examples: hello.ts — the smallest useful ComputerAgent program

45 lines (incl. comments + blank lines). ~25 lines of real code.

Replaces the need to wade through security-agent.ts (169 lines) or
binary-artifact-demo.ts (170 lines) just to learn the shape. Covers
everything a first-touch user actually needs:

  - Inline agent definition (no GitHub repo to clone, no GAP folder
    structure to learn)
  - LocalSubstrate (no Docker, no E2B account, no Tart VM)
  - The Claude Agent SDK engine end-to-end — Write tool included
  - agent.fetchArtifactText() to read back what the agent produced
  - usage rollup printed at the end so people see token + cost data
    from line one

Live-validated against the real Anthropic API:

  $ bun run examples/hello.ts
  Types protect the code
  Errors caught at compile time
  Fewer runtime bugs

  984 tokens • $0.0468 • session sess_...

The other examples stay — they prove richer use cases (multi-turn
marketing, security audit, binary artifacts, session resume). But
hello.ts is now THE canonical entry point.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: kapaleshreyas

examples/hello.ts

@@ -0,0 +1,45 @@
+/**
+ * The smallest useful ComputerAgent program.
+ *
+ *   ANTHROPIC_API_KEY=sk-ant-... bun run examples/hello.ts
+ *
+ * Tell the agent to write something to a file, then read it back. Shows the
+ * full loop in ~20 lines: define an agent inline, run it locally with the
+ * Claude Agent SDK engine, fetch the file the agent produced. No GitHub
+ * repo, no Docker, no E2B account — just the API key.
+ */
+import { ComputerAgent, LocalSubstrate } from "computeragent";
+
+const ANTHROPIC_API_KEY = process.env.ANTHROPIC_API_KEY;
+if (!ANTHROPIC_API_KEY) throw new Error("Set ANTHROPIC_API_KEY first.");
+
+await using agent = new ComputerAgent({
+  source: {
+    type: "inline",
+    manifest: { name: "haiku-bot", version: "0.1.0" },
+    files: {
+      "agent.yaml": [
+        'spec_version: "0.1.0"',
+        "name: haiku-bot",
+        "version: 0.1.0",
+        "model:",
+        "  preferred: claude-haiku-4-5-20251001",
+      ].join("\n"),
+      "SOUL.md": "Write the requested content to the requested file with the Write tool. Stay terse.",
+    },
+  },
+  harness: "claude-agent-sdk",
+  runtime: new LocalSubstrate(),
+  envs: { ANTHROPIC_API_KEY },
+  options: { permissionMode: "bypassPermissions" },
+});
+
+const result = await agent.chat('Write a 3-line haiku about TypeScript to "haiku.txt".');
+const haiku = await agent.fetchArtifactText("haiku.txt");
+
+console.log(`\n${haiku ?? "(no file produced)"}\n`);
+console.log(
+  `${result.usage.inputTokens + result.usage.outputTokens} tokens • ` +
+    `$${result.usage.costUsd?.toFixed(4) ?? "?"} • ` +
+    `session ${result.sessionId}`,
+);

examples/package.json

@@ -4,6 +4,7 @@
   "private": true,
   "type": "module",
   "scripts": {
+    "hello": "bun run hello.ts",
     "wedge1": "bun run wedge1-server.ts",
     "marketing-agent": "bun run marketing-agent.ts",
     "security-agent": "bun run security-agent.ts",