agent-signals

020. The screen shape of Codex CLI

View as Markdown Open in Claude Open in ChatGPT
Date
2026-10-24
Agents
Codex CLI
Measured on
not recorded

Measured

2026-10-24, Codex CLI 0.163.0, codex --no-daemon in a private tmux server, 120 columns by 40 lines. The TUI uses the alternate screen, so the pane has no scrollback.

What was measured

Codex draws no frame around its input box. Seven details matter to a reader.

  1. The mark is › (U+203A), not ❯ or >. A message of the history also starts with › . The live box is the last line that starts with the mark.
  2. No rule of ─ is above or below the box. The frame test of fact 1 cannot prove an idle box.
  3. Under an empty box, the last line starts with ? for shortcuts. The line above it gives the model and the folder. The footer line is absent while the box holds text, and absent under a dialog.
  4. A busy turn draws • Working (1s • esc to interrupt) directly above the box. The box, its placeholder and the footer stay drawn. A background command adds · 1 background terminal running · /ps to view · /stop to close to the same line.
  5. The empty box shows a placeholder, for example › Ask Codex to do anything. In a plain capture it looks like typed text. With -e, the placeholder is dim and typed text is not.
  6. The approval dialog draws in place of the box: "Would you like to run the following command?", Environment: local, Reason: ..., $ <command>, then numbered options under the mark, and the footer "Press enter to confirm or esc to cancel". The selected option is reverse video.
  7. The folder-trust dialog comes before the first box in a folder that Codex has not seen: "Trust this folder? ...", › 1. Trust and continue, 2. Quit, and the footer "enter continue · esc quit". The hooks review dialog ("Hooks need review") can come first in a project with untrusted hooks.

An update banner in a box of ╭─╮ draws at the top of each start. It is not the input box.

Mechanism

A reader for Codex proves an idle box with all of these: the last mark line is not a numbered option, no line of the screen holds "esc to interrupt", and the last nonblank line starts with ? for shortcuts. It tests the busy line before the idle footer, because the footer stays drawn during a turn. It gives UNKNOWN for each other screen, for example a box with typed text. This proof is weaker than a frame: a later dialog can draw the same footer.

Incident

None recorded.

Screens

codex/idle, codex/typed, codex/busy, codex/busy-background, codex/after-turn, codex/approval, codex/approval-full, codex/after-cancel, codex/trust, codex/hooks-review.

Not measured

The keys of the approval dialog other than Esc. The file-change approval dialog. A narrow pane where the busy line wraps. Styled captures of each screen. Other Codex versions, and a TUI that runs through the shared app-server daemon.

Source

Measured by the tg-bridge project and published in its report "Codex CLI and Cursor CLI as harnesses: measurements, 2026-10-24", with one more capture by the ai-world project. The text is a summary, and it holds no host details and no session details.

Screens in the corpus that name this fact