openworldformat (crates.io)

The Open World Format's Rust reference: the world document (types and edits), the session fold (log, branches, state), and the ext-physics extension's executable half — one serde-only crate, no Bevy, no async, no sockets. The same code that implemented the format in LocalGPT since its origin, extracted into the format's own home.

cargo add openworldformat        # or, from this checkout:
cargo add --path rust openworldformat

use openworldformat::{WorldManifest, OpLogEntry, fold_log, fold_path};

// A head-first package: manifest.json is the world now…
let world: WorldManifest = serde_json::from_str(&manifest_text)?;
// …and the log folds over snapshots/base.json back to it.
let base: WorldManifest = serde_json::from_str(&base_text)?;
let entries: Vec<OpLogEntry> = log_text.lines()
    .filter(|l| !l.trim().is_empty())
    .map(serde_json::from_str).collect::<Result<_, _>>()?;

let doc = fold_log(&base.as_base()?, &entries)?;      // the world at head
let (doc, path) = fold_path(&base.as_base()?, &entries, Some("e3"))?; // or at any tip
let same = doc.to_manifest();                          // a whole manifest again

openworldformat::state::fold_state folds the game state over state.json (save games are base + declaration + a player's log); openworldformat::physics carries the extension's deterministic reference solver, trajectory write/fold, and the conformance outcome runner; the schema feature generates world.schema.json.

The 0.3 surface (draft 0.3: head-first, live authoring)

• The fold is total. WorldDoc carries every manifest field — version, meta, soundtrack, creations, ambience, a next_entity_id that never goes down — and to_manifest writes them all back.
• EditOp::ModifyWorld { patch: Box<WorldPatch> } reaches meta, environment, camera, avatar, tours, soundtrack, ambience and creations (absent unchanged, null clears); its inverse restores them. A first SetEnvironment/SetCamera now inverts to a clearing ModifyWorld.
• authoring::ingest(&doc, &batch) — the Authoring profile: names to ids, ids for spawns, partial struct patches merged (merge_patch, RFC 7396), strict reading, whole-batch refusal with a reason per op.
• manifest_text / manifest_text_of — the canonical text an authority writes, byte-identical to the JS manifestText.
• OpLogEntry.message (optional) — part of the entry's identity.
• Head-first packages: PACKAGE_FORMAT_VERSION is 2, BASE_SNAPSHOT is snapshots/base.json; MergeRecord reads the spec's {"merge": {"branch": …}} (it read {"branch": …} before).

The 0.2 surface (draft 0.2 compliance)

The draft-0.2 tightening, as this crate reads it:

• manifest.version is required — a world that doesn't say which schema it speaks is refused, not defaulted.
• Entity ids cap at MAX_ENTITY_ID (2^53 − 1): alloc_entity_id returns Result, and the fold refuses ids past the ceiling, so worlds this crate generates never overflow a JSON-safe reader.
• The v2 multi-file manifest fields (layout_file, region_files, behavior_files, audio_files, avatar_file) are gone from the type, as they already were from the schema.
• LLM lineage lives under meta["ext-provenance"] (ext_provenance::ExtProvenance) — the ext-provenance extension, not core WorldMeta fields.
• Names bind at ingestion: WorldDoc::apply_entry (which fold_log uses) resolves Orbit.center/LookAt.target name references against the fold-so-far, and WorldManifest::as_base resolves a base manifest against itself — never at fold time.
• oplog::canonical_json + oplog::compute_entry_id: the canonical serializer (no whitespace, sorted keys) and the sha256: entry identity computed over it, identical across the five references for integer-valued JSON.
• EditOp::compute_inverse(&doc): the undo rule in full — a delete's inverse is a batch of spawns holding a deep copy of the deleted tree.
• session::merge_branch: fork merging that reallocates ids allocated concurrently on the main line and rewrites every reference to them before appending.
• package::snapshot_filename (snapshots/entry-<id>.json, falling back to rev-<N>.json) and package::compact_plan (base_revision → head; the host performs the file moves).
• strict::{parse_manifest_strict, decode_line_strict}: must-ignore's off switch for authoring tools — unknown fields, legacy lineage keys and unregistered extensions are refusals, with the extension registry embedded as REGISTERED_EXTENSIONS.

Provenance and the plan

Extracted from LocalGPT's world-types, world-sync and world-physics — not rewritten: in one language, two hand-written type layers would only be drift risk. LocalGPT remains the app-side consumer with its own copies until it's quiet enough to flip them to re-export shims over this crate; until then, both sides generate the same world.schema.json, and the snapshot test in each repository fails when they disagree. The schema's generation_tool default is a pinned literal for the same reason: a published schema must not churn with a generating crate's version.

Two cross-implementation fixes landed with the extraction, applied on both sides: entries may omit author (the spec's own example logs do; the JS fold always read them), and the folded schema is version-independent.

Test

cargo test                      # unit + conformance + examples + physics outcomes
cargo test --features schema    # + the schema snapshot (both generators agree)

CI runs both, alongside the js and python jobs — three references, one set of worlds and outcome assertions.

Apache-2.0.