RFC 0000: Language Model Markup Language (LMML) and Archive Bundle Specification (LMMLZ)

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  • Document Version: 1.0.0
  • Status: Informational / Specification
  • Authors: Oeditus Team
  • Date: September 2026

1. Abstract

This specification defines Language Model Markup Language (LMML), a Markdown-superset markup format for representing structured, multi-turn artificial intelligence (AI) and Large Language Model (LLM) interaction sessions. It also specifies LMMLZ, a portable, single-file zip archive format for packaging an LMML narrative alongside external binary and textual assets.

2. Terminology and Conformance

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 and RFC 8174.

  • Narrative: The underlying UTF-8 text containing human prose, Markdown formatting, and embedded asset references.
  • Embed: A named entity (inline or external) contained or referenced within a narrative.
  • Bundle: A container abstraction representing an LMML entity, regardless of whether it is stored as a bare text file (.lmml) or an archive bundle (.lmmlz).

3. On-Disk Formats

An LMML document MUST be stored in one of two canonical forms:

3.1 Plain Text Form (.lmml)

A single UTF-8 encoded text file bearing the .lmml extension.

  • Constraint: Because a bare text file carries no secondary file payload streams, every embed referenced within a .lmml narrative MUST either be inline (@@@name.ext ... @@@) or be resolved against an external environment. Unresolved external references (@name.ext) in a bare .lmml document MUST evaluate to an unresolvable reference error upon asset resolution.

3.2 Zip Archive Form (.lmmlz)

A standard PKZIP archive (magic bytes 0x50 0x4B 0x03 0x04) bearing the .lmmlz extension.

  • Canonical Entry Naming: An .lmmlz archive MUST contain exactly one primary narrative entry whose filename is derived by stripping the trailing z from the archive file's basename (e.g. archive session.lmmlz MUST contain primary narrative entry session.lmml).
  • Asset Entries: Any additional file stored within the archive represents a named external asset accessible to @name.ext references.

4. Narrative Syntax Specification

LMML is designed as a strict superset of standard Markdown (CommonMark/GFM). Any valid Markdown document MUST parse as a valid LMML narrative with zero embeds.

4.1 External Embed References (@name.ext)

  • Syntax: An @ symbol followed immediately by an asset identifier matching [a-zA-Z0-9_.-]+.
  • Parsing Rules:
    • The identifier MUST begin with an alphanumeric character.
    • Punctuation immediately trailing the identifier (such as periods ., commas ,, or closing parentheses )) MUST NOT be captured as part of the asset name if it constitutes standard sentence punctuation.
    • References nested inside inline spans (code spans `...`) or block constructs (fenced code blocks ```...```) MUST NOT be interpreted as LMML references.

4.2 Inline Embed Blocks (@@@name.ext ... @@@)

  • Syntax:
    @@@name.ext
<content>
@@@
  • Parsing Rules:
    • The opening fence line MUST start with three @ symbols (@@@), followed immediately by the embed name.
    • The content between the opening and closing @@@ lines MUST be captured verbatim (byte-for-byte), without HTML entity escaping or Markdown modification.
    • The closing fence MUST be @@@ on a line by itself.

5. Reserved Embeds and Metadata Conventions

LMML defines standard conventions for structural metadata embeds. Implementations MUST recognize these reserved names when requested by callers:

5.1 manifest.json

An embed named manifest.json (inline or external) carries global session metadata.

  • Format: JSON Object ({ ... }).
  • Semantics: Exposes key-value parameters such as schema versions, model IDs, or session UUIDs.

5.2 settings.yaml / settings.json

An embed named settings.yaml or settings.json carries execution configurations (such as model sampling parameters like temperature, top_p, or custom agent instructions).

6. Multi-Turn Segmentation Protocol

An LMML narrative MAY represent a multi-turn conversation comprising multiple message roles.

6.1 Role Delimiters

Implementations MUST recognize two delimiter syntaxes for demarcating turn boundaries (case-insensitive):

  1. Markdown Headings:

    • ## Turn N -- <role>
    • # <role>
    • ### <role> Where <role> is one of :user, :assistant, :system, or :tool.

  2. HTML Comments:

    • <!-- <role> -->

6.2 Turn Structure and Preamble

  • Text preceding the first role delimiter MUST be assigned to a synthetic :context preamble turn.
  • Text following a delimiter belongs to that turn until the next delimiter or end-of-file.
  • Embeds occurring within a turn's character offset span MUST be bound exclusively to that turn.

7. Extension-Based Asset Handlers and Semantic Resolution

LMML separates asset containment from asset consumption:

  1. Resolution Phase: An implementation MUST resolve every embed name to its underlying raw bytes ({:inline, binary} or {:external, filename}).
  2. Rendering / Handler Phase: Resolved assets MUST be mapped to typed application structures based on file extension (or manifest metadata):
    • Image extensions (.png, .jpg, .jpeg, .webp, .svg, .gif) SHOULD map to image_url data URIs.
    • Text and document extensions (.json, .yaml, .pdf, .csv, .log, .diff) SHOULD map to structured attachment parts.
    • Implementations MAY register custom handlers per extension (e.g. invoking an audio transcriber for .mp3 or code interpreter for .py).

8. Conformance & Cross-Validation Requirements

An implementation's validator MUST report all of the following authoring defects when cross-checking a bundle (Bundle.validate/1):

  1. missing_reference: An external reference @name with no corresponding archive entry.
  2. orphaned_entry: An archive entry not referenced anywhere in the narrative.
  3. malformed_embed_name: An embed name violating safe filename path boundaries.
  4. conflicting_embed: Embeds sharing the same name but carrying conflicting content.

9. Security Considerations

Implementations MUST enforce the following security rules:

  • Path Traversal Immunization: Entry names containing absolute paths (/), backslashes (\), or parent directory segments (..) MUST be rejected up front with {:error, {:unsafe_entry, name}}.
  • Zip Central Directory Inspection: In zip archives (.lmmlz), implementations MUST validate archive central-directory tables (e.g. via :zip.table/1) prior to extracting file bytes into memory or disk.