mirror of epic games' lore open source version control
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Filename Latest commit message Latest commit date
Mattias Jansson f205899adf lore-revision: keep the link registry in place so concurrent link edits do not overwrite each other
## Summary
Fixes a data-race in the link registry where a read-modify-write sequence could lose concurrent edits. Previously `link_add`, `link_update`, and `link_remove` each called `link_list` (which released the runtime lock) and then re-acquired the write lock to store the result, so interleaved edits from concurrent tasks would silently overwrite one another.

The fix introduces two helpers:
- `serialized_link_list` - reads the persisted link list from the immutable store, used only when the runtime copy is absent.
- `edit_link_list` - loads the serialized list once (before taking the lock), then holds the write lock across the entire read-modify-write so no two edits can interleave. Callers (`link_add`, `link_update`, `link_remove`) are rewritten to use this helper.

`link_list` is updated to serve the runtime copy directly when present, falling back to `serialized_link_list` only on first access.

Noticed by intermittent failures in smoke tests, reproducable at ~20% rate on my machine with
`uv run pytest scripts/test -m=smoke -k test_link_commit_partial_link_messages --lore-server-binary=./target/debug/loreserver --lore-client-binary=./target/debug/lore` 

Adds a new `reading_the_link_list_leaves_it_editable` unit test: it adds two links, reads the registry (which previously would have discarded the runtime copy), updates one link, then asserts both links are still present and the update is visible.

## Test Plan
Ran the new `reading_the_link_list_leaves_it_editable` unit test on main and verified it failed, reproducing the root issue.

Ran the new unit test on this branch and verified it passed.

Ran the previously failing smoke test 60 times and verified it now passed all 60, where it previously failed with a 20% ratio.

Lore-RevId: 430
Lore-Signature: 298fb3420095895fcc19e9f6e52c3b17f9f4731d6521c703d7b1268fa2c99595
2026-08-03 13:17:35 +00:00
.cargo Emit macOS .dSYM for release-lto (split-debuginfo = packed) 2026-06-09 21:22:45 +00:00
.github ci: Add PR validation workflow 2026-07-31 16:46:47 +00:00
contrib/aws Add Terraform example for AWS deployment 2026-07-21 14:27:15 +00:00
docs Add external instance directory ADR 2026-08-01 15:23:17 +00:00
lore Split network onto a dedicated runtime and remove the rayon compute pool 2026-07-31 09:59:12 +00:00
lore-aws Split network onto a dedicated runtime and remove the rayon compute pool 2026-07-31 09:59:12 +00:00
lore-base lore-server: recompress Oodle fragments to Zstd upon ingestion 2026-07-31 13:08:37 +00:00
lore-capi Split network onto a dedicated runtime and remove the rayon compute pool 2026-07-31 09:59:12 +00:00
lore-chaos-client Remove internal package registry and repository URLs 2026-06-15 14:43:26 +00:00
lore-client Split network onto a dedicated runtime and remove the rayon compute pool 2026-07-31 09:59:12 +00:00
lore-credential Split network onto a dedicated runtime and remove the rayon compute pool 2026-07-31 09:59:12 +00:00
lore-error-set Carry structured error detail and FFI codes on the Complete event 2026-06-24 17:43:05 +00:00
lore-error-set-macro Carry structured error detail and FFI codes on the Complete event 2026-06-24 17:43:05 +00:00
lore-hashicorp Initial code copy from private repo 2026-05-29 18:50:20 +00:00
lore-integration-tests Split network onto a dedicated runtime and remove the rayon compute pool 2026-07-31 09:59:12 +00:00
lore-macro lore: Validate utf8 text passed in args to the API 2026-07-28 13:23:16 +00:00
lore-notification Split network onto a dedicated runtime and remove the rayon compute pool 2026-07-31 09:59:12 +00:00
lore-proto lore-server: Fix created timestamp unit in v1 create RPCs 2026-07-29 11:03:10 +00:00
lore-revision lore-revision: keep the link registry in place so concurrent link edits do not overwrite each other 2026-08-03 13:17:35 +00:00
lore-server Fix branch merge silently dropping out-of-view changes under a sparse view 2026-07-31 15:46:54 +00:00
lore-storage Split network onto a dedicated runtime and remove the rayon compute pool 2026-07-31 09:59:12 +00:00
lore-telemetry lore-telemetry: adjust size_histogram to have larger buckets up to FragmentSize 2026-07-31 13:09:17 +00:00
lore-transport Split network onto a dedicated runtime and remove the rayon compute pool 2026-07-31 09:59:12 +00:00
notices notices: resolve license text for base64-simd, vsimd, and rs-consul 2026-06-05 17:53:57 +00:00
scripts Fix syncing that undoes a change from a file to a directory 2026-08-01 16:51:44 +00:00
vendor/quinn-proto Initial code copy from private repo 2026-05-29 18:50:20 +00:00
.dockerignore Initial code copy from private repo 2026-05-29 18:50:20 +00:00
.gitignore gitignore: Ignore entire .claude/ directory 2026-07-16 11:17:18 +00:00
.loreignore ci: allow .github directory to be tracked for GHA integration 2026-06-16 16:59:34 +00:00
.markdownlint-cli2.jsonc docs: add content_tabs hook for comment-delimited tabs 2026-06-12 20:50:31 +00:00
.pre-commit-clippy.py Add missing executable bit on precommit script and add missing entries to ignore file 2026-06-01 09:00:30 +00:00
.pre-commit-config.yaml Run all pre-commit checks in public GitHub 2026-06-18 15:54:36 +00:00
.rustfmt.toml Initial code copy from private repo 2026-05-29 18:50:20 +00:00
.vale.ini docs: add project level README, migrate Lore design doc, updated branding assets, and glossary 2026-06-05 22:47:33 +00:00
about.toml notices: resolve license text for base64-simd, vsimd, and rs-consul 2026-06-05 17:53:57 +00:00
build-helper.rs lore-base: allow injectable library version name 2026-06-04 10:25:53 +00:00
Cargo.lock Split network onto a dedicated runtime and remove the rayon compute pool 2026-07-31 09:59:12 +00:00
Cargo.toml Split network onto a dedicated runtime and remove the rayon compute pool 2026-07-31 09:59:12 +00:00
clippy.toml Split network onto a dedicated runtime and remove the rayon compute pool 2026-07-31 09:59:12 +00:00
CODE_OF_CONDUCT.md Initial code copy from private repo 2026-05-29 18:50:20 +00:00
CONTRIBUTING.md docs: add public roadmap and crosslink to it across the docs 2026-06-17 11:11:32 +00:00
DCO Initial code copy from private repo 2026-05-29 18:50:20 +00:00
deny.toml Initial code copy from private repo 2026-05-29 18:50:20 +00:00
GOVERNANCE.md update MAINTAINERS to propose adding specialist maintainers 2026-06-23 21:51:30 +00:00
LICENSE Initial code copy from private repo 2026-05-29 18:50:20 +00:00
MAINTAINERS.md update MAINTAINERS to propose adding specialist maintainers 2026-06-23 21:51:30 +00:00
mkdocs.yml docs: add content_tabs hook for comment-delimited tabs 2026-06-12 20:50:31 +00:00
pyproject.toml lore-server: Gate missing-fragment push test on server's failure_generator feature via ServerInfo 2026-06-08 18:39:20 +00:00
pyrightconfig.json Initial code copy from private repo 2026-05-29 18:50:20 +00:00
README.md docs: add public roadmap and crosslink to it across the docs 2026-06-17 11:11:32 +00:00
SECURITY.md update SECURITY to include link to Vulnerability Disclosure Program 2026-06-15 15:39:15 +00:00
uv.lock lore-server: Gate missing-fragment push test on server's failure_generator feature via ServerInfo 2026-06-08 18:39:20 +00:00

Lore — open source version control by Epic Games

Lore

Next-generation open source version control

Download Lore  ·  Quickstart  ·  Read the docs  ·  Join the conversation

License: MIT Built with Rust

Table of contents

About Lore

Lore is an open source version control system designed for unprecedented scalability of both data and teams. It is optimized for projects that combine code with large binary assets, including games and entertainment, and caters for the needs of developers and artists alike.

Note

Lore is pre-1.0 and under active development. Interfaces, on-disk formats, and APIs may change between releases.

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Get started with Lore

  • Quickstart — install Lore and make your first commit by following the quickstart guide.
  • Read the docs — delve into Lore's ethos and architecture in the Lore documentation.
  • Have questions? — the FAQ covers licensing, supported platforms, production readiness, and how Lore compares to other version control systems.
  • See where Lore is headed — the roadmap lays out the big-rock features by time horizon, from scalable locking to an open source desktop client.
  • Join the conversation — chat with us and our community on Discord.

Or try it right now — install Lore and start a local server in demo mode:

macOS / Linux

curl -fsSL https://raw.githubusercontent.com/EpicGames/lore/main/scripts/install.sh | bash -s -- --demo

Windows (PowerShell)

$env:LORE_DEMO=1; irm https://raw.githubusercontent.com/EpicGames/lore/main/scripts/install.ps1 | iex

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Overview

  • Easy setup, on-demand scalability — Get started in local mode in minutes. Then, scale up as far and as fast as you need.
  • Fast and efficient processes — Scale without slowdowns, thanks to shared, reusable data and as-needed downloads.
  • Free branching — Quickly and easily create, manage, and sync branches to freely experiment, iterate, and release.
  • History you can trust — Confidently track and manage revisions with Lore's verifiable tamper-evident source of truth.
  • Intuitive interface — Enjoy complete one-to-one access to the full Lore functionality via the CLI.
  • Full-surface API — Extend, customize, and integrate Lore via C/C++, C#, Rust, Go, Python, or JavaScript.

Note

Lore is the built-in version control system for UEFN (Unreal Editor for Fortnite), but today's open source tooling can't yet talk to it: the UEFN build uses a proprietary compression format that can't ship with the open source project. We're actively moving UEFN onto an open compression format — the same one this open source project uses — to eliminate the gap between the two.

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Lore's architecture

Lore is a centralized, content-addressed version control system that represents repository state as Merkle trees and an immutable revision chain, optimized for binary-first storage, deduplication, and sparse/on-demand data hydration at scale. For the full model—on-disk formats, chunking internals, and the mechanics of the Merkle tree—read the system design doc.

Highlights

  • Content-addressed storage — Repository data is stored and referenced by content hash in a Merkle tree, enabling fast comparisons, integrity checks, and reuse across history and branches.
  • Immutable revision chain — A revision's hash signature is derived from its revision state, including parent revision hashes and contained data hashes, forming an immutable chain with cryptographic integrity.
  • Chunked storage for large files — Files are stored as reusable chunks with indexed lookup, reducing duplication and enabling efficient updates and transfer for large binary assets.
  • On-demand hydration and sparse workspaces — Workspaces can stay lightweight by fetching file data only when needed, so you don't have to download everything up front.
  • Centralized service with caching — A service-backed architecture uses caching in front of durable storage to scale throughput for large teams and repositories.
  • Lightweight branches and fast switching — Branches are lightweight mutable references, so creating and switching branches is low-overhead without duplication of underlying data.

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Lore's repositories

Lore spans a family of repositories: the core library, server, and CLI in this repository, plus a software development kit (SDK) for each supported language.

Repository Description Link
Lore Library, Server & CLI The core Lore library, the Lore Server, and the Lore CLI. You are here. View on GitHub
JavaScript SDK The JavaScript binding for the Lore API. View on GitHub
Python SDK The Python binding for the Lore API. View on GitHub
C# SDK The C# binding for the Lore API. View on GitHub
Go SDK The Go binding for the Lore API. View on GitHub

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Fully open source

We believe a truly open ecosystem is built collectively using open standards. Lore is fully open source under an MIT license, and we invite you to build the version control system of the future in the open. See CONTRIBUTING.md to get involved.

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Contributing

Contributions of every kind are welcome — code, documentation, bug reports, and reviews. Start with CONTRIBUTING.md for the development workflow, then read the Code of Conduct and the project governance model. New to the codebase? The good-first-issue label is a good place to start.

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License

Lore is released under the MIT License. See LICENSE for the full text. Copyright (c) 2026 Epic Games, Inc.

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Contact and community

  • Discord — chat with the team and community on Discord.
  • GitHub Issues — report bugs and request features through GitHub Issues.

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