Levi Neuwirth
fef8520bdf
A shard now seals its accumulated delta into an `IndexRun`, publishes it through the manifest, and discards exactly the layers that run covers in one committed-root CAS. This replaces the `NotImplemented` that refused a shard once it had accumulated `max_index_runs` delta layers. The seal runs at admission, before anything is reserved or sequenced, because a seal that fails partway has to poison and poisoning a shard that has just accepted a transaction owes that caller an answer it can no longer give. Two triggers: `DeltaPressure::SealRequired` over the accumulated entries and bytes, and the layer count, which is the fan-out every lookup pays before it reaches a run and which entry pressure alone does not bound. Everything up to `install_index_run` is pre-durable and fails as an ordinary error; from there the shard poisons on any failure, including one the call may have made before writing. The caller cannot distinguish those, and the conservative direction is refusing to keep writing against a root that may no longer describe the device. `poison_now` latches it — `poison_error` only built the error, which is right inside the publication window whose caller latches for the whole group, and wrong here. Four frozen amendments, all recorded as contract review 2026-07-29-C: `segment::install_index_run` holds the whole durability sequence so no durability operation lives in `engine.rs`; `index::delta_pressure` becomes a free function so the writer's multi-layer backlog asks the same watermark rather than restating it; `CommittedRoot::merge` recognizes a publication that appends no frame, without which the run reaches the manifest and never the root; and a manifest may have an empty retained tail when it commits through zero, which is every shard that has sealed an index but not yet rotated its journal. A finding, recorded in scope §6.5 rather than papered over. Sealing moves entries out of the layers but no frame out of `active/`, and the committed prefix advances only on a checkpoint or a rotation — so recovery still replays everything into one ceiling-bounded delta. The writer therefore refuses once the replayable set reaches `max_active_index_entries`, closing a hole that pre-dates this change: the old layer cap never bounded the summed entries behind it. The consequence is that an entry-pressure seal lands exactly on that ceiling and the next admission is refused; only a fan-out seal leaves the shard able to continue. Entry-pressure sealing becomes useful when `checkpoint()` can advance the prefix. Mutation-checked in both directions. Reverting the discard reports one run beside a three-layer backlog where the test requires zero, so the frozen `IndexMaintenanceSnapshot` is load-bearing. Reverting the `merge` amendment reports zero runs beside a three-layer backlog while `CURRENT` names the run: the silent divergence, arriving quietly. `store-bench` is untouched and stays preliminary. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01XKzM69CHmBuDcA3qN1jFdh |
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| .github/workflows | ||
| bench | ||
| crates | ||
| deploy | ||
| doc | ||
| scripts | ||
| .gitignore | ||
| Cargo.lock | ||
| Cargo.toml | ||
| LICENSE | ||
| README.md | ||
README.md
LeVCS
A distributed version control system with first-class federation, signed authority chains, and a cascading merge engine. Content-addressed by BLAKE3, signed with Ed25519, and built to fix what git can't.
Status: v0.1.0 — protocol substrate complete, workflow surface deferred. The object model, federation API, merge cascade, and instance server all work end-to-end. There is no PR review surface, issue tracker, or web UI yet — those are the next layer up. See
doc/technical-report.mdfor a full framing of where this project is and why.
What's different from git
- Identity is in the protocol. A repo's membership is a versioned, signed authority object with explicit roles (Reader/Contributor/Maintainer/Owner). Force-push enforcement and push authorization are protocol-level, not server policy.
- Federation is first-class. Every repo has a global
repo_id(BLAKE3 of its genesis authority); instances mirror each other in three storage modes (full / release-only / metadata-only). - Merge is a cascade, not a line-level diff. Per-file dispatch to a handler ranked by aggressiveness: textual fallback, format-aware (JSON / YAML / TOML / XML / Markdown / prose), tree-sitter for source code (Rust, Python, JS/TS, Go, C/C++, Java, Ruby, Bash), and wasm-sandboxed plugins for the long tail.
- BLAKE3, not SHA-1. Tree-hashed, ~5 GiB/s on a laptop, 32-byte IDs everywhere.
- Releases are signed objects, not mutable name pointers.
For a deeper comparison and context, see the technical report.
Building
LeVCS is a Rust workspace. You'll need a recent stable toolchain (workspace MSRV is 1.75) and a C compiler for the tree-sitter grammars.
cargo build --release
Two binaries land in target/release/:
levcs— the user-facing CLI.levcs-instance— the federation HTTP server.
Install them somewhere on PATH:
sudo install -m 0755 \
target/release/levcs target/release/levcs-instance \
/usr/local/bin/
Quick start (single user, local only)
# Generate an identity key (stored in $XDG_CONFIG_HOME/levcs/keys.toml).
levcs key generate --label me
# Create a repository wherever you have files to track.
mkdir /tmp/demo && cd /tmp/demo
echo "hello" > a.txt
levcs init --key me
levcs track --all
levcs commit -m "first commit"
levcs log
That's a fully working LeVCS repo. Branch and merge:
levcs branch feature/x
echo "more" >> a.txt
levcs commit -m "wip"
levcs branch main
levcs merge feature/x
If a merge produces conflicts, drop into the resolution TUI:
levcs merge --resolve
Cut a release:
levcs release v0.1.0 --notes "first release"
Hosting an instance
To dogfood the federation surface, run levcs-instance on a VPS behind
nginx or Caddy. The full walkthrough is in
deploy/README.md: build, systemd unit, reverse
proxy templates, firewall, and the laptop-side bootstrap.
The compressed version:
sudo cp deploy/levcs-instance.service /etc/systemd/system/
sudo cp deploy/instance.toml.example /etc/levcs/instance.toml
sudo $EDITOR /etc/levcs/instance.toml
sudo systemctl enable --now levcs-instance
# ... then drop deploy/Caddyfile.example into /etc/caddy/Caddyfile
From your laptop, point the local repo at the instance and push:
levcs instance --set https://levcs.example.com/levcs/v1
levcs push refs/branches/main
The first push to a fresh instance auto-inits the repo with your genesis authority. Subsequent pushes are role-checked against the authority chain.
Repository layout
crates/
levcs-core/ Object model (Blob/Tree/Commit/Release/Authority),
hash, store, refs, repository abstractions.
levcs-identity/ Authority objects, Ed25519 keys, signing/verify.
levcs-merge/ Cascade engine, format and tree-sitter handlers,
plugin runtime, merge records.
levcs-protocol/ Pack codec, wire types, request signing, P2P.
levcs-client/ Thin HTTP client over the federation API.
levcs-instance/ Axum HTTP server (the federation peer).
levcs-cli/ The `levcs` user-facing CLI.
levcs-tui/ Conflict-resolution terminal UI.
deploy/ Production deployment artifacts (systemd, Caddy, nginx).
scripts/ Reproducible benchmark and ops scripts.
doc/ Technical report and architecture docs.
.github/workflows/ CI configuration.
Testing
cargo test --workspace
Runs the full suite — unit tests, integration tests, federation end-to-end tests including the three-instance "dogfood" scenario, the merge conformance corpus, and property-based fuzz tests. ~194 tests at v0.1.0; full run is well under a minute on a modern laptop.
Useful subsets:
# A single crate's tests
cargo test -p levcs-merge
# A specific integration test
cargo test -p levcs-instance --test dogfood
# Property tests only
cargo test -p levcs-merge --test proptest_textual
Benchmarks
Microbenchmarks live in each crate's benches/ directory and use
criterion. A reproducible runner with metadata capture and optional
flamegraph generation is at scripts/bench.sh:
scripts/bench.sh --quick # smoke test (~ a minute total)
scripts/bench.sh # full criterion run (~ a few minutes)
scripts/bench.sh --flamegraph # generate per-bench SVG flamegraphs
scripts/bench.sh --bench pack_codec # one bench only
Output goes to bench-results/<host>-<UTC-timestamp>/ with a parsed
summary.txt, criterion's HTML reports, and a metadata.txt capturing
rustc version, kernel, CPU, and git rev for run-to-run comparison.
Headline numbers on a Ryzen 7 laptop:
- Pack decode at 10 × 1 MiB entries: ~2.3 ms (4.3 GiB/s).
- Blob serialize + BLAKE3 at 1 MiB: ~190 µs (5.1 GiB/s).
- Textual three-way merge of a 100 KiB document: ~4.6 ms.
Pack encoding is the throughput floor at ~380 MiB/s — bottlenecked by zstd level 3 on incompressible data.
Documentation
doc/technical-report.md— Distribution document. What LeVCS is, how to use it, and how it differs from / improves upon git. Targets technical evaluators and the workflow-spec reader.deploy/README.md— Comprehensive VPS deployment walkthrough.spec/— The protocol specification and trust-root revision. Currently kept private; ask the maintainer for a copy.
Contributing
This is a young project. The most useful contributions right now are:
- Trying it. Run
levcs initon a real project, push to a local instance, and report friction. - Workflow design. The next major piece of work is the workflow spec — PR/review surface, issues, CI conventions. Discussion welcome.
- Plugin handlers. The wasm plugin protocol exists; concrete handlers (e.g. protobuf, SQL migrations) are needed to validate it.
- Tightening CI. The
fmtandclippyGitHub jobs are informational; flipping them to gating would close a small but real quality gap.
Please open an issue or reach out before starting non-trivial work so we can coordinate.
License
Released under the Apache License 2.0 — see LICENSE for the
full text.
Citation
If LeVCS supports academic work, please cite the v0.1.0 release. A formal citation entry will land with the workflow spec; in the meantime a repository-URL reference is fine.