fix(collab): hoist intentional-clear consume out of the store retry loop (#251)

The store-side empty-guard consumed the per-document intentional-clear flag
INSIDE the bounded retry loop. consumeIntentionalClear always deletes the
in-memory Map entry, but a tx rollback cannot un-delete it: attempt 1
consumed the flag then updatePage threw a transient error and rolled back;
attempt 2 re-read the page non-empty, saw the flag gone, and the empty-guard
silently BLOCKED the write — dropping the user's deliberate clear and
defeating the retry guarantee for clears.

Hoist the decision out of the loop (like consumeContributors /
consumeAgentTouched): consume once into `allowIntentionalClear` before the
`for`, and only read that boolean on the empty-over-non-empty branch. The
single hoisted consume still drops a pending flag for a non-empty store
(the "cleared then retyped" case), since every store consumes regardless of
incoming emptiness.

Add a regression test: arm via the real onStateless transport, updatePage
throws once then succeeds, assert it is called twice and the retry writes the
empty doc (the clear survives). It fails on the old consume-in-loop ordering
(updatePage called once) and passes after the hoist.

Document the known fail-safe limitation near the TTL constant: if document
ownership transfers / a node crashes between the stateless signal and the
debounced store, the in-memory flag is lost and the clear is silently not
applied (the doc reloads non-empty) — fail-safe, content is never destroyed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/client/src/features/editor/extensions/extensions.ts

@@ -123,6 +123,7 @@ import { countWords } from "alfaaz";
 import AutoJoiner from "@/features/editor/extensions/autojoiner.ts";
 import GlobalDragHandle from "@/features/editor/extensions/drag-handle.ts";
 import { CleanStyles } from "@/features/editor/extensions/clean-styles.ts";
+import { IntentionalClear } from "@/features/editor/extensions/intentional-clear.ts";
 
 const lowlight = createLowlight(common);
 lowlight.register("mermaid", plaintext);
@@ -486,4 +487,10 @@ export const collabExtensions: CollabExtensions = (provider, user) => [
       color: randomElement(userColors),
     },
   }),
+  // #251 — emit an intentional-clear signal to the server when the user
+  // deliberately empties the page, so the #248 store-side empty-guard lets that
+  // one clear through while still blocking accidental empties.
+  IntentionalClear.configure({
+    provider,
+  }),
 ];

apps/client/src/features/editor/extensions/intentional-clear.test.ts

@@ -0,0 +1,88 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { Editor } from "@tiptap/core";
+import { Document } from "@tiptap/extension-document";
+import { Paragraph } from "@tiptap/extension-paragraph";
+import { Text } from "@tiptap/extension-text";
+import {
+  IntentionalClear,
+  INTENTIONAL_CLEAR_MESSAGE_TYPE,
+} from "./intentional-clear";
+
+/**
+ * #251 — the intentional-clear signal is driven through the REAL editor path:
+ * a fresh Editor with the IntentionalClear extension, a fake provider that
+ * records sendStateless, and the actual select-all + delete command the user's
+ * keystroke runs. No hand-poke of any flag.
+ */
+describe("IntentionalClear extension", () => {
+  let sendStateless: ReturnType<typeof vi.fn>;
+
+  const makeEditor = (content: unknown) =>
+    new Editor({
+      extensions: [
+        Document,
+        Paragraph,
+        Text,
+        IntentionalClear.configure({
+          // Minimal provider stand-in: only sendStateless is exercised.
+          provider: { sendStateless } as any,
+        }),
+      ],
+      content: content as any,
+    });
+
+  beforeEach(() => {
+    sendStateless = vi.fn();
+  });
+
+  it("emits the clear signal when a user empties a non-empty doc (select-all + delete)", () => {
+    const editor = makeEditor({
+      type: "doc",
+      content: [
+        { type: "paragraph", content: [{ type: "text", text: "hello world" }] },
+      ],
+    });
+
+    // The exact command path a select-all + Delete keystroke dispatches.
+    editor.chain().selectAll().deleteSelection().run();
+
+    expect(sendStateless).toHaveBeenCalledTimes(1);
+    const payload = JSON.parse(sendStateless.mock.calls[0][0]);
+    expect(payload).toEqual({ type: INTENTIONAL_CLEAR_MESSAGE_TYPE });
+
+    editor.destroy();
+  });
+
+  it("does NOT emit when typing into an empty doc (no non-empty → empty transition)", () => {
+    const editor = makeEditor({ type: "doc", content: [{ type: "paragraph" }] });
+
+    editor.chain().insertContent("typed text").run();
+
+    expect(sendStateless).not.toHaveBeenCalled();
+    editor.destroy();
+  });
+
+  it("does NOT emit on an edit that leaves the doc non-empty", () => {
+    const editor = makeEditor({
+      type: "doc",
+      content: [
+        { type: "paragraph", content: [{ type: "text", text: "keep me" }] },
+      ],
+    });
+
+    editor.chain().insertContent(" more").run();
+
+    expect(sendStateless).not.toHaveBeenCalled();
+    editor.destroy();
+  });
+
+  it("does NOT emit when the doc was already empty", () => {
+    const editor = makeEditor({ type: "doc", content: [{ type: "paragraph" }] });
+
+    // Selecting all + delete on an already-empty doc is a no-op transition.
+    editor.chain().selectAll().deleteSelection().run();
+
+    expect(sendStateless).not.toHaveBeenCalled();
+    editor.destroy();
+  });
+});

apps/client/src/features/editor/extensions/intentional-clear.ts

@@ -0,0 +1,94 @@
+import { Extension } from "@tiptap/core";
+import { isChangeOrigin } from "@tiptap/extension-collaboration";
+import type { Node as PMNode } from "@tiptap/pm/model";
+import type { HocuspocusProvider } from "@hocuspocus/provider";
+
+/**
+ * Stateless message type sent to the server when a user deliberately clears a
+ * page to empty. Kept in one place so the client emitter and the server
+ * consumer (PersistenceExtension.onStateless) agree on the wire format.
+ */
+export const INTENTIONAL_CLEAR_MESSAGE_TYPE = "intentional-clear";
+
+export interface IntentionalClearOptions {
+  /** The collab provider used to send the stateless clear signal. */
+  provider: HocuspocusProvider | null;
+}
+
+/**
+ * A "document is empty" check that mirrors the server's `isEmptyParagraphDoc`
+ * (collaboration.util.ts): exactly one top-level paragraph with no inline
+ * content. After a select-all + delete TipTap leaves precisely this shape, so
+ * matching it here keeps the client signal aligned with the server guard that
+ * consumes it.
+ */
+function isEmptyParagraphDoc(doc: PMNode): boolean {
+  if (doc.childCount !== 1) return false;
+  const child = doc.firstChild;
+  return (
+    child !== null &&
+    child !== undefined &&
+    child.type.name === "paragraph" &&
+    child.content.size === 0
+  );
+}
+
+/**
+ * #251 — intentional-clear signal.
+ *
+ * The server's #248 store-side empty-guard unconditionally refuses to overwrite
+ * non-empty persisted content with an empty document, because a momentarily
+ * empty live Y.Doc (a glitch, a bad merge, an emptying transclusion) is
+ * indistinguishable from a real clear *at the store layer*. That protection is
+ * correct, but it also blocks a user who genuinely wants to empty the page.
+ *
+ * This extension supplies the missing distinction. It watches LOCAL, user-driven
+ * transactions and, the moment one reduces a non-empty document to the empty
+ * single-paragraph shape, it sends a hocuspocus stateless message to the server.
+ * The server records a short-lived, single-use "intentional clear pending" flag
+ * for this document that the next (debounced) onStoreDocument consumes to let
+ * that one empty write through the guard.
+ *
+ * What counts as an intentional clear (precise definition):
+ *  - the transaction actually changed the document (`docChanged`), AND
+ *  - it is a LOCAL user edit, not a remote collab application — remote y-sync
+ *    transactions are tagged and filtered out via `isChangeOrigin`, so an
+ *    emptiness that arrives from another client / a merge never emits a signal,
+ *    AND
+ *  - the document was non-empty before the transaction and is the empty
+ *    single-paragraph doc after it.
+ *
+ * This is exactly the select-all + Delete / Backspace (or any local command that
+ * empties the doc, e.g. clearContent) keystroke path. A transient/programmatic
+ * empty serialization that the server might see on the wire does NOT come with
+ * this signal, so the guard still blocks it.
+ */
+export const IntentionalClear = Extension.create<IntentionalClearOptions>({
+  name: "intentionalClear",
+
+  addOptions() {
+    return {
+      provider: null,
+    };
+  },
+
+  onTransaction({ transaction }) {
+    if (!transaction.docChanged) return;
+    // Only react to local user edits. Remote collaboration steps (and other
+    // y-sync-applied changes) carry the change origin and must never be treated
+    // as an intentional clear, otherwise a remote/merge-induced emptiness would
+    // punch through the server guard.
+    if (isChangeOrigin(transaction)) return;
+
+    const becameEmpty =
+      !isEmptyParagraphDoc(transaction.before) &&
+      isEmptyParagraphDoc(transaction.doc);
+    if (!becameEmpty) return;
+
+    // The server reads the originating document from the connection, so the
+    // payload only needs to declare intent — it cannot target another document.
+    this.options.provider?.sendStateless(
+      JSON.stringify({ type: INTENTIONAL_CLEAR_MESSAGE_TYPE }),
+    );
+  },
+});

apps/server/src/collaboration/extensions/persistence-store.spec.ts

@@ -205,17 +205,11 @@ describe('PersistenceExtension.onStoreDocument — Approach-A boundary snapshot'
     expect(historyQueue.add).toHaveBeenCalledTimes(1);
   });
 
-  // #206 persist-6 — RED (it.failing): a momentarily-empty live Y.Doc must not
+  // #206 persist-6 / #248 — a momentarily-empty live Y.Doc must not overwrite
-  // overwrite non-empty persisted content. `onStoreDocument` empty-guards the
+  // non-empty persisted content. The store-side empty-guard blocks an empty doc
-  // LOAD path but not the STORE path, so today an empty doc (a client/agent
+  // (a client/agent glitch, a bad merge, an emptying transclusion) from wiping
-  // glitch, a bad merge, an emptying transclusion) is written straight over the
+  // the page silently when NO intentional-clear signal is present.
-  // page and the content is wiped silently. A store-side empty-guard is a real
+  it('does NOT overwrite non-empty content with a momentarily-empty live doc (persist-6)', async () => {
-  // behaviour change (a deliberate "select-all + delete" is also empty), so it
-  // is left UNFIXED pending a product decision; this documents the data-loss
-  // path and flips to a normal passing test the moment the guard lands.
-  it.failing(
-    'does NOT overwrite non-empty content with a momentarily-empty live doc (persist-6)',
-    async () => {
     const emptyDoc = { type: 'doc', content: [{ type: 'paragraph' }] };
     const document = ydocFor(emptyDoc);
     pageRepo.findById.mockResolvedValue({
@@ -225,11 +219,189 @@ describe('PersistenceExtension.onStoreDocument — Approach-A boundary snapshot'
 
     await ext.onStoreDocument(buildData(document, 'user') as any);
 
-      // Desired contract: the empty incoming doc is rejected and the rich page
+    // The empty incoming doc is rejected and the rich page survives.
-      // survives. Today updatePage is called with the empty content (data loss).
     expect(pageRepo.updatePage).not.toHaveBeenCalled();
-    },
+  });
+
+  // #248 — an empty-over-empty store is allowed (nothing to lose); the guard
+  // only protects non-empty persisted content.
+  it('allows an empty store over already-empty content (#248)', async () => {
+    const liveEmptyDoc = { type: 'doc', content: [{ type: 'paragraph' }] };
+    const document = ydocFor(liveEmptyDoc);
+    // Stored content is empty per isEmptyParagraphDoc (paragraph with content:[])
+    // but NOT deep-equal to the normalized live doc, so the unchanged
+    // short-circuit is skipped and the empty-guard is genuinely reached.
+    pageRepo.findById.mockResolvedValue({
+      ...persistedHumanPage('IGNORED'),
+      content: { type: 'doc', content: [{ type: 'paragraph', content: [] }] },
+    });
+
+    await ext.onStoreDocument(buildData(document, 'user') as any);
+
+    expect(pageRepo.updatePage).toHaveBeenCalledTimes(1);
+  });
+
+  // #251 — REAL-PATH regression test. The intentional-clear signal is set via
+  // the actual transport seam (ext.onStateless with the exact stateless payload
+  // the client's IntentionalClear extension sends), NOT a hand-injected
+  // context.intentionalClear poke. We then run the debounced store with an empty
+  // live doc over non-empty persisted content and assert the empty write goes
+  // through — i.e. the clear persists.
+  it('persists an intentional clear signalled via the real stateless transport (#251)', async () => {
+    const documentName = `page.${PAGE_ID}`;
+    const emptyDoc = { type: 'doc', content: [{ type: 'paragraph' }] };
+    const document = ydocFor(emptyDoc);
+    pageRepo.findById.mockResolvedValue({
+      ...persistedHumanPage('IGNORED'),
+      content: doc('IMPORTANT RICH CONTENT'),
+    });
+
+    // The client signalled a deliberate clear over the live connection.
+    await ext.onStateless({
+      connection: { readOnly: false } as any,
+      documentName,
+      document: document as any,
+      payload: JSON.stringify({ type: 'intentional-clear' }),
+    } as any);
+
+    await ext.onStoreDocument(buildData(document, 'user') as any);
+
+    // The empty doc was written (the clear persisted). The persisted content is
+    // the Y.Doc round-trip of the empty doc (attrs normalized), so compare
+    // against fromYdoc rather than the raw literal.
+    expect(pageRepo.updatePage).toHaveBeenCalledTimes(1);
+    const expectedEmpty = TiptapTransformer.fromYdoc(document, 'default');
+    expect(pageRepo.updatePage.mock.calls[0][0].content).toEqual(expectedEmpty);
+  });
+
+  // #251 — retry correctness: a transient DB failure on the FIRST attempt must
+  // not silently drop the clear. The intentional-clear flag is consumed ONCE
+  // before the retry loop, so when attempt 1's updatePage throws (tx rolls back,
+  // but the in-memory flag delete cannot roll back) the retry on attempt 2 still
+  // sees the clear as allowed and writes the empty doc. On the pre-fix code
+  // (consumeIntentionalClear called INSIDE the loop) attempt 1 consumed the flag,
+  // attempt 2 re-read it as absent and the empty-guard BLOCKED the write — so
+  // updatePage would be called once and the clear would be lost. This test fails
+  // on that ordering and passes after the hoist.
+  it('persists an intentional clear even when the first store attempt fails transiently (#251)', async () => {
+    const documentName = `page.${PAGE_ID}`;
+    const emptyDoc = { type: 'doc', content: [{ type: 'paragraph' }] };
+    const document = ydocFor(emptyDoc);
+    // The page stays non-empty in the DB across both attempts (the rolled-back
+    // first attempt never changed it), exactly the failure scenario the WARNING
+    // describes.
+    pageRepo.findById.mockResolvedValue({
+      ...persistedHumanPage('IGNORED'),
+      content: doc('IMPORTANT RICH CONTENT'),
+    });
+
+    let attempts = 0;
+    pageRepo.updatePage.mockImplementation(async () => {
+      attempts += 1;
+      if (attempts === 1) throw new Error('deadlock detected'); // transient
+      callOrder.push('updatePage');
+    });
+
+    // The client signalled a deliberate clear over the live connection.
+    await ext.onStateless({
+      connection: { readOnly: false } as any,
+      documentName,
+      document: document as any,
+      payload: JSON.stringify({ type: 'intentional-clear' }),
+    } as any);
+
+    await ext.onStoreDocument(buildData(document, 'user') as any);
+
+    // First attempt failed and rolled back; the retry still honoured the clear
+    // and wrote the empty doc (the clear survived the retry).
+    expect(pageRepo.updatePage).toHaveBeenCalledTimes(2);
+    const expectedEmpty = TiptapTransformer.fromYdoc(document, 'default');
+    expect(pageRepo.updatePage.mock.calls[1][0].content).toEqual(expectedEmpty);
+  });
+
+  // #251 — the signal is single-use: it is consumed by the first empty store,
+  // so a SECOND accidental empty (no fresh signal) is still blocked.
+  it('consumes the intentional-clear signal once; a later empty is blocked (#251)', async () => {
+    const documentName = `page.${PAGE_ID}`;
+    const emptyDoc = { type: 'doc', content: [{ type: 'paragraph' }] };
+    pageRepo.findById.mockResolvedValue({
+      ...persistedHumanPage('IGNORED'),
+      content: doc('IMPORTANT RICH CONTENT'),
+    });
+
+    await ext.onStateless({
+      connection: { readOnly: false } as any,
+      documentName,
+      document: ydocFor(emptyDoc) as any,
+      payload: JSON.stringify({ type: 'intentional-clear' }),
+    } as any);
+
+    // First empty store consumes the signal and writes.
+    await ext.onStoreDocument(buildData(ydocFor(emptyDoc), 'user') as any);
+    expect(pageRepo.updatePage).toHaveBeenCalledTimes(1);
+
+    // Re-arm findById to non-empty (as if content came back) and fire another
+    // empty store WITHOUT a new signal — the guard must block it.
+    pageRepo.updatePage.mockClear();
+    pageRepo.findById.mockResolvedValue({
+      ...persistedHumanPage('IGNORED'),
+      content: doc('IMPORTANT RICH CONTENT'),
+    });
+    await ext.onStoreDocument(buildData(ydocFor(emptyDoc), 'user') as any);
+    expect(pageRepo.updatePage).not.toHaveBeenCalled();
+  });
+
+  // #251 — a read-only connection cannot arm the clear, so its empty store is
+  // still blocked (defends the guard against a read-only spoof).
+  it('ignores an intentional-clear signal from a read-only connection (#251)', async () => {
+    const documentName = `page.${PAGE_ID}`;
+    const emptyDoc = { type: 'doc', content: [{ type: 'paragraph' }] };
+    const document = ydocFor(emptyDoc);
+    pageRepo.findById.mockResolvedValue({
+      ...persistedHumanPage('IGNORED'),
+      content: doc('IMPORTANT RICH CONTENT'),
+    });
+
+    await ext.onStateless({
+      connection: { readOnly: true } as any,
+      documentName,
+      document: document as any,
+      payload: JSON.stringify({ type: 'intentional-clear' }),
+    } as any);
+
+    await ext.onStoreDocument(buildData(document, 'user') as any);
+
+    expect(pageRepo.updatePage).not.toHaveBeenCalled();
+  });
+
+  // #251 — a non-empty store between the signal and the empty store drops the
+  // pending flag ("cleared then retyped" can't leave a usable signal behind).
+  it('drops a pending clear when a non-empty store intervenes (#251)', async () => {
+    const documentName = `page.${PAGE_ID}`;
+    const emptyDoc = { type: 'doc', content: [{ type: 'paragraph' }] };
+
+    await ext.onStateless({
+      connection: { readOnly: false } as any,
+      documentName,
+      document: ydocFor(emptyDoc) as any,
+      payload: JSON.stringify({ type: 'intentional-clear' }),
+    } as any);
+
+    // A non-empty store lands first → consumes/drops the stale flag.
+    pageRepo.findById.mockResolvedValue(persistedHumanPage('NEW HUMAN TEXT'));
+    await ext.onStoreDocument(
+      buildData(ydocFor(doc('NEW HUMAN TEXT')), 'user') as any,
     );
+    pageRepo.updatePage.mockClear();
+
+    // Now an empty store with no fresh signal must be blocked.
+    pageRepo.findById.mockResolvedValue({
+      ...persistedHumanPage('IGNORED'),
+      content: doc('IMPORTANT RICH CONTENT'),
+    });
+    await ext.onStoreDocument(buildData(ydocFor(emptyDoc), 'user') as any);
+    expect(pageRepo.updatePage).not.toHaveBeenCalled();
+  });
 
   // persist-1 — when every attempt fails the hook must NOT report a phantom
   // success: no "page.updated" badge broadcast and no history snapshot for

apps/server/src/collaboration/extensions/persistence.extension.ts

@@ -3,6 +3,7 @@ import {
   Extension,
   onChangePayload,
   onLoadDocumentPayload,
+  onStatelessPayload,
   onStoreDocumentPayload,
 } from '@hocuspocus/server';
 import * as Y from 'yjs';
@@ -41,6 +42,35 @@ import {
 } from '../constants';
 import { TransclusionService } from '../../core/page/transclusion/transclusion.service';
 
+/**
+ * #251 — wire format of the client→server stateless message that signals a
+ * deliberate page clear. The client (IntentionalClear editor extension) sends
+ * `{ type: INTENTIONAL_CLEAR_MESSAGE_TYPE }`; the document is taken from the
+ * connection, not the payload, so the signal cannot be aimed at another page.
+ */
+export const INTENTIONAL_CLEAR_MESSAGE_TYPE = 'intentional-clear';
+
+/**
+ * #251 — how long an intentional-clear signal stays "pending" before it is
+ * ignored. The signal is set on the clearing keystroke but consumed by the
+ * DEBOUNCED onStoreDocument, so the TTL must comfortably exceed the collab
+ * store debounce window (hocuspocus is configured with maxDebounce = 45s in
+ * collaboration.gateway.ts). 60s leaves a margin while keeping the window for a
+ * stale flag small; on top of the TTL, any non-empty store immediately drops a
+ * pending flag (see onStoreDocument), so a "cleared then retyped" sequence can
+ * never leave a usable flag behind.
+ *
+ * Known fail-safe limitation: the flag lives only in this node's process memory.
+ * If document ownership transfers to another node, or this node crashes/restarts,
+ * between the stateless signal (set on node A) and the debounced store, the
+ * in-memory flag is lost and the clear is silently NOT applied — the store-side
+ * empty-guard then reloads the document non-empty from the DB. This is
+ * deliberately fail-safe (a lost flag preserves content rather than destroying
+ * it), but it is a documented limitation, not a guarantee that every deliberate
+ * clear survives a node handoff.
+ */
+export const INTENTIONAL_CLEAR_TTL_MS = 60_000;
+
 /**
  * Resolve the provenance source for a coalesced snapshot.
  *
@@ -96,6 +126,13 @@ export class PersistenceExtension implements Extension {
   // coalescing window" per document and OR it across all edits in the window,
   // so the snapshot is marked 'agent' regardless of who wrote last.
   private agentTouched: Map<string, boolean> = new Map();
+  // #251 — per-document "intentional clear pending" flags. Keyed by
+  // documentName, value = expiry timestamp (ms). Set by onStateless when the
+  // client reports a deliberate clear; consumed once by the next
+  // onStoreDocument empty-guard branch. This is the per-EDIT channel the
+  // per-connection context cannot provide (a clear is an edit event, but the
+  // store is debounced and connection context is fixed at authentication).
+  private intentionalClear: Map<string, number> = new Map();
 
   constructor(
     private readonly pageRepo: PageRepo,
@@ -180,6 +217,19 @@ export class PersistenceExtension implements Extension {
       this.consumeAgentTouched(documentName),
       context?.actor,
     );
+    // #251 — consume the intentional-clear flag ONCE, BEFORE the retry loop
+    // (like consumeContributors / consumeAgentTouched above). consumeIntentional-
+    // Clear ALWAYS deletes the in-memory Map entry, but a tx rollback cannot
+    // un-delete it. Calling it INSIDE the loop meant: a clear armed for attempt 1
+    // was consumed there, attempt 1's updatePage threw a transient error and
+    // rolled back, then attempt 2 re-read non-empty content and saw the flag
+    // already gone — silently downgrading the retry into a BLOCKED write, so the
+    // user's deliberate clear was dropped. Hoisting makes the decision stable
+    // across every attempt. This single call also preserves the "a non-empty
+    // store drops a pending flag" semantics (the cleared-then-retyped case):
+    // every store consumes the flag here regardless of incoming emptiness, so a
+    // subsequent non-empty store can never leave a usable flag behind.
+    const allowIntentionalClear = this.consumeIntentionalClear(documentName);
 
     // Persist with a small bounded retry. The in-memory Y.Doc is the ONLY copy
     // of the latest edit until this hook returns: hocuspocus destroys/unloads the
@@ -210,6 +260,46 @@ export class PersistenceExtension implements Extension {
             return;
           }
 
+          // #206 persist-6 / #248 — store-side empty-guard. A momentarily-empty
+          // live Y.Doc (a client/agent glitch, a bad merge, a transclusion that
+          // emptied) must NOT overwrite non-empty persisted content. The LOAD
+          // path already guards emptiness (onLoadDocument only hydrates from db
+          // when the live doc isEmpty); the STORE path did not, so an empty
+          // serialization was written straight over the page, wiping it
+          // silently.
+          //
+          // #251 — the ONE legitimate empty-over-non-empty write is a user who
+          // deliberately clears the page. That intent arrives out-of-band as a
+          // stateless message, NOT from the doc content, which is why it cannot
+          // be spoofed for non-clear writes: the flag is only ever read on this
+          // empty-incoming branch, so the worst a forged signal can do is clear
+          // a page the connection may already edit. The flag was consumed ONCE
+          // before the retry loop (`allowIntentionalClear`) so the decision is
+          // stable across retries; a non-empty store still drops any pending
+          // flag via that same hoisted consume (a "cleared then retyped"
+          // sequence can't leave a usable one behind).
+          const incomingEmpty = isEmptyParagraphDoc(tiptapJson as any);
+          if (
+            incomingEmpty &&
+            page.content &&
+            !isEmptyParagraphDoc(page.content as any)
+          ) {
+            if (allowIntentionalClear) {
+              this.logger.debug(
+                `Intentional clear for ${pageId}: persisting empty doc over ` +
+                  `non-empty content (user-signalled)`,
+              );
+              // fall through — the empty write is allowed exactly once.
+            } else {
+              this.logger.warn(
+                `Skipping store for ${pageId}: empty live doc would overwrite ` +
+                  `non-empty persisted content`,
+              );
+              page = null;
+              return;
+            }
+          }
+
           let contributorIds = undefined;
           try {
             const existingContributors = page.contributorIds || [];
@@ -345,6 +435,37 @@ export class PersistenceExtension implements Extension {
     }
   }
 
+  /**
+   * #251 — receive the client's deliberate-clear signal. Records a short-lived,
+   * single-use pending flag for the originating document so the next
+   * onStoreDocument may let one empty-over-non-empty write through the guard.
+   *
+   * Hardening: read-only connections cannot arm the flag, and the document is
+   * taken from the connection (`data.documentName`), never the payload, so a
+   * client cannot target a page it isn't editing. The flag only ever RELAXES
+   * the guard for an empty write (a clear); it can never force or alter a
+   * non-empty write, so it is not a guard bypass for normal content.
+   */
+  async onStateless(data: onStatelessPayload) {
+    const { connection, documentName, payload } = data;
+
+    if (connection?.readOnly) return;
+
+    let message: { type?: string } | undefined;
+    try {
+      message = JSON.parse(payload);
+    } catch {
+      return; // unrelated / malformed stateless message
+    }
+
+    if (message?.type !== INTENTIONAL_CLEAR_MESSAGE_TYPE) return;
+
+    this.intentionalClear.set(
+      documentName,
+      Date.now() + INTENTIONAL_CLEAR_TTL_MS,
+    );
+  }
+
   async onChange(data: onChangePayload) {
     const documentName = data.documentName;
     const userId = data.context?.user?.id;
@@ -368,6 +489,7 @@ export class PersistenceExtension implements Extension {
     const documentName = data.documentName;
     this.contributors.delete(documentName);
     this.agentTouched.delete(documentName);
+    this.intentionalClear.delete(documentName);
   }
 
   private consumeContributors(documentName: string): string[] {
@@ -385,6 +507,18 @@ export class PersistenceExtension implements Extension {
     return touched;
   }
 
+  /**
+   * #251 — read and clear the intentional-clear flag for this document. Returns
+   * true only if a flag was pending AND still within its TTL. Always deletes the
+   * entry so the signal is strictly single-use (one clear → one allowed empty
+   * write); an expired flag is treated as absent (guard still blocks).
+   */
+  private consumeIntentionalClear(documentName: string): boolean {
+    const expiry = this.intentionalClear.get(documentName);
+    this.intentionalClear.delete(documentName);
+    return expiry !== undefined && Date.now() < expiry;
+  }
+
   private async enqueuePageHistory(
     page: Page,
     lastUpdatedSource: string,