diff --git a/app/main.py b/app/main.py
index ee86e3a..aeb681c 100644
--- a/app/main.py
+++ b/app/main.py
@@ -85,40 +85,40 @@ WEBHOOK_TOKEN = os.environ.get("WEBHOOK_TOKEN", "")
 OC_GRAPHQL_URL = "https://opencollective.com/api/graphql/v2"
 OC_COLLECTIVE_SLUG = os.environ.get("OC_COLLECTIVE_SLUG", "inference-cooperative")
 
-# Cache of TierId -> (face_value_cents, name), fetched from the OC GraphQL
-# API (tiers scope is allowed on our personal token; orders is not).
-_tier_face_cache: dict[int, tuple[int, str]] = {}
+# Cache of order idV2 -> tip-free contribution amount in cents, resolved via
+# OC's PUBLIC GraphQL API (no token needed; our personal token lacks the
+# orders scope but unauthenticated reads of public orders work).
+_order_amount_cache: dict[str, int] = {}
 
 
-async def get_tier_face(tier_id: int | None) -> tuple[int | None, str]:
-    """Look up a tier's face value and name by numeric legacyId.
+async def get_order_amount(order_id_v2: str | None) -> int | None:
+    """Look up an order's contribution amount (EXCLUDING the platform tip).
 
-    Returns (face_cents, name); (None, "") if unknown. The webhook payload
-    carries only TierId — no name, no face amount — so we resolve via the
-    collective's tiers query and cache the mapping.
+    The webhook's `totalAmount` includes the buyer's optional OC tip, which
+    the co-op never receives — credits must be granted on the tip-free
+    amount. Returns cents, or None if unresolvable.
     """
-    if not tier_id:
-        return None, ""
-    if tier_id in _tier_face_cache:
-        return _tier_face_cache[tier_id]
+    if not order_id_v2:
+        return None
+    if order_id_v2 in _order_amount_cache:
+        return _order_amount_cache[order_id_v2]
     try:
-        query = ('{ collective(slug: "%s") { tiers { nodes { legacyId name '
-                 "amount { valueInCents } } } } }" % OC_COLLECTIVE_SLUG)
+        query = ('{ order(order: {id: "%s"}) { amount { valueInCents } '
+                 'platformTipAmount { valueInCents } } }' % order_id_v2)
         async with httpx.AsyncClient(timeout=15.0) as client:
             r = await client.post(OC_GRAPHQL_URL,
-                headers={"Personal-Token": OC_PERSONAL_TOKEN,
+                headers={"Content-Type": "application/json",
                          "User-Agent": "Mozilla/5.0 (X11; Linux x86_64)"},
                 json={"query": query})
-        for t in r.json().get("data", {}).get("collective", {}).get("tiers", {}).get("nodes", []):
-            lid = t.get("legacyId")
-            if lid is not None:
-                _tier_face_cache[int(lid)] = (
-                    (t.get("amount") or {}).get("valueInCents") or 0,
-                    t.get("name") or "",
-                )
+        o = r.json().get("data", {}).get("order") or {}
+        cents = (o.get("amount") or {}).get("valueInCents")
+        if cents is not None:
+            _order_amount_cache[order_id_v2] = int(cents)
+            return int(cents)
     except Exception as e:
-        logger.warning("Tier face lookup failed for %s: %s", tier_id, e)
-    return _tier_face_cache.get(tier_id, (None, ""))
+        logger.warning("Order amount lookup failed for %s: %s", order_id_v2, e)
+    return None
+
 
 
 # Personal token for the "Inference Co-op Bot" account, which is an admin of
@@ -1334,16 +1334,12 @@ async def opencollective_webhook(request: Request, token: str):
         # OC but is NOT a membership — don't provision it.
         #
         # Tier detection: the webhook payload carries only `data.order.TierId`
-        # (numeric) — NO tier name or face amount. Resolve both via the
-        # collective's tiers query (cached); the order description is the
-        # fallback for the name ("... (Credit pack)").
+        # (numeric) — NO tier name. The order description embeds it
+        # ("Financial contribution to Inference Cooperative (Credit pack)").
         order = data.get("order") or {}
-        tier_id = order.get("TierId")
-        face_cents, tier_name = await get_tier_face(tier_id)
-        if not tier_name:
-            order_desc = order.get("description") or ""
-            m = re.search(r"\(([^)]+)\)\s*$", order_desc.strip())
-            tier_name = m.group(1).strip() if m else ""
+        order_desc = order.get("description") or ""
+        m = re.search(r"\(([^)]+)\)\s*$", order_desc.strip())
+        tier_name = m.group(1).strip() if m else ""
         amount_cents = data.get("amount") or 0
         if not amount_cents:
             amount_cents = order.get("totalAmount") or 0
@@ -1356,18 +1352,20 @@ async def opencollective_webhook(request: Request, token: str):
         if "credit" in tier_name.lower() and slug and event_type == "order.processed":
             members = await fetch_members()
             email = next((m["email"] for m in members if m["slug"] == slug), None)
-            # Credits are granted at the tier's FACE VALUE (what the pack
-            # buys), not the total charged — the total can include a platform
-            # tip the co-op never receives. Fall back to the charged amount
-            # if the face value is unavailable.
-            if face_cents:
-                amount = round(face_cents / 100.0, 2)
+            # The tier is VARIABLE-amount — no fixed face value. Credits are
+            # granted on the contribution amount EXCLUDING the OC platform
+            # tip (totalAmount - tip = amount), which we resolve via OC's
+            # public order API. Fallback: webhook totalAmount (slightly
+            # overgrants if a tip was included; logged).
+            tip_free_cents = await get_order_amount(order.get("idV2"))
+            if tip_free_cents is not None:
+                amount = round(tip_free_cents / 100.0, 2)
             else:
                 amount = round(float(amount_cents) / 100.0, 2)
             charged = round(float(amount_cents) / 100.0, 2)
             if charged > amount:
                 logger.info(
-                    "Credit pack: charged $%.2f but face value $%.2f (tip/fees); granting face value",
+                    "Credit pack: charged $%.2f including tip; granting tip-free $%.2f",
                     charged, amount,
                 )
             oc_ref = f"oc:{slug}:{data.get('id', '')}"