TUI flashes continuously during bursts of Code Mode tool activity

Reproduce the issue in Codex CLI inside tmux using concurrent nested shell or read-only tool calls, and compare the live TUI with the Ctrl+T transcript view. Trace the TUI rendering path responsible for Ran and Explored entries and changing lower-panel height; done means concurrent activity stays visually stable without terminal flashing while full details remain available through Ctrl+T.

What version of Codex CLI is running?

• rust-v0.146.0-alpha.10

What subscription do you have?

• ChatGPT Pro 20x.

Which model were you using?

• gpt-5.6-sol

What terminal emulator and version are you using?

• Alacritty with Codex running inside tmux.

What issue are you seeing?

• I locally adjusted the code-mode-exec instructions to guide the model to write JavaScript that invokes independent nested tools concurrently.
• The generated Code Mode call and its nested tool calls successfully complete the requested task.
• During a burst of concurrent Code Mode tool activity, the TUI rapidly inserts many Ran and Explored entries while the lower portion of the interface repeatedly changes between one and multiple lines.
• The repeated layout changes cause the entire terminal to flash at high frequency and can flood the tmux scrollback buffer.
• The problem is therefore the unstable and continuously flashing TUI presentation during otherwise successful concurrent tool execution.

What steps can reproduce the bug?

• Start Codex CLI in a tmux session.
• Configure the local code-mode-exec instructions to guide the model to generate JavaScript that invokes independent nested tools concurrently.
• Ask Codex to perform a task that results in many concurrent shell or read-only nested tool calls.
• Keep the TUI visible while the nested tool calls start and complete in quick succession.
• Confirm that the task completes, while the transcript receives many Ran or Explored entries and the lower interface repeatedly changes height, causing continuous terminal flashing.

What is the expected behavior?

• Supported concurrent Code Mode tool activity should render without rapid whole-terminal flashing or repeated one-line-to-multiline layout oscillation.
• Concurrent nested tool activity should be collapsed in the TUI like other collapsed tool output, with the existing Ctrl+T transcript view available to inspect the complete details.

Additional information

• Codex CLI assisted with organizing this report.