From 9e4e180da9c3359df71559be477b3ee9cf820b52 Mon Sep 17 00:00:00 2001
From: Omer Bektas <omerbkts61@hotmail.com>
Date: Mon, 17 Aug 2026 09:43:38 +0300
Subject: [PATCH] fix(viem): omit missing typed-data chainId

---
 src/provider/viem-adapter.ts       |  2 +-
 test/provider/viem-adapter.spec.ts | 39 ++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 1 deletion(-)
 create mode 100644 test/provider/viem-adapter.spec.ts

diff --git a/src/provider/viem-adapter.ts b/src/provider/viem-adapter.ts
index d25bc0ced..c1aba8f65 100644
--- a/src/provider/viem-adapter.ts
+++ b/src/provider/viem-adapter.ts
@@ -89,7 +89,7 @@ function createViemSigner(
       }
       return walletClient.signTypedData({
         domain: {
-          chainId: Number(domain.chainId),
+          chainId: domain.chainId != null ? Number(domain.chainId) : undefined,
           name: domain.name,
           version: domain.version,
           verifyingContract: domain.verifyingContract as `0x${string}`,
diff --git a/test/provider/viem-adapter.spec.ts b/test/provider/viem-adapter.spec.ts
new file mode 100644
index 000000000..7eb5d2ac7
--- /dev/null
+++ b/test/provider/viem-adapter.spec.ts
@@ -0,0 +1,39 @@
+import { describe, expect, it, vi } from "vitest"
+import { createViemWallet } from "../../src/provider/viem-adapter"
+
+describe("createViemWallet", () => {
+  it("does not pass NaN when typed-data domain omits chainId", async () => {
+    const signTypedData = vi.fn().mockResolvedValue("0xsignature")
+    const wallet = createViemWallet({
+      publicClient: {
+        waitForTransactionReceipt: vi.fn(),
+      } as any,
+      walletClient: {
+        account: {
+          address: "0x0000000000000000000000000000000000000001",
+        },
+        signTypedData,
+      } as any,
+    })
+
+    if (!("signer" in wallet)) {
+      throw new Error("expected wallet signer")
+    }
+
+    await wallet.signer.signTypedData(
+      {
+        name: "OpenSea",
+        version: "1",
+        verifyingContract: "0x0000000000000000000000000000000000000002",
+      } as any,
+      {
+        Test: [{ name: "value", type: "string" }],
+      },
+      { value: "hello" },
+    )
+
+    const call = signTypedData.mock.calls[0][0]
+    expect(call.domain.chainId).toBeUndefined()
+    expect(Number.isNaN(call.domain.chainId)).toBe(false)
+  })
+})