fix: what the batch C review found

- A redirect followed for a custom base URL (quota on) no longer carries
  the user's key or cookies to another origin, as fetch itself does, and
  a private address may redirect to another private one (already counted).
- The admin Test of an Ollama or Vertex AI entry without a URL goes where
  chat sends that entry's key: the environment's own URL variable, for
  Ollama else the local default. The Test of an Ollama Cloud key without
  a URL went to the cloud while chat went to local Ollama.
- Chat saves: each save notes the chat on screen and the order of the
  reads before reading its data. A save read before switching chats no
  longer writes into the chat switched to, and a copy that waited for its
  thumbnail no longer replaces a newer one.
- "Continue without saving" keeps its button when a later auto-save fails,
  and goes away when a new message is sent.
- A screenshot check that was waiting for its image when the user pressed
  Stop stays skipped after the next message.
- MCP History: draw.io's own copy of a diagram (after get_diagram) no
  longer adds an entry without a picture; a change of background is still
  its own version. The tab ignores an edit's answer that arrives after a
  newer AI write loaded.
- Desktop: a deleted preset is not brought back by a failed switch, and a
  request naming no preset does not stop a rollback. An origin keeping
  an access code counts as having settings.
- .env: a quoted value ending in a backslash ("C:\dir\") is read as dotenv
  reads it.
- The tool card no longer crashes on an id that does not turn into text;
  an older Test's success timer no longer ends a newer Test's spinner.
- Tests that passed without their fix now check it.

packages/mcp-server/src/history.ts

@@ -3,7 +3,9 @@
  * Stores {xml, svg} entries in a circular buffer
  */
 
+import { contentFingerprint } from "./edit-gate.ts"
 import { log } from "./logger.ts"
+import { normalizeToMxfile, parseMxfile } from "./pages.ts"
 
 const MAX_HISTORY = 20
 
@@ -16,6 +18,30 @@ interface HistoryEntry {
 let nextEntryId = 0
 const historyStore = new Map<string, HistoryEntry[]>()
 
+/** Each page's background colour */
+function backgrounds(xml: string): string {
+    const doc = parseMxfile(normalizeToMxfile(xml) ?? xml)
+    if (!doc) return ""
+    return Array.from(doc.querySelectorAll("mxGraphModel"))
+        .map((m) => m.getAttribute("background") || "none")
+        .join(",")
+}
+
+// The same pages, cells and backgrounds. draw.io's own copy of a diagram
+// (a sync reply) adds view and page attributes such as dx, grid and the
+// page size, which the model's XML leaves out, so those are not compared.
+// A document without pages has an empty fingerprint and is compared as
+// text only.
+function sameDiagram(a: string, b: string): boolean {
+    if (a === b) return true
+    const fingerprint = contentFingerprint(a)
+    return (
+        fingerprint !== "" &&
+        fingerprint === contentFingerprint(b) &&
+        backgrounds(a) === backgrounds(b)
+    )
+}
+
 export function addHistory(sessionId: string, xml: string, svg = ""): number {
     let history = historyStore.get(sessionId)
     if (!history) {
@@ -23,10 +49,10 @@ export function addHistory(sessionId: string, xml: string, svg = ""): number {
         historyStore.set(sessionId, history)
     }
 
-    // Dedupe: skip if same as last entry (a change of page settings or
-    // background only is a new version)
+    // Dedupe: skip if same as last entry, also when only re-serialized
+    // (a change of background only is a new version)
     const last = history[history.length - 1]
-    if (last && last.xml === xml) {
+    if (last && sameDiagram(last.xml, xml)) {
         if (svg && !last.svg) last.svg = svg
         return history.length - 1
     }

packages/mcp-server/src/preview/preview.js

@@ -190,8 +190,9 @@ async function pushState(xml, svg = '', baseVersion = currentVersion, source = '
         pushFailing = false;
         if (r.ok) {
             const d = await r.json();
-            // An answer about a state this tab has left since
-            if (sid !== stateId) return;
+            // An answer about a state this tab has left since, or one that
+            // comes after a newer version was loaded or saved
+            if (sid !== stateId || d.version < currentVersion) return;
             currentVersion = d.version;
             lastXml = xml;
             // The canvas changed while this edit was on its way, to

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

@@ -582,6 +582,15 @@ describe("history restore", () => {
         expect(getHistory(id)).toHaveLength(1)
         // The missing image is filled in
         expect(getHistory(id)[0].svg).toBe("SVG")
+        // draw.io's copy of it, as a sync reply brings it back
+        addHistory(
+            id,
+            page("same").replace(
+                "<mxGraphModel>",
+                '<mxGraphModel dx="1244" dy="534" grid="1" pageWidth="850">',
+            ),
+        )
+        expect(getHistory(id)).toHaveLength(1)
     })
 
     it("keeps a version that changed only the background", () => {