diff --git a/package.json b/package.json
index b4e7229..1c7454c 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "stxer",
-  "version": "0.2.6",
+  "version": "0.3.0",
   "license": "MIT",
   "author": "Kyle Fang",
   "main": "dist/index.js",
@@ -18,7 +18,8 @@
     "size": "size-limit",
     "start": "dts watch",
     "test": "dts test",
-    "sample": "tsx src/sample/counter.ts"
+    "sample:counter": "tsx src/sample/counter.ts",
+    "sample:read": "tsx src/sample/read.ts"
   },
   "husky": {
     "hooks": {
diff --git a/src/batch-api.ts b/src/batch-api.ts
new file mode 100644
index 0000000..a40adc5
--- /dev/null
+++ b/src/batch-api.ts
@@ -0,0 +1,157 @@
+import {
+    type ClarityValue,
+    type ContractPrincipalCV,
+    deserializeCV,
+    type OptionalCV,
+    serializeCV,
+  } from '@stacks/transactions';
+  
+  export interface BatchReads {
+    variables?: {
+      contract: ContractPrincipalCV;
+      variableName: string;
+    }[];
+    maps?: {
+      contract: ContractPrincipalCV;
+      mapName: string;
+      mapKey: ClarityValue;
+    }[];
+    index_block_hash?: string;
+  }
+  
+  export interface BatchReadsResult {
+    variables: (ClarityValue | Error)[];
+    maps: (OptionalCV | Error)[];
+  }
+  
+  export interface BatchApiOptions {
+    stxerApi?: string;
+  }
+  
+  const DEFAULT_STXER_API = 'https://api.stxer.xyz';
+  
+  export async function batchRead(
+    reads: BatchReads,
+    options: BatchApiOptions = {}
+  ): Promise<BatchReadsResult> {
+    const payload: string[][] = [];
+    if (reads.variables != null) {
+      for (const variable of reads.variables) {
+        payload.push([serializeCV(variable.contract), variable.variableName]);
+      }
+    }
+    if (reads.maps != null) {
+      for (const map of reads.maps) {
+        payload.push([
+          serializeCV(map.contract),
+          map.mapName,
+          serializeCV(map.mapKey),
+        ]);
+      }
+    }
+  
+    const ibh =
+      reads.index_block_hash == null
+        ? null
+        : reads.index_block_hash.startsWith('0x')
+        ? reads.index_block_hash.substring(2)
+        : reads.index_block_hash;
+  
+    const url = `${options.stxerApi ?? DEFAULT_STXER_API}/sidecar/v2/batch-reads${
+      ibh == null ? '' : `?tip=${ibh}`
+    }`;
+    const data = await fetch(url, {
+      method: 'POST',
+      body: JSON.stringify(payload),
+    });
+    const text = await data.text();
+    if (!text.includes('Ok') && !text.includes('Err')) {
+      throw new Error(
+        `Requesting batch reads failed: ${text}, url: ${url}, payload: ${JSON.stringify(
+          payload
+        )}`
+      );
+    }
+    const results = JSON.parse(text) as [{ Ok: string } | { Err: string }];
+    const rs: BatchReadsResult = {
+      variables: [],
+      maps: [],
+    };
+    let variablesLength = 0;
+    if (reads.variables != null) {
+      variablesLength = reads.variables.length;
+      for (let i = 0; i < variablesLength; i++) {
+        const result = results[i];
+        if ('Ok' in result) {
+          rs.variables.push(deserializeCV(result.Ok));
+        } else {
+          rs.variables.push(new Error(result.Err));
+        }
+      }
+    }
+    if (reads.maps != null) {
+      for (let i = 0; i < reads.maps.length; i++) {
+        const result = results[i + variablesLength];
+        if ('Ok' in result) {
+          rs.maps.push(deserializeCV(result.Ok) as OptionalCV);
+        } else {
+          rs.maps.push(new Error(result.Err));
+        }
+      }
+    }
+    return rs;
+  }
+  
+  export interface BatchReadonlyRequest {
+    readonly: {
+      contract: ContractPrincipalCV;
+      functionName: string;
+      functionArgs: ClarityValue[];
+    }[];
+    index_block_hash?: string;
+  }
+  
+  export async function batchReadonly(
+    req: BatchReadonlyRequest,
+    options: BatchApiOptions = {}
+  ): Promise<(ClarityValue | Error)[]> {
+    const payload = req.readonly.map((r) => [
+      serializeCV(r.contract),
+      r.functionName,
+      ...r.functionArgs.map((arg) => serializeCV(arg)),
+    ]);
+  
+    const ibh =
+      req.index_block_hash == null
+        ? null
+        : req.index_block_hash.startsWith('0x')
+        ? req.index_block_hash.substring(2)
+        : req.index_block_hash;
+  
+    const url = `${options.stxerApi ?? DEFAULT_STXER_API}/sidecar/v2/batch-readonly${
+      ibh == null ? '' : `?tip=${ibh}`
+    }`;
+    const data = await fetch(url, {
+      method: 'POST',
+      body: JSON.stringify(payload),
+    });
+    const text = await data.text();
+    if (!text.includes('Ok') && !text.includes('Err')) {
+      throw new Error(
+        `Requesting batch readonly failed: ${text}, url: ${url}, payload: ${JSON.stringify(
+          payload
+        )}`
+      );
+    }
+    const results = JSON.parse(text) as [{ Ok: string } | { Err: string }];
+    const rs: (ClarityValue | Error)[] = [];
+    for (const result of results) {
+      if ('Ok' in result) {
+        rs.push(deserializeCV(result.Ok));
+      } else {
+        rs.push(new Error(result.Err));
+      }
+    }
+    return rs;
+  }
+  
\ No newline at end of file
diff --git a/src/index.ts b/src/index.ts
index 0c20ea8..aa692ee 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,388 +1,2 @@
-import { type AccountDataResponse, getNodeInfo, richFetch } from 'ts-clarity';
-import type { Block } from '@stacks/stacks-blockchain-api-types';
-import {
-  networkFrom,
-  STACKS_MAINNET,
-  STACKS_TESTNET,
-  type StacksNetworkName,
-} from '@stacks/network';
-import {
-  type ClarityValue,
-  ClarityVersion,
-  PostConditionMode,
-  type StacksTransactionWire,
-  bufferCV,
-  contractPrincipalCV,
-  makeUnsignedContractCall,
-  makeUnsignedContractDeploy,
-  makeUnsignedSTXTokenTransfer,
-  serializeCVBytes,
-  stringAsciiCV,
-  tupleCV,
-  uintCV,
-} from '@stacks/transactions';
-import { c32addressDecode } from 'c32check';
-
-function runTx(tx: StacksTransactionWire) {
-  // type 0: run transaction
-  return tupleCV({ type: uintCV(0), data: bufferCV(tx.serializeBytes()) });
-}
-
-export interface SimulationEval {
-  contract_id: string;
-  code: string;
-}
-
-export function runEval({ contract_id, code }: SimulationEval) {
-  const [contract_address, contract_name] = contract_id.split('.');
-  // type 1: eval arbitrary code inside a contract
-  return tupleCV({
-    type: uintCV(1),
-    data: bufferCV(
-      serializeCVBytes(
-        tupleCV({
-          contract: contractPrincipalCV(contract_address, contract_name),
-          code: stringAsciiCV(code),
-        })
-      )
-    ),
-  });
-}
-
-export async function runSimulation(
-  apiEndpoint: string,
-  block_hash: string,
-  block_height: number,
-  txs: (StacksTransactionWire | SimulationEval)[]
-) {
-  // Convert 'sim-v1' to Uint8Array
-  const header = new TextEncoder().encode('sim-v1');
-  // Create 8 bytes for block height
-  const heightBytes = new Uint8Array(8);
-  // Convert block height to bytes
-  const view = new DataView(heightBytes.buffer);
-  view.setBigUint64(0, BigInt(block_height), false); // false for big-endian
-
-  // Convert block hash to bytes
-  const hashHex = block_hash.startsWith('0x')
-    ? block_hash.substring(2)
-    : block_hash;
-  // Replace non-null assertion with null check
-  const matches = hashHex.match(/.{1,2}/g);
-  if (!matches) {
-    throw new Error('Invalid block hash format');
-  }
-  const hashBytes = new Uint8Array(
-    matches.map((byte) => Number.parseInt(byte, 16))
-  );
-
-  // Convert transactions to bytes
-  const txBytes = txs
-    .map((t) => ('contract_id' in t && 'code' in t ? runEval(t) : runTx(t)))
-    .map((t) => serializeCVBytes(t));
-
-  // Combine all byte arrays
-  const totalLength =
-    header.length +
-    heightBytes.length +
-    hashBytes.length +
-    txBytes.reduce((acc, curr) => acc + curr.length, 0);
-  const body = new Uint8Array(totalLength);
-
-  let offset = 0;
-  body.set(header, offset);
-  offset += header.length;
-  body.set(heightBytes, offset);
-  offset += heightBytes.length;
-  body.set(hashBytes, offset);
-  offset += hashBytes.length;
-  for (const tx of txBytes) {
-    body.set(tx, offset);
-    offset += tx.length;
-  }
-
-  const rs = await fetch(apiEndpoint, {
-    method: 'POST',
-    body,
-  }).then(async (rs) => {
-    const response = await rs.text();
-    if (!response.startsWith('{')) {
-      throw new Error(`failed to submit simulation: ${response}`);
-    }
-    return JSON.parse(response) as { id: string };
-  });
-  return rs.id;
-}
-
-interface SimulationBuilderOptions {
-  apiEndpoint?: string;
-  stacksNodeAPI?: string;
-  network?: StacksNetworkName | string;
-}
-
-export class SimulationBuilder {
-  private apiEndpoint: string;
-  private stacksNodeAPI: string;
-  private network: StacksNetworkName | string;
-
-  private constructor(options: SimulationBuilderOptions = {}) {
-    this.apiEndpoint = options.apiEndpoint ?? 'https://api.stxer.xyz';
-    this.stacksNodeAPI = options.stacksNodeAPI ?? 'https://api.hiro.so';
-    this.network = options.network ?? 'mainnet';
-  }
-
-  public static new(options?: SimulationBuilderOptions) {
-    return new SimulationBuilder(options);
-  }
-
-  // biome-ignore lint/style/useNumberNamespace: <explanation>
-  private block = NaN;
-  private sender = '';
-  private steps: (
-    | {
-        // contract call
-        contract_id: string;
-        function_name: string;
-        function_args?: ClarityValue[];
-        sender: string;
-        fee: number;
-      }
-    | {
-        // contract deploy
-        contract_name: string;
-        source_code: string;
-        deployer: string;
-        fee: number;
-        clarity_version: ClarityVersion;
-      }
-    | {
-        // STX transfer
-        recipient: string;
-        amount: number;
-        sender: string;
-        fee: number;
-      }
-    | SimulationEval
-  )[] = [];
-
-  public useBlockHeight(block: number) {
-    this.block = block;
-    return this;
-  }
-  public withSender(address: string) {
-    this.sender = address;
-    return this;
-  }
-  public addSTXTransfer(params: {
-    recipient: string;
-    amount: number;
-    sender?: string;
-    fee?: number;
-  }) {
-    if (params.sender == null && this.sender === '') {
-      throw new Error(
-        'Please specify a sender with useSender or adding a sender paramenter'
-      );
-    }
-    this.steps.push({
-      ...params,
-      sender: params.sender ?? this.sender,
-      fee: params.fee ?? 0,
-    });
-    return this;
-  }
-  public addContractCall(params: {
-    contract_id: string;
-    function_name: string;
-    function_args?: ClarityValue[];
-    sender?: string;
-    fee?: number;
-  }) {
-    if (params.sender == null && this.sender === '') {
-      throw new Error(
-        'Please specify a sender with useSender or adding a sender paramenter'
-      );
-    }
-    this.steps.push({
-      ...params,
-      sender: params.sender ?? this.sender,
-      fee: params.fee ?? 0,
-    });
-    return this;
-  }
-  public addContractDeploy(params: {
-    contract_name: string;
-    source_code: string;
-    deployer?: string;
-    fee?: number;
-    clarity_version?: ClarityVersion;
-  }) {
-    if (params.deployer == null && this.sender === '') {
-      throw new Error(
-        'Please specify a deployer with useSender or adding a deployer paramenter'
-      );
-    }
-    this.steps.push({
-      ...params,
-      deployer: params.deployer ?? this.sender,
-      fee: params.fee ?? 0,
-      clarity_version: params.clarity_version ?? ClarityVersion.Clarity3,
-    });
-    return this;
-  }
-  public addEvalCode(inside_contract_id: string, code: string) {
-    this.steps.push({
-      contract_id: inside_contract_id,
-      code,
-    });
-    return this;
-  }
-  public addMapRead(contract_id: string, map: string, key: string) {
-    this.steps.push({
-      contract_id,
-      code: `(map-get ${map} ${key})`,
-    });
-    return this;
-  }
-  public addVarRead(contract_id: string, variable: string) {
-    this.steps.push({
-      contract_id,
-      code: `(var-get ${variable})`,
-    });
-    return this;
-  }
-
-  private async getBlockInfo() {
-    if (Number.isNaN(this.block)) {
-      const { stacks_tip_height } = await getNodeInfo({
-        stacksEndpoint: this.stacksNodeAPI,
-      });
-      this.block = stacks_tip_height;
-    }
-    const info: Block = await richFetch(
-      `${this.stacksNodeAPI}/extended/v1/block/by_height/${this.block}?unanchored=true`
-    ).then((r) => r.json());
-    if (
-      info.height !== this.block ||
-      typeof info.hash !== 'string' ||
-      !info.hash.startsWith('0x')
-    ) {
-      throw new Error(
-        `failed to get block info for block height ${this.block}`
-      );
-    }
-    return {
-      block_height: this.block,
-      block_hash: info.hash.substring(2),
-      index_block_hash: info.index_block_hash.substring(2),
-    };
-  }
-
-  public async run() {
-    console.log(
-      `--------------------------------
-This product can never exist without your support!
-
-We receive sponsorship funds with:
-SP212Y5JKN59YP3GYG07K3S8W5SSGE4KH6B5STXER
-
-Feedbacks and feature requests are welcome.
-To get in touch: contact@stxer.xyz
---------------------------------`
-    );
-    const block = await this.getBlockInfo();
-    console.log(
-      `Using block height ${block.block_height} hash 0x${block.block_hash} to run simulation.`
-    );
-    const txs: (StacksTransactionWire | SimulationEval)[] = [];
-    const nonce_by_address = new Map<string, number>();
-    const nextNonce = async (sender: string) => {
-      const nonce = nonce_by_address.get(sender);
-      if (nonce == null) {
-        const url = `${
-          this.stacksNodeAPI
-        }/v2/accounts/${sender}?proof=${false}&tip=${block.index_block_hash}`;
-        const account: AccountDataResponse = await richFetch(url).then((r) =>
-          r.json()
-        );
-        nonce_by_address.set(sender, account.nonce + 1);
-        return account.nonce;
-      }
-      nonce_by_address.set(sender, nonce + 1);
-      return nonce;
-    };
-    for (const step of this.steps) {
-      let network = this.network === 'mainnet' ? STACKS_MAINNET : STACKS_TESTNET;
-      if (this.stacksNodeAPI) {
-        network = {
-          ...network,
-          client: {
-            ...network.client,
-            baseUrl: this.stacksNodeAPI,
-          },
-        };
-      }
-      if ('sender' in step && 'function_name' in step) {
-        const nonce = await nextNonce(step.sender);
-        const [contractAddress, contractName] = step.contract_id.split('.');
-        const tx = await makeUnsignedContractCall({
-          contractAddress,
-          contractName,
-          functionName: step.function_name,
-          functionArgs: step.function_args ?? [],
-          nonce,
-          network,
-          publicKey: '',
-          postConditionMode: PostConditionMode.Allow,
-          fee: step.fee,
-        });
-        tx.auth.spendingCondition.signer = c32addressDecode(step.sender)[1];
-        txs.push(tx);
-      } else if ('sender' in step && 'recipient' in step) {
-        const nonce = await nextNonce(step.sender);
-        const tx = await makeUnsignedSTXTokenTransfer({
-          recipient: step.recipient,
-          amount: step.amount,
-          nonce,
-          network,
-          publicKey: '',
-          fee: step.fee,
-        });
-        tx.auth.spendingCondition.signer = c32addressDecode(step.sender)[1];
-        txs.push(tx);
-      } else if ('deployer' in step) {
-        const nonce = await nextNonce(step.deployer);
-        const tx = await makeUnsignedContractDeploy({
-          contractName: step.contract_name,
-          codeBody: step.source_code,
-          nonce,
-          network,
-          publicKey: '',
-          postConditionMode: PostConditionMode.Allow,
-          fee: step.fee,
-        });
-        tx.auth.spendingCondition.signer = c32addressDecode(step.deployer)[1];
-        txs.push(tx);
-      } else if ('code' in step) {
-        txs.push(step);
-      } else {
-        // biome-ignore lint/style/noUnusedTemplateLiteral: <explanation>
-        console.log(`Invalid simulation step:`, step);
-      }
-    }
-    const id = await runSimulation(
-      `${this.apiEndpoint}/simulations`,
-      block.block_hash,
-      block.block_height,
-      txs
-    );
-    console.log(
-      `Simulation will be available at: https://stxer.xyz/simulations/${this.network}/${id}`
-    );
-    return id;
-  }
-
-  public pipe(transform: (builder: SimulationBuilder) => SimulationBuilder): SimulationBuilder {
-    return transform(this);
-  }
-}
+export * from './batch-api';
+export * from './simulation';
diff --git a/src/sample/read.ts b/src/sample/read.ts
new file mode 100644
index 0000000..8709f6e
--- /dev/null
+++ b/src/sample/read.ts
@@ -0,0 +1,125 @@
+import {
+    contractPrincipalCV,
+    principalCV,
+    stringAsciiCV,
+    tupleCV,
+    uintCV,
+  } from '@stacks/transactions';
+  import { batchRead, batchReadonly } from '../batch-api';
+  
+  async function batchReadsExample() {
+    const rs = await batchRead({
+      // index_block_hash:
+      //   'ce04817b9c6d90814ff9c06228d3a07d64335b1d9b01a233456fc304e34f7c0e', // block 373499
+      variables: [
+        {
+          contract: contractPrincipalCV(
+            'SP1Z92MPDQEWZXW36VX71Q25HKF5K2EPCJ304F275',
+            'liquidity-token-v5kbe3oqvac'
+          ),
+          variableName: 'balance-x',
+        },
+        {
+          contract: contractPrincipalCV(
+            'SP1Z92MPDQEWZXW36VX71Q25HKF5K2EPCJ304F275',
+            'liquidity-token-v5kbe3oqvac'
+          ),
+          variableName: 'balance-y',
+        },
+        {
+          contract: contractPrincipalCV(
+            'SP1Z92MPDQEWZXW36VX71Q25HKF5K2EPCJ304F275',
+            'liquidity-token-v5kbe3oqvac'
+          ),
+          variableName: 'something-not-exists',
+        },
+      ],
+      maps: [
+        {
+          contract: contractPrincipalCV(
+            'SP102V8P0F7JX67ARQ77WEA3D3CFB5XW39REDT0AM',
+            'amm-registry-v2-01'
+          ),
+          mapName: 'pools-data-map',
+          mapKey: tupleCV({
+            'token-x': principalCV(
+              'SP102V8P0F7JX67ARQ77WEA3D3CFB5XW39REDT0AM.token-wstx-v2'
+            ),
+            'token-y': principalCV(
+              'SP102V8P0F7JX67ARQ77WEA3D3CFB5XW39REDT0AM.token-alex'
+            ),
+            factor: uintCV(1e8),
+          }),
+        },
+        {
+          contract: contractPrincipalCV(
+            'SP1Y5YSTAHZ88XYK1VPDH24GY0HPX5J4JECTMY4A1',
+            'univ2-core'
+          ),
+          mapName: 'pools',
+          mapKey: uintCV(1),
+        },
+        {
+          contract: contractPrincipalCV(
+            'SP1Y5YSTAHZ88XYK1VPDH24GY0HPX5J4JECTMY4A1',
+            'contract-not-exists'
+          ),
+          mapName: 'pools',
+          mapKey: uintCV(1),
+        },
+      ],
+    });
+    console.log(rs);
+  }
+  
+  async function batchReadonlyExample() {
+    const rs = await batchReadonly({
+      index_block_hash:
+        'ce04817b9c6d90814ff9c06228d3a07d64335b1d9b01a233456fc304e34f7c0e',
+      readonly: [
+        {
+          contract: contractPrincipalCV(
+            'SM3VDXK3WZZSA84XXFKAFAF15NNZX32CTSG82JFQ4',
+            'sbtc-token'
+          ),
+          functionName: 'get-total-supply',
+          functionArgs: [],
+        },
+        {
+          contract: contractPrincipalCV(
+            'SM3VDXK3WZZSA84XXFKAFAF15NNZX32CTSG82JFQ4',
+            'sbtc-token'
+          ),
+          functionName: 'get-balance',
+          functionArgs: [
+            principalCV('SP1CT7J2RWBZD62QAX36A2PQ3HKH5NFDGVHB8J34V'),
+          ],
+        },
+        {
+          contract: contractPrincipalCV(
+            'SM3VDXK3WZZSA84XXFKAFAF15NNZX32CTSG82JFQ4',
+            'sbtc-token'
+          ),
+          functionName: 'function-not-exists',
+          functionArgs: [],
+        },
+        {
+          contract: contractPrincipalCV(
+            'SM3VDXK3WZZSA84XXFKAFAF15NNZX32CTSG82JFQ4',
+            'sbtc-token'
+          ),
+          functionName: 'get-balance',
+          functionArgs: [stringAsciiCV('invalid-args')],
+        },
+      ],
+    });
+    console.log(rs);
+  }
+  
+  async function main() {
+    await batchReadsExample();
+    await batchReadonlyExample();
+  }
+  
+  main().catch(console.error);
+  
\ No newline at end of file
diff --git a/src/simulation.ts b/src/simulation.ts
new file mode 100644
index 0000000..bab1e74
--- /dev/null
+++ b/src/simulation.ts
@@ -0,0 +1,387 @@
+import { type AccountDataResponse, getNodeInfo, richFetch } from 'ts-clarity';
+import type { Block } from '@stacks/stacks-blockchain-api-types';
+import {
+  STACKS_MAINNET,
+  STACKS_TESTNET,
+  type StacksNetworkName,
+} from '@stacks/network';
+import {
+  type ClarityValue,
+  ClarityVersion,
+  PostConditionMode,
+  type StacksTransactionWire,
+  bufferCV,
+  contractPrincipalCV,
+  makeUnsignedContractCall,
+  makeUnsignedContractDeploy,
+  makeUnsignedSTXTokenTransfer,
+  serializeCVBytes,
+  stringAsciiCV,
+  tupleCV,
+  uintCV,
+} from '@stacks/transactions';
+import { c32addressDecode } from 'c32check';
+
+function runTx(tx: StacksTransactionWire) {
+  // type 0: run transaction
+  return tupleCV({ type: uintCV(0), data: bufferCV(tx.serializeBytes()) });
+}
+
+export interface SimulationEval {
+  contract_id: string;
+  code: string;
+}
+
+export function runEval({ contract_id, code }: SimulationEval) {
+  const [contract_address, contract_name] = contract_id.split('.');
+  // type 1: eval arbitrary code inside a contract
+  return tupleCV({
+    type: uintCV(1),
+    data: bufferCV(
+      serializeCVBytes(
+        tupleCV({
+          contract: contractPrincipalCV(contract_address, contract_name),
+          code: stringAsciiCV(code),
+        })
+      )
+    ),
+  });
+}
+
+export async function runSimulation(
+  apiEndpoint: string,
+  block_hash: string,
+  block_height: number,
+  txs: (StacksTransactionWire | SimulationEval)[]
+) {
+  // Convert 'sim-v1' to Uint8Array
+  const header = new TextEncoder().encode('sim-v1');
+  // Create 8 bytes for block height
+  const heightBytes = new Uint8Array(8);
+  // Convert block height to bytes
+  const view = new DataView(heightBytes.buffer);
+  view.setBigUint64(0, BigInt(block_height), false); // false for big-endian
+
+  // Convert block hash to bytes
+  const hashHex = block_hash.startsWith('0x')
+    ? block_hash.substring(2)
+    : block_hash;
+  // Replace non-null assertion with null check
+  const matches = hashHex.match(/.{1,2}/g);
+  if (!matches) {
+    throw new Error('Invalid block hash format');
+  }
+  const hashBytes = new Uint8Array(
+    matches.map((byte) => Number.parseInt(byte, 16))
+  );
+
+  // Convert transactions to bytes
+  const txBytes = txs
+    .map((t) => ('contract_id' in t && 'code' in t ? runEval(t) : runTx(t)))
+    .map((t) => serializeCVBytes(t));
+
+  // Combine all byte arrays
+  const totalLength =
+    header.length +
+    heightBytes.length +
+    hashBytes.length +
+    txBytes.reduce((acc, curr) => acc + curr.length, 0);
+  const body = new Uint8Array(totalLength);
+
+  let offset = 0;
+  body.set(header, offset);
+  offset += header.length;
+  body.set(heightBytes, offset);
+  offset += heightBytes.length;
+  body.set(hashBytes, offset);
+  offset += hashBytes.length;
+  for (const tx of txBytes) {
+    body.set(tx, offset);
+    offset += tx.length;
+  }
+
+  const rs = await fetch(apiEndpoint, {
+    method: 'POST',
+    body,
+  }).then(async (rs) => {
+    const response = await rs.text();
+    if (!response.startsWith('{')) {
+      throw new Error(`failed to submit simulation: ${response}`);
+    }
+    return JSON.parse(response) as { id: string };
+  });
+  return rs.id;
+}
+
+interface SimulationBuilderOptions {
+  apiEndpoint?: string;
+  stacksNodeAPI?: string;
+  network?: StacksNetworkName | string;
+}
+
+export class SimulationBuilder {
+  private apiEndpoint: string;
+  private stacksNodeAPI: string;
+  private network: StacksNetworkName | string;
+
+  private constructor(options: SimulationBuilderOptions = {}) {
+    this.apiEndpoint = options.apiEndpoint ?? 'https://api.stxer.xyz';
+    this.stacksNodeAPI = options.stacksNodeAPI ?? 'https://api.hiro.so';
+    this.network = options.network ?? 'mainnet';
+  }
+
+  public static new(options?: SimulationBuilderOptions) {
+    return new SimulationBuilder(options);
+  }
+
+  // biome-ignore lint/style/useNumberNamespace: <explanation>
+  private block = NaN;
+  private sender = '';
+  private steps: (
+    | {
+        // contract call
+        contract_id: string;
+        function_name: string;
+        function_args?: ClarityValue[];
+        sender: string;
+        fee: number;
+      }
+    | {
+        // contract deploy
+        contract_name: string;
+        source_code: string;
+        deployer: string;
+        fee: number;
+        clarity_version: ClarityVersion;
+      }
+    | {
+        // STX transfer
+        recipient: string;
+        amount: number;
+        sender: string;
+        fee: number;
+      }
+    | SimulationEval
+  )[] = [];
+
+  public useBlockHeight(block: number) {
+    this.block = block;
+    return this;
+  }
+  public withSender(address: string) {
+    this.sender = address;
+    return this;
+  }
+  public addSTXTransfer(params: {
+    recipient: string;
+    amount: number;
+    sender?: string;
+    fee?: number;
+  }) {
+    if (params.sender == null && this.sender === '') {
+      throw new Error(
+        'Please specify a sender with useSender or adding a sender paramenter'
+      );
+    }
+    this.steps.push({
+      ...params,
+      sender: params.sender ?? this.sender,
+      fee: params.fee ?? 0,
+    });
+    return this;
+  }
+  public addContractCall(params: {
+    contract_id: string;
+    function_name: string;
+    function_args?: ClarityValue[];
+    sender?: string;
+    fee?: number;
+  }) {
+    if (params.sender == null && this.sender === '') {
+      throw new Error(
+        'Please specify a sender with useSender or adding a sender paramenter'
+      );
+    }
+    this.steps.push({
+      ...params,
+      sender: params.sender ?? this.sender,
+      fee: params.fee ?? 0,
+    });
+    return this;
+  }
+  public addContractDeploy(params: {
+    contract_name: string;
+    source_code: string;
+    deployer?: string;
+    fee?: number;
+    clarity_version?: ClarityVersion;
+  }) {
+    if (params.deployer == null && this.sender === '') {
+      throw new Error(
+        'Please specify a deployer with useSender or adding a deployer paramenter'
+      );
+    }
+    this.steps.push({
+      ...params,
+      deployer: params.deployer ?? this.sender,
+      fee: params.fee ?? 0,
+      clarity_version: params.clarity_version ?? ClarityVersion.Clarity3,
+    });
+    return this;
+  }
+  public addEvalCode(inside_contract_id: string, code: string) {
+    this.steps.push({
+      contract_id: inside_contract_id,
+      code,
+    });
+    return this;
+  }
+  public addMapRead(contract_id: string, map: string, key: string) {
+    this.steps.push({
+      contract_id,
+      code: `(map-get ${map} ${key})`,
+    });
+    return this;
+  }
+  public addVarRead(contract_id: string, variable: string) {
+    this.steps.push({
+      contract_id,
+      code: `(var-get ${variable})`,
+    });
+    return this;
+  }
+
+  private async getBlockInfo() {
+    if (Number.isNaN(this.block)) {
+      const { stacks_tip_height } = await getNodeInfo({
+        stacksEndpoint: this.stacksNodeAPI,
+      });
+      this.block = stacks_tip_height;
+    }
+    const info: Block = await richFetch(
+      `${this.stacksNodeAPI}/extended/v1/block/by_height/${this.block}?unanchored=true`
+    ).then((r) => r.json());
+    if (
+      info.height !== this.block ||
+      typeof info.hash !== 'string' ||
+      !info.hash.startsWith('0x')
+    ) {
+      throw new Error(
+        `failed to get block info for block height ${this.block}`
+      );
+    }
+    return {
+      block_height: this.block,
+      block_hash: info.hash.substring(2),
+      index_block_hash: info.index_block_hash.substring(2),
+    };
+  }
+
+  public async run() {
+    console.log(
+      `--------------------------------
+This product can never exist without your support!
+
+We receive sponsorship funds with:
+SP212Y5JKN59YP3GYG07K3S8W5SSGE4KH6B5STXER
+
+Feedbacks and feature requests are welcome.
+To get in touch: contact@stxer.xyz
+--------------------------------`
+    );
+    const block = await this.getBlockInfo();
+    console.log(
+      `Using block height ${block.block_height} hash 0x${block.block_hash} to run simulation.`
+    );
+    const txs: (StacksTransactionWire | SimulationEval)[] = [];
+    const nonce_by_address = new Map<string, number>();
+    const nextNonce = async (sender: string) => {
+      const nonce = nonce_by_address.get(sender);
+      if (nonce == null) {
+        const url = `${
+          this.stacksNodeAPI
+        }/v2/accounts/${sender}?proof=${false}&tip=${block.index_block_hash}`;
+        const account: AccountDataResponse = await richFetch(url).then((r) =>
+          r.json()
+        );
+        nonce_by_address.set(sender, account.nonce + 1);
+        return account.nonce;
+      }
+      nonce_by_address.set(sender, nonce + 1);
+      return nonce;
+    };
+    for (const step of this.steps) {
+      let network = this.network === 'mainnet' ? STACKS_MAINNET : STACKS_TESTNET;
+      if (this.stacksNodeAPI) {
+        network = {
+          ...network,
+          client: {
+            ...network.client,
+            baseUrl: this.stacksNodeAPI,
+          },
+        };
+      }
+      if ('sender' in step && 'function_name' in step) {
+        const nonce = await nextNonce(step.sender);
+        const [contractAddress, contractName] = step.contract_id.split('.');
+        const tx = await makeUnsignedContractCall({
+          contractAddress,
+          contractName,
+          functionName: step.function_name,
+          functionArgs: step.function_args ?? [],
+          nonce,
+          network,
+          publicKey: '',
+          postConditionMode: PostConditionMode.Allow,
+          fee: step.fee,
+        });
+        tx.auth.spendingCondition.signer = c32addressDecode(step.sender)[1];
+        txs.push(tx);
+      } else if ('sender' in step && 'recipient' in step) {
+        const nonce = await nextNonce(step.sender);
+        const tx = await makeUnsignedSTXTokenTransfer({
+          recipient: step.recipient,
+          amount: step.amount,
+          nonce,
+          network,
+          publicKey: '',
+          fee: step.fee,
+        });
+        tx.auth.spendingCondition.signer = c32addressDecode(step.sender)[1];
+        txs.push(tx);
+      } else if ('deployer' in step) {
+        const nonce = await nextNonce(step.deployer);
+        const tx = await makeUnsignedContractDeploy({
+          contractName: step.contract_name,
+          codeBody: step.source_code,
+          nonce,
+          network,
+          publicKey: '',
+          postConditionMode: PostConditionMode.Allow,
+          fee: step.fee,
+        });
+        tx.auth.spendingCondition.signer = c32addressDecode(step.deployer)[1];
+        txs.push(tx);
+      } else if ('code' in step) {
+        txs.push(step);
+      } else {
+        // biome-ignore lint/style/noUnusedTemplateLiteral: <explanation>
+        console.log(`Invalid simulation step:`, step);
+      }
+    }
+    const id = await runSimulation(
+      `${this.apiEndpoint}/simulations`,
+      block.block_hash,
+      block.block_height,
+      txs
+    );
+    console.log(
+      `Simulation will be available at: https://stxer.xyz/simulations/${this.network}/${id}`
+    );
+    return id;
+  }
+
+  public pipe(transform: (builder: SimulationBuilder) => SimulationBuilder): SimulationBuilder {
+    return transform(this);
+  }
+}