M6: version history — note revisions + restore

A note's title+body is snapshotted on each edit that changes either, so an accidental overwrite can be viewed and restored (task 1906). Underwrites 'dump freely, nothing is lost'.

Backend: note_revisions table (migration 0014) + NoteRevision model; update_note records a revision of the PRE-edit state whenever title/body changes; GET /api/notes/<id>/revisions (newest 50) and POST /api/notes/<id>/revisions/<rev_id>/restore (snapshots the current state first so restore is itself undoable, then applies the revision with the usual title/body ripple — display name, links, #tags, backlinks). Title+body only in v1.

Frontend: a History toggle in the modal editor opens a panel of past versions (timestamp + preview) with per-row Restore. Store gains fetchRevisions/restoreRevision.

Migration 0014 runs on deploy; DB behavior operator-verified (no Postgres CI lane).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm

src/thoughtsync/models/all.py

@@ -3,4 +3,15 @@
 Imported for side effects only (model registration on Base.metadata).
 """
 
-from . import group, label, note, note_attachment, note_item, note_link, settings, share, user  # noqa: F401
+from . import (  # noqa: F401
+    group,
+    label,
+    note,
+    note_attachment,
+    note_item,
+    note_link,
+    note_revision,
+    settings,
+    share,
+    user,
+)

src/thoughtsync/models/note_revision.py

@@ -0,0 +1,27 @@
+from __future__ import annotations
+
+import uuid
+from datetime import datetime
+
+from sqlalchemy import DateTime, ForeignKey, Index, Text, func
+from sqlalchemy.dialects.postgresql import UUID
+from sqlalchemy.orm import Mapped, mapped_column
+
+from . import Base
+
+
+class NoteRevision(Base):
+    """A point-in-time snapshot of a note's title+body, written on each edit that
+    changes either — so an accidental overwrite can be viewed and restored. Only
+    title+body are versioned in v1 (not items/attachments/labels)."""
+
+    __tablename__ = "note_revisions"
+    __table_args__ = (Index("ix_note_revisions_note_created", "note_id", "created_at"),)
+
+    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    note_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True), ForeignKey("notes.id", ondelete="CASCADE"), nullable=False
+    )
+    title: Mapped[str | None] = mapped_column(Text(), nullable=True)
+    body: Mapped[str] = mapped_column(Text(), nullable=False, server_default="")
+    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False, server_default=func.now())

src/thoughtsync/notes.py

@@ -17,6 +17,7 @@ from .models.note import NOTE_COLORS, Note
 from .models.note_attachment import NoteAttachment
 from .models.note_item import NoteItem
 from .models.note_link import NoteLink
+from .models.note_revision import NoteRevision
 
 ALLOWED_IMAGE_MIMES = {"image/png": ".png", "image/jpeg": ".jpg", "image/gif": ".gif", "image/webp": ".webp"}
 
@@ -543,6 +544,8 @@ async def update_note(note_id: str):
         if note is None:
             return jsonify({"error": "not found"}), 404
         old_display = note.display_title
+        old_title = note.title
+        old_body = note.body
         if "title" in data:
             title = data["title"] if isinstance(data["title"], str) else ""
             note.title = title.strip() or None
@@ -576,6 +579,69 @@ async def update_note(note_id: str):
         # repoints inbound [[Old Name]] references so backlinks survive (skip pure
         # case/whitespace changes, which still resolve).
         new_display = note.display_title
+        if old_display and new_display and old_display.strip().lower() != new_display.strip().lower():
+            await _rename_inbound_links(db, note, old_display, new_display)
+        # Version history: snapshot the PRE-edit title+body whenever either changed.
+        if note.title != old_title or note.body != old_body:
+            db.add(NoteRevision(note_id=note.id, title=old_title, body=old_body))
+        await db.commit()
+        await db.refresh(note)
+        return jsonify(await _serialize_note(db, note))
+
+
+def _serialize_revision(rev: NoteRevision) -> dict:
+    return {
+        "id": str(rev.id),
+        "title": rev.title,
+        "body": rev.body,
+        "created_at": rev.created_at.isoformat() if rev.created_at else None,
+    }
+
+
+@bp.get("/<note_id>/revisions")
+@login_required
+async def list_revisions(note_id: str):
+    async with session_scope() as db:
+        note = await _get_owned(db, note_id)
+        if note is None:
+            return jsonify({"error": "not found"}), 404
+        rows = (
+            await db.scalars(
+                select(NoteRevision)
+                .where(NoteRevision.note_id == note.id)
+                .order_by(NoteRevision.created_at.desc())
+                .limit(50)
+            )
+        ).all()
+        return jsonify({"revisions": [_serialize_revision(r) for r in rows]})
+
+
+@bp.post("/<note_id>/revisions/<rev_id>/restore")
+@login_required
+async def restore_revision(note_id: str, rev_id: str):
+    try:
+        rid = uuid.UUID(rev_id)
+    except (ValueError, TypeError):
+        return jsonify({"error": "not found"}), 404
+    async with session_scope() as db:
+        note = await _get_owned(db, note_id)
+        if note is None:
+            return jsonify({"error": "not found"}), 404
+        rev = await db.scalar(select(NoteRevision).where(NoteRevision.id == rid, NoteRevision.note_id == note.id))
+        if rev is None:
+            return jsonify({"error": "not found"}), 404
+        if note.title == rev.title and note.body == rev.body:
+            return jsonify(await _serialize_note(db, note))  # already at this version — no-op
+        # Snapshot the CURRENT state first, so restoring is itself undoable, then apply
+        # the revision — with the same title/body ripple as a normal edit.
+        old_display = note.display_title
+        db.add(NoteRevision(note_id=note.id, title=note.title, body=note.body))
+        note.title = rev.title
+        note.body = rev.body
+        note.display_title = derive_display_title(note.title, note.body)
+        await _rewrite_links(db, note)
+        await _reconcile_tags(db, note)
+        new_display = note.display_title
         if old_display and new_display and old_display.strip().lower() != new_display.strip().lower():
             await _rename_inbound_links(db, note, old_display, new_display)
         await db.commit()