codex/agentydragon/tasks/15-embedded-neovim-prompt-editor.md

Task 15: Embedded Neovim Prompt Editor

This task is specific to codex-rs.

Status

General Status: Not started
Summary: Not started; missing Implementation details (How it was implemented and How it works).

Goal

Replace the basic line‑editing prompt composer with an embedded Neovim window so users can enjoy full-featured, multi-line editing of their chat prompt directly inside the TUI.

Acceptance Criteria

• Introduce a TUI-integrated Neovim editor pane activated via /edit-prompt or Ctrl+E when embedded_prompt_editor = true in [tui] config.
• Pre-populate the Neovim buffer with the current draft prompt; upon exit, reload the buffer contents back into the composer.
• Support standard Neovim keybindings and commands (e.g. insert mode, visual mode, plugins) within the embedded pane.
• Cleanly restore the previous TUI layout after closing the editor, with prompt focus returned to the composer.
• Provide configuration toggle (embedded_prompt_editor) and fall back to external-editor prompt behavior when disabled.

Implementation

How it was implemented

• Add a new module tui/src/editor/neovim.rs that wraps a headless Neovim RPC instance and renders its UI into a dedicated TUI layer.
• Extend tui/src/bottom_pane/chat_composer.rs to detect embedded_prompt_editor and invoke the embedded editor instead of spawning an external process.
• Wire a config flag embedded_prompt_editor: bool through ConfigToml → Config under the tui section, defaulting to false.
• Handle Neovim communication via nvim-rs crate, multiplexing input/output over the TUI event loop.

How it works

• When the user triggers the editor, pause the main TUI rendering and allocate a full-screen or split view for Neovim.
• Start Neovim in embedded RPC mode, passing the current prompt text into a new buffer.
• Drive Neovim’s UI updates via RPC and render its screen cells into the TUI terminal using termion or similar backend.
• Detect the Neovim exit event (e.g. user :q or ZZ), fetch the buffer contents, and close the embedded view.
• Restore the original TUI state and update the composer widget with the edited prompt.

Notes

• This relies on a working nvim binary in PATH or specified via nvim_binary config.
• Investigate performance impact of embedding a full editor in the TUI; ensure fallback to external-editor remains smooth.
• Consider edge cases (resizing, plugin‑heavy Neovim configs) and document prerequisites in the README.