ACPX extension: split ACP stream parser and test fixtures

extensions/acpx/src/runtime-internals/control-errors.test.ts

@@ -0,0 +1,25 @@
+import { describe, expect, it } from "vitest";
+import { parseControlJsonError } from "./control-errors.js";
+
+describe("parseControlJsonError", () => {
+  it("reads structured control-command errors", () => {
+    expect(
+      parseControlJsonError({
+        error: {
+          code: "NO_SESSION",
+          message: "No matching session",
+          retryable: false,
+        },
+      }),
+    ).toEqual({
+      code: "NO_SESSION",
+      message: "No matching session",
+      retryable: false,
+    });
+  });
+
+  it("returns null when payload has no error object", () => {
+    expect(parseControlJsonError({ action: "session_ensured" })).toBeNull();
+    expect(parseControlJsonError("bad")).toBeNull();
+  });
+});