langchain-code-interpreter

LangChain agent on Tenki (code interpreter)

A LangChain agent that writes Python and runs it in a disposable Tenki sandbox — the "code interpreter" pattern, with Tenki as the execution backend. One sandbox per agent session; a run_python tool the agent calls to execute code in an isolated microVM.

The tool (tenki-tool.mjs)

import { tool } from "@langchain/core/tools";
import { z } from "zod";
import { stdoutText, stderrText } from "@tenkicloud/sandbox";

export function makeCodeTool(sandbox) {
  return tool(
    async ({ code }) => {
      const res = await sandbox.exec("python3", { args: ["-c", code] });
      return `${stdoutText(res)}${stderrText(res)}`.trim() || `(exit ${res.exitCode})`;
    },
    {
      name: "run_python",
      description: "Execute Python in a sandbox and return its output.",
      schema: z.object({ code: z.string() }),
    },
  );
}

The agent (agent.mjs)

Create one sandbox, wire the tool into a LangGraph ReAct agent, ask something that needs real computation:

const agent = createReactAgent({
  llm: new ChatOpenAI({ model: "gpt-4o-mini" }),
  tools: [makeCodeTool(sandbox)],
});
const result = await agent.invoke({
  messages: [{ role: "user", content: "What is the 20th Fibonacci number? Compute it with Python." }],
});

Run it

npm install
export TENKI_AUTH_TOKEN=...                    # from `tenki login`
export TENKI_WORKSPACE_ID=...
export OPENAI_API_KEY=...                      # or swap ChatOpenAI for your provider
node agent.mjs

Verify (no LLM needed)

node verify.mjs   # calls the tool directly → runs Python in Tenki → asserts the output

This is what CI runs: it proves the Tenki integration end-to-end without a model key.

Notes

• One sandbox per session, reused across tool calls — cheaper than a sandbox per call; disposed when the agent finishes.
• exec("python3", { args: ["-c", code] }) passes the code as a single argument (no shell), so multi-line agent-generated code goes through without escaping issues.
• Stdlib only by default — sandboxes have no outbound network unless you pass allowOutbound: true (needed for pip install).
• Built on LangChain.js v1 + @tenkicloud/sandbox. The same tool-backed-by-a-sandbox pattern works in LangChain Python.