AI Error WikiSearch

Codex could not start its user interface

The Codex editor panel fails to load.

Quick answer

This wording appears in reports about the Codex VS Code extension failing before its panel becomes usable. One Windows reporter said reloading the window and restarting VS Code did not help. A Linux reporter restored the panel by returning from extension 26.1021.22027 to 26.1007.21434. That version-specific result is useful evidence, not a universal downgrade instruction.

Exact message

Codex could not start — The extension could not start its user interface.

What it means

The panel failed at startup, before a normal Codex task began. Check the extension version rather than treating this as a prompt or model problem. The Linux issue says reinstalling the CLI and extension did not fix that machine; the older extension did. A different version may fail for another reason.

What to try

  1. Write down your OS, VS Code version, and Codex extension version. Save a screenshot of the exact startup message.
  2. Reload the VS Code window or restart it once. If the panel still will not open, stop repeating the same reload and compare your version with the linked reports.
  3. If your installed extension matches a reported failing build, check for a newer fixed build or consider a known working older build after backing up local settings. Record the result so you can reverse the change if it does not help.

User report

The Windows issue names extension 26.51021.22027 and says reload and restart failed. The Linux issue names 26.1021.22027; its reporter tried a clean reinstall and still saw the error, then reported success with 26.1007.21434. Later Linux commenters in the same thread reported the same rollback result. The two issue numbers do not prove all builds or operating systems behave alike.

FAQ

Which product shows this message?

The cited screenshots and reports concern the Codex panel in VS Code. The panel may say it could not start its user interface before you can sign in or send a prompt. If the desktop Codex app opens but a task later disconnects, use the stream disconnect guide instead; the failure occurs at a different point.

Will restarting VS Code fix it?

It is a reasonable first check because it is quick and reversible. It did not fix the Windows reporter’s case, and the Linux reporter still saw the error after a clean reinstall. Try it once, then record the extension version if the same panel returns. Repeated restarts without a version check are unlikely to narrow the problem.

Should I downgrade the extension?

Only consider it after you identify the extension version and compare it with the linked reports. A Linux reporter said 26.1007.21434 restored the panel after 26.1021.22027 failed, and other commenters confirmed that particular comparison. Back up settings and note your current version before changing it. A newer version or a different OS may need another solution.

Sources