Singleton reasoning title is missing from live TUI history

Singleton reasoning title is missing from live TUI history

What version of Codex CLI is running?

• codex-cli 0.145.4

What subscription do you have?

• Pro

Which model were you using?

• GPT-5.6 family; observed with gpt-5.6-terra

What issue are you seeing?

• A reasoning item whose summary contains one title-only part appears in the Working row but not in completed live history:

**Confirming backend JSONL source**

• Cold resume shows the title, so the persisted item is intact.
• Items with multiple summary parts can appear to work because the TUI joins the parts and treats later titles as body content.

What steps can reproduce the bug?

• Run a turn with a model that emits a reasoning item containing one bold title and no prose body.
• Observe the title in the Working row.
• After item completion, confirm that live history omits the title.
• Resume the thread and confirm that the title appears.

What is the expected behavior?

• A nonempty title-only summary should be committed once to live history.
• Completing it should release the same title from the Working row.

Additional information

• For a singleton **Title**, split_reasoning_summary_parts() returns an empty header and the title as content.
• new_reasoning_summary_block() consequently marks the cell transcript-only: display_lines() is empty while transcript_lines() retains the title.
• The behavior appears to be an older heading-plus-prose assumption exposed by newer title-only summary output.
• Codex CLI assisted with organizing this report and the focused source analysis.