OpenAI DevDay 2026 for Agent Builders: Agents API Computer Use, GPT-6.1 Sol, MCP Events

OpenAI DevDay 2026, held on September 29 in San Francisco, had more than 20 announcements. Five matter most to agent builders: the Agents API now supports computer use, plus multi-agent features from Codex, tool search and context compaction, with OpenAI running the execution infrastructure; GPT-6.1 Sol approaches GPT-6 Astra on several evaluations at one-fifth of Astra's token prices; the Decisions API (limited preview) uses the small Luna model to pick from predefined answers for routing and classification; ChatGPT plugins can now react to events through the proposed MCP Events specification; and Dots, always-on agents inside ChatGPT. Facts were re-checked against the cited sources on October 11, 2026; OpenAI's own recap page could not be retrieved, so some details come from press coverage.

The Agents API now lets your application operate software through its graphical interface, which matters when a system has no API. It also gains multi-agent capabilities taken from Codex, tool search (useful when an agent has more tools than fit comfortably in context), and context compaction for long-running tasks. OpenAI manages the execution infrastructure.

GPT-6.1 Sol targets coding, computer use and professional tasks. OpenAI says it approaches GPT-6 Astra on several evaluations at one-fifth of Astra's standard input and output token prices, with cached input at $0.10 per million tokens. Check OpenAI's documentation for where it is available.

What to do: run your own evals with Sol as the default model and route only the hard cases to Astra. A model router plus caching is the fastest cost win for agent workloads; see how to reduce LLM costs.

In limited preview, the Decisions API uses the smaller Luna model to choose from a predefined set of answers given text or image context. It is aimed at classification, request routing and agent decision points.

Where it fits in an agent: the many small branch decisions ("is this email a support request, a sales lead or spam?") that do not need a frontier model. Constraining the output to a fixed set also makes those steps easy to evaluate.

Plugins can now provide sidebar experiences, interactive conversation panels and custom file viewers, and can respond to events through the proposed MCP Events specification. Event-driven tools are what always-on agents need: instead of polling, an agent is woken when something changes. If you already expose systems as MCP servers, watch this spec closely. Background: What is MCP?

Dots are always-on agents inside ChatGPT on GPT-6 Astra, with their own cloud computer and access to 4,000+ apps. They are a product for ChatGPT users rather than a developer API, and the announcement did not detail developer access. Full guide: What are OpenAI Dots?

Codex now runs in cloud environments alongside local execution, so you can start remote tasks from another device. The CLI gained voice input and an /agents interface for delegating and monitoring tasks.

• Re-run your agent evals with GPT-6.1 Sol; keep Astra only where Sol measurably falls short
• Replace custom browser automation with Agents API computer use where reliability improves
• Move high-volume classification steps to a constrained-choice model and evaluate them separately
• Turn on context compaction for long-running tasks and verify it keeps the facts your agent needs
• Prototype one event-driven MCP tool so your agent wakes on change instead of polling
• Confirm your approval gate and audit log cover the new computer-use actions

What did OpenAI announce at DevDay 2026? More than 20 announcements, including Dots (always-on ChatGPT agents), computer use and multi-agent features in the Agents API, GPT-6.1 Sol, the Decisions API, an expanded ChatGPT plugin platform with MCP Events, and Codex cloud environments.

What is GPT-6.1 Sol? An OpenAI model for coding, computer use and professional tasks that OpenAI says approaches GPT-6 Astra on several evaluations at one-fifth of Astra's token prices.

Does the OpenAI Agents API support computer use? Yes. Since DevDay 2026, the Agents API supports computer use, letting applications operate software through its graphical interface.

What is MCP Events? A proposed extension that lets tools built on the Model Context Protocol notify clients when something happens, so ChatGPT plugins and agents can respond to events instead of polling.

What is the OpenAI Decisions API? A limited-preview API that uses the small Luna model to choose from a predefined set of answers based on text or image context, for classification, routing and agent decisions.

Should I switch to GPT-6.1 Sol to save money? OpenAI says Sol approaches GPT-6 Astra on several evaluations at one-fifth of the token price, but that is a vendor claim on its evaluations. Run your own evals with Sol as the default and keep Astra only where Sol measurably falls short.

Can developers build their own Dots? The announcement did not detail developer access to Dots. Builders who want similar capabilities in their own product should look at the Agents API with computer use.

What does computer use mean for agents without APIs? It lets your application operate software through its graphical interface, which matters when a system has no API. Keep your approval gate and audit log covering these actions.

• What are OpenAI Dots?
• What is MCP?
• How to reduce LLM costs by 90%
• Build your own 24/7 personal AI agent
• Agentic AI Engineer roadmap

• OpenAI DevDay 2026 (InfoQ)
• DevDay 2026 recap (OpenAI)
• OpenAI launches dots (The Next Web)