Choose the connection type

For an iMac that will stay powered on, a full desktop host is usually the best choice. You may also add the same iMac as an SSH host if you want direct shell-based project access.

Add the iMac as a full desktop host

On the iMac

1. Install or update the ChatGPT desktop app.
2. Sign in with the same ChatGPT account and workspace used on your other computer.
3. Select Codex in the app.
4. Open Settings > Connections > Control this Mac.
5. Select Set up or Add, approve remote access, and complete any account verification.
6. Enable the option that allows other devices to connect.
7. Add the project folders you want Codex to use on the iMac.
8. If needed, enable Computer Use and install the Chrome extension on the iMac.
9. Keep the ChatGPT app running and prevent the iMac from sleeping when you want remote access.

On the MacBook or other controlling computer

1. Update and open the ChatGPT desktop app.
2. Sign in to the same account and workspace as the iMac.
3. Open Settings > Connections > Control other devices.
4. Select Add, choose the iMac, and complete the pairing flow.
5. Start a new Codex chat and select a project saved on the iMac.

The Control other devices option can vary by rollout. If it is unavailable, use the mobile Remote flow or add the iMac as an SSH host.

Pair a phone with the iMac

1. On the iMac, open Settings > Connections > Control this Mac > Set up/Add.
2. Display the pairing QR code.
3. Scan it using the phone.
4. In the ChatGPT mobile app, confirm the same account and workspace.
5. Complete MFA, SSO, or passkey verification if requested.
6. Open Remote in the mobile app and confirm that the iMac and its projects appear.

Add a computer as an SSH host

Information required

• A short SSH alias, such as office-imac
• Hostname, local DNS name, mesh-VPN name, or IP address
• SSH username
• SSH port, normally 22
• Path to the local private key
• One or more remote project-folder paths

SSH configuration on the controlling Mac

Add a concrete entry to ~/.ssh/config:

Host office-imac
  HostName office-imac.local
  User your-mac-username
  IdentityFile ~/.ssh/id_ed25519_office_imac
  IdentitiesOnly yes
  ServerAliveInterval 60
  ServerAliveCountMax 3

Then verify:

ssh office-imac

On the remote computer, verify Codex is installed, on the login-shell path, and authenticated:

command -v codex
codex --version
codex login status

Finally, in the desktop app:

1. Open Settings > Connections.
2. Choose Add SSH host.
3. Select the concrete SSH alias.
4. Choose and save a remote project folder.
5. Start a new Codex chat using that saved remote project.

Codex discovers concrete aliases from ~/.ssh/config; pattern-only entries such as Host * are not selectable hosts.

What to record for every computer

Display name:
Purpose:
Connection type: Desktop host / SSH host / Both
ChatGPT account and workspace:
Computer hostname:
SSH alias:
SSH username:
SSH port:
Private-key filename (not the key contents):
Project folder paths:
Codex version:
Codex login verified on:
Desktop pairing verified on:
Keep-awake configuration:
Computer Use enabled: Yes / No
Chrome extension installed: Yes / No
Notes:

Security rules

• Never store a private key, password, recovery code, or token in the inventory.
• Store passwords and recovery information in a password manager.
• Protect SSH private keys with a passphrase and use Keychain or ssh-agent.
• Give each computer its own SSH key so access can be revoked independently.
• Use a least-privilege user account for remote work.
• Prefer a VPN or mesh network when a machine is not directly reachable. Do not expose the Codex app-server port to the public internet.
• Remove old devices under Settings > Connections when they are retired or lost.

Troubleshooting order

1. Confirm both desktop apps are current and signed in to the same account and workspace.
2. Confirm the host is awake, online, and running the ChatGPT desktop app.
3. Confirm remote access is enabled under Settings > Connections.
4. For SSH, run ssh alias, command -v codex, and codex login status.
5. Confirm at least one project folder is saved on the host.
6. Restart the ChatGPT desktop app and retry the connection.
7. Re-pair devices if a previously working connection is stale.

Official documentation

• Remote connections
• ChatGPT desktop app
• Desktop app settings

Default

• Codex: start with Spark when appropriate, otherwise Terra
• Claude: start with Sonnet

Escalate only when needed

• Terra/Sonnet struggles: move to Sol/Opus
• Sol/Opus struggles, or the task truly requires maximum capability: move to Astra/Fable

Use lower models for

• Routine coding, UI changes, copy and text changes, repetitive implementation
• Browser clicking and navigation, data entry, and copying information between systems
• Following an established implementation plan and making simple fixes

Use higher models for

• Architecture decisions, complex debugging, major migrations, and security or authentication
• Difficult database decisions, complex integrations, and problems where the correct approach is unclear
• Reviewing high-risk or consequential changes

Important: Sol High is Sol using a higher reasoning level, not a separate model tier. Do not automatically use High or maximum reasoning. Long or tedious does not necessarily mean difficult. Keep Fast mode off unless speed is worth the additional usage. Avoid unnecessarily long threads, start fresh when moving to a substantially different feature or problem. Put permanent project knowledge in repository documentation instead of relying on giant conversation threads. Use the cheapest or lowest model that can reliably complete the task.