fix(intercept): 加固裁判输出解析,避免正确 DENY 被当成放行

模型若照抄提示词里的中文标签(如「拦截:DENY:...」),旧解析要求关键词在行首,
会判为无法解析 → 按 fail_action(默认 allow)兜底,导致真实拦截被放行。

- ParseVerdict 改为扫描行内最早出现的 ALLOW/ASK/DENY 关键词,容忍前缀标签
- 提示词输出段改用箭头并明确禁止输出中文标签,附合法输出示例
- 新增 prompt_test.go 覆盖标签回显、全角冒号、大小写、超长理由截断等场景

Claude-Session: https://claude.ai/code/session_019QXSCDmzimwnjntBNCgUD7

intercept/prompt.go

@@ -81,10 +81,12 @@ DENY   hping3 --flood -p 80 tgt                                参数明示 floo
 ASK    mysql -e "DROP TABLE users_bak_0921"                    像备份表,无法确定是否生产数据。
 ASK    删除 /data/uploads 下一个归属不明的文件                    作用对象无法判明。
 
-# 输出(严格一行,不要任何解释、前后缀或代码块)
-- 放行:ALLOW
-- 转人工:ASK:<不超过30字,说明为何判不准>
-- 拦截:DENY:<不超过30字,写明命中 D1–D6 中哪条>`
+# 输出格式(严格一行,只含裁决本身;禁止输出「放行/转人工/拦截」等中文标签、解释、前后缀或代码块)
+- 放行  → 输出 ALLOW
+- 转人工 → 输出 ASK:<不超过30字,说明为何判不准>
+- 拦截  → 输出 DENY:<不超过30字,写明命中 D1–D6 中哪条>
+合法输出示例:DENY:删除生产文件命中D4
+合法输出示例:ALLOW`
 
 // Verdict is the parsed outcome of the judge's single-line reply.
 type Verdict struct {
@@ -92,42 +94,57 @@ type Verdict struct {
 	Reason string
 }
 
-// ParseVerdict parses the judge model's reply. It accepts a single line of the
-// form ALLOW / ASK:<reason> / DENY:<reason> (case-insensitive, optional colon).
-// Only the first non-empty line is considered. An empty Action signals the reply
-// could not be parsed, so the caller applies the configured fail action.
+// ParseVerdict parses the judge model's reply. It accepts a single line
+// containing ALLOW / ASK:<reason> / DENY:<reason> (case-insensitive). It scans
+// for the earliest verdict keyword rather than requiring it at the very start,
+// so a model that echoes a leading label from the prompt (e.g. "拦截:DENY:...")
+// is still parsed correctly instead of silently falling through to fail-open.
+// An empty Action signals the reply could not be parsed, so the caller applies
+// the configured fail action.
 func ParseVerdict(text string) Verdict {
 	line := firstNonEmptyLine(text)
 	if line == "" {
 		return Verdict{}
 	}
 	upper := strings.ToUpper(line)
-	switch {
-	case strings.HasPrefix(upper, "ALLOW"):
-		return Verdict{Action: "allow"}
-	case strings.HasPrefix(upper, "DENY"):
-		return Verdict{Action: "deny", Reason: verdictReason(line, 4)}
-	case strings.HasPrefix(upper, "ASK"):
-		return Verdict{Action: "ask", Reason: verdictReason(line, 3)}
-	default:
+
+	// Find whichever verdict keyword appears earliest in the line.
+	keywords := []struct {
+		word   string
+		action string
+	}{
+		{"ALLOW", "allow"},
+		{"DENY", "deny"},
+		{"ASK", "ask"},
+	}
+	bestIdx, bestLen, action := -1, 0, ""
+	for _, k := range keywords {
+		idx := strings.Index(upper, k.word)
+		if idx >= 0 && (bestIdx < 0 || idx < bestIdx) {
+			bestIdx, bestLen, action = idx, len(k.word), k.action
+		}
+	}
+	if bestIdx < 0 {
 		return Verdict{}
 	}
+	if action == "allow" {
+		return Verdict{Action: "allow"}
+	}
+	return Verdict{Action: action, Reason: cleanReason(line[bestIdx+bestLen:])}
 }
 
-// verdictReason extracts the reason after the keyword of length n, trimming a
-// leading colon/whitespace and capping the length so a runaway model can't bloat
-// the audit row.
-func verdictReason(line string, n int) string {
-	if len(line) <= n {
-		return ""
+// cleanReason trims the text after a verdict keyword: drop a leading colon/space,
+// keep only the first line, and cap the length so a runaway model can't bloat the
+// audit row.
+func cleanReason(s string) string {
+	s = firstNonEmptyLine(s)
+	s = strings.TrimSpace(s)
+	s = strings.TrimLeft(s, ":：")
+	s = strings.TrimSpace(s)
+	if len(s) > 200 {
+		s = s[:200]
 	}
-	r := strings.TrimSpace(line[n:])
-	r = strings.TrimLeft(r, ":：")
-	r = strings.TrimSpace(r)
-	if len(r) > 200 {
-		r = r[:200]
-	}
-	return r
+	return s
 }
 
 func firstNonEmptyLine(text string) string {

intercept/prompt_test.go

@@ -0,0 +1,45 @@
+package intercept
+
+import "testing"
+
+func TestParseVerdict(t *testing.T) {
+	cases := []struct {
+		name       string
+		in         string
+		wantAction string
+		wantReason string
+	}{
+		{"bare allow", "ALLOW", "allow", ""},
+		{"bare deny", "DENY:删除生产文件(D4)", "deny", "删除生产文件(D4)"},
+		{"bare ask", "ASK:归属不明", "ask", "归属不明"},
+		{"lowercase", "deny: rm 系统文件", "deny", "rm 系统文件"},
+		{"fullwidth colon", "DENY：命中D4", "deny", "命中D4"},
+		// The model echoing the prompt's Chinese label must NOT fall through to
+		// unparseable (which would fail-open on a real DENY).
+		{"echoed label deny", "拦截:DENY:命中D5", "deny", "命中D5"},
+		{"echoed label allow", "放行:ALLOW", "allow", ""},
+		{"echoed label ask", "转人工：ASK:无法判断影响面", "ask", "无法判断影响面"},
+		{"leading whitespace/blank line", "\n  ALLOW\n", "allow", ""},
+		{"extra trailing text on later line", "DENY:清库(D4)\n其它解释", "deny", "清库(D4)"},
+		{"unparseable", "我认为这个命令没问题", "", ""},
+		{"empty", "", "", ""},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			v := ParseVerdict(c.in)
+			if v.Action != c.wantAction {
+				t.Errorf("action = %q, want %q (in=%q)", v.Action, c.wantAction, c.in)
+			}
+			if v.Reason != c.wantReason {
+				t.Errorf("reason = %q, want %q (in=%q)", v.Reason, c.wantReason, c.in)
+			}
+		})
+	}
+}
+
+func TestParseVerdictReasonCapped(t *testing.T) {
+	long := "DENY:" + string(make([]byte, 500))
+	if got := ParseVerdict(long); len(got.Reason) > 200 {
+		t.Errorf("reason length = %d, want <= 200", len(got.Reason))
+	}
+}