diff --git a/apps/client/src/features/notification/notification.utils.test.ts b/apps/client/src/features/notification/notification.utils.test.ts
index 14d99d0e..2cfd7f55 100644
--- a/apps/client/src/features/notification/notification.utils.test.ts
+++ b/apps/client/src/features/notification/notification.utils.test.ts
@@ -1,5 +1,7 @@
 import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import i18n from "@/i18n.ts";
 import {
+  formatRelativeTime,
   getTimeGroup,
   groupNotificationsByTime,
 } from "@/features/notification/notification.utils.ts";
@@ -132,3 +134,59 @@ describe("groupNotificationsByTime", () => {
     expect(groupNotificationsByTime([], labels)).toEqual([]);
   });
 });
+
+describe("formatRelativeTime — relative buckets and absolute-date fallback", () => {
+  // Distinct fixed clock for the relative formatter (uses Date.now via `new
+  // Date()`), so the bucket boundaries are deterministic under fake timers.
+  const NOW = new Date("2026-06-15T12:00:00.000Z");
+  const MIN = 60_000;
+
+  beforeEach(() => {
+    vi.setSystemTime(NOW);
+  });
+
+  // ISO string `ms` milliseconds before NOW.
+  function ago(ms: number): string {
+    return new Date(NOW.getTime() - ms).toISOString();
+  }
+
+  it("returns the i18n 'now' label for anything under a minute", () => {
+    expect(formatRelativeTime(ago(0))).toBe(i18n.t("now"));
+    expect(formatRelativeTime(ago(59_000))).toBe(i18n.t("now"));
+  });
+
+  it("crosses into the minutes bucket exactly at 1 minute", () => {
+    expect(formatRelativeTime(ago(MIN - 1000))).toBe(i18n.t("now"));
+    expect(formatRelativeTime(ago(MIN))).toBe("1m");
+    expect(formatRelativeTime(ago(5 * MIN))).toBe("5m");
+    expect(formatRelativeTime(ago(59 * MIN))).toBe("59m");
+  });
+
+  it("crosses into the hours bucket exactly at 60 minutes", () => {
+    expect(formatRelativeTime(ago(60 * MIN - 1000))).toBe("59m");
+    expect(formatRelativeTime(ago(HOUR))).toBe("1h");
+    expect(formatRelativeTime(ago(23 * HOUR))).toBe("23h");
+  });
+
+  it("crosses into the days bucket exactly at 24 hours", () => {
+    expect(formatRelativeTime(ago(24 * HOUR - 1000))).toBe("23h");
+    expect(formatRelativeTime(ago(DAY))).toBe("1d");
+    expect(formatRelativeTime(ago(6 * DAY))).toBe("6d");
+  });
+
+  it("falls back to an absolute short date once >= 7 days old", () => {
+    // 6d -> still relative; 7d -> absolute date (no longer N[mhd], and equal to
+    // the localized short-date of the source timestamp).
+    expect(formatRelativeTime(ago(6 * DAY))).toBe("6d");
+
+    const sevenDaysAgo = ago(7 * DAY);
+    const result = formatRelativeTime(sevenDaysAgo);
+    expect(result).not.toMatch(/^\d+[mhd]$/);
+    expect(result).not.toBe(i18n.t("now"));
+    const expected = new Intl.DateTimeFormat(i18n.language, {
+      month: "short",
+      day: "numeric",
+    }).format(new Date(sevenDaysAgo));
+    expect(result).toBe(expected);
+  });
+});
diff --git a/apps/client/src/features/page/tree/utils/find-breadcrumb-path.test.ts b/apps/client/src/features/page/tree/utils/find-breadcrumb-path.test.ts
new file mode 100644
index 00000000..0dff0f79
--- /dev/null
+++ b/apps/client/src/features/page/tree/utils/find-breadcrumb-path.test.ts
@@ -0,0 +1,79 @@
+import { describe, it, expect } from "vitest";
+import { findBreadcrumbPath } from "./utils";
+import type { SpaceTreeNode } from "@/features/page/tree/types.ts";
+
+// findBreadcrumbPath walks the live, SHARED sidebar tree. The high-value
+// invariant: when a node has no usable name it must surface "Untitled" ONLY on
+// the returned breadcrumb chain via a shallow copy — never by mutating the input
+// node (which would silently rename the node in the sidebar). Also covers normal
+// ancestor-chain resolution, the not-found case, and nested children.
+
+function node(id: string, over: Partial<SpaceTreeNode> = {}): SpaceTreeNode {
+  return {
+    id,
+    slugId: `slug-${id}`,
+    name: id.toUpperCase(),
+    icon: undefined,
+    position: "a0",
+    spaceId: "space-1",
+    parentPageId: null as unknown as string,
+    hasChildren: false,
+    children: [],
+    ...over,
+  };
+}
+
+describe("findBreadcrumbPath", () => {
+  it("does NOT mutate the input tree when a node has an empty/whitespace name", () => {
+    // A whitespace-only-named node nested under a blank-named root.
+    const target = node("target", { name: "   " });
+    const root = node("root", { name: "", hasChildren: true, children: [target] });
+    const tree = [root];
+
+    const result = findBreadcrumbPath(tree, "target");
+
+    expect(result).not.toBeNull();
+    // The RETURNED chain shows "Untitled" for both blank nodes.
+    expect(result!.map((n) => n.name)).toEqual(["Untitled", "Untitled"]);
+    // The original input nodes are untouched (still blank).
+    expect(root.name).toBe("");
+    expect(target.name).toBe("   ");
+    // The renamed breadcrumb entries are fresh copies, not the input objects.
+    expect(result![0]).not.toBe(root);
+    expect(result![1]).not.toBe(target);
+  });
+
+  it("returns the SAME node reference (no copy) when the name is non-empty", () => {
+    // No rename needed -> the node is passed through by reference (cheap path).
+    const target = node("target", { name: "Real Title" });
+    const result = findBreadcrumbPath([target], "target");
+    expect(result![0]).toBe(target);
+    expect(result![0].name).toBe("Real Title");
+  });
+
+  it("resolves the full ancestor chain ending at the target", () => {
+    const target = node("c");
+    const mid = node("b", { hasChildren: true, children: [target] });
+    const root = node("a", { hasChildren: true, children: [mid] });
+    const result = findBreadcrumbPath([root], "c");
+    expect(result!.map((n) => n.id)).toEqual(["a", "b", "c"]);
+  });
+
+  it("finds a target nested under a deeper sibling branch", () => {
+    // Two root branches; the target lives inside the second branch's child.
+    const target = node("deep");
+    const branch2 = node("r2", {
+      hasChildren: true,
+      children: [node("x"), node("y", { hasChildren: true, children: [target] })],
+    });
+    const branch1 = node("r1", { hasChildren: true, children: [node("z")] });
+    const result = findBreadcrumbPath([branch1, branch2], "deep");
+    expect(result!.map((n) => n.id)).toEqual(["r2", "y", "deep"]);
+  });
+
+  it("returns null when the page id is not present in the tree", () => {
+    const root = node("root", { hasChildren: true, children: [node("child")] });
+    expect(findBreadcrumbPath([root], "missing")).toBeNull();
+    expect(findBreadcrumbPath([], "anything")).toBeNull();
+  });
+});
diff --git a/apps/client/src/features/page/tree/utils/utils.test.ts b/apps/client/src/features/page/tree/utils/utils.test.ts
index 4ea181b5..0eced376 100644
--- a/apps/client/src/features/page/tree/utils/utils.test.ts
+++ b/apps/client/src/features/page/tree/utils/utils.test.ts
@@ -8,6 +8,8 @@ import {
   closeIds,
   mergeRootTrees,
   loadedOpenBranchIds,
+  sortPositionKeys,
+  pageToTreeNode,
 } from "./utils";
 import type { IPage } from "@/features/page/types/page.types.ts";
 import type { SpaceTreeNode } from "@/features/page/tree/types.ts";
@@ -60,6 +62,82 @@ function treeNode(id: string, children: SpaceTreeNode[] = []): SpaceTreeNode {
   };
 }
 
+describe("sortPositionKeys", () => {
+  it("orders items ascending by their fractional `position` string", () => {
+    const items = [
+      { id: "c", position: "a5" },
+      { id: "a", position: "a1" },
+      { id: "b", position: "a3" },
+    ];
+    expect(sortPositionKeys(items).map((i) => i.id)).toEqual(["a", "b", "c"]);
+  });
+
+  it("is a stable sort: equal positions keep their input order", () => {
+    const items = [
+      { id: "x", position: "a1" },
+      { id: "y", position: "a1" },
+      { id: "z", position: "a1" },
+    ];
+    expect(sortPositionKeys(items).map((i) => i.id)).toEqual(["x", "y", "z"]);
+  });
+});
+
+describe("pageToTreeNode", () => {
+  function pageRow(over: Partial<IPage> = {}): IPage {
+    return {
+      id: "p1",
+      slugId: "slug-p1",
+      title: "My Page",
+      icon: "📄",
+      position: "a1",
+      hasChildren: true,
+      spaceId: "space-1",
+      parentPageId: null as unknown as string,
+      ...over,
+    } as IPage;
+  }
+
+  it("maps page.title -> node.name and copies the core fields", () => {
+    const node = pageToTreeNode(pageRow());
+    // The non-trivial transform: a page's `title` becomes the tree node's `name`.
+    expect(node.name).toBe("My Page");
+    expect(node.id).toBe("p1");
+    expect(node.slugId).toBe("slug-p1");
+    expect(node.icon).toBe("📄");
+    expect(node.position).toBe("a1");
+    expect(node.spaceId).toBe("space-1");
+    expect(node.hasChildren).toBe(true);
+    // Always materialized with an empty children array.
+    expect(node.children).toEqual([]);
+  });
+
+  it("derives canEdit from page.permissions.canEdit when the flat field is absent", () => {
+    const node = pageToTreeNode(
+      pageRow({ canEdit: undefined, permissions: { canEdit: true } } as Partial<IPage>),
+    );
+    expect(node.canEdit).toBe(true);
+  });
+
+  it("prefers the flat page.canEdit over permissions.canEdit", () => {
+    const node = pageToTreeNode(
+      pageRow({ canEdit: false, permissions: { canEdit: true } } as Partial<IPage>),
+    );
+    expect(node.canEdit).toBe(false);
+  });
+
+  it("carries temporaryExpiresAt straight off the page", () => {
+    const expiresAt = "2026-06-27T21:00:00.000Z";
+    expect(pageToTreeNode(pageRow({ temporaryExpiresAt: expiresAt })).temporaryExpiresAt).toBe(
+      expiresAt,
+    );
+  });
+
+  it("applies overrides on top of the mapped fields (e.g. optimistic blank name)", () => {
+    const node = pageToTreeNode(pageRow(), { name: "" });
+    expect(node.name).toBe("");
+  });
+});
+
 describe("buildTree", () => {
   it("builds one node per unique page", () => {
     const tree = buildTree([page("a", "a1"), page("b", "a2")]);
diff --git a/apps/client/src/features/page/tree/utils/utils.ts b/apps/client/src/features/page/tree/utils/utils.ts
index 11600162..d5084b00 100644
--- a/apps/client/src/features/page/tree/utils/utils.ts
+++ b/apps/client/src/features/page/tree/utils/utils.ts
@@ -70,18 +70,22 @@ export function findBreadcrumbPath(
   path: SpaceTreeNode[] = [],
 ): SpaceTreeNode[] | null {
   for (const node of tree) {
-    if (!node.name || node.name.trim() === "") {
-      node.name = "Untitled";
-    }
+    // Never mutate the input tree (it is the live, shared sidebar tree state).
+    // When a node has no usable name, surface "Untitled" via a shallow copy that
+    // only the returned breadcrumb chain sees — the source node stays untouched.
+    const displayNode: SpaceTreeNode =
+      !node.name || node.name.trim() === ""
+        ? { ...node, name: "Untitled" }
+        : node;
 
     if (node.id === pageId) {
-      return [...path, node];
+      return [...path, displayNode];
     }
 
     if (node.children) {
       const newPath = findBreadcrumbPath(node.children, pageId, [
         ...path,
-        node,
+        displayNode,
       ]);
       if (newPath) {
         return newPath;
diff --git a/apps/client/src/features/websocket/tree-socket-reducers.test.ts b/apps/client/src/features/websocket/tree-socket-reducers.test.ts
index 81c62b56..ae93a714 100644
--- a/apps/client/src/features/websocket/tree-socket-reducers.test.ts
+++ b/apps/client/src/features/websocket/tree-socket-reducers.test.ts
@@ -3,6 +3,7 @@ import {
   applyAddTreeNode,
   applyMoveTreeNode,
   applyDeleteTreeNode,
+  applyUpdateOne,
 } from "./tree-socket-reducers";
 import { treeModel } from "@/features/page/tree/model/tree-model";
 import { SpaceTreeNode } from "@/features/page/tree/types.ts";
@@ -338,3 +339,76 @@ describe("applyAddTreeNode", () => {
     expect(treeModel.find(next, "temp")?.temporaryExpiresAt).toBe(expiresAt);
   });
 });
+
+describe("applyUpdateOne", () => {
+  // A loaded two-level tree so we can patch both a root and a nested node.
+  const buildTree = (): SpaceTreeNode[] => [
+    node("root", {
+      position: "a0",
+      name: "Root",
+      icon: "📁",
+      hasChildren: true,
+      children: [node("child", { position: "a1", parentPageId: "root", name: "Child", icon: "📄" })],
+    }),
+  ];
+
+  // Build the UpdateEvent envelope; only `id`/`payload` matter to the reducer.
+  const ev = (id: string, payload: Record<string, unknown>) =>
+    ({
+      operation: "updateOne",
+      spaceId: "space-1",
+      entity: ["pages"],
+      id,
+      payload,
+    }) as unknown as Parameters<typeof applyUpdateOne>[1];
+
+  it("applies a title-only update to the node's name (icon untouched)", () => {
+    const tree = buildTree();
+    const next = applyUpdateOne(tree, ev("child", { title: "Renamed" }));
+    const child = treeModel.find(next, "child");
+    expect(child?.name).toBe("Renamed");
+    // Icon is left as it was.
+    expect(child?.icon).toBe("📄");
+  });
+
+  it("applies an icon-only update to the node's icon (name untouched)", () => {
+    const tree = buildTree();
+    const next = applyUpdateOne(tree, ev("root", { icon: "🔥" }));
+    const root = treeModel.find(next, "root");
+    expect(root?.icon).toBe("🔥");
+    expect(root?.name).toBe("Root");
+  });
+
+  it("applies a combined title + icon update", () => {
+    const tree = buildTree();
+    const next = applyUpdateOne(tree, ev("child", { title: "Both", icon: "⭐" }));
+    const child = treeModel.find(next, "child");
+    expect(child?.name).toBe("Both");
+    expect(child?.icon).toBe("⭐");
+  });
+
+  it("returns prev UNCHANGED (same reference) when the id is not loaded", () => {
+    const tree = buildTree();
+    const next = applyUpdateOne(tree, ev("ghost", { title: "Nope" }));
+    expect(next).toBe(tree);
+  });
+
+  it("returns prev UNCHANGED (same reference) for a no-op payload (no title/icon)", () => {
+    // The node exists, but the payload carries neither title nor icon -> nothing
+    // to patch, so the reducer must hand back the same array reference.
+    const tree = buildTree();
+    const next = applyUpdateOne(tree, ev("child", {}));
+    expect(next).toBe(tree);
+  });
+
+  it("treats an explicit null icon/title as a value to apply (undefined check, not truthiness)", () => {
+    // The reducer guards on `!== undefined`, so a clearing null IS applied.
+    const tree = buildTree();
+    const next = applyUpdateOne(tree, ev("child", { title: "", icon: null }));
+    const child = treeModel.find(next, "child");
+    expect(child?.name).toBe("");
+    expect(child?.icon).toBeNull();
+    // And it did change something -> a fresh reference, not prev.
+    expect(next).not.toBe(tree);
+  });
+});
diff --git a/apps/server/src/collaboration/yjs.util.spec.ts b/apps/server/src/collaboration/yjs.util.spec.ts
new file mode 100644
index 00000000..29511d6d
--- /dev/null
+++ b/apps/server/src/collaboration/yjs.util.spec.ts
@@ -0,0 +1,278 @@
+import * as Y from 'yjs';
+import { getSchema } from '@tiptap/core';
+import {
+  initProseMirrorDoc,
+  absolutePositionToRelativePosition,
+  prosemirrorJSONToYDoc,
+} from '@tiptap/y-tiptap';
+import { tiptapExtensions } from './collaboration.util';
+import {
+  setYjsMark,
+  removeYjsMarkByAttribute,
+  updateYjsMarkAttribute,
+  type YjsSelection,
+} from './yjs.util';
+
+/**
+ * Unit tests for the server-side Yjs mark helpers used by the collaboration
+ * handler to set/resolve/delete comment marks directly on the shared Y.Doc
+ * (collaboration.handler.ts: setCommentMark / resolveCommentMark).
+ *
+ * The fragment shape mirrors production exactly: a `default` XmlFragment whose
+ * children are block XmlElements (paragraph) holding XmlText runs. For setYjsMark
+ * the selection is a pair of Yjs RelativePosition JSONs (what the client sends);
+ * we synthesize them from known ProseMirror absolute positions via
+ * absolutePositionToRelativePosition so the marked range is deterministic.
+ */
+
+const schema = getSchema(tiptapExtensions);
+
+// Build a real Y.Doc from ProseMirror JSON (same path the collab handler uses
+// via TiptapTransformer) and return the doc + its `default` fragment.
+function buildFromPm(pmJson: unknown) {
+  const ydoc = prosemirrorJSONToYDoc(
+    schema,
+    pmJson as never,
+    'default',
+  ) as unknown as Y.Doc;
+  const fragment = ydoc.getXmlFragment('default');
+  return { ydoc, fragment };
+}
+
+// Make a YjsSelection (anchor/head RelativePosition JSON) for two ProseMirror
+// absolute positions in `fragment`.
+function selectionFor(
+  fragment: Y.XmlFragment,
+  anchorPos: number,
+  headPos: number,
+): YjsSelection {
+  const { mapping } = initProseMirrorDoc(fragment, schema);
+  const anchor = absolutePositionToRelativePosition(
+    anchorPos,
+    fragment as never,
+    mapping,
+  );
+  const head = absolutePositionToRelativePosition(
+    headPos,
+    fragment as never,
+    mapping,
+  );
+  return {
+    anchor: Y.relativePositionToJSON(anchor),
+    head: Y.relativePositionToJSON(head),
+  };
+}
+
+// The XmlText run of the i-th top-level paragraph.
+function paragraphText(fragment: Y.XmlFragment, index = 0): Y.XmlText {
+  const para = fragment.get(index) as Y.XmlElement;
+  return para.get(0) as Y.XmlText;
+}
+
+// --- raw fragment builder for the remove/update tests (no schema needed) ---
+//
+// removeYjsMarkByAttribute / updateYjsMarkAttribute only read item.toDelta() and
+// call item.format(); they never touch the ProseMirror schema. Build the runs
+// directly so we control which segment carries which comment attrs.
+function buildWithComments(
+  segments: Array<{
+    text: string;
+    comment?: { commentId: string; resolved: boolean };
+  }>,
+): { fragment: Y.XmlFragment; text: Y.XmlText } {
+  const ydoc = new Y.Doc();
+  const fragment = ydoc.getXmlFragment('default');
+  const para = new Y.XmlElement('paragraph');
+  fragment.insert(0, [para]);
+  const text = new Y.XmlText();
+  para.insert(0, [text]);
+  let offset = 0;
+  for (const seg of segments) {
+    text.insert(offset, seg.text);
+    if (seg.comment) {
+      text.format(offset, seg.text.length, { comment: seg.comment });
+    }
+    offset += seg.text.length;
+  }
+  return { fragment, text };
+}
+
+describe('setYjsMark', () => {
+  it('applies the mark over exactly the selected sub-range (PM pos 1..6 = "Hello")', () => {
+    const { ydoc, fragment } = buildFromPm({
+      type: 'doc',
+      content: [
+        { type: 'paragraph', content: [{ type: 'text', text: 'Hello world' }] },
+      ],
+    });
+    // PM pos 1 = start of the paragraph text; pos 6 = just after "Hello".
+    const sel = selectionFor(fragment, 1, 6);
+
+    setYjsMark(ydoc as never, fragment, sel, 'comment', {
+      commentId: 'c1',
+      resolved: false,
+    });
+
+    // The run splits: "Hello" carries the comment mark, " world" stays clean.
+    expect(paragraphText(fragment).toDelta()).toEqual([
+      {
+        insert: 'Hello',
+        attributes: { comment: { commentId: 'c1', resolved: false } },
+      },
+      { insert: ' world' },
+    ]);
+  });
+
+  it('normalizes a reversed selection (head before anchor) to the same range', () => {
+    const { ydoc, fragment } = buildFromPm({
+      type: 'doc',
+      content: [
+        { type: 'paragraph', content: [{ type: 'text', text: 'Hello world' }] },
+      ],
+    });
+    // anchor=6, head=1 — reversed; setYjsMark takes min/max so it marks "Hello".
+    const sel = selectionFor(fragment, 6, 1);
+
+    setYjsMark(ydoc as never, fragment, sel, 'comment', {
+      commentId: 'c2',
+      resolved: false,
+    });
+
+    expect(paragraphText(fragment).toDelta()).toEqual([
+      {
+        insert: 'Hello',
+        attributes: { comment: { commentId: 'c2', resolved: false } },
+      },
+      { insert: ' world' },
+    ]);
+  });
+
+  it('marks across two paragraphs (range spans an element boundary)', () => {
+    const { ydoc, fragment } = buildFromPm({
+      type: 'doc',
+      content: [
+        { type: 'paragraph', content: [{ type: 'text', text: 'aaa' }] },
+        { type: 'paragraph', content: [{ type: 'text', text: 'bbb' }] },
+      ],
+    });
+    // PM positions: "aaa" = 1..4; the </p><p> boundary consumes pos 4 and 5, so
+    // "bbb" starts at pos 6 (chars at 6,7,8). Select pos 2 (inside "aaa") to pos
+    // 8 (after the second "b").
+    const sel = selectionFor(fragment, 2, 8);
+
+    setYjsMark(ydoc as never, fragment, sel, 'comment', {
+      commentId: 'c3',
+      resolved: false,
+    });
+
+    // First paragraph: "a" clean, "aa" marked.
+    expect(paragraphText(fragment, 0).toDelta()).toEqual([
+      { insert: 'a' },
+      {
+        insert: 'aa',
+        attributes: { comment: { commentId: 'c3', resolved: false } },
+      },
+    ]);
+    // Second paragraph: "bb" marked, "b" clean.
+    expect(paragraphText(fragment, 1).toDelta()).toEqual([
+      {
+        insert: 'bb',
+        attributes: { comment: { commentId: 'c3', resolved: false } },
+      },
+      { insert: 'b' },
+    ]);
+  });
+});
+
+describe('removeYjsMarkByAttribute', () => {
+  it('removes only the run whose attribute value matches, leaving others', () => {
+    const { fragment, text } = buildWithComments([
+      { text: 'AAA', comment: { commentId: 'c1', resolved: false } },
+      { text: 'BBB', comment: { commentId: 'c2', resolved: false } },
+    ]);
+
+    removeYjsMarkByAttribute(fragment, 'comment', 'commentId', 'c1');
+
+    // c1's run loses the mark; c2's run is untouched.
+    expect(text.toDelta()).toEqual([
+      { insert: 'AAA' },
+      {
+        insert: 'BBB',
+        attributes: { comment: { commentId: 'c2', resolved: false } },
+      },
+    ]);
+  });
+
+  it('does nothing when no run carries the requested value (no-match branch)', () => {
+    const { fragment, text } = buildWithComments([
+      { text: 'AAA', comment: { commentId: 'c1', resolved: false } },
+    ]);
+    const before = text.toDelta();
+
+    removeYjsMarkByAttribute(fragment, 'comment', 'commentId', 'does-not-exist');
+
+    expect(text.toDelta()).toEqual(before);
+  });
+
+  it('leaves a different mark type alone', () => {
+    // A run carrying only `bold` must survive a comment removal pass.
+    const ydoc = new Y.Doc();
+    const fragment = ydoc.getXmlFragment('default');
+    const para = new Y.XmlElement('paragraph');
+    fragment.insert(0, [para]);
+    const text = new Y.XmlText();
+    para.insert(0, [text]);
+    text.insert(0, 'XYZ');
+    text.format(0, 3, { bold: true });
+
+    removeYjsMarkByAttribute(fragment, 'comment', 'commentId', 'c1');
+
+    expect(text.toDelta()).toEqual([
+      { insert: 'XYZ', attributes: { bold: true } },
+    ]);
+  });
+});
+
+describe('updateYjsMarkAttribute', () => {
+  it('merges new attributes into the matching run, preserving the rest', () => {
+    const { fragment, text } = buildWithComments([
+      { text: 'AAA', comment: { commentId: 'c1', resolved: false } },
+      { text: 'BBB', comment: { commentId: 'c2', resolved: false } },
+    ]);
+
+    updateYjsMarkAttribute(
+      fragment,
+      'comment',
+      { name: 'commentId', value: 'c1' },
+      { resolved: true },
+    );
+
+    // c1's run flips resolved=true (commentId preserved via merge); c2 untouched.
+    expect(text.toDelta()).toEqual([
+      {
+        insert: 'AAA',
+        attributes: { comment: { commentId: 'c1', resolved: true } },
+      },
+      {
+        insert: 'BBB',
+        attributes: { comment: { commentId: 'c2', resolved: false } },
+      },
+    ]);
+  });
+
+  it('does nothing when no run matches (no-match branch)', () => {
+    const { fragment, text } = buildWithComments([
+      { text: 'AAA', comment: { commentId: 'c1', resolved: false } },
+    ]);
+    const before = text.toDelta();
+
+    updateYjsMarkAttribute(
+      fragment,
+      'comment',
+      { name: 'commentId', value: 'nope' },
+      { resolved: true },
+    );
+
+    expect(text.toDelta()).toEqual(before);
+  });
+});
diff --git a/apps/server/src/core/ai-chat/external-mcp/mcp-clients.service.spec.ts b/apps/server/src/core/ai-chat/external-mcp/mcp-clients.service.spec.ts
new file mode 100644
index 00000000..53ad6191
--- /dev/null
+++ b/apps/server/src/core/ai-chat/external-mcp/mcp-clients.service.spec.ts
@@ -0,0 +1,166 @@
+import { McpClientsService } from './mcp-clients.service';
+
+/**
+ * Unit tests for the two security-critical surfaces of McpClientsService that the
+ * sibling specs (ssrf-guard / validate-resolved-addresses / lease) do NOT cover:
+ *
+ *  1. `decryptHeaders` (private) — FAIL-OPEN behavior. A decrypt/parse failure
+ *     (e.g. APP_SECRET rotated, tampered blob) must NEVER throw and must NEVER
+ *     log the blob: it returns `undefined` so the connect proceeds WITHOUT the
+ *     now-unreadable auth headers (which then 401s and the server is skipped),
+ *     rather than crashing the whole turn.
+ *
+ *  2. `this.guardedFetch` (private, bound to the SSRF-pinned dispatcher) — the
+ *     per-request DNS-rebinding guard. A blocked host (private/loopback/metadata
+ *     IP literal, or an unparseable URL) must REJECT before any socket is opened;
+ *     a public host is allowed through to the real `fetch` with the pinned
+ *     dispatcher attached.
+ *
+ * No network and no DB: the repo + secretBox deps are stubbed, and global `fetch`
+ * is mocked for the single allow-path assertion.
+ */
+
+// Build the service with a SecretBoxService stub whose decryptSecret is supplied
+// per-test. The repo dep is unused by the methods under test.
+function buildService(decryptSecret: (blob: string) => string) {
+  const secretBox = { decryptSecret: jest.fn(decryptSecret) };
+  const service = new McpClientsService({} as never, secretBox as never);
+  return { service, secretBox };
+}
+
+describe('McpClientsService.decryptHeaders', () => {
+  // Reach the private method via the as-any pattern common in these NestJS specs.
+  const callDecrypt = (
+    service: McpClientsService,
+    blob: string | null,
+  ): Record<string, string> | undefined =>
+    (
+      service as unknown as {
+        decryptHeaders: (b: string | null) => Record<string, string> | undefined;
+      }
+    ).decryptHeaders(blob);
+
+  it('returns undefined for a null blob without decrypting', () => {
+    const { service, secretBox } = buildService(() => '{}');
+    expect(callDecrypt(service, null)).toBeUndefined();
+    expect(secretBox.decryptSecret).not.toHaveBeenCalled();
+  });
+
+  it('decrypts a valid blob and keeps only string-valued headers', () => {
+    const { service } = buildService(() =>
+      JSON.stringify({
+        Authorization: 'Bearer abc',
+        'X-Api-Key': 'k',
+        // Non-string values must be dropped, not coerced.
+        count: 5,
+        flag: true,
+        nested: { a: 1 },
+      }),
+    );
+    expect(callDecrypt(service, 'cipher')).toEqual({
+      Authorization: 'Bearer abc',
+      'X-Api-Key': 'k',
+    });
+  });
+
+  it('returns undefined when the decrypted object has no string headers', () => {
+    const { service } = buildService(() => JSON.stringify({ count: 5 }));
+    // No usable headers -> undefined (connect with no auth header), not {}.
+    expect(callDecrypt(service, 'cipher')).toBeUndefined();
+  });
+
+  it('FAILS OPEN: a decrypt error returns undefined instead of throwing', () => {
+    const { service } = buildService(() => {
+      throw new Error('Failed to decrypt secret — APP_SECRET may have changed');
+    });
+    const warnSpy = jest
+      .spyOn(
+        (service as unknown as { logger: { warn: (...a: unknown[]) => void } })
+          .logger,
+        'warn',
+      )
+      .mockImplementation(() => undefined);
+
+    let result: unknown;
+    expect(() => {
+      result = callDecrypt(service, 'tampered-blob');
+    }).not.toThrow();
+    expect(result).toBeUndefined();
+    // It warns (so ops sees degradation) but never logs the blob itself.
+    expect(warnSpy).toHaveBeenCalledTimes(1);
+    expect(String(warnSpy.mock.calls[0]?.[0])).not.toContain('tampered-blob');
+  });
+
+  it('FAILS OPEN: malformed JSON (decrypts to non-JSON) returns undefined', () => {
+    const { service } = buildService(() => 'not-json{');
+    jest
+      .spyOn(
+        (service as unknown as { logger: { warn: (...a: unknown[]) => void } })
+          .logger,
+        'warn',
+      )
+      .mockImplementation(() => undefined);
+    expect(callDecrypt(service, 'cipher')).toBeUndefined();
+  });
+});
+
+describe('McpClientsService.guardedFetch (SSRF per-request guard)', () => {
+  // The bound guardedFetch closure lives on the instance as a private field.
+  const guardedFetchOf = (service: McpClientsService) =>
+    (service as unknown as { guardedFetch: typeof fetch }).guardedFetch;
+
+  let fetchSpy: jest.SpiedFunction<typeof fetch>;
+
+  beforeEach(() => {
+    // Any reachable real fetch would be a network call; assert per-test that the
+    // blocked paths never reach it, and stub a Response for the allow path.
+    fetchSpy = jest
+      .spyOn(global, 'fetch')
+      .mockResolvedValue(new Response('ok', { status: 200 }));
+  });
+
+  afterEach(() => {
+    jest.restoreAllMocks();
+  });
+
+  const blocked: Array<[string, string]> = [
+    ['loopback IPv4', 'http://127.0.0.1/mcp'],
+    ['private 10/8', 'http://10.0.0.5/mcp'],
+    ['private 192.168/16', 'http://192.168.1.1/mcp'],
+    ['cloud metadata link-local', 'http://169.254.169.254/latest/meta-data/'],
+    ['loopback IPv6 (bracketed)', 'http://[::1]:8080/mcp'],
+  ];
+
+  it.each(blocked)(
+    'rejects a request to %s without opening a socket',
+    async (_label, url) => {
+      const { service } = buildService(() => '{}');
+      await expect(guardedFetchOf(service)(url)).rejects.toThrow(
+        /blocked request/,
+      );
+      expect(fetchSpy).not.toHaveBeenCalled();
+    },
+  );
+
+  it('rejects an unparseable URL as a blocked request', async () => {
+    const { service } = buildService(() => '{}');
+    await expect(
+      guardedFetchOf(service)('::: not a url :::'),
+    ).rejects.toThrow('blocked request: invalid URL');
+    expect(fetchSpy).not.toHaveBeenCalled();
+  });
+
+  it('allows a public IP literal and forwards through the pinned dispatcher', async () => {
+    const { service } = buildService(() => '{}');
+    const res = await guardedFetchOf(service)('http://8.8.8.8/mcp');
+
+    expect(res.status).toBe(200);
+    expect(fetchSpy).toHaveBeenCalledTimes(1);
+    // The init MUST carry the SSRF-pinned undici dispatcher (the rebinding pin);
+    // dropping it would let undici do a second, unchecked DNS resolution.
+    const init = fetchSpy.mock.calls[0][1] as RequestInit & {
+      dispatcher?: unknown;
+    };
+    expect(init.dispatcher).toBeDefined();
+  });
+});
diff --git a/apps/server/src/core/ai-chat/tools/shared-tool-specs.contract.spec.ts b/apps/server/src/core/ai-chat/tools/shared-tool-specs.contract.spec.ts
new file mode 100644
index 00000000..31461717
--- /dev/null
+++ b/apps/server/src/core/ai-chat/tools/shared-tool-specs.contract.spec.ts
@@ -0,0 +1,124 @@
+import { z } from 'zod';
+import { AiChatToolsService } from './ai-chat-tools.service';
+import * as loader from './docmost-client.loader';
+import type { DocmostClientLike } from './docmost-client.loader';
+// The real zod-agnostic registry, imported from source so the contract is checked
+// against exactly what the @docmost/mcp package ships (no hand-stub).
+import { SHARED_TOOL_SPECS } from '../../../../../../packages/mcp/src/tool-specs';
+
+/**
+ * CONTRACT: SHARED_TOOL_SPECS <-> in-app tool wiring parity.
+ *
+ * `packages/mcp/src/tool-specs.ts` is the single source of truth for the tools
+ * that are intentionally IDENTICAL across the standalone MCP server (zod v3) and
+ * the in-app AI-SDK service (zod v4). The in-app service builds each one via
+ * `sharedTool(sharedToolSpecs.<key>, execute)`, keyed by the spec's `inAppKey`.
+ *
+ * This test fails the build if a spec is added to the registry but never wired
+ * in-app, if an `inAppKey` is renamed without updating the service, if the
+ * description drifts between the registry and the exposed tool, if the
+ * snake_case `mcpName` <-> camelCase `inAppKey` convention is broken, or if the
+ * exposed tool's input-schema keys diverge from the spec's `buildShape`.
+ *
+ * It does NOT need @docmost/mcp built: the registry is imported from TS source,
+ * and the ESM loader is mocked so `forUser()` never dynamically imports the
+ * package.
+ */
+describe('SHARED_TOOL_SPECS contract parity', () => {
+  // Empty fake client: no tool is executed here — every assertion is on tool
+  // presence / metadata / schema, so the client methods are never called.
+  const fakeClient: Partial<DocmostClientLike> = {};
+  const tokenServiceStub = {
+    generateAccessToken: jest.fn().mockResolvedValue('access-token'),
+    generateCollabToken: jest.fn().mockResolvedValue('collab-token'),
+  };
+
+  let tools: Record<string, unknown>;
+
+  beforeAll(async () => {
+    jest.spyOn(loader, 'loadDocmostMcp').mockResolvedValue({
+      DocmostClient: function () {
+        return fakeClient as DocmostClientLike;
+      } as unknown as loader.DocmostClientCtor,
+      // Feed the service the SAME registry this test asserts against.
+      sharedToolSpecs: SHARED_TOOL_SPECS as unknown as Record<
+        string,
+        loader.SharedToolSpec
+      >,
+    });
+    const service = new AiChatToolsService(
+      tokenServiceStub as never,
+      {} as never,
+      {} as never,
+      {} as never,
+      {} as never,
+      { asSink: () => ({ put: jest.fn(), has: jest.fn(), evict: jest.fn() }) } as never,
+    );
+    tools = (await service.forUser(
+      { id: 'user-1', email: 'u@example.com', workspaceId: 'ws-1' } as never,
+      'session-1',
+      'ws-1',
+      'chat-1',
+    )) as unknown as Record<string, unknown>;
+  });
+
+  afterAll(() => jest.restoreAllMocks());
+
+  // camelCase -> snake_case, matching the registry's mcpName convention.
+  const toSnake = (s: string) =>
+    s.replace(/[A-Z]/g, (c) => `_${c.toLowerCase()}`);
+
+  // Type as the (optional-buildShape) SharedToolSpec; the `satisfies` literal
+  // above otherwise narrows to a union where some members lack buildShape.
+  const specEntries = Object.entries(SHARED_TOOL_SPECS) as Array<
+    [string, loader.SharedToolSpec]
+  >;
+
+  // Sanity: the registry is non-empty, so the per-spec table below is not vacuous.
+  it('registry is non-empty', () => {
+    expect(specEntries.length).toBeGreaterThan(0);
+  });
+
+  describe.each(specEntries)('spec "%s"', (registryKey, spec) => {
+    it('registry key equals its inAppKey', () => {
+      // The service indexes the registry by property name; a key != inAppKey
+      // would wire the wrong (or no) tool.
+      expect(spec.inAppKey).toBe(registryKey);
+    });
+
+    it('mcpName is the snake_case form of inAppKey', () => {
+      expect(spec.mcpName).toBe(toSnake(spec.inAppKey));
+    });
+
+    it('is exposed in-app under its inAppKey', () => {
+      // Fails if a spec is added to the registry but never wired in forUser().
+      expect(tools[spec.inAppKey]).toBeDefined();
+    });
+
+    it("exposed tool's description matches the registry description", () => {
+      const tool = tools[spec.inAppKey] as { description: string };
+      expect(tool.description).toBe(spec.description);
+    });
+
+    it("exposed tool's input-schema keys match buildShape (incl. required)", () => {
+      const tool = tools[spec.inAppKey] as {
+        inputSchema: { jsonSchema: { properties?: Record<string, unknown>; required?: string[] } };
+      };
+      const json = tool.inputSchema.jsonSchema;
+      const actualKeys = Object.keys(json.properties ?? {}).sort();
+
+      // Derive the spec's declared shape with THIS layer's zod (v4) — the same
+      // call the service makes — then compare key sets and required-ness.
+      const shape = spec.buildShape ? spec.buildShape(z) : {};
+      const expectedKeys = Object.keys(shape).sort();
+      expect(actualKeys).toEqual(expectedKeys);
+
+      // A non-.optional() field must surface as required in the advertised schema.
+      const expectedRequired = Object.entries(shape)
+        .filter(([, field]) => !(field as z.ZodTypeAny).isOptional?.())
+        .map(([k]) => k)
+        .sort();
+      expect((json.required ?? []).slice().sort()).toEqual(expectedRequired);
+    });
+  });
+});
diff --git a/apps/server/src/integrations/storage/storage.service.spec.ts b/apps/server/src/integrations/storage/storage.service.spec.ts
index 79db48c0..fc80246e 100644
--- a/apps/server/src/integrations/storage/storage.service.spec.ts
+++ b/apps/server/src/integrations/storage/storage.service.spec.ts
@@ -1,18 +1,110 @@
+import { Readable } from 'stream';
 import { StorageService } from './storage.service';
+import type { StorageDriver } from './interfaces';
 
-// Direct instantiation with a stub driver. The Test.createTestingModule form
-// failed to resolve the STORAGE_DRIVER_TOKEN at compile(); this smoke test only
-// needs the service to construct.
-describe('StorageService', () => {
+/**
+ * StorageService is a thin facade over the injected StorageDriver: each public
+ * method must forward to the driver with the SAME arguments and return/await the
+ * driver's result unchanged (the read paths return it; the write paths await it).
+ * A mock driver lets us assert that delegation exactly, with no real S3/disk IO.
+ */
+describe('StorageService delegation', () => {
+  // Every driver method is a jest mock so we can assert call args + return passing.
+  function buildDriver(): jest.Mocked<StorageDriver> {
+    return {
+      upload: jest.fn().mockResolvedValue(undefined),
+      uploadStream: jest.fn().mockResolvedValue(undefined),
+      copy: jest.fn().mockResolvedValue(undefined),
+      read: jest.fn(),
+      readStream: jest.fn(),
+      readRangeStream: jest.fn(),
+      exists: jest.fn(),
+      getUrl: jest.fn(),
+      getSignedUrl: jest.fn(),
+      delete: jest.fn().mockResolvedValue(undefined),
+      getDriver: jest.fn(),
+      getDriverName: jest.fn(),
+      getConfig: jest.fn(),
+    } as unknown as jest.Mocked<StorageDriver>;
+  }
+
+  let driver: jest.Mocked<StorageDriver>;
   let service: StorageService;
 
   beforeEach(() => {
-    service = new StorageService(
-      {} as any, // storageDriver
-    );
+    driver = buildDriver();
+    service = new StorageService(driver as unknown as StorageDriver);
   });
 
-  it('should be defined', () => {
-    expect(service).toBeDefined();
+  it('upload forwards path + content to the driver', async () => {
+    const buf = Buffer.from('data');
+    await service.upload('a/b.png', buf);
+    expect(driver.upload).toHaveBeenCalledWith('a/b.png', buf);
+  });
+
+  it('uploadStream forwards path, stream and options', async () => {
+    const stream = Readable.from(['x']);
+    await service.uploadStream('a/b.bin', stream, { recreateClient: true });
+    expect(driver.uploadStream).toHaveBeenCalledWith('a/b.bin', stream, {
+      recreateClient: true,
+    });
+  });
+
+  it('copy forwards both paths', async () => {
+    await service.copy('from.txt', 'to.txt');
+    expect(driver.copy).toHaveBeenCalledWith('from.txt', 'to.txt');
+  });
+
+  it('read returns the driver buffer unchanged', async () => {
+    const buf = Buffer.from('content');
+    driver.read.mockResolvedValue(buf);
+    await expect(service.read('f.txt')).resolves.toBe(buf);
+    expect(driver.read).toHaveBeenCalledWith('f.txt');
+  });
+
+  it('readStream returns the driver stream unchanged', async () => {
+    const stream = Readable.from(['y']);
+    driver.readStream.mockResolvedValue(stream);
+    await expect(service.readStream('f.bin')).resolves.toBe(stream);
+    expect(driver.readStream).toHaveBeenCalledWith('f.bin');
+  });
+
+  it('readRangeStream forwards the range object and returns the stream', async () => {
+    const stream = Readable.from(['z']);
+    driver.readRangeStream.mockResolvedValue(stream);
+    const range = { start: 0, end: 99 };
+    await expect(service.readRangeStream('f.bin', range)).resolves.toBe(stream);
+    expect(driver.readRangeStream).toHaveBeenCalledWith('f.bin', range);
+  });
+
+  it('exists returns the driver boolean', async () => {
+    driver.exists.mockResolvedValue(false);
+    await expect(service.exists('missing')).resolves.toBe(false);
+    expect(driver.exists).toHaveBeenCalledWith('missing');
+  });
+
+  it('getSignedUrl forwards path + expiry and returns the signed url', async () => {
+    driver.getSignedUrl.mockResolvedValue('https://signed/url');
+    await expect(service.getSignedUrl('f.png', 600)).resolves.toBe(
+      'https://signed/url',
+    );
+    expect(driver.getSignedUrl).toHaveBeenCalledWith('f.png', 600);
+  });
+
+  it('getUrl returns the driver url synchronously', () => {
+    driver.getUrl.mockReturnValue('https://cdn/f.png');
+    expect(service.getUrl('f.png')).toBe('https://cdn/f.png');
+    expect(driver.getUrl).toHaveBeenCalledWith('f.png');
+  });
+
+  it('delete forwards the path', async () => {
+    await service.delete('old.txt');
+    expect(driver.delete).toHaveBeenCalledWith('old.txt');
+  });
+
+  it('getDriverName returns the driver name', () => {
+    driver.getDriverName.mockReturnValue('s3');
+    expect(service.getDriverName()).toBe('s3');
+    expect(driver.getDriverName).toHaveBeenCalledTimes(1);
   });
 });
diff --git a/packages/editor-ext/src/lib/recreate-transform/recreateTransform.test.ts b/packages/editor-ext/src/lib/recreate-transform/recreateTransform.test.ts
new file mode 100644
index 00000000..a30dc3d2
--- /dev/null
+++ b/packages/editor-ext/src/lib/recreate-transform/recreateTransform.test.ts
@@ -0,0 +1,133 @@
+import { describe, it, expect } from "vitest";
+import { schema } from "@tiptap/pm/schema-basic";
+import type { Node as PMNode } from "@tiptap/pm/model";
+import { Transform } from "@tiptap/pm/transform";
+import { recreateTransform } from "./recreateTransform";
+
+/**
+ * recreateTransform diffs two documents and produces ProseMirror steps that turn
+ * `fromDoc` into `toDoc`. It is the backbone of collaborative/version diffing, so
+ * THE invariant that matters is: replaying the produced steps on `fromDoc` must
+ * reproduce `toDoc` exactly. Every test below re-applies the steps onto a fresh
+ * Transform seeded from `fromDoc` (not just trusting `tr.doc`) and asserts node
+ * equality with `.eq()`. If a regression makes any step wrong, the round-trip
+ * breaks and the test fails.
+ */
+
+// Real ProseMirror schema (the standard basic schema) with paragraph/heading +
+// strong/em marks — the same primitives the editor diffs in production.
+const doc = (...c: PMNode[]) => schema.node("doc", null, c);
+const p = (...c: PMNode[]) =>
+  schema.node("paragraph", null, c.length ? c : undefined);
+const h = (level: number, ...c: PMNode[]) =>
+  schema.node("heading", { level }, c);
+const t = (text: string, ...marks: any[]) =>
+  schema.text(text, marks.length ? marks : undefined);
+const strong = schema.marks.strong.create();
+const em = schema.marks.em.create();
+
+// Replay the diff's steps onto a fresh Transform built from `fromDoc`. This is
+// the faithful "apply(diff) == target" check — it exercises the actual Step
+// objects rather than the transform's internal accumulated doc.
+function applyDiff(fromDoc: PMNode, toDoc: PMNode, options?: any): PMNode {
+  const tr = recreateTransform(fromDoc, toDoc, options);
+  const replay = new Transform(fromDoc);
+  tr.steps.forEach((s) => {
+    const result = replay.maybeStep(s);
+    if (result.failed) throw new Error(`step failed: ${result.failed}`);
+  });
+  return replay.doc;
+}
+
+describe("recreateTransform round-trip (apply(diff) == target)", () => {
+  it("reconstructs the target on plain text insertion", () => {
+    // Inserting " world" must yield exactly the target paragraph.
+    const from = doc(p(t("hello")));
+    const to = doc(p(t("hello world")));
+    expect(applyDiff(from, to).eq(to)).toBe(true);
+  });
+
+  it("reconstructs the target on text deletion", () => {
+    // Deleting a trailing word is the inverse of insertion and must round-trip.
+    const from = doc(p(t("hello world")));
+    const to = doc(p(t("hello")));
+    expect(applyDiff(from, to).eq(to)).toBe(true);
+  });
+
+  it("reconstructs the target when a word is replaced mid-string", () => {
+    // A char-level replace in the middle must not corrupt the surrounding text.
+    const from = doc(p(t("the quick brown fox")));
+    const to = doc(p(t("the slow brown fox")));
+    expect(applyDiff(from, to).eq(to)).toBe(true);
+  });
+
+  it("reconstructs the target when a mark is added (complexSteps path)", () => {
+    // Mark-only changes are diffed in a separate pass; the bolded run must match.
+    const from = doc(p(t("hello")));
+    const to = doc(p(t("hello", strong)));
+    const out = applyDiff(from, to);
+    expect(out.eq(to)).toBe(true);
+    // Sanity: the produced doc actually carries the strong mark.
+    expect(out.firstChild!.firstChild!.marks.length).toBe(1);
+  });
+
+  it("reconstructs the target when a mark is removed", () => {
+    // Removing the only mark must leave the same text with no marks.
+    const from = doc(p(t("hello", strong)));
+    const to = doc(p(t("hello")));
+    const out = applyDiff(from, to);
+    expect(out.eq(to)).toBe(true);
+    expect(out.firstChild!.firstChild!.marks.length).toBe(0);
+  });
+
+  it("reconstructs the target on a paragraph split into two blocks", () => {
+    // Structural change (one block -> two) must replay as valid replace steps.
+    const from = doc(p(t("hello world")));
+    const to = doc(p(t("hello")), p(t("world")));
+    const out = applyDiff(from, to);
+    expect(out.eq(to)).toBe(true);
+    expect(out.childCount).toBe(2);
+  });
+
+  it("reconstructs the target on a node-type change (paragraph -> heading)", () => {
+    // Type/attrs changes drive the setNodeMarkup branch; the node must become a
+    // heading while keeping its text.
+    const from = doc(p(t("hello")));
+    const to = doc(h(1, t("hello")));
+    const out = applyDiff(from, to);
+    expect(out.eq(to)).toBe(true);
+    expect(out.firstChild!.type.name).toBe("heading");
+  });
+
+  it("reconstructs a combined structural + mark change", () => {
+    // Several diff kinds at once (new block + italic run) still round-trips.
+    const from = doc(p(t("alpha")));
+    const to = doc(p(t("alpha")), p(t("beta", em)));
+    const out = applyDiff(from, to);
+    expect(out.eq(to)).toBe(true);
+  });
+
+  it("produces an empty step list for identical documents", () => {
+    // No diff => no work; spurious steps would mean wasted/incorrect history.
+    const from = doc(p(t("same")));
+    const to = doc(p(t("same")));
+    const tr = recreateTransform(from, to);
+    expect(tr.steps.length).toBe(0);
+    expect(tr.doc.eq(to)).toBe(true);
+  });
+
+  it("round-trips with complexSteps:false (marks diffed as replaces)", () => {
+    // With complexSteps off, mark changes are folded into replace steps rather
+    // than dedicated mark steps — the result must still equal the target.
+    const from = doc(p(t("hello")));
+    const to = doc(p(t("hello", strong)));
+    expect(applyDiff(from, to, { complexSteps: false }).eq(to)).toBe(true);
+  });
+
+  it("round-trips with wordDiffs:true (whole-word text diffing)", () => {
+    // wordDiffs changes the granularity of the text diff, not the outcome.
+    const from = doc(p(t("the quick brown fox")));
+    const to = doc(p(t("the quick red fox")));
+    expect(applyDiff(from, to, { wordDiffs: true }).eq(to)).toBe(true);
+  });
+});
diff --git a/packages/editor-ext/src/lib/table/utils/get-selection-range-in-column.test.ts b/packages/editor-ext/src/lib/table/utils/get-selection-range-in-column.test.ts
new file mode 100644
index 00000000..7e623c60
--- /dev/null
+++ b/packages/editor-ext/src/lib/table/utils/get-selection-range-in-column.test.ts
@@ -0,0 +1,108 @@
+import { describe, it, expect } from "vitest";
+import { Schema } from "@tiptap/pm/model";
+import type { Node as PMNode } from "@tiptap/pm/model";
+import { tableNodes } from "@tiptap/pm/tables";
+import { EditorState, Selection } from "@tiptap/pm/state";
+import { getSelectionRangeInColumn } from "./get-selection-range-in-column";
+
+/**
+ * getSelectionRangeInColumn computes the rectangular column range (the set of
+ * column indexes, plus anchor/head cell positions) that a drag-reorder or
+ * column-select operation should act on, accounting for merged (colspan) cells.
+ * It keys off the table found from the current selection, so we drive it with a
+ * real EditorState whose selection sits inside the table.
+ */
+
+// Real ProseMirror table schema (same primitives the editor uses) so TableMap /
+// cellsInRect behave exactly as in production.
+const tNodes = tableNodes({
+  tableGroup: "block",
+  cellContent: "inline*",
+  cellAttributes: {},
+});
+const schema = new Schema({
+  nodes: {
+    doc: { content: "block+" },
+    paragraph: { group: "block", content: "inline*", toDOM: () => ["p", 0] },
+    text: { group: "inline" },
+    ...tNodes,
+  },
+  marks: {},
+});
+const cell = (txt: string, attrs?: Record<string, unknown>): PMNode =>
+  schema.nodes.table_cell.createChecked(attrs ?? null, schema.text(txt));
+const row = (...cells: PMNode[]): PMNode =>
+  schema.nodes.table_row.createChecked(null, cells);
+const table = (...rows: PMNode[]): PMNode =>
+  schema.nodes.table.createChecked(null, rows);
+const doc = (...content: PMNode[]): PMNode =>
+  schema.nodes.doc.createChecked(null, content);
+
+// Build a transaction whose selection is inside the table (the function locates
+// the table via `tr.selection.$from`).
+const trFor = (d: PMNode) =>
+  EditorState.create({ doc: d, selection: Selection.atStart(d) }).tr;
+
+// A 2-row x 3-col grid; each column is identifiable by its top-row letter.
+const grid3x2 = () =>
+  doc(
+    table(
+      row(cell("a"), cell("b"), cell("c")),
+      row(cell("d"), cell("e"), cell("f")),
+    ),
+  );
+
+describe("getSelectionRangeInColumn", () => {
+  it("returns a single-column range for a single index", () => {
+    // Asking for column 1 yields exactly indexes [1].
+    const tr = trFor(grid3x2());
+    const range = getSelectionRangeInColumn(tr, 1);
+    expect(range).toBeTruthy();
+    expect(range!.indexes).toEqual([1]);
+  });
+
+  it("anchor/head resolve to the top and bottom cells OF the requested column", () => {
+    // $head must point at the column's first (top) cell and $anchor at its last
+    // (bottom) cell — pinning that the returned positions belong to column 1,
+    // not some other column.
+    const tr = trFor(grid3x2());
+    const range = getSelectionRangeInColumn(tr, 1)!;
+    expect(tr.doc.nodeAt(range.$head.pos)?.textContent).toBe("b"); // top of col 1
+    expect(tr.doc.nodeAt(range.$anchor.pos)?.textContent).toBe("e"); // bottom of col 1
+  });
+
+  it("returns the inclusive span of columns for a multi-column request", () => {
+    // A 0..2 request must enumerate every covered column, in order.
+    const tr = trFor(grid3x2());
+    const range = getSelectionRangeInColumn(tr, 0, 2);
+    expect(range!.indexes).toEqual([0, 1, 2]);
+  });
+
+  it("returns a two-column span for an adjacent pair", () => {
+    const tr = trFor(grid3x2());
+    const range = getSelectionRangeInColumn(tr, 1, 2);
+    expect(range!.indexes).toEqual([1, 2]);
+  });
+
+  it("expands the range to cover a horizontally merged (colspan) cell", () => {
+    // Row 0 col 0 spans 2 columns. Requesting just column 0 must pull column 1
+    // into the range because they are merged together in the top row.
+    const d = doc(
+      table(
+        row(cell("ab", { colspan: 2 }), cell("c")),
+        row(cell("d"), cell("e"), cell("f")),
+      ),
+    );
+    const tr = trFor(d);
+    const range = getSelectionRangeInColumn(tr, 0);
+    expect(range!.indexes).toEqual([0, 1]);
+  });
+
+  it("throws when the requested column is entirely out of range", () => {
+    // No cells exist at column 5 of a 3-wide table, so the function cannot pick
+    // an anchor cell and dereferences undefined — pin this as the current
+    // (caller-guarded) contract so a silent behavior change is caught.
+    const tr = trFor(grid3x2());
+    expect(() => getSelectionRangeInColumn(tr, 5)).toThrow();
+  });
+});
diff --git a/packages/editor-ext/src/lib/table/utils/move-column.test.ts b/packages/editor-ext/src/lib/table/utils/move-column.test.ts
new file mode 100644
index 00000000..5b2d60e5
--- /dev/null
+++ b/packages/editor-ext/src/lib/table/utils/move-column.test.ts
@@ -0,0 +1,156 @@
+import { describe, it, expect } from "vitest";
+import { Schema } from "@tiptap/pm/model";
+import type { Node as PMNode } from "@tiptap/pm/model";
+import { tableNodes, CellSelection } from "@tiptap/pm/tables";
+import { EditorState, Selection } from "@tiptap/pm/state";
+import { moveColumn } from "./move-column";
+import { convertTableNodeToArrayOfRows } from "./convert-table-node-to-array-of-rows";
+import { findTable } from "./query";
+
+/**
+ * moveColumn reorders whole columns of a real ProseMirror table by mutating a
+ * Transaction (transpose -> move row -> transpose back -> replace). The invariant
+ * is that after the call each column appears at its new position with every
+ * cell's content preserved and nothing dropped or duplicated.
+ */
+
+const tNodes = tableNodes({
+  tableGroup: "block",
+  cellContent: "inline*",
+  cellAttributes: {},
+});
+const schema = new Schema({
+  nodes: {
+    doc: { content: "block+" },
+    paragraph: { group: "block", content: "inline*", toDOM: () => ["p", 0] },
+    text: { group: "inline" },
+    ...tNodes,
+  },
+  marks: {},
+});
+const cell = (txt: string): PMNode =>
+  schema.nodes.table_cell.createChecked(null, schema.text(txt));
+const row = (...cells: PMNode[]): PMNode =>
+  schema.nodes.table_row.createChecked(null, cells);
+const table = (...rows: PMNode[]): PMNode =>
+  schema.nodes.table.createChecked(null, rows);
+const doc = (...content: PMNode[]): PMNode =>
+  schema.nodes.doc.createChecked(null, content);
+
+const grid = (tr: any): string[][] => {
+  const t = findTable(tr.doc.resolve(tr.selection.from))!;
+  return convertTableNodeToArrayOfRows(t.node).map((r) =>
+    r.map((c) => (c ? c.textContent : "")),
+  );
+};
+
+// 2-row x 3-col table; column k is (rowX-col-k). Columns: 0=(a,d) 1=(b,e) 2=(c,f).
+const grid3x2 = () =>
+  doc(
+    table(
+      row(cell("a"), cell("b"), cell("c")),
+      row(cell("d"), cell("e"), cell("f")),
+    ),
+  );
+
+const stateFor = (d: PMNode) =>
+  EditorState.create({ doc: d, selection: Selection.atStart(d) });
+
+describe("moveColumn", () => {
+  it("moves the first column to the last index, preserving column content", () => {
+    // origin 0 -> target 2 sends column (a,d) to the right: cols become 1,2,0.
+    const state = stateFor(grid3x2());
+    const tr = state.tr;
+    const ok = moveColumn({
+      tr,
+      originIndex: 0,
+      targetIndex: 2,
+      select: false,
+      pos: state.selection.from,
+    });
+    expect(ok).toBe(true);
+    expect(grid(tr)).toEqual([
+      ["b", "c", "a"],
+      ["e", "f", "d"],
+    ]);
+  });
+
+  it("moves a later column to the first index", () => {
+    // origin 2 -> target 0 pulls column (c,f) to the front: cols become 2,0,1.
+    const state = stateFor(grid3x2());
+    const tr = state.tr;
+    const ok = moveColumn({
+      tr,
+      originIndex: 2,
+      targetIndex: 0,
+      select: false,
+      pos: state.selection.from,
+    });
+    expect(ok).toBe(true);
+    expect(grid(tr)).toEqual([
+      ["c", "a", "b"],
+      ["f", "d", "e"],
+    ]);
+  });
+
+  it("never drops or duplicates cells when reordering columns", () => {
+    const state = stateFor(grid3x2());
+    const tr = state.tr;
+    moveColumn({
+      tr,
+      originIndex: 1,
+      targetIndex: 2,
+      select: false,
+      pos: state.selection.from,
+    });
+    expect(grid(tr).flat().sort()).toEqual(
+      ["a", "b", "c", "d", "e", "f"].sort(),
+    );
+    expect(grid(tr)[0].length).toBe(3);
+  });
+
+  it("returns false (no-op) when target equals origin", () => {
+    const state = stateFor(grid3x2());
+    const tr = state.tr;
+    const before = grid(tr);
+    const ok = moveColumn({
+      tr,
+      originIndex: 1,
+      targetIndex: 1,
+      select: false,
+      pos: state.selection.from,
+    });
+    expect(ok).toBe(false);
+    expect(grid(tr)).toEqual(before);
+  });
+
+  it("returns false when pos is not inside a table", () => {
+    const d = doc(
+      schema.nodes.paragraph.createChecked(null, schema.text("plain")),
+    );
+    const state = stateFor(d);
+    const tr = state.tr;
+    const ok = moveColumn({
+      tr,
+      originIndex: 0,
+      targetIndex: 1,
+      select: false,
+      pos: state.selection.from,
+    });
+    expect(ok).toBe(false);
+  });
+
+  it("installs a CellSelection on the moved column when select is true", () => {
+    const state = stateFor(grid3x2());
+    const tr = state.tr;
+    const ok = moveColumn({
+      tr,
+      originIndex: 0,
+      targetIndex: 2,
+      select: true,
+      pos: state.selection.from,
+    });
+    expect(ok).toBe(true);
+    expect(tr.selection instanceof CellSelection).toBe(true);
+  });
+});
diff --git a/packages/editor-ext/src/lib/table/utils/move-row.test.ts b/packages/editor-ext/src/lib/table/utils/move-row.test.ts
new file mode 100644
index 00000000..3a0c481a
--- /dev/null
+++ b/packages/editor-ext/src/lib/table/utils/move-row.test.ts
@@ -0,0 +1,167 @@
+import { describe, it, expect } from "vitest";
+import { Schema } from "@tiptap/pm/model";
+import type { Node as PMNode } from "@tiptap/pm/model";
+import { tableNodes, CellSelection } from "@tiptap/pm/tables";
+import { EditorState, Selection } from "@tiptap/pm/state";
+import { moveRow } from "./move-row";
+import { convertTableNodeToArrayOfRows } from "./convert-table-node-to-array-of-rows";
+import { findTable } from "./query";
+
+/**
+ * moveRow reorders whole rows of a real ProseMirror table by mutating a
+ * Transaction: it locates the table, computes origin/target row ranges, rebuilds
+ * the table with rows reordered, and replaces it in the doc. The invariant is
+ * that after the call the table's rows appear in the new order with every cell's
+ * content preserved, and no rows are dropped or duplicated.
+ */
+
+const tNodes = tableNodes({
+  tableGroup: "block",
+  cellContent: "inline*",
+  cellAttributes: {},
+});
+const schema = new Schema({
+  nodes: {
+    doc: { content: "block+" },
+    paragraph: { group: "block", content: "inline*", toDOM: () => ["p", 0] },
+    text: { group: "inline" },
+    ...tNodes,
+  },
+  marks: {},
+});
+const cell = (txt: string): PMNode =>
+  schema.nodes.table_cell.createChecked(null, schema.text(txt));
+const row = (...cells: PMNode[]): PMNode =>
+  schema.nodes.table_row.createChecked(null, cells);
+const table = (...rows: PMNode[]): PMNode =>
+  schema.nodes.table.createChecked(null, rows);
+const doc = (...content: PMNode[]): PMNode =>
+  schema.nodes.doc.createChecked(null, content);
+
+// Read the table's content as a grid of cell texts (rows x cols) from whatever
+// table currently lives in `tr.doc`.
+const grid = (tr: any): string[][] => {
+  const t = findTable(tr.doc.resolve(tr.selection.from))!;
+  return convertTableNodeToArrayOfRows(t.node).map((r) =>
+    r.map((c) => (c ? c.textContent : "")),
+  );
+};
+
+// 3-row x 2-col table; each row identifiable by its cells.
+const grid2x3 = () =>
+  doc(
+    table(
+      row(cell("r0a"), cell("r0b")),
+      row(cell("r1a"), cell("r1b")),
+      row(cell("r2a"), cell("r2b")),
+    ),
+  );
+
+const stateFor = (d: PMNode) =>
+  EditorState.create({ doc: d, selection: Selection.atStart(d) });
+
+describe("moveRow", () => {
+  it("moves the first row down to the last index, preserving content", () => {
+    // origin 0 -> target 2 makes row 0 land after the other rows: [r1, r2, r0].
+    const state = stateFor(grid2x3());
+    const tr = state.tr;
+    const ok = moveRow({
+      tr,
+      originIndex: 0,
+      targetIndex: 2,
+      select: false,
+      pos: state.selection.from,
+    });
+    expect(ok).toBe(true);
+    expect(grid(tr)).toEqual([
+      ["r1a", "r1b"],
+      ["r2a", "r2b"],
+      ["r0a", "r0b"],
+    ]);
+  });
+
+  it("moves a lower row up to an earlier index", () => {
+    // origin 2 -> target 0 lifts the last row above the rest: [r2, r0, r1].
+    const state = stateFor(grid2x3());
+    const tr = state.tr;
+    const ok = moveRow({
+      tr,
+      originIndex: 2,
+      targetIndex: 0,
+      select: false,
+      pos: state.selection.from,
+    });
+    expect(ok).toBe(true);
+    expect(grid(tr)).toEqual([
+      ["r2a", "r2b"],
+      ["r0a", "r0b"],
+      ["r1a", "r1b"],
+    ]);
+  });
+
+  it("never drops or duplicates rows when reordering", () => {
+    // The full multiset of cell texts is invariant under any valid move.
+    const state = stateFor(grid2x3());
+    const tr = state.tr;
+    moveRow({
+      tr,
+      originIndex: 1,
+      targetIndex: 2,
+      select: false,
+      pos: state.selection.from,
+    });
+    const flat = grid(tr).flat().sort();
+    expect(flat).toEqual(
+      ["r0a", "r0b", "r1a", "r1b", "r2a", "r2b"].sort(),
+    );
+    expect(grid(tr).length).toBe(3);
+  });
+
+  it("returns false (no-op) when target equals origin", () => {
+    // Moving a row onto itself is rejected and leaves the table unchanged.
+    const state = stateFor(grid2x3());
+    const tr = state.tr;
+    const before = grid(tr);
+    const ok = moveRow({
+      tr,
+      originIndex: 1,
+      targetIndex: 1,
+      select: false,
+      pos: state.selection.from,
+    });
+    expect(ok).toBe(false);
+    expect(grid(tr)).toEqual(before);
+  });
+
+  it("returns false when pos is not inside a table", () => {
+    // Without a table at `pos`, the function bails out instead of throwing.
+    const d = doc(
+      schema.nodes.paragraph.createChecked(null, schema.text("plain")),
+    );
+    const state = stateFor(d);
+    const tr = state.tr;
+    const ok = moveRow({
+      tr,
+      originIndex: 0,
+      targetIndex: 1,
+      select: false,
+      pos: state.selection.from,
+    });
+    expect(ok).toBe(false);
+  });
+
+  it("installs a CellSelection on the moved row when select is true", () => {
+    // With select:true the moved row at the target index is selected.
+    const state = stateFor(grid2x3());
+    const tr = state.tr;
+    const ok = moveRow({
+      tr,
+      originIndex: 0,
+      targetIndex: 2,
+      select: true,
+      pos: state.selection.from,
+    });
+    expect(ok).toBe(true);
+    expect(tr.selection instanceof CellSelection).toBe(true);
+  });
+});
diff --git a/packages/editor-ext/src/lib/unique-id/unique-id.util.test.ts b/packages/editor-ext/src/lib/unique-id/unique-id.util.test.ts
index 24d30408..64603b5b 100644
--- a/packages/editor-ext/src/lib/unique-id/unique-id.util.test.ts
+++ b/packages/editor-ext/src/lib/unique-id/unique-id.util.test.ts
@@ -100,4 +100,51 @@ describe("addUniqueIdsToDoc", () => {
     const [id] = ids(out);
     expect(id).toBeTruthy();
   });
+
+  it("only assigns ids to configured node types, not to others", () => {
+    // `types` is ["heading","paragraph"]; a codeBlock is NOT addressed, so it
+    // must come back without an id while the sibling paragraph is filled. (The
+    // UniqueID attribute only exists on configured types in the schema.)
+    const doc = {
+      type: "doc",
+      content: [
+        { type: "codeBlock", content: [{ type: "text", text: "x = 1" }] },
+        para(undefined, "after"),
+      ],
+    };
+    const out = addUniqueIdsToDoc(doc, extensions);
+    const [codeId, paraId] = ids(out);
+    expect(codeId).toBeUndefined();
+    expect(paraId).toBeTruthy();
+  });
+
+  it("assigns ids to target nodes nested inside non-target containers", () => {
+    // findChildren walks the whole tree: a paragraph inside a blockquote still
+    // gets an id, while the (non-target) blockquote wrapper does not.
+    const doc = {
+      type: "doc",
+      content: [
+        { type: "blockquote", content: [para(undefined, "quoted")] },
+      ],
+    };
+    const out = addUniqueIdsToDoc(doc, extensions) as any;
+    const blockquote = out.content[0];
+    const nestedPara = blockquote.content[0];
+    expect(blockquote.attrs?.id).toBeUndefined();
+    expect(nestedPara.attrs.id).toBeTruthy();
+  });
+
+  it("is idempotent: a second pass keeps every already-unique id unchanged", () => {
+    // Once ids are assigned and unique, re-running must be a fixed point — no
+    // churn that would invalidate stored MCP anchors on every save.
+    const doc = {
+      type: "doc",
+      content: [para(undefined, "a"), para(undefined, "b"), para(undefined, "c")],
+    };
+    const once = addUniqueIdsToDoc(doc, extensions);
+    const twice = addUniqueIdsToDoc(once, extensions);
+    expect(ids(twice)).toEqual(ids(once));
+    // And all three are distinct, so the second pass had real ids to preserve.
+    expect(new Set(ids(once)).size).toBe(3);
+  });
 });
diff --git a/packages/mcp/build/lib/auth-utils.js b/packages/mcp/build/lib/auth-utils.js
index cc61481c..39b91d9d 100644
--- a/packages/mcp/build/lib/auth-utils.js
+++ b/packages/mcp/build/lib/auth-utils.js
@@ -29,6 +29,41 @@ export async function getCollabToken(baseUrl, apiToken) {
         throw error;
     }
 }
+/**
+ * Pure cookie-parsing helper extracted from `performLogin` so the parsing logic
+ * can be unit-tested without performing the login network request. Given the
+ * raw `Set-Cookie` header array from the login response, return the `authToken`
+ * cookie's value.
+ *
+ * Behavior (kept identical to the original inline logic):
+ *  - throws if there is no Set-Cookie header at all;
+ *  - matches the cookie NAME exactly (`authToken`), so a future
+ *    `authTokenRefresh=...` cookie is NOT picked up (a `startsWith` would be);
+ *  - returns everything after the FIRST `=` up to the first `;`, so a base64
+ *    value containing `=` padding is preserved (a naive `split("=")` would
+ *    truncate it);
+ *  - cookie attributes after the first `;` (Path, HttpOnly, Expires, …) are
+ *    ignored;
+ *  - throws if no `authToken` cookie is present.
+ */
+export function extractAuthTokenFromSetCookie(cookies) {
+    if (!cookies) {
+        throw new Error("No Set-Cookie header found in login response");
+    }
+    // Match the cookie name exactly to avoid matching a future
+    // authTokenRefresh cookie (startsWith would catch it).
+    const authCookie = cookies.find((c) => {
+        const kv = c.split(";")[0];
+        return kv.slice(0, kv.indexOf("=")) === "authToken";
+    });
+    if (!authCookie) {
+        throw new Error("No authToken cookie found in login response");
+    }
+    // Take everything after the FIRST "=" up to the first ";".
+    // Splitting on "=" would truncate base64 values containing "=" padding.
+    const kv = authCookie.split(";")[0];
+    return kv.slice(kv.indexOf("=") + 1);
+}
 export async function performLogin(baseUrl, email, password) {
     try {
         const response = await axios.post(`${baseUrl}/auth/login`, {
@@ -36,24 +71,7 @@ export async function performLogin(baseUrl, email, password) {
             password,
         });
         // Extract token from Set-Cookie header
-        const cookies = response.headers["set-cookie"];
-        if (!cookies) {
-            throw new Error("No Set-Cookie header found in login response");
-        }
-        // Match the cookie name exactly to avoid matching a future
-        // authTokenRefresh cookie (startsWith would catch it).
-        const authCookie = cookies.find((c) => {
-            const kv = c.split(";")[0];
-            return kv.slice(0, kv.indexOf("=")) === "authToken";
-        });
-        if (!authCookie) {
-            throw new Error("No authToken cookie found in login response");
-        }
-        // Take everything after the FIRST "=" up to the first ";".
-        // Splitting on "=" would truncate base64 values containing "=" padding.
-        const kv = authCookie.split(";")[0];
-        const token = kv.slice(kv.indexOf("=") + 1);
-        return token;
+        return extractAuthTokenFromSetCookie(response.headers["set-cookie"]);
     }
     catch (error) {
         // Avoid leaking the full server response body by default; log only the
diff --git a/packages/mcp/src/lib/auth-utils.ts b/packages/mcp/src/lib/auth-utils.ts
index d677be25..a3a3b652 100644
--- a/packages/mcp/src/lib/auth-utils.ts
+++ b/packages/mcp/src/lib/auth-utils.ts
@@ -38,6 +38,45 @@ export async function getCollabToken(
   }
 }
 
+/**
+ * Pure cookie-parsing helper extracted from `performLogin` so the parsing logic
+ * can be unit-tested without performing the login network request. Given the
+ * raw `Set-Cookie` header array from the login response, return the `authToken`
+ * cookie's value.
+ *
+ * Behavior (kept identical to the original inline logic):
+ *  - throws if there is no Set-Cookie header at all;
+ *  - matches the cookie NAME exactly (`authToken`), so a future
+ *    `authTokenRefresh=...` cookie is NOT picked up (a `startsWith` would be);
+ *  - returns everything after the FIRST `=` up to the first `;`, so a base64
+ *    value containing `=` padding is preserved (a naive `split("=")` would
+ *    truncate it);
+ *  - cookie attributes after the first `;` (Path, HttpOnly, Expires, …) are
+ *    ignored;
+ *  - throws if no `authToken` cookie is present.
+ */
+export function extractAuthTokenFromSetCookie(
+  cookies: string[] | undefined,
+): string {
+  if (!cookies) {
+    throw new Error("No Set-Cookie header found in login response");
+  }
+  // Match the cookie name exactly to avoid matching a future
+  // authTokenRefresh cookie (startsWith would catch it).
+  const authCookie = cookies.find((c: string) => {
+    const kv = c.split(";")[0];
+    return kv.slice(0, kv.indexOf("=")) === "authToken";
+  });
+  if (!authCookie) {
+    throw new Error("No authToken cookie found in login response");
+  }
+
+  // Take everything after the FIRST "=" up to the first ";".
+  // Splitting on "=" would truncate base64 values containing "=" padding.
+  const kv = authCookie.split(";")[0];
+  return kv.slice(kv.indexOf("=") + 1);
+}
+
 export async function performLogin(
   baseUrl: string,
   email: string,
@@ -50,25 +89,7 @@ export async function performLogin(
     });
 
     // Extract token from Set-Cookie header
-    const cookies = response.headers["set-cookie"];
-    if (!cookies) {
-      throw new Error("No Set-Cookie header found in login response");
-    }
-    // Match the cookie name exactly to avoid matching a future
-    // authTokenRefresh cookie (startsWith would catch it).
-    const authCookie = cookies.find((c: string) => {
-      const kv = c.split(";")[0];
-      return kv.slice(0, kv.indexOf("=")) === "authToken";
-    });
-    if (!authCookie) {
-      throw new Error("No authToken cookie found in login response");
-    }
-
-    // Take everything after the FIRST "=" up to the first ";".
-    // Splitting on "=" would truncate base64 values containing "=" padding.
-    const kv = authCookie.split(";")[0];
-    const token = kv.slice(kv.indexOf("=") + 1);
-    return token;
+    return extractAuthTokenFromSetCookie(response.headers["set-cookie"]);
   } catch (error: any) {
     // Avoid leaking the full server response body by default; log only the
     // HTTP status. Log the verbose body only when DEBUG is set.
diff --git a/packages/mcp/test/unit/auth-cookie.test.mjs b/packages/mcp/test/unit/auth-cookie.test.mjs
new file mode 100644
index 00000000..92206cf4
--- /dev/null
+++ b/packages/mcp/test/unit/auth-cookie.test.mjs
@@ -0,0 +1,93 @@
+// Cookie parsing for the login flow.
+//
+// `performLogin` in auth-utils.ts does a real network POST and then extracts the
+// auth token from the response's Set-Cookie header. The cookie-parsing logic was
+// extracted into the pure, exported helper `extractAuthTokenFromSetCookie` so it
+// can be tested without network I/O; `performLogin` now delegates to it, so these
+// tests cover the exact parsing path the login uses.
+import { test } from "node:test";
+import assert from "node:assert/strict";
+
+import { extractAuthTokenFromSetCookie } from "../../build/lib/auth-utils.js";
+
+// ---------------------------------------------------------------------------
+// Happy path: a single authToken cookie with attributes.
+// ---------------------------------------------------------------------------
+test("extracts the authToken value, ignoring trailing attributes", () => {
+  const cookies = [
+    "authToken=abc123; Path=/; HttpOnly; Secure; SameSite=Lax",
+  ];
+  assert.equal(extractAuthTokenFromSetCookie(cookies), "abc123");
+});
+
+// ---------------------------------------------------------------------------
+// A base64/JWT value containing "=" padding must NOT be truncated: only the
+// FIRST "=" separates name from value.
+// ---------------------------------------------------------------------------
+test("preserves an '=' inside the value (base64 padding is not truncated)", () => {
+  const jwt = "eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiIxIn0=";
+  const cookies = [`authToken=${jwt}; Path=/`];
+  assert.equal(extractAuthTokenFromSetCookie(cookies), jwt);
+});
+
+// ---------------------------------------------------------------------------
+// Exact-name match: a different cookie whose name merely STARTS WITH "authToken"
+// (e.g. authTokenRefresh) must not be picked up; the real authToken wins.
+// ---------------------------------------------------------------------------
+test("matches the cookie name exactly, not by prefix (authTokenRefresh ignored)", () => {
+  const cookies = [
+    "authTokenRefresh=refreshvalue; Path=/; HttpOnly",
+    "authToken=realtoken; Path=/; HttpOnly",
+  ];
+  assert.equal(extractAuthTokenFromSetCookie(cookies), "realtoken");
+});
+
+// ---------------------------------------------------------------------------
+// Picks the authToken out of several unrelated cookies regardless of order.
+// ---------------------------------------------------------------------------
+test("selects authToken among multiple unrelated cookies", () => {
+  const cookies = [
+    "session=xyz; Path=/",
+    "authToken=tok-7; Path=/; HttpOnly",
+    "theme=dark",
+  ];
+  assert.equal(extractAuthTokenFromSetCookie(cookies), "tok-7");
+});
+
+// ---------------------------------------------------------------------------
+// An empty value is valid and returns "".
+// ---------------------------------------------------------------------------
+test("returns an empty string when authToken has an empty value", () => {
+  assert.equal(extractAuthTokenFromSetCookie(["authToken=; Path=/"]), "");
+});
+
+// ---------------------------------------------------------------------------
+// Missing Set-Cookie header -> documented error.
+// ---------------------------------------------------------------------------
+test("throws when there is no Set-Cookie header", () => {
+  assert.throws(
+    () => extractAuthTokenFromSetCookie(undefined),
+    /No Set-Cookie header/,
+  );
+});
+
+// ---------------------------------------------------------------------------
+// Set-Cookie present but no authToken cookie -> documented error.
+// ---------------------------------------------------------------------------
+test("throws when no authToken cookie is present", () => {
+  assert.throws(
+    () => extractAuthTokenFromSetCookie(["session=xyz; Path=/", "theme=dark"]),
+    /No authToken cookie/,
+  );
+});
+
+// ---------------------------------------------------------------------------
+// An empty cookie array also yields the "no authToken" error (header exists but
+// is empty), distinct from the "no Set-Cookie header" case above.
+// ---------------------------------------------------------------------------
+test("throws 'no authToken' (not 'no header') for an empty cookie array", () => {
+  assert.throws(
+    () => extractAuthTokenFromSetCookie([]),
+    /No authToken cookie/,
+  );
+});
diff --git a/packages/mcp/test/unit/comment-anchor-apply.test.mjs b/packages/mcp/test/unit/comment-anchor-apply.test.mjs
new file mode 100644
index 00000000..46049c02
--- /dev/null
+++ b/packages/mcp/test/unit/comment-anchor-apply.test.mjs
@@ -0,0 +1,111 @@
+// applyAnchorInDoc — first-match / ambiguity / boundary behavior.
+//
+// comment-anchor.test.mjs already covers the core apply paths (single-node
+// match, spanning adjacent text nodes, code/italic boundary mark preservation,
+// smart-quote normalization, no-match-no-mutation, pre-existing comment mark
+// replacement, nested-list DFS). This file focuses on the SELECTION/RESOLUTION
+// behavior those tests don't pin down: which occurrence/block wins when a
+// selection appears more than once, sub-word ranges, and the run boundary
+// created by a non-text inline node.
+import { test } from "node:test";
+import assert from "node:assert/strict";
+
+import { applyAnchorInDoc, canAnchorInDoc } from "../../build/lib/comment-anchor.js";
+
+const commentMark = (node) =>
+  (Array.isArray(node.marks) ? node.marks : []).find((m) => m && m.type === "comment") || null;
+const paragraphDoc = (content) => ({ type: "doc", content: [{ type: "paragraph", content }] });
+
+// ---------------------------------------------------------------------------
+// Document order: when two separate blocks both contain the selection, only the
+// FIRST block (DFS document order) is anchored; the second is left untouched.
+// ---------------------------------------------------------------------------
+test("anchors only the FIRST block when the selection occurs in two blocks", () => {
+  const doc = {
+    type: "doc",
+    content: [
+      { type: "paragraph", content: [{ type: "text", text: "first target here" }] },
+      { type: "paragraph", content: [{ type: "text", text: "second target here" }] },
+    ],
+  };
+  assert.equal(applyAnchorInDoc(doc, "target", "C"), true);
+
+  const marked0 = doc.content[0].content.filter((p) => commentMark(p));
+  const marked1 = doc.content[1].content.filter((p) => commentMark(p));
+  assert.equal(marked0.length, 1, "first block is anchored");
+  assert.equal(marked0[0].text, "target");
+  assert.equal(marked1.length, 0, "second block is left untouched");
+});
+
+// ---------------------------------------------------------------------------
+// Ambiguity within one block: indexOf finds the FIRST occurrence, so only the
+// first "ab" is marked; the later occurrences stay in one unmarked fragment.
+// ---------------------------------------------------------------------------
+test("anchors only the FIRST occurrence within a block (ambiguous selection)", () => {
+  const doc = paragraphDoc([{ type: "text", text: "ab ab ab" }]);
+  assert.equal(applyAnchorInDoc(doc, "ab", "C"), true);
+
+  const parts = doc.content[0].content;
+  assert.equal(parts.length, 2, "split into [marked, rest]");
+  assert.equal(parts[0].text, "ab");
+  assert.ok(commentMark(parts[0]), "first occurrence is marked");
+  assert.equal(parts[1].text, " ab ab");
+  assert.equal(commentMark(parts[1]), null, "later occurrences are not marked");
+});
+
+// ---------------------------------------------------------------------------
+// Sub-word range: a selection that is a substring inside a single text node is
+// spliced into before / marked / after, marking exactly the matched characters.
+// ---------------------------------------------------------------------------
+test("anchors a sub-word range inside a single text node", () => {
+  const doc = paragraphDoc([{ type: "text", text: "Hello" }]);
+  assert.equal(applyAnchorInDoc(doc, "ell", "C"), true);
+
+  const parts = doc.content[0].content;
+  assert.deepEqual(parts.map((p) => p.text), ["H", "ell", "o"]);
+  assert.equal(commentMark(parts[0]), null);
+  assert.ok(commentMark(parts[1]), "only the matched substring is marked");
+  assert.equal(commentMark(parts[2]), null);
+});
+
+// ---------------------------------------------------------------------------
+// A non-text inline node (hardBreak) breaks the matching run: a selection that
+// would span the break cannot match, but one wholly inside a run still does.
+// ---------------------------------------------------------------------------
+test("a non-text inline node breaks the run: cross-break selection does not match", () => {
+  const make = () =>
+    paragraphDoc([
+      { type: "text", text: "foo" },
+      { type: "hardBreak" },
+      { type: "text", text: "bar" },
+    ]);
+
+  // "foobar" straddles the hardBreak -> no match, no mutation.
+  const docA = make();
+  const before = JSON.stringify(docA);
+  assert.equal(canAnchorInDoc(docA, "foobar"), false);
+  assert.equal(applyAnchorInDoc(docA, "foobar", "C"), false);
+  assert.equal(JSON.stringify(docA), before, "failed match must not mutate");
+
+  // "foo" lives entirely in the first run -> matches and is marked; the
+  // hardBreak node is preserved untouched.
+  const docB = make();
+  assert.equal(applyAnchorInDoc(docB, "foo", "C"), true);
+  const parts = docB.content[0].content;
+  assert.equal(parts[0].text, "foo");
+  assert.ok(commentMark(parts[0]));
+  assert.equal(parts[1].type, "hardBreak", "the inline atom is preserved");
+  assert.equal(parts[2].text, "bar");
+  assert.equal(commentMark(parts[2]), null);
+});
+
+// ---------------------------------------------------------------------------
+// A whitespace-only selection normalizes to empty and never anchors.
+// ---------------------------------------------------------------------------
+test("a whitespace-only selection does not anchor and does not mutate", () => {
+  const doc = paragraphDoc([{ type: "text", text: "hello world" }]);
+  const before = JSON.stringify(doc);
+  assert.equal(canAnchorInDoc(doc, "   "), false);
+  assert.equal(applyAnchorInDoc(doc, "   ", "C"), false);
+  assert.equal(JSON.stringify(doc), before);
+});
diff --git a/packages/mcp/test/unit/media-roundtrip-attrs.test.mjs b/packages/mcp/test/unit/media-roundtrip-attrs.test.mjs
new file mode 100644
index 00000000..37668fe0
--- /dev/null
+++ b/packages/mcp/test/unit/media-roundtrip-attrs.test.mjs
@@ -0,0 +1,135 @@
+// Extra media round-trip coverage (issue #244), complementing
+// media-roundtrip.test.mjs.
+//
+// The existing media-roundtrip.test.mjs already asserts that video, youtube,
+// embed, excalidraw, audio and pdf SURVIVE a PM -> markdown -> PM round-trip and
+// keeps their identifying src / provider / name / attachmentId. It does NOT,
+// however, exercise:
+//   * the `drawio` node (a distinct schema node that shares the excalidraw
+//     converter case) — not covered at all;
+//   * the dimension / layout attributes (width, height, align) that ride in
+//     data-* attributes — exactly where a converter<->schema mismatch silently
+//     drops a value while the node itself survives;
+//   * attribute escaping for a src containing `"` (escapeAttr) — a malformed
+//     value here would either break the round-trip or inject HTML.
+//
+// These are the gaps this file locks down.
+import { test } from "node:test";
+import assert from "node:assert/strict";
+
+import { convertProseMirrorToMarkdown } from "../../build/lib/markdown-converter.js";
+import { markdownToProseMirror } from "../../build/lib/collaboration.js";
+
+const doc = (...content) => ({ type: "doc", content });
+
+const findAll = (node, type, acc = []) => {
+  if (!node || typeof node !== "object") return acc;
+  if (node.type === type) acc.push(node);
+  for (const c of node.content || []) findAll(c, type, acc);
+  return acc;
+};
+
+// PM node -> markdown -> PM; return both the markdown and the matching nodes.
+const roundtrip = async (node, type) => {
+  const md = convertProseMirrorToMarkdown(doc(node));
+  const pm = await markdownToProseMirror(md);
+  return { md, found: findAll(pm, type) };
+};
+
+// ---------------------------------------------------------------------------
+// drawio: a separate schema node sharing the excalidraw converter case. Not
+// covered by the existing file at all, so guard its full round-trip here.
+// ---------------------------------------------------------------------------
+test("round-trip: drawio diagram survives with src, title, dimensions, align, attachmentId", async () => {
+  const { md, found } = await roundtrip(
+    {
+      type: "drawio",
+      attrs: {
+        src: "/api/files/d.drawio",
+        title: "Flow",
+        width: 400,
+        height: 300,
+        align: "left",
+        attachmentId: "dz1",
+      },
+    },
+    "drawio",
+  );
+  // The converter must emit the schema-matching div[data-type="drawio"].
+  assert.match(md, /data-type="drawio"/);
+  assert.equal(found.length, 1, "drawio node must survive the round-trip");
+  const a = found[0].attrs;
+  assert.equal(a.src, "/api/files/d.drawio");
+  assert.equal(a.title, "Flow");
+  assert.equal(a.attachmentId, "dz1");
+  assert.equal(a.align, "left");
+  // Numeric dimensions come back as strings via the schema parseHTML.
+  assert.equal(String(a.width), "400");
+  assert.equal(String(a.height), "300");
+});
+
+// ---------------------------------------------------------------------------
+// Dimension + align attrs ride in data-* (or width/height) attributes. The
+// existing file checks only src/provider/name/attachmentId, so a dropped
+// width/height/align would pass there but fail here.
+// ---------------------------------------------------------------------------
+test("round-trip: youtube preserves width/height/align (data-* attrs)", async () => {
+  const { found } = await roundtrip(
+    { type: "youtube", attrs: { src: "https://youtube.com/watch?v=x", width: 560, height: 315, align: "left" } },
+    "youtube",
+  );
+  assert.equal(found.length, 1);
+  const a = found[0].attrs;
+  assert.equal(String(a.width), "560");
+  assert.equal(String(a.height), "315");
+  assert.equal(a.align, "left");
+});
+
+test("round-trip: embed preserves provider, width/height and align", async () => {
+  const { found } = await roundtrip(
+    { type: "embed", attrs: { src: "https://e.com/x", provider: "iframe", width: 600, height: 480, align: "right" } },
+    "embed",
+  );
+  assert.equal(found.length, 1);
+  const a = found[0].attrs;
+  assert.equal(a.provider, "iframe");
+  assert.equal(String(a.width), "600");
+  assert.equal(String(a.height), "480");
+  assert.equal(a.align, "right");
+});
+
+test("round-trip: video preserves width/height and align (data-align)", async () => {
+  const { found } = await roundtrip(
+    { type: "video", attrs: { src: "/api/files/v.mp4", attachmentId: "att1", width: 640, height: 360, align: "right" } },
+    "video",
+  );
+  assert.equal(found.length, 1);
+  const a = found[0].attrs;
+  assert.equal(String(a.width), "640");
+  assert.equal(String(a.height), "360");
+  assert.equal(a.align, "right");
+});
+
+test("round-trip: pdf preserves width/height (standard attrs) plus name", async () => {
+  const { found } = await roundtrip(
+    { type: "pdf", attrs: { src: "/api/files/x.pdf", name: "x.pdf", attachmentId: "a4", width: 700, height: 900 } },
+    "pdf",
+  );
+  assert.equal(found.length, 1);
+  const a = found[0].attrs;
+  assert.equal(a.name, "x.pdf");
+  assert.equal(String(a.width), "700");
+  assert.equal(String(a.height), "900");
+});
+
+// ---------------------------------------------------------------------------
+// Escaping: a src containing a double quote must survive the attribute-quoted
+// HTML emission (escapeAttr) and re-parse to the exact original value, with no
+// node loss and no HTML injection.
+// ---------------------------------------------------------------------------
+test("round-trip: a src containing a double quote is escaped and recovered intact", async () => {
+  const tricky = 'https://e.com/x?a="b"&c=1';
+  const { found } = await roundtrip({ type: "youtube", attrs: { src: tricky } }, "youtube");
+  assert.equal(found.length, 1, "node must survive a quote-bearing src");
+  assert.equal(found[0].attrs.src, tricky, "the exact src is recovered");
+});
diff --git a/packages/mcp/test/unit/recreate-transform-drift.test.mjs b/packages/mcp/test/unit/recreate-transform-drift.test.mjs
new file mode 100644
index 00000000..b950cdaf
--- /dev/null
+++ b/packages/mcp/test/unit/recreate-transform-drift.test.mjs
@@ -0,0 +1,139 @@
+// CONTRACT / DRIFT GUARD: mcp diff vs the vendored editor-ext recreate-transform.
+//
+// packages/mcp/src/lib/diff.ts computes its document diff with
+// `recreateTransform` from the published @fellow/prosemirror-recreate-transform
+// package. Docmost's in-app history editor computes the SAME diff with its own
+// vendored copy at
+// packages/editor-ext/src/lib/recreate-transform/recreateTransform.ts.
+// diff.ts's header comment claims the two are "identical" — if they ever drift,
+// the headless mcp diff would stop matching what a user sees in the app.
+//
+// This test guards that claim two ways, on representative doc pairs, using the
+// EXACT options diff.ts passes (complexSteps:false, wordDiffs:true,
+// simplifyDiff:true):
+//   1. invariant: each implementation's transform reproduces the target doc
+//      (apply(diff) == target);
+//   2. cross-copy parity: both implementations emit the SAME step sequence, so a
+//      behavioral divergence between the two copies fails this test.
+//
+// The vendored copy is TypeScript, so it is transpiled to CommonJS at test time
+// and required directly — the test runs the ACTUAL vendored source, not a stand-in.
+import { test, before } from "node:test";
+import assert from "node:assert/strict";
+import ts from "typescript";
+import fs from "node:fs";
+import path from "node:path";
+import { createRequire } from "node:module";
+import { fileURLToPath } from "node:url";
+
+import { recreateTransform as fellowRecreate } from "@fellow/prosemirror-recreate-transform";
+import { Node } from "@tiptap/pm/model";
+import { docmostSchema } from "../../build/lib/docmost-schema.js";
+
+const require = createRequire(import.meta.url);
+const HERE = path.dirname(fileURLToPath(import.meta.url));
+// .../packages/mcp/test/unit -> repo packages root.
+const PACKAGES = path.resolve(HERE, "..", "..", "..");
+const VENDOR_SRC = path.join(
+  PACKAGES,
+  "editor-ext",
+  "src",
+  "lib",
+  "recreate-transform",
+);
+// Emit transpiled CJS under mcp/build so Node resolves the hoisted deps
+// (@tiptap/pm, rfc6902, diff) up the directory tree exactly as diff.js does.
+const VENDOR_OUT = path.resolve(HERE, "..", "..", "build", "_vendored_editor_ext");
+
+// The exact options the mcp diff pipeline uses (diff.ts).
+const DIFF_OPTS = { complexSteps: false, wordDiffs: true, simplifyDiff: true };
+
+let vendoredRecreate;
+
+before(() => {
+  assert.ok(
+    fs.existsSync(VENDOR_SRC),
+    `vendored recreate-transform sources missing at ${VENDOR_SRC}`,
+  );
+  fs.rmSync(VENDOR_OUT, { recursive: true, force: true });
+  fs.mkdirSync(VENDOR_OUT, { recursive: true });
+  // Mark the output as CommonJS so relative `require("./x")` resolves to x.js.
+  fs.writeFileSync(
+    path.join(VENDOR_OUT, "package.json"),
+    JSON.stringify({ type: "commonjs" }),
+  );
+  for (const f of fs.readdirSync(VENDOR_SRC)) {
+    if (!f.endsWith(".ts")) continue;
+    const code = fs.readFileSync(path.join(VENDOR_SRC, f), "utf8");
+    const out = ts.transpileModule(code, {
+      compilerOptions: {
+        module: ts.ModuleKind.CommonJS,
+        target: ts.ScriptTarget.ES2020,
+      },
+    });
+    fs.writeFileSync(path.join(VENDOR_OUT, f.replace(/\.ts$/, ".js")), out.outputText);
+  }
+  vendoredRecreate = require(path.join(VENDOR_OUT, "index.js")).recreateTransform;
+  assert.equal(typeof vendoredRecreate, "function", "vendored recreateTransform loaded");
+});
+
+// ---------------------------------------------------------------------------
+// Builders + representative doc pairs covering the diff shapes diff.ts handles.
+// ---------------------------------------------------------------------------
+const t = (text, marks) => (marks ? { type: "text", text, marks } : { type: "text", text });
+const para = (...c) => ({ type: "paragraph", content: c });
+const doc = (...c) => ({ type: "doc", content: c });
+
+const PAIRS = [
+  // word inserted mid-sentence
+  ["insert word", doc(para(t("Hello world"))), doc(para(t("Hello brave world")))],
+  // whole block deleted
+  ["delete block", doc(para(t("keep this")), para(t("remove this"))), doc(para(t("keep this")))],
+  // word removed mid-sentence
+  ["delete word", doc(para(t("one two three"))), doc(para(t("one three")))],
+  // pure mark addition (complexSteps:false treats it as a content step)
+  ["add mark", doc(para(t("plain"))), doc(para(t("plain", [{ type: "bold" }])))],
+  // two blocks swapped (reorder)
+  ["reorder blocks", doc(para(t("a")), para(t("b"))), doc(para(t("b")), para(t("a")))],
+  // structural insert: an image node appears
+  [
+    "insert image",
+    doc(para(t("caption"))),
+    doc(para(t("caption")), { type: "image", attrs: { src: "/api/files/a.png", attachmentId: "i1" } }),
+  ],
+];
+
+const stepsJSON = (tr) => JSON.stringify(tr.steps.map((s) => s.toJSON()));
+
+for (const [label, fromJSON, toJSON] of PAIRS) {
+  test(`invariant: @fellow recreateTransform reproduces the target (${label})`, () => {
+    const from = Node.fromJSON(docmostSchema, fromJSON);
+    const to = Node.fromJSON(docmostSchema, toJSON);
+    const tr = fellowRecreate(from, to, DIFF_OPTS);
+    // apply(diff) == target, comparing schema-normalized JSON on both sides.
+    assert.equal(JSON.stringify(tr.doc.toJSON()), JSON.stringify(to.toJSON()));
+  });
+
+  test(`drift: @fellow and vendored editor-ext emit identical steps (${label})`, () => {
+    const mk = () => [
+      Node.fromJSON(docmostSchema, fromJSON),
+      Node.fromJSON(docmostSchema, toJSON),
+    ];
+    const [fA, tA] = mk();
+    const [fB, tB] = mk();
+    const trFellow = fellowRecreate(fA, tA, DIFF_OPTS);
+    const trVendor = vendoredRecreate(fB, tB, DIFF_OPTS);
+
+    // Both must reach the same target...
+    const target = JSON.stringify(tA.toJSON());
+    assert.equal(JSON.stringify(trFellow.doc.toJSON()), target, "fellow reaches target");
+    assert.equal(JSON.stringify(trVendor.doc.toJSON()), target, "vendored reaches target");
+    // ...and, critically, via the SAME step sequence. A divergence in the two
+    // recreate-transform copies' algorithm would change the steps and fail here.
+    assert.equal(
+      stepsJSON(trVendor),
+      stepsJSON(trFellow),
+      `vendored editor-ext drifted from @fellow on "${label}"`,
+    );
+  });
+}