diff --git a/benchmarks/harbor-buzz-orchestra/src/harbor_buzz_orchestra/accounting.py b/benchmarks/harbor-buzz-orchestra/src/harbor_buzz_orchestra/accounting.py
index b3820da0b7..6cf07b78e9 100644
--- a/benchmarks/harbor-buzz-orchestra/src/harbor_buzz_orchestra/accounting.py
+++ b/benchmarks/harbor-buzz-orchestra/src/harbor_buzz_orchestra/accounting.py
@@ -84,8 +84,12 @@ _ANSI_RE = re.compile(r"\x1b\[[0-9;]*[a-zA-Z]")
 # fields) degrades to "no samples" rather than a wrong number.
 USAGE_MARKER = "goose usage update"
 _SESSION_RE = re.compile(r"\bsession_id=(\S+)")
-_INPUT_RE = re.compile(r"\binput=(\d+)\b")
-_OUTPUT_RE = re.compile(r"\boutput=(\d+)\b")
+# Older buzz-acp builds render cumulative counters as `input=123`; current
+# builds retain their optional type in the tracing field and render
+# `input=Some(123)`. Accept both representations so a source update cannot make
+# a real, billed run look like zero usage.
+_INPUT_RE = re.compile(r"\binput=(?:Some\()?(\d+)(?:\))?")
+_OUTPUT_RE = re.compile(r"\boutput=(?:Some\()?(\d+)(?:\))?")
 # The cache-served subset of `input`, added to the usage line by buzz-acp. Absent
 # in logs written by an agent build that predates it, which is why a missing
 # field must read as "unknown" (fall back to the modelled rate) and never as 0 —
diff --git a/benchmarks/harbor-buzz-orchestra/tests/test_accounting.py b/benchmarks/harbor-buzz-orchestra/tests/test_accounting.py
index 7cde72492b..e126e235d4 100644
--- a/benchmarks/harbor-buzz-orchestra/tests/test_accounting.py
+++ b/benchmarks/harbor-buzz-orchestra/tests/test_accounting.py
@@ -64,6 +64,16 @@ def test_parse_usage_log_reads_the_coloured_lines_a_real_trial_produces():
     )
 
 
+def test_parse_usage_log_reads_optional_counters_from_current_buzz_acp():
+    text = (
+        "2026-08-18T23:25:39Z DEBUG acp::usage: goose usage update "
+        "session_id=ses_current input=Some(5738) output=Some(1802) cached=0"
+    )
+    assert accounting.parse_usage_log(text) == (
+        accounting.SessionUsage("ses_current", 5738, 1802, 0),
+    )
+
+
 def test_parse_handoffs_reads_coloured_lines_too():
     """Same formatter, same escapes — the compaction bound must not silently zero."""
     text = (