diff --git a/packages/cli/src/commands/tokenplan/assign-seats.ts b/packages/cli/src/commands/tokenplan/assign-seats.ts
index d453ae4..5dd1e76 100644
--- a/packages/cli/src/commands/tokenplan/assign-seats.ts
+++ b/packages/cli/src/commands/tokenplan/assign-seats.ts
@@ -165,7 +165,7 @@ function buildQueryParams(
   if (Array.isArray(accountIds) && accountIds.length > 0) {
     params.AccountIds = accountIds;
   } else if (typeof accountIds === "string" && accountIds.length > 0) {
-    params.AccountIds = accountIds;
+    params.AccountIds = [accountIds];
   }
 
   return params;
diff --git a/packages/cli/tests/e2e/tokenplan.e2e.test.ts b/packages/cli/tests/e2e/tokenplan.e2e.test.ts
index 1635bbf..e264cbf 100644
--- a/packages/cli/tests/e2e/tokenplan.e2e.test.ts
+++ b/packages/cli/tests/e2e/tokenplan.e2e.test.ts
@@ -328,6 +328,8 @@ describe("e2e: tokenplan dry-run", () => {
     expect(data.query?.WorkspaceId).toBe("ws_456");
     expect(data.query?.SeatType).toBe("standard");
     expect(data.query?.AccountIds).toEqual(["acc_1", "acc_2"]);
+    expect(data.endpoint).toMatch(/AccountIds\.1=acc_1/);
+    expect(data.endpoint).toMatch(/AccountIds\.2=acc_2/);
   });
 
   test("add-member --dry-run 输出 endpoint 和 query 参数", async () => {
diff --git a/packages/core/src/client/ak-sign.ts b/packages/core/src/client/ak-sign.ts
index d807ad3..1f55c46 100644
--- a/packages/core/src/client/ak-sign.ts
+++ b/packages/core/src/client/ak-sign.ts
@@ -28,9 +28,9 @@ export function buildCanonicalQuery(params: Record<string, string | string[] | u
   for (const [key, value] of Object.entries(params)) {
     if (value === undefined || value === "") continue;
     if (Array.isArray(value)) {
-      const sorted = [...value].sort();
-      for (const v of sorted) {
-        if (v !== "") pairs.push([key, v]);
+      for (let i = 0; i < value.length; i++) {
+        const v = value[i];
+        if (v !== "") pairs.push([`${key}.${i + 1}`, v]);
       }
     } else {
       pairs.push([key, value]);
diff --git a/packages/core/tests/ak-sign.test.ts b/packages/core/tests/ak-sign.test.ts
new file mode 100644
index 0000000..6633ee8
--- /dev/null
+++ b/packages/core/tests/ak-sign.test.ts
@@ -0,0 +1,20 @@
+import { expect, test } from "vite-plus/test";
+import { buildCanonicalQuery } from "../src/client/ak-sign.ts";
+
+test("buildCanonicalQuery flattens arrays as indexed keys", () => {
+  expect(
+    buildCanonicalQuery({
+      WorkspaceId: "ws_1",
+      SeatType: "pro",
+      AccountIds: ["acc_1", "acc_2"],
+    }),
+  ).toBe("AccountIds.1=acc_1&AccountIds.2=acc_2&SeatType=pro&WorkspaceId=ws_1");
+});
+
+test("buildCanonicalQuery uses single indexed key for one-element arrays", () => {
+  expect(
+    buildCanonicalQuery({
+      AccountIds: ["acc_2bd88814c31743d9aa5833dc16b3b8e0"],
+    }),
+  ).toBe("AccountIds.1=acc_2bd88814c31743d9aa5833dc16b3b8e0");
+});