Document ChatGPT Desktop configuration via ngrok tunnel

Author: danbarr

docs/toolhive/reference/client-compatibility.mdx

@@ -40,13 +40,14 @@ We've tested ToolHive with these clients:
 | Windsurf IDE               |    ✅     |         ✅         |       ✅       |                                             |
 | Windsurf (JetBrains)       |    ✅     |         ✅         |       ❌       |                                             |
 | Zed                        |    ✅     |         ✅         |       ❌       | v0.214.5+                                   |
-| ChatGPT Desktop            |    ✅     |         ❌         |       ❌       | See [STDIO-only client configuration][4]    |
+| ChatGPT Desktop            |    ✅     |         ❌         |       ❌       | See [ChatGPT Desktop configuration][5]      |
 | Claude Desktop             |    ✅     |         ❌         |       ❌       | See [STDIO-only client configuration][4]    |
 | GitHub Copilot (JetBrains) |    ✅     |         ❌         |       ❌       | v1.5.47+                                    |
 | PydanticAI                 |    ✅     |         ❌         |       ❌       | v0.2.18+                                    |
 
 [3]: #vs-code-with-copilot
 [4]: #stdio-only-client-configuration
+[5]: #chatgpt-desktop-configuration
 
 The minimum versions listed are the earliest versions that support the
 Streamable HTTP transport protocol.
@@ -373,6 +374,65 @@ even though it uses SSE transport.
 For more details, see the
 [`thv proxy stdio` CLI reference](../reference/cli/thv_proxy_stdio.md).
 
+### ChatGPT Desktop configuration
+
+ChatGPT Desktop only accepts MCP servers over HTTPS — it has no equivalent of
+Claude Desktop's command-based configuration. Use `thv proxy tunnel` to expose
+your local ToolHive server through an [ngrok](https://ngrok.com) tunnel.
+
+**How it works:**
+
+1. ToolHive runs the MCP server in its container with its default transport
+   (SSE, HTTP, or other)
+2. The `thv proxy tunnel` command creates an ngrok HTTPS tunnel pointing to that
+   server
+3. You configure ChatGPT Desktop with the resulting HTTPS URL
+
+**Prerequisites:**
+
+- An ngrok account and auth token
+- A static ngrok domain (recommended, so the connector URL stays stable across
+  restarts)
+
+**Example:**
+
+First, run an MCP server:
+
+```bash
+thv run osv --transport sse --name osv
+```
+
+Then start the ngrok tunnel, using the workload name as the target:
+
+```bash
+thv proxy tunnel osv osv \
+  --tunnel-provider ngrok \
+  --provider-args '{"auth-token": "<YOUR_NGROK_TOKEN>", "url": "https://<YOUR_NGROK_DOMAIN>", "pooling": true}'
+```
+
+Then configure ChatGPT Desktop:
+
+1. Navigate to **Settings → Connectors → Create**.
+2. Enter a **Connector name** and **Description**.
+3. Set the **Connector URL** to your ngrok domain plus the `/mcp` path, for
+   example `https://<YOUR_NGROK_DOMAIN>/mcp`.
+4. Click **Create**.
+
+After a successful connection, ChatGPT Desktop lists the tools your MCP server
+exposes. You can add them to a conversation by clicking **+** near the message
+composer and selecting your connector.
+
+:::tip
+
+The `url` field in `--provider-args` sets a static ngrok domain. If you omit it,
+ngrok assigns a temporary random URL each time, which means updating the
+connector in ChatGPT Desktop on every restart.
+
+:::
+
+For more details, see the
+[`thv proxy tunnel` CLI reference](../reference/cli/thv_proxy_tunnel.md).
+
 ## Related information
 
 - [Client configuration](../guides-cli/client-configuration.mdx)