Codex plugin

The HyperMemory plugin for Codex connects the MCP server, installs the HyperMemory skill and hooks, and adds the background memory-writer. It reports exact token counts from Codex.

Before you start

Codex CLI or the Codex app
A HyperMemory account — sign up free
python3 on your PATH (the hooks use it)

Install with one instruction

Paste this into Codex. It runs the commands for you:

Install the HyperMemory plugin from https://github.com/hypermemory-ai/hm-plugins-openai
(first make sure Python 3 and Git are installed on this computer and install them if
they are missing), then start the HyperMemory OAuth sign-in so the authentication page
opens in my browser and wait for me to approve it, and finally download and install the
latest HyperMemory skill.

Then run /hooks and trust the HyperMemory hooks.

Install it yourself

Add the marketplace

codex plugin marketplace add hypermemory-ai/hm-plugins-openai

Install the plugin

codex plugin add hypermemory@hypermemory-ai

Codex asks you to sign in to HyperMemory during install. Approve the connection in your browser.

Trust the hooks

In Codex CLI, run /hooks and trust the HyperMemory hooks. Codex skips plugin hooks until you trust them, and asks again whenever a hook changes.

Verify

Start a new Codex session and ask:

What do you know about this project?

Codex should call hm_get_overview and hm_recall before answering.

What the plugin installs

Component	What it does
`hypermemory` skill	The every-turn HyperMemory protocol.
`memory-writer` skill and agent	Saves the turn’s new facts, links them, writes the timeline and reports tokens.
SessionStart and UserPromptSubmit hooks	Load the skill on start, resume, clear, compaction and every prompt.
PreToolUse hook	Holds other tools until `hm_get_overview` and `hm_recall` have run for the turn.
Stop hook	Hands the turn to the memory-writer, which reports exact token counts from Codex.

Organization memory and per-project organization binding work exactly as in the Claude Code plugin.

Update

codex plugin marketplace upgrade hypermemory-ai
codex plugin add hypermemory@hypermemory-ai

Trust the updated hooks with /hooks afterwards.

Uninstall

codex plugin remove hypermemory@hypermemory-ai
codex plugin marketplace remove hypermemory-ai

Removing the plugin doesn’t delete anything from your memory.

Without the plugin

hm setup codex installs the same protocol through the CLI, using hm commands instead of MCP. Or add the MCP server yourself in ~/.codex/config.toml:

[mcp_servers.hypermemory]
url = "https://api.hypermemory.io/mcp"

Then run codex mcp login hypermemory to sign in.