fragmentation

Content-addressed, arbitrary-depth, circular-reflexive trees.

[dependencies]
fragmentation = { git = "https://github.com/systemic-engineering/fragmentation" }

What This Is

A Rust library for building trees where every node is identified by its content. Two node types: Shard (terminal) and Fractal (recursive). Git-compatible SHA-1 hashing at the wire boundary; content-addressed SpectralCoordinate<5> internally. The observer is part of the commit, not the hash.

As of 2026-06-01, fragmentation is also the substrate beneath fragmentation-mcp — a standalone Model Context Protocol server that exposes content-addressed primitives + the HamiltonScheduler's hot/cold management to any agent runtime (Claude Code, Cursor, Zed, any MCP-aware client). See docs/specs/fragmentation-mcp.md for the architecture; the MCP layer lives in the new vcs/mcp/ workspace member. Fragmentation-mcp is the first deployment target of the wider stack — ships standalone, useful without mirror, open-source infrastructure that fills a real gap in the agent-runtime ecosystem (existing git-MCPs are CLI wrappers; this one speaks content-addressed primitives directly).

use fragmentation::fragment::{Fragment, blob_oid};

// Shard -- terminal node
let leaf = Fragment::shard("hello");

// Fractal -- recursive node
let tree = Fragment::fractal("root", vec![leaf]);

// Content-addressed: same content = same hash
let oid = tree.content_oid();

Different witness, different commit. Same content, same tree. The observer changes the record without changing the content.

DAG-native

Fragmentation is graph-native DAG today (v1). Content addressing handles directed acyclic multi-parent references natively: same content → same OID, regardless of how many parents reference it.

• Fractal::Branch carries fractal: Vec<Fractal<E, H>> by value. The same child node, cloned into two parents, collapses to one stored node under the content-address.
• Fractal::Lens carries target: Vec<H> for explicit OID-only references (proper graph edges, not containment). Multiple lenses can point at the same target without duplication.

Cycle handling is deferred to spectral-db (v1.5). spectral-db exercises actually-cyclic graphs with the witnessed-computation contract: each cycle traversal records a measurement, the measurement IS the fixed-point witness, and kintsugi ensures the measurement converges. Fragmentation itself treats cycle detection as an error class; the v1/v1.5 boundary is named in docs/specs/mirror-native-vcs.md §4.6 (Consequence 3).

Adapters

Fragmentation ships as a workspace with VCS-adjacent adapter crates:

Crate	Role
fragmentation	the substrate; content-addressed primitives, hash trait, store types
fragmentation-git (vcs/git/)	git wire interop; SHA-1 ↔ SpectralCoordinate<5> crosswalk; FUSE portal; frgmt-git CLI
fragmentation-jj (vcs/jj/)	jj-native backend (planned; per docs/specs/mirror-native-vcs.md)
fragmentation-mcp (vcs/mcp/, new)	MCP server; agent-runtime substrate; fragmentation serve --stdio

The substrate compiles dependency-free of all adapters; each adapter pulls fragmentation as its dependency. prism_core stays zero-dep.

Fragmentation-mcp is the first deployment target of the wider stack — ships standalone, useful without mirror, open-source infrastructure that fills a real gap in the agent-runtime ecosystem (existing git-MCPs are CLI wrappers; fragmentation-mcp speaks content-addressed primitives directly, with bounded RAM via the HamiltonScheduler and structured drops via [[docs/specs/lens-transit]]). See docs/specs/fragmentation-mcp.md.

Features

Feature	What it enables
git	Read/write fragment trees as native git objects
ssh	Ed25519 signing + ECIES encryption (X25519, ChaCha20-Poly1305)
gpg	GPG signing + encryption via subprocess

Modules

Module	Purpose
fragment	Fragment<E>, construction, content addressing
ref_	Ref -- content address (SHA + label)
sha	Sha -- SHA-1 and SHA-256
store	Content-addressed in-memory storage
walk	Depth-first traversal, fold, find, depth
diff	Positional structural comparison
encoding	Text as five-level fragment trees
witnessed	Commit metadata -- author, committer, timestamp, message
git	Fragment persistence to git repositories
keys	Sign, encrypt, decrypt (SSH, GPG, plain)
actor	Witness identity with encoding boundary and keys

Documentation

See docs/.

Development

cargo test --all-features  # 185 tests

Licence

systemic.engineering License v1.0