fix(youtube): a refused YouTube action answers a 422 that says what to do

The two manual syncs (subscriptions import, playlist pull) had no YouTubeError
handler, so a quota, token or transport failure was a raw 500 and the blocking
"Server error" dialog (E9 F1). The other YouTube routes answered either the
upstream's English or a playlist-scoped "youtube_failed".

One helper, routes/_common.youtube_refusal: 422 {code: "youtube", reason} with
the reason sorted by what the user can do — quota (wait for the reset),
reconnect (the token step refused), unavailable (retry). Used by every route
that surfaces a YouTube failure; localizeDetail translates it.

"Reconnect" had no path: a grant Google revoked still read as granted, so
Settings and the wizard offered no connect button while every call failed.
An invalid_grant from the token endpoint now clears the stored grant.

backend/app/routes/_common.py

@@ -13,6 +13,7 @@ from sqlalchemy.orm import Session
 
 from app.db import Base
 from app.models import User
+from app.youtube.client import YouTubeError, refusal_reason
 
 M = TypeVar("M", bound=Base)
 
@@ -51,3 +52,12 @@ def owned_or_404(
     if getattr(obj, owner_attr) != user.id:
         raise not_found(what)
     return obj
+
+
+def youtube_refusal(exc: YouTubeError) -> HTTPException:
+    """The answer to an action YouTube refused: a 422 whose reason the UI translates
+    (`errors.youtube.<reason>`). One definition, because the routes had grown three shapes of it —
+    a bare English string quoting the upstream message, a playlist-scoped reason, and nothing at
+    all (a raw 500 from the manual syncs). The upstream failure is already logged where it
+    happened (`youtube.api.error`)."""
+    return HTTPException(status_code=422, detail={"code": "youtube", "reason": refusal_reason(exc)})

backend/app/routes/channels.py

@@ -25,7 +25,7 @@ from app.models import (
     User,
     Video,
 )
-from app.routes._common import get_or_404, not_found, owned_or_404
+from app.routes._common import get_or_404, not_found, owned_or_404, youtube_refusal
 from app.sync.explore import explore_ingest_page
 from app.sync.runner import backfill_channel_now, run_recent_backfill
 from app.sync.subscriptions import apply_channel_details
@@ -424,7 +424,7 @@ def explore_channel(
                 channel = db.get(Channel, channel_id)
             result = explore_ingest_page(db, yt, channel, page_token)
     except YouTubeError as exc:
-        raise HTTPException(status_code=422, detail=f"YouTube couldn't load this channel: {exc}")
+        raise youtube_refusal(exc)
     return {
         "channel_id": channel_id,
         "ingested": result["ingested"],
@@ -583,9 +583,7 @@ def subscribe(
             if "subscriptionDuplicate" in exc.reason.split(","):
                 yt_sub_id = ""
             else:
-                raise HTTPException(
-                    status_code=422, detail=f"YouTube couldn't subscribe you: {exc}"
-                )
+                raise youtube_refusal(exc)
         # Enrich a stub channel (title/thumbnail/subscriber count) so it shows up properly right
         # away, on BOTH the normal and the desync path — a resurfaced stub still needs metadata to
         # render. Keep the client open (we're still inside the `with`); a metadata failure here
@@ -649,7 +647,7 @@ def unsubscribe(
     except YouTubeError as exc:
         # 422 (a real, explainable error → speaking modal), not 502 which the client treats as
         # a transient "connection lost" gateway blip.
-        raise HTTPException(status_code=422, detail=f"YouTube couldn't unsubscribe you: {exc}")
+        raise youtube_refusal(exc)
     db.delete(sub)
     db.commit()
     return {"unsubscribed": channel_id}

backend/app/routes/feed.py

@@ -29,7 +29,7 @@ from app.models import (
     Video,
     VideoState,
 )
-from app.routes._common import get_or_404
+from app.routes._common import get_or_404, youtube_refusal
 from app.sync.videos import parse_iso8601_duration
 from app.utils import iso
 from app.youtube.client import YouTubeClient, YouTubeError
@@ -411,7 +411,7 @@ def get_video_detail(
         ):
             items = yt.get_videos([video_id])
     except YouTubeError as exc:
-        raise HTTPException(status_code=422, detail=f"YouTube lookup failed: {exc}")
+        raise youtube_refusal(exc)
     if not items:
         raise HTTPException(status_code=404, detail="Unknown video")
 

backend/app/routes/playlists.py

@@ -23,7 +23,7 @@ from app.sync.playlists import (
     sync_user_playlists,
 )
 from app.ratelimit import RateLimiter
-from app.routes._common import get_or_404, owned_or_404
+from app.routes._common import get_or_404, owned_or_404, youtube_refusal
 from app.youtube.client import YouTubeClient, YouTubeError
 
 router = APIRouter(prefix="/api/playlists", tags=["playlists"])
@@ -322,8 +322,12 @@ def sync_youtube(
     if not has_read_scope(user):
         raise _refused(403, "youtube_read_scope")
     _check_pull_cooldown(user)
-    with quota.attribute(user.id, quota.QuotaAction.PLAYLISTS_PULL):
-        return sync_user_playlists(db, user)
+    try:
+        with quota.attribute(user.id, quota.QuotaAction.PLAYLISTS_PULL):
+            return sync_user_playlists(db, user)
+    except YouTubeError as exc:
+        db.rollback()
+        raise youtube_refusal(exc)
 
 
 @router.post("/{playlist_id}/revert-youtube")
@@ -344,9 +348,9 @@ def revert_youtube(
     try:
         with quota.attribute(user.id, quota.QuotaAction.PLAYLISTS_PULL):
             return repull_playlist(db, user, pl)
-    except YouTubeError:
+    except YouTubeError as exc:
         db.rollback()
-        raise _refused(422, "youtube_failed")
+        raise youtube_refusal(exc)
 
 
 def _pushable(db: Session, user: User, playlist_id: int) -> Playlist:
@@ -371,8 +375,8 @@ def push_plan(
     try:
         with quota.attribute(user.id, quota.QuotaAction.PLAYLISTS_PUSH):
             plan = plan_merge(db, user, pl)
-    except YouTubeError:
-        raise _refused(422, "youtube_failed")
+    except YouTubeError as exc:
+        raise youtube_refusal(exc)
     plan["remaining_today"] = quota.remaining_today(db)
     plan["affordable"] = plan["units_estimate"] <= plan["remaining_today"]
     return plan
@@ -404,9 +408,9 @@ def push(
             if plan["units_estimate"] > quota.remaining_today(db):
                 raise _refused(429, "quota_exceeded")
             return merge_playlist(db, user, pl, live=live)
-    except YouTubeError:
+    except YouTubeError as exc:
         db.rollback()
-        raise _refused(422, "youtube_failed")
+        raise youtube_refusal(exc)
 
 
 @router.get("/{playlist_id}")
@@ -496,8 +500,8 @@ def delete_playlist(
             with quota.attribute(user.id, quota.QuotaAction.PLAYLISTS_DELETE):
                 with YouTubeClient(db, user) as yt:
                     yt.delete_playlist(pl.yt_playlist_id)
-        except YouTubeError:
-            raise _refused(422, "youtube_failed")
+        except YouTubeError as exc:
+            raise youtube_refusal(exc)
     db.delete(pl)  # items cascade
     db.commit()
     return {"deleted": playlist_id}

backend/app/routes/sync.py

@@ -7,10 +7,12 @@ from app.audit import AuditAction
 from app.auth import admin_user, current_user, has_read_scope, require_human
 from app.db import get_db
 from app.models import Channel, Subscription, User, Video
+from app.routes._common import youtube_refusal
 from app.ratelimit import RateLimiter
 from app.sync.runner import estimate_deep_backfill
 from app.sync.subscriptions import import_subscriptions
 from app.scheduler import running_job_ids
+from app.youtube.client import YouTubeError
 
 router = APIRouter(prefix="/api/sync", tags=["sync"])
 
@@ -32,8 +34,14 @@ def sync_subscriptions(user: User = Depends(require_human), db: Session = Depend
         )
     if not _sync_limiter.allow(str(user.id)):
         raise HTTPException(status_code=429, detail={"code": "sync_cooldown"})
-    with quota.measured(db, user.id, quota.QuotaAction.SUBSCRIPTIONS_PULL) as m:
-        result = import_subscriptions(db, user)
+    try:
+        with quota.measured(db, user.id, quota.QuotaAction.SUBSCRIPTIONS_PULL) as m:
+            result = import_subscriptions(db, user)
+    except YouTubeError as exc:
+        # The onboarding wizard's first call: an unguarded failure here was a raw 500 and the
+        # blocking "Server error" dialog, with nothing the user could act on (E9 F1).
+        db.rollback()
+        raise youtube_refusal(exc)
     result["quota_used_estimate"] = m.used
     result["quota_remaining_today"] = m.remaining
     return result

backend/app/youtube/client.py

@@ -9,6 +9,7 @@ uses OAuth.
 import logging
 from collections.abc import Iterator
 from datetime import datetime, timedelta, timezone
+from typing import Literal
 
 import httpx
 
@@ -108,6 +109,22 @@ def is_quota_refusal(exc: YouTubeError) -> bool:
     return any(r in _QUOTA_REASONS for r in exc.reason.split(","))
 
 
+# What a refused YouTube action means to the person who asked for it — the three things they can
+# act on differently: wait for tomorrow's budget, reconnect the account, or try again later.
+YouTubeRefusal = Literal["quota", "reconnect", "unavailable"]
+
+
+def refusal_reason(exc: YouTubeError) -> YouTubeRefusal:
+    """Sort a failure by what the user can do about it. The token step failing (Google refused the
+    refresh, or there is no usable token at all — raised before any endpoint answered, so with no
+    path and no transport reason) means the account must be reconnected; retrying cannot help."""
+    if is_quota_refusal(exc):
+        return "quota"
+    if exc.path == "oauth2/token" or (not exc.path and exc.reason != "transport"):
+        return "reconnect"
+    return "unavailable"
+
+
 def _chunks(items: list, size: int) -> Iterator[list]:
     for i in range(0, len(items), size):
         yield items[i : i + size]
@@ -181,7 +198,10 @@ class YouTubeClient:
             },
         )
         if resp.status_code != 200:
-            raise _upstream_failure("POST", "oauth2/token", resp)
+            exc = _upstream_failure("POST", "oauth2/token", resp)
+            if exc.reason == "invalid_grant":
+                self._drop_dead_grant(tok)
+            raise exc
         data = resp.json()
         access = data["access_token"]
         tok.access_token = encrypt(access)
@@ -191,6 +211,25 @@ class YouTubeClient:
         log.info("Refreshed access token for user %s", self.user.id)
         return access
 
+    def _drop_dead_grant(self, tok) -> None:
+        """Google answered the refresh with `invalid_grant`: the grant was revoked or expired, and no
+        retry will revive it. Forget it, so the account reads as NOT connected — Settings and the
+        onboarding wizard then offer the connect button again (a fresh consent issues a new refresh
+        token). Kept as "granted", the UI showed a live connection with no way to renew it while
+        every call failed. Committed like the refresh above: the caller rolls back on the error."""
+        tok.scopes = None
+        tok.access_token = None
+        tok.refresh_token_enc = None
+        tok.expiry = None
+        self.db.add(tok)
+        self.db.commit()
+        # INFO: the refusal itself is already the warning (`youtube.api.error`, invalid_grant).
+        log.info(
+            "cleared the dead YouTube grant of user %s",
+            self.user.id,
+            extra=logs.event("youtube.grant.cleared"),
+        )
+
     # --- core request ---
     def _get(
         self,

backend/tests/test_log_pii.py

@@ -140,9 +140,9 @@ def test_a_refused_token_refresh_names_the_oauth_reason_and_not_its_prose(sink,
         request=httpx.Request("POST", "https://oauth2.googleapis.com/token"),
     )
     client = yt.YouTubeClient.__new__(yt.YouTubeClient)  # no HTTP client: `_send` is the stub
-    client.db = None
+    client.db = SimpleNamespace(add=lambda obj: None, commit=lambda: None)
     client.user = SimpleNamespace(
-        token=SimpleNamespace(access_token=None, expiry=None, refresh_token_enc=b"x")
+        id=1, token=SimpleNamespace(access_token=None, expiry=None, refresh_token_enc=b"x")
     )
     monkeypatch.setattr(yt, "decrypt_optional", lambda value: None)
     monkeypatch.setattr(yt, "decrypt", lambda value: "a-refresh-token")

backend/tests/test_youtube_refusals.py

@@ -0,0 +1,106 @@
+"""An action YouTube refuses answers a 422 the UI can translate — never a raw 500 — and says what the
+user can do about it (`routes/_common.youtube_refusal`). E9 F1: the two manual syncs had no handler
+at all, so a quota or transport failure opened the blocking "Server error" dialog."""
+
+from types import SimpleNamespace
+
+import httpx
+import pytest
+
+from app.auth import has_read_scope
+from app.models import OAuthToken
+from app.youtube import client as yt
+from app.youtube.client import YouTubeError, refusal_reason
+
+
+@pytest.mark.parametrize(
+    ("exc", "reason"),
+    [
+        (YouTubeError("m", reason="quotaExceeded", path="playlists"), "quota"),
+        (YouTubeError("m", reason="backendError,dailyLimitExceeded", path="videos"), "quota"),
+        (YouTubeError("m", reason="invalid_grant", path="oauth2/token"), "reconnect"),
+        (YouTubeError("No refresh token; user must re-authenticate"), "reconnect"),
+        (YouTubeError("m", reason="transport"), "unavailable"),
+        (YouTubeError("m", reason="backendError", path="subscriptions"), "unavailable"),
+    ],
+)
+def test_a_failure_is_sorted_by_what_the_user_can_do(exc, reason):
+    assert refusal_reason(exc) == reason
+
+
+@pytest.mark.parametrize(
+    ("route", "target"),
+    [
+        ("/api/sync/subscriptions", "app.routes.sync.import_subscriptions"),
+        ("/api/playlists/sync-youtube", "app.routes.playlists.sync_user_playlists"),
+    ],
+)
+def test_a_manual_sync_youtube_refuses_is_a_422_not_a_500(
+    db, as_user, make_user, monkeypatch, route, target
+):
+    user = make_user()
+    db.commit()
+    module, name = target.rsplit(".", 1)
+
+    def refused(*a, **k):
+        raise YouTubeError("GET subscriptions -> 403: quotaExceeded", reason="quotaExceeded")
+
+    monkeypatch.setattr(f"{module}.has_read_scope", lambda u: True)
+    monkeypatch.setattr(f"{module}.{name}", refused)
+
+    r = as_user(user).post(route)
+    assert r.status_code == 422
+    assert r.json()["detail"] == {"code": "youtube", "reason": "quota"}
+
+
+def test_a_revoked_grant_is_forgotten_so_the_account_can_reconnect(db, make_user, monkeypatch):
+    """Google's `invalid_grant` is final. Kept, the grant read as live in Settings — with no connect
+    button — while every call failed; cleared, the connect button comes back."""
+    user = make_user()
+    db.add(
+        OAuthToken(
+            user_id=user.id,
+            refresh_token_enc="x",
+            scopes="openid https://www.googleapis.com/auth/youtube.readonly",
+        )
+    )
+    db.commit()
+    db.refresh(user)
+    assert has_read_scope(user)
+
+    resp = httpx.Response(
+        400,
+        json={"error": "invalid_grant", "error_description": "Token has been expired or revoked."},
+        request=httpx.Request("POST", yt.GOOGLE_TOKEN_URL),
+    )
+    c = yt.YouTubeClient.__new__(yt.YouTubeClient)  # no HTTP client: `_send` is the stub
+    c.db, c.user = db, user
+    monkeypatch.setattr(yt, "decrypt", lambda value: "a-refresh-token")
+    monkeypatch.setattr(yt.sysconfig, "get_str", lambda d, key: "")
+    monkeypatch.setattr(c, "_send", lambda *a, **k: resp)
+
+    with pytest.raises(YouTubeError) as caught:
+        c._access_token()
+    assert refusal_reason(caught.value) == "reconnect"
+
+    db.expire_all()
+    assert not has_read_scope(db.get(type(user), user.id))
+
+
+def test_any_other_token_refusal_keeps_the_grant(monkeypatch):
+    """Only `invalid_grant` is final: a 5xx from the token endpoint is Google having a bad minute."""
+    resp = httpx.Response(
+        503, json={"error": "backend_error"}, request=httpx.Request("POST", yt.GOOGLE_TOKEN_URL)
+    )
+    tok = SimpleNamespace(access_token=None, expiry=None, refresh_token_enc="x", scopes="s")
+    c = yt.YouTubeClient.__new__(yt.YouTubeClient)
+    c.db = SimpleNamespace(add=lambda o: None, commit=lambda: None)
+    c.user = SimpleNamespace(id=1, token=tok)
+    monkeypatch.setattr(yt, "decrypt_optional", lambda value: None)
+    monkeypatch.setattr(yt, "decrypt", lambda value: "a-refresh-token")
+    monkeypatch.setattr(yt.sysconfig, "get_str", lambda d, key: "")
+    monkeypatch.setattr(c, "_send", lambda *a, **k: resp)
+
+    with pytest.raises(YouTubeError):
+        c._access_token()
+    assert tok.scopes == "s"

frontend/src/components/usePlaylistActions.dom.test.tsx

@@ -49,7 +49,7 @@ const linked = { id: 4, name: "Mix", kind: "user", yt_playlist_id: "PL1" } as co
 describe("usePlaylistActions — deleting a list", () => {
   it("does not toast a failure the request layer already put on screen", async () => {
     vi.spyOn(globalThis, "fetch").mockResolvedValue(
-      new Response(JSON.stringify({ detail: { code: "playlist", reason: "youtube_failed" } }), {
+      new Response(JSON.stringify({ detail: { code: "youtube", reason: "unavailable" } }), {
         status: 422,
         headers: { "content-type": "application/json" },
       }),

frontend/src/i18n/locales/en/errors.json

@@ -91,5 +91,10 @@
     "reload": "Reload",
     "notifTitle": "Something broke",
     "notifMessage": "Unexpected error"
+  },
+  "youtube": {
+    "quota": "Today's YouTube budget for this instance is spent. It resets at midnight Pacific time — try again then.",
+    "reconnect": "Google no longer accepts this account's YouTube connection. Sign out and sign in with Google again to reconnect it.",
+    "unavailable": "YouTube didn't accept that just now. Please try again."
   }
 }

frontend/src/i18n/locales/en/playlists.json

@@ -81,7 +81,6 @@
     "name_required": "Give the playlist a name.",
     "youtube_read_scope": "Connect YouTube (read access) to sync your playlists.",
     "not_on_youtube": "This playlist isn't on YouTube.",
-    "youtube_failed": "YouTube didn't accept that just now. Please try again.",
     "watch_later_not_pushable": "The Watch later list can't be sent to YouTube.",
     "watch_later_undeletable": "The Watch later list can't be deleted.",
     "youtube_editing_off": "Enable YouTube editing in Settings first.",

frontend/src/i18n/locales/hu/errors.json

@@ -91,5 +91,10 @@
     "reload": "Újratöltés",
     "notifTitle": "Valami elromlott",
     "notifMessage": "Váratlan hiba"
+  },
+  "youtube": {
+    "quota": "Ennek a példánynak elfogyott a mai YouTube-kerete. Csendes-óceáni idő szerint éjfélkor újraindul — akkor próbáld újra.",
+    "reconnect": "A Google már nem fogadja el ennek a fióknak a YouTube-kapcsolatát. Jelentkezz ki, majd lépj be újra Google-lel az összekötéshez.",
+    "unavailable": "A YouTube most nem fogadta el. Próbáld újra."
   }
 }

frontend/src/i18n/locales/hu/playlists.json

@@ -81,7 +81,6 @@
     "name_required": "Adj nevet a lejátszási listának.",
     "youtube_read_scope": "A listák szinkronizálásához kapcsold össze a YouTube-ot (olvasási hozzáférés).",
     "not_on_youtube": "Ez a lejátszási lista nincs fent a YouTube-on.",
-    "youtube_failed": "A YouTube most nem fogadta el. Próbáld újra.",
     "watch_later_not_pushable": "A „Megnézem később” listát nem lehet a YouTube-ra küldeni.",
     "watch_later_undeletable": "A „Megnézem később” lista nem törölhető.",
     "youtube_editing_off": "Előbb engedélyezd a YouTube-szerkesztést a Beállításokban.",

frontend/src/lib/api/core.test.ts

@@ -167,6 +167,23 @@ describe("req — a structured refusal reads in the user's language", () => {
       detail: localized,
     });
   });
+
+  it.each(["quota", "reconnect", "unavailable"])(
+    "says what to do about an action YouTube refused (%s)",
+    async (reason) => {
+      // Waiting for tomorrow's budget, reconnecting and retrying are different advice; the manual
+      // syncs used to answer a raw 500 here, and the other routes the upstream's English.
+      vi.spyOn(globalThis, "fetch").mockResolvedValue(
+        new Response(JSON.stringify({ detail: { code: "youtube", reason } }), {
+          status: 422,
+          headers: { "content-type": "application/json" },
+        }),
+      );
+      await expect(req("/api/sync/subscriptions", { method: "POST" })).rejects.toMatchObject({
+        detail: `errors.youtube.${reason}`,
+      });
+    },
+  );
 });
 
 describe("req — what it has already put in front of the user", () => {

frontend/src/lib/api/core.ts

@@ -129,6 +129,10 @@ function localizeDetail(d: unknown): string {
     return o.reason === "name_taken"
       ? t("plex.collection.nameTaken")
       : t("plex.collection.editFailed");
+  // An action YouTube refused (routes/_common.youtube_refusal): what the reader can do about it —
+  // wait for the budget, reconnect, or retry. An unknown reason reads as the retryable one.
+  if (o?.code === "youtube")
+    return t(`errors.youtube.${o.reason}`, t("errors.youtube.unavailable"));
   // A playlist action the server refused (Watch later can't be deleted, YouTube said no, …).
   if (o?.code === "playlist") return t(`playlists.errors.${o.reason}`, t("errors.generic"));
   // An admin action on an account or an invite that the server refused: activating an address that