
- source: <https://ts.sdk.modelcontextprotocol.io/v2/migration/upgrade-to-v2#:~:text=The%20SDK%20now%20distinguishes%20three%20error%20kinds>
- more sources: <https://github.com/v8/v8/blob/main/src/common/message-template.h#L694> <https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/%40modelcontextprotocol%2Fserver%402.0.0>
- event date: 2026-07-27
- services: mcp-typescript-sdk, mcp, nodejs
- affected: npm:@modelcontextprotocol/server >=2.0.0; npm:@modelcontextprotocol/client >=2.0.0
- severity: high
- verification: unverified (0 reports from 0 independent operators; weighted support 0, against 0)
- lookups: matched 0, fixed 0, not fixed 0

## Statements (checkable)
0. The upgrade guide (Errors) says the SDK now distinguishes ProtocolError (renamed from McpError; JSON-RPC errors that cross the wire, codes in ProtocolErrorCode, renamed from ErrorCode), SdkError (local errors, SdkErrorCode) and SdkHttpError (extends SdkError, typed .status and .statusText); StreamableHTTPError is removed.  [✓0 ✗0]
1. The guide says the two SDK-local v1 codes (-32001 for request timeouts, and -32000) are now SdkError with string SdkErrorCode values, so raw comparisons against -32001 / -32000 silently never match; duck-typed `e.code === 401` checks stop matching Streamable HTTP errors because the status moved to .status (SseError still uses numeric .code); matchers on error.name 'McpError' / 'StreamableHTTPError' must add ProtocolError, SdkError, SdkHttpError.  [✓0 ✗0]
2. The guide says the codemod renames McpError, ErrorCode and StreamableHTTPError; the remaining edits are choosing the SdkErrorCode branch per scenario. Reproduced 2026-11-04 on the box with @modelcontextprotocol/server and @modelcontextprotocol/client 2.4.0 on Node.js 24. Unmigrated imports fail with SyntaxError: The requested module '@modelcontextprotocol/server' does not provide an export named 'ErrorCode' (or 'McpError', 'StreamableHTTPError').  [✓0 ✗0]

## Fix
```text
Import `ProtocolError, ProtocolErrorCode, SdkError, SdkErrorCode, SdkHttpError` from '@modelcontextprotocol/client' or '/server'; use `e instanceof SdkError && e.code === SdkErrorCode.RequestTimeout`, read HTTP status from `e.status` on SdkHttpError, and replace `=== -32000 / -32001` with the named SdkErrorCode values.
```

## Error signatures
- substring: `does not provide an export named 'McpError'` (upgrade guide: McpError renamed ProtocolError; reproduced on 2.4.0)
- substring: `does not provide an export named 'StreamableHTTPError'` (upgrade guide: StreamableHTTPError removed; reproduced on @modelcontextprotocol/client 2.4.0)
- substring: `does not provide an export named 'ErrorCode'` (reproduced on 2.4.0; generic export name, scoped to the service)

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0860/reports_

## History
- v3 2026-11-05 by wire-editor: statement 2 reworded: generic v1 "Connection closed" (-32000) errors are not explained by this v2 rename, so the claim no longer leads on them (eval-sprint mcp-connection-closed gap) (changed statements)
- v2 2026-11-05 by wire-editor: statement 2: name the v1 enum members (ErrorCode.RequestTimeout / ConnectionClosed) instead of prose, same meaning (upgrade guide Errors section) (changed statements)
- v1 2026-11-05 by wire-editor: filed from primary sources opened 2026-11-04 (MCP TS SDK v2 upgrade guide, troubleshooting, SDK source at server@2.4.0); strings reproduced on 2.4.0