Codex Desktop 26.616: automatic context compaction fails at 258k/258k and aborts with context-window error

What version of the Codex App are you using (From “About Codex” dialog)?

Codex Desktop 26.616.51431
Released Jun 21, 2026

What subscription do you have?

ChatGPT Pro / Full access

What platform is your computer?

macOS, Apple Silicon / arm64

What issue are you seeing?

Hi Codex team,

A long-running Codex Desktop task just became unrecoverable even though the app had already entered automatic context compaction.

The UI showed:

• Automatically compacting context
• Context window: 100% full
• 258k / 258k tokens used
• Model/mode: 5.5 Extra High
• The task had been working for about 1m 10s

After that, Codex surfaced the error:

Codex ran out of room in the model's context window. Start a new thread or clear earlier history before retrying.

This looks like a context-compaction/recovery bug. If Codex detects the context is full and automatically starts compaction, that compaction path should still be able to complete. The user should not be forced to abandon the existing task/thread because the compaction operation itself cannot run inside the already-full context window.

What steps can reproduce the bug?

I do not have a minimal deterministic reproduction yet, but the observed flow was:

1. Use Codex Desktop in a long-running thread/task.
2. Continue until the UI reaches 258k / 258k tokens used and shows 100% full.
3. Codex enters Automatically compacting context.
4. Instead of recovering/compacting, the thread fails with:

``text
Codex ran out of room in the model's context window. Start a new thread or clear earlier history before retrying.
``

What is the expected behavior?

When automatic compaction is triggered, Codex should provide a safe recovery path:

• compact before the active request reaches an unrecoverable state;
• or run compaction out-of-band against stored history rather than requiring the full thread to fit in the active model context;
• or preserve the thread/task state and allow retry after compaction.

The app should not ask the user to start a new thread after it has already detected the full context and attempted automatic compaction.

Additional information

Feedback uploaded successfully:

019ee8f8-10a3-7110-842f-ade6115b13d1

Screenshots captured the feedback ID, the Automatically compacting context state, 258k / 258k tokens used, and the Codex version dialog.

Related/open issues may include context compaction failures such as #29302, #28920, and #29142, but this report is specifically for Codex Desktop automatic compaction reaching 258k / 258k and then failing instead of recovering the active task.