Session name on the prompt bar lost its highlighted background (renders as plain text)

Summary

The session name shown on the prompt bar (set via /rename) has lost its highlighted background. It used to render as a filled badge — accent-colored background with dark text — sitting on the prompt box border. It now renders as plain accent-colored text with the border line simply broken around it.

Before / after

Before: the name appeared as a solid filled block, e.g. a cyan rectangle containing dark text my-session, interrupting the prompt border.

After: the same element renders as unfilled text, e.g. ───── hiya ─, in the accent color with no background fill.

(Screenshots available — happy to attach them to this issue.)

Environment

• Claude Code 2.1.245 (the running process at the time of the report; 2.1.246 was installed but not yet picked up by any live session)
• macOS, Darwin 24.6.0
• iTerm2, zsh
• tui: "fullscreen"
• Custom theme in ~/.claude/settings.json: "theme": "custom:forest" (a base: dark theme overriding accent tokens including promptBorder / promptBorderShimmer)

Steps to reproduce

1. Run /rename some-name in an interactive session.
2. Look at the session name on the prompt bar.

Expected: the name renders as a filled/highlighted badge.
Actual: the name renders as plain text with no background fill.

What was ruled out

• Not a version hot-swap mid-session. Every running claude process was verified via lsof to be mapped to the same 2.1.245 binary; the 2.1.246 install had not been picked up by any live session.
• Not the terminal color scheme. Switching the iTerm2 color preset (via the OSC 1337 SetColors escape) did not restore the fill.

Open question

Is the fill supposed to come from a theme token that a custom: theme can leave unset? If the badge background is driven by a token that custom themes are not required to define, that would be worth documenting — or worth falling back to the base theme value rather than rendering unfilled.