Everyone who has tried to build a real agent knows the problem, and it isn't intelligence. Getting a model to plan a task is easy. Keeping it alive three hours into an unsupervised job is where homemade setups die. The context window fills up. A tool call fails and nothing recovers. It loses track of what it was doing halfway through. You end up writing more plumbing than product. Last Wednesday OpenAI opened the Agents API in public beta. It's the same harness that runs Codex and ChatGPT for Work, and it handles exactly that layer. Session orchestration. Context compaction when the window fills. Subagent coordination. Crash recovery. Durable sessions that pick up where they left off. Agents that stay running for days. There's no fee for the API itself. You pay for tokens, tools, and sandbox compute, which you were paying for anyway. The numbers from launch customers are worth a look. 📊 One company moved their case review workflow onto it and cut cost per case by 60%. Another decoupled their agent from the sandbox environment and dropped failed responses by 86%. A third reported their evaluation score climbing from 0.71 to 0.85, and specifically credited being able to see and orchestrate subagents instead of guessing at what they were doing. Different companies, different workloads, all vendor-reported. But the pattern is consistent and it's not about the model getting smarter. It's the scaffolding underneath getting solid. You can also run the sandbox wherever you want. OpenAI-hosted, your own infrastructure, or partners like Cloudflare and Vercel. And it speaks MCP, so tools you've already wired up plug in. Here's the part worth thinking about even if you never touch an API. 💡 The build-versus-buy line just moved, and it moved against a lot of people's business models. If you've been paying a developer to build orchestration, retry logic, session memory, and error recovery for your agents, a big chunk of that work is now free infrastructure maintained by someone else. That's not a small line item. For most agent projects it's the majority of the engineering.