DX-3099: add Amp custom harness example

packages/sdk/examples/custom-amp-agent.ts

@@ -0,0 +1,179 @@
+import { Agent, Box } from "@upstash/box";
+
+// Amp custom agent harness (ampcode.com)
+//
+// Runs the Amp CLI in execute mode and translates its Claude Code-compatible
+// stream JSON into box-sse-v1 events. Box sessions map to Amp threads.
+// MCP servers are passed with --mcp-config; prompt files are inlined (text)
+// or saved under /workspace/home/.box-attachments (images, PDFs).
+//
+// Needs AMP_API_KEY: an access token from ampcode.com/settings (Security),
+// starts with sgamp_. The model is an Amp mode: low, medium, high, or ultra.
+//
+// Cost is reported as 0: Amp's stream JSON has token counts but no price. Amp
+// bills in credits; `amp threads usage <thread-id>` shows a thread's cost.
+
+const agentSource = String.raw`
+import { spawn } from "child_process";
+import { randomUUID } from "crypto";
+import { mkdirSync, readFileSync, unlinkSync, writeFileSync } from "fs";
+import { basename } from "path";
+import { createInterface } from "readline";
+
+const WORK_DIR = "/workspace/home";
+const ATTACHMENTS_DIR = WORK_DIR + "/.box-attachments";
+const MCP_CONFIG_PATH = WORK_DIR + "/.box-internal/mcp-config.json";
+
+const args = process.argv.slice(2);
+const readArg = (name) => {
+  const i = args.indexOf(name);
+  return i >= 0 ? args[i + 1] : undefined;
+};
+const mode = readArg("--model");
+const session = readArg("--session");
+
+const emit = (event, data) => process.stdout.write("event: " + event + "\ndata: " + JSON.stringify(data) + "\n\n");
+
+const TEXT_TYPES = ["application/json", "application/javascript", "application/typescript",
+  "application/xml", "application/yaml", "application/toml", "application/sql"];
+const isText = (mime) => mime.startsWith("text/") || TEXT_TYPES.includes(mime.split(";")[0]);
+
+// Text files are inlined; other files (images, PDFs) are saved so Amp can read them by path.
+function buildPrompt(base) {
+  const filesPath = process.env.PROMPT_FILES_PATH;
+  if (!filesPath) return base;
+  const files = JSON.parse(readFileSync(filesPath, "utf-8"));
+  try { unlinkSync(filesPath); } catch {}
+  const fence = String.fromCharCode(96, 96, 96);
+  let prompt = base;
+  files.forEach((f, i) => {
+    const name = basename(f.filename || "file-" + i);
+    const data = Buffer.from(f.data, "base64");
+    if (isText(f.media_type)) {
+      prompt += "\n\nAttached file: " + name + "\n" + fence + "\n" + data.toString("utf-8") + "\n" + fence;
+    } else {
+      const dir = ATTACHMENTS_DIR + "/" + randomUUID();
+      mkdirSync(dir, { recursive: true });
+      writeFileSync(dir + "/" + name, data);
+      prompt += "\n\nAttached file: " + dir + "/" + name;
+    }
+  });
+  return prompt;
+}
+
+function mcpConfig() {
+  let servers;
+  try { servers = JSON.parse(readFileSync(MCP_CONFIG_PATH, "utf-8")); } catch { return []; }
+  const config = {};
+  for (const s of servers) {
+    config[s.name] = s.source === "npm"
+      ? { command: "npx", args: ["-y", s.package_or_url, ...(s.args ?? [])], env: s.headers ?? {} }
+      : { url: s.package_or_url, headers: s.headers ?? {} };
+  }
+  return servers.length ? ["--mcp-config", JSON.stringify(config)] : [];
+}
+
+if (process.env.JSON_SCHEMA) console.error("[amp] Warning: JSON_SCHEMA is not supported by the Amp harness");
+if (process.env.AGENT_OPTIONS) console.error("[amp] Warning: AGENT_OPTIONS are not supported by the Amp harness");
+
+const ampArgs = [
+  ...(session ? ["threads", "continue", session] : ["--no-archive-after-execute"]),
+  "--dangerously-allow-all",
+  "--stream-json",
+  ...mcpConfig(),
+  ...(mode && mode !== "custom" ? ["-m", mode] : []),
+  "-x", buildPrompt(readArg("-p") ?? ""),
+];
+
+const amp = spawn("amp", ampArgs, { cwd: WORK_DIR, stdio: ["ignore", "pipe", "pipe"] });
+
+let stderr = "";
+amp.stderr.on("data", (d) => { stderr = (stderr + d).slice(-4000); });
+
+let threadId = session ?? "";
+let output = "";
+let inputTokens = 0, outputTokens = 0, cachedInputTokens = 0;
+let finished = false;
+
+for await (const line of createInterface({ input: amp.stdout })) {
+  let event;
+  try { event = JSON.parse(line); } catch { continue; }
+  if (event.session_id) threadId = event.session_id;
+
+  if (event.type === "assistant") {
+    const usage = event.message?.usage ?? {};
+    inputTokens += (usage.input_tokens ?? 0) + (usage.cache_creation_input_tokens ?? 0);
+    cachedInputTokens += usage.cache_read_input_tokens ?? 0;
+    outputTokens += usage.output_tokens ?? 0;
+    for (const part of event.message?.content ?? []) {
+      if (part.type === "text") emit("text", { text: part.text });
+      if (part.type === "tool_use") emit("tool", { name: part.name, toolCallId: part.id, input: part.input ?? {} });
+    }
+  } else if (event.type === "user") {
+    for (const part of event.message?.content ?? []) {
+      if (part.type !== "tool_result") continue;
+      const content = typeof part.content === "string" ? part.content : JSON.stringify(part.content);
+      emit("tool_result", { toolCallId: part.tool_use_id, output: content, is_error: part.is_error ?? false });
+    }
+  } else if (event.type === "result") {
+    finished = true;
+    const meta = { input_tokens: inputTokens, output_tokens: outputTokens, cached_input_tokens: cachedInputTokens, total_cost_usd: 0, session_id: threadId };
+    if (event.is_error) emit("error", { error: event.error ?? event.result ?? "Amp run failed", ...meta });
+    else emit("done", { output: event.result ?? output, ...meta });
+  }
+}
+
+const code = await new Promise((resolve) => amp.on("close", resolve));
+if (!finished) {
+  emit("error", { error: "amp exited with code " + code + ": " + stderr.trim().split("\n").slice(-5).join("\n"), session_id: threadId });
+  process.exit(1);
+}
+`;
+
+const box = await Box.create({
+  apiKey: process.env.UPSTASH_BOX_API_KEY!,
+  baseUrl: process.env.UPSTASH_BOX_BASE_URL,
+  runtime: "node",
+  agent: {
+    harness: Agent.Custom,
+    model: "medium",
+    customHarness: {
+      command: "node",
+      args: ["/workspace/home/custom-amp-agent.mjs"],
+      protocol: "box-sse-v1",
+    },
+  },
+  env: {
+    AMP_API_KEY: process.env.AMP_API_KEY!,
+  },
+});
+
+console.log(`Created box: ${box.id}`);
+
+try {
+  console.log("Installing Amp...");
+  await box.exec.command("sudo -n npm install -g @sourcegraph/amp");
+
+  await box.files.write({
+    path: "custom-amp-agent.mjs",
+    content: agentSource,
+  });
+
+  console.log("\n=== Turn 1 ===");
+  const run1 = await box.agent.run({
+    prompt: "Create a file called hello.txt with the content 'Hello from Amp!'",
+  });
+  console.log(run1.result);
+
+  console.log("\n=== Turn 2 (follow-up) ===");
+  const stream = await box.agent.stream({
+    prompt: "Now read back the file you just created.",
+  });
+  for await (const chunk of stream) {
+    if (chunk.type === "text-delta") process.stdout.write(chunk.text);
+  }
+  console.log();
+} finally {
+  await box.delete();
+  console.log("\nBox deleted.");
+}