MCP Releases Draft File-Transfer Extension, Moving File Bytes Out of Model Context

On November 12, 2026, the MCP maintainers published the first draft of an extension, io.modelcontextprotocol/files, designed to move files between clients and tools. The core idea is to take file content out of the model context. Instead of embedding base64 blobs in tool arguments, relying on bespoke presigned-URL conventions, or pasting CSV data directly into prompts, the extension passes only metadata such as the id, the file name, and the MIME type as tool parameters.

The extension is compatible with protocol revision 2026-07-28 and later releases, and the maintainers expect it to reach a stable state before the end of the year. One analysis piece notes, however, that three security design issues remain unresolved at this stage. That is the full extent of what has been reported so far. No conclusions have been reached on how those three issues will be handled, or whether the extension will actually be finalized on schedule, and no further developments have been disclosed beyond the initial draft.