System Constants

Hard-coded constants used across the XE network. Every value below is traceable to a named constant in the xeprotocol/core source; the Go node and the embedded web UI must agree on all of them.

Units and supply

Constant	Value	Source
`AssetXE` / `AssetXUSD` decimals	6	`core/amount.go`
`UnitsPerToken`	1,000,000	`core/amount.go`
`MaxMemoBytes`	64 bytes	`core/memo.go`
`GenesisSupply`	42,000,000 XE (4.2×10¹³ µXE)	`core/genesis.go`

On-chain amounts — balances, send amounts, lease cost and stake, pending sends — are uint64 micro-units: 1 XE = 1_000_000 µXE, and the same for XUSD. They travel on the wire as plain JSON numbers, not strings. Where integer division on an amount cannot be avoided, the rounding policy is always round up (ceilDiv, core/ledger.go).

Memos are allowed on send and burn blocks only, and must be valid UTF-8 of at most 64 bytes.

Proof of work

Constant	Value	Notes
`core.DefaultDifficulty`	`0xfffff80000000000`	~2M expected attempts, ~1s on a single core
`core.TestDifficulty`	`0x0000000000000002`	Near-instant, for tests only
`chat.DefaultPoWDifficulty`	`0xffffc00000000000`	~2¹⁸ expected attempts, for chat envelopes

Block PoW and chat PoW are deliberately separate constants — they price different kinds of spam. A node advertises the thresholds it enforces as hex strings in GET /node (pow_difficulty, chat_pow_difficulty); "0" means PoW is disabled. Clients should read them from the node rather than hardcoding.

See Proof of Work for algorithm details.

Timing

Constant	Value	Used by
`DefaultTimestampWindow`	±1 hour	Block timestamp validation
Vote window (`voteWindowNanos`)	±5 minutes	Vote acceptance
`DefaultMaxAttestationSkew`	±10 minutes	Lease attestation validation (genesis-pinnable)
`chat.MaxEnvelopeSkew`	±5 minutes	Chat envelope freshness
`fallbackDelay`	10 seconds	Fallback conflict resolution after detection
`lockStabilityWindow`	3 seconds	Delay before the 67% converge-quorum commit-lock may form
Stale conflict sweep	15 seconds	Periodic conflict re-drive and cleanup
`revoteBackoff`	15 seconds	Minimum interval between sweep-driven converge re-emits
`phantomEvictionDelay`	30 seconds	Eviction of unbacked phantom candidates
`phantomUnretrievableTimeout`	10 minutes	Drop deadline for a live but unretrievable phantom
`failedPromotionTTL`	30 seconds	Quarantine for a winner that failed full promotion
`periodicSyncInterval`	10 seconds	Frontier sync interval
`syncCooldown`	5 seconds per peer	Per-peer sync throttle
Bootstrap watchdog	30 seconds	Re-dial interval for disconnected bootstrap peers
Directory TTL	30 minutes	Account directory entry expiry

[!INFO] Timestamp windows The block timestamp window (±1 hour) is intentionally generous to accommodate clock drift between nodes. Votes use a tighter ±5 minute window because representatives are expected to have reasonably synchronized clocks.

Size limits

Protocol limits

Constant	Value	Description
`maxConflictHashes`	10	Maximum competing block hashes per conflict
`maxPendingVotesPerConflict`	10	Votes buffered for a not-yet-known conflict
`MaxAttestationsPerBlock`	20	Maximum timekeeper attestations per lease block
`MaxGossipMessageSize`	262,144 bytes (256 KB)	Maximum gossip pubsub message
`maxSyncRequestBytes`	1 MiB	Maximum sync request payload
`maxSyncResponseBytes`	10 MiB	Maximum sync response page
`maxTotalBlocks` / `maxServerBlocks`	10,000 per session	Blocks transferred in one sync session
`maxFrontiers`	10,000	Frontier entries honoured in a sync request
Sync page size	64 default, 256 max	Blocks per sync response page

State chain limits

Constant	Value	Description
`MaxKeyLength`	128 bytes	Maximum key length for KV operations
`MaxValueSize`	65,536 bytes (64 KB)	Maximum value size for KV operations
`MaxBlockSize`	262,144 bytes (256 KB)	Maximum serialized state chain block

Messaging limits

Constant	Value	Description
`MsgMaxRequestSize`	65,536 bytes (64 KB)	Maximum `/xe/msg/1.0.0` request
`MsgMaxResponseSize`	65,536 bytes (64 KB)	Maximum `/xe/msg/1.0.0` response
`chat.MaxMessageBytes`	8,192 bytes (8 KiB)	Maximum chat message body

Lease economics

[!WARNING] Pre-mainnet values These are the constants compiled into core/ledger.go today, on a testnet-only network. They may still change before mainnet. See Cost Model.

Constant	Value	Description
`LeaseVCPURate`	20,000 µXUSD / vCPU / hour	Per-vCPU cost
`LeaseMemGBRate`	10,000 µXUSD / GB / hour	Per-GB memory cost
`LeaseDiskGBRate`	1,000 µXUSD / GB / hour	Per-GB disk cost
`LeaseStakeDivisor`	5	Stake = ⌈cost / 5⌉, minimum 1 µXUSD
`LeaseMaxDuration`	31,536,000 seconds	Longest allowed lease (365 days)

Cost is computed in whole hours (partial hours round up) and whole GB of memory (partial GB round up), then scaled by the provider's price multiplier, which is carried ×1000 (1000 = 1.000×) and ceiling-divided back out.

[!EXAMPLE] Cost calculation The worked target from core/ledger.go: 1 vCPU, 1 GB memory, 10 GB disk for 1 day at a 1.000× multiplier.
perHourMicro = 1×20_000 + 1×10_000 + 10×1_000 = 40_000 µXUSD/hour
hours        = 24
costMicro    = 40_000 × 24 = 960_000 µXUSD   (= 0.96 XUSD)
stake        = ceil(960_000 / 5) = 192_000 µXUSD

The XE emitted to the provider on settlement is not equal to the cost: it is ceil(cost × R_capped / 1000), where R_capped is the epoch's emission ratio (scaled ×1000) locked into the lease_accept block. See Cost Model and Economics for the emission curve.

Lease timing

Constant	Mainnet default	Description
`DefaultLeaseMinDuration`	60 seconds	Shortest allowed lease
`DefaultLeaseSettleGrace`	1 hour	Expiry → end of the provider settle window
`DefaultLeaseForceSettleGap`	25 minutes	Dead zone before the consumer force-settle window opens
`DefaultLeaseEscrowExpiry`	365 days	Expiry → escrow burn deadline
`DefaultLeaseArchiveGap`	1 hour	Local GC delay past the consensus deadline

Force-settle becomes eligible at expiry + LeaseSettleGrace + LeaseForceSettleGap — 1 hour 25 minutes after expiry on the defaults above.

[!IMPORTANT] Lease timing is pinned in genesis These are the production (mainnet) defaults. A network may override any of them in its genesis block, which is where every node gets its values from — a compressed test network is a different genesis, not a different binary. Read a live network's effective values from GET /node (lease_timing), not from these constants.

Performance certificates

Constant	Value	Description
`BenchmarkIterations`	375,000,000	Sequential SHA-256 hash chain
`MemoryTableSize`	8,388,608	Memory table entries (256 MB at 32 bytes each)
`MemoryReads`	1,000,000	Sequential-dependency random reads from the memory table
`WorkloadVersion`	3	Benchmark algorithm version (increment on changes)
`CertificateValidity`	7 days	How long a certificate is valid after issuance

See Performance Evaluation for benchmark and scoring details.

Consensus

Constant	Value	Description
Quorum threshold	67%	Delegated weight in final votes required to finalize
Connection manager low water	100 peers	Minimum peer target
Connection manager high water	400 peers	Maximum peer target
Connection grace period	1 minute	New connection protection window

API

Constant	Value	Description
Read rate limit	200 req/sec, burst 1,000	Per-IP bucket for `GET` requests
Write rate limit	10 req/sec, burst 50	Per-IP bucket for `POST` requests
`rateLimiterTTL`	5 minutes	Idle eviction for a per-IP limiter entry
`maxRateLimiterIPs`	100,000	Cap on tracked IPs before new ones are rejected
`maxRequestBytes`	1 MiB	Maximum HTTP request body
Page limit	100 default, 1,000 max	`?limit=` on paginated endpoints
Default API port	8080	`xe node --api-port`
Default libp2p port	9000	`xe node --port`
Default UI port	8000	`xe node --ui-port`
Default CORS origin	`http://localhost:3000`	Used when `--cors-origin` is unset

Reads and writes get separate per-IP buckets: browsing the chain must never trip the limiter, while POST mutations (block submission, chat, directory registration) are held to a much tighter rate.