OpenAI Agents API with Bring Your Own Sandbox as a backend for a 'software factory'

Melvin Vivas · X post · 2026-09-12 · Open on X

Topics: AI Agents, Tool Use & MCP, AI System Design & Architecture, AI Dev Tools & Productivity · Level: intermediate

Summary

The creator plans to use OpenAI's newly launched Agents API as the backend for a 'Software Factory' app whose UI was generated by Codex with GPT-6 Astra (Ultra). The Agents API supports BYOS (Bring Your Own Sandbox), so agents can run code in sandbox providers such as Blaxel, Cloudflare, Daytona, E2B, Modal and Vercel.

Key points

• OpenAI launched an Agents API meant to be the backend for apps that build software with agents.
• It supports BYOS (Bring Your Own Sandbox): plug in Blaxel, Cloudflare, Daytona, E2B, Modal or Vercel to run code.
• The creator first had Codex with Astra (Ultra) build only the UI of a Software Factory app, then picked a backend.
• A useful workflow: prototype the UI with a coding agent first, then connect an agent API backend.

Resources mentioned

• Introducing the Agents API (OpenAI) · article · openai.com · free
  OpenAI's official announcement of the Agents API, which supports bring-your-own-sandbox providers.
• OpenAI · tool · x.com · free
  An AI model provider whose models can be used through managed connectors.
  Also in: Creator's favorite OpenAI DevDay announcements (Melvin Vivas on X · notes), Building Software Factories on the OpenAI Agents API (Codex-Powered) (Melvin Vivas on X · notes), Coworker: Free Local-First Desktop App for Running AI Agents (Melvin Vivas on X · notes), OpenAI Models Leaving Cursor After November 12 (Melvin Vivas on X · notes) and 11 more
• Blaxel · tool · x.com · check price
  Sandbox provider that works with the Agents API's BYOS option.
• Cloudflare · tool · x.com · check price
  Cloud platform listed as a supported BYOS sandbox provider.
  Also in: Using Codex as a Sysadmin to Find a Cloudflare DNS Issue (Melvin Vivas on X · notes)
• Daytona · tool · x.com · check price
  Sandbox infrastructure for running AI-generated code, now with GPU sandboxes.
  Also in: Daytona Offers GPU Sandboxes (H100, RTX 4090/5090) (Melvin Vivas on X · notes)
• E2B · tool · x.com · check price
  Cloud sandbox for running AI-generated code, supported via BYOS.
• Modal · tool · x.com · check price
  Serverless cloud platform for running and serving AI models and GPU workloads.
  Also in: Self-Hosting GLM 5.2 with Modal Auto Endpoints (Melvin Vivas on X · notes)
• Vercel · tool · x.com · free · recommended by both Bashiri Smith & Melvin Vivas
  Deploy web apps and frontends.
  Also in: OpenAI DevDay 2026 Recap: Dots, Agents API, Codex Cloud & Marketplace (Melvin Vivas on X · notes), 7 Habits to Become an AI Engineer: Books, Tooling, Research & Shipping (Bashiri Smith on Facebook · notes), Jev model added to the AIBackends API via Vercel AI Gateway (Melvin Vivas on X · notes), Open models now dominate token volume on Vercel AI Gateway (Melvin Vivas on X · notes) and 7 more
• OpenAI Codex · tool · openai.com · paid
  OpenAI's coding agent. In the diagram it writes code, fixes review findings and drives the build loop. The creator also used it to make this video.
  Also in: An agent bot that installs and drives Codex on its own (Melvin Vivas on X · notes), Asking a Coder bot to install Codex (Melvin Vivas on X · notes), Sign in with ChatGPT: Setting Usage Limits for Each App (Melvin Vivas on X · notes), Codex Cloud Environments Must Be Saved & Published Before Use (Melvin Vivas on X · notes) and 240 more
• Astra ultra · tool · openai.com · free
  The AI assistant or model ("Ultra" tier or mode) the creator prompted to build the interface. The post doesn't say exactly what it is.
  Also in: Codex Video Generation: One High-Res Image Per Scene, Not a Cropped Grid (Melvin Vivas on X · notes), Read the GPT-6 Astra launch article to learn what the model can do (Melvin Vivas on X · notes), Demo: AI Coding Agent Generates a "Software Factory" UI (Frontend Only) (Melvin Vivas on X · notes)

Try this

• Read OpenAI's Agents API announcement and compare the sandbox providers it supports.
• Build a 'Software Factory' app: generate the UI with Codex, then use the OpenAI Agents API with a sandbox provider (E2B, Daytona, Modal, etc.) as the backend.