fix(models): type SubscriptionEvent from the event the API sends (#149)

CHANGELOG.md

@@ -71,6 +71,19 @@ All notable changes to the OilPriceAPI Python SDK will be documented in this fil
 
 ### Fixed
 
+- **`SubscriptionEvent` is typed from the event the API sends (#149).** It
+  declared `type`, `code`, `payload` and `created_at`, which
+  `GET /v1/subscriptions/events` has never sent, so they read `None` on every
+  real event. Meanwhile `id`, `observed_at`, `snapshot`, `deltas`, `source` and
+  `tool_name` were untyped extras. The model now declares:
+  - required `id`, `seq`, `watch_id`, `observed_at` (a timezone-aware
+    `datetime`), `snapshot` and `deltas`;
+  - optional `source` and `tool_name`.
+  `snapshot` maps each code to the new `SubscriptionEventSnapshot` (`price`,
+  `currency`, optional `change_24h_pct` and `as_of`). `deltas` maps each code
+  to the new `SubscriptionEventDelta` (`price_change`, optional `pct_change`).
+  An event missing a required field raises
+  `OilPriceAPIError(code="MALFORMED_RESPONSE")`.
 - **`error.code` is no longer set to a human sentence (#145).** For fail
   envelopes, `{"status": "fail", "data": {"error": ...}}`, the SDK copied
   `data.error` into `error.code` / `error.machine_code` whatever it held. Every
@@ -119,6 +132,23 @@ All notable changes to the OilPriceAPI Python SDK will be documented in this fil
   default to `[]`, reading as a watch on nothing; the API always sends it, so a
   missing value now fails validation instead of being invented.
 
+### Deprecated
+
+- **`SubscriptionEvent.type`, `.code`, `.payload` and `.created_at` are
+  deprecated and will be removed in 2.0.0 (#149).** The events API never sends
+  any of them. They are no longer pydantic fields and do not appear in
+  `model_dump()`. Each is now a property that emits a `DeprecationWarning` on
+  access:
+  - `type` returns `None` and has no equivalent, because every event is an
+    interval snapshot.
+  - `code` returns `None`. An event covers every watched code; use
+    `list(event.snapshot)`.
+  - `payload` returns `None`. Use `event.snapshot` and `event.deltas`.
+  - `created_at` returns `observed_at`, the event's timestamp, where it used to
+    return `None`.
+
+  Parsing, polling and serializing events emit no warning.
+
 ## [1.15.0] - 2026-09-13
 
 ### Fixed

oilpriceapi/__init__.py

@@ -45,6 +45,8 @@
     PriceAlert,
     Subscription,
     SubscriptionEvent,
+    SubscriptionEventDelta,
+    SubscriptionEventSnapshot,
     WebhookTestResponse,
 )
 from oilpriceapi.resources.subscriptions import SubscriptionEventsPage
@@ -90,6 +92,8 @@
     "ParcelFuelSurchargeCarrier",
     "Subscription",
     "SubscriptionEvent",
+    "SubscriptionEventDelta",
+    "SubscriptionEventSnapshot",
     "SubscriptionEventsPage",
     "PriceStream",
     "StreamUpdate",

oilpriceapi/_subscriptions_common.py

@@ -386,7 +386,7 @@ def unwrap_events_page(
                 f"{_field_errors(error)}",
                 response,
             ) from error
-        if event.seq is not None and event.seq > cursor:
+        if event.seq > cursor:
             raise _malformed(
                 subject,
                 f"data.cursor {cursor} is behind data.events[{index}].seq {event.seq}; "

oilpriceapi/models.py

@@ -4,6 +4,7 @@
 Pydantic models for API responses.
 """
 
+import warnings
 from datetime import date, datetime
 from typing import Any, Dict, List, Optional, Union
 
@@ -454,32 +455,122 @@ def parse_datetimes(cls, v):
         return v
 
 
+class SubscriptionEventSnapshot(BaseModel):
+    """One watched code's price at the moment a subscription event was recorded.
+
+    Built by the API's ``MarketBriefBuilder#snapshot_hash``.
+    """
+
+    model_config = ConfigDict(populate_by_name=True, extra="allow")
+
+    price: float = Field(description="Latest spot price")
+    currency: str = Field(description="Price currency, e.g. USD")
+    change_24h_pct: Optional[float] = Field(
+        default=None, description="24h change in percent; None when there is no 24h comparison"
+    )
+    as_of: Optional[datetime] = Field(default=None, description="Timestamp of the price used")
+
+
+class SubscriptionEventDelta(BaseModel):
+    """One code's change since the previous event of the same subscription.
+
+    Built by the API's ``Watch#compute_deltas``.
+    """
+
+    model_config = ConfigDict(populate_by_name=True, extra="allow")
+
+    price_change: float = Field(description="Price change since the previous event")
+    pct_change: Optional[float] = Field(
+        default=None,
+        description="Percent change; None when the previous price was 0 (the API omits it)",
+    )
+
+
 class SubscriptionEvent(BaseModel):
-    """A single event emitted by a subscription, returned from the poll endpoint."""
+    """A single event emitted by a subscription, returned from the poll endpoint.
+
+    Typed from ``GET /v1/subscriptions/events`` as the API sends it (#149).
+    ``snapshot`` and ``deltas`` are keyed by commodity code. ``deltas`` is
+    ``{}`` on a subscription's first event, and a code is absent from it when
+    either snapshot lacked a price.
+    """
 
     model_config = ConfigDict(populate_by_name=True, extra="allow")
 
-    seq: Optional[int] = Field(default=None, description="Monotonic per-user sequence cursor")
-    watch_id: Optional[str] = Field(default=None, description="Subscription (watch) that produced the event")
-    type: Optional[str] = Field(default=None, description="Event type")
-    code: Optional[str] = Field(default=None, description="Commodity code the event relates to")
-    payload: Optional[Dict[str, Any]] = Field(default=None, description="Event payload")
-    created_at: Optional[datetime] = Field(default=None, description="Event timestamp")
+    id: str = Field(description="Event identifier")
+    seq: int = Field(description="Monotonic per-user sequence cursor")
+    watch_id: str = Field(description="Subscription (watch) that produced the event")
+    observed_at: datetime = Field(description="When the snapshot was taken")
+    snapshot: Dict[str, SubscriptionEventSnapshot] = Field(
+        description="Price per watched code at observed_at"
+    )
+    deltas: Dict[str, SubscriptionEventDelta] = Field(
+        description="Change per code since the previous event; {} on the first event"
+    )
+    source: Optional[str] = Field(default=None, description="Attribution source of the subscription")
+    tool_name: Optional[str] = Field(default=None, description="Attribution tool name of the subscription")
 
-    @field_validator("created_at", mode="before")
-    @classmethod
-    def parse_created_at(cls, v):
-        """Parse created_at from various formats."""
-        if v is None:
-            return None
-        if isinstance(v, str):
-            try:
-                return datetime.fromisoformat(v.replace("Z", "+00:00"))
-            except ValueError:
-                from dateutil import parser
+    # Deprecated accessors (#149). Plain properties, not pydantic fields, so they
+    # never appear in model_dump() or serialization. Removed in 2.0.0.
 
-                return parser.parse(v)
-        return v
+    @property
+    def created_at(self) -> datetime:
+        """Deprecated alias for ``observed_at``; removed in 2.0.0.
+
+        The API never sent ``created_at`` on an event, so this always read
+        ``None``. The event's timestamp is ``observed_at``.
+        """
+        warnings.warn(
+            "SubscriptionEvent.created_at is deprecated and will be removed in 2.0.0; "
+            "use observed_at. The events API does not send created_at (#149).",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return self.observed_at
+
+    @property
+    def type(self) -> None:
+        """Deprecated; always ``None``, removed in 2.0.0.
+
+        The events API has no event type: every event is an interval snapshot.
+        """
+        warnings.warn(
+            "SubscriptionEvent.type is deprecated and will be removed in 2.0.0. It was "
+            "always None: the events API sends no event type, and has no equivalent "
+            "field; every event is an interval snapshot (#149).",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return None
+
+    @property
+    def code(self) -> None:
+        """Deprecated; always ``None``, removed in 2.0.0.
+
+        An event can cover several codes: use ``snapshot.keys()``.
+        """
+        warnings.warn(
+            "SubscriptionEvent.code is deprecated and will be removed in 2.0.0. It was "
+            "always None: an event covers every watched code, so use "
+            "list(event.snapshot) (#149).",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return None
+
+    @property
+    def payload(self) -> None:
+        """Deprecated; always ``None``, removed in 2.0.0.
+
+        The event data is in ``snapshot`` and ``deltas``.
+        """
+        warnings.warn(
+            "SubscriptionEvent.payload is deprecated and will be removed in 2.0.0. It "
+            "was always None: use event.snapshot and event.deltas (#149).",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return None
 
 
 class DataConnectorPrice(BaseModel):

tests/unit/test_async_subscriptions_resource.py

@@ -73,7 +73,18 @@ async def test_events(self, client):
             "data": {
                 "cursor": 7,
                 "has_more": False,
-                "events": [{"seq": 7, "watch_id": "abc-123", "type": "threshold", "code": "WTI_USD"}],
+                "events": [
+                    {
+                        "id": "a835a930-f34f-4001-80b1-38fb3cde3797",
+                        "seq": 7,
+                        "watch_id": "abc-123",
+                        "observed_at": "2026-09-08T17:21:19Z",
+                        "snapshot": {"WTI_USD": {"as_of": "2026-09-08T17:20:37Z", "price": 63.02, "currency": "USD", "change_24h_pct": -0.08}},
+                        "deltas": {"WTI_USD": {"pct_change": -0.26, "price_change": -0.16}},
+                        "source": "api",
+                        "tool_name": None,
+                    }
+                ],
             }
         }
         mock = AsyncMock(return_value=payload)