OpenAI shipped ChatGPT Work, an agentic workspace, one day before confirming GPT-5.6 as the preferred model for Microsoft 365 Copilot.

ChatGPT Work executes long-running multi-step tasks across Slack, Gmail, Google Drive, CRMs, and internal knowledge bases, producing documents, spreadsheets, and sites instead of chat turns. Altman claims 54% better token efficiency on agentic coding. Then OpenAI confirmed GPT-5.6 powers M365 Copilot. Read those together: OpenAI is the model under Microsoft's agent surface at the exact moment it ships a competing agent product. If you build on Copilot extensibility, expect tool-calling and long-horizon behavior to shift under you with no opt-in.