From ef0fac4933287ca2580000a4addfde694c606701 Mon Sep 17 00:00:00 2001
From: Miguel Palhas <mpalhas@gmail.com>
Date: Tue, 25 Aug 2026 01:00:41 +0100
Subject: [PATCH] feat(arr): let backends report billed characters

---
 crates/arr-subs/src/translate.rs | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/crates/arr-subs/src/translate.rs b/crates/arr-subs/src/translate.rs
index 2fa8345..4114a90 100644
--- a/crates/arr-subs/src/translate.rs
+++ b/crates/arr-subs/src/translate.rs
@@ -128,6 +128,15 @@ pub trait Backend: fmt::Debug + Send + Sync {
         BATCH_CHAR_BUDGET
     }
 
+    /// Characters this backend has billed so far, cumulative over its life.
+    ///
+    /// Translators charge per character (DESIGN.md §15); the daily budget
+    /// (#197) spends against what was actually billed rather than an
+    /// estimate of it. A backend that cannot say reports zero.
+    fn characters_billed(&self) -> u64 {
+        0
+    }
+
     /// Translate one batch.
     ///
     /// The reply is expected to carry every cue number the batch carried,