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Use this guide to connect Claude Desktop Cowork on third-party inference to CometAPI. This configuration lets Claude Desktop send Claude Messages API requests to CometAPI from the Cowork, Projects, and supported desktop workflows. Official references:
Claude Desktop third-party inference requires an Anthropic-compatible gateway. CometAPI supports Claude models through the Anthropic Messages API.
Content that you send from Claude Desktop is processed by CometAPI and the selected model provider. Do not send confidential data unless your organization allows that workflow.

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Prerequisites

  • Claude Desktop installed from claude.com/download
  • A Claude Desktop build that includes Developer mode and Configure third-party inference
  • A CometAPI account with an active API key
  • Access to Claude models in CometAPI
  • A network path that can reach https://api.cometapi.com
Start from the Claude Desktop sign-in screen. If you already signed in with an Anthropic account, sign out before you configure third-party inference.

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Configuration

1

Enable developer mode

Open Claude Desktop and stay on the sign-in screen. In the application menu, open Help → Troubleshooting, then select Enable Developer Mode.On Windows, the menu can be hard to reach before sign-in. Focus the email field, press Tab until the menu is focused, then press Enter.
2

Open third-party inference settings

After developer mode is enabled, open Developer → Configure third-party inference.The configuration window opens with several sections in the left sidebar. Use the Connection section for the CometAPI settings.
3

Configure the gateway

In the Connection section, enter the CometAPI values below:
FieldValue
Inference providerGateway
GatewayAnthropic-compatible
Gateway base URLhttps://api.cometapi.com
Gateway API keyYour CometAPI API key, such as <COMETAPI_KEY>
Gateway auth schemeBearer
Gateway extra headersLeave blank
Keep the base URL exactly as shown. Claude Desktop requires an HTTPS base URL.The following screenshot shows the Connection section filled with CometAPI values.Claude Desktop Connection settings with the CometAPI gateway base URL, API key field, and bearer auth scheme filled in
4

Add model IDs

In Model list, add these model IDs manually:
Model IDRecommended use
claude-opus-4-7Complex planning and agent tasks
claude-sonnet-4-6General desktop use
claude-haiku-4-5-20251001Lightweight prompts and quick drafts
The first model in the list becomes the default model. Put claude-sonnet-4-6 first if you want a general-purpose default.
Model availability can change. If a model does not appear in Claude Desktop after configuration, verify access on the CometAPI Models page.
The following screenshot shows the model list with the three Claude model IDs configured for CometAPI.Claude Desktop model list showing claude-opus-4-7, claude-sonnet-4-6, and claude-haiku-4-5-20251001 for CometAPI
5

Apply the configuration locally

Click Apply locally. Claude Desktop writes the selected configuration to the local user profile and relaunches the app.If the app does not relaunch, quit Claude Desktop completely and open it again.
6

Start a Cowork session

On the sign-in screen, choose the option for Cowork on third-party inference. Open Cowork or Projects, select one of the configured Claude models, and send a short test prompt.A successful response confirms that Claude Desktop is using CometAPI for model calls.

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Verify the configuration

Use a short prompt that does not require external tools: 
Reply with one sentence: Claude Desktop is connected through CometAPI.
If Claude Desktop returns a response, then the base URL, API key, and model list are configured correctly. The following screenshot shows a successful Cowork reply through CometAPI. Claude Desktop Cowork reply using CometAPI after the third-party inference setup To inspect the detected settings, open Help → Troubleshooting → Copy Managed Configuration Report. Secret values are redacted in the copied report.

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Troubleshooting

Confirm that you selected Help → Troubleshooting → Enable Developer Mode. Then quit Claude Desktop completely and open it again.If the option is missing, install a Claude Desktop build that includes third-party inference configuration.
Check these items:
  • Inference provider is set to Gateway.
  • Gateway base URL is https://api.cometapi.com.
  • Gateway API key contains your CometAPI API key with no extra spaces.
  • You clicked Apply locally and fully restarted Claude Desktop.
Confirm that the base URL starts with https://. Claude Desktop does not accept plain HTTP gateway URLs.Also confirm that your CometAPI account has access to Claude models and that the API key has not been deleted or disabled.
Reopen Developer → Configure third-party inference and check the Model list entries. Model IDs must match the IDs that CometAPI exposes.Add each model ID as a separate entry. Do not include quotes, commas, or extra spaces in the UI fields.
Claude Desktop third-party inference expects an Anthropic-compatible gateway for this flow. Use https://api.cometapi.com and the Claude model IDs listed above.
The Code tab uses the Claude Code engine inside Claude Desktop. Some desktop settings may not apply to Code sessions in the same way that they apply to Cowork.For standalone terminal usage, see the Claude Code integration guide.