Codex Desktop auto-compaction sends unsupported `context_compaction` item type

What version of Codex CLI is running?

codex-cli 0.137.0

What subscription do you have?

ChatGPT Pro

Which model were you using?

gpt-5.5

What platform is your computer?

Linux 6.8.0-124-generic x86_64 x86_64

What terminal emulator and version are you using (if applicable)?

_No response_

Codex doctor report

Codex Desktop. No tmux/screen/zellij multiplexer in use.

codex doctor reports TERM=dumb in the internal execution environment:
TERM=dumb
stdin/stdout/stderr are not terminal

What issue are you seeing?

When working in Codex Desktop, automatic context compaction can break the current thread with an API validation error.

The error says that an input item has type context_compaction, but the API schema only accepts compaction and compaction_trigger among compaction-related item types.

Full error:

[ItemParam] [input[733]] [invalid_enum_value] Invalid value: 'context_compaction'. Supported values are: 'additional_tools', 'apply_patch_call', 'apply_patch_call_output', 'code_interpreter_call', 'compaction', 'compaction_trigger', 'computer_call', 'computer_call_output', 'custom_tool_call', 'custom_tool_call_output', 'file_search_call', 'function_call', 'function_call_output', 'image_generation_call', 'item_reference', 'local_shell_call', 'local_shell_call_output', 'mcp_approval_request', 'mcp_approval_response', 'mcp_call', 'mcp_list_tools', 'message', 'reasoning', 'shell_call', 'shell_call_output', 'tool_search_call', 'tool_search_output', and 'web_search_call'.

### What steps can reproduce the bug?


**What steps can reproduce the bug?**

```markdown
1. Open a long-running thread in Codex Desktop.
2. Continue working until automatic context compaction is triggered.
3. After compaction, continue sending messages in the same thread.
4. The thread fails with the `invalid_enum_value` error for `context_compaction`.

### What is the expected behavior?

Codex should serialize compaction-related items using a supported item type such as `compaction` or `compaction_trigger`, or handle compaction metadata internally without sending unsupported item types to the API.

The thread should remain usable after automatic context compaction.

### Additional information

_No response_