feat: complete production-quality Model Router AI traffic control platform

backend/app/budgets/manager.py

@@ -0,0 +1,39 @@
+from typing import Tuple
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+from app.storage.models import BudgetRecord
+
+
+async def check_budget_threshold(
+    session: AsyncSession,
+    cost_to_add: float = 0.0,
+) -> Tuple[float, str]:
+    """
+    Checks current budget utilization percentage and determines intervention mode:
+    - NORMAL (< 80%)
+    - OPTIMIZE_80 (>= 80% and < 95%)
+    - CHEAP_95 (>= 95% and < 100%)
+    - BLOCK_100 (>= 100%)
+    """
+    res = await session.execute(select(BudgetRecord).filter_by(id="default"))
+    budget = res.scalar_one_or_none()
+    if not budget:
+        return 0.0, "NORMAL"
+
+    monthly_limit = budget.monthly_limit or 100.0
+    current_spend = budget.current_monthly_spend + cost_to_add
+    percent = (current_spend / monthly_limit) * 100.0 if monthly_limit > 0 else 0.0
+
+    mode = "NORMAL"
+    if percent >= 100.0:
+        mode = "BLOCK_100"
+    elif percent >= 95.0:
+        mode = "CHEAP_95"
+    elif percent >= 80.0:
+        mode = "OPTIMIZE_80"
+
+    budget.current_monthly_spend = current_spend
+    budget.intervention_mode = mode
+    await session.commit()
+
+    return round(percent, 2), mode