diff --git a/backend/app/services/llm_graph_builder.py b/backend/app/services/llm_graph_builder.py
index e87ed6c..bbb2c69 100644
--- a/backend/app/services/llm_graph_builder.py
+++ b/backend/app/services/llm_graph_builder.py
@@ -6,12 +6,15 @@ Replaces Zep with direct LLM calls for entity/relationship extraction
 import os
 import uuid
 import json
+import logging
 from typing import Dict, Any, List, Optional, Callable
 
 from ..utils.llm_client import LLMClient
 from ..models.task import TaskManager, TaskStatus
 from .text_processor import TextProcessor
 
+logger = logging.getLogger('mirofish.llm_graph_builder')
+
 
 EXTRACT_SYSTEM_PROMPT = """You are a knowledge graph extraction engine. Given a text chunk and an ontology schema, extract all entities and relationships.
 
@@ -84,14 +87,19 @@ class LLMGraphBuilderService:
         ontology_json = json.dumps(ontology, indent=2, ensure_ascii=False)
 
         total = len(chunks)
+        success_count = 0
+        fail_count = 0
+        last_error = None
+
         for i, chunk in enumerate(chunks):
             if progress_callback:
                 progress_callback(
-                    f"Extracting from chunk {i+1}/{total}...",
+                    f"Extracting from chunk {i+1}/{total} (ok={success_count}, fail={fail_count})...",
                     (i + 1) / total
                 )
 
             try:
+                logger.info(f"Extracting chunk {i+1}/{total} ({len(chunk)} chars)")
                 result = self.llm.chat_json(
                     messages=[
                         {
@@ -106,10 +114,22 @@ class LLMGraphBuilderService:
                     temperature=0.1,
                     max_tokens=4096
                 )
+                entities = result.get("entities", [])
+                rels = result.get("relationships", [])
+                logger.info(f"Chunk {i+1}: extracted {len(entities)} entities, {len(rels)} relationships")
                 self._merge_extraction(graph_id, result)
+                success_count += 1
             except Exception as e:
+                fail_count += 1
+                last_error = e
+                logger.error(f"Chunk {i+1} extraction failed: {e}")
                 if progress_callback:
-                    progress_callback(f"Chunk {i+1} extraction error: {e}", (i + 1) / total)
+                    progress_callback(f"Chunk {i+1} error: {e}", (i + 1) / total)
+
+        logger.info(f"Extraction complete: {success_count}/{total} succeeded, {fail_count} failed")
+
+        if success_count == 0 and total > 0:
+            raise RuntimeError(f"All {total} chunks failed extraction. Last error: {last_error}")
 
     def _merge_extraction(self, graph_id: str, result: Dict[str, Any]):
         """Merge extracted entities/relationships into the graph, deduplicating by name."""