- Add BudgetExceededError exception for budget limit violations
- Implement CostTrackingService for managing cost tracking and budget enforcement
- Add comprehensive BDD tests for cost budget tracking and enforcement
- Support three-tier budget hierarchy (plan, session, organization)
- Track token usage and costs per provider
- Enforce budget limits with warning thresholds at 90% utilization
- Record budget exhaustion events for auditability

@@ -0,0 +239,4 @@
+def step_verify_exhaustion_event(context: object) -> None:
+    """Verify exhaustion event was recorded."""
+    assert len(context.cost_metadata.budget_exhaustion_events) > 0
+    event = context.cost_metadata.budget_exhaustion_events[0]

@@ -0,0 +1,257 @@
+"""Cost tracking and budget enforcement service.
+

@@ -0,0 +16,4 @@
+    BudgetLevel,
+    OrgCostAccumulator,
+    SessionCostBudget,
+    ThreadSafeOrgCostAccumulator,

@@ -0,0 +77,4 @@
+                    reason=(
+                        f"Session budget of ${session_budget.max_cost_usd:.2f} "
+                        f"would be exceeded (current: ${session_budget.total_cost:.2f}, "
+                        f"proposed: ${proposed_cost:.2f})"

@@ -0,0 +85,4 @@
+        # Check org budget
+        if org_accumulator is not None:
+            if org_accumulator.would_exceed(proposed_cost):
+                utilization = org_accumulator.utilization()

@@ -0,0 +20,4 @@
+    And another LLM call costs $2.50
+    Then the second call should raise BudgetExceededError
+    And the error should indicate plan budget exceeded
+

@@ -0,0 +185,4 @@
+
+@when("a check for ${cost} cost is performed")
+def step_check_budget(context: object, cost: str) -> None:
+    """Check if cost fits in budget."""

@@ -0,0 +329,4 @@
+    except ValueError as e:
+        context.error_raised = True
+        context.error = e
+

@@ -357,1 +357,4 @@
 ]
+
+
+class BudgetExceededError(DomainError):

@@ -0,0 +19,4 @@
+    When an LLM call costs $3.00
+    And another LLM call costs $2.50
+    Then the second call should raise BudgetExceededError
+    And the error should indicate plan budget exceeded

@@ -0,0 +185,4 @@
+
+@when("a check for ${cost} cost is performed")
+def step_check_budget(context: object, cost: str) -> None:
+    """Check if cost fits in budget."""

@@ -0,0 +329,4 @@
+    except ValueError as e:
+        context.error_raised = True
+        context.error = e
+

@@ -357,1 +357,4 @@
 ]
+
+
+class BudgetExceededError(DomainError):

@@ -0,0 +188,4 @@
+    """Check if cost fits in budget."""
+    cost_amount = float(cost)
+    context.budget_check = context.cost_service.check_budget(
+        context.session_budget, None, cost_amount

@@ -0,0 +331,4 @@
+        context.error = e
+
+
+

@@ -0,0 +19,4 @@
+    When an LLM call costs $3.00
+    And another LLM call costs $2.50
+    Then the second call should raise BudgetExceededError
+    And the error should indicate plan budget exceeded

@@ -0,0 +188,4 @@
+    """Check if cost fits in budget."""
+    cost_amount = float(cost)
+    context.budget_check = context.cost_service.check_budget(
+        context.session_budget, None, cost_amount

@@ -0,0 +329,4 @@
+    except ValueError as e:
+        context.error_raised = True
+        context.error = e
+

@@ -357,1 +357,4 @@
 ]
+
+
+class BudgetExceededError(DomainError):

@@ -0,0 +68,4 @@
+    And $80.00 has been spent at organization level
+    And a check for $15.00 cost is performed
+    Then the check should fail due to organization budget
+    And the exceeded_level should be "org"

@@ -0,0 +189,4 @@
+    cost_amount = float(cost)
+    context.budget_check = context.cost_service.check_budget(
+        context.session_budget, None, cost_amount
+    )

@@ -0,0 +331,4 @@
+        context.error = e
+
+
+

@@ -355,3 +355,50 @@ __all__ = [
     "ToolTypeMismatchError",