Avalanche X-Chain and P-Chain networks

The Avalanche family serves the primary network's two UTXO chains through @avalabs/avalanchejs 5 (npm install @avalabs/avalanchejs): avalanche-x, the X-Chain (AVM), and avalanche-p, the P-Chain (PlatformVM), each on mainnet (the default) and fuji. The C-Chain is an EVM chain: it stays avalanche, in the EVM family. AVAX has 9 decimals here (a bigint amount is in nAVAX), not the C-Chain's 18.

Chain	Networks (network id)	Fees	Memo	Address
avalanche-x	mainnet (1), fuji (5)	fixed, 0.001 AVAX per transaction (avm.getTxFee)	yes, up to 256 bytes	X-avax1…, X-fuji1…
avalanche-p	mainnet (1), fuji (5)	dynamic gas price (Etna)	no (refused since Durango)	P-avax1…, P-fuji1…

• A provider and an indexer. provider is a node's chain API, JSON-RPC at the chain's own URL (https://node.example/ext/bc/X, …/ext/bc/P). AvalancheGo says whether a transaction is accepted but not which block holds it, so the Avalanche Data API is the required indexer: it locates a transaction's block, which the node then proves under the proof quorum, and it serves history. A transaction the indexer does not know yet is looked for in the node's newest 16 blocks. public names Ava Labs' public API and the keyless Data API, for trying things out, not for production; glacier is the Data API with an apiKey, sent in the x-glacier-api-key header as a Secret. Every endpoint's health check reads the id of the chain's block at height 0, so an endpoint of another network or chain is refused.
• Finality. Snowman never reverts an accepted block: a transaction in an accepted block is final (finality: 1 confirmation), and waitForConfirmation proves it as soon as it is accepted. The X-Chain shows no mempool, so an issued transaction reads as not seen until it is accepted, usually within seconds.
• Spending. A transfer spends plain AVAX outputs the wallet signs alone (threshold 1, no lock), largest first, at most 128 per transaction, with change back to the sending address; the balance counts those outputs only (stake-locked, time-locked and multi-owner outputs are listed by ext.avalanche.listUnspent, not spent). Outputs held by another live Operation are left out. Every input is signed with the same secp256k1 signature, over the SHA-256 of the unsigned transaction; the id is known only after signing.
• Fees. The X-Chain fee is read under the proof quorum and every speed pays it. The P-Chain fee is the transaction's gas times a gas price: the endpoint's current price times 1.1 (slow), 1.5 (normal) or 2 (fast), or { gasPrice } (nAVAX per gas). Two options bound them: options.maxFee (default 0.1 AVAX) and, on the P-Chain, options.maxGasPrice (default 10,000). A P-Chain transaction that burns less than the price at the time it is verified is refused (FEE_TOO_LOW) and stays stalled until the price falls and it is sent again.
• No replace or cancel. AvalancheGo keeps the first of two conflicting transactions, and an accepted one is final.
• Broadcasts. A node's refusal never ends a transfer as TX_REJECTED: the driver checks every transaction before it is signed, so each refusal is refused (FEE_TOO_LOW or TX_REFUSED, with a fixed reason, never the node's text), and the transfer stalls with its inputs held, since the node may have relayed it. So one lying endpoint cannot free your outputs for a second payment. Never retry the payment as a new transfer (a new idempotency key): it spends other outputs, and both can be accepted. Repeat the call with the same key, or use rebroadcast; the transfer ends once a node accepts it, or failed (TX_REPLACED) once a transaction that spent one of its inputs is final.
• Reading. getTransaction, scans and history decode each plain AVAX output to one address as a transfer (out:<index>); the senders are the addresses the signatures recover to. An export, a staking or subnet transaction, a reward, an Avalanche native token or a multi-owner output makes the decoding partial. An X-Chain transaction accepted before the chain's linearization (April 2023) has no block and reads as not seen.
• Keys. The derivation path is BIP44's m/44'/9000'/0'/0/i. Avalanche wallets export an xpub on every network, so deriveAddress accepts one on Fuji too.
• Not yet. Avalanche native tokens (ANTs), cross-chain import and export, staking.
• Live checks (this repository). CRYPTO_AIO_INTEGRATION=1 runs the read-only checks in test/integration/avalanche.test.ts against Fuji (CRYPTO_AIO_IT_AVALANCHE_NETWORK=mainnet for mainnet); CRYPTO_AIO_IT_AVALANCHE_{X,P}_RPC_URL and …_INDEXER_URL point them at other endpoints.