mvanhorn/last30days-skill · error · ValueError

Polymarket item carries no event id; slug equality alone can

Error message

Polymarket item carries no event id; slug equality alone cannot verify event identity

What it means

Raised during Polymarket datum re-verification when the item's URL matches a slug pattern but the item carries no event id anywhere. Because a slug can be reused by a different event over time, slug equality alone cannot prove the refreshed event is the same one originally cited, so the library fails closed with ValueError instead of returning a possibly-wrong verdict.

Source

Thrown at skills/last30days/scripts/lib/polymarket.py:949

    # On the slug fallback, a slug can be re-used by a re-created event. When
    # the cached item still carries the original Gamma event id (numeric; the
    # synthetic PM<N> parse fallback carries no identity), the response id
    # must match it too, or the verdict would come from another market.
    expected_id = (
        cached_item_id
        if not event_id and re.fullmatch(r"\d+", cached_item_id)
        else ""
    )
    if event_id:
        payload = http.request(
            "GET", f"{GAMMA_EVENTS_URL}/{quote(event_id)}", timeout=10, retries=2,
        )
    elif slug_match:
        if not expected_id:
            # No event id anywhere: slug equality alone cannot verify event
            # identity, so fail closed (unsupported) instead of re-deriving a
            # verdict from whatever event currently owns the slug.
            raise ValueError(
                "Polymarket item carries no event id; slug equality alone "
                "cannot verify event identity"
            )
        requested_slug = slug_match.group(1)
        payload = http.request(
            "GET", GAMMA_EVENTS_URL, params={"slug": requested_slug},
            timeout=10, retries=2,
        )
    else:
        raise ValueError("Polymarket item has no event id or slug")

    requested_slug = slug_match.group(1) if slug_match else None

    def _matches_identity(entry: dict) -> bool:
        if str(entry.get("slug") or "").strip() != requested_slug:
            return False
        if expected_id and str(entry.get("id") or "").strip() != expected_id:
            return False

View on GitHub (pinned to c7460f6114)

Solutions

1. Ensure items persisted for Polymarket carry the Gamma numeric event id (item.metadata/event id) at ingest time
2. If the event id is genuinely unavailable, refresh via the original search flow instead of refetch_datum so identity is re-established
3. Catch ValueError here and mark the datum 'unverified' rather than retrying - retrying cannot fix missing identity data

Example fix

# before
url = f"https://polymarket.com/event/{slug}"  # id never stored

# after
metadata = {"event_id": event["id"], "slug": slug}  # persist id at ingest
url = f"https://polymarket.com/event/{slug}"

def can_verify_polymarket_event(item) -> bool:
    has_id = bool(getattr(item, "id", "") and re.fullmatch(r"\d+", str(item.id)))
    has_slug = bool(re.search(r"polymarket\.com/event/([\w-]+)", getattr(item, "url", "") or ""))
    return has_id or (has_slug and bool(item.metadata.get("event_id")))

try:
    datum = refetch_datum(item, key)
except ValueError as e:
    if "slug equality alone" in str(e):
        mark_unverifiable(item)  # identity data missing; do not retry
    raise

When it happens

Trigger: refetch_datum is called on a Polymarket item whose URL is a slug-style link (e.g. polymarket.com/event/some-slug) but whose cached item id is not purely numeric (so no event id can be derived) and no expected id is available from metadata. The slug_match branch is taken with expected_id falsy, hitting the explicit raise.

Common situations: Items persisted from an older schema that did not store the Gamma event id; hand-constructed items with only a URL; upstream Gamma data where the id field was stripped; migrating stored items between versions of the ingest pipeline.

Related errors

• Polymarket item has no event id or slug
• Nominations bundle {path} contains no readable nominations (
• Polymarket event was not found
• Polymarket event is closed, unavailable, or malformed
• Polymarket datum {datum_key!r} was not found

AI-assisted analysis of mvanhorn/last30days-skill@c7460f6114 (2026-08-15). Data as JSON: /api/errors/105ed8bfb26ac592. Report an issue: GitHub.