diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..1a54072
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,4 @@
+doc/tags
+*.swp
+*.swo
+.DS_Store
diff --git a/README.md b/README.md
index cf92482..f7a87f0 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,43 @@
 # opencode.nvim
 
-Prototype Neovim plugin that opens `opencode` in a terminal split on the right.
+Neovim plugin that toggles an `opencode` terminal in a right-side split.
+
+The terminal buffer is kept alive when hidden, so your `opencode` session remains
+available across toggles.
+
+## Requirements
+
+- Neovim 0.10 or newer
+- The `opencode` CLI installed and available on `$PATH`
+
+This plugin does not install or bundle `opencode`; it only starts the CLI in a
+Neovim terminal. Use of `opencode` is subject to that project's own license and
+terms.
+
+## Installation
+
+Install with your plugin manager of choice.
+
+Using `lazy.nvim`:
+
+```lua
+{
+  "agj/opencode.nvim",
+  opts = {
+    width = 0.3,
+  },
+}
+```
+
+Using `vim-plug`:
+
+```vim
+Plug 'agj/opencode.nvim'
+```
+
+```lua
+require("opencode").setup()
+```
 
 ## Usage
 
@@ -10,18 +47,46 @@ Run:
 :OpenCodeToggle
 ```
 
-The command opens `opencode` in a right-side terminal window sized to 40% of the
-screen width. Running the command again closes only the window; the terminal
-buffer and `opencode` session stay alive. Run `:OpenCodeToggle` again to show the
-same session.
+The command opens `opencode` in a right-side terminal window sized to 30% of the
+screen width by default. Running the command again closes only the window; the
+terminal buffer and `opencode` session stay alive. Run `:OpenCodeToggle` again to
+show the same session.
 
 ## Configuration
 
 ```lua
 require("opencode").setup({
-  width = 0.4,
+  width = 0.3,
 })
 ```
 
 `width` is the fraction of the screen width used by the terminal window. The
-default is `0.4`.
+default is `0.3`. It must be greater than `0` and less than or equal to `1`.
+
+## Help
+
+After installing the plugin, run:
+
+```vim
+:help opencode.nvim
+```
+
+If your plugin manager does not generate helptags automatically, run:
+
+```vim
+:helptags ALL
+```
+
+## License
+
+opencode.nvim is free software released under the GNU General Public License,
+version 3 only. See [LICENSE](LICENSE) for the full license text.
+
+This program is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+PARTICULAR PURPOSE.
+
+## Trademark Notice
+
+opencode.nvim is an independent Neovim plugin and is not affiliated with,
+endorsed by, or sponsored by the maintainers of `opencode` or Neovim.
diff --git a/doc/opencode.nvim.txt b/doc/opencode.nvim.txt
new file mode 100644
index 0000000..6aeb5e7
--- /dev/null
+++ b/doc/opencode.nvim.txt
@@ -0,0 +1,93 @@
+*opencode.nvim.txt*        Toggle opencode in a Neovim terminal
+
+===============================================================================
+CONTENTS                                             *opencode.nvim-contents*
+
+1. Introduction                                      |opencode.nvim|
+2. Requirements                                      |opencode.nvim-requirements|
+3. Installation                                      |opencode.nvim-installation|
+4. Usage                                             |opencode.nvim-usage|
+5. Configuration                                     |opencode.nvim-configuration|
+6. License                                           |opencode.nvim-license|
+
+===============================================================================
+INTRODUCTION                                           *opencode.nvim*
+
+opencode.nvim toggles an `opencode` terminal in a right-side split.
+
+The terminal buffer is hidden instead of deleted when closed, so the same
+`opencode` session is shown the next time the window is toggled open.
+
+===============================================================================
+REQUIREMENTS                              *opencode.nvim-requirements*
+
+- Neovim 0.10 or newer
+- The `opencode` CLI installed and available on $PATH
+
+This plugin does not install or bundle `opencode`; it only starts the CLI in a
+Neovim terminal. Use of `opencode` is subject to that project's own license and
+terms.
+
+===============================================================================
+INSTALLATION                              *opencode.nvim-installation*
+
+Install with your plugin manager of choice.
+
+Using lazy.nvim: >lua
+  {
+    "agj/opencode.nvim",
+    opts = {
+      width = 0.3,
+    },
+  }
+<
+
+Using vim-plug: >vim
+  Plug 'agj/opencode.nvim'
+<
+
+Then call setup from your Neovim configuration: >lua
+  require("opencode").setup()
+<
+
+===============================================================================
+USAGE                                          *opencode.nvim-usage*
+
+                                                *:OpenCodeToggle*
+:OpenCodeToggle
+        Toggle the right-side opencode terminal window.
+
+        If the terminal window is visible, this closes only the window. The
+        terminal buffer and running `opencode` process remain alive. If the
+        terminal buffer already exists, the command reuses it.
+
+===============================================================================
+CONFIGURATION                          *opencode.nvim-configuration*
+
+Call setup with an optional table: >lua
+  require("opencode").setup({
+    width = 0.3,
+  })
+<
+
+Options:                                             *opencode.nvim-options*
+
+                                                        *opencode.nvim-width*
+width                                                   number, default: 0.3
+        Fraction of the screen width used by the terminal split. Must be
+        greater than 0 and less than or equal to 1.
+
+===============================================================================
+LICENSE                                      *opencode.nvim-license*
+
+opencode.nvim is free software released under the GNU General Public License,
+version 3 only. See the LICENSE file for the full license text.
+
+This program is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+PARTICULAR PURPOSE.
+
+opencode.nvim is an independent Neovim plugin and is not affiliated with,
+endorsed by, or sponsored by the maintainers of `opencode` or Neovim.
+
+vim:tw=78:ts=8:noet:ft=help:norl: