test: dedupe anthropic transport mock reads

src/agents/anthropic-transport-stream.test.ts

@@ -74,6 +74,16 @@ function latestAnthropicRequestHeaders() {
   return new Headers(latestAnthropicRequest().init?.headers);
 }
 
+function guardedFetchCall(
+  callIndex = 0,
+): [unknown, { method?: unknown; headers?: HeadersInit } | undefined] {
+  const call = guardedFetchMock.mock.calls[callIndex];
+  if (!call) {
+    throw new Error(`expected guarded fetch call ${callIndex + 1}`);
+  }
+  return call as [unknown, { method?: unknown; headers?: HeadersInit } | undefined];
+}
+
 function requireRecord(value: unknown, label: string): Record<string, unknown> {
   if (!value || typeof value !== "object" || Array.isArray(value)) {
     throw new Error(`Expected ${label}`);
@@ -178,7 +188,7 @@ describe("anthropic transport stream", () => {
     );
 
     expect(buildGuardedModelFetchMock).toHaveBeenCalledWith(model);
-    const [url, init] = guardedFetchMock.mock.calls.at(0) ?? [];
+    const [url, init] = guardedFetchCall();
     expect(url).toBe("https://api.anthropic.com/v1/messages");
     expect(init?.method).toBe("POST");
     const headers = new Headers(init?.headers);
@@ -241,8 +251,9 @@ describe("anthropic transport stream", () => {
       } as AnthropicStreamOptions,
     );
 
-    expect(guardedFetchMock.mock.calls.at(0)?.[0]).toBe("https://custom-proxy.example/v1/messages");
-    expect(guardedFetchMock.mock.calls.at(0)?.[1]?.method).toBe("POST");
+    const [url, init] = guardedFetchCall();
+    expect(url).toBe("https://custom-proxy.example/v1/messages");
+    expect(init?.method).toBe("POST");
     expect(latestAnthropicRequestHeaders().get("anthropic-beta")).toBeNull();
   });
 
@@ -468,8 +479,9 @@ describe("anthropic transport stream", () => {
     );
     const result = await stream.result();
 
-    expect(guardedFetchMock.mock.calls.at(0)?.[0]).toBe("https://api.anthropic.com/v1/messages");
-    const headers = new Headers(guardedFetchMock.mock.calls.at(0)?.[1]?.headers);
+    const [url, init] = guardedFetchCall();
+    expect(url).toBe("https://api.anthropic.com/v1/messages");
+    const headers = new Headers(init?.headers);
     expect(headers.get("authorization")).toBe("Bearer sk-ant-oat-example");
     expect(headers.get("x-app")).toBe("cli");
     expect(headers.get("user-agent")).toContain("claude-cli/");