Cursor Projects: the main agent of every existing project shows "Agent encountered an error" after an update; reconnecting GitHub and picking a default repository fixed it

发生场景

Source(s): https://forum.cursor.com/t/cursor-projects-agent-encountered-error-after-latest-update/174068 Signal: 59 views; the original poster's own fix reply is the accepted answer, posted 12 minutes after the report (October 2026). Status: reported working by source, not reproduced by us.

问题

After the 2026-10-08 Cursor update, sending a message to the main agent of any project created before the update shows an "Agent encountered an error" popup, and retrying or sending a new request shows it again. Creating a new agent inside the project avoids the popup, but its chat disappears after sending a message. Reproduced on macOS and on the web.

报错原文（已脱敏/规范化）

Agent encountered an error

适用环境

Cursor 3.23.23 (Universal) on macOS, Agent Window layout, and Cursor on the web; projects started in the macOS IDE before the update.

如何确认是这个问题

1. Open a project created before the update and send a message to its main agent. → expect: the "Agent encountered an error" popup every time.
2. Create a new agent in the same project and send a message. → expect: no popup, but the chat disappears.

不是这个问题时 / 边界

The popup also appears in projects that never used a GitHub-backed environment, or GitHub is connected and a default repository is already set (our inference).

根因

Not explained by Cursor. The fix suggests the project's environment lost its GitHub connection or default repository during the update (our inference).

修复步骤

1. Reconnect your GitHub account in Cursor's settings (the original poster; they did not give the exact menu path).
2. Select a default repository for the environment in Cursor's settings (the original poster). → expect: the main agents of the existing projects work again.

如何验证

Sending a message to an existing project's main agent gets a normal reply with no popup.

试过没用的办法

Retrying the request and sending a new message did not help (the original poster).

风险提示

When you reconnect GitHub, grant access only to the repositories the agents need (our inference).

验证范围

Cursor 3.23.23 Projects on macOS and the web, October 2026.

何时失效

Cursor shows a specific "GitHub not connected / no default repository" message instead of the generic error.