diff --git a/.github/workflows/faiss.yml b/.github/workflows/faiss.yml
new file mode 100644
index 0000000000..f78bf2b586
--- /dev/null
+++ b/.github/workflows/faiss.yml
@@ -0,0 +1,76 @@
+# This workflow comes from https://github.com/ofek/hatch-mypyc
+# https://github.com/ofek/hatch-mypyc/blob/5a198c0ba8660494d02716cfc9d79ce4adfb1442/.github/workflows/test.yml
+name: Test / faiss
+
+on:
+  schedule:
+    - cron: "0 0 * * *"
+  pull_request:
+    paths:
+      - "integrations/faiss/**"
+      - "!integrations/faiss/*.md"
+      - ".github/workflows/faiss.yml"
+
+concurrency:
+  group: faiss-${{ github.head_ref }}
+  cancel-in-progress: true
+
+env:
+  PYTHONUNBUFFERED: "1"
+  FORCE_COLOR: "1"
+
+defaults:
+  run:
+    working-directory: integrations/faiss
+
+jobs:
+  run:
+    name: Python ${{ matrix.python-version }} on ${{ startsWith(matrix.os, 'macos-') && 'macOS' || startsWith(matrix.os, 'windows-') && 'Windows' || 'Linux' }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        # FAISS wheels are most reliable on Linux in CI.
+        os: [ubuntu-latest] #[ubuntu-latest, windows-latest, macos-latest]
+        python-version: ["3.10", "3.13"]
+
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v6
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Install Hatch
+        run: pip install hatch "virtualenv<21.0.0"
+
+      - name: Lint
+        if: matrix.python-version == '3.10' && runner.os == 'Linux'
+        run: hatch run fmt-check && hatch run test:types
+
+      - name: Run tests
+        run: hatch run test:cov-retry
+
+      - name: Run unit tests with lowest direct dependencies
+        if: matrix.python-version == '3.10' && runner.os == 'Linux'
+        run: |
+          hatch env prune
+          hatch run uv pip compile pyproject.toml --resolution lowest-direct --output-file requirements_lowest_direct.txt
+          hatch -e test env run -- uv pip install -r requirements_lowest_direct.txt
+          hatch run test:unit
+
+      - name: Nightly - run unit tests with Haystack main branch
+        if: github.event_name == 'schedule'
+        run: |
+          hatch env prune
+          hatch -e test env run -- uv pip install git+https://github.com/deepset-ai/haystack.git@main
+          hatch run test:unit
+
+      - name: Send event to Datadog for nightly failures
+        if: failure() && github.event_name == 'schedule'
+        uses: ./.github/actions/send_failure
+        with:
+          title: |
+            Core integrations nightly tests failure: ${{ github.workflow }}
+          api-key: ${{ secrets.CORE_DATADOG_API_KEY }}
diff --git a/integrations/faiss/pyproject.toml b/integrations/faiss/pyproject.toml
index 5646508a95..016f26822f 100644
--- a/integrations/faiss/pyproject.toml
+++ b/integrations/faiss/pyproject.toml
@@ -24,7 +24,7 @@ classifiers = [
 dependencies = [
   "haystack-ai>=2.24.0",
   "faiss-cpu>=1.8.0",
-  "numpy",
+  "numpy>=1.22,<2; python_version < '3.13'",
 ]
 
 [project.urls]
diff --git a/integrations/faiss/src/haystack_integrations/components/retrievers/faiss/embedding_retriever.py b/integrations/faiss/src/haystack_integrations/components/retrievers/faiss/embedding_retriever.py
index fb918cf383..fde48d7bf1 100644
--- a/integrations/faiss/src/haystack_integrations/components/retrievers/faiss/embedding_retriever.py
+++ b/integrations/faiss/src/haystack_integrations/components/retrievers/faiss/embedding_retriever.py
@@ -50,7 +50,7 @@ class FAISSEmbeddingRetriever:
 
     assert res["retriever"]["documents"][0].content == "There are over 7,000 languages spoken around the world today."
     ```
-    """ # noqa: E501
+    """  # noqa: E501
 
     def __init__(
         self,
diff --git a/integrations/faiss/src/haystack_integrations/components/retrievers/faiss/py.typed b/integrations/faiss/src/haystack_integrations/components/retrievers/faiss/py.typed
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/integrations/faiss/src/haystack_integrations/document_stores/faiss/document_store.py b/integrations/faiss/src/haystack_integrations/document_stores/faiss/document_store.py
index fc78f19cd6..050a4929aa 100644
--- a/integrations/faiss/src/haystack_integrations/document_stores/faiss/document_store.py
+++ b/integrations/faiss/src/haystack_integrations/document_stores/faiss/document_store.py
@@ -9,7 +9,7 @@
 from pathlib import Path
 from typing import Any
 
-import faiss
+import faiss  # type: ignore[import-untyped]
 import numpy as np
 from haystack import default_from_dict, default_to_dict
 from haystack.dataclasses import Document
@@ -40,6 +40,8 @@ def __init__(
         :param index_path: Path to save/load the index and documents. If None, the store is in-memory only.
         :param index_string: The FAISS index factory string. Default is "Flat".
         :param embedding_dim: The dimension of the embeddings. Default is 768.
+        :raises DocumentStoreError: If the FAISS index cannot be initialized.
+        :raises ValueError: If `index_path` points to a missing `.faiss` file when loading persisted data.
         """
         self.index_path = index_path
         self.embedding_dim = embedding_dim
@@ -68,6 +70,13 @@ def _create_new_index(self):
             msg = f"Could not create FAISS index with factory string '{self.index_string}': {e}"
             raise DocumentStoreError(msg) from e
 
+    def _get_index_or_raise(self) -> Any:
+        """Return the FAISS index or raise if it is unexpectedly missing."""
+        if self.index is None:
+            msg = "FAISS index has not been initialized."
+            raise DocumentStoreError(msg)
+        return self.index
+
     def count_documents(self) -> int:
         """
         Returns the number of documents in the store.
@@ -80,6 +89,7 @@ def filter_documents(self, filters: dict[str, Any] | None = None) -> list[Docume
 
         :param filters: A dictionary of filters to apply.
         :return: A list of matching Documents.
+        :raises FilterError: If the filter structure is invalid.
         """
         if not filters:
             return list(self.documents.values())
@@ -120,6 +130,9 @@ def write_documents(self, documents: list[Document], policy: DuplicatePolicy = D
         :param documents: The list of documents to write.
         :param policy: The policy to handle duplicate documents.
         :return: The number of documents written.
+        :raises ValueError: If `documents` is not an iterable of `Document` objects.
+        :raises DuplicateDocumentError: If a duplicate document is found and `policy` is `DuplicatePolicy.FAIL`.
+        :raises DocumentStoreError: If the FAISS index is unexpectedly unavailable when adding embeddings.
         """
         if not isinstance(documents, Iterable) or isinstance(documents, (str, bytes)):
             msg = "param 'documents' must contain an iterable of objects of type Document."
@@ -175,13 +188,16 @@ def write_documents(self, documents: list[Document], policy: DuplicatePolicy = D
         if vectors_to_add:
             vectors = np.array(vectors_to_add, dtype="float32")
             ids = np.array(ids_to_add_to_index, dtype="int64")
-            self.index.add_with_ids(vectors, ids)
+            index = self._get_index_or_raise()
+            index.add_with_ids(vectors, ids)
 
         return docs_written
 
     def delete_documents(self, document_ids: list[str]) -> None:
         """
         Deletes documents from the store.
+
+        :raises DocumentStoreError: If the FAISS index is unexpectedly unavailable when removing embeddings.
         """
         if not document_ids:
             return
@@ -197,9 +213,10 @@ def delete_documents(self, document_ids: list[str]) -> None:
                     del self.id_map[int_id]
                     ids_to_remove_from_index.append(int_id)
 
-        if ids_to_remove_from_index and self.index.ntotal > 0:
+        index = self._get_index_or_raise()
+        if ids_to_remove_from_index and index.ntotal > 0:
             ids_array = np.array(ids_to_remove_from_index, dtype="int64")
-            self.index.remove_ids(ids_array)
+            index.remove_ids(ids_array)
 
     def delete_all_documents(self) -> None:
         """
@@ -221,6 +238,7 @@ def search(
         :param top_k: The number of results to return.
         :param filters: Filters to apply.
         :return: A list of matching Documents.
+        :raises FilterError: If the filter structure is invalid.
         """
         if not self.index or self.index.ntotal == 0:
             return []
@@ -301,6 +319,9 @@ def _check_condition(self, doc: Document, condition: dict[str, Any]) -> bool:
             msg = "Missing 'field' in filter condition"
             raise FilterError(msg)
         field = condition.get("field")
+        if not isinstance(field, str):
+            msg = "'field' in filter condition must be a string"
+            raise FilterError(msg)
         if "value" not in condition:
             msg = "Missing 'value' in filter condition"
             raise FilterError(msg)
@@ -370,6 +391,8 @@ def delete_by_filter(self, filters: dict[str, Any]) -> int:
 
         :param filters: A dictionary of filters to apply to find documents to delete.
         :returns: The number of documents deleted.
+        :raises FilterError: If the filter structure is invalid.
+        :raises DocumentStoreError: If the FAISS index is unexpectedly unavailable when removing embeddings.
         """
         docs_to_delete = self.filter_documents(filters)
         ids = [doc.id for doc in docs_to_delete]
@@ -382,6 +405,7 @@ def count_documents_by_filter(self, filters: dict[str, Any]) -> int:
 
         :param filters: A dictionary of filters to apply.
         :returns: The number of matching documents.
+        :raises FilterError: If the filter structure is invalid.
         """
         return len(self.filter_documents(filters))
 
@@ -395,6 +419,7 @@ def update_by_filter(self, filters: dict[str, Any], meta: dict[str, Any]) -> int
         :param filters: A dictionary of filters to apply to find documents to update.
         :param meta: A dictionary of metadata key-value pairs to update in the matching documents.
         :returns: The number of documents updated.
+        :raises FilterError: If the filter structure is invalid.
         """
         docs_to_update = self.filter_documents(filters)
         for doc in docs_to_update:
@@ -505,9 +530,11 @@ def from_dict(cls, data: dict[str, Any]) -> "FAISSDocumentStore":
     def save(self, index_path: str | Path) -> None:
         """
         Saves the index and documents to disk.
+
+        :raises DocumentStoreError: If the FAISS index is unexpectedly unavailable.
         """
         path = Path(index_path)
-        faiss.write_index(self.index, str(path.with_suffix(".faiss")))
+        faiss.write_index(self._get_index_or_raise(), str(path.with_suffix(".faiss")))
 
         # Save documents and ID mapping
         data = {
@@ -523,6 +550,8 @@ def save(self, index_path: str | Path) -> None:
     def load(self, index_path: str | Path) -> None:
         """
         Loads the index and documents from disk.
+
+        :raises ValueError: If the `.faiss` file does not exist.
         """
         path = Path(index_path)
         if not path.with_suffix(".faiss").exists():