feat(mcp-server): the canvas shell is the default preview, the classic page behind DRAWIO_PREVIEW_UI=classic

packages/mcp-server/tests/e2e/shell.spec.ts

@@ -1,8 +1,8 @@
 /**
- * The canvas shell as start_session opens it with DRAWIO_PREVIEW_UI=shell:
- * the built server (dist/index.js, or the copy MCP_SERVER_ENTRY names: CI
- * installs the packed tarball in an empty directory) runs over stdio as an
- * MCP client would start it, and headless Chromium opens the URL it returns.
+ * The canvas shell as start_session opens it by default: the built server
+ * (dist/index.js, or the copy MCP_SERVER_ENTRY names: CI installs the packed
+ * tarball in an empty directory) runs over stdio as an MCP client would
+ * start it, and headless Chromium opens the URL it returns.
  */
 import { mkdtempSync, readFileSync, rmSync } from "node:fs"
 import { tmpdir } from "node:os"
@@ -26,7 +26,6 @@ test.beforeAll(async () => {
         env: {
             ...process.env,
             DRAWIO_DATA_DIR: dataDir,
-            DRAWIO_PREVIEW_UI: "shell",
             // Away from the web app's dev server and other test runs
             PORT: String(6100 + Math.floor(Math.random() * 400)),
             BROWSER: "none",

packages/mcp-server/tests/http-server.test.ts

@@ -27,6 +27,7 @@ import {
     keepInHistory,
     onSessionRecreate,
     onStateChange,
+    previewUiFromEnv,
     previewUrl,
     requestExport,
     requestSelection,
@@ -928,7 +929,15 @@ describe("canvas shell page", () => {
         }
     })
 
-    it("is what start_session opens with DRAWIO_PREVIEW_UI=shell", () => {
+    it("is what start_session opens, unless DRAWIO_PREVIEW_UI=classic", () => {
+        expect(previewUiFromEnv({})).toBe("shell")
+        expect(previewUiFromEnv({ DRAWIO_PREVIEW_UI: "shell" })).toBe("shell")
+        expect(previewUiFromEnv({ DRAWIO_PREVIEW_UI: "classic" })).toBe(
+            "classic",
+        )
+        expect(previewUiFromEnv({ DRAWIO_PREVIEW_UI: "Classic" })).toBe(
+            "classic",
+        )
         expect(previewUrl(6002, "mcp-x", "shell")).toBe(
             "http://localhost:6002/shell/?mcp=mcp-x",
         )

packages/mcp-server/tests/server-wiring.test.ts

@@ -95,9 +95,9 @@ beforeAll(async () => {
             ...process.env,
             DRAWIO_DATA_DIR: dataDir,
             // For the session tests at the end: no browser window, the
-            // canvas shell as the preview, a port away from other servers
+            // default preview (the canvas shell), a port away from other
+            // servers
             BROWSER: "none",
-            DRAWIO_PREVIEW_UI: "shell",
             PORT: String(6500 + Math.floor(Math.random() * 400)),
         },
     }) as ChildProcessWithoutNullStreams