Update changelog; simplify; pass type checks

Author: cpsievert

CHANGELOG.md

@@ -7,6 +7,12 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 -->
 
+## [UNRELEASED]
+
+### Bug fixes
+
+* Fixed an issue where `.chat()` wasn't streaming output properly in (the latest build of) Positron's Jupyter notebook. (#131)
+
 ## [0.9.0] - 2025-07-02
 
 ### New features

chatlas/_chat.py

@@ -2429,9 +2429,7 @@ def is_quarto():
 
 def is_positron_notebook():
     try:
-        get_ipython  # type: ignore[name-defined]
-    except NameError:
+        mode = get_ipython().session_mode  # noqa: F821 # type: ignore
+        return mode == "notebook"
+    except Exception:
         return False
-    ipython = get_ipython()  # type: ignore[name-defined]
-    session_mode = getattr(ipython, "session_mode", None)
-    return session_mode == "notebook"