Slash-command `argument-hint` rendering overwrites typed characters with blanks

Summary

When a slash command has an argument-hint defined, typing the full command name and a space causes the display to overwrite the trailing typed characters with blanks. The input buffer itself is unaffected — only the rendering. This is distinct from any feature-request about configurable cursor style.

Repro

1. Define a slash command at ~/.claude/commands/doc.md with frontmatter:

``yaml
argument-hint: <project> [--infra] [--v1] [--examples] [--repo <name>] | <PR#> [overrides] | --archive <project> | (no args, asks)
``

1. In Claude Code's interactive prompt, type these 5 keystrokes: /, d, o, c, (slash, d, o, c, space).
2. Stop and observe the display.

Expected

Display: /doc [cursor]<ghost-text-hint> — the typed /doc fully visible, hint begins after the cursor.

Actual

Display: /do [cursor]<ghost-text-hint> — the typed c AND the typed space are both rendered as blanks; the block cursor sits one column to the right of where the c should be visible. The hint text begins after the cursor.

The buffer is fine (submitting the command works correctly) — this is purely a rendering bug.

Diagnosis

The argument-hint rendering layer appears to:

1. Overwrite the position of c (the last char of the command name) with a blank,
2. Overwrite the typed space with a second blank,
3. Position the block cursor on that second blank,
4. Render the hint text after the cursor.

The hint's rendering origin is computed too far to the left, eating typed characters that should remain visible.

Environment

• macOS 15.x, zsh, VS Code integrated terminal
• Claude Code CLI (Opus 4.7, 1M context build, current as of 2026-05-16)

Related

Distinct from the open feature-requests for configurable cursor style (#29133, #16086, #10215, #674) — those ask for user choice of cursor style; this is a rendering bug in the default path. Even users who prefer a block cursor would benefit from typed characters remaining visible.

Screenshot

<img width="553" height="86" alt="Image" src="https://github.com/user-attachments/assets/eed784fb-4fa2-4c78-90ce-403752222724" />