Background Web Agents Failing with “Something Went Wrong”

[OCA99]

Where does the bug appear (feature/product)?

Background Agent (GitHub, Slack, Web, Linear)

Describe the Bug

After 30 minutes running on a task, the frontend shows: “Something went wrong
An error occurred while loading the agents page. Please try again.”

Reloading the page shows the same error. The Chrome console shows:
[AgentsError] Error: cannot encode field aiserver.v1.ConversationMessage.ToolResult.tool_call to JSON: E(…).toJson is not a function

Steps to Reproduce

For now this has only happened on a specific task we have. The task runs correctly for ~30 minutes and then this happens. We’ve tried with the same task two times and have had the same result.

Expected Behavior

The Agent keeps running as normal.

Screenshots / Screen Recordings

Operating System

MacOS

Version Information

Web agents

For AI issues: which model did you use?

Codex 5.3 High

Does this stop you from using Cursor

Sometimes - I can sometimes use Cursor

[deanrie]

Hey, this is a known issue. It’s the same bug with ToolResult.toJson serialization that’s affecting several users right now. More details are in this thread.

The team is aware. What’s interesting is that you’re seeing this on Codex 5.3 High. Other users mostly reported it on GPT 5.4, and Codex 5.3 seemed to work for them. That’s helpful info.

A couple workarounds that might help:

• Try opening the agent page in Safari (on macOS). Some users said the error doesn’t show up there.
• Try a different model, like GPT 5.4 or Composer 1.5, although based on other reports they might be affected too.

Let me know if any of this helps.