[FEATURE] Make TUI cursor style configurable (thin/line cursor instead of forced block) #32209

Summary

opencode's TUI forces the terminal cursor to a block shape, overriding the user's terminal-emulator cursor preference. It would be great to make the cursor style configurable (e.g. a thin/line cursor) like the cursor color already is.

Current behavior

• The terminal is configured with a thin (bar/beam) cursor.
• On launching opencode, the cursor switches to a block while the prompt is focused.
• On exit, opencode restores the cursor shape (ESC [ 0 q) and color (ESC ] 112 BEL), so the behavior is clearly driven by opencode, not the terminal.

There is no opencode.json field to change this (confirmed against https://opencode.ai/config.json).

Root cause

opencode uses OpenTUI (@opencode-ai/tui → @opentui/core). The EditBufferRenderable (the prompt input) defaults its cursor style to block:

packages/core/src/renderables/EditBufferRenderable.ts

cursorStyle: {
  style: "block",
  blinking: true,
},

OpenTUI already supports all four shapes (packages/core/src/types.ts):

export type CursorStyle = "block" | "line" | "underline" | "default"

…and exposes a writable cursorStyle on the edit buffer, which it translates into DECSCUSR escape sequences.

However, opencode's prompt component only sets cursorColor, never cursorStyle:

packages/tui/src/component/prompt/index.tsx

if (props.disabled) input.cursorColor = theme.backgroundElement
if (!props.disabled) input.cursorColor = theme.text
// cursorStyle is never set -> falls back to OpenTUI's "block" default

Proposal

Expose the cursor style via config (e.g. opencode.json or the theme), so users can pick e.g. a thin/line cursor. Minimal change would be passing cursorStyle through to the input alongside cursorColor, e.g. input.cursorStyle = { style: "line", blinking: true }.

A possible config shape:

{
  "tui": {
    "cursorStyle": "line"   // "block" | "line" | "underline" | "default"
  }
}

Environment

• opencode 1.17.4 (Homebrew, macOS arm64)
• TUI via OpenTUI @opentui/core 0.3.4