> ## Documentation Index
> Fetch the complete documentation index at: https://musicready.org/llms.txt
> Use this file to discover all available pages before exploring further.

# MIME Types and File Extensions

> Standard MIME types and file extensions for MRS documents.

See: [`/MRS-Specification-RFC#16-mime-types-and-file-extensions`](/MRS-Specification-RFC#16-mime-types-and-file-extensions)

## MIME Types

| Format               | MIME Type                           |
| -------------------- | ----------------------------------- |
| MRS-S                | `application/vnd.mrs+sexpr`         |
| MRS-Ops              | `application/vnd.mrs-ops+sexpr`     |
| Working Set Envelope | `application/vnd.mrs-workset+sexpr` |

## File Extensions

| Format      | Extension          | Persistence                   |
| ----------- | ------------------ | ----------------------------- |
| MRS-S       | `.mrs` or `.mrs-s` | Persisted (canonical storage) |
| MRS-Ops     | `.mrs-ops`         | Typically ephemeral           |
| Working Set | `.mrs-workset`     | Typically ephemeral           |

### Persistence Notes

**MRS-S** is the only format intended for long-term storage. It represents the complete, archival-quality canonical state of a score.

**MRS-Ops** and **Working Set Envelopes** exist as in-memory structures passed between orchestrator and agents. While they can be serialized for debugging or audit logs, they are not typically stored as files.

## Encoding

MRS documents MUST be encoded in UTF-8. The BOM (Byte Order Mark) SHOULD NOT be used.