---
title: Codex
description: "Add persistent memory to OpenAI Codex with the Mem0 plugin — MCP server, lifecycle hooks, and SDK skill."
---

Add persistent memory to [**OpenAI Codex**](https://openai.com/index/codex/) with the Mem0 plugin. Codex forgets everything between tasks — this plugin fixes that by connecting to Mem0's cloud memory layer via MCP, automatically capturing learnings at key lifecycle points, and retrieving relevant context before every response.

## Prerequisites

Before setting up Mem0 with Codex, ensure you have:

1. A Mem0 Platform account and API key:
   - <a href="https://app.mem0.ai?utm_source=oss&utm_medium=integration-codex" rel="nofollow">Sign up at app.mem0.ai</a>
   - <a href="https://app.mem0.ai/dashboard/api-keys?utm_source=oss&utm_medium=integration-codex" rel="nofollow">Get your API key</a> (starts with `m0-`)

2. OpenAI Codex access

3. Your API key added to your shell profile (persists across sessions):

<CodeGroup>
```bash zsh
echo 'export MEM0_API_KEY="m0-your-api-key"' >> ~/.zshrc
source ~/.zshrc
```

```bash bash
echo 'export MEM0_API_KEY="m0-your-api-key"' >> ~/.bashrc
source ~/.bashrc
```
</CodeGroup>

## Installation

### Option A — Plugin Marketplace (Recommended)

Install the full plugin including MCP server, lifecycle hooks, and SDK skill.

1. Add the Mem0 marketplace:

   ```bash
   codex plugin marketplace add mem0ai/mem0
   ```

2. Restart Codex, open the Plugin Directory, browse the **Mem0 Plugins** marketplace, and install **Mem0**.

<Info>
  Do not combine with Option B. The plugin manifest auto-registers the `mem0` MCP server, so adding both will create a duplicate registration.
</Info>

### Option B — Direct MCP

The fastest way to connect Codex to Mem0 — no plugin, no marketplace. Add to `~/.codex/config.toml`:

```toml
[mcp_servers.mem0]
url = "https://mcp.mem0.ai/mcp"
bearer_token_env_var = "MEM0_API_KEY"
```

Make sure `MEM0_API_KEY` is exported in the shell you launch Codex from, then restart Codex.

<Info>
  Codex's `codex mcp add` CLI only supports stdio MCP servers. Because Mem0's MCP is HTTP/streamable, you configure it by editing `config.toml` directly (or via the **Plugins → Connect to a custom MCP → Streamable HTTP** UI in the Codex app).
</Info>

This gives you the MCP tools but not the lifecycle hooks or SDK skill.

### Managing the Plugin

```bash
codex plugin marketplace upgrade               # pull latest plugin versions
codex plugin marketplace remove mem0-plugins   # unregister the marketplace
```

To update, run `codex plugin marketplace upgrade` to pull the latest from the Mem0 repo.

<Info icon="check">
  After either option, start a new Codex task and ask: *"List my mem0 entities"* or *"Search my memories for hello"*. If the `mem0` tools appear and respond, you're all set.
</Info>

## What's Included

| Component | Plugin Install | MCP Only |
|-----------|:--------------:|:--------:|
| MCP Server (9 memory tools) | Yes | Yes |
| Lifecycle Hooks | Yes | No |
| Mem0 SDK Skill | Yes | No |

## Available MCP Tools

Once installed, the following tools are available in every Codex session:

| Tool | Description |
|------|-------------|
| `add_memory` | Save text or conversation history for a user/agent |
| `search_memories` | Semantic search across memories with filters |
| `get_memories` | List memories with filters and pagination |
| `get_memory` | Retrieve a specific memory by ID |
| `update_memory` | Overwrite a memory's text by ID |
| `delete_memory` | Delete a single memory by ID |
| `delete_all_memories` | Bulk delete all memories in scope |
| `delete_entities` | Delete a user/agent/app/run entity and its memories |
| `list_entities` | List users/agents/apps/runs stored in Mem0 |

## Lifecycle Hooks

When installed via the plugin marketplace, Mem0 hooks into Codex's lifecycle to automatically manage memory:

| Hook | Event | What it does |
|------|-------|-------------|
| **Session start** | `SessionStart` | Loads prior memories and displays status banner |
| **User prompt** | `UserPromptSubmit` | Searches relevant memories before each message |
| **Pre-tool** | `PreToolUse` | Blocks MEMORY.md writes, enforces `user_id`/`app_id` on mem0 tool calls |
| **Post-tool** | `PostToolUse` | Tracks stats, scans bash errors for related memories |
| **Pre-compact** | `PreCompact` | Stores a session summary before context compaction |

## Example Workflow

```text
# Task 1: Setting up a new service
You: Create a REST API for the notifications service using Express and TypeScript.

# Codex searches memories, finds user preferences from prior tasks.
# After completing the task, Mem0 stores:
#   - Decision: "Notifications service uses Express + TypeScript + Zod validation"
#   - Convention: "All API routes follow /api/v1/{resource} pattern"
#   - Preference: "User prefers explicit error types over generic catch-all"

# Task 2 (days later): Extending the service
You: Add WebSocket support for real-time notification delivery.

# Codex searches memories, retrieves the architecture decisions and conventions.
# Follows the same patterns established in the first task.
```

## Troubleshooting

- **"Connection failed"** — Verify `MEM0_API_KEY` is set: `echo $MEM0_API_KEY`
- **No tools appearing** — Restart your Codex session after installation
- **Duplicate `mem0` MCP / "tool collision" errors** — You combined Option A with Option B. Remove the `[mcp_servers.mem0]` block from `~/.codex/config.toml`; the plugin registers it automatically
- **Hooks not firing** — Ensure the plugin is installed via the marketplace (Option A). MCP-only installs do not include hooks

<CardGroup cols={2}>
  <Card title="Mem0 MCP Setup" icon="puzzle-piece" href="/platform/mem0-mcp">
    Detailed MCP configuration for all clients
  </Card>
  <Card title="Claude Code Integration" icon={<svg width="24" height="25" viewBox="0 0 24 25" fill="none" xmlns="http://www.w3.org/2000/svg"><path d="M5.92888 16.2181L9.86008 14.0122L9.92585 13.8199L9.86008 13.7137H9.66782L9.01009 13.6732L6.76369 13.6125L4.81581 13.5315L2.92863 13.4303L2.45304 13.3292L2.00781 12.7423L2.05335 12.4488L2.45304 12.1807L3.02476 12.2313L4.28962 12.3173L6.18692 12.4488L7.56309 12.5298L9.60204 12.7423H9.92585L9.97138 12.6107L9.86008 12.5298L9.77407 12.4488L7.811 11.1182L5.68603 9.71165L4.57295 8.90214L3.97088 8.49233L3.66731 8.10781L3.53577 7.26794L4.08219 6.66587L4.81581 6.71646L5.00301 6.76706L5.74674 7.33877L7.33541 8.56822L9.40979 10.0962L9.71335 10.3491L9.83478 10.2631L9.84996 10.2024L9.71335 9.97475L8.5851 7.93579L7.38095 5.86141L6.84465 5.00131L6.70298 4.48524C6.65239 4.27275 6.61697 4.09567 6.61697 3.87811L7.23928 3.03318L7.58332 2.92188L8.41307 3.03318L8.76218 3.33675L9.27824 4.5156L10.113 6.37242L11.4083 8.89708L11.7877 9.64588L11.9901 10.339L12.066 10.5515H12.1975V10.4301L12.3038 9.00839L12.5011 7.26288L12.6934 5.01649L12.7591 4.38406L13.0728 3.62514L13.6951 3.21532L14.1808 3.44806L14.5805 4.01978L14.5249 4.38912L14.2871 5.93225L13.8216 8.35066L13.5181 9.96969H13.6951L13.8975 9.76731L14.7171 8.67953L16.0933 6.95931L16.7005 6.27629L17.4088 5.52243L17.8641 5.16321H18.7242L19.3567 6.10427L19.0733 7.07568L18.1879 8.19888L17.4543 9.15006L16.4019 10.5667L15.7442 11.7L15.8049 11.7911L15.9618 11.7759L18.3397 11.27L19.6248 11.0372L21.1578 10.7741L21.851 11.0979L21.9269 11.4268L21.6537 12.0997L20.0144 12.5045L18.0918 12.889L15.2282 13.567L15.1927 13.5923L15.2332 13.6428L16.5234 13.7643L17.0749 13.7946H18.4257L20.9403 13.9818L21.598 14.4169L21.9926 14.9482L21.9269 15.3529L20.915 15.869L19.5489 15.5452L16.3615 14.7863L15.2686 14.5131H15.1168V14.6041L16.0275 15.4946L17.6972 17.0023L19.7867 18.9451L19.893 19.4258L19.6248 19.8053L19.3415 19.7648L17.5049 18.3835L16.7966 17.7612L15.1927 16.4104H15.0865V16.552L15.4558 17.0934L17.4088 20.0279L17.51 20.9285L17.3683 21.2219L16.8624 21.399L16.3058 21.2978L15.1624 19.6939L13.9835 17.8877L13.0324 16.2687L12.916 16.3345L12.3544 22.3805L12.0913 22.6891L11.4842 22.9219L10.9782 22.5374L10.7101 21.915L10.9782 20.6856L11.302 19.0818L11.5651 17.8068L11.8029 16.2232L11.9446 15.697L11.9345 15.6616L11.8181 15.6767L10.6241 17.316L8.80771 19.7698L7.37083 21.3079L7.02679 21.4445L6.42977 21.1359L6.48542 20.5844L6.81935 20.0936L8.80771 17.5639L10.0068 15.9955L10.7809 15.0898L10.7758 14.9583H10.7303L5.44824 18.3886L4.50718 18.51L4.10242 18.1306L4.15302 17.5083L4.34528 17.3059L5.93394 16.213L5.92888 16.2181Z" fill="currentColor"/></svg>} href="/integrations/claude-code">
    Add Mem0 memory to Claude Code workflows
  </Card>
</CardGroup>