diff --git a/contracts/script/test/7683/concurrentintents/.gitignore b/contracts/script/test/7683/concurrentintents/.gitignore
new file mode 100644
index 00000000..a14702c4
--- /dev/null
+++ b/contracts/script/test/7683/concurrentintents/.gitignore
@@ -0,0 +1,34 @@
+# dependencies (bun install)
+node_modules
+
+# output
+out
+dist
+*.tgz
+
+# code coverage
+coverage
+*.lcov
+
+# logs
+logs
+_.log
+report.[0-9]_.[0-9]_.[0-9]_.[0-9]_.json
+
+# dotenv environment variable files
+.env
+.env.development.local
+.env.test.local
+.env.production.local
+.env.local
+
+# caches
+.eslintcache
+.cache
+*.tsbuildinfo
+
+# IntelliJ based IDEs
+.idea
+
+# Finder (MacOS) folder config
+.DS_Store
diff --git a/contracts/script/test/7683/concurrentintents/README.md b/contracts/script/test/7683/concurrentintents/README.md
new file mode 100644
index 00000000..7db7cc50
--- /dev/null
+++ b/contracts/script/test/7683/concurrentintents/README.md
@@ -0,0 +1,13 @@
+# concurrentintents
+
+To install dependencies:
+
+```bash
+bun install
+```
+
+To run:
+
+```bash
+bun run index.ts
+```
diff --git a/contracts/script/test/7683/concurrentintents/bun.lock b/contracts/script/test/7683/concurrentintents/bun.lock
new file mode 100644
index 00000000..93701fe7
--- /dev/null
+++ b/contracts/script/test/7683/concurrentintents/bun.lock
@@ -0,0 +1,55 @@
+{
+  "lockfileVersion": 1,
+  "configVersion": 1,
+  "workspaces": {
+    "": {
+      "name": "concurrentintents",
+      "dependencies": {
+        "viem": "^2.44.2",
+      },
+      "devDependencies": {
+        "@types/bun": "latest",
+      },
+      "peerDependencies": {
+        "typescript": "^5",
+      },
+    },
+  },
+  "packages": {
+    "@adraffy/ens-normalize": ["@adraffy/ens-normalize@1.11.1", "", {}, "sha512-nhCBV3quEgesuf7c7KYfperqSS14T8bYuvJ8PcLJp6znkZpFc0AuW4qBtr8eKVyPPe/8RSr7sglCWPU5eaxwKQ=="],
+
+    "@noble/ciphers": ["@noble/ciphers@1.3.0", "", {}, "sha512-2I0gnIVPtfnMw9ee9h1dJG7tp81+8Ob3OJb3Mv37rx5L40/b0i7djjCVvGOVqc9AEIQyvyu1i6ypKdFw8R8gQw=="],
+
+    "@noble/curves": ["@noble/curves@1.9.1", "", { "dependencies": { "@noble/hashes": "1.8.0" } }, "sha512-k11yZxZg+t+gWvBbIswW0yoJlu8cHOC7dhunwOzoWH/mXGBiYyR4YY6hAEK/3EUs4UpB8la1RfdRpeGsFHkWsA=="],
+
+    "@noble/hashes": ["@noble/hashes@1.8.0", "", {}, "sha512-jCs9ldd7NwzpgXDIf6P3+NrHh9/sD6CQdxHyjQI+h/6rDNo88ypBxxz45UDuZHz9r3tNz7N/VInSVoVdtXEI4A=="],
+
+    "@scure/base": ["@scure/base@1.2.6", "", {}, "sha512-g/nm5FgUa//MCj1gV09zTJTaM6KBAHqLN907YVQqf7zC49+DcO4B1so4ZX07Ef10Twr6nuqYEH9GEggFXA4Fmg=="],
+
+    "@scure/bip32": ["@scure/bip32@1.7.0", "", { "dependencies": { "@noble/curves": "~1.9.0", "@noble/hashes": "~1.8.0", "@scure/base": "~1.2.5" } }, "sha512-E4FFX/N3f4B80AKWp5dP6ow+flD1LQZo/w8UnLGYZO674jS6YnYeepycOOksv+vLPSpgN35wgKgy+ybfTb2SMw=="],
+
+    "@scure/bip39": ["@scure/bip39@1.6.0", "", { "dependencies": { "@noble/hashes": "~1.8.0", "@scure/base": "~1.2.5" } }, "sha512-+lF0BbLiJNwVlev4eKelw1WWLaiKXw7sSl8T6FvBlWkdX+94aGJ4o8XjUdlyhTCjd8c+B3KT3JfS8P0bLRNU6A=="],
+
+    "@types/bun": ["@types/bun@1.3.5", "", { "dependencies": { "bun-types": "1.3.5" } }, "sha512-RnygCqNrd3srIPEWBd5LFeUYG7plCoH2Yw9WaZGyNmdTEei+gWaHqydbaIRkIkcbXwhBT94q78QljxN0Sk838w=="],
+
+    "@types/node": ["@types/node@25.0.8", "", { "dependencies": { "undici-types": "~7.16.0" } }, "sha512-powIePYMmC3ibL0UJ2i2s0WIbq6cg6UyVFQxSCpaPxxzAaziRfimGivjdF943sSGV6RADVbk0Nvlm5P/FB44Zg=="],
+
+    "abitype": ["abitype@1.2.3", "", { "peerDependencies": { "typescript": ">=5.0.4", "zod": "^3.22.0 || ^4.0.0" }, "optionalPeers": ["typescript", "zod"] }, "sha512-Ofer5QUnuUdTFsBRwARMoWKOH1ND5ehwYhJ3OJ/BQO+StkwQjHw0XyVh4vDttzHB7QOFhPHa/o413PJ82gU/Tg=="],
+
+    "bun-types": ["bun-types@1.3.5", "", { "dependencies": { "@types/node": "*" } }, "sha512-inmAYe2PFLs0SUbFOWSVD24sg1jFlMPxOjOSSCYqUgn4Hsc3rDc7dFvfVYjFPNHtov6kgUeulV4SxbuIV/stPw=="],
+
+    "eventemitter3": ["eventemitter3@5.0.1", "", {}, "sha512-GWkBvjiSZK87ELrYOSESUYeVIc9mvLLf/nXalMOS5dYrgZq9o5OVkbZAVM06CVxYsCwH9BDZFPlQTlPA1j4ahA=="],
+
+    "isows": ["isows@1.0.7", "", { "peerDependencies": { "ws": "*" } }, "sha512-I1fSfDCZL5P0v33sVqeTDSpcstAg/N+wF5HS033mogOVIp4B+oHC7oOCsA3axAbBSGTJ8QubbNmnIRN/h8U7hg=="],
+
+    "ox": ["ox@0.11.3", "", { "dependencies": { "@adraffy/ens-normalize": "^1.11.0", "@noble/ciphers": "^1.3.0", "@noble/curves": "1.9.1", "@noble/hashes": "^1.8.0", "@scure/bip32": "^1.7.0", "@scure/bip39": "^1.6.0", "abitype": "^1.2.3", "eventemitter3": "5.0.1" }, "peerDependencies": { "typescript": ">=5.4.0" }, "optionalPeers": ["typescript"] }, "sha512-1bWYGk/xZel3xro3l8WGg6eq4YEKlaqvyMtVhfMFpbJzK2F6rj4EDRtqDCWVEJMkzcmEi9uW2QxsqELokOlarw=="],
+
+    "typescript": ["typescript@5.9.3", "", { "bin": { "tsc": "bin/tsc", "tsserver": "bin/tsserver" } }, "sha512-jl1vZzPDinLr9eUt3J/t7V6FgNEw9QjvBPdysz9KfQDD41fQrC2Y4vKQdiaUpFT4bXlb1RHhLpp8wtm6M5TgSw=="],
+
+    "undici-types": ["undici-types@7.16.0", "", {}, "sha512-Zz+aZWSj8LE6zoxD+xrjh4VfkIG8Ya6LvYkZqtUQGJPZjYl53ypCaUwWqo7eI0x66KBGeRo+mlBEkMSeSZ38Nw=="],
+
+    "viem": ["viem@2.44.2", "", { "dependencies": { "@noble/curves": "1.9.1", "@noble/hashes": "1.8.0", "@scure/bip32": "1.7.0", "@scure/bip39": "1.6.0", "abitype": "1.2.3", "isows": "1.0.7", "ox": "0.11.3", "ws": "8.18.3" }, "peerDependencies": { "typescript": ">=5.0.4" }, "optionalPeers": ["typescript"] }, "sha512-nHY872t/T3flLpVsnvQT/89bwbrJwxaL917FDv7Oxy4E5FWIFkokRQOKXG3P+hgl30QYVZxi9o2SUHLnebycxw=="],
+
+    "ws": ["ws@8.18.3", "", { "peerDependencies": { "bufferutil": "^4.0.1", "utf-8-validate": ">=5.0.2" }, "optionalPeers": ["bufferutil", "utf-8-validate"] }, "sha512-PEIGCY5tSlUt50cqyMXfCzX+oOPqN0vuGqWzbcJ2xvnkzkq46oOpz7dQaTDBdfICb4N14+GARUDw2XV2N4tvzg=="],
+  }
+}
diff --git a/contracts/script/test/7683/concurrentintents/index.ts b/contracts/script/test/7683/concurrentintents/index.ts
new file mode 100644
index 00000000..a295ec49
--- /dev/null
+++ b/contracts/script/test/7683/concurrentintents/index.ts
@@ -0,0 +1,342 @@
+import "dotenv/config";
+import crypto from "node:crypto";
+import {
+  createPublicClient,
+  createWalletClient,
+  webSocket,
+  parseGwei,
+  encodeAbiParameters,
+  encodeFunctionData,
+  padHex,
+  type Abi,
+  type Hex,
+  type Address, type Chain,
+} from "viem";
+import { privateKeyToAccount } from "viem/accounts";
+import { arbitrum, base } from "viem/chains";
+
+function requireEnv(name: string): string {
+  const v = process.env[name];
+  if (!v) throw new Error(`Missing env var: ${name}`);
+  return v;
+}
+
+function asHexPrivateKey(v: string): Hex {
+  return (v.startsWith("0x") ? v : `0x${v}`) as Hex;
+}
+
+function asAddress(v: string): Address {
+  if (!v.startsWith("0x") || v.length !== 42) throw new Error(`Invalid address: ${v}`);
+  return v as Address;
+}
+
+function addressToBytes32(a: Address): Hex {
+  return padHex(a, { size: 32 });
+}
+
+const TX_COUNT = Number(process.env.TX_COUNT ?? "100");
+const TX_CONCURRENCY = Number(process.env.TX_CONCURRENCY ?? "25");
+const PRIORITY_FEE_GWEI = process.env.PRIORITY_FEE_GWEI ?? "0.05";
+
+const AMOUNT_IN = BigInt(process.env.AMOUNT_IN ?? "100");
+const MIN_OUT_BPS = BigInt(process.env.MIN_OUT_BPS ?? "9000"); // 9000 = 90%
+const FILL_DEADLINE_SECONDS = BigInt(process.env.FILL_DEADLINE_SECONDS ?? "300");
+
+const ERC20_ABI = [
+  {
+    type: "function",
+    name: "approve",
+    stateMutability: "nonpayable",
+    inputs: [
+      { name: "spender", type: "address" },
+      { name: "amount", type: "uint256" },
+    ],
+    outputs: [{ name: "", type: "bool" }],
+  },
+] as const satisfies Abi;
+
+// Minimal ABI for T1ERC7683.open(OnchainCrossChainOrder)
+const T1ERC7683_ABI = [
+  {
+    type: "function",
+    name: "open",
+    stateMutability: "payable",
+    inputs: [
+      {
+        name: "_order",
+        type: "tuple",
+        components: [
+          { name: "fillDeadline", type: "uint32" },
+          { name: "orderDataType", type: "bytes32" },
+          { name: "orderData", type: "bytes" },
+        ],
+      },
+    ],
+    outputs: [],
+  },
+] as const satisfies Abi;
+
+// bytes32 orderDataType = keccak256("OrderData(...same as OrderEncoder...)")
+// We hardcode the value by computing it at runtime from the exact type string.
+import { keccak256, toHex } from "viem";
+const ORDER_DATA_TYPE_STRING =
+  "OrderData(" +
+  "bytes32 sender," +
+  "bytes32 recipient," +
+  "bytes32 inputToken," +
+  "bytes32 outputToken," +
+  "uint256 amountIn," +
+  "uint256 minAmountOut," +
+  "uint256 senderNonce," +
+  "uint32 originDomain," +
+  "uint32 destinationDomain," +
+  "bytes32 destinationSettler," +
+  "uint32 fillDeadline," +
+  "bool closedAuction," +
+  "bytes data)";
+
+const ORDER_DATA_TYPEHASH = keccak256(toHex(ORDER_DATA_TYPE_STRING)) as Hex;
+
+type ChainCfg = {
+  name: string;
+  chain: Chain;
+  wsUrl: string;
+  privateKey: Hex;
+
+  t1Erc7683: Address;
+
+  // origin-side token address
+  inputToken: Address;
+
+  // destination-side token address (encoded into orderData)
+  outputToken: Address;
+
+  destinationSettler: Address;
+
+  originDomain: number; // uint32
+  destinationDomain: number; // uint32
+};
+
+function randomUint256(): bigint {
+  return BigInt(`0x${crypto.randomBytes(32).toString("hex")}`);
+}
+
+async function approveIfNeeded(cfg: ChainCfg, walletClient: any, publicClient: any) {
+  // For speed/simplicity, we just send approve(max). Many tokens allow repeated approve(max).
+  const maxUint256 = (1n << 256n) - 1n;
+
+  const data = encodeFunctionData({
+    abi: ERC20_ABI,
+    functionName: "approve",
+    args: [cfg.t1Erc7683, maxUint256],
+  });
+
+  const suggested = await publicClient.estimateFeesPerGas();
+  const maxPriorityFeePerGas = parseGwei(PRIORITY_FEE_GWEI);
+  const maxFeePerGas =
+    suggested.maxFeePerGas && suggested.maxFeePerGas > maxPriorityFeePerGas
+      ? suggested.maxFeePerGas
+      : maxPriorityFeePerGas;
+
+  const request = await publicClient.prepareTransactionRequest({
+    account: privateKeyToAccount(cfg.privateKey),
+    to: cfg.inputToken,
+    data,
+    value: 0n,
+    maxFeePerGas,
+    maxPriorityFeePerGas,
+  });
+
+  const signed = await walletClient.signTransaction(request);
+  const hash = await publicClient.sendRawTransaction({ serializedTransaction: signed });
+
+  console.log(`[${cfg.name}] approve tx: ${hash}`);
+  await publicClient.waitForTransactionReceipt({ hash });
+}
+
+async function runChain(cfg: ChainCfg) {
+  const account = privateKeyToAccount(cfg.privateKey);
+  const owner = account.address;
+
+  const transport = webSocket(cfg.wsUrl, {
+    reconnect: { attempts: Infinity, delay: 500 },
+    keepAlive: { interval: 15_000 },
+  });
+
+  const publicClient = createPublicClient({ chain: cfg.chain, transport });
+  const walletClient = createWalletClient({ chain: cfg.chain, transport, account });
+
+  const [baseNonce, now] = await Promise.all([
+    publicClient.getTransactionCount({ address: owner, blockTag: "pending" }),
+    publicClient.getBlock(), // includes timestamp
+  ]);
+
+  const suggested = await publicClient.estimateFeesPerGas();
+  const maxPriorityFeePerGas = parseGwei(PRIORITY_FEE_GWEI);
+  const maxFeePerGas =
+    suggested.maxFeePerGas && suggested.maxFeePerGas > maxPriorityFeePerGas
+      ? suggested.maxFeePerGas
+      : maxPriorityFeePerGas;
+
+  console.log(
+    `[${cfg.name}] from=${owner} startNonce=${baseNonce} maxFeePerGas=${maxFeePerGas} maxPriorityFeePerGas=${maxPriorityFeePerGas}`,
+  );
+
+  // One approval before the burst (consumes 1 nonce).
+  await approveIfNeeded(cfg, walletClient, publicClient);
+
+  // Re-fetch nonce after approve, to be safe.
+  const startNonce = await publicClient.getTransactionCount({ address: owner, blockTag: "pending" });
+
+  const minAmountOut = (AMOUNT_IN * MIN_OUT_BPS) / 10_000n;
+  const baseTimestamp = BigInt(now.timestamp);
+
+  // Pre-sign all open() txs for speed.
+  const signedTxs: Hex[] = [];
+  for (let i = 0; i < TX_COUNT; i++) {
+    const senderNonce = randomUint256();
+    const fillDeadline = Number(baseTimestamp + FILL_DEADLINE_SECONDS); // fits uint32 for normal timestamps
+
+    // OrderData (solidity) as ABI tuple encoding (equivalent to abi.encode(orderData))
+    const encodedOrderData = encodeAbiParameters(
+      [
+        {
+          type: "tuple",
+          name: "orderData",
+          components: [
+            { name: "sender", type: "bytes32" },
+            { name: "recipient", type: "bytes32" },
+            { name: "inputToken", type: "bytes32" },
+            { name: "outputToken", type: "bytes32" },
+            { name: "amountIn", type: "uint256" },
+            { name: "minAmountOut", type: "uint256" },
+            { name: "senderNonce", type: "uint256" },
+            { name: "originDomain", type: "uint32" },
+            { name: "destinationDomain", type: "uint32" },
+            { name: "destinationSettler", type: "bytes32" },
+            { name: "fillDeadline", type: "uint32" },
+            { name: "closedAuction", type: "bool" },
+            { name: "data", type: "bytes" },
+          ],
+        },
+      ],
+      [
+        {
+          sender: addressToBytes32(owner),
+          recipient: addressToBytes32(owner),
+          inputToken: addressToBytes32(cfg.inputToken),
+          outputToken: addressToBytes32(cfg.outputToken),
+          amountIn: AMOUNT_IN,
+          minAmountOut,
+          senderNonce,
+          originDomain: cfg.originDomain,
+          destinationDomain: cfg.destinationDomain,
+          destinationSettler: addressToBytes32(cfg.destinationSettler),
+          fillDeadline,
+          closedAuction: true,
+          data: "0x",
+        },
+      ],
+    );
+
+    const callData = encodeFunctionData({
+      abi: T1ERC7683_ABI,
+      functionName: "open",
+      args: [
+        {
+          fillDeadline,
+          orderDataType: ORDER_DATA_TYPEHASH,
+          orderData: encodedOrderData,
+        },
+      ],
+    });
+
+    const nonce = startNonce + i;
+
+    const request = await publicClient.prepareTransactionRequest({
+      account,
+      to: cfg.t1Erc7683,
+      data: callData,
+      value: 0n,
+      nonce,
+      maxFeePerGas,
+      maxPriorityFeePerGas,
+    });
+
+    const signed = await walletClient.signTransaction(request);
+    signedTxs.push(signed);
+  }
+
+  // Broadcast burst
+  let sent = 0;
+  const hashes: Hex[] = new Array(TX_COUNT);
+
+  async function worker(workerId: number) {
+    for (;;) {
+      const idx = sent++;
+      if (idx >= signedTxs.length) return;
+
+      const raw = signedTxs[idx]!;
+      const hash = await publicClient.sendRawTransaction({ serializedTransaction: raw });
+      hashes[idx] = hash;
+
+      console.log(`[${cfg.name}] worker=${workerId} open() ${idx + 1}/${TX_COUNT} hash=${hash}`);
+    }
+  }
+
+  const workers = Array.from({ length: Math.min(TX_CONCURRENCY, TX_COUNT) }, (_, i) => worker(i));
+  const t0 = Date.now();
+  await Promise.all(workers);
+  const t1 = Date.now();
+
+  console.log(`[${cfg.name}] broadcasted ${TX_COUNT} open() tx in ${t1 - t0}ms`);
+
+  // Optional: wait + show block spread
+  const receipts = await Promise.all(hashes.map((h) => publicClient.waitForTransactionReceipt({ hash: h })));
+  const blocks = receipts.map((r) => r.blockNumber);
+  const minBlock = blocks.reduce((a, b) => (a < b ? a : b));
+  const maxBlock = blocks.reduce((a, b) => (a > b ? a : b));
+  console.log(`[${cfg.name}] inclusion spread: minBlock=${minBlock} maxBlock=${maxBlock} span=${maxBlock - minBlock}`);
+
+  return { hashes, receipts };
+}
+
+async function main() {
+  const baseT1 = asAddress(requireEnv("BASE_T1_ERC7683_CONTRACT_ADDRESS"));
+  const arbT1 = asAddress(requireEnv("ARBITRUM_T1_ERC7683_CONTRACT_ADDRESS"));
+
+  const baseCfg: ChainCfg = {
+    name: "Base (Base→Arb intents)",
+    chain: base,
+    wsUrl: requireEnv("BASE_WS"),
+    privateKey: asHexPrivateKey(requireEnv("BASE_SIGNER_PRIVATE_KEY")),
+    t1Erc7683: baseT1,
+    inputToken: asAddress(requireEnv("BASE_INPUT_TOKEN")),
+    outputToken: asAddress(requireEnv("ARB_INPUT_TOKEN")), // output token lives on destination
+    destinationSettler: asAddress(process.env.ARB_DESTINATION_SETTLER ?? arbT1),
+    originDomain: base.id,
+    destinationDomain: arbitrum.id,
+  };
+
+  const arbCfg: ChainCfg = {
+    name: "Arbitrum (Arb→Base intents)",
+    chain: arbitrum,
+    wsUrl: requireEnv("ARBITRUM_WS"),
+    privateKey: asHexPrivateKey(requireEnv("ARBITRUM_SIGNER_PRIVATE_KEY")),
+    t1Erc7683: arbT1,
+    inputToken: asAddress(requireEnv("ARB_INPUT_TOKEN")),
+    outputToken: asAddress(requireEnv("BASE_INPUT_TOKEN")), // output token lives on destination
+    destinationSettler: asAddress(process.env.BASE_DESTINATION_SETTLER ?? baseT1),
+    originDomain: arbitrum.id,
+    destinationDomain: base.id,
+  };
+
+  // Run both bursts in parallel so they line up in time as tightly as possible.
+  await Promise.all([runChain(baseCfg), runChain(arbCfg)]);
+  console.log("Done.");
+}
+
+main().catch((e) => {
+  console.error(e);
+  process.exit(1);
+});
diff --git a/contracts/script/test/7683/concurrentintents/package.json b/contracts/script/test/7683/concurrentintents/package.json
new file mode 100644
index 00000000..41fa6a80
--- /dev/null
+++ b/contracts/script/test/7683/concurrentintents/package.json
@@ -0,0 +1,15 @@
+{
+  "name": "concurrentintents",
+  "module": "index.ts",
+  "type": "module",
+  "private": true,
+  "devDependencies": {
+    "@types/bun": "latest"
+  },
+  "peerDependencies": {
+    "typescript": "^5"
+  },
+  "dependencies": {
+    "viem": "^2.44.2"
+  }
+}
diff --git a/contracts/script/test/7683/concurrentintents/tsconfig.json b/contracts/script/test/7683/concurrentintents/tsconfig.json
new file mode 100644
index 00000000..bfa0fead
--- /dev/null
+++ b/contracts/script/test/7683/concurrentintents/tsconfig.json
@@ -0,0 +1,29 @@
+{
+  "compilerOptions": {
+    // Environment setup & latest features
+    "lib": ["ESNext"],
+    "target": "ESNext",
+    "module": "Preserve",
+    "moduleDetection": "force",
+    "jsx": "react-jsx",
+    "allowJs": true,
+
+    // Bundler mode
+    "moduleResolution": "bundler",
+    "allowImportingTsExtensions": true,
+    "verbatimModuleSyntax": true,
+    "noEmit": true,
+
+    // Best practices
+    "strict": true,
+    "skipLibCheck": true,
+    "noFallthroughCasesInSwitch": true,
+    "noUncheckedIndexedAccess": true,
+    "noImplicitOverride": true,
+
+    // Some stricter flags (disabled by default)
+    "noUnusedLocals": false,
+    "noUnusedParameters": false,
+    "noPropertyAccessFromIndexSignature": false
+  }
+}