feat(advisor): add 0.85 advisory threshold triggering LLM suggestions

- Add advisory_threshold=0.85 field to MetricRule (higher-is-better metrics)
- diagnose() now emits severity='low' for scores in (warning_threshold, 0.85)
- noise_sensitivity (lower-is-better) keeps its existing two-tier thresholds
- writer.py: severity labels mapped to Chinese (严重/警告/待优化)
- llm_analyzer.py: prompt explains low/warning/critical tiers in Chinese
- Tests: 5 new cases for 'low' severity, updated log summary assertions

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

rag_eval/advisor/llm_analyzer.py

@@ -22,22 +22,31 @@ _PROMPT_TEMPLATE = """\
 
 ## 报告要求
 
-1. 按指标分节（## 指标名  [severity]），先解释"为什么低"（结合低分样本具体分析），再给出"具体怎么改"
-2. "具体怎么改"要结合低分样本的实际内容，而不只是泛泛建议
-3. 最后写一节 **## 优先优化次序**，按性价比排序（不增加 LLM 调用次数的优化优先）
-4. 语言简洁，面向工程师，不要废话，不要重复列表内容
+1. 按指标分节（## 指标名  [严重程度]），先解释"为什么低"（结合低分样本具体分析），再给出"具体怎么改"
+2. 严重程度说明：critical=严重（<阈值50%），warning=警告（<阈值70%），low=待优化（低于0.85，有提升空间）
+3. "具体怎么改"要结合低分样本的实际内容，而不只是泛泛建议
+4. 最后写一节 **## 优先优化次序**，按性价比排序（不增加 LLM 调用次数的优化优先），critical 和 warning 项优先于 low 项
+5. 语言简洁，面向工程师，不要废话，不要重复列表内容
 
 只输出 Markdown 报告正文，不要任何前置说明。
 """
 
 
+_SEVERITY_LABEL_ZH: dict[str, str] = {
+    "critical": "严重",
+    "warning": "警告",
+    "low": "待优化",
+}
+
+
 def _build_diagnosis_summary(diagnoses: list[Diagnosis]) -> str:
     lines = []
     for d in diagnoses:
         direction = "（越低越好）" if d.metric == "noise_sensitivity" else ""
+        label = _SEVERITY_LABEL_ZH.get(d.severity, d.severity)
         lines.append(
             f"- **{d.metric}** {direction} 均值={d.mean_score:.4f}，"
-            f"阈值={d.threshold}，严重程度={d.severity}"
+            f"阈值={d.threshold}，严重程度={label}"
         )
         lines.append(f"  - 可能原因：{'; '.join(d.root_causes)}")
         lines.append(f"  - 建议动作：{'; '.join(d.suggested_actions)}")

rag_eval/advisor/rules.py

@@ -14,6 +14,9 @@ class MetricRule:
     higher_is_better: bool  # False for noise_sensitivity
     root_causes: list[str]
     suggested_actions: list[str]
+    # Scores below this threshold trigger a "low" advisory (LLM suggestion requested).
+    # Only applies to higher_is_better metrics; noise_sensitivity uses existing thresholds.
+    advisory_threshold: float = 0.85
 
 
 METRIC_RULES: dict[str, MetricRule] = {
@@ -208,10 +211,14 @@ def diagnose(
             elif mean < rule.warning_threshold:
                 severity = "warning"
                 threshold = rule.warning_threshold
+            elif mean < rule.advisory_threshold:
+                # Score is acceptable but below 0.85 — request LLM optimization advice.
+                severity = "low"
+                threshold = rule.advisory_threshold
             else:
-                continue  # above warning threshold → no diagnosis
+                continue  # >= advisory_threshold → no diagnosis needed
         else:
-            # lower is better (noise_sensitivity)
+            # lower is better (noise_sensitivity): keep existing two-tier logic
             if mean > rule.critical_threshold:
                 severity = "critical"
                 threshold = rule.critical_threshold

rag_eval/advisor/writer.py

@@ -8,12 +8,22 @@ from .rules import Diagnosis
 
 logger = logging.getLogger("rag_eval.advisor")
 
+# Chinese display labels for each severity tier.
+_SEVERITY_LABEL: dict[str, str] = {
+    "critical": "严重",
+    "warning": "警告",
+    "low": "待优化",
+}
+
 
 def _format_log_summary(diagnoses: list[Diagnosis], advice_path: Path) -> str:
     """Return a single-line log summary of triggered diagnoses."""
     if not diagnoses:
         return "[advisor] 所有指标正常，无需优化建议。"
-    parts = [f"{d.metric}({d.mean_score:.2f}, {d.severity})" for d in diagnoses]
+    parts = [
+        f"{d.metric}({d.mean_score:.2f},{_SEVERITY_LABEL.get(d.severity, d.severity)})"
+        for d in diagnoses
+    ]
     triggered = " ".join(parts)
     return f"[advisor] 触发诊断 {len(diagnoses)} 项: {triggered}  →  {advice_path}"
 
@@ -24,7 +34,8 @@ def _build_fallback_report(diagnoses: list[Diagnosis]) -> str:
         return ""
     lines = ["## 规则诊断（LLM 分析不可用）\n"]
     for d in diagnoses:
-        lines.append(f"### {d.metric}  [{d.severity}]  均值={d.mean_score:.4f}")
+        label = _SEVERITY_LABEL.get(d.severity, d.severity)
+        lines.append(f"### {d.metric}  [{label}]  均值={d.mean_score:.4f}")
         lines.append("\n**可能原因：**")
         for cause in d.root_causes:
             lines.append(f"- {cause}")