feat(cli): Model Context Protocol (MCP) support — client, TUI overlay, config & basic test

[jagzmz]

This PR integrates Model Context Protocol (MCP) into Codex CLI, letting any MCP server’s tools appear as agent‑callable functions.

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✨ Key additions

Area	Change
Runtime	MCPClient & MCPManager manage connections, cache server metadata, flatten tools for OpenAI function‑calling, and clean up on exit.
UI (Ink/React)	MCPProvider, useMcpManager hook, and mcp‑overlay panel show live server status & tool lists; /mcp slash‑command “List MCP servers”.
Config loading	AgentLoop now accepts an optional mcpTools array; quiet‑mode path instantiates/initialises MCPManager.
Package deps	Adds @modelcontextprotocol/sdk ^1.11.0; updates lock‑file.
Tests	New Jest suites for manager initialisation, tool‑flattening, and adjusted TerminalChatInput signature.
Polish	Warn earlier when context budget is > 25 %; TerminalChatInput callbacks simplified to return void.

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🛠️ Example Configuration

Add an mcpServers block to ~/.codex/config.json
Each key is a friendly name; values mirror a spawn‑style process descriptor:

{
  // …existing config …
  "mcpServers": {
    "jina ai": {
      "command": "npx",
      "args": [
        "-y",
        "jina-ai-mcp-server"
      ],
      "env": {
        "JINA_API_KEY=xxx"          // <- your key here
      }
    },
    "memory": {
      "command": "npx",
      "args": [
        "-y",
        "@modelcontextprotocol/server-memory"
      ]
    }
  }
}

---

📸 Demo

Attached: TUI listing two live MCP servers

[github-actions]

All contributors have signed the CLA ✍️ ✅
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[jagzmz]

I have read the CLA Document and I hereby sign the CLA

[jagzmz]

Tagging maintainers @tibo-openai @bolinfest for review. Thank you!

[bolinfest]

@jagzmz this is exciting stuff and obviously a complex change! Incidentally, I am actively working on making the analogous change in the Rust CLI: #829.

[bolinfest]

@jagzmz in your example, I see JINA_API_KEY=xxx in args, but shouldn't that be in env?

[jagzmz]

@jagzmz in your example, I see JINA_API_KEY=xxx in args, but shouldn't that be in env?

Yes, it should be, i picked up an old example i had with me : P, anyways, I have updated the example.

[jagzmz]

this is exciting stuff and obviously a complex change! Incidentally, I am actively working on making the analogous change in the Rust CLI:

Nice! Are new feature updates to the TS variant paused ?

[jagzmz]

Hi @bolinfest , would appreciate a review on this pull request. Thanks!

I am wondering if new features are halted on the TS variant?

[bolinfest]

@jagzmz Hi, sorry for dragging our feet here: we're actively discussing how we want to balance TS versus Rust going forward (and to publish the plan).

That said, I think @fouad-openai was going to try to review a number of the TS PRs in once he gets a free moment...