diff --git a/README.md b/README.md
index 4625b2c..ec67fae 100644
--- a/README.md
+++ b/README.md
@@ -4134,6 +4134,113 @@ client.create_model_monitoring_request_results(
 )
 ```
 
+## Workspace User
+
+### Get workspace users
+
+Returns a list of internal workspace users. (Up to 20 at a time by default)
+Each user includes its granted module permissions in `functionResourcePermissions`.
+
+```python
+import fastlabel
+client = fastlabel.Client()
+
+users = client.get_workspace_users(
+    keyword="",  # Search keyword for name or email (Optional)
+    offset=0,    # The starting position number to fetch (Optional)
+    limit=20,    # The max number to fetch (Optional, default 20)
+)
+# [
+#   {
+#     "id": "...",
+#     "userId": "...",
+#     "userSlug": "...",
+#     "userName": "John Doe",
+#     "userEmail": "john@example.com",
+#     "role": "member",
+#     "isExternal": False,
+#     "createdAt": "...",
+#     "updatedAt": "...",
+#     "functionResourcePermissions": {
+#       "annotation": True,
+#       "modelDev": False,
+#       "dataset": False
+#     }
+#   }
+# ]
+```
+
+### Create workspace user
+
+Creates an internal workspace user. The `slug` is generated automatically on the server side.
+Module permissions are managed separately (see below).
+
+```python
+user = client.create_workspace_user(
+    name="John Doe",
+    email="john@example.com",
+    language="en",  # 'en' or 'ja'
+    role="member",  # 'member' or 'owner'
+)
+```
+
+### Update workspace user
+
+Updates an internal workspace user. Only the `role` can be changed.
+
+```python
+user = client.update_workspace_user(
+    id="YOUR_WORKSPACE_USER_ID",
+    role="owner",  # 'member' or 'owner' (Optional)
+)
+```
+
+### Delete workspace user
+
+Deletes an internal workspace user.
+
+```python
+client.delete_workspace_user(id="YOUR_WORKSPACE_USER_ID")
+```
+
+### Grant module permissions
+
+Grants module permissions to an internal workspace user.
+`modules` accepts a single module or a list (each is sent as a separate request).
+
+```python
+# Single module
+client.create_workspace_user_module_permissions(
+    workspace_user_id="YOUR_WORKSPACE_USER_ID",
+    modules="annotation",  # 'annotation', 'modelDev' or 'dataset'
+)
+
+# Multiple modules
+client.create_workspace_user_module_permissions(
+    workspace_user_id="YOUR_WORKSPACE_USER_ID",
+    modules=["annotation", "dataset"],
+)
+```
+
+### Revoke module permissions
+
+Revokes module permissions from an internal workspace user.
+`modules` accepts a single module or a list (each is sent as a separate request).
+
+```python
+# Single module
+client.delete_workspace_user_module_permissions(
+    workspace_user_id="YOUR_WORKSPACE_USER_ID",
+    modules="annotation",  # 'annotation', 'modelDev' or 'dataset'
+)
+
+# Multiple modules
+client.delete_workspace_user_module_permissions(
+    workspace_user_id="YOUR_WORKSPACE_USER_ID",
+    modules=["annotation", "dataset"],
+)
+```
+
 ## API Docs
 
 Check [this](https://api.fastlabel.ai/docs/) for further information.
diff --git a/fastlabel/__init__.py b/fastlabel/__init__.py
index 0155359..e2c8f0f 100644
--- a/fastlabel/__init__.py
+++ b/fastlabel/__init__.py
@@ -5471,6 +5471,140 @@ def get_project_comments(
             params["limit"] = limit
         return self.api.get_request(endpoint, params=params)
 
+    def get_workspace_users(
+        self,
+        keyword: str = None,
+        offset: int = None,
+        limit: int = 20,
+    ) -> list:
+        """
+        Returns a list of internal workspace users.
+        keyword is a search keyword for name or email (Optional).
+        offset is the starting position number to fetch (Optional).
+        limit is the max number to fetch (Optional, default 20).
+        """
+        endpoint = "workspaces-users"
+        params = {}
+        if keyword:
+            params["keyword"] = keyword
+        if offset is not None:
+            params["offset"] = offset
+        if limit is not None:
+            params["limit"] = limit
+        return self.api.get_request(endpoint, params=params)
+
+    def create_workspace_user(
+        self,
+        name: str,
+        email: str,
+        language: str,
+        role: str,
+    ) -> dict:
+        """
+        Creates an internal workspace user and returns the created user.
+        name is the user's name (Required).
+        email is the user's email address (Required).
+        language is the user's language, 'en' or 'ja' (Required).
+        role is the workspace role, 'member' or 'owner' (Required).
+        Module permissions are managed separately; use
+        create_workspace_user_module_permission to grant them.
+        """
+        endpoint = "workspaces-users/internal-users"
+        payload = {
+            "name": name,
+            "email": email,
+            "language": language,
+            "role": role,
+        }
+        return self.api.post_request(endpoint, payload=payload)
+
+    def update_workspace_user(
+        self,
+        id: str,
+        role: str = None,
+    ) -> dict:
+        """
+        Updates an internal workspace user and returns the updated user.
+        Only the role can be changed.
+        id is the id of the workspace user (Required).
+        role is the workspace role, 'member' or 'owner' (Optional).
+        """
+        endpoint = f"workspaces-users/internal-users/{id}"
+        payload = {}
+        if role:
+            payload["role"] = role
+        return self.api.put_request(endpoint, payload=payload)
+
+    def delete_workspace_user(self, id: str) -> None:
+        """
+        Deletes an internal workspace user.
+        id is the id of the workspace user (Required).
+        """
+        endpoint = f"workspaces-users/internal-users/{id}"
+        self.api.delete_request(endpoint)
+
+    def create_workspace_user_module_permissions(
+        self,
+        workspace_user_id: str,
+        modules: Union[str, List[str]],
+    ) -> List[str]:
+        """
+        Grants module permissions to an internal workspace user.
+        Each module is granted with a separate request; if one fails (e.g. the
+        module user limit is reached), the permissions granted before it remain.
+        workspace_user_id is the id of the workspace user (Required).
+        modules is a single module or a list of modules, each one of
+        'annotation', 'modelDev', 'dataset' (Required).
+        """
+        if isinstance(modules, str):
+            modules = [modules]
+        module_paths = {
+            "annotation": "annotation",
+            "dataset": "dataset",
+            "modelDev": "model-dev",
+        }
+        results = []
+        for module in modules:
+            if module not in module_paths:
+                raise FastLabelInvalidException(
+                    "module must be one of 'annotation', 'modelDev', 'dataset'.", 422
+                )
+            endpoint = (
+                f"function-resource-permissions/{module_paths[module]}/internal-users"
+            )
+            results.append(
+                self.api.post_request(
+                    endpoint, payload={"workspaceUserId": workspace_user_id}
+                )
+            )
+        return results
+
+    def delete_workspace_user_module_permissions(
+        self,
+        workspace_user_id: str,
+        modules: Union[str, List[str]],
+    ) -> None:
+        """
+        Revokes module permissions from an internal workspace user.
+        Each module is revoked with a separate request; if one fails, the
+        permissions revoked before it remain revoked.
+        workspace_user_id is the id of the workspace user (Required).
+        modules is a single module or a list of modules, each one of
+        'annotation', 'modelDev', 'dataset' (Required).
+        """
+        if isinstance(modules, str):
+            modules = [modules]
+        endpoint = "function-resource-permissions"
+        for module in modules:
+            if module not in ("annotation", "modelDev", "dataset"):
+                raise FastLabelInvalidException(
+                    "module must be one of 'annotation', 'modelDev', 'dataset'.", 422
+                )
+            self.api.delete_request(
+                endpoint,
+                payload={"workspaceUserId": workspace_user_id, "resource": module},
+            )
+
     def mask_to_fastlabel_segmentation_points(
         self, mask_image: Union[str, np.ndarray]
     ) -> List[List[List[int]]]:
diff --git a/fastlabel/api.py b/fastlabel/api.py
index 20e5188..6df9c8c 100644
--- a/fastlabel/api.py
+++ b/fastlabel/api.py
@@ -44,7 +44,7 @@ def get_request(self, endpoint: str, params=None) -> Union[dict, list]:
             else:
                 raise FastLabelException(error, r.status_code)
 
-    def delete_request(self, endpoint: str, params=None) -> dict:
+    def delete_request(self, endpoint: str, params=None, payload=None) -> dict:
         """Makes a delete request to an endpoint.
         If an error occurs, assumes that endpoint returns JSON as:
             { 'statusCode': XXX,
@@ -55,7 +55,9 @@ def delete_request(self, endpoint: str, params=None) -> dict:
             "Content-Type": "application/json",
             "Authorization": self.access_token,
         }
-        r = requests.delete(self.base_url + endpoint, headers=headers, params=params)
+        r = requests.delete(
+            self.base_url + endpoint, headers=headers, params=params, json=payload
+        )
 
         if r.status_code == 200 or r.status_code == 204:
             return
diff --git a/fastlabel/exceptions.py b/fastlabel/exceptions.py
index 7f0a4ba..62415f8 100644
--- a/fastlabel/exceptions.py
+++ b/fastlabel/exceptions.py
@@ -1,10 +1,14 @@
 class FastLabelException(Exception):
-    def __init__(self, message, errcode):
+    def __init__(self, message, errcode=None):
         super(FastLabelException, self).__init__(
             "<Response [{}]> {}".format(errcode, message)
         )
+        self.message = message
         self.code = errcode
 
+    def __reduce__(self):
+        return (self.__class__, (self.message, self.code))
+
 
 class FastLabelInvalidException(FastLabelException, ValueError):
     pass
diff --git a/tests/test_workspace_user.py b/tests/test_workspace_user.py
new file mode 100644
index 0000000..90176fa
--- /dev/null
+++ b/tests/test_workspace_user.py
@@ -0,0 +1,206 @@
+"""Tests for the workspace user API client methods.
+
+These verify that get/create/update/delete_workspace_user build the correct
+endpoint, query params and payload. The HTTP layer (client.api.*_request) is
+stubbed so no real request is made.
+"""
+import pytest
+
+import fastlabel
+
+
+@pytest.fixture
+def client(monkeypatch):
+    monkeypatch.setenv("FASTLABEL_ACCESS_TOKEN", "dummy-token")
+    return fastlabel.Client()
+
+
+def _capture(monkeypatch, client, method_name, return_value=None):
+    """Replace an api.*_request method with a recorder and return the calls list."""
+    calls = []
+
+    def fake(endpoint, *args, **kwargs):
+        calls.append({"endpoint": endpoint, "args": args, "kwargs": kwargs})
+        return return_value
+
+    monkeypatch.setattr(client.api, method_name, fake)
+    return calls
+
+
+# --- get_workspace_users ---------------------------------------------------
+
+
+def test_get_workspace_users_default(monkeypatch, client):
+    calls = _capture(monkeypatch, client, "get_request", return_value=[])
+
+    client.get_workspace_users()
+
+    assert calls[0]["endpoint"] == "workspaces-users"
+    # keyword/offset are omitted, limit defaults to 20
+    assert calls[0]["kwargs"]["params"] == {"limit": 20}
+
+
+def test_get_workspace_users_with_params(monkeypatch, client):
+    calls = _capture(monkeypatch, client, "get_request", return_value=[])
+
+    client.get_workspace_users(keyword="john", offset=10, limit=50)
+
+    assert calls[0]["kwargs"]["params"] == {
+        "keyword": "john",
+        "offset": 10,
+        "limit": 50,
+    }
+
+
+def test_get_workspace_users_offset_zero_included(monkeypatch, client):
+    calls = _capture(monkeypatch, client, "get_request", return_value=[])
+
+    client.get_workspace_users(offset=0)
+
+    # offset=0 should still be sent (is not None), keyword empty is omitted
+    assert calls[0]["kwargs"]["params"] == {"offset": 0, "limit": 20}
+
+
+# --- create_workspace_user -------------------------------------------------
+
+
+def test_create_workspace_user_without_modules(monkeypatch, client):
+    calls = _capture(monkeypatch, client, "post_request", return_value={})
+
+    client.create_workspace_user(
+        name="John Doe",
+        email="john@example.com",
+        language="en",
+        role="member",
+    )
+
+    assert calls[0]["endpoint"] == "workspaces-users/internal-users"
+    assert calls[0]["kwargs"]["payload"] == {
+        "name": "John Doe",
+        "email": "john@example.com",
+        "language": "en",
+        "role": "member",
+    }
+
+
+# --- update_workspace_user -------------------------------------------------
+
+
+def test_update_workspace_user_role_only(monkeypatch, client):
+    calls = _capture(monkeypatch, client, "put_request", return_value={})
+
+    client.update_workspace_user(id="wsu-1", role="owner")
+
+    assert calls[0]["endpoint"] == "workspaces-users/internal-users/wsu-1"
+    assert calls[0]["kwargs"]["payload"] == {"role": "owner"}
+
+
+def test_update_workspace_user_role_omitted(monkeypatch, client):
+    calls = _capture(monkeypatch, client, "put_request", return_value={})
+
+    client.update_workspace_user(id="wsu-1")
+
+    # role omitted -> empty payload
+    assert calls[0]["kwargs"]["payload"] == {}
+
+
+# --- delete_workspace_user -------------------------------------------------
+
+
+def test_delete_workspace_user(monkeypatch, client):
+    calls = _capture(monkeypatch, client, "delete_request", return_value=None)
+
+    result = client.delete_workspace_user(id="wsu-1")
+
+    assert calls[0]["endpoint"] == "workspaces-users/internal-users/wsu-1"
+    assert result is None
+
+
+# --- create_workspace_user_module_permissions ------------------------------
+
+
+@pytest.mark.parametrize(
+    "module, expected_path",
+    [
+        ("annotation", "function-resource-permissions/annotation/internal-users"),
+        ("dataset", "function-resource-permissions/dataset/internal-users"),
+        ("modelDev", "function-resource-permissions/model-dev/internal-users"),
+    ],
+)
+def test_create_module_permissions_single(monkeypatch, client, module, expected_path):
+    calls = _capture(monkeypatch, client, "post_request", return_value=module)
+
+    # a single module string is accepted (not only a list)
+    result = client.create_workspace_user_module_permissions(
+        workspace_user_id="wsu-1", modules=module
+    )
+
+    assert len(calls) == 1
+    assert calls[0]["endpoint"] == expected_path
+    assert calls[0]["kwargs"]["payload"] == {"workspaceUserId": "wsu-1"}
+    assert result == [module]
+
+
+def test_create_module_permissions_multiple(monkeypatch, client):
+    calls = _capture(monkeypatch, client, "post_request", return_value="ok")
+
+    result = client.create_workspace_user_module_permissions(
+        workspace_user_id="wsu-1", modules=["annotation", "dataset"]
+    )
+
+    assert [c["endpoint"] for c in calls] == [
+        "function-resource-permissions/annotation/internal-users",
+        "function-resource-permissions/dataset/internal-users",
+    ]
+    assert all(c["kwargs"]["payload"] == {"workspaceUserId": "wsu-1"} for c in calls)
+    assert result == ["ok", "ok"]
+
+
+def test_create_module_permissions_invalid_module(monkeypatch, client):
+    _capture(monkeypatch, client, "post_request", return_value=None)
+
+    with pytest.raises(fastlabel.exceptions.FastLabelInvalidException):
+        client.create_workspace_user_module_permissions(
+            workspace_user_id="wsu-1", modules="unknown"
+        )
+
+
+# --- delete_workspace_user_module_permissions ------------------------------
+
+
+def test_delete_module_permissions_single(monkeypatch, client):
+    calls = _capture(monkeypatch, client, "delete_request", return_value=None)
+
+    client.delete_workspace_user_module_permissions(
+        workspace_user_id="wsu-1", modules="modelDev"
+    )
+
+    assert len(calls) == 1
+    assert calls[0]["endpoint"] == "function-resource-permissions"
+    assert calls[0]["kwargs"]["payload"] == {
+        "workspaceUserId": "wsu-1",
+        "resource": "modelDev",
+    }
+
+
+def test_delete_module_permissions_multiple(monkeypatch, client):
+    calls = _capture(monkeypatch, client, "delete_request", return_value=None)
+
+    client.delete_workspace_user_module_permissions(
+        workspace_user_id="wsu-1", modules=["annotation", "modelDev"]
+    )
+
+    assert [c["kwargs"]["payload"]["resource"] for c in calls] == [
+        "annotation",
+        "modelDev",
+    ]
+    assert all(c["endpoint"] == "function-resource-permissions" for c in calls)
+
+
+def test_delete_module_permissions_invalid_module(monkeypatch, client):
+    _capture(monkeypatch, client, "delete_request", return_value=None)
+
+    with pytest.raises(fastlabel.exceptions.FastLabelInvalidException):
+        client.delete_workspace_user_module_permissions(
+            workspace_user_id="wsu-1", modules="unknown"
+        )