diff --git a/README.md b/README.md
index 7d8c297..157a7c1 100644
--- a/README.md
+++ b/README.md
@@ -63,6 +63,25 @@ connected producers in the same workspace.
 - **COMPAS: Clear Live Viewer** — clear that workspace and its replay history.
 - **COMPAS: Restart Live Server** — apply host or port changes immediately.
 
+### Extension API
+
+Other extensions can discover the live server without asking the user to pin a
+port. `compasThreejs.getLiveEndpoint` starts the server if it is not already
+running and resolves to its WebSocket endpoint, or to `undefined` if it could
+not be started:
+
+```ts
+const endpoint = await vscode.commands.executeCommand<string | undefined>(
+  "compasThreejs.getLiveEndpoint",
+);
+// "ws://127.0.0.1:54321/ws"
+```
+
+This exists because the port is normally ephemeral and otherwise appears only in
+the status bar and the clipboard snippet, neither of which another extension can
+read. The workspace to publish into is readable from
+`compasThreejs.live.workspace`.
+
 ### Settings
 
 - `compasThreejs.live.enabled` — start the server after VS Code starts.
diff --git a/package.json b/package.json
index 22910f8..e39553b 100644
--- a/package.json
+++ b/package.json
@@ -35,7 +35,8 @@
     "onCommand:compasThreejs.openLiveViewer",
     "onCommand:compasThreejs.copyConnectionSnippet",
     "onCommand:compasThreejs.restartLiveServer",
-    "onCommand:compasThreejs.clearLiveViewer"
+    "onCommand:compasThreejs.clearLiveViewer",
+    "onCommand:compasThreejs.getLiveEndpoint"
   ],
   "main": "./dist/extension.js",
   "contributes": {
@@ -59,6 +60,10 @@
         "command": "compasThreejs.clearLiveViewer",
         "title": "COMPAS: Clear Live Viewer",
         "icon": "$(clear-all)"
+      },
+      {
+        "command": "compasThreejs.getLiveEndpoint",
+        "title": "COMPAS: Get Live Server Endpoint"
       }
     ],
     "customEditors": [
@@ -119,6 +124,10 @@
         },
         {
           "command": "compasThreejs.clearLiveViewer"
+        },
+        {
+          "command": "compasThreejs.getLiveEndpoint",
+          "when": "false"
         }
       ]
     }
diff --git a/src/extension.ts b/src/extension.ts
index 3c8dd3b..4e4f1d8 100644
--- a/src/extension.ts
+++ b/src/extension.ts
@@ -74,6 +74,20 @@ export function activate(context: vscode.ExtensionContext): void {
         }
       },
     ),
+    // Public API for other extensions: the live server's WebSocket endpoint,
+    // starting the server if it is not already running. The port is normally
+    // ephemeral and is otherwise only visible in the status bar text and the
+    // clipboard snippet, neither of which another extension can read.
+    // Returns undefined if the server could not be started.
+    vscode.commands.registerCommand(
+      "compasThreejs.getLiveEndpoint",
+      async (): Promise<string | undefined> => {
+        if (!(await ensureServer(false))) {
+          return undefined;
+        }
+        return server.endpoint;
+      },
+    ),
     vscode.commands.registerCommand(
       "compasThreejs.copyConnectionSnippet",
       async () => {