diff --git a/src/thoughtsync/notes.py b/src/thoughtsync/notes.py
index 733afd1..0e73a40 100644
--- a/src/thoughtsync/notes.py
+++ b/src/thoughtsync/notes.py
@@ -19,6 +19,7 @@ from .auth import login_required
 from .common import coerce_bool, parse_dt
 from .config import Config
 from .db import session_scope
+from .responses import json_error, not_found, parse_uuid
 from .settings import get_setting
 from .unfurl import UnfurlError, unfurl
 from .models.label import Label, NoteLabel
@@ -237,9 +238,8 @@ async def _serialize_notes(db, notes: list) -> list:
 
 async def _get_owned(db, note_id: str) -> Note | None:
     """Fetch a note the current user OWNS (mutations are owner-only in M1/M2)."""
-    try:
-        nid = uuid.UUID(note_id)
-    except (ValueError, TypeError):
+    nid = parse_uuid(note_id)
+    if nid is None:
         return None
     return await db.scalar(select(Note).where(Note.id == nid, Note.owner_id == g.user_id))
 
@@ -369,7 +369,7 @@ def next_occurrence(remind_at: datetime, recurrence: str, after: datetime) -> da
 async def list_notes():
     filter_name = request.args.get("filter", "active")
     if filter_name not in VALID_FILTERS:
-        return jsonify({"error": "invalid filter"}), 400
+        return json_error("invalid filter", 400)
     # Combinable facet filters (all optional, AND-ed together) — the rich-search /
     # saved-filter lens. Multiple ?label= narrow to notes carrying ALL of them.
     label_params = request.args.getlist("label")
@@ -390,18 +390,17 @@ async def list_notes():
         stmt = select(Note).where(visible_to_user("note", Note.owner_id, Note.id, g.user_id))
         stmt = apply_filter(stmt, filter_name)
         for raw_label in label_params:
-            try:
-                lid = uuid.UUID(raw_label)
-            except (ValueError, TypeError):
-                return jsonify({"error": "invalid label"}), 400
+            lid = parse_uuid(raw_label)
+            if lid is None:
+                return json_error("invalid label", 400)
             stmt = stmt.where(Note.id.in_(select(NoteLabel.note_id).where(NoteLabel.label_id == lid)))
         if color is not None:
             if color not in NOTE_COLORS:
-                return jsonify({"error": "invalid color"}), 400
+                return json_error("invalid color", 400)
             stmt = stmt.where(Note.color == color)
         if kind is not None:
             if kind not in ("text", "list"):
-                return jsonify({"error": "invalid kind"}), 400
+                return json_error("invalid kind", 400)
             stmt = stmt.where(Note.kind == kind)
         if has_reminder:
             stmt = stmt.where(Note.remind_at.is_not(None))
@@ -410,12 +409,12 @@ async def list_notes():
         if after_param:
             after_dt = parse_dt(after_param)
             if after_dt is None:
-                return jsonify({"error": "invalid created_after"}), 400
+                return json_error("invalid created_after", 400)
             stmt = stmt.where(Note.created_at >= after_dt)
         if before_param:
             before_dt = parse_dt(before_param)
             if before_dt is None:
-                return jsonify({"error": "invalid created_before"}), 400
+                return json_error("invalid created_before", 400)
             stmt = stmt.where(Note.created_at < before_dt)
         if query_text:
             # Full-text match over title+body (generated tsvector, migration 0005),
@@ -482,7 +481,7 @@ async def complete_reminder(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
+            return not_found()
         if note.remind_at is not None and note.recurrence in REMINDER_RECURRENCES:
             note.remind_at = next_occurrence(note.remind_at, note.recurrence, datetime.now(timezone.utc))
         else:
@@ -505,7 +504,7 @@ async def snooze_reminder(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
+            return not_found()
         note.remind_at = datetime.now(timezone.utc) + timedelta(minutes=minutes)
         await db.commit()
         return jsonify(await _serialize_note(db, note))
@@ -877,20 +876,19 @@ async def import_notes():
     files = await request.files
     upload = files.get("file")
     if upload is None:
-        return jsonify({"error": "no file provided"}), 400
+        return json_error("no file provided", 400)
     raw = upload.stream.read()
     if not raw:
-        return jsonify({"error": "empty upload"}), 400
+        return json_error("empty upload", 400)
     try:
         zf = zipfile.ZipFile(io.BytesIO(raw))
     except zipfile.BadZipFile:
-        return jsonify({"error": "that file isn't a valid .zip archive"}), 400
-
+        return json_error("that file isn't a valid .zip archive", 400)
     specs, source = _read_import_specs(zf)
     if not specs:
-        return jsonify(
-            {"error": "no importable notes found — expected a ThoughtSync export or a Google Keep Takeout zip"}
-        ), 400
+        return json_error(
+            "no importable notes found — expected a ThoughtSync export or a Google Keep Takeout zip", 400
+        )
 
     imported = 0
     skipped = 0
@@ -965,16 +963,15 @@ async def link_search():
 @bp.get("/<note_id>/backlinks")
 @login_required
 async def note_backlinks(note_id: str):
-    try:
-        nid = uuid.UUID(note_id)
-    except (ValueError, TypeError):
-        return jsonify({"error": "not found"}), 404
+    nid = parse_uuid(note_id)
+    if nid is None:
+        return not_found()
     async with session_scope() as db:
         note = await db.scalar(
             select(Note).where(Note.id == nid, visible_to_user("note", Note.owner_id, Note.id, g.user_id))
         )
         if note is None:
-            return jsonify({"error": "not found"}), 404
+            return not_found()
         if not note.display_title:
             return jsonify({"backlinks": []})
         norm = note.display_title.strip().lower()
@@ -1005,13 +1002,13 @@ async def reorder_notes():
     data = await request.get_json(silent=True) or {}
     ids = data.get("ids")
     if not isinstance(ids, list):
-        return jsonify({"error": "ids must be a list"}), 400
+        return json_error("ids must be a list", 400)
     parsed: list = []
     for rid in ids:
-        try:
-            parsed.append(uuid.UUID(str(rid)))
-        except (ValueError, TypeError):
-            return jsonify({"error": "invalid id"}), 400
+        parsed_id = parse_uuid(rid)
+        if parsed_id is None:
+            return json_error("invalid id", 400)
+        parsed.append(parsed_id)
     async with session_scope() as db:
         owned = {
             n.id: n
@@ -1038,9 +1035,9 @@ async def create_note():
     item_texts = parse_list_items(data.get("items")) if kind == "list" else []
     if kind == "list":
         if not (title.strip() or item_texts):
-            return jsonify({"error": "note is empty"}), 400
+            return json_error("note is empty", 400)
     elif is_empty_note(title, body):
-        return jsonify({"error": "note is empty"}), 400
+        return json_error("note is empty", 400)
     async with session_scope() as db:
         # New notes go to the top of the manual order.
         max_pos = await db.scalar(
@@ -1072,16 +1069,15 @@ async def create_note():
 @bp.get("/<note_id>")
 @login_required
 async def get_note(note_id: str):
-    try:
-        nid = uuid.UUID(note_id)
-    except (ValueError, TypeError):
-        return jsonify({"error": "not found"}), 404
+    nid = parse_uuid(note_id)
+    if nid is None:
+        return not_found()
     async with session_scope() as db:
         note = await db.scalar(
             select(Note).where(Note.id == nid, visible_to_user("note", Note.owner_id, Note.id, g.user_id))
         )
         if note is None:
-            return jsonify({"error": "not found"}), 404
+            return not_found()
         return jsonify(await _serialize_note(db, note))
 
 
@@ -1092,7 +1088,7 @@ async def update_note(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
+            return not_found()
         old_display = note.display_title
         old_title = note.title
         old_body = note.body
@@ -1117,7 +1113,7 @@ async def update_note(note_id: str):
             else:
                 remind_dt = parse_dt(raw)
                 if remind_dt is None:
-                    return jsonify({"error": "invalid remind_at"}), 400
+                    return json_error("invalid remind_at", 400)
                 note.remind_at = remind_dt
         if "recurrence" in data:
             note.recurrence = normalize_recurrence(data["recurrence"])
@@ -1157,7 +1153,7 @@ 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
+            return not_found()
         rows = (
             await db.scalars(
                 select(NoteRevision)
@@ -1172,17 +1168,16 @@ async def list_revisions(note_id: str):
 @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
+    rid = parse_uuid(rev_id)
+    if rid is None:
+        return not_found()
     async with session_scope() as db:
         note = await _get_owned(db, note_id)
         if note is None:
-            return jsonify({"error": "not found"}), 404
+            return not_found()
         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
+            return not_found()
         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
@@ -1208,17 +1203,17 @@ async def set_note_labels(note_id: str):
     data = await request.get_json(silent=True) or {}
     raw_ids = data.get("label_ids")
     if not isinstance(raw_ids, list):
-        return jsonify({"error": "label_ids must be a list"}), 400
+        return json_error("label_ids must be a list", 400)
     label_ids: list = []
     for rid in raw_ids:
-        try:
-            label_ids.append(uuid.UUID(str(rid)))
-        except (ValueError, TypeError):
-            return jsonify({"error": "invalid label id"}), 400
+        parsed_label = parse_uuid(rid)
+        if parsed_label is None:
+            return json_error("invalid label id", 400)
+        label_ids.append(parsed_label)
     async with session_scope() as db:
         note = await _get_owned(db, note_id)
         if note is None:
-            return jsonify({"error": "not found"}), 404
+            return not_found()
         owned: set = set()
         if label_ids:
             owned = set(
@@ -1244,9 +1239,8 @@ async def set_note_labels(note_id: str):
 
 
 async def _get_item(db, note: Note, item_id: str) -> NoteItem | None:
-    try:
-        iid = uuid.UUID(item_id)
-    except (ValueError, TypeError):
+    iid = parse_uuid(item_id)
+    if iid is None:
         return None
     return await db.scalar(select(NoteItem).where(NoteItem.id == iid, NoteItem.note_id == note.id))
 
@@ -1259,7 +1253,7 @@ async def add_item(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
+            return not_found()
         max_pos = await db.scalar(
             select(func.coalesce(func.max(NoteItem.position), -1)).where(NoteItem.note_id == note.id)
         )
@@ -1275,10 +1269,10 @@ async def update_item(note_id: str, item_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
+            return not_found()
         item = await _get_item(db, note, item_id)
         if item is None:
-            return jsonify({"error": "not found"}), 404
+            return not_found()
         if "text" in data and isinstance(data["text"], str):
             item.text = data["text"]
         if "checked" in data:
@@ -1293,10 +1287,10 @@ async def delete_item(note_id: str, item_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
+            return not_found()
         item = await _get_item(db, note, item_id)
         if item is None:
-            return jsonify({"error": "not found"}), 404
+            return not_found()
         await db.delete(item)
         await db.commit()
         return jsonify(await _serialize_note(db, note))
@@ -1308,11 +1302,11 @@ async def reorder_items(note_id: str):
     data = await request.get_json(silent=True) or {}
     order = data.get("item_ids")
     if not isinstance(order, list):
-        return jsonify({"error": "item_ids must be a list"}), 400
+        return json_error("item_ids must be a list", 400)
     async with session_scope() as db:
         note = await _get_owned(db, note_id)
         if note is None:
-            return jsonify({"error": "not found"}), 404
+            return not_found()
         existing = {
             str(i.id): i for i in (await db.scalars(select(NoteItem).where(NoteItem.note_id == note.id))).all()
         }
@@ -1351,11 +1345,11 @@ async def upload_attachment(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
+            return not_found()
         files = await request.files
         upload = files.get("file")
         if upload is None:
-            return jsonify({"error": "no file provided"}), 400
+            return json_error("no file provided", 400)
         # Any file type is allowed — images render inline, everything else downloads.
         mime = (upload.content_type or "application/octet-stream").split(";")[0].strip().lower()
         filename = _safe_filename(upload.filename)
@@ -1366,10 +1360,10 @@ async def upload_attachment(note_id: str):
         raw_id = (form.get("id") or "").strip()
         att_id = uuid.uuid4()
         if raw_id:
-            try:
-                att_id = uuid.UUID(raw_id)
-            except (ValueError, TypeError):
-                return jsonify({"error": "invalid attachment id"}), 400
+            parsed_att = parse_uuid(raw_id)
+            if parsed_att is None:
+                return json_error("invalid attachment id", 400)
+            att_id = parsed_att
             existing = await db.scalar(
                 select(NoteAttachment).where(NoteAttachment.id == att_id, NoteAttachment.note_id == note.id)
             )
@@ -1378,7 +1372,7 @@ async def upload_attachment(note_id: str):
         raw = upload.stream.read()
         max_mb = int(await get_setting(db, "max_attachment_mb"))
         if len(raw) > max_mb * 1024 * 1024:
-            return jsonify({"error": f"file is too large (max {max_mb} MB)"}), 413
+            return json_error(f"file is too large (max {max_mb} MB)", 413)
         rel = os.path.join(str(note.id), f"{att_id}{ext}")
         dest = Config.media_root() / rel
         dest.parent.mkdir(parents=True, exist_ok=True)
@@ -1401,26 +1395,25 @@ async def upload_attachment(note_id: str):
 @bp.get("/<note_id>/attachments/<att_id>")
 @login_required
 async def get_attachment(note_id: str, att_id: str):
-    try:
-        nid = uuid.UUID(note_id)
-        aid = uuid.UUID(att_id)
-    except (ValueError, TypeError):
-        return jsonify({"error": "not found"}), 404
+    nid = parse_uuid(note_id)
+    aid = parse_uuid(att_id)
+    if nid is None or aid is None:
+        return not_found()
     async with session_scope() as db:
         # Owner OR shared may view (rule 47).
         note = await db.scalar(
             select(Note).where(Note.id == nid, visible_to_user("note", Note.owner_id, Note.id, g.user_id))
         )
         if note is None:
-            return jsonify({"error": "not found"}), 404
+            return not_found()
         att = await db.scalar(select(NoteAttachment).where(NoteAttachment.id == aid, NoteAttachment.note_id == nid))
         if att is None:
-            return jsonify({"error": "not found"}), 404
+            return not_found()
         mime = att.mime
         filename = att.filename or os.path.basename(att.path)
         file_path = Config.media_root() / att.path
     if not file_path.is_file():
-        return jsonify({"error": "not found"}), 404
+        return not_found()
     response = await send_file(str(file_path), mimetype=mime)
     response.headers["X-Content-Type-Options"] = "nosniff"
     response.headers["Cache-Control"] = "private, max-age=86400"
@@ -1433,17 +1426,16 @@ async def get_attachment(note_id: str, att_id: str):
 @bp.delete("/<note_id>/attachments/<att_id>")
 @login_required
 async def delete_attachment(note_id: str, att_id: str):
-    try:
-        aid = uuid.UUID(att_id)
-    except (ValueError, TypeError):
-        return jsonify({"error": "not found"}), 404
+    aid = parse_uuid(att_id)
+    if aid is None:
+        return not_found()
     async with session_scope() as db:
         note = await _get_owned(db, note_id)
         if note is None:
-            return jsonify({"error": "not found"}), 404
+            return not_found()
         att = await db.scalar(select(NoteAttachment).where(NoteAttachment.id == aid, NoteAttachment.note_id == note.id))
         if att is None:
-            return jsonify({"error": "not found"}), 404
+            return not_found()
         file_path = Config.media_root() / att.path
         await db.delete(att)
         await db.commit()
@@ -1463,22 +1455,22 @@ async def unfurl_link(note_id: str):
     data = await request.get_json(silent=True) or {}
     url = (data.get("url") or "").strip()
     if not url:
-        return jsonify({"error": "url is required"}), 400
+        return json_error("url is required", 400)
     async with session_scope() as db:
         note = await _get_owned(db, note_id)
         if note is None:
-            return jsonify({"error": "not found"}), 404
+            return not_found()
         if not await get_setting(db, "enable_url_unfurl"):
-            return jsonify({"error": "link previews are disabled"}), 403
+            return json_error("link previews are disabled", 403)
     # Fetch OUTSIDE the DB session — network IO shouldn't hold a connection.
     try:
         preview = await unfurl(url)
     except UnfurlError as e:
-        return jsonify({"error": str(e)}), 502
+        return json_error(str(e), 502)
     async with session_scope() as db:
         note = await _get_owned(db, note_id)
         if note is None:
-            return jsonify({"error": "not found"}), 404
+            return not_found()
         # Keyed by the ORIGINAL pasted url (what the note body contains, so the client
         # matches it) — re-unfurling the same link updates the cached preview in place.
         row = await db.scalar(
@@ -1498,19 +1490,18 @@ async def unfurl_link(note_id: str):
 @bp.delete("/<note_id>/previews/<preview_id>")
 @login_required
 async def delete_preview(note_id: str, preview_id: str):
-    try:
-        pid = uuid.UUID(preview_id)
-    except (ValueError, TypeError):
-        return jsonify({"error": "not found"}), 404
+    pid = parse_uuid(preview_id)
+    if pid is None:
+        return not_found()
     async with session_scope() as db:
         note = await _get_owned(db, note_id)
         if note is None:
-            return jsonify({"error": "not found"}), 404
+            return not_found()
         row = await db.scalar(
             select(NoteLinkPreview).where(NoteLinkPreview.id == pid, NoteLinkPreview.note_id == note.id)
         )
         if row is None:
-            return jsonify({"error": "not found"}), 404
+            return not_found()
         await db.delete(row)
         await db.commit()
         return jsonify(await _serialize_note(db, note))
@@ -1522,7 +1513,7 @@ async def trash_note(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
+            return not_found()
         note.deleted_at = datetime.now(timezone.utc)
         await db.commit()
         await db.refresh(note)
@@ -1535,7 +1526,7 @@ async def restore_note(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
+            return not_found()
         note.deleted_at = None
         await db.commit()
         await db.refresh(note)
@@ -1548,9 +1539,9 @@ async def delete_note(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
+            return not_found()
         if note.deleted_at is None:
-            return jsonify({"error": "note must be trashed before permanent delete"}), 409
+            return json_error("note must be trashed before permanent delete", 409)
         await db.delete(note)
         await db.commit()
         return jsonify({"ok": True})
diff --git a/src/thoughtsync/responses.py b/src/thoughtsync/responses.py
new file mode 100644
index 0000000..f464377
--- /dev/null
+++ b/src/thoughtsync/responses.py
@@ -0,0 +1,28 @@
+from __future__ import annotations
+
+import uuid
+
+from quart import jsonify
+
+# The app's single JSON error shape + the two guards that pair with it, so every
+# blueprint returns errors and parses path ids the same way instead of hand-building
+# `jsonify({"error": ...}), code` and try/except uuid blocks at ~35 call sites.
+
+
+def json_error(message: str, status: int):
+    """A JSON error body + status: ({"error": message}, status)."""
+    return jsonify({"error": message}), status
+
+
+def not_found():
+    """404 with the standard body — by far the most common error in the note routes."""
+    return json_error("not found", 404)
+
+
+def parse_uuid(raw: object) -> uuid.UUID | None:
+    """Parse a path/body UUID, returning None on anything malformed. Pair with
+    not_found() for the ubiquitous 'bad id in the URL → 404' guard."""
+    try:
+        return uuid.UUID(str(raw))
+    except (ValueError, TypeError):
+        return None