fix(pkg-py): Set system_prompt on client during initialization (#188)

* fix(pkg-py): Set system_prompt on client during initialization

The system_prompt was not being set on _client during initialization,
causing the chat to have no context about the data. This resulted in
nonsense greetings and broken functionality.

Fixes #187

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* feat(pkg-py): Add tools parameter to QueryChatExpress

The tools parameter was missing from QueryChatExpress.__init__(),
preventing Express users from customizing which tools are available.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: cpsievert

pkg-py/src/querychat/_querychat.py

@@ -79,6 +79,7 @@ def __init__(
         client = as_querychat_client(client)
         self._client = copy.deepcopy(client)
         self._client.set_turns([])
+        self._client.system_prompt = self._system_prompt.render(self.tools)
 
         # Storage for console client
         self._client_console = None
@@ -142,7 +143,7 @@ def app_server(input: Inputs, output: Outputs, session: Session):
                 self.id,
                 data_source=self._data_source,
                 greeting=self.greeting,
-                client=self._client,
+                client=self.client(),
                 enable_bookmarking=enable_bookmarking,
             )
 
@@ -719,6 +720,19 @@ def data_table():
         If `client` is not provided, querychat consults the
         `QUERYCHAT_CLIENT` environment variable. If that is not set, it
         defaults to `"openai"`.
+    tools
+        Which querychat tools to include in the chat client by default. Can be:
+        - A single tool string: `"update"` or `"query"`
+        - A tuple of tools: `("update", "query")`
+        - `None` or `()` to disable all tools
+
+        Default is `("update", "query")` (both tools enabled).
+
+        Set to `"update"` to prevent the LLM from accessing data values, only
+        allowing dashboard filtering without answering questions.
+
+        The tools can be overridden per-client by passing a different `tools`
+        parameter to the `.client()` method.
     data_description
         Description of the data in plain text or Markdown. If a pathlib.Path
         object is passed, querychat will read the contents of the path into a
@@ -751,6 +765,7 @@ def __init__(
         id: Optional[str] = None,
         greeting: Optional[str | Path] = None,
         client: Optional[str | chatlas.Chat] = None,
+        tools: TOOL_GROUPS | tuple[TOOL_GROUPS, ...] | None = ("update", "query"),
         data_description: Optional[str | Path] = None,
         categorical_threshold: int = 20,
         extra_instructions: Optional[str | Path] = None,
@@ -771,6 +786,7 @@ def __init__(
             id=id,
             greeting=greeting,
             client=client,
+            tools=tools,
             data_description=data_description,
             categorical_threshold=categorical_threshold,
             extra_instructions=extra_instructions,
@@ -793,7 +809,7 @@ def __init__(
             self.id,
             data_source=self._data_source,
             greeting=self.greeting,
-            client=self._client,
+            client=self.client(),
             enable_bookmarking=enable,
         )
 

pkg-py/tests/test_querychat.py

@@ -60,3 +60,30 @@ def test_querychat_custom_id(sample_df):
     )
 
     assert qc.id == "custom_id"
+
+
+def test_querychat_client_has_system_prompt(sample_df):
+    """
+    Test that the client returned by .client() has a system prompt set.
+
+    Regression test for issue #187: the system prompt was missing because
+    _client.system_prompt wasn't being set during initialization.
+    """
+    qc = QueryChat(
+        data_source=sample_df,
+        table_name="test_table",
+        greeting="Hello!",
+    )
+
+    # The client() method should return a chat with the system prompt set
+    client = qc.client()
+    assert client.system_prompt is not None
+    assert len(client.system_prompt) > 0
+
+    # The system_prompt should contain the table name since it includes schema info
+    assert "test_table" in client.system_prompt
+
+    # The internal _client should also have the system prompt set
+    # (needed for methods like generate_greeting() that use _client directly)
+    assert qc._client.system_prompt is not None
+    assert "test_table" in qc._client.system_prompt