Build a coding Agent

const agent = await client.agents.get(agentId);
await client.agents.update(agentId, {
  tools: agent.tools.includes("file_operation_sandbox")
    ? agent.tools : [...agent.tools, "file_operation_sandbox" as const],
});
const turn = await client.chat({
  agentId,
  message: { id: crypto.randomUUID(), role: "user", parts: [{
    type: "text", text: "Use write to create status.txt containing PENDING plus a newline. "
      + "Use edit to replace PENDING with READY. Verify it with read, grep for READY, "
      + "and glob for status.txt. Run `wc -c < status.txt` with bash. Then summarize.",
  }] },
});
const sessionId = await turn.sessionId;
for await (const _chunk of turn.toUIMessageStream()) { /* drain */ }
const { data } = await client.sessions.messages(agentId, sessionId);
const parts = data.flatMap((message) => message.parts);
const result = (name: string) => parts.find((part) =>
  part.type === `tool-${name}` && part.state === "output-available")?.output;
const isRecord = (value: unknown): value is Record<string, unknown> =>
  typeof value === "object" && value !== null;
const has = (name: string, key: string, expected: unknown) => {
  const output = result(name);
  return isRecord(output) && output[key] === expected;
};
if (!has("write", "bytesWritten", 8) || !has("edit", "replacements", 1)) throw new Error("change failed");
if (!(JSON.stringify(result("grep")) ?? "").includes("READY")
  || !(JSON.stringify(result("glob")) ?? "").includes("/status.txt")) throw new Error("search failed");
if (!has("read", "content", "READY\n")) throw new Error("read failed");
if (!has("bash", "stdout", "6\n") || !has("bash", "exitCode", 0)) throw new Error("bash failed");