feat(tui): make prompt size responsive and configurable

[bjschafer]

Issue for this PR

Related to #14670

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

• Makes the TUI prompt height configurable via tui.json (setting prompt.max_height) instead of being hard-capped at 6 lines.
• Lets the prompt textarea fill its parent width via tui.json (setting prompt.max_width) for users who want a wider/responsive prompt. This is opt-in via config.

To enable responsive width, add to tui.json:

{
    "prompt": {
        "max_width": "auto",
        "max_height": "auto"
    }
}

auto for prompt.max_width resolves to max(75, floor(terminal_width * 0.7)), or you can set a fixed numeric value.

How did you verify your code works?

• bun --cwd packages/opencode typecheck
• git diff --check
• pre-push hook: bun turbo typecheck

Screenshots / recordings

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

The only relevant result found is PR #28255 itself (the current PR), which is expected. The other result (#13885) is about a native status line template system and is not related to this prompt sizing feature.

No duplicate PRs found

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍

[rekram1-node]

I think this introduces a regression for the prompt input width, now it is much wider which is a change from our existing styling

[bjschafer]

I think this introduces a regression for the prompt input width, now it is much wider which is a change from our existing styling

The wider prompt is intentional, that's the core change this PR makes (along with allowing it to grow longer as well). The goal is for the prompt to grow within reasonable bounds with the terminal rather than staying capped at a fairly narrow width. The behavior is configurable as well.

Happy to clarify anything about the approach if it's helpful.

[rekram1-node]

[rekram1-node]

[rekram1-node]

That first option (what this PR does) looks pretty ugly to me, ill check w/ team.

I'm totally game for making the box configurable but i dont think we should be changing the default size to this

[rekram1-node]

Yeah talked w/ team we don't want to change the default behaviors here

[bjschafer]

would you be open to adding the adaptive width behind an option in tui.json instead?

and, any concerns with the expanded vertical space also in this PR?

[rekram1-node]

i think the vertical spacing one is prolly fine

[bjschafer]

Ok, left vertical spacing as-is in this change. Updated horizontal to not change the default behavior but instead provide an opt-in in tui.json like so:

{
  "prompt": {
    "max_width": "auto"
  }
}
// Resolves to max(75, floor(terminal_width * 0.7)).

or "auto" can instead be a fixed width.

[rekram1-node]

/review