diff --git a/ariadne/services/testing_triage_diagnosis.py b/ariadne/services/testing_triage_diagnosis.py
index 46f68f8..630c5ab 100644
--- a/ariadne/services/testing_triage_diagnosis.py
+++ b/ariadne/services/testing_triage_diagnosis.py
@@ -13,6 +13,7 @@ from ..settings import settings
 TRIAGE_DIAGNOSIS_EVENT_TYPE = "testing_triage_diagnosis"
 _MAX_MODEL_EVIDENCE_CHARS = 24000
 _MAX_MODEL_OUTPUT_CHARS = 12000
+_ASCII_CODEPOINT_LIMIT = 128
 _DIAGNOSIS_SYSTEM_PROMPT = (
     "You are Ariadne's local testing triage model. Use only the supplied JSON evidence. "
     "Return exactly one diagnosis object that matches the requested schema. Do not copy "
@@ -315,7 +316,7 @@ def _safe_evidence_refs(value: Any, summary: dict[str, Any], unknowns: list[Any]
 
 
 def _english_ascii(text: str) -> bool:
-    return all(ord(char) < 128 for char in text)
+    return all(ord(char) < _ASCII_CODEPOINT_LIMIT for char in text)
 
 
 def _mentions_blocked_job(text: str, blocked_jobs: set[str]) -> bool: