diff --git a/backend/crates/gateway-store/src/postgres/account_groups.rs b/backend/crates/gateway-store/src/postgres/account_groups.rs
index e822fabe0..da8ed6b17 100644
--- a/backend/crates/gateway-store/src/postgres/account_groups.rs
+++ b/backend/crates/gateway-store/src/postgres/account_groups.rs
@@ -529,6 +529,8 @@ async fn group_costs(
         return Ok(BTreeMap::new());
     }
     let completed_usage = completed_usage_fact_predicate("mr");
+    // 用量按实际完成请求的账号统计：账号属于多个分组时计入每个所属分组，
+    // 不再按 Client Key 绑定分组快照归属，避免多分组 Key 的费用重复出现在未承接请求的分组上。
     let statement = format!(
         "with requested_groups(group_id) as (
            select unnest($1::text[])
@@ -541,8 +543,10 @@ async fn group_costs(
                 coalesce(sum(mr.cost_amount), 0)::text as retained_total_usd
          from requested_groups
          cross join runtime_settings settings
+         left join account_group_accounts membership
+           on membership.account_group_id = requested_groups.group_id
          left join model_requests mr
-           on mr.routing_group_refs @> array[requested_groups.group_id]::text[]
+           on mr.provider_account_ref = membership.provider_account_id
           and mr.started_at >= now() - make_interval(days => settings.usage_retention_days::int)
           and {completed_usage}
           and mr.cost_currency = 'USD'
diff --git a/backend/crates/gateway-store/tests/postgres/account_groups.rs b/backend/crates/gateway-store/tests/postgres/account_groups.rs
index d5daa06f6..34863d481 100644
--- a/backend/crates/gateway-store/tests/postgres/account_groups.rs
+++ b/backend/crates/gateway-store/tests/postgres/account_groups.rs
@@ -89,14 +89,24 @@ async fn groups_aggregate_cross_provider_members_and_key_bindings_without_multip
             .await
             .expect("create scoped client key");
     }
+    // 多分组 Key 的请求费用只计入实际承接账号所属的分组，Key 绑定的其他分组不重复计费。
     seed_group_cost_snapshot(
         &database.pool,
-        "req_historical_empty_group",
+        "req_dual_group_key",
         "acct_group_openai",
-        EMPTY_GROUP,
+        &[MIXED_GROUP, EMPTY_GROUP],
         "1.5",
     )
     .await;
+    // 归属跟随完成请求的账号，而不是 Client Key 绑定的分组快照。
+    seed_group_cost_snapshot(
+        &database.pool,
+        "req_account_attribution",
+        "acct_group_xai",
+        &[EMPTY_GROUP],
+        "2.25",
+    )
+    .await;
 
     let page = groups
         .list_account_groups(AccountGroupListQuery {
@@ -138,14 +148,14 @@ async fn groups_aggregate_cross_provider_members_and_key_bindings_without_multip
     assert_eq!(mixed.account_summary.total, 0);
     assert_eq!(mixed.capacity.used_slots, None);
     assert_eq!(mixed.capacity.total_slots, Some(0));
-    assert_eq!(mixed.usage.today_usd.as_str(), "0");
-    assert_eq!(mixed.usage.retained_total_usd.as_str(), "0");
+    assert_eq!(mixed.usage.today_usd.as_str(), "3.75");
+    assert_eq!(mixed.usage.retained_total_usd.as_str(), "3.75");
     let empty = by_id.get(EMPTY_GROUP).expect("empty group");
     assert_eq!(empty.member_count, 0);
     assert!(empty.provider_counts.is_empty());
     assert_eq!(empty.client_key_count, 1);
-    assert_eq!(empty.usage.today_usd.as_str(), "1.5");
-    assert_eq!(empty.usage.retained_total_usd.as_str(), "1.5");
+    assert_eq!(empty.usage.today_usd.as_str(), "0");
+    assert_eq!(empty.usage.retained_total_usd.as_str(), "0");
 
     let all_key = keys
         .reveal_client_key(&client_key_id("key_all_accounts"))
@@ -272,6 +282,7 @@ async fn group_costs_should_include_statusless_websocket_but_reject_statusless_h
         )
         .await
         .expect("create statusless cost group");
+    assign_accounts(&database.pool, EMPTY_GROUP, &["acct_group_statusless"]).await;
     for (request_id, cost_amount) in [
         ("req_group_http_success", "1.5"),
         ("req_group_statusless_websocket", "2"),
@@ -281,7 +292,7 @@ async fn group_costs_should_include_statusless_websocket_but_reject_statusless_h
             &database.pool,
             request_id,
             "acct_group_statusless",
-            EMPTY_GROUP,
+            &[EMPTY_GROUP],
             cost_amount,
         )
         .await;
@@ -393,9 +404,13 @@ async fn seed_group_cost_snapshot(
     pool: &sqlx::PgPool,
     request_id: &str,
     account_id: &str,
-    historical_group_id: &str,
+    routing_group_ids: &[&str],
     cost_amount: &str,
 ) {
+    let routing_group_refs: Vec<String> = routing_group_ids
+        .iter()
+        .map(|id| (*id).to_owned())
+        .collect();
     sqlx::query(
         "insert into model_requests (
            id, client_api_key_ref, config_revision, protocol, operation, endpoint,
@@ -411,16 +426,16 @@ async fn seed_group_cost_snapshot(
            'sent', now(), 'succeeded', 200, 200, 10,
            'provider_reported', $4::numeric, 'USD', now() - interval '1 minute',
            now() + interval '5 minutes', now(),
-           'groups', array[$3]::text[], jsonb_build_array($3::text)
+           'groups', $3::text[], to_jsonb($3::text[])
          )",
     )
     .bind(request_id)
     .bind(account_id)
-    .bind(historical_group_id)
+    .bind(routing_group_refs)
     .bind(cost_amount)
     .execute(pool)
     .await
-    .expect("seed historical group cost snapshot");
+    .expect("seed group cost snapshot");
 }
 
 async fn current_revision(pool: &sqlx::PgPool) -> u64 {