diff --git a/config.py b/config.py
index 727c756..8ddd31e 100644
--- a/config.py
+++ b/config.py
@@ -32,6 +32,7 @@ class Config:
     OPENAI_URL = os.getenv("OPENAI_URL", "https://api.openai.com/v1/chat/completions")
     OPENAI_MODEL = os.getenv("OPENAI_MODEL", "gpt-4o-mini")
     OPENAI_TIMEOUT = int(os.getenv("OPENAI_TIMEOUT", "30"))
+    OPENAI_LOG_PAYLOAD = os.getenv("OPENAI_LOG_PAYLOAD", "false").lower() == "true"
 
     # YouTube settings
     YOUTUBE_LANGUAGE = os.getenv("YOUTUBE_LANGUAGE", "en")
diff --git a/main.py b/main.py
index 19ce12d..3c60f59 100644
--- a/main.py
+++ b/main.py
@@ -14,6 +14,7 @@ Usage:
 
 import argparse
 import sys
+import logging
 from pathlib import Path
 from datetime import datetime
 from typing import Optional
@@ -53,6 +54,15 @@ def extract_content(url: str, source_type: str) -> dict:
 
 
 def main():
+    logging.basicConfig(
+        level=getattr(logging, Config.LOG_LEVEL.upper(), logging.INFO),
+        format="%(asctime)s %(levelname)s [%(name)s] %(message)s",
+        handlers=[
+            logging.StreamHandler(),
+            logging.FileHandler(Config.LOG_FILE),
+        ],
+    )
+
     parser = argparse.ArgumentParser(
         description="Extract content from URLs and save to Obsidian notes"
     )
diff --git a/summarizer.py b/summarizer.py
index 84d6c77..d9e212b 100644
--- a/summarizer.py
+++ b/summarizer.py
@@ -7,6 +7,7 @@ Uses OPENAI_API_KEY and OPENAI_URL from environment (via Config).
 from __future__ import annotations
 
 import json
+import logging
 from typing import Dict, List
 
 import requests
@@ -18,6 +19,9 @@ class SummarizationError(RuntimeError):
     """Raised when summarization fails."""
 
 
+logger = logging.getLogger(__name__)
+
+
 def summarize_text(text: str, max_points: int = 3) -> Dict[str, List[str] | str]:
     """
     Summarize text into a short summary and key points.
@@ -63,15 +67,28 @@ def summarize_text(text: str, max_points: int = 3) -> Dict[str, List[str] | str]
     }
 
     try:
+        logger.info(
+            "OpenAI request: url=%s model=%s timeout=%ss input_chars=%s",
+            Config.OPENAI_URL,
+            Config.OPENAI_MODEL,
+            Config.OPENAI_TIMEOUT,
+            len(text),
+        )
+        if Config.OPENAI_LOG_PAYLOAD:
+            logger.debug("OpenAI request payload: %s", json.dumps(payload, ensure_ascii=False))
         response = requests.post(
             Config.OPENAI_URL,
             headers=headers,
             json=payload,
             timeout=Config.OPENAI_TIMEOUT,
         )
+        logger.info("OpenAI response: status=%s", response.status_code)
+        if Config.OPENAI_LOG_PAYLOAD:
+            logger.debug("OpenAI response body: %s", response.text)
         response.raise_for_status()
         data = response.json()
     except Exception as exc:
+        logger.exception("OpenAI request failed")
         raise SummarizationError(f"Request failed: {exc}") from exc
 
     try:
@@ -129,14 +146,27 @@ def format_markdown_content(text: str) -> str:
     }
 
     try:
+        logger.info(
+            "OpenAI format request: url=%s model=%s timeout=%ss input_chars=%s",
+            Config.OPENAI_URL,
+            Config.OPENAI_MODEL,
+            Config.OPENAI_TIMEOUT,
+            len(text),
+        )
+        if Config.OPENAI_LOG_PAYLOAD:
+            logger.debug("OpenAI format request payload: %s", json.dumps(payload, ensure_ascii=False))
         response = requests.post(
             Config.OPENAI_URL,
             headers=headers,
             json=payload,
             timeout=Config.OPENAI_TIMEOUT,
         )
+        logger.info("OpenAI format response: status=%s", response.status_code)
+        if Config.OPENAI_LOG_PAYLOAD:
+            logger.debug("OpenAI format response body: %s", response.text)
         response.raise_for_status()
         data = response.json()
         return data["choices"][0]["message"]["content"].strip()
     except Exception as exc:
+        logger.exception("OpenAI format request failed")
         raise SummarizationError(f"Formatting request failed: {exc}") from exc