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A custom Solana validator client written in Zig.

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What is Vexor?

Vexor is an independent Solana validator client written from scratch in Zig. It is not a fork of Agave or Firedancer — it is a ground-up implementation of the Solana consensus and execution protocol.

Currently running on testnet:

• Identity: 3J2jADiEoKMaooCQbkyr9aLnjAb5ApDWfVvKgzyK2fbP
• Server: AMD EPYC 9374F (32 cores), 503 GB RAM, 3.6 TB NVMe, Broadcom 10G NICs
• Epoch 933 — actively voting, zero STATE-DIVERGENCE, votes landing on-chain
• 36 leader slots assigned for epoch 934

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Current Status

Component	Status
Gossip / TVU / TPU	✅ Running
Shred assembly (AF_XDP copy-mode)	✅ Running
Transaction replay	✅ Running
Bank hash (SIMD-215 two-step LtHash)	✅ Correct
Native SBPF v0 VM	✅ Running (no C dependency)
Vote submission (TowerSync)	✅ Landing on-chain
Block production (leader slots)	✅ Implemented
VEXstore LSM storage engine	🔧 In development
CPI (cross-program invocation)	🔧 RPC shadow bridge (interim)
Mainnet	📋 Planned

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Architecture

┌─────────────────────────────────────────────────────────────────┐
│                         VEXOR VALIDATOR                          │
├──────────────┬──────────────┬─────────────────┬─────────────────┤
│   NETWORK    │   CONSENSUS  │    EXECUTION     │    STORAGE      │
│              │              │                  │                 │
│  AF_XDP      │  Tower BFT   │  SBPF v0 VM     │  AccountsDb     │
│  copy-mode   │  Fork Choice │  (native Zig)   │  (in-memory +   │
│  10G NICs    │  Vote Submit │                  │   NVMe)         │
│              │              │  RPC Shadow BPF  │                 │
│  Gossip      │  Leader Sched│  (CPI fallback)  │  VEXstore LSM   │
│  TVU / TPU   │  Epoch Stakes│                  │  (WiscKey-style)│
│  Turbine     │              │  ELF Loader      │                 │
└──────────────┴──────────────┴─────────────────┴─────────────────┘

Native Zig SBPF VM

Vexor includes a complete native Zig implementation of the Solana BPF virtual machine — no Firedancer C library, no external dependencies:

• Full SBPF v0 instruction set: all ALU64/ALU32, load/store, jump, and LDDW instructions
• Correct Solana memory model: four virtual address regions (0x100000000 program, 0x200000000 stack, 0x300000000 heap, 0x400000000 input), each with host-pointer translation and write-protection
• 27 syscalls: sol_log_, sol_memcpy_, sol_memcmp_, sol_memset_, sol_sha256, sol_keccak256, sol_blake3, sol_create_program_address_, sol_try_find_program_address, and more — all syscall IDs computed as murmur3_32(name, 0) and verified against Agave
• CPI fallback: sol_invoke_signed returns CpiRequired; the executor transparently falls back to an RPC shadow that fetches confirmed account state for that slot

Bank Hash

Implements SIMD-215 two-step formula:

step1 = SHA256(parent_hash || sig_count_u64_LE || last_blockhash)
bank_hash = SHA256(step1 || lthash_2048_bytes)

LtHash uses Blake3 XOF → 2048 bytes per account, with element-wise u16 add/subtract for account updates. Matches the network exactly — zero STATE-DIVERGENCE since deployment.

Storage

• Legacy backend: in-memory HashMap with NVMe persistence, used in production
• VEXstore: custom WiscKey-inspired LSM engine (2,500+ lines), being integrated as primary backend. Separates keys (index in SSTable) from values (NVMe value log), avoiding write amplification on large account data

Networking

AF_XDP copy-mode on enp5s0f0np0 (Broadcom BCM57416, 10G). Zero-copy mode (xsk_umem_register) is not supported by this NIC's bnxt_en driver — copy-mode is the correct configuration. Shred repair runs on enp5s0f1np1 (.155).

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Hardware

The testnet validator runs on dedicated bare metal:

Component	Spec
CPU	AMD EPYC 9374F (32 cores, Zen 4)
RAM	503 GB DDR5
NVMe	3.6 TB
NICs	Dual Broadcom BCM57416 10G (enp5s0f0np0 + enp5s0f1np1)
OS	Debian 12, kernel 6.12.74
Compiler	Zig 0.14.0

CPU pinning: cores 6–19 for Vexor (14 cores), cores 2–5 for IRQ affinity.

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Build

# Standard build (for your local machine)
zig build -Doptimize=ReleaseFast

# Production build (AMD EPYC / znver4)
zig build -Doptimize=ReleaseFast -Dcpu=znver4

# Optional: future Firedancer VM comparison (not required)
zig build -Doptimize=ReleaseFast -Dcpu=znver4 \
    -Dfiredancer_src=/path/to/firedancer/src

# Optional build flags
-Dstorage_backend=vexstore    # use VEXstore as primary backend
-Dvexstore_shadow=true        # shadow writes to VEXstore alongside legacy

Requirements: Zig 0.14.0. No other build dependencies.

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Running on Testnet

./vexor-launch.sh testnet

Key flags used in production:

--bootstrap --testnet
--identity ****
--vote-account ****
--ledger /mnt/ledger/vexor-testnet
--accounts /mnt/ramdisk/vexor-testnet
--snapshots /mnt/snapshots/vexor-testnet
--public-ip 38.58.183.154
--gossip-port 8001 --tvu-port 8003 --repair-port 8002
--repair-bind-addr 38.58.183.155
--expected-genesis-hash 4uhcVJyU9pJkvQyS88uRDiswHXSCkY3zQawwpjk2NsNY
--known-validator [4 testnet validators]
--entrypoint [3 testnet entrypoints]
--enable-af-xdp --interface enp5s0f0np0
--enable-fec-recovery --enable-io-uring
--limit-ledger-size 50000000

Do not use --xdp-zero-copy — not supported by bnxt_en driver.

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Monitoring

TPS Metrics

Vexor logs a rolling 60-slot TPS window every minute:

[METRICS] slot=397856000 | replay_TPS=4230 tx/s (last 60 slots, 101520 txns) |
          net_est=3750 tx/s | lifetime: 2847300 txns across 14230 slots |
          votes=28460 blocks=4 bad_shreds=0

• replay_TPS: how fast Vexor's SBPF VM processes transactions (wall-clock)
• net_est: estimated network-wide TPS from avg transactions per slot ÷ 0.4s
• lifetime: cumulative totals since process start

Vote Confirmation

# Watch identity balance drain (5,000 lamports per vote)
solana balance 3J2jADiEoKMaooCQbkyr9aLnjAb5ApDWfVvKgzyK2fbP --url testnet

# Watch Vexor logs
tail -f /home/davidb/vexor_testnet.log | grep -E "VoteSubmitter|METRICS|HASH"

Log Patterns

Pattern	Meaning
[VoteSubmitter] Attempting vote for slot N	Vote being submitted
[METRICS] replay_TPS=N	Rolling TPS report (every 60 slots)
[HASH-COMPARATOR] MATCHES	Bank hash matches network
[RpcShadowBpf] N BPF accounts tracked, N changed	CPI fallback active for slot
[BlockProducer] WE ARE LEADER	Leader slot, producing block
[STATE-DIVERGENCE]	❌ Should not appear — means bank hash mismatch

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Roadmap

Near term

• Full CPI (cross-program invocation) in native Zig VM — eliminates RPC shadow dependency
• VEXstore as primary storage backend (flat index elimination complete)
• SIMD-0161 (SBPF v1) instruction set support
• Prometheus /metrics HTTP endpoint

Medium term

• Mainnet readiness: stake-weighted quality-of-service, stake delegation
• Native secp256k1 recover syscall (currently returns error code 1)
• Alpenglow consensus (SIMD-0236) — faster finality
• QUIC TPU ingress

Long term

• Full hardware zero-copy XDP (requires NIC with XDP_SETUP_XSK_POOL support)
• Multi-validator cluster testing
• Jito MEV integration

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Key Files

src/
├── runtime/
│   ├── bank.zig              Bank state, LtHash, freeze(), RPC shadow injection
│   ├── replay_stage.zig      Shred assembly, TX replay, TPS metrics
│   ├── bootstrap.zig         Startup, snapshot load, vote loop
│   ├── vote_state_serde.zig  VoteState V1/V2/V3/V4 round-trip serde
│   ├── rpc_shadow_bpf.zig    CPI fallback: fetch confirmed BPF state from RPC
│   └── bpf/
│       ├── interpreter.zig   Native Zig SBPF v0 VM (virtual address memory model)
│       ├── syscalls.zig      27 syscalls, murmur3_32 dispatch, Zig 0.14 crypto
│       ├── sbpf_executor.zig Serialise accounts → run VM → deserialise mutations
│       └── elf_loader.zig    SBPF ELF → combined rodata buffer + entry_pc
├── consensus/
│   ├── tower.zig             Tower BFT, lockouts, timely vote credits (SIMD-033)
│   └── fork_choice.zig       Heaviest-subtree stake-weighted fork selection
├── storage/
│   ├── accounts.zig          AccountsDb, LtHash cache, top_votes, SIMD-0084
│   └── vexstore.zig          VEXstore WiscKey LSM engine (in development)
└── crypto/
    └── lthash.zig            Blake3 XOF → 2048-byte LtHash, u16 element add/sub

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Credits & Attribution

Vexor is an independent implementation of the Solana protocol. In studying the protocol, the following open-source projects were invaluable references:

• Firedancer (Jump Trading, Apache-2.0) — virtual machine architecture, memory region layout concepts, syscall dispatch approach
• Agave / solana-rbpf (Solana Labs, MIT) — virtual address constants (MM_PROG_START etc.), calling convention, SBPF v0 specification
• SIG (Syndica, MIT) — Zig patterns for Solana protocol implementation

Vexor's code is written from scratch in Zig. All syscall IDs are computed independently via murmur3_32(name, 0). The Solana protocol specification (SIMDs) are the authoritative reference for all consensus-critical behaviour.

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Built with ❤️ and Zig. Running on Solana testnet.