update testnet deployments to new contract, improve DX

- Testnet contract address changed to 0x428c850be686E933DD641eE43574BA35f550c94c (same as mainnet)
- Add tUSDT pool to both Sepolia and BSC Testnet (verified on-chain)
- Update max amounts to uint128 max from new contract
- README Quick Start uses SEPOLIA_TESTNET preset instead of placeholder URLs
- Add chain preset reference table to README
- Improve seed validation error message with HKDF context
- Add JSDoc to WalletSessionInput.seed

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: niconiconi

README.md

@@ -25,30 +25,35 @@ pnpm add @ocash/sdk
 ## Quick Start
 
 ```ts
-import { createSdk } from '@ocash/sdk';
+import { createSdk, SEPOLIA_TESTNET } from '@ocash/sdk';
 
-// See demos/node/ocash.config.example.json for testnet URLs
 const sdk = createSdk({
-  chains: [
-    {
-      chainId: 11155111,
-      entryUrl: '<ENTRY_SERVICE_URL>',
-      ocashContractAddress: '<CONTRACT_ADDRESS>',
-      relayerUrl: '<RELAYER_URL>',
-      merkleProofUrl: '<MERKLE_PROOF_URL>',
-      tokens: [],
-    },
-  ],
+  chains: [SEPOLIA_TESTNET],
   onEvent: console.log,
 });
 
 await sdk.core.ready();
 await sdk.wallet.open({ seed: 'your-secret-seed-phrase' });
 await sdk.sync.syncOnce();
 
-const balance = await sdk.wallet.getBalance({ chainId, assetId });
+const balance = await sdk.wallet.getBalance({
+  chainId: SEPOLIA_TESTNET.chainId,
+  assetId: SEPOLIA_TESTNET.tokens![0]!.id,
+});
 ```
 
+Pre-configured chain presets exported from `@ocash/sdk`:
+
+| Preset | Chain | Chain ID |
+| --- | --- | --- |
+| `ETH_MAINNET` | Ethereum | 1 |
+| `BSC_MAINNET` | BNB Chain | 56 |
+| `BASE_MAINNET` | Base | 8453 |
+| `SEPOLIA_TESTNET` | Sepolia | 11155111 |
+| `BSC_TESTNET` | BSC Testnet | 97 |
+
+Also available: `MAINNET_CHAINS` and `TESTNET_CHAINS` arrays.
+
 ## Entry Points
 
 | Import               | Environment | Extra              |

src/crypto/keyManager.ts

@@ -11,7 +11,7 @@ const HKDF_INFO = 'OCash.KeyGen';
  * Derive a 32-byte seed from a human string using HKDF-SHA256.
  */
 const deriveSeed = (seed: string, nonce?: string): `0x${string}` => {
-  if (seed.length < 16) throw new Error('Seed must be at least 16 characters');
+  if (seed.length < 16) throw new Error('Seed must be at least 16 characters. Any passphrase, hex string, or random bytes will work — it is run through HKDF-SHA256 internally.');
   const ikm = utf8ToBytes(seed);
   const info = utf8ToBytes(nonce ? `${HKDF_INFO}:${nonce}` : HKDF_INFO);
   const okm = hkdf(sha256, ikm, undefined, info, 32);

src/deployments.ts

@@ -117,13 +117,13 @@ export const BASE_MAINNET: ChainConfigInput = {
 
 /**
  * OCash testnet deployment — Sepolia (Chain ID 11155111).
- * Pool: SepoliaETH.
+ * Pools: SepoliaETH, tUSDT.
  */
 export const SEPOLIA_TESTNET: ChainConfigInput = {
   chainId: 11155111,
   rpcUrl: 'https://sepolia.drpc.org',
   entryUrl: 'https://api.2.o.cash',
-  ocashContractAddress: '0x103B9fa1355709832DEB7ff3760017f3cc49A000',
+  ocashContractAddress: '0x428c850be686E933DD641eE43574BA35f550c94c',
   relayerUrl: 'https://relayer.sepolia.2.o.cash',
   merkleProofUrl: 'https://freezer.sepolia.2.o.cash',
   tokens: [
@@ -136,21 +136,33 @@ export const SEPOLIA_TESTNET: ChainConfigInput = {
       freezerPk: ['4669474039172149691654565526011752760208335185174811747074129322851928951709', '13559226903331282409026052744251929479054127336193904689356637527155192056962'],
       depositFeeBps: 0,
       withdrawFeeBps: 25,
-      transferMaxAmount: '400000000000000000',
-      withdrawMaxAmount: '400000000000000000',
+      transferMaxAmount: '340282366920938463463374607431768211455',
+      withdrawMaxAmount: '340282366920938463463374607431768211455',
+    },
+    {
+      id: '14880450956444241072894828158264802787637197896840919915927253631318375660820',
+      symbol: 'tUSDT',
+      decimals: 18,
+      wrappedErc20: '0xa88C08409342E95e5A05CB95f5EcC267E1F4f102',
+      viewerPk: ['16705602615272268567003522975712421097082383063417679753060534780702444376151', '14514464143093266825290311242522740387541372997639894559538766466467730361203'],
+      freezerPk: ['12575519572146277363559222067073217394207912146376135522069598095499837742570', '20535825957543427476664044300935290889134231934616628729189553228696621211842'],
+      depositFeeBps: 0,
+      withdrawFeeBps: 25,
+      transferMaxAmount: '340282366920938463463374607431768211455',
+      withdrawMaxAmount: '340282366920938463463374607431768211455',
     },
   ],
 };
 
 /**
  * OCash testnet deployment — BSC Testnet (Chain ID 97).
- * Pool: tBNB.
+ * Pools: tBNB, tUSDT.
  */
 export const BSC_TESTNET: ChainConfigInput = {
   chainId: 97,
   rpcUrl: 'https://data-seed-prebsc-1-s1.bnbchain.org:8545',
   entryUrl: 'https://api.2.o.cash',
-  ocashContractAddress: '0x103B9fa1355709832DEB7ff3760017f3cc49A000',
+  ocashContractAddress: '0x428c850be686E933DD641eE43574BA35f550c94c',
   relayerUrl: 'https://relayer.bsctestnet.2.o.cash',
   merkleProofUrl: 'https://freezer.bsctestnet.2.o.cash',
   tokens: [
@@ -163,8 +175,20 @@ export const BSC_TESTNET: ChainConfigInput = {
       freezerPk: ['4669474039172149691654565526011752760208335185174811747074129322851928951709', '13559226903331282409026052744251929479054127336193904689356637527155192056962'],
       depositFeeBps: 0,
       withdrawFeeBps: 25,
-      transferMaxAmount: '1200000000000000000',
-      withdrawMaxAmount: '1200000000000000000',
+      transferMaxAmount: '340282366920938463463374607431768211455',
+      withdrawMaxAmount: '340282366920938463463374607431768211455',
+    },
+    {
+      id: '691101997437781201062208285139214150313744022627571716486227682674885189667',
+      symbol: 'tUSDT',
+      decimals: 18,
+      wrappedErc20: '0xa7Ae7a38EB9929753Deb8B100627D2bfa060eC91',
+      viewerPk: ['16705602615272268567003522975712421097082383063417679753060534780702444376151', '14514464143093266825290311242522740387541372997639894559538766466467730361203'],
+      freezerPk: ['12575519572146277363559222067073217394207912146376135522069598095499837742570', '20535825957543427476664044300935290889134231934616628729189553228696621211842'],
+      depositFeeBps: 0,
+      withdrawFeeBps: 25,
+      transferMaxAmount: '340282366920938463463374607431768211455',
+      withdrawMaxAmount: '340282366920938463463374607431768211455',
     },
   ],
 };

src/types.ts

@@ -772,6 +772,10 @@ export interface MerkleApi {
 
 /** Wallet open session parameters. */
 export interface WalletSessionInput {
+  /**
+   * Secret seed for key derivation (min 16 characters).
+   * Any passphrase, hex string, or raw bytes — internally run through HKDF-SHA256.
+   */
   seed: string | Uint8Array;
   accountNonce?: number;
 }