Fix credit model: allowance is a floor, credits add on top (max_budget = allowance + credits, not reduced by cycle overspend)

app/main.py

@@ -584,32 +584,28 @@ def add_credits(email: str, delta: float, reason: str, reference: str | None = N
 def compute_max_budget(allowance: float, credit_balance: float, team_spend: float | None) -> dict:
     """Compute the effective LiteLLM max_budget from the two buckets.
 
-    Model: the member has a monthly ALLOWANCE (resets via LiteLLM's
-    budget_duration) plus a NON-EXPIRING credit balance. Spend draws the
-    allowance first; once spend exceeds the allowance within a cycle, credits
-    cover the overflow.
+    Model: the member has a monthly ALLOWANCE (renews on each membership
+    payment) plus a credit balance that adds spendable headroom ON TOP of the
+    allowance. The total spendable cap is simply `allowance + credit_balance`
+    — credits never shrink the allowance; they extend it.
 
-    `team_spend` is the member's spend so far this cycle (from LiteLLM).
-    Credits already consumed this cycle are excluded from the available pool
-    so the pushed max_budget reflects exactly what's left:
-
-        max_budget = allowance + credits_remaining
+    `team_spend` is the member's spend so far this cycle (from LiteLLM). It is
+    used only to split the spend between allowance vs credits for display, NOT
+    to reduce the cap.
 
     Returns {"max_budget", "allowance_used", "credits_used"} for dashboards.
     """
+    max_budget = allowance + credit_balance
     if team_spend is None:
-        # Unknown spend: be permissive (full allowance + full credits) so we
-        # never wrongly block a member over a metrics gap.
         return {
-            "max_budget": allowance + credit_balance,
+            "max_budget": max_budget,
             "allowance_used": 0.0,
             "credits_used": 0.0,
         }
     allowance_used = min(max(team_spend, 0.0), allowance)
     credits_used = max(0.0, team_spend - allowance)
-    credits_remaining = max(0.0, credit_balance - credits_used)
     return {
-        "max_budget": allowance + credits_remaining,
+        "max_budget": max_budget,
         "allowance_used": allowance_used,
         "credits_used": credits_used,
     }