codex - 💡(How to fix) Fix Codex CLI does not interpolate ${CLAUDE_PLUGIN_ROOT} in plugin .mcp.json args, breaking imessage MCP [1 comments, 2 participants]

Summary

The imessage plugin from anthropics/claude-plugins-official ships a .mcp.json that references ${CLAUDE_PLUGIN_ROOT} — a placeholder Claude Code interpolates with the plugin install dir. Codex CLI passes the literal string through to the spawned process, so bun run --cwd ${CLAUDE_PLUGIN_ROOT} ... fails with ENOENT: Could not change directory to "${CLAUDE_PLUGIN_ROOT}".

Reproduction

1. codex plugin marketplace add claude-plugins-official https://github.com/anthropics/claude-plugins-official.git
2. Enable imessage@claude-plugins-official
3. Launch Codex — startup log shows: MCP client for \imessage` failed to start: MCP startup failed: handshaking with MCP server failed: connection closed: initialize response`

`codex mcp list` confirms the literal placeholder:

``` imessage bun run --cwd ${CLAUDE_PLUGIN_ROOT} --shell=bun --silent start ```

Expected

Codex CLI should interpolate `${CLAUDE_PLUGIN_ROOT}` (and likely `${CLAUDE_PLUGIN_DATA}`, etc.) in `.mcp.json` `args[]` and `command` per the Claude Code plugin spec, since plugins shared between marketplaces rely on this idiom.

Workaround

Register a custom MCP via `codex mcp add` with the absolute install path; or edit cache `.mcp.json` (reverts on plugin re-extract).

Affected versions

Codex CLI (current GA as of 2026-04-25), claude-plugins-official imessage 0.1.0.