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Tutorial: Claude Code CLI + Codex

One quarkus-chat-ui instance using Claude Code CLI (Anthropic), another using Codex (OpenAI), talking to each other via MCP.

1. Install Claude Code CLI​

npm install -g @anthropic-ai/claude-code

Verify:

claude --version

2. Install Codex CLI​

npm install -g @openai/codex

Verify:

codex --version

3. Set API Keys​

export ANTHROPIC_API_KEY=sk-ant-api03-...
export OPENAI_API_KEY=sk-...

4. Download quarkus-chat-ui​

Download from Releases.

chmod +x quarkus-chat-ui-linux-amd64

5. Start Alice with Claude (port 28010)​

Terminal 1:

./quarkus-chat-ui-linux-amd64 \
  -Dchat-ui.provider=claude \
  -Dquarkus.http.port=28010

Open http://localhost:28010

6. Start Bob with Codex (port 28020)​

Terminal 2:

./quarkus-chat-ui-linux-amd64 \
  -Dchat-ui.provider=codex \
  -Dquarkus.http.port=28020

Open http://localhost:28020

7. Register MCP Endpoints​

For Claude Code CLI (so Alice can call Bob):

claude mcp add bob --transport http http://localhost:28020/mcp

For Codex (so Bob can call Alice):

codex mcp add alice --transport http http://localhost:28010/mcp

Verify:

claude mcp list   # shows: bob
codex mcp list    # shows: alice

8. Restart Both Instances​

Both CLIs read MCP registrations at startup.

Terminal 1 (Ctrl+C, then):

./quarkus-chat-ui-linux-amd64 \
  -Dchat-ui.provider=claude \
  -Dquarkus.http.port=28010

Terminal 2 (Ctrl+C, then):

./quarkus-chat-ui-linux-amd64 \
  -Dchat-ui.provider=codex \
  -Dquarkus.http.port=28020

9. Test: Alice (Claude) Sends to Bob (Codex)​

In Alice's browser (http://localhost:28010):

Use mcp__bob__submitPrompt to send "Hello Bob! I'm Claude." to Bob.
Set _caller to http://localhost:28010

10. Verify: Bob (Codex) Receives​

In Bob's browser (http://localhost:28020):

[MCP from localhost:28010] Hello Bob! I'm Claude.

Bob (Codex) can reply using mcp__alice__submitPrompt.

Cleanup​

claude mcp remove bob
codex mcp remove alice

Troubleshooting​

ProblemSolution
Claude can't find mcp__bob__*claude mcp add bob ... and restart Alice
Codex can't find mcp__alice__*codex mcp add alice ... and restart Bob
One direction works, other doesn'tBoth sides need MCP registration