diff --git a/README.md b/README.md
index 6066917..d9231d6 100644
--- a/README.md
+++ b/README.md
@@ -4,7 +4,7 @@
 
 # Plannotator
 
-Interactive Plan Review for AI Coding Agents. Mark up and refine your plans using a visual UI, share for team collaboration, and seamlessly integrate with **Claude Code**, **OpenCode**, and **Pi**.
+Interactive Plan Review for AI Coding Agents. Mark up and refine your plans using a visual UI, share for team collaboration, and seamlessly integrate with **Claude Code**, **OpenCode**, **Pi**, and **Codex**.
 
 <table>
 <tr>
@@ -55,6 +55,7 @@ Plannotator lets you privately share plans, annotations, and feedback with colle
 - [Claude Code](#install-for-claude-code)
 - [OpenCode](#install-for-opencode)
 - [Pi](#install-for-pi)
+- [Codex](#install-for-codex)
 
 ## Install for Claude Code
 
@@ -122,6 +123,35 @@ See [apps/pi-extension/README.md](apps/pi-extension/README.md) for full usage de
 
 ---
 
+## Install for Codex
+
+**Install the `plannotator` command:**
+
+**macOS / Linux / WSL:**
+
+```bash
+curl -fsSL https://plannotator.ai/install.sh | bash
+```
+
+**Windows PowerShell:**
+
+```powershell
+irm https://plannotator.ai/install.ps1 | iex
+```
+
+**Then in Codex, run directly:**
+
+```
+!plannotator review           # Code review for current changes
+!plannotator annotate file.md # Annotate a markdown file
+```
+
+Plan mode is not yet supported.
+
+See [apps/codex/README.md](apps/codex/README.md) for details.
+
+---
+
 ## How It Works
 
 When your AI agent finishes planning, Plannotator:
diff --git a/apps/codex/README.md b/apps/codex/README.md
new file mode 100644
index 0000000..e9defa0
--- /dev/null
+++ b/apps/codex/README.md
@@ -0,0 +1,51 @@
+# Plannotator for Codex
+
+Code review and markdown annotation are supported today. Plan mode is not yet supported — it requires hooks to intercept the agent's plan submission, which Codex does not currently expose.
+
+## Install
+
+**macOS / Linux / WSL:**
+
+```bash
+curl -fsSL https://plannotator.ai/install.sh | bash
+```
+
+**Windows PowerShell:**
+
+```powershell
+irm https://plannotator.ai/install.ps1 | iex
+```
+
+## Usage
+
+### Code Review
+
+Run `!plannotator review` to open the code review UI for your current changes:
+
+```
+!plannotator review
+```
+
+This captures your git diff, opens a browser with the review UI, and waits for your feedback. When you submit annotations, the feedback is printed to stdout.
+
+### Annotate Markdown
+
+Run `!plannotator annotate` to annotate any markdown file:
+
+```
+!plannotator annotate path/to/file.md
+```
+
+## Environment Variables
+
+| Variable | Description |
+|----------|-------------|
+| `PLANNOTATOR_REMOTE` | Set to `1` for remote mode (devcontainer, SSH). Uses fixed port and skips browser open. |
+| `PLANNOTATOR_PORT` | Fixed port to use. Default: random locally, `19432` for remote sessions. |
+| `PLANNOTATOR_BROWSER` | Custom browser to open. macOS: app name or path. Linux/Windows: executable path. |
+
+## Links
+
+- [Website](https://plannotator.ai)
+- [GitHub](https://github.com/backnotprop/plannotator)
+- [Docs](https://plannotator.ai/docs/getting-started/installation/)
diff --git a/apps/marketing/src/content/docs/getting-started/installation.md b/apps/marketing/src/content/docs/getting-started/installation.md
index 080f75e..c984e95 100644
--- a/apps/marketing/src/content/docs/getting-started/installation.md
+++ b/apps/marketing/src/content/docs/getting-started/installation.md
@@ -101,4 +101,11 @@ Coming soon.
 
 ## Codex
 
-Coming soon.
+Plan mode is not yet supported.
+
+Install the binary, then use it directly:
+
+```
+!plannotator review           # Code review for current changes
+!plannotator annotate file.md # Annotate a markdown file
+```