feat(metadata): add stripThinkingBlocks function and related tests

internal/ai/compat/client.go

@@ -189,6 +189,7 @@ func (c *Client) extractMetadataWithModel(ctx context.Context, input, model stri
 	}
 
 	metadataText := strings.TrimSpace(resp.Choices[0].Message.Content)
+	metadataText = stripThinkingBlocks(metadataText)
 	metadataText = stripCodeFence(metadataText)
 	metadataText = extractJSONObject(metadataText)
 	if metadataText == "" {
@@ -320,6 +321,30 @@ func extractJSONObject(s string) string {
 	return s[start : end+1]
 }
 
+// stripThinkingBlocks removes <think>...</think> and <thinking>...</thinking>
+// blocks produced by reasoning models (DeepSeek R1, QwQ, etc.) so that the
+// remaining text can be parsed as JSON without interference from thinking content
+// that may itself contain braces.
+func stripThinkingBlocks(s string) string {
+	for _, tag := range []string{"think", "thinking"} {
+		open := "<" + tag + ">"
+		close := "</" + tag + ">"
+		for {
+			start := strings.Index(s, open)
+			if start == -1 {
+				break
+			}
+			end := strings.Index(s[start:], close)
+			if end == -1 {
+				s = s[:start]
+				break
+			}
+			s = s[:start] + s[start+end+len(close):]
+		}
+	}
+	return strings.TrimSpace(s)
+}
+
 func stripCodeFence(value string) string {
 	value = strings.TrimSpace(value)
 	if !strings.HasPrefix(value, "```") {