diff --git a/frontend/composables/chat/useChatSearch.js b/frontend/composables/chat/useChatSearch.js
index 8a92e75..caa2915 100644
--- a/frontend/composables/chat/useChatSearch.js
+++ b/frontend/composables/chat/useChatSearch.js
@@ -457,6 +457,33 @@ if (scope === 'global') {
 }
 return (text.charAt(0) || '?').toString()
 }
+
+const buildTransientSearchTargetContact = ({ username, displayName = '', avatar = '', isGroup = null } = {}) => {
+const u = String(username || '').trim()
+if (!u) return null
+const name = String(displayName || u).trim() || u
+return {
+  id: u,
+  username: u,
+  name,
+  avatar: String(avatar || '').trim() || null,
+  avatarColor: '#4B5563',
+  lastMessage: '',
+  lastMessageTime: '',
+  unreadCount: 0,
+  isGroup: typeof isGroup === 'boolean' ? isGroup : u.endsWith('@chatroom'),
+  isTop: false
+}
+}
+
+const resolveSearchTargetContact = ({ username, displayName = '', avatar = '', isGroup = null } = {}) => {
+const u = String(username || '').trim()
+if (!u) return null
+const existing = contacts.value.find((c) => String(c?.username || '').trim() === u)
+if (existing) return existing
+if (String(selectedContact.value?.username || '').trim() === u) return selectedContact.value
+return buildTransientSearchTargetContact({ username: u, displayName, avatar, isGroup })
+}
 const searchContextBannerText = computed(() => {
 if (!searchContext.value?.active) return ''
 const kind = String(searchContext.value.kind || 'search')
@@ -986,7 +1013,12 @@ if (!hit?.id) return
 const targetUsername = String(hit?.username || selectedContact.value?.username || '').trim()
 if (!targetUsername) return
 
-const targetContact = contacts.value.find((c) => c?.username === targetUsername)
+const targetContact = resolveSearchTargetContact({
+  username: targetUsername,
+  displayName: String(hit?.conversationName || hit?.username || targetUsername).trim(),
+  avatar: String(hit?.conversationAvatar || hit?.senderAvatar || '').trim(),
+  isGroup: targetUsername.endsWith('@chatroom')
+})
 if (targetContact && selectedContact.value?.username !== targetUsername) {
   await selectContact(targetContact, { skipLoadMessages: true })
 }
@@ -1051,7 +1083,12 @@ const u = String(targetUsername || selectedContact.value?.username || '').trim()
 const anchor = String(anchorId || '').trim()
 if (!u || !anchor) return
 
-const targetContact = contacts.value.find((c) => c?.username === u)
+const targetContact = resolveSearchTargetContact({
+  username: u,
+  displayName: String(selectedContact.value?.name || u).trim(),
+  avatar: String(selectedContact.value?.avatar || '').trim(),
+  isGroup: u.endsWith('@chatroom')
+})
 if (targetContact && selectedContact.value?.username !== u) {
   await selectContact(targetContact, { skipLoadMessages: true })
 }
diff --git a/frontend/pages/chat/[[username]].vue b/frontend/pages/chat/[[username]].vue
index 6ec51e6..4ab20f8 100644
--- a/frontend/pages/chat/[[username]].vue
+++ b/frontend/pages/chat/[[username]].vue
@@ -119,6 +119,23 @@ const nextMessageLoadToken = () => {
   return messageLoadSequence
 }
 
+const buildTransientContact = ({ username, name = '', avatar = '', isGroup = null } = {}) => {
+  const u = String(username || '').trim()
+  const displayName = String(name || u).trim() || u
+  return {
+    id: u,
+    username: u,
+    name: displayName,
+    avatar: String(avatar || '').trim() || null,
+    avatarColor: '#4B5563',
+    lastMessage: '',
+    lastMessageTime: '',
+    unreadCount: 0,
+    isGroup: typeof isGroup === 'boolean' ? isGroup : u.endsWith('@chatroom'),
+    isTop: false
+  }
+}
+
 const buildChatPath = (username) => {
   return username ? `/chat/${encodeURIComponent(username)}` : '/chat'
 }
@@ -334,14 +351,28 @@ const selectContact = async (contact, options = {}) => {
 }
 
 const applyRouteSelection = async (options = {}) => {
+  const selectionReason = String(options.reason || 'route-selection').trim() || 'route-selection'
+  const requested = routeUsername.value || ''
+  if ((!contacts.value || contacts.value.length === 0) && requested) {
+    if (selectedContact.value?.username === requested) {
+      return
+    }
+    await selectContact(buildTransientContact({ username: requested }), {
+      syncRoute: false,
+      deferLoadMessages: !!options.deferLoadMessages,
+      reason: `${selectionReason}:transient-route-empty-list`
+    })
+    return
+  }
   if (!contacts.value || contacts.value.length === 0) {
     selectedContact.value = null
     return
   }
 
-  const selectionReason = String(options.reason || 'route-selection').trim() || 'route-selection'
-  const requested = routeUsername.value || ''
   if (requested) {
+    if (selectedContact.value?.username === requested) {
+      return
+    }
     const matched = contacts.value.find((contact) => contact.username === requested)
     if (matched) {
       if (selectedContact.value?.username !== matched.username) {
@@ -353,6 +384,12 @@ const applyRouteSelection = async (options = {}) => {
       }
       return
     }
+    await selectContact(buildTransientContact({ username: requested }), {
+      syncRoute: false,
+      deferLoadMessages: !!options.deferLoadMessages,
+      reason: `${selectionReason}:transient-route`
+    })
+    return
   }
 
   await selectContact(contacts.value[0], {
diff --git a/src/wechat_decrypt_tool/chat_helpers.py b/src/wechat_decrypt_tool/chat_helpers.py
index 603bb81..40b0bad 100644
--- a/src/wechat_decrypt_tool/chat_helpers.py
+++ b/src/wechat_decrypt_tool/chat_helpers.py
@@ -14,6 +14,7 @@ from fastapi import HTTPException
 
 from .app_paths import get_output_databases_dir
 from .logging_config import get_logger
+from .sqlite_diagnostics import collect_sqlite_diagnostics, format_sqlite_diagnostics
 
 try:
     import zstandard as zstd  # type: ignore
@@ -1755,9 +1756,10 @@ def _load_latest_message_previews(account_dir: Path, usernames: list[str]) -> di
 
     session_db_path = Path(account_dir) / "session.db"
     if session_db_path.exists() and remaining:
-        sconn = sqlite3.connect(str(session_db_path))
-        sconn.row_factory = sqlite3.Row
+        sconn: Optional[sqlite3.Connection] = None
         try:
+            sconn = sqlite3.connect(str(session_db_path))
+            sconn.row_factory = sqlite3.Row
             uniq = list(dict.fromkeys([u for u in remaining if u]))
             chunk_size = 900
             for i in range(0, len(uniq), chunk_size):
@@ -1786,10 +1788,24 @@ def _load_latest_message_previews(account_dir: Path, usernames: list[str]) -> di
                         if not u:
                             continue
                         expected_ts_by_user[u] = int(r["last_timestamp"] or 0)
+        except sqlite3.DatabaseError as e:
+            expected_ts_by_user = {}
+            logger.warning(
+                "[sessions.preview] session timestamp lookup failed account=%s db=%s usernames=%s sample_usernames=%s error=%s diag=%s",
+                account_dir.name,
+                str(session_db_path),
+                len(remaining),
+                sorted([u for u in remaining if u])[:5],
+                str(e),
+                format_sqlite_diagnostics(
+                    collect_sqlite_diagnostics(session_db_path, quick_check=True, table_name="SessionTable")
+                ),
+            )
         except Exception:
             expected_ts_by_user = {}
         finally:
-            sconn.close()
+            if sconn is not None:
+                sconn.close()
 
     if _DEBUG_SESSIONS:
         logger.info(
@@ -1800,9 +1816,16 @@ def _load_latest_message_previews(account_dir: Path, usernames: list[str]) -> di
         )
 
     for db_path in db_paths:
-        conn = sqlite3.connect(str(db_path))
-        conn.row_factory = sqlite3.Row
+        conn: Optional[sqlite3.Connection] = None
+        stage = "connect"
+        stage_username = ""
+        stage_table = ""
         try:
+            stage = "connect"
+            conn = sqlite3.connect(str(db_path))
+            conn.row_factory = sqlite3.Row
+
+            stage = "sqlite_master"
             rows = conn.execute("SELECT name FROM sqlite_master WHERE type='table'").fetchall()
             names = [str(r[0]) for r in rows if r and r[0]]
             lower_to_actual = {n.lower(): n for n in names}
@@ -1818,9 +1841,12 @@ def _load_latest_message_previews(account_dir: Path, usernames: list[str]) -> di
 
             conn.text_factory = bytes
             for u, tn in found.items():
+                stage_username = str(u)
+                stage_table = str(tn)
                 quoted = _quote_ident(tn)
                 try:
                     try:
+                        stage = "latest_row_with_name2id"
                         r = conn.execute(
                             "SELECT "
                             "m.local_type, m.message_content, m.compress_content, m.create_time, m.sort_seq, m.local_id, "
@@ -1831,6 +1857,7 @@ def _load_latest_message_previews(account_dir: Path, usernames: list[str]) -> di
                             "LIMIT 1"
                         ).fetchone()
                     except Exception:
+                        stage = "latest_row_without_name2id"
                         r = conn.execute(
                             "SELECT "
                             "local_type, message_content, compress_content, create_time, sort_seq, local_id, '' AS sender_username "
@@ -1838,6 +1865,20 @@ def _load_latest_message_previews(account_dir: Path, usernames: list[str]) -> di
                             "ORDER BY sort_seq DESC, local_id DESC "
                             "LIMIT 1"
                         ).fetchone()
+                except sqlite3.DatabaseError as e:
+                    logger.warning(
+                        "[sessions.preview] latest row query failed account=%s db=%s username=%s table=%s stage=%s error=%s diag=%s",
+                        account_dir.name,
+                        str(db_path),
+                        str(u),
+                        str(tn),
+                        stage,
+                        str(e),
+                        format_sqlite_diagnostics(
+                            collect_sqlite_diagnostics(db_path, quick_check=True, table_name=tn)
+                        ),
+                    )
+                    continue
                 except Exception as e:
                     if _DEBUG_SESSIONS:
                         logger.info(
@@ -1855,6 +1896,7 @@ def _load_latest_message_previews(account_dir: Path, usernames: list[str]) -> di
                 expected_ts = int(expected_ts_by_user.get(u) or 0)
                 if expected_ts > 0 and create_time > 0 and create_time < expected_ts:
                     try:
+                        stage = "latest_row_by_create_time_with_name2id"
                         r2 = conn.execute(
                             "SELECT "
                             "m.local_type, m.message_content, m.compress_content, m.create_time, m.sort_seq, m.local_id, "
@@ -1866,6 +1908,7 @@ def _load_latest_message_previews(account_dir: Path, usernames: list[str]) -> di
                         ).fetchone()
                     except Exception:
                         try:
+                            stage = "latest_row_by_create_time_without_name2id"
                             r2 = conn.execute(
                                 "SELECT "
                                 "local_type, message_content, compress_content, create_time, sort_seq, local_id, '' AS sender_username "
@@ -1873,6 +1916,20 @@ def _load_latest_message_previews(account_dir: Path, usernames: list[str]) -> di
                                 "ORDER BY COALESCE(create_time, 0) DESC, COALESCE(sort_seq, 0) DESC, local_id DESC "
                                 "LIMIT 1"
                             ).fetchone()
+                        except sqlite3.DatabaseError as e:
+                            logger.warning(
+                                "[sessions.preview] latest row requery failed account=%s db=%s username=%s table=%s stage=%s error=%s diag=%s",
+                                account_dir.name,
+                                str(db_path),
+                                str(u),
+                                str(tn),
+                                stage,
+                                str(e),
+                                format_sqlite_diagnostics(
+                                    collect_sqlite_diagnostics(db_path, quick_check=True, table_name=tn)
+                                ),
+                            )
+                            r2 = None
                         except Exception:
                             r2 = None
 
@@ -1900,8 +1957,28 @@ def _load_latest_message_previews(account_dir: Path, usernames: list[str]) -> di
                 prev = best.get(u)
                 if prev is None or sort_key > prev[0]:
                     best[u] = (sort_key, preview)
+        except sqlite3.DatabaseError as e:
+            logger.warning(
+                "[sessions.preview] malformed message db account=%s db=%s stage=%s username=%s table=%s remaining=%s sample_usernames=%s error=%s diag=%s",
+                account_dir.name,
+                str(db_path),
+                stage,
+                stage_username,
+                stage_table,
+                len(remaining),
+                sorted([u for u in remaining if u])[:5],
+                str(e),
+                format_sqlite_diagnostics(
+                    collect_sqlite_diagnostics(db_path, quick_check=True, table_name=(stage_table or None))
+                ),
+            )
+            continue
         finally:
-            conn.close()
+            if conn is not None:
+                try:
+                    conn.close()
+                except Exception:
+                    pass
 
     previews = {u: v[1] for u, v in best.items() if v and v[1]}
     if _DEBUG_SESSIONS:
diff --git a/src/wechat_decrypt_tool/routers/chat.py b/src/wechat_decrypt_tool/routers/chat.py
index f1c423a..b6f2ec0 100644
--- a/src/wechat_decrypt_tool/routers/chat.py
+++ b/src/wechat_decrypt_tool/routers/chat.py
@@ -77,6 +77,7 @@ from ..session_last_message import (
     get_session_last_message_status,
     load_session_last_messages,
 )
+from ..sqlite_diagnostics import collect_sqlite_diagnostics, format_sqlite_diagnostics
 from ..wcdb_realtime import (
     WCDBRealtimeError,
     WCDB_REALTIME,
@@ -2022,12 +2023,18 @@ def _sync_chat_realtime_messages_for_table(
     if backfill_limit > max_scan:
         backfill_limit = max_scan
 
-    msg_conn = sqlite3.connect(str(msg_db_path))
-    msg_conn.row_factory = sqlite3.Row
+    msg_conn: Optional[sqlite3.Connection] = None
+    stage = "connect"
     try:
+        stage = "connect"
+        msg_conn = sqlite3.connect(str(msg_db_path))
+        msg_conn.row_factory = sqlite3.Row
+
+        stage = "resolve_db_storage_paths"
         msg_db_path_real, _res_db_path_real = _resolve_db_storage_message_paths(account_dir, msg_db_path.stem)
         name2id_synced = False
         try:
+            stage = "sync_name2id"
             name2id_result = _sync_output_name2id_from_live(
                 msg_conn,
                 rt_conn=rt_conn,
@@ -2050,12 +2057,14 @@ def _sync_chat_realtime_messages_for_table(
             )
 
         quoted_table = _quote_ident(table_name)
+        stage = "max_local_id"
         row = msg_conn.execute(f"SELECT MAX(local_id) AS mx FROM {quoted_table}").fetchone()
         try:
             max_local_id = int((row["mx"] if row is not None else 0) or 0)
         except Exception:
             max_local_id = 0
 
+        stage = "pragma_table_info"
         cols = msg_conn.execute(f"PRAGMA table_info({quoted_table})").fetchall()
         available_cols = {str(c[1] or "") for c in cols}
         base_cols = [
@@ -2075,6 +2084,7 @@ def _sync_chat_realtime_messages_for_table(
 
         placeholders = ",".join(["?"] * len(insert_cols))
         insert_sql = f"INSERT OR IGNORE INTO {quoted_table} ({','.join(insert_cols)}) VALUES ({placeholders})"
+        stage = "collect_realtime_rows"
         fetch_result = _collect_realtime_rows_for_session(
             trace_id=None,
             account_name=account_dir.name,
@@ -2094,6 +2104,7 @@ def _sync_chat_realtime_messages_for_table(
         backfilled = 0
         if new_rows:
             if not name2id_synced:
+                stage = "upsert_name2id_fallback"
                 _best_effort_upsert_output_name2id_rows(
                     msg_conn,
                     account_name=account_dir.name,
@@ -2102,6 +2113,7 @@ def _sync_chat_realtime_messages_for_table(
 
             values = [tuple(r.get(c) for c in insert_cols) for r in reversed(new_rows)]
             insert_t0 = time.perf_counter()
+            stage = "insert_new_rows"
             msg_conn.executemany(insert_sql, values)
             msg_conn.commit()
             insert_ms = (time.perf_counter() - insert_t0) * 1000.0
@@ -2131,6 +2143,7 @@ def _sync_chat_realtime_messages_for_table(
             if update_values:
                 before_changes = msg_conn.total_changes
                 update_t0 = time.perf_counter()
+                stage = "backfill_packed_info"
                 msg_conn.executemany(
                     f"UPDATE {quoted_table} SET packed_info_data = ? WHERE local_id = ? AND (packed_info_data IS NULL OR length(packed_info_data) = 0)",
                     update_values,
@@ -2187,8 +2200,11 @@ def _sync_chat_realtime_messages_for_table(
 
         if inserted and newest_ts:
             session_db_path = account_dir / "session.db"
-            sconn = sqlite3.connect(str(session_db_path))
+            sconn: Optional[sqlite3.Connection] = None
             try:
+                stage = "open_session_db"
+                sconn = sqlite3.connect(str(session_db_path))
+                stage = "update_session_table"
                 sconn.execute("INSERT OR IGNORE INTO SessionTable(username) VALUES (?)", (username,))
                 sconn.execute(
                     """
@@ -2217,6 +2233,7 @@ def _sync_chat_realtime_messages_for_table(
                     ),
                 )
 
+                stage = "update_session_last_message"
                 _ensure_session_last_message_table(sconn)
                 sconn.execute(
                     """
@@ -2239,8 +2256,25 @@ def _sync_chat_realtime_messages_for_table(
                     ),
                 )
                 sconn.commit()
+            except sqlite3.DatabaseError as e:
+                logger.warning(
+                    "[realtime] malformed session db during sync account=%s username=%s session_db=%s stage=%s error=%s diag=%s",
+                    account_dir.name,
+                    username,
+                    str(session_db_path),
+                    stage,
+                    str(e),
+                    format_sqlite_diagnostics(
+                        collect_sqlite_diagnostics(session_db_path, quick_check=True, table_name="SessionTable")
+                    ),
+                )
+                raise HTTPException(
+                    status_code=500,
+                    detail=f"Malformed session db during realtime sync: {session_db_path.name}",
+                )
             finally:
-                sconn.close()
+                if sconn is not None:
+                    sconn.close()
 
         return {
             "username": username,
@@ -2250,8 +2284,23 @@ def _sync_chat_realtime_messages_for_table(
             "backfilled": int(backfilled),
             "preview": preview or "",
         }
+    except sqlite3.DatabaseError as e:
+        logger.warning(
+            "[realtime] malformed decrypted message db account=%s username=%s db=%s table=%s stage=%s error=%s diag=%s",
+            account_dir.name,
+            username,
+            str(msg_db_path),
+            table_name,
+            stage,
+            str(e),
+            format_sqlite_diagnostics(
+                collect_sqlite_diagnostics(msg_db_path, quick_check=True, table_name=table_name)
+            ),
+        )
+        raise HTTPException(status_code=500, detail=f"Malformed decrypted message db: {msg_db_path.name}")
     finally:
-        msg_conn.close()
+        if msg_conn is not None:
+            msg_conn.close()
 
 
 @router.post("/api/chat/realtime/sync_all", summary="实时消息同步到解密库（全会话增量）")
@@ -2545,20 +2594,24 @@ def sync_chat_realtime_messages_all(
             except HTTPException as e:
                 errors.append(f"{uname}: {str(e.detail or '')}".strip())
                 logger.warning(
-                    "[%s] sync session failed account=%s username=%s err=%s",
+                    "[%s] sync session failed account=%s username=%s db=%s table=%s err=%s",
                     trace_id,
                     account_dir.name,
                     uname,
+                    str(msg_db_path),
+                    str(table_name),
                     str(e.detail or "").strip(),
                 )
                 continue
             except Exception as e:
                 errors.append(f"{uname}: {str(e)}".strip())
                 logger.exception(
-                    "[%s] sync session crashed account=%s username=%s",
+                    "[%s] sync session crashed account=%s username=%s db=%s table=%s",
                     trace_id,
                     account_dir.name,
                     uname,
+                    str(msg_db_path),
+                    str(table_name),
                 )
                 continue
 
@@ -4173,6 +4226,15 @@ def list_chat_sessions(
                 )
                 last_previews = load_session_last_messages(account_dir, usernames)
         except Exception:
+            logger.exception(
+                "[sessions.list] session_last_message preview load failed account=%s preview_mode=%s usernames=%s diag=%s",
+                account_dir.name,
+                preview_mode,
+                len(usernames),
+                format_sqlite_diagnostics(
+                    collect_sqlite_diagnostics(account_dir / "session.db", quick_check=True, table_name="session_last_message")
+                ),
+            )
             last_previews = {}
 
     def _is_generic_location_preview(value: Any) -> bool:
@@ -4189,7 +4251,17 @@ def list_chat_sessions(
             else [u for u in usernames if u and ((u not in last_previews) or _is_generic_location_preview(last_previews.get(u)))]
         )
         if targets:
-            legacy = _load_latest_message_previews(account_dir, targets)
+            try:
+                legacy = _load_latest_message_previews(account_dir, targets)
+            except Exception:
+                logger.exception(
+                    "[sessions.list] legacy latest-message preview fallback failed account=%s preview_mode=%s targets=%s sample_targets=%s; falling back to session summaries",
+                    account_dir.name,
+                    preview_mode,
+                    len(targets),
+                    [str(u) for u in targets[:5]],
+                )
+                legacy = {}
             for u, v in legacy.items():
                 if v:
                     last_previews[u] = v
diff --git a/src/wechat_decrypt_tool/routers/decrypt.py b/src/wechat_decrypt_tool/routers/decrypt.py
index d797441..7ee6126 100644
--- a/src/wechat_decrypt_tool/routers/decrypt.py
+++ b/src/wechat_decrypt_tool/routers/decrypt.py
@@ -59,6 +59,12 @@ async def decrypt_databases(request: DecryptRequest):
             raise HTTPException(status_code=400, detail=results["message"])
 
         logger.info(f"解密完成: 成功 {results['successful_count']}/{results['total_databases']} 个数据库")
+        if int(results.get("diagnostic_warning_count") or 0) > 0:
+            logger.warning(
+                "解密完成但检测到诊断告警: warning_dbs=%s total=%s",
+                int(results.get("diagnostic_warning_count") or 0),
+                int(results.get("total_databases") or 0),
+            )
 
         # 成功解密后，按账号保存数据库密钥（用于前端自动回填）
         try:
@@ -77,6 +83,7 @@ async def decrypt_databases(request: DecryptRequest):
             "processed_files": results["processed_files"],
             "failed_files": results["failed_files"],
             "account_results": results.get("account_results", {}),
+            "diagnostic_warning_count": int(results.get("diagnostic_warning_count") or 0),
         }
 
     except HTTPException:
@@ -160,6 +167,7 @@ async def decrypt_databases_stream(
         processed_files: list[str] = []
         failed_files: list[str] = []
         account_results: dict = {}
+        diagnostic_warning_count = 0
         overall_current = 0
 
         for account, dbs in account_databases.items():
@@ -181,6 +189,8 @@ async def decrypt_databases_stream(
             account_success = 0
             account_processed: list[str] = []
             account_failed: list[str] = []
+            account_db_diagnostics: dict[str, dict] = {}
+            account_diagnostic_warning_count = 0
 
             for db_info in dbs:
                 if await request.is_disconnected():
@@ -223,6 +233,23 @@ async def decrypt_databases_stream(
                     ok = bool(task.result())
                 except Exception:
                     ok = False
+                db_diagnostic = dict(getattr(decryptor, "last_result", {}) or {})
+                if not db_diagnostic:
+                    db_diagnostic = {
+                        "db_path": str(db_path),
+                        "db_name": str(db_name),
+                        "output_path": str(output_path),
+                        "success": bool(ok),
+                    }
+                db_diagnostic["account"] = str(account)
+                account_db_diagnostics[db_name] = db_diagnostic
+
+                if (
+                    (not bool(db_diagnostic.get("success", ok)))
+                    or int(db_diagnostic.get("failed_pages") or 0) > 0
+                    or str(db_diagnostic.get("diagnostic_status") or "") != "ok"
+                ):
+                    account_diagnostic_warning_count += 1
 
                 if ok:
                     account_success += 1
@@ -238,18 +265,25 @@ async def decrypt_databases_stream(
                     status = "fail"
                     msg = "解密失败"
 
-                yield _sse(
-                    {
-                        "type": "progress",
-                        "current": overall_current,
-                        "total": total_databases,
-                        "success_count": success_count,
-                        "fail_count": fail_count,
-                        "current_file": current_file,
-                        "status": status,
-                        "message": msg,
-                    }
-                )
+                payload = {
+                    "type": "progress",
+                    "current": overall_current,
+                    "total": total_databases,
+                    "success_count": success_count,
+                    "fail_count": fail_count,
+                    "current_file": current_file,
+                    "status": status,
+                    "message": msg,
+                }
+                if db_diagnostic:
+                    payload["diagnostic_status"] = str(db_diagnostic.get("diagnostic_status") or "")
+                    payload["page_failures"] = int(db_diagnostic.get("failed_pages") or 0)
+                    if db_diagnostic.get("failed_page_samples"):
+                        payload["failed_page_samples"] = db_diagnostic.get("failed_page_samples")
+                    if db_diagnostic.get("diagnostics"):
+                        payload["diagnostics"] = db_diagnostic.get("diagnostics")
+
+                yield _sse(payload)
 
                 if overall_current % 5 == 0:
                     await asyncio.sleep(0)
@@ -261,7 +295,10 @@ async def decrypt_databases_stream(
                 "output_dir": str(account_output_dir),
                 "processed_files": account_processed,
                 "failed_files": account_failed,
+                "db_diagnostics": account_db_diagnostics,
+                "diagnostic_warning_count": int(account_diagnostic_warning_count),
             }
+            diagnostic_warning_count += int(account_diagnostic_warning_count)
 
             # Build cache table (keep behavior consistent with the POST endpoint).
             if os.environ.get("WECHAT_TOOL_BUILD_SESSION_LAST_MESSAGE", "1") != "0":
@@ -311,6 +348,7 @@ async def decrypt_databases_stream(
             "processed_files": processed_files,
             "failed_files": failed_files,
             "account_results": account_results,
+            "diagnostic_warning_count": int(diagnostic_warning_count),
         }
 
         # Save db key for frontend autofill.
diff --git a/src/wechat_decrypt_tool/sqlite_diagnostics.py b/src/wechat_decrypt_tool/sqlite_diagnostics.py
new file mode 100644
index 0000000..2cfae67
--- /dev/null
+++ b/src/wechat_decrypt_tool/sqlite_diagnostics.py
@@ -0,0 +1,150 @@
+from __future__ import annotations
+
+import json
+import sqlite3
+from pathlib import Path
+from typing import Any, Mapping, Optional
+
+SQLITE_HEADER = b"SQLite format 3\x00"
+
+
+def _clean_text(value: Any, *, limit: int = 240) -> str:
+    text = " ".join(str(value or "").split()).strip()
+    if len(text) > limit:
+        return text[: limit - 3] + "..."
+    return text
+
+
+def _clean_error(exc: BaseException, *, limit: int = 240) -> str:
+    text = _clean_text(exc, limit=limit)
+    if text:
+        return f"{type(exc).__name__}: {text}"
+    return type(exc).__name__
+
+
+def _quote_ident(name: str) -> str:
+    return '"' + str(name or "").replace('"', '""') + '"'
+
+
+def collect_sqlite_diagnostics(
+    path: str | Path,
+    *,
+    quick_check: bool = True,
+    table_name: Optional[str] = None,
+    table_sample_limit: int = 5,
+) -> dict[str, Any]:
+    db_path = Path(path)
+    diagnostics: dict[str, Any] = {
+        "path": str(db_path),
+        "exists": bool(db_path.exists()),
+    }
+
+    if not diagnostics["exists"]:
+        return diagnostics
+
+    try:
+        diagnostics["size"] = int(db_path.stat().st_size)
+    except Exception as exc:
+        diagnostics["size_error"] = _clean_error(exc)
+
+    try:
+        with db_path.open("rb") as f:
+            header = f.read(len(SQLITE_HEADER))
+        diagnostics["header_ok"] = header == SQLITE_HEADER
+        diagnostics["header_hex"] = header.hex()
+    except Exception as exc:
+        diagnostics["header_error"] = _clean_error(exc)
+
+    if not quick_check:
+        return diagnostics
+
+    conn: sqlite3.Connection | None = None
+    try:
+        conn = sqlite3.connect(str(db_path))
+
+        try:
+            row = conn.execute("PRAGMA page_size").fetchone()
+            diagnostics["page_size"] = int((row[0] if row is not None else 0) or 0)
+        except Exception as exc:
+            diagnostics["page_size_error"] = _clean_error(exc)
+
+        try:
+            row = conn.execute("PRAGMA page_count").fetchone()
+            diagnostics["page_count"] = int((row[0] if row is not None else 0) or 0)
+        except Exception as exc:
+            diagnostics["page_count_error"] = _clean_error(exc)
+
+        try:
+            rows = conn.execute("SELECT name FROM sqlite_master WHERE type='table' ORDER BY name").fetchall()
+            table_names = [str(row[0]) for row in rows if row and row[0]]
+            diagnostics["table_count"] = len(table_names)
+            if table_names:
+                diagnostics["tables_sample"] = table_names[: max(int(table_sample_limit or 0), 1)]
+        except Exception as exc:
+            diagnostics["table_list_error"] = _clean_error(exc)
+
+        if table_name:
+            diagnostics["target_table"] = str(table_name)
+            try:
+                cols = conn.execute(f"PRAGMA table_info({_quote_ident(table_name)})").fetchall()
+                diagnostics["target_table_exists"] = bool(cols)
+                if cols:
+                    diagnostics["target_table_columns"] = [
+                        str(col[1])
+                        for col in cols[:8]
+                        if len(col) > 1 and str(col[1] or "").strip()
+                    ]
+            except Exception as exc:
+                diagnostics["target_table_error"] = _clean_error(exc)
+
+        try:
+            rows = conn.execute("PRAGMA quick_check").fetchall()
+            values = [_clean_text(row[0]) for row in rows if row and row[0] is not None]
+            if values:
+                diagnostics["quick_check"] = values[0] if len(values) == 1 else values[:5]
+                diagnostics["quick_check_ok"] = len(values) == 1 and values[0].lower() == "ok"
+                if len(values) > 5:
+                    diagnostics["quick_check_truncated"] = len(values) - 5
+            else:
+                diagnostics["quick_check"] = ""
+                diagnostics["quick_check_ok"] = None
+        except Exception as exc:
+            diagnostics["quick_check_error"] = _clean_error(exc)
+            diagnostics["quick_check_ok"] = False
+    except Exception as exc:
+        diagnostics["connect_error"] = _clean_error(exc)
+    finally:
+        if conn is not None:
+            try:
+                conn.close()
+            except Exception:
+                pass
+
+    return diagnostics
+
+
+def sqlite_diagnostics_status(diagnostics: Mapping[str, Any]) -> str:
+    if not diagnostics:
+        return "not_run"
+    if not diagnostics.get("exists", False):
+        return "missing"
+    if diagnostics.get("header_ok") is False:
+        return "bad_header"
+    if diagnostics.get("connect_error"):
+        return "connect_error"
+    if diagnostics.get("quick_check_error"):
+        return "quick_check_error"
+    if diagnostics.get("quick_check_ok") is False:
+        return "quick_check_failed"
+    if diagnostics.get("quick_check_ok") is True:
+        return "ok"
+    return "header_only"
+
+
+def format_sqlite_diagnostics(diagnostics: Mapping[str, Any]) -> str:
+    compact: dict[str, Any] = {}
+    for key, value in diagnostics.items():
+        if value in (None, "", [], {}):
+            continue
+        compact[str(key)] = value
+    return json.dumps(compact, ensure_ascii=False, sort_keys=True)
diff --git a/src/wechat_decrypt_tool/wechat_decrypt.py b/src/wechat_decrypt_tool/wechat_decrypt.py
index 8afcb13..e714e7d 100644
--- a/src/wechat_decrypt_tool/wechat_decrypt.py
+++ b/src/wechat_decrypt_tool/wechat_decrypt.py
@@ -21,6 +21,7 @@ from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
 from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC
 
 from .app_paths import get_output_databases_dir
+from .sqlite_diagnostics import collect_sqlite_diagnostics, sqlite_diagnostics_status
 
 # 注意：不再支持默认密钥，所有密钥必须通过参数传入
 
@@ -221,6 +222,7 @@ class WeChatDatabaseDecryptor:
             self.key_bytes = bytes.fromhex(key_hex)
         except ValueError:
             raise ValueError("密钥必须是有效的十六进制字符串")
+        self.last_result: dict = {}
     
     def decrypt_database(self, db_path: str, output_path: str) -> bool:
         """解密微信4.x版本数据库
@@ -234,6 +236,79 @@ class WeChatDatabaseDecryptor:
         from .logging_config import get_logger
         logger = get_logger(__name__)
 
+        result = {
+            "db_path": str(db_path),
+            "db_name": Path(str(db_path)).name,
+            "output_path": str(output_path),
+            "success": False,
+            "copied_as_sqlite": False,
+            "input_size": 0,
+            "output_size": 0,
+            "total_pages": 0,
+            "successful_pages": 0,
+            "failed_pages": 0,
+            "failed_page_samples": [],
+            "failure_reasons": {},
+            "diagnostics": {},
+            "diagnostic_status": "not_run",
+            "error": "",
+        }
+        self.last_result = result
+
+        def _append_failed_page(page_num: int, reason: str, error: str = "") -> None:
+            result["failure_reasons"][reason] = int(result["failure_reasons"].get(reason) or 0) + 1
+            if len(result["failed_page_samples"]) >= 8:
+                return
+            item = {"page": int(page_num), "reason": str(reason)}
+            err = " ".join(str(error or "").split()).strip()
+            if err:
+                item["error"] = err[:200]
+            result["failed_page_samples"].append(item)
+
+        def _finalize(success: bool, error: str = "") -> bool:
+            result["success"] = bool(success)
+            if error:
+                result["error"] = " ".join(str(error).split()).strip()
+
+            output_file = Path(str(output_path))
+            if output_file.exists():
+                try:
+                    result["output_size"] = int(output_file.stat().st_size)
+                except Exception:
+                    pass
+
+                diagnostics = collect_sqlite_diagnostics(output_file, quick_check=True)
+                result["diagnostics"] = diagnostics
+                result["diagnostic_status"] = sqlite_diagnostics_status(diagnostics)
+
+            payload = {
+                "db_name": result["db_name"],
+                "db_path": result["db_path"],
+                "output_path": result["output_path"],
+                "success": result["success"],
+                "copied_as_sqlite": result["copied_as_sqlite"],
+                "input_size": result["input_size"],
+                "output_size": result["output_size"],
+                "total_pages": result["total_pages"],
+                "successful_pages": result["successful_pages"],
+                "failed_pages": result["failed_pages"],
+                "failure_reasons": result["failure_reasons"],
+                "failed_page_samples": result["failed_page_samples"],
+                "diagnostic_status": result["diagnostic_status"],
+                "diagnostics": result["diagnostics"],
+                "error": result["error"],
+            }
+            log_fn = logger.info
+            if (
+                (not result["success"])
+                or int(result["failed_pages"] or 0) > 0
+                or str(result["diagnostic_status"] or "") != "ok"
+            ):
+                log_fn = logger.warning
+            log_fn("[decrypt.diagnostic] %s", json.dumps(payload, ensure_ascii=False, sort_keys=True))
+            self.last_result = result
+            return bool(success)
+
         logger.info(f"开始解密数据库: {db_path}")
         
         try:
@@ -241,17 +316,19 @@ class WeChatDatabaseDecryptor:
                 encrypted_data = f.read()
             
             logger.info(f"读取文件大小: {len(encrypted_data)} bytes")
+            result["input_size"] = int(len(encrypted_data))
 
             if len(encrypted_data) < 4096:
                 logger.warning(f"文件太小，跳过解密: {db_path}")
-                return False
+                return _finalize(False, "file_too_small")
 
             # 检查是否已经是解密的数据库
             if encrypted_data.startswith(SQLITE_HEADER):
                 logger.info(f"文件已是SQLite格式，直接复制: {db_path}")
                 with open(output_path, 'wb') as f:
                     f.write(encrypted_data)
-                return True
+                result["copied_as_sqlite"] = True
+                return _finalize(True)
             
             # 提取salt (前16字节)
             salt = encrypted_data[:16]
@@ -295,6 +372,7 @@ class WeChatDatabaseDecryptor:
             total_pages = len(encrypted_data) // page_size
             successful_pages = 0
             failed_pages = 0
+            result["total_pages"] = int(total_pages)
             
             # 逐页解密
             for cur_page in range(total_pages):
@@ -329,6 +407,7 @@ class WeChatDatabaseDecryptor:
                 if stored_hmac != expected_hmac:
                     logger.warning(f"页面 {page_num} HMAC验证失败")
                     failed_pages += 1
+                    _append_failed_page(page_num, "hmac")
                     continue
                 
                 # 提取IV和加密数据用于AES解密
@@ -354,20 +433,32 @@ class WeChatDatabaseDecryptor:
                 except Exception as e:
                     logger.error(f"页面 {page_num} AES解密失败: {e}")
                     failed_pages += 1
+                    _append_failed_page(page_num, "aes", str(e))
                     continue
 
             logger.info(f"解密完成: 成功 {successful_pages} 页, 失败 {failed_pages} 页")
+            result["successful_pages"] = int(successful_pages)
+            result["failed_pages"] = int(failed_pages)
 
             # 写入解密后的文件
             with open(output_path, 'wb') as f:
                 f.write(decrypted_data)
 
             logger.info(f"解密文件大小: {len(decrypted_data)} bytes")
-            return True
+            if failed_pages > 0:
+                logger.warning(
+                    "解密输出包含页失败: db=%s total_pages=%s failed_pages=%s failure_reasons=%s samples=%s",
+                    result["db_name"],
+                    int(total_pages),
+                    int(failed_pages),
+                    json.dumps(result["failure_reasons"], ensure_ascii=False, sort_keys=True),
+                    json.dumps(result["failed_page_samples"], ensure_ascii=False),
+                )
+            return _finalize(True)
 
         except Exception as e:
             logger.error(f"解密失败: {db_path}, 错误: {e}")
-            return False
+            return _finalize(False, str(e))
 
 def decrypt_wechat_databases(db_storage_path: str = None, key: str = None) -> dict:
     """
@@ -493,6 +584,7 @@ def decrypt_wechat_databases(db_storage_path: str = None, key: str = None) -> di
     processed_files = []
     failed_files = []
     account_results = {}
+    diagnostic_warning_count = 0
 
     for account_name, databases in account_databases.items():
         logger.info(f"开始解密账号 {account_name} 的 {len(databases)} 个数据库")
@@ -523,6 +615,8 @@ def decrypt_wechat_databases(db_storage_path: str = None, key: str = None) -> di
         account_success = 0
         account_processed = []
         account_failed = []
+        account_db_diagnostics = {}
+        account_diagnostic_warning_count = 0
 
         for db_info in databases:
             db_path = db_info['path']
@@ -533,7 +627,26 @@ def decrypt_wechat_databases(db_storage_path: str = None, key: str = None) -> di
 
             # 解密数据库
             logger.info(f"解密 {account_name}/{db_name}")
-            if decryptor.decrypt_database(db_path, str(output_path)):
+            ok = decryptor.decrypt_database(db_path, str(output_path))
+            db_diagnostic = dict(getattr(decryptor, "last_result", {}) or {})
+            if not db_diagnostic:
+                db_diagnostic = {
+                    "db_path": str(db_path),
+                    "db_name": str(db_name),
+                    "output_path": str(output_path),
+                    "success": bool(ok),
+                }
+            db_diagnostic["account"] = str(account_name)
+            account_db_diagnostics[db_name] = db_diagnostic
+
+            if (
+                (not bool(db_diagnostic.get("success", ok)))
+                or int(db_diagnostic.get("failed_pages") or 0) > 0
+                or str(db_diagnostic.get("diagnostic_status") or "") != "ok"
+            ):
+                account_diagnostic_warning_count += 1
+
+            if ok:
                 account_success += 1
                 success_count += 1
                 account_processed.append(str(output_path))
@@ -551,8 +664,11 @@ def decrypt_wechat_databases(db_storage_path: str = None, key: str = None) -> di
             "failed": len(databases) - account_success,
             "output_dir": str(account_output_dir),
             "processed_files": account_processed,
-            "failed_files": account_failed
+            "failed_files": account_failed,
+            "db_diagnostics": account_db_diagnostics,
+            "diagnostic_warning_count": int(account_diagnostic_warning_count),
         }
+        diagnostic_warning_count += int(account_diagnostic_warning_count)
 
         # 构建“会话最后一条消息”缓存表：把耗时挪到解密阶段，后续会话列表直接查表
         if os.environ.get("WECHAT_TOOL_BUILD_SESSION_LAST_MESSAGE", "1") != "0":
@@ -586,6 +702,7 @@ def decrypt_wechat_databases(db_storage_path: str = None, key: str = None) -> di
         "failed_files": failed_files,
         "account_results": account_results,  # 新增：按账号的详细结果
         "detected_accounts": detected_accounts,
+        "diagnostic_warning_count": int(diagnostic_warning_count),
     }
 
     logger.info("=" * 60)