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Codex plugin

The REL plugin connects Codex to REL’s persistent embedded Chromium sessions. It configures the MCP server bundled with the installed app and adds the rel-browser skill for interactive browser work plus the crawl-websites-with-rel skill for restartable, history-preserving crawls.

Related documents: MCP server and CLI.

For provider setup and per-Session assignment, see Configure proxies.

Requirements

Section titled “Requirements”
  • macOS 15 or later;
  • REL installed on the Mac;
  • a Codex release with plugin marketplace support.

REL.app must be installed so Codex can start its bundled Contents/Resources/rel-mcp adapter. The app does not need to be running for plugin discovery or rel_status; other validated tool calls start it lazily.

The plugin checks /Applications/REL.app, ~/Applications/REL.app, then macOS application registration using bundle ID me.rel.Rel. Set REL_APP_PATH in the MCP host’s environment to select a custom bundle path. Discovery does not launch REL; an invalid override reports an error without falling back.

Install

Section titled “Install”

Add this repository as a Codex marketplace, then install the rel plugin:

Terminal window
codex plugin marketplace add https://github.com/rel-me/rel-tools.git --ref main
codex plugin add rel@rel

Start a new Codex task after installation so the task loads the plugin’s skill and MCP tools.

What the plugin adds

Section titled “What the plugin adds”

The plugin contains:

  • the bundled REL MCP server configuration, with automatic app discovery;
  • the rel-browser skill for safe session selection and browser workflows;
  • the crawl-websites-with-rel skill for rendered-link discovery, readiness, checkpoints, capture metadata, bounded retries, and session recovery;
  • all fourteen MCP tools, including bounded semantic reading, opt-in untrusted website notifications, observations, session-group closing, and inline or file-backed screenshots;
  • all eight canonical page actions: click, wait-for, type, clear, press, select, wait, and click-link.

The plugin does not add another browser backend. REL.app remains the only Chromium owner, and every tool call flows through the local versioned API. See the MCP tool reference for complete inputs and action semantics.

Verify

Section titled “Verify”

Begin with a read-only check in a new task:

Use the REL MCP server. Call rel_status, then rel_list_sessions. Do not navigate anywhere.

Codex should discover fourteen rel_* tools without opening REL. If REL is already running, rel_status reports the app, local agent, Browser Proxy, and embedded Chromium bridge. Otherwise it returns the local connection error without launching the app; rel_list_sessions then starts REL lazily.

Update

Section titled “Update”

Refresh the marketplace snapshot and reinstall the current plugin version:

Terminal window
codex plugin marketplace upgrade rel
codex plugin add rel@rel

Version 0.4.2 replaces the old lettermark with REL’s blue optical-lens logo in the marketplace and composer.

Version 0.4.3 names the plugin MCP server REL so Codex preserves the brand’s capitalization in its MCP servers list. The plugin identifier remains rel@rel, the adapter remains rel-mcp, and tool names remain rel_*.

Version 0.4.4 instructs both bundled skills to use REL in user-facing text. The MCP adapter source also gives every tool an explicit REL title; those titles require a REL app release containing the updated adapter.

Version 0.4.5 discovers REL outside /Applications and supports a REL_APP_PATH override.

Start another new task after updating so it uses the refreshed plugin cache.