diff --git a/src/main/db/migrations/0021_aromatic_pyro.sql b/src/main/db/migrations/0021_aromatic_pyro.sql
new file mode 100644
index 0000000..98a5838
--- /dev/null
+++ b/src/main/db/migrations/0021_aromatic_pyro.sql
@@ -0,0 +1,12 @@
+CREATE TABLE `folder_watches` (
+	`id` text PRIMARY KEY NOT NULL,
+	`notebook_id` text NOT NULL,
+	`path` text NOT NULL,
+	`created_at` integer NOT NULL,
+	`updated_at` integer NOT NULL,
+	FOREIGN KEY (`notebook_id`) REFERENCES `notebooks`(`id`) ON UPDATE no action ON DELETE cascade
+);
+--> statement-breakpoint
+CREATE UNIQUE INDEX `idx_folder_watches_notebook_path` ON `folder_watches` (`notebook_id`,`path`);--> statement-breakpoint
+ALTER TABLE `documents` ADD `source_state` text DEFAULT 'available' NOT NULL;--> statement-breakpoint
+ALTER TABLE `documents` ADD `source_mtime_ms` integer;
\ No newline at end of file
diff --git a/src/main/db/migrations/meta/0021_snapshot.json b/src/main/db/migrations/meta/0021_snapshot.json
new file mode 100644
index 0000000..11bb8ef
--- /dev/null
+++ b/src/main/db/migrations/meta/0021_snapshot.json
@@ -0,0 +1,1827 @@
+{
+  "version": "6",
+  "dialect": "sqlite",
+  "id": "baab174f-764a-417c-8f5c-c1a56c3320fe",
+  "prevId": "7afec921-a432-43f3-aafe-054c28f80f89",
+  "tables": {
+    "anki_cards": {
+      "name": "anki_cards",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "text",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "notebook_id": {
+          "name": "notebook_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "title": {
+          "name": "title",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "version": {
+          "name": "version",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": 1
+        },
+        "cards_data": {
+          "name": "cards_data",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "chunk_mapping": {
+          "name": "chunk_mapping",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "metadata": {
+          "name": "metadata",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "status": {
+          "name": "status",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": "'generating'"
+        },
+        "error_message": {
+          "name": "error_message",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "created_at": {
+          "name": "created_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "updated_at": {
+          "name": "updated_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        }
+      },
+      "indexes": {
+        "idx_ankicards_notebook": {
+          "name": "idx_ankicards_notebook",
+          "columns": [
+            "notebook_id",
+            "updated_at"
+          ],
+          "isUnique": false
+        },
+        "idx_ankicards_version": {
+          "name": "idx_ankicards_version",
+          "columns": [
+            "notebook_id",
+            "version"
+          ],
+          "isUnique": false
+        }
+      },
+      "foreignKeys": {
+        "anki_cards_notebook_id_notebooks_id_fk": {
+          "name": "anki_cards_notebook_id_notebooks_id_fk",
+          "tableFrom": "anki_cards",
+          "tableTo": "notebooks",
+          "columnsFrom": [
+            "notebook_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "cascade",
+          "onUpdate": "no action"
+        }
+      },
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "chat_messages": {
+      "name": "chat_messages",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "text",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "session_id": {
+          "name": "session_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "role": {
+          "name": "role",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "content": {
+          "name": "content",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "reasoning_content": {
+          "name": "reasoning_content",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "metadata": {
+          "name": "metadata",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "status": {
+          "name": "status",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "finish_reason": {
+          "name": "finish_reason",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "error": {
+          "name": "error",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "usage": {
+          "name": "usage",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "finished_at": {
+          "name": "finished_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "attempt_of": {
+          "name": "attempt_of",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "created_at": {
+          "name": "created_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        }
+      },
+      "indexes": {
+        "idx_messages_session": {
+          "name": "idx_messages_session",
+          "columns": [
+            "session_id",
+            "created_at"
+          ],
+          "isUnique": false
+        }
+      },
+      "foreignKeys": {
+        "chat_messages_session_id_chat_sessions_id_fk": {
+          "name": "chat_messages_session_id_chat_sessions_id_fk",
+          "tableFrom": "chat_messages",
+          "tableTo": "chat_sessions",
+          "columnsFrom": [
+            "session_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "cascade",
+          "onUpdate": "no action"
+        }
+      },
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "chat_sessions": {
+      "name": "chat_sessions",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "text",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "notebook_id": {
+          "name": "notebook_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "title": {
+          "name": "title",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "summary": {
+          "name": "summary",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "total_tokens": {
+          "name": "total_tokens",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": 0
+        },
+        "status": {
+          "name": "status",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": "'active'"
+        },
+        "parent_session_id": {
+          "name": "parent_session_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "retrieval_scope": {
+          "name": "retrieval_scope",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "created_at": {
+          "name": "created_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "updated_at": {
+          "name": "updated_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        }
+      },
+      "indexes": {
+        "idx_sessions_notebook": {
+          "name": "idx_sessions_notebook",
+          "columns": [
+            "notebook_id",
+            "updated_at"
+          ],
+          "isUnique": false
+        }
+      },
+      "foreignKeys": {
+        "chat_sessions_notebook_id_notebooks_id_fk": {
+          "name": "chat_sessions_notebook_id_notebooks_id_fk",
+          "tableFrom": "chat_sessions",
+          "tableTo": "notebooks",
+          "columnsFrom": [
+            "notebook_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "cascade",
+          "onUpdate": "no action"
+        },
+        "chat_sessions_parent_session_id_chat_sessions_id_fk": {
+          "name": "chat_sessions_parent_session_id_chat_sessions_id_fk",
+          "tableFrom": "chat_sessions",
+          "tableTo": "chat_sessions",
+          "columnsFrom": [
+            "parent_session_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "set null",
+          "onUpdate": "no action"
+        }
+      },
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "chunk_blocks": {
+      "name": "chunk_blocks",
+      "columns": {
+        "chunk_id": {
+          "name": "chunk_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "block_id": {
+          "name": "block_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "start_in_block": {
+          "name": "start_in_block",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "end_in_block": {
+          "name": "end_in_block",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        }
+      },
+      "indexes": {
+        "idx_chunk_blocks_block": {
+          "name": "idx_chunk_blocks_block",
+          "columns": [
+            "block_id"
+          ],
+          "isUnique": false
+        }
+      },
+      "foreignKeys": {
+        "chunk_blocks_chunk_id_chunks_id_fk": {
+          "name": "chunk_blocks_chunk_id_chunks_id_fk",
+          "tableFrom": "chunk_blocks",
+          "tableTo": "chunks",
+          "columnsFrom": [
+            "chunk_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "cascade",
+          "onUpdate": "no action"
+        },
+        "chunk_blocks_block_id_document_blocks_id_fk": {
+          "name": "chunk_blocks_block_id_document_blocks_id_fk",
+          "tableFrom": "chunk_blocks",
+          "tableTo": "document_blocks",
+          "columnsFrom": [
+            "block_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "cascade",
+          "onUpdate": "no action"
+        }
+      },
+      "compositePrimaryKeys": {
+        "chunk_blocks_chunk_id_block_id_pk": {
+          "columns": [
+            "chunk_id",
+            "block_id"
+          ],
+          "name": "chunk_blocks_chunk_id_block_id_pk"
+        }
+      },
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "chunks": {
+      "name": "chunks",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "text",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "document_id": {
+          "name": "document_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "notebook_id": {
+          "name": "notebook_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "content": {
+          "name": "content",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "chunk_index": {
+          "name": "chunk_index",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "start_offset": {
+          "name": "start_offset",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "end_offset": {
+          "name": "end_offset",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "page_start": {
+          "name": "page_start",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "page_end": {
+          "name": "page_end",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "metadata": {
+          "name": "metadata",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "token_count": {
+          "name": "token_count",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "created_at": {
+          "name": "created_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        }
+      },
+      "indexes": {
+        "idx_chunks_document": {
+          "name": "idx_chunks_document",
+          "columns": [
+            "document_id"
+          ],
+          "isUnique": false
+        },
+        "idx_chunks_notebook": {
+          "name": "idx_chunks_notebook",
+          "columns": [
+            "notebook_id"
+          ],
+          "isUnique": false
+        }
+      },
+      "foreignKeys": {
+        "chunks_document_id_documents_id_fk": {
+          "name": "chunks_document_id_documents_id_fk",
+          "tableFrom": "chunks",
+          "tableTo": "documents",
+          "columnsFrom": [
+            "document_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "cascade",
+          "onUpdate": "no action"
+        },
+        "chunks_notebook_id_notebooks_id_fk": {
+          "name": "chunks_notebook_id_notebooks_id_fk",
+          "tableFrom": "chunks",
+          "tableTo": "notebooks",
+          "columnsFrom": [
+            "notebook_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "cascade",
+          "onUpdate": "no action"
+        }
+      },
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "document_blocks": {
+      "name": "document_blocks",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "text",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "document_id": {
+          "name": "document_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "kind": {
+          "name": "kind",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "order": {
+          "name": "order",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "page": {
+          "name": "page",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "level": {
+          "name": "level",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "text": {
+          "name": "text",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "start_offset": {
+          "name": "start_offset",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "end_offset": {
+          "name": "end_offset",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "bbox": {
+          "name": "bbox",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "metadata": {
+          "name": "metadata",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        }
+      },
+      "indexes": {
+        "idx_blocks_document_order": {
+          "name": "idx_blocks_document_order",
+          "columns": [
+            "document_id",
+            "order"
+          ],
+          "isUnique": false
+        },
+        "idx_blocks_document_page": {
+          "name": "idx_blocks_document_page",
+          "columns": [
+            "document_id",
+            "page"
+          ],
+          "isUnique": false
+        }
+      },
+      "foreignKeys": {
+        "document_blocks_document_id_documents_id_fk": {
+          "name": "document_blocks_document_id_documents_id_fk",
+          "tableFrom": "document_blocks",
+          "tableTo": "documents",
+          "columnsFrom": [
+            "document_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "cascade",
+          "onUpdate": "no action"
+        }
+      },
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "documents": {
+      "name": "documents",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "text",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "notebook_id": {
+          "name": "notebook_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "title": {
+          "name": "title",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "type": {
+          "name": "type",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "source_uri": {
+          "name": "source_uri",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "local_file_path": {
+          "name": "local_file_path",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "source_note_id": {
+          "name": "source_note_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "content": {
+          "name": "content",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "structure": {
+          "name": "structure",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "content_hash": {
+          "name": "content_hash",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "mime_type": {
+          "name": "mime_type",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "file_size": {
+          "name": "file_size",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "metadata": {
+          "name": "metadata",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "status": {
+          "name": "status",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": "'pending'"
+        },
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+          "isUnique": false
+        }
+      },
+      "foreignKeys": {
+        "quiz_sessions_quiz_id_quizzes_id_fk": {
+          "name": "quiz_sessions_quiz_id_quizzes_id_fk",
+          "tableFrom": "quiz_sessions",
+          "tableTo": "quizzes",
+          "columnsFrom": [
+            "quiz_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "cascade",
+          "onUpdate": "no action"
+        },
+        "quiz_sessions_notebook_id_notebooks_id_fk": {
+          "name": "quiz_sessions_notebook_id_notebooks_id_fk",
+          "tableFrom": "quiz_sessions",
+          "tableTo": "notebooks",
+          "columnsFrom": [
+            "notebook_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "cascade",
+          "onUpdate": "no action"
+        }
+      },
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    },
+    "quizzes": {
+      "name": "quizzes",
+      "columns": {
+        "id": {
+          "name": "id",
+          "type": "text",
+          "primaryKey": true,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "notebook_id": {
+          "name": "notebook_id",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "title": {
+          "name": "title",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "version": {
+          "name": "version",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": 1
+        },
+        "questions_data": {
+          "name": "questions_data",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "chunk_mapping": {
+          "name": "chunk_mapping",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "metadata": {
+          "name": "metadata",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "status": {
+          "name": "status",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false,
+          "default": "'generating'"
+        },
+        "error_message": {
+          "name": "error_message",
+          "type": "text",
+          "primaryKey": false,
+          "notNull": false,
+          "autoincrement": false
+        },
+        "created_at": {
+          "name": "created_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        },
+        "updated_at": {
+          "name": "updated_at",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true,
+          "autoincrement": false
+        }
+      },
+      "indexes": {
+        "idx_quizzes_notebook": {
+          "name": "idx_quizzes_notebook",
+          "columns": [
+            "notebook_id",
+            "updated_at"
+          ],
+          "isUnique": false
+        },
+        "idx_quizzes_version": {
+          "name": "idx_quizzes_version",
+          "columns": [
+            "notebook_id",
+            "version"
+          ],
+          "isUnique": false
+        }
+      },
+      "foreignKeys": {
+        "quizzes_notebook_id_notebooks_id_fk": {
+          "name": "quizzes_notebook_id_notebooks_id_fk",
+          "tableFrom": "quizzes",
+          "tableTo": "notebooks",
+          "columnsFrom": [
+            "notebook_id"
+          ],
+          "columnsTo": [
+            "id"
+          ],
+          "onDelete": "cascade",
+          "onUpdate": "no action"
+        }
+      },
+      "compositePrimaryKeys": {},
+      "uniqueConstraints": {},
+      "checkConstraints": {}
+    }
+  },
+  "views": {},
+  "enums": {},
+  "_meta": {
+    "schemas": {},
+    "tables": {},
+    "columns": {}
+  },
+  "internal": {
+    "indexes": {}
+  }
+}
\ No newline at end of file
diff --git a/src/main/db/migrations/meta/_journal.json b/src/main/db/migrations/meta/_journal.json
index db04dc0..fdbf467 100644
--- a/src/main/db/migrations/meta/_journal.json
+++ b/src/main/db/migrations/meta/_journal.json
@@ -148,6 +148,13 @@
       "when": 1790587593731,
       "tag": "0020_normal_nextwave",
       "breakpoints": true
+    },
+    {
+      "idx": 21,
+      "version": "6",
+      "when": 1790594238292,
+      "tag": "0021_aromatic_pyro",
+      "breakpoints": true
     }
   ]
 }
\ No newline at end of file
diff --git a/src/main/db/schema.ts b/src/main/db/schema.ts
index 9d8736d..baba4e4 100644
--- a/src/main/db/schema.ts
+++ b/src/main/db/schema.ts
@@ -1,4 +1,4 @@
-import { sqliteTable, text, integer, index, primaryKey } from 'drizzle-orm/sqlite-core'
+import { sqliteTable, text, integer, index, primaryKey, uniqueIndex } from 'drizzle-orm/sqlite-core'
 import type { QuizQuestion } from '../../shared/types/quiz'
 import type {
   ChatExecutionError,
@@ -165,6 +165,15 @@ export const documents = sqliteTable(
     status: text('status', { enum: ['pending', 'processing', 'indexed', 'failed'] })
       .notNull()
       .default('pending'),
+    /**
+     * 来源文件本身的状态（#158），与 `status`（索引状态）分开：
+     * 文件被删是 `missing`，索引只是过期；笔记、摘录、citation 都还在。
+     */
+    sourceState: text('source_state', { enum: ['available', 'missing', 'changed'] })
+      .notNull()
+      .default('available'),
+    /** 上次导入/刷新时来源文件的 mtime（ms）；watch 靠它判断文件是否被改过。 */
+    sourceMtimeMs: integer('source_mtime_ms'),
     errorMessage: text('error_message'),
     chunkCount: integer('chunk_count').default(0),
     createdAt: integer('created_at', { mode: 'timestamp' }).notNull(),
@@ -179,6 +188,31 @@ export const documents = sqliteTable(
 export type Document = typeof documents.$inferSelect
 export type NewDocument = typeof documents.$inferInsert
 
+/**
+ * 被监听的文件夹（#158）。
+ *
+ * 文件夹不是 document（document 是一份来源文件），所以监听关系单独一张表：一个
+ * notebook 可以监听多个文件夹，同一个（notebook, path）不会重复（唯一索引）。
+ */
+export const folderWatches = sqliteTable(
+  'folder_watches',
+  {
+    id: text('id').primaryKey(),
+    notebookId: text('notebook_id')
+      .notNull()
+      .references(() => notebooks.id, { onDelete: 'cascade' }),
+    path: text('path').notNull(),
+    createdAt: integer('created_at', { mode: 'timestamp' }).notNull(),
+    updatedAt: integer('updated_at', { mode: 'timestamp' }).notNull()
+  },
+  (table) => ({
+    uniquePath: uniqueIndex('idx_folder_watches_notebook_path').on(table.notebookId, table.path)
+  })
+)
+
+export type FolderWatch = typeof folderWatches.$inferSelect
+export type NewFolderWatch = typeof folderWatches.$inferInsert
+
 /**
  * 索引尝试记录（#95）。
  *
diff --git a/src/main/index.ts b/src/main/index.ts
index a6e24cf..c3b1497 100644
--- a/src/main/index.ts
+++ b/src/main/index.ts
@@ -137,6 +137,12 @@ app.whenReady().then(async () => {
   knowledgeService = new KnowledgeService(embeddingService)
   Logger.info('Main', 'Knowledge Service initialized')
 
+  // Watched folders (#158): reconcile once so changes made while the app was closed
+  // are picked up, then keep them current live.
+  Logger.info('Main', 'Reconciling watched folders...')
+  await knowledgeService.reconcileWatchedFolders()
+  knowledgeService.startFolderWatching()
+
   // Initialize Update Service
   Logger.info('Main', 'Initializing Update Service...')
   updateService = new UpdateService()
@@ -245,6 +251,7 @@ app.on('before-quit', () => {
   }
 
   Logger.info('Main', 'Closing database connection...')
+  knowledgeService?.stopFolderWatching()
   closeDatabase()
 })
 
diff --git a/src/main/ipc/knowledgeHandlers.ts b/src/main/ipc/knowledgeHandlers.ts
index f624cf9..8b32cc0 100644
--- a/src/main/ipc/knowledgeHandlers.ts
+++ b/src/main/ipc/knowledgeHandlers.ts
@@ -337,64 +337,92 @@ export function registerKnowledgeHandlers(knowledgeService: KnowledgeService) {
   })
 
   // 文件夹导入：一次快照（#98）
-  ipcMain.handle(
-    'knowledge:add-folder',
-    async (event: IpcMainInvokeEvent, args: unknown) => {
-      const validated = await validate(KnowledgeSchemas.addFolder, async (params) => {
-        Logger.debug('KnowledgeHandlers', 'add-folder:', params)
+  ipcMain.handle('knowledge:add-folder', async (event: IpcMainInvokeEvent, args: unknown) => {
+    const validated = await validate(KnowledgeSchemas.addFolder, async (params) => {
+      Logger.debug('KnowledgeHandlers', 'add-folder:', params)
 
-        try {
-          const result = await knowledgeService.addFolder(
-            params.notebookId,
-            params.folderPath,
-            (stage, progress) => {
-              event.sender.send('knowledge:index-progress', {
-                notebookId: params.notebookId,
-                stage,
-                progress
-              })
-            }
-          )
-          return { success: true, ...result }
-        } catch (error) {
-          Logger.error('KnowledgeHandlers', 'Error adding folder:', error)
-          return { success: false, added: [], skipped: [], failed: [], error: (error as Error).message }
+      try {
+        const result = await knowledgeService.addFolder(
+          params.notebookId,
+          params.folderPath,
+          (stage, progress) => {
+            event.sender.send('knowledge:index-progress', {
+              notebookId: params.notebookId,
+              stage,
+              progress
+            })
+          }
+        )
+
+        // 监听（#158）在快照之后建立：持久化监听关系、立刻对齐一次、开始实时监听。
+        if (params.watch) {
+          await knowledgeService.watchFolder(params.notebookId, params.folderPath)
         }
-      })(event, args)
 
-      return validated
-    }
+        return { success: true, ...result }
+      } catch (error) {
+        Logger.error('KnowledgeHandlers', 'Error adding folder:', error)
+        return {
+          success: false,
+          added: [],
+          skipped: [],
+          failed: [],
+          error: (error as Error).message
+        }
+      }
+    })(event, args)
+
+    return validated
+  })
+
+  // 监听文件夹（#158）
+  ipcMain.handle(
+    'knowledge:list-folder-watches',
+    validate(KnowledgeSchemas.listFolderWatches, async (params) => {
+      return knowledgeService.listFolderWatches(params.notebookId)
+    })
   )
 
-  // 批量导入一组文件（#98，拖放/多选共用）
   ipcMain.handle(
-    'knowledge:add-files',
-    async (event: IpcMainInvokeEvent, args: unknown) => {
-      const validated = await validate(KnowledgeSchemas.addFiles, async (params) => {
-        Logger.debug('KnowledgeHandlers', 'add-files:', params.paths.length)
+    'knowledge:unwatch-folder',
+    validate(KnowledgeSchemas.unwatchFolder, async (params) => {
+      knowledgeService.unwatchFolder(params.watchId)
+      return { success: true }
+    })
+  )
 
-        try {
-          const result = await knowledgeService.addDocumentsFromPaths(
-            params.notebookId,
-            params.paths,
-            (stage, progress) => {
-              event.sender.send('knowledge:index-progress', {
-                notebookId: params.notebookId,
-                stage,
-                progress
-              })
-            }
-          )
-          return { success: true, ...result }
-        } catch (error) {
-          Logger.error('KnowledgeHandlers', 'Error adding files:', error)
-          return { success: false, added: [], skipped: [], failed: [], error: (error as Error).message }
+  // 批量导入一组文件（#98，拖放/多选共用）
+  ipcMain.handle('knowledge:add-files', async (event: IpcMainInvokeEvent, args: unknown) => {
+    const validated = await validate(KnowledgeSchemas.addFiles, async (params) => {
+      Logger.debug('KnowledgeHandlers', 'add-files:', params.paths.length)
+
+      try {
+        const result = await knowledgeService.addDocumentsFromPaths(
+          params.notebookId,
+          params.paths,
+          (stage, progress) => {
+            event.sender.send('knowledge:index-progress', {
+              notebookId: params.notebookId,
+              stage,
+              progress
+            })
+          }
+        )
+        return { success: true, ...result }
+      } catch (error) {
+        Logger.error('KnowledgeHandlers', 'Error adding files:', error)
+        return {
+          success: false,
+          added: [],
+          skipped: [],
+          failed: [],
+          error: (error as Error).message
         }
-      })(event, args)
+      }
+    })(event, args)
 
-      return validated
-    }
-  )
+    return validated
+  })
 
   // 打开文档源文件
   ipcMain.handle(
diff --git a/src/main/ipc/validation.ts b/src/main/ipc/validation.ts
index fee8194..e409938 100644
--- a/src/main/ipc/validation.ts
+++ b/src/main/ipc/validation.ts
@@ -146,10 +146,20 @@ export const KnowledgeSchemas = {
     filePath: z.string().min(1, '文件路径不能为空')
   }),
 
-  // 批量/文件夹导入（#98）
+  // 批量/文件夹导入（#98），以及监听文件夹（#158）
   addFolder: z.object({
     notebookId: z.string().min(1, '笔记本 ID 不能为空'),
-    folderPath: z.string().min(1, '文件夹路径不能为空')
+    folderPath: z.string().min(1, '文件夹路径不能为空'),
+    /** true 时把文件夹改为监听来源（#158）：持续对齐，而不仅仅是一次快照。 */
+    watch: z.boolean().optional()
+  }),
+
+  listFolderWatches: z.object({
+    notebookId: z.string().min(1, '笔记本 ID 不能为空')
+  }),
+
+  unwatchFolder: z.object({
+    watchId: z.string().min(1, '监听 ID 不能为空')
   }),
 
   addFiles: z.object({
diff --git a/src/main/services/KnowledgeService.ts b/src/main/services/KnowledgeService.ts
index 9a38a45..521b050 100644
--- a/src/main/services/KnowledgeService.ts
+++ b/src/main/services/KnowledgeService.ts
@@ -5,7 +5,7 @@
 
 import { createHash } from 'crypto'
 import { app } from 'electron'
-import { join, basename } from 'path'
+import { join, basename, sep } from 'path'
 import { mkdir, copyFile, unlink, stat } from 'fs/promises'
 import {
   getDatabase,
@@ -60,6 +60,15 @@ import type {
   Retriever
 } from './retrieval'
 import { WebFetchService } from './WebFetchService'
+import type { WatchedDocument } from './ingestion/folderWatch'
+import {
+  FolderWatchService,
+  addFolderWatch,
+  listFolderWatchesForNotebook,
+  removeFolderWatch,
+  type FolderWatchRecord,
+  type ReconcileResult
+} from './ingestion/folderWatch'
 import { scanFolder } from './ingestion/folderScan'
 import { deleteDocumentChunksFts, ensureChunksFts, indexChunksFts, searchChunksFts } from './fts'
 import { vectorStoreManager } from '../vectorstore'
@@ -182,6 +191,7 @@ export class KnowledgeService {
   private fileParserService: FileParserService
   private webFetchService: WebFetchService
   private knowledgeFilesDir: string
+  private folderWatch: FolderWatchService
 
   constructor(embeddingService: EmbeddingService) {
     this.embeddingService = embeddingService
@@ -192,6 +202,8 @@ export class KnowledgeService {
     // 知识库文件存储目录
     this.knowledgeFilesDir = join(app.getPath('userData'), 'knowledge-files')
     this.ensureKnowledgeFilesDir()
+    // 监听服务只持有本服务的引用，构造本身没有副作用（不会开数据库、不会开始监听）。
+    this.folderWatch = new FolderWatchService(this)
   }
 
   /**
@@ -468,6 +480,9 @@ export class KnowledgeService {
           fileSize: parseResult.metadata?.fileSize as number | undefined,
           metadata: parseResult.metadata,
           errorMessage: null,
+          // 文件回到 available，并记下这次看到的 mtime：watch（#158）靠它判断是否被改过。
+          sourceState: 'available',
+          sourceMtimeMs: (await stat(filePath).catch(() => null))?.mtimeMs,
           updatedAt: new Date()
         })
         .where(eq(documents.id, documentId))
@@ -1175,6 +1190,89 @@ export class KnowledgeService {
     return runsFor(documentId)
   }
 
+  /** 当前所有已注册 loader 认识的扩展名（#98 / #158 的扫描用它）。 */
+  supportedExtensions(): string[] {
+    return this.fileParserService.supportedExtensions()
+  }
+
+  /**
+   * 一个被监听文件夹下的所有 source（#158）。
+   *
+   * 按 `sourceUri` 前缀匹配：文件导入后 sourceUri 仍是原路径，所以「这个文件夹下的
+   * 来源」可以直接算出来，不需要另存一份父子关系。
+   */
+  getWatchedDocuments(notebookId: string, folderPath: string): WatchedDocument[] {
+    const prefix = folderPath.endsWith(sep) ? folderPath : folderPath + sep
+
+    return getDatabase()
+      .select({
+        documentId: documents.id,
+        sourceUri: documents.sourceUri,
+        sourceMtimeMs: documents.sourceMtimeMs,
+        sourceState: documents.sourceState
+      })
+      .from(documents)
+      .where(eq(documents.notebookId, notebookId))
+      .all()
+      .filter(
+        (row): row is WatchedDocument =>
+          typeof row.sourceUri === 'string' &&
+          (row.sourceUri === folderPath || row.sourceUri.startsWith(prefix))
+      )
+  }
+
+  /** 标记来源文件本身的状态（#158）：`missing` 不删行，也不碰笔记与 citation。 */
+  markSourceState(documentId: string, state: 'available' | 'missing' | 'changed'): void {
+    getDatabase()
+      .update(documents)
+      .set({ sourceState: state, updatedAt: new Date() })
+      .where(eq(documents.id, documentId))
+      .run()
+  }
+
+  /**
+   * 来源文件变了：重新拷贝、解析并索引**同一个** documentId（#158）。
+   *
+   * 与 reindex 的区别：reindex 用的是已持久化的 content，而这里文件本身被改过，必须
+   * 重新解析。来源身份不变，所以历史 citation 与摘录仍然指向同一个来源。
+   */
+  async refreshDocumentFromFile(documentId: string, filePath: string): Promise<void> {
+    await this.ingestFile(documentId, filePath, { copyFrom: filePath }, 'reindex')
+  }
+
+  /**
+   * 监听一个文件夹（#158）：持久化监听关系，立刻对齐一次，然后开始实时监听。
+   * 立刻对齐是必要的：watch 建立之前的改动也要被覆盖，而不仅仅依赖之后的 fs 事件。
+   */
+  async watchFolder(notebookId: string, folderPath: string): Promise<ReconcileResult> {
+    addFolderWatch(notebookId, folderPath)
+    const result = await this.folderWatch.reconcileFolder(notebookId, folderPath)
+    this.folderWatch.start()
+    return result
+  }
+
+  unwatchFolder(watchId: string): void {
+    removeFolderWatch(watchId)
+    this.folderWatch.stopWatch(watchId)
+  }
+
+  listFolderWatches(notebookId: string): FolderWatchRecord[] {
+    return listFolderWatchesForNotebook(notebookId)
+  }
+
+  /** 启动时对齐一次（#158）：app 关着的时候发生的改动不会被漏掉。 */
+  async reconcileWatchedFolders(): Promise<ReconcileResult[]> {
+    return this.folderWatch.reconcileAll()
+  }
+
+  startFolderWatching(): void {
+    this.folderWatch.start()
+  }
+
+  stopFolderWatching(): void {
+    this.folderWatch.stop()
+  }
+
   /**
    * 从本地副本重新解析出结构，用于升级前没有持久化 `structure` 的文档。
    *
diff --git a/src/main/services/ingestion/folderDiff.ts b/src/main/services/ingestion/folderDiff.ts
new file mode 100644
index 0000000..6cfc1c8
--- /dev/null
+++ b/src/main/services/ingestion/folderDiff.ts
@@ -0,0 +1,61 @@
+import type { ScannedFile } from './folderScan'
+
+/**
+ * The pure part of folder watching (#158).
+ *
+ * Kept out of `folderWatch.ts` on purpose: that module opens the database (and so
+ * loads Electron), and the decision table below is the part worth unit-testing.
+ * "Changed" and "missing" have to be *determined*, not guessed, so they are a pure
+ * function of the scan and the rows already imported.
+ */
+
+/** A document already imported from a file inside the watched folder. */
+export interface WatchedDocument {
+  documentId: string
+  sourceUri: string
+  sourceMtimeMs: number | null
+  sourceState: 'available' | 'missing' | 'changed'
+}
+
+export interface FolderDiff {
+  /** Files on disk with no document yet. */
+  added: ScannedFile[]
+  /** Files whose mtime differs from what was recorded. */
+  changed: ScannedFile[]
+  /** Documents whose file is gone. */
+  missing: WatchedDocument[]
+  /** Documents previously not `available` whose file is back, mtime unchanged. */
+  restored: WatchedDocument[]
+}
+
+export function diffFolder(
+  scanned: readonly ScannedFile[],
+  existing: readonly WatchedDocument[]
+): FolderDiff {
+  const byPath = new Map(existing.map((document) => [document.sourceUri, document]))
+  const seen = new Set<string>()
+
+  const added: ScannedFile[] = []
+  const changed: ScannedFile[] = []
+  const restored: WatchedDocument[] = []
+
+  for (const file of scanned) {
+    seen.add(file.path)
+    const document = byPath.get(file.path)
+
+    if (!document) {
+      added.push(file)
+      continue
+    }
+
+    const mtimeChanged = document.sourceMtimeMs === null || document.sourceMtimeMs !== file.mtimeMs
+    if (mtimeChanged) {
+      changed.push(file)
+    } else if (document.sourceState !== 'available') {
+      restored.push(document)
+    }
+  }
+
+  const missing = existing.filter((document) => !seen.has(document.sourceUri))
+  return { added, changed, missing, restored }
+}
diff --git a/src/main/services/ingestion/folderScan.ts b/src/main/services/ingestion/folderScan.ts
index ff29c3c..ae567ae 100644
--- a/src/main/services/ingestion/folderScan.ts
+++ b/src/main/services/ingestion/folderScan.ts
@@ -1,4 +1,4 @@
-import { readdir } from 'fs/promises'
+import { readdir, stat } from 'fs/promises'
 import { extname, join, relative } from 'path'
 
 /**
@@ -15,6 +15,8 @@ export interface ScannedFile {
   path: string
   /** Path relative to the scanned root, for stable ordering and messages. */
   relativePath: string
+  /** File modification time in ms — what a watch compares to decide "changed" (#158). */
+  mtimeMs: number
 }
 
 /**
@@ -46,7 +48,8 @@ export async function scanFolder(
 
       const extension = extname(entry.name).toLowerCase().slice(1)
       if (allowed.has(extension)) {
-        files.push({ path: fullPath, relativePath: relative(dir, fullPath) })
+        const info = await stat(fullPath)
+        files.push({ path: fullPath, relativePath: relative(dir, fullPath), mtimeMs: info.mtimeMs })
       }
     }
   }
diff --git a/src/main/services/ingestion/folderWatch.ts b/src/main/services/ingestion/folderWatch.ts
new file mode 100644
index 0000000..3262c31
--- /dev/null
+++ b/src/main/services/ingestion/folderWatch.ts
@@ -0,0 +1,217 @@
+import { watch, type FSWatcher } from 'fs'
+import { eq } from 'drizzle-orm'
+import { getDatabase } from '../../db'
+import { folderWatches } from '../../db/schema'
+import type { KnowledgeService } from '../KnowledgeService'
+import { scanFolder, type ScannedFile } from './folderScan'
+import { diffFolder } from './folderDiff'
+
+// Re-exported so the rest of the app keeps importing the watcher from one place;
+// the pure decision table lives in `folderDiff.ts` so it is testable without Electron.
+export { diffFolder, type FolderDiff, type WatchedDocument } from './folderDiff'
+
+/**
+ * Watched folders (#158).
+ *
+ * A folder import (#98) is a snapshot; this is what keeps a folder current. The
+ * two are deliberately separate code paths: the snapshot never runs on a timer,
+ * and the watcher never re-implements parsing.
+ *
+ * The division of labour:
+ *
+ *   filesystem event      → (debounced) reconcile that one folder
+ *   new file              → enqueue an import run (#95)
+ *   changed file          → re-parse + re-index the SAME documentId
+ *   deleted file          → mark the source `missing`; never delete the row,
+ *                           its notes, its excerpts or its citations
+ *
+ * Reconciliation is a *diff*, not a re-import: an unchanged file costs one stat
+ * and nothing else.
+ */
+
+export interface FolderWatchRecord {
+  id: string
+  notebookId: string
+  path: string
+}
+
+export function listFolderWatches(): FolderWatchRecord[] {
+  return getDatabase()
+    .select({
+      id: folderWatches.id,
+      notebookId: folderWatches.notebookId,
+      path: folderWatches.path
+    })
+    .from(folderWatches)
+    .all()
+}
+
+export function listFolderWatchesForNotebook(notebookId: string): FolderWatchRecord[] {
+  return getDatabase()
+    .select({
+      id: folderWatches.id,
+      notebookId: folderWatches.notebookId,
+      path: folderWatches.path
+    })
+    .from(folderWatches)
+    .where(eq(folderWatches.notebookId, notebookId))
+    .all()
+}
+
+/** Add a watch. Adding the same folder twice is a no-op, not a second row. */
+export function addFolderWatch(notebookId: string, path: string): FolderWatchRecord {
+  const existing = listFolderWatchesForNotebook(notebookId).find((entry) => entry.path === path)
+  if (existing) return existing
+
+  const now = new Date()
+  const id = `watch_${Date.now()}_${Math.random().toString(36).slice(2, 9)}`
+  getDatabase()
+    .insert(folderWatches)
+    .values({ id, notebookId, path, createdAt: now, updatedAt: now })
+    .run()
+
+  return { id, notebookId, path }
+}
+
+export function removeFolderWatch(watchId: string): void {
+  getDatabase().delete(folderWatches).where(eq(folderWatches.id, watchId)).run()
+}
+
+export interface ReconcileResult {
+  notebookId: string
+  path: string
+  added: number
+  changed: number
+  missing: number
+  restored: number
+}
+
+/**
+ * Keeps watched folders current.
+ *
+ * `reconcileAll()` runs on launch, so a change made while the app was closed is
+ * not missed; `start()` adds live watchers on top of that. Both funnel through
+ * `reconcileFolder()`, which is the only place that decides what changed.
+ */
+export class FolderWatchService {
+  private readonly watchers = new Map<string, FSWatcher>()
+  private readonly timers = new Map<string, NodeJS.Timeout>()
+  private stopped = false
+
+  constructor(private readonly knowledgeService: KnowledgeService) {}
+
+  async reconcileAll(): Promise<ReconcileResult[]> {
+    const results: ReconcileResult[] = []
+    for (const watch of listFolderWatches()) {
+      results.push(await this.reconcileFolder(watch.notebookId, watch.path))
+    }
+    return results
+  }
+
+  async reconcileFolder(notebookId: string, folderPath: string): Promise<ReconcileResult> {
+    const extensions = this.knowledgeService.supportedExtensions()
+    let scanned: ScannedFile[]
+    try {
+      scanned = await scanFolder(folderPath, extensions)
+    } catch {
+      // A watched folder can disappear (unmounted drive, deleted folder). Every
+      // source under it becomes `missing`; nothing is deleted.
+      scanned = []
+    }
+
+    const existing = this.knowledgeService.getWatchedDocuments(notebookId, folderPath)
+    const diff = diffFolder(scanned, existing)
+
+    for (const document of diff.missing) {
+      this.knowledgeService.markSourceState(document.documentId, 'missing')
+    }
+    for (const document of diff.restored) {
+      this.knowledgeService.markSourceState(document.documentId, 'available')
+    }
+    for (const file of diff.changed) {
+      const document = existing.find((entry) => entry.sourceUri === file.path)
+      if (!document) continue
+      try {
+        await this.knowledgeService.refreshDocumentFromFile(document.documentId, file.path)
+      } catch {
+        // A refresh failure is recorded on the ingestion run and leaves the old
+        // index in place (#95); reconciliation itself must not throw.
+      }
+    }
+
+    if (diff.added.length > 0) {
+      await this.knowledgeService.addDocumentsFromPaths(
+        notebookId,
+        diff.added.map((file) => file.path)
+      )
+    }
+
+    return {
+      notebookId,
+      path: folderPath,
+      added: diff.added.length,
+      changed: diff.changed.length,
+      missing: diff.missing.length,
+      restored: diff.restored.length
+    }
+  }
+
+  /** Live watchers over the persisted watches. Safe to call once at startup. */
+  start(): void {
+    for (const record of listFolderWatches()) {
+      this.watchFolder(record)
+    }
+  }
+
+  stop(): void {
+    this.stopped = true
+    for (const timer of this.timers.values()) clearTimeout(timer)
+    this.timers.clear()
+    for (const watcher of this.watchers.values()) watcher.close()
+    this.watchers.clear()
+  }
+
+  /** 停止监听单个文件夹（取消监听时）；行还在时下次 `start()` 不会把它加回来。 */
+  stopWatch(watchId: string): void {
+    const timer = this.timers.get(watchId)
+    if (timer) clearTimeout(timer)
+    this.timers.delete(watchId)
+
+    const watcher = this.watchers.get(watchId)
+    if (watcher) watcher.close()
+    this.watchers.delete(watchId)
+  }
+
+  private watchFolder(record: FolderWatchRecord): void {
+    if (this.watchers.has(record.id)) return
+
+    try {
+      // `recursive` is supported on macOS/Windows and on Linux since Node 20. If a
+      // platform refuses it, the launch-time reconcile still keeps the folder
+      // current — only live updates are lost, and that is not silent: it is this catch.
+      const watcher = watch(record.path, { recursive: true }, () => this.debounce(record))
+      watcher.on('error', () => {
+        watcher.close()
+        this.watchers.delete(record.id)
+      })
+      this.watchers.set(record.id, watcher)
+    } catch {
+      // Folder gone or recursive unsupported: reconcile-on-launch remains the fallback.
+    }
+  }
+
+  /** One folder's burst of events becomes one reconcile. */
+  private debounce(watch: FolderWatchRecord): void {
+    if (this.stopped) return
+    const pending = this.timers.get(watch.id)
+    if (pending) clearTimeout(pending)
+
+    this.timers.set(
+      watch.id,
+      setTimeout(() => {
+        this.timers.delete(watch.id)
+        void this.reconcileFolder(watch.notebookId, watch.path)
+      }, 800)
+    )
+  }
+}
diff --git a/src/main/smokeTest.ts b/src/main/smokeTest.ts
index e07c777..70555c4 100644
--- a/src/main/smokeTest.ts
+++ b/src/main/smokeTest.ts
@@ -757,6 +757,41 @@ async function runChecks(): Promise<string[]> {
   )
   pass('a folder import is a snapshot: unsupported files are skipped and re-import is a no-op')
 
+  // --- watching a folder keeps it current, and never deletes (#158) -----------
+  const watchedFolder = mkdtempSync(join(tmpdir(), 'knownote-watch-'))
+  copyFileSync(join(fixtures, 'sample.md'), join(watchedFolder, 'watched.md'))
+  await knowledge.watchFolder(reindexNotebook, watchedFolder)
+
+  const watchedDoc = knowledge
+    .getDocuments(reindexNotebook)
+    .find((doc) => doc.sourceUri === join(watchedFolder, 'watched.md'))
+  assert(watchedDoc, 'watching a folder did not import the file already in it')
+
+  // A new file appears: reconcile imports it without the user doing anything.
+  copyFileSync(join(fixtures, 'sample.md'), join(watchedFolder, 'added.md'))
+  await knowledge.reconcileWatchedFolders()
+  assert(
+    knowledge
+      .getDocuments(reindexNotebook)
+      .some((doc) => doc.sourceUri === join(watchedFolder, 'added.md')),
+    'reconcile did not import a file added to a watched folder'
+  )
+
+  // A file disappears: the source is marked missing; the row, its chunks and its
+  // citations survive, because a citation is a snapshot.
+  rmSync(join(watchedFolder, 'watched.md'))
+  await knowledge.reconcileWatchedFolders()
+  const missingDoc = knowledge.getDocument(watchedDoc.id)
+  assert(
+    missingDoc?.sourceState === 'missing',
+    `a deleted file left source_state=${missingDoc?.sourceState}`
+  )
+  assert(
+    knowledge.getDocumentChunks(watchedDoc.id).length > 0,
+    'marking a source missing destroyed its derived index'
+  )
+  pass('a watched folder picks up new files and marks deleted ones missing without deleting them')
+
   // --- a failed re-index leaves the previous index usable (#95) ---------------
   // The failure this guards: `reindexDocument()` used to clear the derived index
   // *before* embedding, so an embedding failure at 70% left the document with no
diff --git a/src/preload/index.d.ts b/src/preload/index.d.ts
index 18bdb80..cef081e 100644
--- a/src/preload/index.d.ts
+++ b/src/preload/index.d.ts
@@ -260,8 +260,17 @@ declare global {
           notebookId: string,
           filePath: string
         ) => Promise<{ success: boolean; documentId?: string; error?: string }>
-        /** 文件夹导入：一次快照（#98）。 */
-        addFolder: (notebookId: string, folderPath: string) => Promise<BatchImportOutcome>
+        /** 文件夹导入：一次快照；`watch` 为 true 时同时改为监听来源（#158）。 */
+        addFolder: (
+          notebookId: string,
+          folderPath: string,
+          watch?: boolean
+        ) => Promise<BatchImportOutcome>
+        /** 监听列表（#158）。 */
+        listFolderWatches: (
+          notebookId: string
+        ) => Promise<Array<{ id: string; notebookId: string; path: string }>>
+        unwatchFolder: (watchId: string) => Promise<{ success: boolean }>
         /** 批量导入一组文件（#98）：拖放与多选共用。 */
         addFiles: (notebookId: string, paths: string[]) => Promise<BatchImportOutcome>
         /** 拖放的 `File` → 绝对路径（#98）。 */
diff --git a/src/preload/index.ts b/src/preload/index.ts
index 191c69a..f24b510 100644
--- a/src/preload/index.ts
+++ b/src/preload/index.ts
@@ -168,8 +168,11 @@ const api = {
       ipcRenderer.invoke('knowledge:add-document', { notebookId, options }),
     addDocumentFromFile: (notebookId: string, filePath: string) =>
       ipcRenderer.invoke('knowledge:add-document-from-file', { notebookId, filePath }),
-    addFolder: (notebookId: string, folderPath: string) =>
-      ipcRenderer.invoke('knowledge:add-folder', { notebookId, folderPath }),
+    addFolder: (notebookId: string, folderPath: string, watch = false) =>
+      ipcRenderer.invoke('knowledge:add-folder', { notebookId, folderPath, watch }),
+    listFolderWatches: (notebookId: string) =>
+      ipcRenderer.invoke('knowledge:list-folder-watches', { notebookId }),
+    unwatchFolder: (watchId: string) => ipcRenderer.invoke('knowledge:unwatch-folder', { watchId }),
     addFiles: (notebookId: string, paths: string[]) =>
       ipcRenderer.invoke('knowledge:add-files', { notebookId, paths }),
     /**
diff --git a/src/renderer/src/components/notebook/SourcePanel.tsx b/src/renderer/src/components/notebook/SourcePanel.tsx
index 7268052..366331b 100644
--- a/src/renderer/src/components/notebook/SourcePanel.tsx
+++ b/src/renderer/src/components/notebook/SourcePanel.tsx
@@ -11,7 +11,8 @@ import {
   ArrowLeft,
   Quote,
   ExternalLink,
-  FolderOpen
+  FolderOpen,
+  FolderSync
 } from 'lucide-react'
 import { toast } from 'sonner'
 import { useKnowledgeStore, setupKnowledgeListeners } from '../../store/knowledgeStore'
@@ -27,10 +28,7 @@ import { Card } from '../ui/card'
 import { PanelHeader } from '../ui/panel-header'
 import DocumentList from './source/DocumentList'
 import SourceReader from './source/reader/SourceReader'
-import type {
-  KnowledgeDocument,
-  BatchImportOutcome
-} from '../../../../shared/types/knowledge'
+import type { KnowledgeDocument, BatchImportOutcome } from '../../../../shared/types/knowledge'
 import type { ReaderAnchor, ReaderSelection } from '../../../../shared/types/source'
 import {
   selectionToSourceAnchor,
@@ -511,20 +509,23 @@ export default function SourcePanel(): ReactElement {
     reportBatch(await addFiles(notebookId, files))
   }, [notebookId, hasEmbeddingModel, selectFiles, addFiles, reportBatch, t])
 
-  // 处理文件夹导入（#98）：一次快照，不是监听（监听是 #158）
-  const handleFolderUpload = useCallback(async () => {
-    if (!notebookId) return
-    if (!hasEmbeddingModel) {
-      alert(t('noEmbeddingModelConfigured'))
-      return
-    }
+  // 处理文件夹导入（#98 快照 / #158 监听）
+  const handleFolderUpload = useCallback(
+    async (watch: boolean) => {
+      if (!notebookId) return
+      if (!hasEmbeddingModel) {
+        alert(t('noEmbeddingModelConfigured'))
+        return
+      }
 
-    const folders = await selectFolder()
-    setShowAddMenu(false)
-    for (const folder of folders) {
-      reportBatch(await addFolder(notebookId, folder))
-    }
-  }, [notebookId, hasEmbeddingModel, selectFolder, addFolder, reportBatch, t])
+      const folders = await selectFolder()
+      setShowAddMenu(false)
+      for (const folder of folders) {
+        reportBatch(await addFolder(notebookId, folder, watch))
+      }
+    },
+    [notebookId, hasEmbeddingModel, selectFolder, addFolder, reportBatch, t]
+  )
 
   // 拖放文件/文件夹（#98）。Electron 39 下路径必须由 preload 的 webUtils 给出。
   const handleDrop = useCallback(
@@ -764,13 +765,21 @@ export default function SourcePanel(): ReactElement {
                       {t('uploadFile')}
                     </Button>
                     <Button
-                      onClick={handleFolderUpload}
+                      onClick={() => void handleFolderUpload(false)}
                       variant="ghost"
                       className="w-full justify-start text-sm font-normal"
                     >
                       <FolderOpen className="w-4 h-4" />
                       {t('uploadFolder')}
                     </Button>
+                    <Button
+                      onClick={() => void handleFolderUpload(true)}
+                      variant="ghost"
+                      className="w-full justify-start text-sm font-normal"
+                    >
+                      <FolderSync className="w-4 h-4" />
+                      {t('watchFolder')}
+                    </Button>
                     <Button
                       onClick={() => {
                         setModalType('url')
diff --git a/src/renderer/src/components/notebook/source/DocumentList.tsx b/src/renderer/src/components/notebook/source/DocumentList.tsx
index 8f73381..ad32ca1 100644
--- a/src/renderer/src/components/notebook/source/DocumentList.tsx
+++ b/src/renderer/src/components/notebook/source/DocumentList.tsx
@@ -162,6 +162,10 @@ function DocumentItem({
               {document.errorMessage}
             </p>
           )}
+          {/* 来源文件不在了（#158）：citation / 摘录仍然有效，只是文件暂时取不到。 */}
+          {document.sourceState === 'missing' && (
+            <p className="text-xs text-subtle-foreground">{t('sourceMissing')}</p>
+          )}
         </div>
       </button>
 
diff --git a/src/renderer/src/locales/en-US/ui.json b/src/renderer/src/locales/en-US/ui.json
index f5d6b82..607b48e 100644
--- a/src/renderer/src/locales/en-US/ui.json
+++ b/src/renderer/src/locales/en-US/ui.json
@@ -86,6 +86,8 @@
   "retryDocument": "Try again",
   "reindexDocument": "Re-index",
   "uploadFolder": "Add folder",
+  "watchFolder": "Watch folder",
+  "sourceMissing": "The file is no longer at its path",
   "dropToImport": "Drop files or a folder to import",
   "importAdded": "Imported {{count}}",
   "importSkipped": "skipped {{count}} (already imported)",
diff --git a/src/renderer/src/locales/zh-CN/ui.json b/src/renderer/src/locales/zh-CN/ui.json
index dbbb6e1..89e74ff 100644
--- a/src/renderer/src/locales/zh-CN/ui.json
+++ b/src/renderer/src/locales/zh-CN/ui.json
@@ -86,6 +86,8 @@
   "retryDocument": "重试",
   "reindexDocument": "重建索引",
   "uploadFolder": "添加文件夹",
+  "watchFolder": "监听文件夹",
+  "sourceMissing": "文件已不在原路径",
   "dropToImport": "拖入文件或文件夹以导入",
   "importAdded": "已导入 {{count}} 个",
   "importSkipped": "跳过 {{count}} 个（已存在）",
diff --git a/src/renderer/src/store/knowledgeStore.ts b/src/renderer/src/store/knowledgeStore.ts
index a49c1d8..31bb093 100644
--- a/src/renderer/src/store/knowledgeStore.ts
+++ b/src/renderer/src/store/knowledgeStore.ts
@@ -70,8 +70,12 @@ interface KnowledgeStore {
     notebookId: string,
     noteId: string
   ) => Promise<{ success: boolean; documentId?: string; error?: string }>
-  /** 文件夹导入：一次快照（#98）。 */
-  addFolder: (notebookId: string, folderPath: string) => Promise<BatchImportOutcome>
+  /** 文件夹导入：一次快照；`watch` 为 true 时同时改为监听来源（#158）。 */
+  addFolder: (
+    notebookId: string,
+    folderPath: string,
+    watch?: boolean
+  ) => Promise<BatchImportOutcome>
   /** 批量导入一组文件（#98）：拖放与多选共用同一路径。 */
   addFiles: (notebookId: string, paths: string[]) => Promise<BatchImportOutcome>
   selectFolder: () => Promise<string[]>
@@ -207,9 +211,9 @@ export const useKnowledgeStore = create<KnowledgeStore>()((set, get) => ({
   },
 
   // 文件夹 / 批量导入（#98）
-  addFolder: async (notebookId, folderPath) => {
+  addFolder: async (notebookId, folderPath, watch = false) => {
     set({ isIndexing: true, error: null })
-    const result = await window.api.knowledge.addFolder(notebookId, folderPath)
+    const result = await window.api.knowledge.addFolder(notebookId, folderPath, watch)
     await refreshAfterImport(notebookId, result, set, get)
     return result
   },
diff --git a/test/folderDiff.test.ts b/test/folderDiff.test.ts
new file mode 100644
index 0000000..a25031d
--- /dev/null
+++ b/test/folderDiff.test.ts
@@ -0,0 +1,109 @@
+import { test } from 'node:test'
+import assert from 'node:assert/strict'
+import { diffFolder, type WatchedDocument } from '../src/main/services/ingestion/folderDiff.ts'
+import type { ScannedFile } from '../src/main/services/ingestion/folderScan.ts'
+
+/**
+ * The decision table behind watching a folder (#158).
+ *
+ * This is the part that must not be guessed: a document is re-indexed only when
+ * its file's mtime actually changed, and a document is only marked `missing` when
+ * its file is really gone. Everything downstream (re-index, mark missing) is a
+ * consequence of this diff.
+ */
+
+const file = (path: string, mtimeMs: number): ScannedFile => ({ path, relativePath: path, mtimeMs })
+
+const doc = (
+  path: string,
+  mtimeMs: number | null,
+  sourceState: WatchedDocument['sourceState'] = 'available'
+): WatchedDocument => ({
+  documentId: `doc_${path}`,
+  sourceUri: path,
+  sourceMtimeMs: mtimeMs,
+  sourceState
+})
+
+test('a file with no document is added', () => {
+  const diff = diffFolder([file('/p/a.pdf', 100)], [])
+  assert.deepEqual(
+    diff.added.map((f) => f.path),
+    ['/p/a.pdf']
+  )
+  assert.equal(diff.changed.length + diff.missing.length + diff.restored.length, 0)
+})
+
+test('an mtime change is changed, not added', () => {
+  const diff = diffFolder([file('/p/a.pdf', 200)], [doc('/p/a.pdf', 100)])
+  assert.deepEqual(
+    diff.changed.map((f) => f.path),
+    ['/p/a.pdf']
+  )
+  assert.equal(diff.added.length, 0)
+})
+
+test('an unchanged file is neither added nor changed', () => {
+  const diff = diffFolder([file('/p/a.pdf', 100)], [doc('/p/a.pdf', 100)])
+  assert.equal(
+    diff.added.length + diff.changed.length + diff.missing.length + diff.restored.length,
+    0
+  )
+})
+
+test('a document with no mtime recorded counts as changed, not as current', () => {
+  // An older row has no mtime; the first reconcile after the upgrade must treat it
+  // as out of date rather than assume it is current.
+  const diff = diffFolder([file('/p/a.pdf', 100)], [doc('/p/a.pdf', null)])
+  assert.deepEqual(
+    diff.changed.map((f) => f.path),
+    ['/p/a.pdf']
+  )
+})
+
+test('a document whose file is gone is missing', () => {
+  const diff = diffFolder([], [doc('/p/gone.pdf', 100)])
+  assert.deepEqual(
+    diff.missing.map((d) => d.sourceUri),
+    ['/p/gone.pdf']
+  )
+  assert.equal(diff.added.length + diff.changed.length, 0)
+})
+
+test('a missing document whose file is back and unchanged is restored', () => {
+  const diff = diffFolder([file('/p/a.pdf', 100)], [doc('/p/a.pdf', 100, 'missing')])
+  assert.deepEqual(
+    diff.restored.map((d) => d.sourceUri),
+    ['/p/a.pdf']
+  )
+  assert.equal(diff.changed.length, 0)
+})
+
+test('a missing document whose file is back but changed is re-indexed', () => {
+  const diff = diffFolder([file('/p/a.pdf', 300)], [doc('/p/a.pdf', 100, 'missing')])
+  assert.deepEqual(
+    diff.changed.map((f) => f.path),
+    ['/p/a.pdf']
+  )
+  assert.equal(diff.restored.length, 0)
+})
+
+test('added, changed and missing are computed together', () => {
+  const diff = diffFolder(
+    [file('/p/new.pdf', 10), file('/p/edited.pdf', 20), file('/p/same.pdf', 30)],
+    [doc('/p/edited.pdf', 5), doc('/p/same.pdf', 30), doc('/p/deleted.pdf', 40)]
+  )
+
+  assert.deepEqual(
+    diff.added.map((f) => f.path),
+    ['/p/new.pdf']
+  )
+  assert.deepEqual(
+    diff.changed.map((f) => f.path),
+    ['/p/edited.pdf']
+  )
+  assert.deepEqual(
+    diff.missing.map((d) => d.sourceUri),
+    ['/p/deleted.pdf']
+  )
+})