chains/LLM.md

chains

Org: luxfi · Ecosystem: lux · Path: /Users/a/work/lux/luxfi/chains Origin: https://github.com/luxfi/chains.git

Discovery

This file (CLAUDE.md) is the canonical agent-facing readme; LLM.md is a symlink to it. Update either name and both stay in sync.

Where to look first

• README.md — human-facing overview (if present)
• package.json / Cargo.toml / pyproject.toml / go.mod — language & deps
• .github/workflows/ — CI surface
• docs/ — extended docs (if present)

Canonical chain roster (LP-0130)

The topology, UTXO ownership rule, and cross-chain fee model are normatively specified by LP-0130 (Chain Topology, UTXO Ownership, and Fee Model). Read that LP before touching any VM's fee/settlement path.

Only P (in node/vms/platformvm) and X (in node/vms/xvm) are canonical UTXO state machines. Every VM in THIS repo is a domain-execution chain that MUST consume UTXO settlement via the chains/fee primitive funded from X.

Dir	Letter	Role	LP
evm/	C	Contract / EVM account state	LP-1200
dexvm/	D	DEX matching + settlement receipts	LP-9000
quantumvm/	Q	Finality-cert / Quasar aggregation. No user-payable blockspace (validator obligation, LP-0130 §6)	LP-1300
zkvm/	Z	Rollup / private commitment + nullifier. Shielded supply is an X-escrow wrapper (LP-0130 §2, I-5)	LP-8000
aivm/	A	Inference receipt + attestation. Rides B's settlement engine (LP-0130 §9)	LP-5000
bridgevm/	B	Cross-chain message lifecycle. Fees deducted from bridged amount (LP-0130 §8)	LP-6000
mpcvm/	M	MPC signing / custody. Service fees paid by originating chain (LP-0130 §7); no user M-balance	LP-7100
fhevm/	F	Confidential-compute coordination: ciphertext handles, access permits, threshold decryption	LP-8200
mpcvm/fhe/	—	FHE runtime library — a package inside mpcvm, wrapped by fhevm/, not itself a chain	LP-8200

Deployment reality (probed on mainnet 96369, platform.getBlockchains). Ten chains are live: P X + C D Q Z A B G K. M and F are NOT deployed; both now build and ship a plugin binary, and neither has a chain registered on any network. make produces build/mpcvm and build/fhevm, and luxd's --plugin-dir scan (node/node/vms.go OptionalVMs) finds each under the CB58 of its vmID — qCURact1n41FcoNBch8iMVBwc9AWie48D118ZNJ5tBdWrvryS for M, n6sSsSfbpQBrU9sY4R29U6z8VrmnTo2CntW6da4rRS7qmnGdv for F.

F-Chain (fhevm/)

F is the coordination plane for confidential compute, modelled on keyvm/: the chain of record for encrypted values that it never holds. It stores a ciphertext's 32-byte handle, the digest of the off-chain body, its owner, the capability permits granted over it, and the threshold decryptions asked for and answered. It stores no ciphertext body, no plaintext, no FHE secret key and no decryption share — fhevm/invariant_test.go proves that by walking the type graph and scanning the package source.

Six operations, each fee-settled through consensus and priced by scheme and ring dimension (fhevm/gas.go): register a ciphertext, grant a permit, revoke a permit, request a decryption, attest its result, advance the epoch. The last two are threshold decisions — a request completes when Threshold distinct members of the epoch's committee attest the same result handle, and an epoch installs when Threshold members of the sitting committee attest the same successor. A member votes once, and votes are tallied per value, so one member naming a false result delays nothing and pays for the attempt.

F wraps mpcvm/fhe/ rather than restating it: its records embed that package's types and its public parameters come from DefaultThresholdConfig(). It does not use that package's Registry, which stamps records with time.Now() — right for the off-chain daemon it was written for, wrong here, because two validators replaying one block would store different bytes and return different answers to the same query. F owns its persistence and every timestamp it writes comes from the accepting block.

A transaction that fails authorization REVERTS: it burns its fee, consumes its nonce, and changes nothing. Authorization is decided once, in Accept, because an earlier transaction in the same block can change the state a later one is judged against — so a verdict reached in Verify can differ from the one reached at application, and a block every validator certifies and no validator can apply halts the chain at that height. Verify therefore asks only that a block is well-formed, authentic, correctly ordered and paid for; batch.admit is that rule, and BuildBlock runs the same rule and simply leaves out what does not fit, so a proposer cannot build a block its own Verify would reject.

Two things F does not have, and the one change that gives both

F commits no state root, and it cannot verify a child of a block it has not yet accepted (the second is shared with keyvm/). Both come from the same gap: there is one state layer, so Verify reads committed state and a proposer cannot know its post-state until Accept.

• A root checked only at Accept would be worse than none — a wrong root in a proposed block would pass Verify everywhere and fail Accept everywhere, which is a halt an adversary triggers at will.
• Verifying b2 on top of an unaccepted b1 needs b1's post-state, which is the same missing layer.

The fix for both is a state layer per in-flight block (versiondb chains, with the record caches moving under it). Until then, determinism is enforced from outside consensus by replay_test.go, which replays a chain onto independently built nodes running different clocks and requires their databases to be byte-identical.

Chain time is monotone and bounded ahead of the verifier's clock by MaxFutureSkew; within [parent timestamp, clock + skew] the proposer still chooses, so a permit that lapsed during a gap in block production can authorize one request in the block that closes the gap. TestH2_ProposerFreedomIsExactly‑ TheGapSinceTheLastBlock measures exactly that. Removing it means counting lifetimes in block heights, which no proposer can rewind — a change to the grant API, not a patch.

T-Chain is gone entirely — LP-1340 dissolves it with zero remainder (threshold signing → M, FHE → F, cross-chain messaging/teleport → B). There is no teleportvm here and no teleportvm VM ID in luxfi/constants.

Service VMs (not canonical primary chains under LP-0130):

Dir	Letter	Purpose
schain/	S	S3-style object storage (on-chain metadata, off-chain blob)
keyvm/	K	Key registry / cryptographic algorithm addressing
identityvm/	I	DID / identity
graphvm/	G	Graph indexing / GraphQL surface
relayvm/	R	Relay message queue
oraclevm/	O	Oracle price / data feed

Service VMs MAY have domain state and MAY charge fees, but MUST fund their fee balance from X and MUST NOT hold canonical UTXO asset supply.

Fee settlement primitive — chains/fee

chains/fee/{balance,meter,settle,ledger}.go is the shared admission → meter → burn primitive every non-P/X VM in this repo uses. Its Burn is a native LUX burn (no coinbase credit) that reconciles against X-side fee escrow at the epoch fee root (LP-0130 §4). chains/fee/doc.go is the design intent.

Σ-escrow invariant

At every Q checkpoint (LP-0130 I-8):

Σ (non-P/X fee balances)  ==  Σ (X-side fee escrow)

Drift is a finality-blocking fault. This is the audit invariant every VM's epoch-fee-root emission and reconciliation path exists to satisfy.

VMs in this repo

Each *vm/ dir is a self-contained block.ChainVM plugin. dexvm is the reference for VM structure + commit discipline (dual-DB: durable baseDB + per-block versiondb; one db.CommitBatch() at block Accept).

• schain (schain/) — the Lux S-Chain storage VM, forked from dexvm's structure. VMID = ids.ID{'s','c','h','a','i','n'} (dexvm's byte pattern). M0 (DONE): one mutation PutManifest{bucket,object,fileIds,size,etag} round-trips through a real Lux block (BuildBlock→Verify→Accept) and commits the manifest to a real on-disk zapdb in ONE atomic batch at Accept; GetManifest returns it only after Accept. Commit discipline copied verbatim from dexvm/vm.go:1194 (acceptBlock), minus the cross-chain shared-memory leg a storage VM does not have — accept reduces to CommitBatch() + batch.Write() + db.Abort(). State = typed manifest accessors over versiondb (no protobuf; JSON value bodies, prefix keys), mirroring dexvm/state/state.go. Tx wire = type-byte + JSON, one codec (mirror dexvm/txs/tx.go). No blobs/pinning/ networking yet — that is M1+. Test: schain/schain_test.go drives the genuine VM↔engine contract (SubmitTx→ToEngine PendingTxs→BuildBlock→Verify→Accept) over a REAL zapdb.New(t.TempDir(),…); proves staged-not-durable before Accept, durable after, and Reject→Abort discards. M1 (DONE): TWO parts. PART A — manifest STATE ROOT (the multi-validator safety prerequisite M0 omitted): state.Root() hashes the committed manifest keyspace deterministically via the zapdb prefix iterator NewIteratorWithStartAndPrefix(nil, prefixManifest), folding each entry length-prefixed (len(k)||k||len(v)||v) in lexicographic key order (mirror of dexvm/state/state.go:395 StateHash, narrowed to the one keyspace; last-block pointer excluded — it is consensus binding folded via blockHash/height, not object state). VM.computeStateRoot folds blockHash+height with state.Root() (mirror dexvm/vm.go:1260); ProcessBlock stamps it into BlockResult.StateRoot (mirror dexvm/vm.go:584). The root travels in the block HEADER (new 32-byte field after parentID; block id commits to it) and Block.Verify recomputes it and REJECTS a mismatch (errStateRootMismatch) + Aborts staged writes — this is the >1-validator safety gate dexvm computed but never compared. Tests (schain/stateroot_test.go): determinism across write order, change-sensitivity (object set / etag / size / fileIds each move the root), and Verify-rejects-tampered-root. PART B — S3 OBJECT path, on-chain-metadata / off-chain-blob split proven end to end (schain/object/): Store.PutObject streams the blob to a Volume (OFF chain) → fid, then commits only PutManifest{bucket,object,[fid],size,etag} to the VM through a real block (ON chain); GetObject reads the manifest back and reconstructs the blob from the volume. object.Volume is the SEAM (Write(blob)→fid, Read(fid)→blob); M1 satisfies it with a faithful in-memory MemVolume whose fid shape mirrors hanzo/s3's needle.FileId (volumeId,needleIdCookie) and whose etag is base64(md5(blob)) (= hanzo/s3 ContentMd5). M2 PLUG POINT (marked in object/volume.go): swap MemVolume for a thin adapter over github.com/ hanzoai/s3 s3/operation.SubmitFiles (assign volume + stream needle → .Fid) and a needle GET — nothing in the VM or object.Store changes. Kept inside chains/schain (not importing the hanzoai/s3 module into luxfi/chains) to respect the org/module boundary while proving the exact data model. Test (schain/object_roundtrip_test.go): asserts the blob bytes appear in NO accepted block (bytes.Contains over blk.Bytes()) and the block stays manifest-small (<4KiB for a 68KiB blob), the manifest IS on chain, and GET byte-reconstructs.

Test/build env gotcha (macOS)

The whole chains test suite links CGO deps that need -lresolv; the CLT cc fails with library 'resolv' not found unless the macOS SDK syslibroot is set. Run tests with SDKROOT="$(xcrun --show-sdk-path)" go test ./schain/.... This affects dexvm and every other VM here too — it is NOT schain-specific.

How a block becomes fact: chain/

Every chain here advances the same way, so it is written once, in chain/. A chain package declares what it IS — its transactions, its records, its authorization rules — and nothing about how a block lands.

chain.Store[B] holds a chain's committed database, the versiondb view every block writes through, the blocks in flight, the accepted tip, and the block the engine prefers. Store.Accept runs the block's Write, then puts the block, its height entry and the tip pointer, then commits ONCE. Any failure aborts the view, rebuilds the chain's caches from committed state, and leaves the tip where it was. Publish runs only after the commit.

That split is the whole point. Write can fail and is discarded whole; Publish cannot fail and only ever sees durable state. Five chains here used to write with individual db.Put calls that each returned early, with the status and the tip already moved — so a failure left the chain believing a block it had only half applied, with no way back. On M-Chain it was worse than a loss: the duplicate guards in PutKey/PutCeremony then refused the records the failed block had already written, so that block could never be applied again and the chain was wedged at that height.

• chain.Block is not the engine's block interface. It is ID/Height/ Bytes/Write/Publish and nothing more, because Z-Chain decides in two shapes: a linear block and a DAG vertex with several parents and no timestamp. Both change state the same way. A chain with one shape parameterises the store over its own type (Store[*Block]) and never asserts; Z-Chain uses Store[chain.Block] and says which it got.
• The store's lock is the chain's lock. In-flight blocks under a second mutex is one map with two owners, which in Go is a fatal throw. A VM's own operational state — B-Chain's signer set, transfers and release plumbing — is NOT the chain's state and keeps its own lock; the order is written where the locks are, and it is always the chain's first.
• Propose hands over the parent block, not the tip id, so a build never calls back into the store it is already inside.
• chain.Pool[T,K] derives its claim set from its queue and rebuilds it whenever the queue shrinks, so a claim cannot outlive the entry that made it. It carries the latch (see below).
• chain.Floor(networkID) / chain.Closed() replace each VM's newFeePolicy; the zero chain.Fee admits nothing, so a chain that forgets to declare one refuses every caller.
• chain.Factory[VM] replaces each VM's factory. A factory-built VM holds nothing; Initialize does all of it.

On chain.Store: identityvm, zkvm, bridgevm, mpcvm. keyvm and fhevm already had the discipline in their own code and are the shape it was generalised from; schain and quantumvm are partway. graphvm is NOT on it and does not need to be — it writes nothing at all, so there is no partial state to have.

Sibling repos

See the org-level LLM.md at /Users/a/work/lux/luxfi/LLM.md for the full inventory of sibling repos and inter-repo dependencies.

Telling consensus there is work

Consensus calls WaitForEvent and builds nothing until it returns, so a VM that accepts work has to report it. There is one way to do that: vm.Latch in github.com/luxfi/vm. Signal() says there is work, WaitForEvent(ctx) blocks until there is, and signalling twice before the signal is taken is the same as once — a builder needs to know that there is work, not how much, so a burst coalesces into one build. The zero value is usable, so whatever owns the pending work holds one.

Put the latch on the pool, not the VM. The pool is what learns work arrived, whichever path it came by, so it covers internal callers as well as the HTTP handler and the VM's WaitForEvent is one line. zkvm, quantumvm, identityvm, bridgevm, aivm, keyvm and mpcvm all work this way.

Two chains deliberately do not, and both are correct:

• schain and dexvm notify on the ToEngine channel they receive in vm.Init instead, and park on the context. That is the other of the two ways a VM can report work, and a VM needs one. Before changing a parked WaitForEvent, check which: grep -rn "toEngine <-" <vm>/*.go.
• graphvm builds no blocks at all. G-Chain indexes what other chains have already agreed, so it holds no state of its own to agree on; a block there would carry a query result, which a peer recomputes, or a schema, which is local configuration. BuildBlock declines with errReadOnlyChain.

B-Chain: where a bridge request comes from

B learns of a bridge from the source chain's own Locked events, not from its API. watch.go polls each configured chain, reads the range it has not read yet, and turns each lock into a pending request keyed by the transfer's canonical digest — the same value M signs and the destination gateway keys its replay guard by, so two chains reusing a nonce cannot collide and the same lock read twice is the same request.

It reads twelve blocks behind the head, so a lock a reorg takes back never becomes a request; it bounds one pass, so a backlog is asked for in pieces; and a chain it cannot reach keeps its cursor rather than skipping that chain's blocks. The depth a lock is buried at rides along as its confirmation count, which is what BuildBlock gates on.

The bridge's API is the JSON-RPC service in rpc.go, and bridge_health reports what the node can do: a node with no chains wired is not a relayer and is healthy, while one that is configured to relay but cannot attest says so.