feat: add support for Codex agent

[mscolnick]

Adds Codex to the available agents in the ACP sidebar and many other fixes:

• Add Codex command to the Agent dropdown
• Disable bottom buttons when the agent is running
• Dedupe todos/plans (in case they have status updates)
• some tools don't send a completion update, so we just always mark them completed if they are no longer the last block
• Collapse unchanged regions in the diff viewer
• Handle edge case when Claude ACP returns a different schema than the ACP protocol expects for diffs (HACK: if the raw input is abs_path, old_string, new_string then handle it as if it is a diff)
• Handle edge case were the title comes back "undefined" from the ACP

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Project	Deployment	Preview	Comments	Updated (UTC)
marimo-docs	Ready	Preview	Comment	Oct 28, 2025 1:26pm

[dmadisetti]

Had to pnpm add vega-util to build- but might be user error and/ or unrelated churn.
Wasn't able to login out the box:

[Server → Client]: {
  jsonrpc: '2.0',
  id: 0,
  result: {
    protocolVersion: 1,
    agentCapabilities: {
      loadSession: false,
      promptCapabilities: { image: true, audio: false, embeddedContext: true },
      mcpCapabilities: { http: true, sse: false }
    },
    authMethods: [
      {
        id: 'chatgpt',
        name: 'Login with ChatGPT',
        description: 'Use your ChatGPT login with Codex CLI (requires a paid ChatGPT subscription)'
      },
      {
        id: 'codex-api-key',
        name: 'Use CODEX_API_KEY',
        description: 'Requires setting the `CODEX_API_KEY` environment variable.'
      },
      {
        id: 'openai-api-key',
        name: 'Use OPENAI_API_KEY',
        description: 'Requires setting the `OPENAI_API_KEY` environment variable.'
      }
    ],
    agentInfo: { name: 'codex-acp', title: 'Codex', version: '0.3.10' }
  }
}
[stdio-to-ws] Child stderr: 2025-10-27T21:49:55.345020Z ERROR codex_core::codex: Failed to create session: cwd is not absolute: ""

[Server → Client]: {
  jsonrpc: '2.0',
  id: 1,
  error: { code: -32603, message: 'Internal error' }
}

Also tried the API_KEY. But codex by itself does work. Notice codex is slow, but I think that's just codex in general.

Changes look good by themselves

[Light2Dark]

should it be this?

Suggested change

	const prefix = title || Strings.startCase(item.kind || "") || "Tool call";
	const prefix = title || (item.kind ? Strings.startCase(item.kind) : "Tool call");

[mscolnick]

it evaluates to the same