diff --git a/core/queue.py b/core/queue.py
index cc06468..c6925f4 100644
--- a/core/queue.py
+++ b/core/queue.py
@@ -1,4 +1,5 @@
 import logging
+import threading
 from pydantic import BaseModel
 from typing import Any, Optional
 from gitea.models import IssueModel, PullRequestModel
@@ -19,43 +20,53 @@ class WorkQueue:
     """Thread-safe work queue grouped by repo."""
 
     def __init__(self) -> None:
+        self._lock: threading.Lock = threading.Lock()
         self._queue: list[WorkItem] = []
         self._enqueued_repos: set[str] = set()
 
     def enqueue(self, item: WorkItem) -> None:
-        self._queue.append(item)
-        self._enqueued_repos.add(item.repo_full_name)
-        logger.info(f"Enqueued work item: {item.task_type} #{item.task_number} for {item.repo_full_name}")
+        with self._lock:
+            self._queue.append(item)
+            self._enqueued_repos.add(item.repo_full_name)
+            logger.info(f"Enqueued work item: {item.task_type} #{item.task_number} for {item.repo_full_name}")
 
     def enqueue_batch(self, items: list[WorkItem]) -> None:
-        for item in items:
-            self.enqueue(item)
+        with self._lock:
+            for item in items:
+                self._queue.append(item)
+                self._enqueued_repos.add(item.repo_full_name)
+                logger.info(f"Enqueued work item: {item.task_type} #{item.task_number} for {item.repo_full_name}")
 
     def get_repo_work(self, repo: str) -> list[WorkItem]:
         """Get all work items for a specific repo."""
-        items: list[WorkItem] = [
-            item for item in self._queue if item.repo_full_name == repo
-        ]
-        logger.info(f"Retrieved {len(items)} work items for repository: {repo}")
-        return items
+        with self._lock:
+            items: list[WorkItem] = [
+                item for item in self._queue if item.repo_full_name == repo
+            ]
+            logger.info(f"Retrieved {len(items)} work items for repository: {repo}")
+            return items
 
     def remove_repo_work(self, repo: str) -> None:
         """Remove all work items for a specific repo."""
-        self._queue = [
-            item for item in self._queue if item.repo_full_name != repo
-        ]
-        self._enqueued_repos.discard(repo)
-        logger.info(f"Removed all work items for repository: {repo}")
+        with self._lock:
+            self._queue = [
+                item for item in self._queue if item.repo_full_name != repo
+            ]
+            self._enqueued_repos.discard(repo)
+            logger.info(f"Removed all work items for repository: {repo}")
 
     def get_next_repo(self) -> str | None:
         """Get the next repo with work, or None if empty."""
-        if not self._enqueued_repos:
-            return None
-        return next(iter(self._enqueued_repos))
+        with self._lock:
+            if not self._enqueued_repos:
+                return None
+            return next(iter(self._enqueued_repos))
 
     @property
     def is_empty(self) -> bool:
-        return len(self._queue) == 0
+        with self._lock:
+            return len(self._queue) == 0
 
     def __len__(self) -> int:
-        return len(self._queue)
+        with self._lock:
+            return len(self._queue)
diff --git a/tests/test_queue.py b/tests/test_queue.py
new file mode 100644
index 0000000..97e8b48
--- /dev/null
+++ b/tests/test_queue.py
@@ -0,0 +1,102 @@
+import threading
+from core.queue import WorkQueue, WorkItem
+from gitea.models import IssueModel
+
+
+def test_work_queue_basic_operations() -> None:
+    queue: WorkQueue = WorkQueue()
+    assert queue.is_empty
+    assert len(queue) == 0
+    assert queue.get_next_repo() is None
+
+    item1 = WorkItem(
+        repo_full_name="meeks/repo1",
+        task_type="issue",
+        task_number=1,
+        task_info=IssueModel(number=1),
+    )
+    item2 = WorkItem(
+        repo_full_name="meeks/repo1",
+        task_type="issue",
+        task_number=2,
+        task_info=IssueModel(number=2),
+    )
+    item3 = WorkItem(
+        repo_full_name="meeks/repo2",
+        task_type="issue",
+        task_number=3,
+        task_info=IssueModel(number=3),
+    )
+
+    queue.enqueue(item1)
+    assert not queue.is_empty
+    assert len(queue) == 1
+    assert queue.get_next_repo() == "meeks/repo1"
+
+    queue.enqueue_batch([item2, item3])
+    assert len(queue) == 3
+
+    # get_repo_work
+    repo1_work = queue.get_repo_work("meeks/repo1")
+    assert len(repo1_work) == 2
+    assert repo1_work[0].task_number == 1
+    assert repo1_work[1].task_number == 2
+
+    # remove_repo_work
+    queue.remove_repo_work("meeks/repo1")
+    assert len(queue) == 1
+    assert queue.get_next_repo() == "meeks/repo2"
+
+    queue.remove_repo_work("meeks/repo2")
+    assert queue.is_empty
+    assert len(queue) == 0
+    assert queue.get_next_repo() is None
+
+
+def test_work_queue_thread_safety() -> None:
+    queue: WorkQueue = WorkQueue()
+    num_threads: int = 10
+    items_per_thread: int = 100
+    barrier = threading.Barrier(num_threads)
+
+    def worker(thread_idx: int) -> None:
+        barrier.wait()  # synchronize start
+        for i in range(items_per_thread):
+            item = WorkItem(
+                repo_full_name=f"meeks/repo_{thread_idx}",
+                task_type="issue",
+                task_number=i,
+                task_info=IssueModel(number=i),
+            )
+            queue.enqueue(item)
+
+    threads: list[threading.Thread] = []
+    for idx in range(num_threads):
+        t = threading.Thread(target=worker, args=(idx,))
+        threads.append(t)
+        t.start()
+
+    for t in threads:
+        t.join()
+
+    # Verify that all items are enqueued
+    assert len(queue) == num_threads * items_per_thread
+
+    # Concurrently remove repo work
+    barrier_remove = threading.Barrier(num_threads)
+
+    def remover(thread_idx: int) -> None:
+        barrier_remove.wait()
+        queue.remove_repo_work(f"meeks/repo_{thread_idx}")
+
+    remove_threads: list[threading.Thread] = []
+    for idx in range(num_threads):
+        t = threading.Thread(target=remover, args=(idx,))
+        remove_threads.append(t)
+        t.start()
+
+    for t in remove_threads:
+        t.join()
+
+    assert queue.is_empty
+    assert len(queue) == 0