fix(agent): broaden NO_REPLY detection to cover decorative variants

Models occasionally emit NO_REPLY with trailing underscores, quotes,
markdown emphasis, or short explanations (e.g. `NO_REPLY_`,
`**NO_REPLY**`, `NO_REPLY: offline`). Previous word-boundary check
treated `_` as a word char so `NO_REPLY_` slipped through and was
delivered to end users.

Rewrite IsSilentReply to strip decorative wrappers, then prefix-match
case-insensitively. Token is only rejected when glued to another
word character (e.g. `NO_REPLYING`). Intentional divergence from
upstream #19537 — documented in the doc comment.

internal/agent/sanitize.go

@@ -20,6 +20,7 @@ import (
 	"log/slog"
 	"regexp"
 	"strings"
+	"unicode/utf8"
 
 	"github.com/nextlevelbuilder/goclaw/internal/store"
 )
@@ -377,33 +378,41 @@ func StripConfigLeak(content, agentType string) string {
 
 // --- NO_REPLY detection ---
 
-// IsSilentReply checks if the text is a NO_REPLY token.
-// Matching TS isSilentReplyText() from auto-reply/tokens.ts.
+// IsSilentReply checks if the text begins with a NO_REPLY token.
+//
+// Divergent from TS isSilentReplyText() (exact-match only) — we match broadly:
+// decorative wrappers (`NO_REPLY_`, `"NO_REPLY"`, `**NO_REPLY**`) AND trailing
+// explanations (`NO_REPLY because offline`, `NO_REPLY: note`) suppress delivery.
+// Only requirement: the token is not glued to another word (`NO_REPLYING` is NOT silent).
+// Case-insensitive.
+//
+// Trade-off vs upstream #19537: upstream guards against suppressing substantive
+// replies that end in NO_REPLY. We accept that risk because observed model output
+// leans toward "NO_REPLY + reason" rather than "real reply ending in NO_REPLY".
 func IsSilentReply(text string) bool {
 	trimmed := strings.TrimSpace(text)
 	if trimmed == "" {
 		return false
 	}
+	// Strip decorative wrappers from both ends (quotes, markdown emphasis, punctuation).
+	stripped := strings.Trim(trimmed, "_ \t\n\r.,:;!?\"'`*~#>-()[]{}")
 	const token = "NO_REPLY"
-	// Exact match
-	if trimmed == token {
+	if len(stripped) < len(token) {
+		return false
+	}
+	if !strings.EqualFold(stripped[:len(token)], token) {
+		return false
+	}
+	if len(stripped) == len(token) {
 		return true
 	}
-	// Starts with token followed by non-word char or end
-	if strings.HasPrefix(trimmed, token) {
-		rest := trimmed[len(token):]
-		if rest == "" || !isWordChar(rune(rest[0])) {
-			return true
-		}
-	}
-	// Ends with token preceded by non-word char
-	if strings.HasSuffix(trimmed, token) {
-		before := trimmed[:len(trimmed)-len(token)]
-		if before == "" || !isWordChar(rune(before[len(before)-1])) {
-			return true
-		}
-	}
-	return false
+	// Token must not be glued to another word — next rune must be non-alphanumeric.
+	next, _ := utf8.DecodeRuneInString(stripped[len(token):])
+	return !isAlphaNum(next)
+}
+
+func isAlphaNum(r rune) bool {
+	return (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') || (r >= '0' && r <= '9')
 }
 
 func isWordChar(r rune) bool {

internal/agent/sanitize_silent_reply_test.go

@@ -0,0 +1,49 @@
+package agent
+
+import "testing"
+
+func TestIsSilentReply(t *testing.T) {
+	cases := []struct {
+		name string
+		in   string
+		want bool
+	}{
+		// Exact matches.
+		{"exact", "NO_REPLY", true},
+		{"with whitespace", "  NO_REPLY  ", true},
+		{"with newlines", "\nNO_REPLY\n", true},
+		// Decorative variants — the bug report.
+		{"trailing underscore", "NO_REPLY_", true},
+		{"double trailing underscore", "NO_REPLY__", true},
+		{"leading underscore", "_NO_REPLY", true},
+		{"both underscores", "_NO_REPLY_", true},
+		{"trailing dot", "NO_REPLY.", true},
+		{"trailing bang", "NO_REPLY!", true},
+		{"double-quoted", `"NO_REPLY"`, true},
+		{"single-quoted", "'NO_REPLY'", true},
+		{"backticked", "`NO_REPLY`", true},
+		{"markdown bold", "**NO_REPLY**", true},
+		{"parenthesized", "(NO_REPLY)", true},
+		// Case-insensitive.
+		{"lowercase", "no_reply", true},
+		{"mixed case", "No_Reply", true},
+		// Silent — token + explanation (user intent: prefix-match, divergent from upstream).
+		{"prefix + space + content", "NO_REPLY hello", true},
+		{"prefix + colon + content", "NO_REPLY: offline", true},
+		{"prefix + because", "NO_REPLY because user is away", true},
+		// NOT silent — token glued to another word, or not at start.
+		{"embedded word", "NO_REPLYING", false},
+		{"trailing after content", "Here you go. NO_REPLY", false},
+		{"token mid-sentence", "Hello NO_REPLY world", false},
+		{"empty", "", false},
+		{"whitespace only", "   ", false},
+		{"unrelated text", "no reply needed", false},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			if got := IsSilentReply(c.in); got != c.want {
+				t.Errorf("IsSilentReply(%q) = %v, want %v", c.in, got, c.want)
+			}
+		})
+	}
+}