diff --git a/extensions/xai/index.test.ts b/extensions/xai/index.test.ts
index 1dea1d530f0..8ef1cc4d225 100644
--- a/extensions/xai/index.test.ts
+++ b/extensions/xai/index.test.ts
@@ -1,8 +1,11 @@
-import type { StreamFn } from "@mariozechner/pi-agent-core";
-import type { Context, Model } from "@mariozechner/pi-ai";
 import { describe, expect, it } from "vitest";
 import { registerSingleProviderPlugin } from "../../test/helpers/plugins/plugin-registration.js";
 import plugin from "./index.js";
+import {
+  createXaiPayloadCaptureStream,
+  expectXaiFastToolStreamShaping,
+  runXaiGrok4ResponseStream,
+} from "./test-helpers.js";
 
 function createProviderModel(overrides: {
   id: string;
@@ -59,54 +62,17 @@ describe("xai provider plugin", () => {
 
   it("wires provider stream shaping for fast mode and tool-stream defaults", async () => {
     const provider = await registerSingleProviderPlugin(plugin);
-    let capturedModelId = "";
-    let capturedPayload: Record<string, unknown> | undefined;
-    const baseStreamFn: StreamFn = (model, _context, options) => {
-      capturedModelId = model.id;
-      const payload: Record<string, unknown> = {
-        reasoning: { effort: "high" },
-        tools: [
-          {
-            type: "function",
-            function: {
-              name: "write",
-              parameters: { type: "object", properties: {} },
-              strict: true,
-            },
-          },
-        ],
-      };
-      options?.onPayload?.(payload as never, model as never);
-      capturedPayload = payload;
-      return {
-        result: async () => ({}) as never,
-        async *[Symbol.asyncIterator]() {},
-      } as unknown as ReturnType<StreamFn>;
-    };
+    const capture = createXaiPayloadCaptureStream();
 
     const wrapped = provider.wrapStreamFn?.({
       provider: "xai",
       modelId: "grok-4",
       extraParams: { fastMode: true },
-      streamFn: baseStreamFn,
+      streamFn: capture.streamFn,
     } as never);
 
-    void wrapped?.(
-      {
-        api: "openai-responses",
-        provider: "xai",
-        id: "grok-4",
-      } as Model<"openai-responses">,
-      { messages: [] } as Context,
-      {},
-    );
-
-    expect(capturedModelId).toBe("grok-4-fast");
-    expect(capturedPayload).toMatchObject({ tool_stream: true });
-    expect(capturedPayload).not.toHaveProperty("reasoning");
-    expect(
-      (capturedPayload?.tools as Array<{ function?: Record<string, unknown> }>)[0]?.function,
-    ).not.toHaveProperty("strict");
+    runXaiGrok4ResponseStream(wrapped);
+    expectXaiFastToolStreamShaping(capture);
   });
 
   it("defaults tool_stream extra params but preserves explicit values", async () => {
diff --git a/extensions/xai/stream.test.ts b/extensions/xai/stream.test.ts
index 8d19965ece8..520f800b229 100644
--- a/extensions/xai/stream.test.ts
+++ b/extensions/xai/stream.test.ts
@@ -6,14 +6,11 @@ import {
   createXaiToolPayloadCompatibilityWrapper,
   wrapXaiProviderStream,
 } from "./stream.js";
-
-type ToolPayload = {
-  function?: Record<string, unknown>;
-};
-type XaiTestPayload = Record<string, unknown> & {
-  tools?: Array<{ type?: string; function?: Record<string, unknown> }>;
-  input?: unknown[];
-};
+import {
+  createXaiPayloadCaptureStream,
+  expectXaiFastToolStreamShaping,
+  runXaiGrok4ResponseStream,
+} from "./test-helpers.js";
 type XaiStreamApi = Extract<Api, "openai-completions" | "openai-responses">;
 
 function captureWrappedModelId(params: {
@@ -94,51 +91,15 @@ describe("xai stream wrappers", () => {
   });
 
   it("composes the xai provider stream chain from extra params", () => {
-    let capturedModelId = "";
-    let capturedPayload: XaiTestPayload | undefined;
-    const baseStreamFn: StreamFn = (model, _context, options) => {
-      capturedModelId = model.id;
-      const payload: XaiTestPayload = {
-        reasoning: { effort: "high" },
-        tools: [
-          {
-            type: "function",
-            function: {
-              name: "write",
-              parameters: { type: "object", properties: {} },
-              strict: true,
-            },
-          },
-        ],
-      };
-      options?.onPayload?.(payload as never, model as never);
-      capturedPayload = payload;
-      return {
-        result: async () => ({}) as never,
-        async *[Symbol.asyncIterator]() {},
-      } as unknown as ReturnType<StreamFn>;
-    };
+    const capture = createXaiPayloadCaptureStream();
 
     const wrapped = wrapXaiProviderStream({
-      streamFn: baseStreamFn,
+      streamFn: capture.streamFn,
       extraParams: { fastMode: true },
     } as never);
 
-    void wrapped?.(
-      {
-        api: "openai-responses",
-        provider: "xai",
-        id: "grok-4",
-      } as Model<"openai-responses">,
-      { messages: [] } as Context,
-      {},
-    );
-
-    expect(capturedModelId).toBe("grok-4-fast");
-    expect(capturedPayload).toMatchObject({ tool_stream: true });
-    expect(capturedPayload).not.toHaveProperty("reasoning");
-    const payloadTools = capturedPayload?.tools as ToolPayload[] | undefined;
-    expect(payloadTools?.[0]?.function).not.toHaveProperty("strict");
+    runXaiGrok4ResponseStream(wrapped);
+    expectXaiFastToolStreamShaping(capture);
   });
 
   it("strips unsupported strict and reasoning controls from tool payloads", () => {
diff --git a/extensions/xai/test-helpers.ts b/extensions/xai/test-helpers.ts
new file mode 100644
index 00000000000..77848a1a8ac
--- /dev/null
+++ b/extensions/xai/test-helpers.ts
@@ -0,0 +1,73 @@
+import type { StreamFn } from "@mariozechner/pi-agent-core";
+import type { Context, Model } from "@mariozechner/pi-ai";
+import { expect } from "vitest";
+
+export type XaiToolPayloadFunction = {
+  function?: Record<string, unknown>;
+};
+
+export type XaiTestPayload = Record<string, unknown> & {
+  tools?: Array<{ type?: string; function?: Record<string, unknown> }>;
+  input?: unknown[];
+};
+
+export function createXaiToolStreamPayload(): XaiTestPayload {
+  return {
+    reasoning: { effort: "high" },
+    tools: [
+      {
+        type: "function",
+        function: {
+          name: "write",
+          parameters: { type: "object", properties: {} },
+          strict: true,
+        },
+      },
+    ],
+  };
+}
+
+export function createXaiPayloadCaptureStream() {
+  let capturedModelId = "";
+  let capturedPayload: XaiTestPayload | undefined;
+
+  const streamFn: StreamFn = (model, _context, options) => {
+    capturedModelId = model.id;
+    const payload = createXaiToolStreamPayload();
+    options?.onPayload?.(payload as never, model as never);
+    capturedPayload = payload;
+    return {
+      result: async () => ({}) as never,
+      async *[Symbol.asyncIterator]() {},
+    } as unknown as ReturnType<StreamFn>;
+  };
+
+  return {
+    streamFn,
+    getCapturedModelId: () => capturedModelId,
+    getCapturedPayload: () => capturedPayload,
+  };
+}
+
+export function runXaiGrok4ResponseStream(streamFn: StreamFn | undefined) {
+  void streamFn?.(
+    {
+      api: "openai-responses",
+      provider: "xai",
+      id: "grok-4",
+    } as Model<"openai-responses">,
+    { messages: [] } as Context,
+    {},
+  );
+}
+
+export function expectXaiFastToolStreamShaping(
+  capture: ReturnType<typeof createXaiPayloadCaptureStream>,
+) {
+  const capturedPayload = capture.getCapturedPayload();
+  expect(capture.getCapturedModelId()).toBe("grok-4-fast");
+  expect(capturedPayload).toMatchObject({ tool_stream: true });
+  expect(capturedPayload).not.toHaveProperty("reasoning");
+  const payloadTools = capturedPayload?.tools as XaiToolPayloadFunction[] | undefined;
+  expect(payloadTools?.[0]?.function).not.toHaveProperty("strict");
+}