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What the error means
A common full message is thread/resume failed during TUI bootstrap: thread/resume failed: thread <thread-id> already has an active writer (code -32600). Codex is reporting that the requested thread already has a writer when it tries to resume it. The current TUI source recognizes this error text in an active-writer error check, but that recognition does not provide a repair command or establish why the owner exists: Codex TUI session source.
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The message alone cannot distinguish an active CLI, a remote terminal that survived a disconnect, an editor or app-server-connected client, and stale ownership after a process interruption. The recovery depends on which situation applies.
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Check whether another client still owns the thread
Another CLI, editor, or app-server client
Check whether the same thread is open in another Codex CLI session, VS Code panel, or client connected through the app server. A client that is still using the thread may be the legitimate writer. Close or finish work in that client normally, then retry the resume. Do not remove a lock while a client may still be operating on the thread.
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A remote TUI after an SSH disconnect
Losing an SSH connection does not necessarily stop the Codex process on the remote host. In an issue report opened September 9, 2026, a user running Codex CLI 0.153.4 on Linux said an idle remote TUI remained alive after SSH loss and continued to hold the writer. The report says the process could remain for hours without server-side SSH keepalive detection; those details describe that reporter’s setup, not a general timing guarantee. See the remote TUI report.
If you can reconnect to the host, check whether the original Codex session is still running and return to it if it is. Only stop that process if you have confirmed it is no longer doing work and you are willing to end that session.
A VS Code panel holding a live lock
A September 14, 2026 issue report describes a VS Code panel holding an OS-level lock while a CLI resume failed. The reporter used lsof and flock to investigate that specific setup. These are reporter diagnostics, not universal commands for all operating systems or proof that a lock can safely be removed. See the VS Code lock report.
If the previous process exited after an interrupt
A user report opened September 7, 2026 describes Ctrl+C followed by a failed resume, even though the reporter said the prior CLI process had exited. This is evidence that stale-looking ownership has been reported; it does not establish the mechanism or show that stale ownership is the cause in every case. See the Ctrl+C resume report.
If you have confirmed that no Codex client or process is still using the thread, retry the resume. The reviewed reports do not establish a safe, supported lock-file deletion procedure. Avoid deleting lock data blindly: if the owner is actually alive, doing so could interfere with ongoing work.
Check the approval-flag workaround only for the matching trigger
If the failure began after interrupting an approval and your restart command adds --approve-for-me, one report says the user could resume after restarting without that option, while restarting with it failed. The report was opened August 25, 2026, and closed as a duplicate; it is a case-specific workaround, not a general fix for active-writer errors. See the interrupted-approval report.
For that specific sequence, try resuming without --approve-for-me. If the error persists, record the exact command and interruption sequence rather than treating the flag as a universal cause.
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- Codex CLI version and operating system.
- Whether the thread is open in another CLI, VS Code panel, or app-server-connected client.
- Whether the session was local or remote, and the exact disconnect or interruption sequence.
- The complete error text, including the thread/resume context and error code.
- Whether the restart command used
--approve-for-me, if approval interruption was involved.
The GitHub reports linked above are user reports rather than controlled reproductions or official remediation guidance. They show several plausible ownership situations, but do not establish a single recovery procedure that is safe for every cause.
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