What does Codex’s “Error running remote compact task: {"detail":"Bad Request"}” mean?

Thu, 17 Sep 2026 11:53:02 +0900

When you have been working on Codex for a long time, remote compact may be triggered. At that point, the following error can appear:

Error running remote compact task: {"detail":"Bad Request"}

This indicates that Codex’s context‑compression process did not complete successfully.

However, {"detail":"Bad Request"} is not a specific cause name. From just this display alone, you cannot tell whether the context was too large, there were too many images, the history entries were invalid, or it was a temporary server‑side issue.

We recovered from a remote compact failure in a long-running Codex session that contained a large number of uncompressed PNGs.

Fri, 11 Sep 2026 21:25:17 +0900

The thread that had been running for a long time on Codex suddenly stopped working.

The error that was displayed is as follows.

If you only want to understand the meaning of this error, it is explained in “What does Codex’s ‘Error running remote compact task: {“detail”:“Bad Request”}’ mean?” (source). In this article, I will describe the steps we took to investigate the history and restore the thread.

Error running remote compact task: {"detail":"Bad Request"}

If it had failed only once, a simple retry would have worked, but in this thread every time we tried a compact we received the same HTTP 400 error, and eventually even the normal responses began to fail.

Compaction

What does Codex’s “Error running remote compact task: {"detail":"Bad Request"}” mean?

We recovered from a remote compact failure in a long-running Codex session that contained a large number of uncompressed PNGs.