diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 62f8b7cf..2ba87b98 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -12,6 +12,10 @@ permissions:
   id-token: write
   contents: read
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   test_unit:
     runs-on: ubuntu-latest
diff --git a/src/hooks/custom/FixArrayParamsHook.ts b/src/hooks/custom/FixArrayParamsHook.ts
new file mode 100644
index 00000000..dbff0eb6
--- /dev/null
+++ b/src/hooks/custom/FixArrayParamsHook.ts
@@ -0,0 +1,55 @@
+
+import {
+  type BeforeRequestContext,
+  BeforeRequestHook,
+} from "../types.js";
+import { prepareRequestHeaders } from "./utils/request.js";
+
+/**
+ * If the given key in FormData is present and contains a comma-separated list of values,
+ * split the values into separate entries with the key suffixed by "[]".
+ *
+ * @param formData - The FormData object to modify.
+ * @param key - The key to extract and split.
+ */
+function flattenArrayParameter(formData: FormData, key: string): void {
+  const value = formData.get(key);
+  if (formData && typeof value === "string" && value.includes(",")) {
+    formData.delete(key);
+    const values = value.split(",").map(v => v.trim()).filter(Boolean);
+    for (const v of values) {
+      formData.append(`${key}[]`, v);
+    }
+  }
+}
+/**
+ * Represents a hook for fixing array parameters before sending a request.
+ */
+export class FixArrayParamsHook implements BeforeRequestHook {
+  /**
+   * Fixes specific array parameters in the request.
+   * The SDK creates FormData with {extract_image_block_types: "a,b,c"},
+   * and the server expects it to be {extract_image_block_types[]: ["a", "b", "c"]}.
+   * Speakeasy will fix this upstream soon.
+   *
+   * @param _hookCtx - The context object for the hook, containing metadata about the request.
+   * @param request - The original Request object.
+   * @returns A new Request object with modified form data and headers.
+   */
+  async beforeRequest(
+    _hookCtx: BeforeRequestContext,
+    request: Request
+  ): Promise<Request> {
+    const requestClone = request.clone();
+    const formData = await requestClone.formData();
+
+    flattenArrayParameter(formData, "extract_image_block_types");
+
+    const headers = prepareRequestHeaders(requestClone);
+
+    return new Request(requestClone, {
+      body: formData,
+      headers: headers,
+    });
+  }
+}
diff --git a/src/hooks/custom/utils/request.ts b/src/hooks/custom/utils/request.ts
index 03a1dfde..b8f6a65d 100644
--- a/src/hooks/custom/utils/request.ts
+++ b/src/hooks/custom/utils/request.ts
@@ -1,5 +1,4 @@
 import {
-  EXTRACT_IMAGE_BLOCK_TYPES,
   PARTITION_FORM_FILES_KEY,
   PARTITION_FORM_SPLIT_PDF_PAGE_KEY,
   PARTITION_FORM_STARTING_PAGE_NUMBER_KEY,
@@ -90,13 +89,5 @@ export async function prepareRequestBody(
     startingPageNumber.toString()
   );
 
-  if (formData.has(EXTRACT_IMAGE_BLOCK_TYPES)) {
-    newFormData.delete(EXTRACT_IMAGE_BLOCK_TYPES);
-    const extractImageBlockTypes = (formData.get(EXTRACT_IMAGE_BLOCK_TYPES)?.toString() || "").split(",");
-    for(const blockType of extractImageBlockTypes) {
-      newFormData.append(EXTRACT_IMAGE_BLOCK_TYPES, blockType);
-    }
-  }
-
   return newFormData;
 }
diff --git a/src/hooks/registration.ts b/src/hooks/registration.ts
index 26dba7ff..ae4f7438 100644
--- a/src/hooks/registration.ts
+++ b/src/hooks/registration.ts
@@ -3,6 +3,7 @@ import { Hooks } from "./types.js";
 import { LoggerHook } from "./custom/LoggerHook.js";
 import { SplitPdfHook } from "./custom/SplitPdfHook.js";
 import { HttpsCheckHook } from "./custom/HttpsCheckHook.js";
+import { FixArrayParamsHook } from "./custom/FixArrayParamsHook.js";
 
 /*
  * This file is only ever generated once on the first generation and then is free to be modified.
@@ -19,6 +20,7 @@ export function initHooks(hooks: Hooks) {
   const loggerHook = new LoggerHook();
   const splitPdfHook = new SplitPdfHook();
   const httpsCheckHook = new HttpsCheckHook();
+  const fixArrayParamsHook = new FixArrayParamsHook();
 
   // NOTE: logger_hook should stay registered last as logs the status of
   // request and whether it will be retried which can be changed by e.g. split_pdf_hook
@@ -28,6 +30,7 @@ export function initHooks(hooks: Hooks) {
   hooks.registerSDKInitHook(splitPdfHook);
 
   // Register before request hooks
+  hooks.registerBeforeRequestHook(fixArrayParamsHook)
   hooks.registerBeforeRequestHook(splitPdfHook);
 
   // Register after success hooks
diff --git a/test/unit/FixArrayParamsHook.test.ts b/test/unit/FixArrayParamsHook.test.ts
new file mode 100644
index 00000000..e263a1ba
--- /dev/null
+++ b/test/unit/FixArrayParamsHook.test.ts
@@ -0,0 +1,68 @@
+import { readFileSync } from "fs";
+
+import { UnstructuredClient } from "../../src";
+import { PartitionResponse } from "../../src/sdk/models/operations";
+import { PartitionParameters, Strategy } from "../../src/sdk/models/shared";
+import { describe, it, expect, vi, beforeEach} from 'vitest';
+
+describe("FixArrayParamsHook unit tests", () => {
+    beforeEach(() => {
+        // Reset the mock before each test
+        vi.resetAllMocks();
+    });
+
+    // Assert that array parameters are sent in the correct format
+    // This should work with and without pdf splitting
+    it.each([
+      {splitPdfPage: false},
+      {splitPdfPage: true},
+    ])(
+    "should send extract_image_block_types in the correct format", async ({splitPdfPage}) => {
+      const client = new UnstructuredClient({});
+
+      const file = {
+        content: readFileSync("test/data/layout-parser-paper-fast.pdf"),
+        fileName: "test/data/layout-parser-paper-fast.pdf",
+      };
+
+      const requestParams: PartitionParameters = {
+        files: file,
+        strategy: Strategy.Fast,
+        extractImageBlockTypes: ["a", "b", "c"],
+        splitPdfPage: splitPdfPage,
+      };
+
+      const fetchMock = vi.fn().mockResolvedValue(
+        new Response(
+          JSON.stringify([
+            {
+              type: "Image",
+              element_id: "2fe9cbfbf0ff1bd64cc4705347dbd1d6",
+              text: "This is a test",
+              metadata: {},
+            },
+          ]),
+          {
+            status: 200,
+            headers: { "Content-Type": "application/json" },
+          }
+        )
+      );
+
+      vi.stubGlobal("fetch", fetchMock);
+
+      const res: PartitionResponse = await client.general.partition({
+        partitionParameters: requestParams,
+      });
+
+      expect(fetchMock).toHaveBeenCalledTimes(1);
+
+      const request = fetchMock.mock.calls[0][0];
+      const formData = await request.formData();
+      const extract_image_block_types = formData.getAll(
+        "extract_image_block_types[]"
+      );
+
+      expect(extract_image_block_types).toEqual(["a", "b", "c"]);
+    });
+});