feat: Improve tool detection by implementing a new content splitting strategy that identifies suspicious prefixes.

api/chat-stream.js

@@ -751,7 +751,7 @@ function processToolSieveChunk(state, chunk, toolNames) {
       continue;
     }
 
-    const [safe, hold] = splitSafeContent(state.pending, 64);
+    const [safe, hold] = splitSafeContentForToolDetection(state.pending);
     if (!safe) {
       break;
     }
@@ -791,12 +791,35 @@ function flushToolSieve(state, toolNames) {
   return events;
 }
 
-function splitSafeContent(s, holdChars) {
-  const chars = Array.from(s || '');
-  if (chars.length <= holdChars) {
-    return ['', s];
+function splitSafeContentForToolDetection(s) {
+  const text = s || '';
+  if (!text) {
+    return ['', ''];
   }
-  return [chars.slice(0, chars.length - holdChars).join(''), chars.slice(chars.length - holdChars).join('')];
+  const suspiciousStart = findSuspiciousPrefixStart(text);
+  if (suspiciousStart < 0) {
+    return [text, ''];
+  }
+  if (suspiciousStart > 0) {
+    return [text.slice(0, suspiciousStart), text.slice(suspiciousStart)];
+  }
+  const chars = Array.from(text);
+  const maxHold = 128;
+  if (chars.length <= maxHold) {
+    return ['', text];
+  }
+  return [chars.slice(0, chars.length - maxHold).join(''), chars.slice(chars.length - maxHold).join('')];
+}
+
+function findSuspiciousPrefixStart(s) {
+  let start = -1;
+  for (const needle of ['{', '[', '```']) {
+    const idx = s.lastIndexOf(needle);
+    if (idx > start) {
+      start = idx;
+    }
+  }
+  return start;
 }
 
 function findToolSegmentStart(s) {

internal/adapter/openai/handler.go

@@ -810,7 +810,7 @@ func processToolSieveChunk(state *toolStreamSieveState, chunk string, toolNames
 			continue
 		}
 
-		safe, hold := splitSafeContent(pending, 64)
+		safe, hold := splitSafeContentForToolDetection(pending)
 		if safe == "" {
 			break
 		}
@@ -842,15 +842,38 @@ func flushToolSieve(state *toolStreamSieveState, toolNames []string) []toolStrea
 	return events
 }
 
-func splitSafeContent(s string, holdRunes int) (safe, hold string) {
-	if s == "" || holdRunes <= 0 {
+func splitSafeContentForToolDetection(s string) (safe, hold string) {
+	if s == "" {
+		return "", ""
+	}
+	suspiciousStart := findSuspiciousPrefixStart(s)
+	if suspiciousStart < 0 {
 		return s, ""
 	}
+	if suspiciousStart > 0 {
+		return s[:suspiciousStart], s[suspiciousStart:]
+	}
 	runes := []rune(s)
-	if len(runes) <= holdRunes {
+	const maxHold = 128
+	if len(runes) <= maxHold {
 		return "", s
 	}
-	return string(runes[:len(runes)-holdRunes]), string(runes[len(runes)-holdRunes:])
+	return string(runes[:len(runes)-maxHold]), string(runes[len(runes)-maxHold:])
+}
+
+func findSuspiciousPrefixStart(s string) int {
+	start := -1
+	indices := []int{
+		strings.LastIndex(s, "{"),
+		strings.LastIndex(s, "["),
+		strings.LastIndex(s, "```"),
+	}
+	for _, idx := range indices {
+		if idx > start {
+			start = idx
+		}
+	}
+	return start
 }
 
 func findToolSegmentStart(s string) int {