From 127bafa0b9aebaac32137441bb5a876c0c5e353b Mon Sep 17 00:00:00 2001
From: Peter Steinberger <steipete@gmail.com>
Date: Sat, 18 Apr 2026 22:05:51 +0100
Subject: [PATCH] test: dedupe vertex stream payload fixture

---
 src/agents/anthropic-vertex-stream.test.ts | 74 ++++++++++------------
 1 file changed, 34 insertions(+), 40 deletions(-)

diff --git a/src/agents/anthropic-vertex-stream.test.ts b/src/agents/anthropic-vertex-stream.test.ts
index c1cb3a0b60c..8e9717f718d 100644
--- a/src/agents/anthropic-vertex-stream.test.ts
+++ b/src/agents/anthropic-vertex-stream.test.ts
@@ -63,6 +63,33 @@ function makeModel(params: { id: string; maxTokens?: number }): Model<"anthropic
   } as Model<"anthropic-messages">;
 }
 
+const CACHE_BOUNDARY_PROMPT = `Stable prefix${SYSTEM_PROMPT_CACHE_BOUNDARY}Dynamic suffix`;
+
+type PayloadHook = (payload: unknown, payloadModel: unknown) => Promise<unknown>;
+
+function captureCacheBoundaryPayloadHook(onPayload: PayloadHook) {
+  const streamFn = createAnthropicVertexStreamFn("vertex-project", "us-east5");
+  const model = makeModel({ id: "claude-sonnet-4-6", maxTokens: 64000 });
+
+  void streamFn(
+    model,
+    {
+      systemPrompt: CACHE_BOUNDARY_PROMPT,
+      messages: [{ role: "user", content: "Hello" }],
+    } as never,
+    {
+      cacheRetention: "short",
+      onPayload,
+    } as never,
+  );
+
+  const transportOptions = hoisted.streamAnthropicMock.mock.calls[0]?.[2] as {
+    onPayload?: PayloadHook;
+  };
+
+  return { model, onPayload: transportOptions.onPayload };
+}
+
 describe("createAnthropicVertexStreamFn", () => {
   beforeAll(async () => {
     ({ createAnthropicVertexStreamFn, createAnthropicVertexStreamFnForModel } =
@@ -163,37 +190,20 @@ describe("createAnthropicVertexStreamFn", () => {
   });
 
   it("applies Anthropic cache-boundary shaping before forwarding payload hooks", async () => {
-    const streamFn = createAnthropicVertexStreamFn("vertex-project", "us-east5");
-    const model = makeModel({ id: "claude-sonnet-4-6", maxTokens: 64000 });
     const onPayload = vi.fn(async (payload: unknown) => payload);
-
-    void streamFn(
-      model,
-      {
-        systemPrompt: `Stable prefix${SYSTEM_PROMPT_CACHE_BOUNDARY}Dynamic suffix`,
-        messages: [{ role: "user", content: "Hello" }],
-      } as never,
-      {
-        cacheRetention: "short",
-        onPayload,
-      } as never,
-    );
-
-    const transportOptions = hoisted.streamAnthropicMock.mock.calls[0]?.[2] as {
-      onPayload?: (payload: unknown, payloadModel: unknown) => Promise<unknown>;
-    };
+    const { model, onPayload: transportPayloadHook } = captureCacheBoundaryPayloadHook(onPayload);
     const payload = {
       system: [
         {
           type: "text",
-          text: `Stable prefix${SYSTEM_PROMPT_CACHE_BOUNDARY}Dynamic suffix`,
+          text: CACHE_BOUNDARY_PROMPT,
           cache_control: { type: "ephemeral" },
         },
       ],
       messages: [{ role: "user", content: "Hello" }],
     };
 
-    const nextPayload = await transportOptions.onPayload?.(payload, model);
+    const nextPayload = await transportPayloadHook?.(payload, model);
 
     expect(onPayload).toHaveBeenCalledWith(
       {
@@ -251,39 +261,23 @@ describe("createAnthropicVertexStreamFn", () => {
   });
 
   it("reapplies Anthropic cache-boundary shaping when payload hooks return a fresh payload", async () => {
-    const streamFn = createAnthropicVertexStreamFn("vertex-project", "us-east5");
-    const model = makeModel({ id: "claude-sonnet-4-6", maxTokens: 64000 });
     const onPayload = vi.fn(async () => ({
       system: [
         {
           type: "text",
-          text: `Stable prefix${SYSTEM_PROMPT_CACHE_BOUNDARY}Dynamic suffix`,
+          text: CACHE_BOUNDARY_PROMPT,
         },
       ],
       messages: [{ role: "user", content: "Hello again" }],
     }));
+    const { model, onPayload: transportPayloadHook } = captureCacheBoundaryPayloadHook(onPayload);
 
-    void streamFn(
-      model,
-      {
-        systemPrompt: `Stable prefix${SYSTEM_PROMPT_CACHE_BOUNDARY}Dynamic suffix`,
-        messages: [{ role: "user", content: "Hello" }],
-      } as never,
-      {
-        cacheRetention: "short",
-        onPayload,
-      } as never,
-    );
-
-    const transportOptions = hoisted.streamAnthropicMock.mock.calls[0]?.[2] as {
-      onPayload?: (payload: unknown, payloadModel: unknown) => Promise<unknown>;
-    };
-    const nextPayload = await transportOptions.onPayload?.(
+    const nextPayload = await transportPayloadHook?.(
       {
         system: [
           {
             type: "text",
-            text: `Stable prefix${SYSTEM_PROMPT_CACHE_BOUNDARY}Dynamic suffix`,
+            text: CACHE_BOUNDARY_PROMPT,
           },
         ],
         messages: [{ role: "user", content: "Hello" }],