diff --git a/routes/personal_routes.py b/routes/personal_routes.py
index a42615be7..3cf6c1d9d 100644
--- a/routes/personal_routes.py
+++ b/routes/personal_routes.py
@@ -1,11 +1,13 @@
 # routes/personal_routes.py
 """Routes for personal documents management."""
+import asyncio
 import os
 import logging
 import shutil
 import uuid
 from typing import Any, Dict, List, Tuple
 from fastapi import APIRouter, HTTPException, Query, Request, UploadFile, File, Depends
+from fastapi.concurrency import run_in_threadpool
 from src.request_models import DirectoryRequest
 from core.constants import BASE_DIR, PERSONAL_DIR, PERSONAL_UPLOADS_DIR
 from src.rag_singleton import get_rag_manager
@@ -18,7 +20,6 @@ UPLOADS_DIR = PERSONAL_UPLOADS_DIR
 
 logger = logging.getLogger(__name__)
 
-
 def _personal_upload_dir_for_owner(owner: str | None, *, create: bool = True) -> str:
     """Return the per-owner upload directory used for direct RAG uploads."""
     owner_segment = secure_filename((owner or "local").strip())[:80] or "local"
@@ -141,6 +142,22 @@ def setup_personal_routes(personal_docs_manager, rag_manager, rag_available):
     """
     router = APIRouter(prefix="/api/personal")
 
+    # Serializes directory index jobs across requests. Indexing runs in the
+    # threadpool (#5558), so concurrent requests would otherwise run in parallel
+    # and race PersonalDocsManager's unsynchronized list mutations and file
+    # writes; before the threadpool move they serialized on the blocked event
+    # loop, so one-at-a-time is behavior parity.
+    #
+    # An asyncio.Lock acquired in the async handler BEFORE offloading: a waiting
+    # request parks on the event loop instead of pinning a threadpool worker (an
+    # earlier threading.Lock taken INSIDE the worker meant queued jobs held pool
+    # tokens while blocked, starving every other run_in_threadpool caller).
+    # add/remove/reload all take this lock, so their mutations never interleave.
+    # Per-router (not module-global) so each app binds it to its own event loop.
+    # Scope is the single process: multi-worker deployments would need a shared
+    # lock (out of scope for #5558).
+    _index_job_lock = asyncio.Lock()
+
     def _rag():
         """Get the current RAG manager, retrying init if needed."""
         return get_rag_manager()
@@ -172,8 +189,12 @@ def setup_personal_routes(personal_docs_manager, rag_manager, rag_available):
         return {"files": files, "directories": directories}
     
     @router.post("/reload")
-    def api_personal_reload(owner: str = Depends(require_user), _admin: None = Depends(require_admin)):
-        personal_docs_manager.refresh_index()
+    async def api_personal_reload(owner: str = Depends(require_user), _admin: None = Depends(require_admin)):
+        # refresh_index() re-extracts text across every tracked directory —
+        # blocking work. Take the shared job lock (so it cannot race an add /
+        # remove) and run it off the event loop.
+        async with _index_job_lock:
+            await run_in_threadpool(personal_docs_manager.refresh_index)
         return {"ok": True, "count": len(personal_docs_manager.index)}
     
     @router.post("/add_directory")
@@ -207,12 +228,26 @@ def setup_personal_routes(personal_docs_manager, rag_manager, rag_available):
             # Use the RAGManager to index the directory
             rag = _rag()
             if rag:
-                result = rag.index_personal_documents(directory, owner=owner)
-                
+                def _index_directory():
+                    result = rag.index_personal_documents(directory, owner=owner)
+                    if result["success"]:
+                        # Also update the personal_docs_manager to track this
+                        # directory. Kept inside the offloaded call: it triggers
+                        # refresh_index(), which re-extracts text across tracked
+                        # directories.
+                        personal_docs_manager.add_directory(directory, index=False)
+                    return result
+
+                # Indexing walks, embeds, and stores the whole tree — minutes
+                # on a real directory. The handler is async, so calling it
+                # inline runs it on the event loop and every other request
+                # queues behind it until it finishes (#5558). Serialize on the
+                # async job lock BEFORE offloading so a queued request parks on
+                # the loop instead of pinning a threadpool worker.
+                async with _index_job_lock:
+                    result = await run_in_threadpool(_index_directory)
+
                 if result["success"]:
-                    # Also update the personal_docs_manager to track this directory
-                    personal_docs_manager.add_directory(directory, index=False)
-                    
                     return {
                         "success": True,
                         "message": f"Successfully indexed {result['indexed_count']} chunks from {directory}",
@@ -251,17 +286,25 @@ def setup_personal_routes(personal_docs_manager, rag_manager, rag_available):
 
             logger.info(f"Removing directory from RAG: {directory}")
 
-            # Always remove from personal_docs_manager tracking
-            if hasattr(personal_docs_manager, 'remove_directory'):
-                personal_docs_manager.remove_directory(directory)
-
-            # Remove from RAG vector store (best-effort)
             rag = _rag()
-            if rag:
-                try:
-                    rag.remove_directory(directory)
-                except Exception as e:
-                    logger.warning(f"RAG removal failed for directory {directory}: {e}")
+
+            def _remove_directory():
+                # Always remove from personal_docs_manager tracking. This
+                # mutates the same unsynchronized list/index an add job touches
+                # and re-extracts text (refresh_index), so it is blocking work.
+                if hasattr(personal_docs_manager, 'remove_directory'):
+                    personal_docs_manager.remove_directory(directory)
+                # Remove from RAG vector store (best-effort).
+                if rag:
+                    try:
+                        rag.remove_directory(directory)
+                    except Exception as e:
+                        logger.warning(f"RAG removal failed for directory {directory}: {e}")
+
+            # Same job lock as add/reload so remove cannot interleave with an
+            # in-flight add; offloaded off the event loop.
+            async with _index_job_lock:
+                await run_in_threadpool(_remove_directory)
 
             return {
                 "success": True,
@@ -289,54 +332,73 @@ def setup_personal_routes(personal_docs_manager, rag_manager, rag_available):
         total_failed = 0
         uploaded_files = []
 
-        for upload in files:
-            try:
-                file_path, stored_name, safe_name = _unique_personal_upload_path(upload_dir, upload.filename)
-                content_bytes = await upload.read(PERSONAL_UPLOAD_MAX_BYTES + 1)
-                if len(content_bytes) > PERSONAL_UPLOAD_MAX_BYTES:
-                    logger.warning(f"Rejected oversized personal upload: {upload.filename!r}")
-                    total_failed += 1
-                    continue
-                with open(file_path, "wb") as f:
-                    f.write(content_bytes)
-
-                ext = os.path.splitext(safe_name)[1].lower()
-                if ext == ".pdf":
-                    from src.personal_docs import extract_pdf_text
-                    text = extract_pdf_text(file_path)
-                else:
-                    text = content_bytes.decode("utf-8", errors="replace")
-
-                if not text or not text.strip():
-                    total_failed += 1
-                    continue
-
-                # Chunk and index
-                chunks = rag._split_into_chunks(text, chunk_size=500)
-                for i, chunk in enumerate(chunks):
-                    metadata = {
-                        "source": file_path,
-                        "filename": safe_name,
-                        "stored_filename": stored_name,
-                        "directory": upload_dir,
-                        "type": ext,
-                        "chunk_id": i,
-                    }
-                    if user:
-                        metadata["owner"] = user
-                    if rag.add_document(chunk, metadata):
-                        total_indexed += 1
-                    else:
+        # Chunking, embedding and the tracking update are blocking work over the
+        # same vector/tracking state add_directory mutates (#5634). Take the
+        # shared job lock BEFORE offloading so a queued request parks on the loop
+        # instead of pinning a threadpool worker, matching add_directory.
+        # Read and process one capped payload at a time so a multi-file request
+        # cannot retain len(files) * PERSONAL_UPLOAD_MAX_BYTES in memory.
+        async with _index_job_lock:
+            for upload in files:
+                try:
+                    file_path, stored_name, safe_name = _unique_personal_upload_path(
+                        upload_dir, upload.filename
+                    )
+                    content_bytes = await upload.read(PERSONAL_UPLOAD_MAX_BYTES + 1)
+                    if len(content_bytes) > PERSONAL_UPLOAD_MAX_BYTES:
+                        logger.warning(f"Rejected oversized personal upload: {upload.filename!r}")
                         total_failed += 1
+                        continue
 
-                uploaded_files.append(safe_name)
-            except Exception as e:
-                logger.error(f"Failed to upload/index {upload.filename}: {e}")
-                total_failed += 1
+                    def _index_upload():
+                        with open(file_path, "wb") as f:
+                            f.write(content_bytes)
 
-        # Track uploads directory
-        if uploaded_files and hasattr(personal_docs_manager, "add_directory"):
-            personal_docs_manager.add_directory(upload_dir, index=False)
+                        ext = os.path.splitext(safe_name)[1].lower()
+                        if ext == ".pdf":
+                            from src.personal_docs import extract_pdf_text
+                            text = extract_pdf_text(file_path)
+                        else:
+                            text = content_bytes.decode("utf-8", errors="replace")
+
+                        if not text or not text.strip():
+                            return 0, 1, None
+
+                        indexed = 0
+                        failed = 0
+                        chunks = rag._split_into_chunks(text, chunk_size=500)
+                        for i, chunk in enumerate(chunks):
+                            metadata = {
+                                "source": file_path,
+                                "filename": safe_name,
+                                "stored_filename": stored_name,
+                                "directory": upload_dir,
+                                "type": ext,
+                                "chunk_id": i,
+                            }
+                            if user:
+                                metadata["owner"] = user
+                            if rag.add_document(chunk, metadata):
+                                indexed += 1
+                            else:
+                                failed += 1
+                        return indexed, failed, safe_name
+
+                    indexed, failed, uploaded_name = await run_in_threadpool(_index_upload)
+                    total_indexed += indexed
+                    total_failed += failed
+                    if uploaded_name:
+                        uploaded_files.append(uploaded_name)
+                except Exception as e:
+                    logger.error(f"Failed to upload/index {upload.filename}: {e}")
+                    total_failed += 1
+
+            # Same transition, same lock: the tracking update must not land
+            # while another job is mid-write over the same state.
+            if uploaded_files and hasattr(personal_docs_manager, "add_directory"):
+                await run_in_threadpool(
+                    personal_docs_manager.add_directory, upload_dir, index=False
+                )
 
         return {
             "success": True,
@@ -349,38 +411,47 @@ def setup_personal_routes(personal_docs_manager, rag_manager, rag_available):
     async def delete_file_from_rag(filepath: str = Query(...), owner: str = Depends(require_user), _admin: None = Depends(require_admin)):
         """Delete a specific file from RAG index and optionally from disk."""
         try:
-            # Remove chunks from RAG vector store (best-effort)
-            removed = 0
-            rag = _rag()
-            if rag:
-                try:
-                    removed = rag.delete_by_source(filepath)
-                except Exception as e:
-                    logger.warning(f"RAG removal failed for {filepath}: {e}")
+            def _delete_file():
+                # Remove chunks from RAG vector store (best-effort)
+                removed = 0
+                rag = _rag()
+                if rag:
+                    try:
+                        removed = rag.delete_by_source(filepath)
+                    except Exception as e:
+                        logger.warning(f"RAG removal failed for {filepath}: {e}")
 
-            # Delete file from disk if it's in the caller's own uploads dir.
-            # Scope to the per-owner subdir, not the shared uploads root, so one
-            # admin can't delete another user's personal files by path.
-            deleted_from_disk = False
-            try:
-                abs_target = os.path.realpath(filepath)
-                base_abs = os.path.realpath(_personal_upload_dir_for_owner(owner, create=False))
-                in_uploads = (
-                    abs_target == base_abs
-                    or os.path.commonpath([abs_target, base_abs]) == base_abs
-                )
-            except ValueError:
-                # commonpath raises on mixed drives / non-comparable paths
-                in_uploads = False
-            if in_uploads and abs_target != base_abs:
+                # Delete file from disk if it's in the caller's own uploads dir.
+                # Scope to the per-owner subdir, not the shared uploads root, so one
+                # admin can't delete another user's personal files by path.
+                deleted_from_disk = False
                 try:
-                    os.remove(abs_target)
-                    deleted_from_disk = True
-                except FileNotFoundError:
-                    pass  # already gone — race with another request or cleanup
+                    abs_target = os.path.realpath(filepath)
+                    base_abs = os.path.realpath(_personal_upload_dir_for_owner(owner, create=False))
+                    in_uploads = (
+                        abs_target == base_abs
+                        or os.path.commonpath([abs_target, base_abs]) == base_abs
+                    )
+                except ValueError:
+                    # commonpath raises on mixed drives / non-comparable paths
+                    in_uploads = False
+                if in_uploads and abs_target != base_abs:
+                    try:
+                        os.remove(abs_target)
+                        deleted_from_disk = True
+                    except FileNotFoundError:
+                        pass  # already gone — race with another request or cleanup
 
-            # Exclude the file from the listing (persists across restarts)
-            personal_docs_manager.exclude_file(filepath)
+                # Exclude the file from the listing (persists across restarts)
+                personal_docs_manager.exclude_file(filepath)
+                return removed, deleted_from_disk
+
+            # Vector removal, the disk unlink and the exclusion write are one
+            # transition over the same state add_directory mutates (#5634), and
+            # all three block. Take the shared job lock BEFORE offloading, as
+            # add_directory does.
+            async with _index_job_lock:
+                removed, deleted_from_disk = await run_in_threadpool(_delete_file)
 
             return {
                 "success": True,
diff --git a/tests/test_add_directory_event_loop.py b/tests/test_add_directory_event_loop.py
new file mode 100644
index 000000000..dd70aa134
--- /dev/null
+++ b/tests/test_add_directory_event_loop.py
@@ -0,0 +1,394 @@
+"""Regression guard for #5558 — POST /api/personal/add_directory must not run
+the indexing job on the event loop.
+
+The handler is ``async def`` but called ``rag.index_personal_documents``
+(os.walk + file reads + per-chunk embedding + Chroma inserts) inline, so
+FastAPI ran the whole job on the event loop and every other request queued
+behind it: indexing a real directory froze the UI and API for 25+ minutes.
+``personal_docs_manager.add_directory`` sits in the same blocking section — it
+triggers ``refresh_index()``, which re-extracts text across tracked dirs.
+
+These tests build the real router with fake managers and compare the thread
+the indexing work runs on against the event loop's thread.
+"""
+import asyncio
+import os
+import threading
+
+os.environ.setdefault("DATABASE_URL", "sqlite:///:memory:")
+
+import httpx
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+
+
+def _serialization_probe():
+    """Shared counter proving two critical sections never overlap."""
+    state = {"active": 0, "max_active": 0}
+    lock = threading.Lock()
+
+    def enter():
+        with lock:
+            state["active"] += 1
+            state["max_active"] = max(state["max_active"], state["active"])
+
+    def leave():
+        with lock:
+            state["active"] -= 1
+
+    return state, enter, leave
+
+
+# Concurrency tests are `async def` (pyproject asyncio_mode="auto") and drive the
+# ASGI app through httpx.ASGITransport + AsyncClient + asyncio.gather, NOT starlette
+# TestClient + ThreadPoolExecutor: the job lock is an asyncio.Lock acquired in the
+# async handler, and TestClient's portal-thread dispatch deadlocks against it (same
+# reason test_notes_fail_closed_auth.py uses ASGITransport). asyncio.gather runs both
+# requests on the test's own loop.
+def _async_client(app):
+    return httpx.AsyncClient(transport=httpx.ASGITransport(app=app), base_url="http://t")
+
+import routes.personal_routes as personal_routes
+from core.middleware import require_admin
+from src.auth_helpers import require_user
+
+
+class _FakeRag:
+    def __init__(self, record):
+        self._record = record
+
+    def index_personal_documents(self, directory, owner=None):
+        self._record["index_thread"] = threading.get_ident()
+        return {"success": True, "indexed_count": 3, "failed_count": 0}
+
+    def _split_into_chunks(self, text, chunk_size=500):
+        return [text]
+
+    def add_document(self, chunk, metadata):
+        self._record["add_document_thread"] = threading.get_ident()
+        return True
+
+    def delete_by_source(self, filepath):
+        self._record["delete_thread"] = threading.get_ident()
+        return 1
+
+
+class _FakeDocsManager:
+    def __init__(self, record):
+        self._record = record
+        self.index = []
+
+    def add_directory(self, directory, *, index=True, owner=None):
+        self._record["bookkeeping_thread"] = threading.get_ident()
+        self._record["bookkeeping_index_flag"] = index
+
+    def exclude_file(self, filepath):
+        self._record["exclude_thread"] = threading.get_ident()
+
+
+def _build_app(tmp_path, monkeypatch, record):
+    monkeypatch.setattr(personal_routes, "PERSONAL_DIR", str(tmp_path))
+    monkeypatch.setattr(personal_routes, "get_rag_manager", lambda: _FakeRag(record))
+
+    app = FastAPI()
+    app.include_router(
+        personal_routes.setup_personal_routes(_FakeDocsManager(record), None, True)
+    )
+    app.dependency_overrides[require_user] = lambda: "tester"
+    app.dependency_overrides[require_admin] = lambda: None
+
+    @app.get("/loop-thread")
+    async def loop_thread_probe():
+        return {"thread": threading.get_ident()}
+
+    return app
+
+
+def test_indexing_runs_off_the_event_loop(tmp_path, monkeypatch):
+    record = {}
+    app = _build_app(tmp_path, monkeypatch, record)
+    target = tmp_path / "docs"
+    target.mkdir()
+
+    # Context-manager client: one portal/event loop serves both requests, so
+    # the probe and the POST are guaranteed to see the same loop thread.
+    with TestClient(app) as client:
+        loop_thread = client.get("/loop-thread").json()["thread"]
+        resp = client.post(
+            "/api/personal/add_directory", json={"directory": str(target)}
+        )
+
+    assert resp.status_code == 200
+    assert record["index_thread"] != loop_thread, (
+        "index_personal_documents ran on the event loop thread — every other "
+        "request queues behind the indexing job (#5558)"
+    )
+    assert record["bookkeeping_thread"] != loop_thread, (
+        "personal_docs_manager.add_directory (refresh_index) ran on the event "
+        "loop thread"
+    )
+
+
+def test_response_and_bookkeeping_unchanged(tmp_path, monkeypatch):
+    record = {}
+    app = _build_app(tmp_path, monkeypatch, record)
+    target = tmp_path / "docs"
+    target.mkdir()
+
+    client = TestClient(app)
+    resp = client.post("/api/personal/add_directory", json={"directory": str(target)})
+
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["success"] is True
+    assert body["indexed_count"] == 3
+    assert body["failed_count"] == 0
+    assert body["directory"] == os.path.realpath(str(target))
+    assert record["bookkeeping_index_flag"] is False
+
+
+async def test_concurrent_add_directory_requests_serialize_indexing(tmp_path, monkeypatch):
+    """Off-loop execution must not mean parallel index jobs: concurrent
+    requests would race PersonalDocsManager's unsynchronized list mutations
+    and file writes (save_directories/_save_excluded are plain open('w'))."""
+    import time
+
+    state, enter, leave = _serialization_probe()
+
+    def _slow_index(self, directory, owner=None):
+        enter(); time.sleep(0.2); leave()
+        return {"success": True, "indexed_count": 1, "failed_count": 0}
+
+    monkeypatch.setattr(_FakeRag, "index_personal_documents", _slow_index)
+
+    record = {}
+    app = _build_app(tmp_path, monkeypatch, record)
+    for name in ("docs_a", "docs_b"):
+        (tmp_path / name).mkdir()
+
+    async with _async_client(app) as ac:
+        results = await asyncio.gather(
+            ac.post("/api/personal/add_directory", json={"directory": str(tmp_path / "docs_a")}),
+            ac.post("/api/personal/add_directory", json={"directory": str(tmp_path / "docs_b")}),
+        )
+
+    assert all(r.status_code == 200 for r in results)
+    assert state["max_active"] == 1, (
+        f"{state['max_active']} index jobs ran in parallel — concurrent "
+        "add_directory requests must serialize"
+    )
+
+
+def test_failed_indexing_still_returns_500(tmp_path, monkeypatch):
+    record = {}
+    app = _build_app(tmp_path, monkeypatch, record)
+    target = tmp_path / "docs"
+    target.mkdir()
+
+    def _fail(directory, owner=None):
+        return {"success": False, "message": "boom"}
+
+    monkeypatch.setattr(_FakeRag, "index_personal_documents", staticmethod(_fail))
+
+    client = TestClient(app)
+    resp = client.post("/api/personal/add_directory", json={"directory": str(target)})
+    assert resp.status_code == 500
+    assert "boom" in resp.json()["detail"]
+
+
+async def test_add_and_remove_serialize(tmp_path, monkeypatch):
+    """#5634: remove must hold the SAME job lock as add. Otherwise a remove
+    running while an add job is in flight races PersonalDocsManager's
+    unsynchronized list/index mutations — the inconsistent state the PR's
+    'add/remove are serialized' guarantee claims to prevent."""
+    import time
+
+    state, enter, leave = _serialization_probe()
+
+    def _slow_index(self, directory, owner=None):
+        enter(); time.sleep(0.25); leave()
+        return {"success": True, "indexed_count": 1, "failed_count": 0}
+
+    def _slow_remove(self, directory):
+        enter(); time.sleep(0.25); leave()
+
+    monkeypatch.setattr(_FakeRag, "index_personal_documents", _slow_index)
+    monkeypatch.setattr(_FakeDocsManager, "remove_directory", _slow_remove, raising=False)
+
+    record = {}
+    app = _build_app(tmp_path, monkeypatch, record)
+    (tmp_path / "docs_a").mkdir()
+    (tmp_path / "docs_b").mkdir()
+
+    async with _async_client(app) as ac:
+        results = await asyncio.gather(
+            ac.post("/api/personal/add_directory", json={"directory": str(tmp_path / "docs_a")}),
+            ac.delete("/api/personal/remove_directory", params={"directory": str(tmp_path / "docs_b")}),
+        )
+
+    assert all(r.status_code == 200 for r in results)
+    assert state["max_active"] == 1, (
+        f"{state['max_active']} add/remove critical sections overlapped — "
+        "remove must hold the same index job lock as add"
+    )
+
+
+async def test_add_and_upload_serialize(tmp_path, monkeypatch):
+    """#5634 follow-up: POST /upload writes chunks into the vector store and then
+    calls personal_docs_manager.add_directory — the same vector/tracking state
+    add_directory mutates. It must hold the SAME job lock, or an upload landing
+    mid-add interleaves two writers over unsynchronized state."""
+    import time
+
+    state, enter, leave = _serialization_probe()
+
+    def _slow_index(self, directory, owner=None):
+        enter(); time.sleep(0.25); leave()
+        return {"success": True, "indexed_count": 1, "failed_count": 0}
+
+    def _slow_add_document(self, chunk, metadata):
+        self._record["add_document_thread"] = threading.get_ident()
+        enter(); time.sleep(0.25); leave()
+        return True
+
+    monkeypatch.setattr(_FakeRag, "index_personal_documents", _slow_index)
+    monkeypatch.setattr(_FakeRag, "add_document", _slow_add_document)
+
+    record = {}
+    app = _build_app(tmp_path, monkeypatch, record)
+    monkeypatch.setattr(personal_routes, "UPLOADS_DIR", str(tmp_path / "uploads"))
+    monkeypatch.setattr(personal_routes, "require_privilege", lambda request, key: "tester")
+    (tmp_path / "docs_a").mkdir()
+
+    async with _async_client(app) as ac:
+        results = await asyncio.gather(
+            ac.post("/api/personal/add_directory", json={"directory": str(tmp_path / "docs_a")}),
+            ac.post("/api/personal/upload", files={"files": ("a.txt", b"hello world", "text/plain")}),
+        )
+
+    assert all(r.status_code == 200 for r in results)
+    # The test coroutine runs on the event loop, so this IS the loop thread.
+    assert record["add_document_thread"] != threading.get_ident(), (
+        "rag.add_document ran on the event loop thread — chunk writes block "
+        "every other request for the duration of the upload"
+    )
+    assert state["max_active"] == 1, (
+        f"{state['max_active']} add/upload critical sections overlapped — "
+        "upload must hold the same index job lock as add"
+    )
+
+
+async def test_upload_processes_each_payload_before_reading_the_next(tmp_path, monkeypatch):
+    """A multi-file upload must retain at most one capped payload at a time."""
+    from starlette.datastructures import UploadFile as StarletteUploadFile
+
+    reads = []
+    original_read = StarletteUploadFile.read
+
+    async def _recording_read(upload, size=-1):
+        reads.append(upload.filename)
+        return await original_read(upload, size)
+
+    def _record_first_index(self, chunk, metadata):
+        self._record.setdefault("reads_at_first_index", len(reads))
+        return True
+
+    monkeypatch.setattr(StarletteUploadFile, "read", _recording_read)
+    monkeypatch.setattr(_FakeRag, "add_document", _record_first_index)
+
+    record = {}
+    app = _build_app(tmp_path, monkeypatch, record)
+    monkeypatch.setattr(personal_routes, "UPLOADS_DIR", str(tmp_path / "uploads"))
+    monkeypatch.setattr(personal_routes, "require_privilege", lambda request, key: "tester")
+
+    files = [
+        ("files", ("a.txt", b"alpha", "text/plain")),
+        ("files", ("b.txt", b"bravo", "text/plain")),
+        ("files", ("c.txt", b"charlie", "text/plain")),
+    ]
+    async with _async_client(app) as ac:
+        response = await ac.post("/api/personal/upload", files=files)
+
+    assert response.status_code == 200
+    assert response.json()["uploaded"] == ["a.txt", "b.txt", "c.txt"]
+    assert reads == ["a.txt", "b.txt", "c.txt"]
+    assert record["reads_at_first_index"] == 1, (
+        "all upload bodies were retained before worker processing began"
+    )
+
+
+async def test_add_and_delete_file_serialize(tmp_path, monkeypatch):
+    """#5634 follow-up: DELETE /file removes chunks from the vector store and
+    calls personal_docs_manager.exclude_file. Both mutate state add_directory
+    also touches, so the delete must hold the SAME job lock as add."""
+    import time
+
+    state, enter, leave = _serialization_probe()
+
+    def _slow_index(self, directory, owner=None):
+        enter(); time.sleep(0.25); leave()
+        return {"success": True, "indexed_count": 1, "failed_count": 0}
+
+    def _slow_delete(self, filepath):
+        self._record["delete_thread"] = threading.get_ident()
+        enter(); time.sleep(0.25); leave()
+        return 1
+
+    monkeypatch.setattr(_FakeRag, "index_personal_documents", _slow_index)
+    monkeypatch.setattr(_FakeRag, "delete_by_source", _slow_delete)
+
+    record = {}
+    app = _build_app(tmp_path, monkeypatch, record)
+    monkeypatch.setattr(personal_routes, "UPLOADS_DIR", str(tmp_path / "uploads"))
+    (tmp_path / "docs_a").mkdir()
+    doomed = tmp_path / "doomed.txt"
+    doomed.write_text("bye")
+
+    async with _async_client(app) as ac:
+        results = await asyncio.gather(
+            ac.post("/api/personal/add_directory", json={"directory": str(tmp_path / "docs_a")}),
+            ac.delete("/api/personal/file", params={"filepath": str(doomed)}),
+        )
+
+    assert all(r.status_code == 200 for r in results)
+    assert record["delete_thread"] != threading.get_ident(), (
+        "rag.delete_by_source ran on the event loop thread"
+    )
+    assert state["max_active"] == 1, (
+        f"{state['max_active']} add/delete critical sections overlapped — "
+        "delete must hold the same index job lock as add"
+    )
+
+
+async def test_reload_serializes_with_add(tmp_path, monkeypatch):
+    """#5634: POST /reload rebuilds the index via refresh_index(); it must hold
+    the same job lock so it cannot race an in-flight add job."""
+    import time
+
+    state, enter, leave = _serialization_probe()
+
+    def _slow_index(self, directory, owner=None):
+        enter(); time.sleep(0.25); leave()
+        return {"success": True, "indexed_count": 1, "failed_count": 0}
+
+    def _slow_refresh(self):
+        enter(); time.sleep(0.25); leave()
+
+    monkeypatch.setattr(_FakeRag, "index_personal_documents", _slow_index)
+    monkeypatch.setattr(_FakeDocsManager, "refresh_index", _slow_refresh, raising=False)
+
+    record = {}
+    app = _build_app(tmp_path, monkeypatch, record)
+    (tmp_path / "docs_a").mkdir()
+
+    async with _async_client(app) as ac:
+        results = await asyncio.gather(
+            ac.post("/api/personal/add_directory", json={"directory": str(tmp_path / "docs_a")}),
+            ac.post("/api/personal/reload"),
+        )
+
+    assert all(r.status_code == 200 for r in results)
+    assert state["max_active"] == 1, (
+        f"{state['max_active']} add/reload critical sections overlapped — "
+        "reload must hold the same index job lock as add"
+    )