Log account delete and subscription changes in UserAuthEvent

Add account_deleted, subscription_started, and subscription_updated
event types. Soft-delete, Checkout/Backer assign, and Stripe portal
lifecycle webhooks write audit rows visible on the user admin.

llm_be/finance/services/plans.py

@@ -8,10 +8,25 @@ from typing import Any
 from django.db import transaction
 from django.utils import timezone
 
+from chat_backend.models import UserAuthEvent
 from finance.models import BackerEmail, SubscriptionPlan, UserSubscription
 
 logger = logging.getLogger(__name__)
 
+
+def log_subscription_auth_event(
+    user,
+    *,
+    started: bool,
+    detail: str,
+) -> None:
+    event_type = (
+        UserAuthEvent.EventType.SUBSCRIPTION_STARTED
+        if started
+        else UserAuthEvent.EventType.SUBSCRIPTION_UPDATED
+    )
+    UserAuthEvent.log(user, event_type, detail=detail[:512])
+
 # Seed catalog for #36. Standard/Pro/Business stay hidden until explicitly enabled.
 PLAN_SEED: list[dict[str, Any]] = [
     {
@@ -141,14 +156,63 @@ def assign_plan(
     source: str,
     status: str = UserSubscription.Status.ACTIVE,
     stripe_subscription_id: str = "",
+    log_auth_event: bool = True,
 ) -> UserSubscription:
     sub = get_or_create_user_subscription(user)
+    prev_plan_id = sub.plan_id
+    prev_status = sub.status
+    prev_source = sub.source
+    prev_stripe_sub = sub.stripe_subscription_id or ""
+    had_active = (
+        prev_status == UserSubscription.Status.ACTIVE and prev_plan_id is not None
+    )
+
     sub.plan = plan
     sub.source = source
     sub.status = status
     if stripe_subscription_id:
         sub.stripe_subscription_id = stripe_subscription_id
     sub.save()
+
+    if log_auth_event:
+        became_active = (
+            status == UserSubscription.Status.ACTIVE and plan is not None
+        )
+        changed = (
+            prev_plan_id != sub.plan_id
+            or prev_status != sub.status
+            or prev_source != sub.source
+            or (
+                bool(stripe_subscription_id)
+                and prev_stripe_sub != (sub.stripe_subscription_id or "")
+            )
+        )
+        if became_active and not had_active:
+            log_subscription_auth_event(
+                user,
+                started=True,
+                detail=(
+                    f"plan={plan.slug} source={source} status={status}"
+                    + (
+                        f" stripe_subscription_id={stripe_subscription_id}"
+                        if stripe_subscription_id
+                        else ""
+                    )
+                ),
+            )
+        elif changed:
+            log_subscription_auth_event(
+                user,
+                started=False,
+                detail=(
+                    f"plan={plan.slug} source={source} status={status}"
+                    + (
+                        f" stripe_subscription_id={stripe_subscription_id}"
+                        if stripe_subscription_id
+                        else ""
+                    )
+                ),
+            )
     return sub
 
 
@@ -241,12 +305,21 @@ def assign_plan_from_stripe(
 ) -> UserSubscription:
     """Assign a catalog plan from a Stripe Checkout / subscription event."""
     seed_subscription_plans(update_existing=False)
+    existing = (
+        UserSubscription.objects.filter(user=user).select_related("plan").first()
+    )
+    prev_cancel = bool(existing.cancel_at_period_end) if existing else False
+    prev_period_end = existing.current_period_end if existing else None
+    had_active = bool(
+        existing
+        and existing.status == UserSubscription.Status.ACTIVE
+        and existing.plan_id
+    )
+
     slug = (plan_slug or "").strip().lower()
     plan = get_plan(slug) if slug else None
-    if plan is None and keep_existing_plan_if_unknown:
-        existing = UserSubscription.objects.filter(user=user).select_related("plan").first()
-        if existing and existing.plan_id:
-            plan = existing.plan
+    if plan is None and keep_existing_plan_if_unknown and existing and existing.plan_id:
+        plan = existing.plan
     if plan is None:
         if slug:
             logger.warning(
@@ -257,12 +330,15 @@ def assign_plan_from_stripe(
         plan = get_plan(SubscriptionPlan.Slug.FOUNDERS)
     if plan is None:
         raise RuntimeError("Founders plan missing from catalog")
+
+    # Single auth-event log after plan + cancel fields are applied.
     sub = assign_plan(
         user,
         plan=plan,
         source=UserSubscription.Source.STRIPE,
         status=status,
         stripe_subscription_id=stripe_subscription_id or "",
+        log_auth_event=False,
     )
     update_fields: list[str] = []
     if cancel_at_period_end is not None:
@@ -273,6 +349,47 @@ def assign_plan_from_stripe(
         update_fields.append("current_period_end")
     if update_fields:
         sub.save(update_fields=update_fields)
+
+    became_active = (
+        sub.status == UserSubscription.Status.ACTIVE and sub.plan_id is not None
+    )
+    cancel_changed = (
+        cancel_at_period_end is not None
+        and bool(cancel_at_period_end) != prev_cancel
+    )
+    period_changed = (
+        current_period_end is not None and current_period_end != prev_period_end
+    )
+    plan_or_status_changed = (
+        not existing
+        or existing.plan_id != sub.plan_id
+        or existing.status != sub.status
+        or (existing.source != sub.source)
+        or (
+            bool(stripe_subscription_id)
+            and (existing.stripe_subscription_id or "")
+            != (sub.stripe_subscription_id or "")
+        )
+    )
+    if became_active and not had_active:
+        log_subscription_auth_event(
+            user,
+            started=True,
+            detail=(
+                f"plan={sub.plan.slug} source={sub.source} status={sub.status}"
+                f" cancel_at_period_end={sub.cancel_at_period_end}"
+            ),
+        )
+    elif plan_or_status_changed or cancel_changed or period_changed:
+        log_subscription_auth_event(
+            user,
+            started=False,
+            detail=(
+                f"plan={sub.plan.slug if sub.plan_id else 'none'} "
+                f"source={sub.source} status={sub.status} "
+                f"cancel_at_period_end={sub.cancel_at_period_end}"
+            ),
+        )
     return sub
 
 

llm_be/finance/services/webhooks.py

@@ -14,6 +14,7 @@ from finance.models import Invoice, Payment, UserSubscription
 from finance.services.plans import (
     assign_plan_from_stripe,
     get_or_create_user_subscription,
+    log_subscription_auth_event,
     resolve_plan_from_stripe_price,
 )
 
@@ -421,6 +422,7 @@ def handle_customer_subscription_deleted(subscription: dict[str, Any]):
         return None
 
     sub = get_or_create_user_subscription(user)
+    prev_status = sub.status
     sub.status = UserSubscription.Status.CANCELED
     sub.cancel_at_period_end = False
     sub.current_period_end = _ts_to_dt(subscription.get("current_period_end"))
@@ -430,6 +432,16 @@ def handle_customer_subscription_deleted(subscription: dict[str, Any]):
     if sub.source == UserSubscription.Source.NONE:
         sub.source = UserSubscription.Source.STRIPE
     sub.save()
+    if prev_status != UserSubscription.Status.CANCELED:
+        log_subscription_auth_event(
+            user,
+            started=False,
+            detail=(
+                f"plan={sub.plan.slug if sub.plan_id else 'none'} "
+                f"source={sub.source} status={sub.status} "
+                f"stripe_subscription_id={sub.stripe_subscription_id}"
+            ),
+        )
     return sub