Update changelog

Author: cpsievert

pkg-py/CHANGELOG.md

@@ -7,10 +7,16 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [UNRELEASED]
 
+* Numerous `Chat()` features have been deprecated in preparation for future removal to simplify the API (#91)
+  * `Chat(messages=...)` was deprecated. Use `chat.ui(messages=...)` instead.
+  * `Chat(tokenizer=...)` was deprecated. This is only relevant for `.messages(token_limits=...)` which is also now deprecated.
+  * All parameters to `.messages()` were deprecated. This reflects an overall change philosophy for maintaining the conversation history sent to the LLM -- `Chat` should no longer be responsible for maintaining it -- another stateful object (perhaps the one provided by chatlas, LangChain, etc.) should be used instead. That said, `.messages()` is still useful if you want to access UI message state.
+  * The `.transform_user_input` and `.transform_assistant_response` decorators were deprecated. Instead, transformation of input/responses should be done manually and independently of `Chat`.
+  * As a result of the previous deprecations, `.user_input(transform=...)` was also deprecated.
+
 * The chat input no longer submits incomplete text when the user has activated IME completions (e.g. while typing in Japanese or Chinese). (#85)
 
 
 ## [0.1.0] - 2025-08-07
 
-This first release of the `shinychat` package simply copies the `Chat` and `MarkdownStream` components exactly as they are in version 1.4.0 of `shiny`. Future versions of `shiny` will import these components from `shinychat`. By maintaining these components via a separate library, we can ship features more quickly and independently of `shiny`.
-
+This first release of the `shinychat` package simply copies the `Chat` and `MarkdownStream` components exactly as they are in version 1.4.0 of `shiny`. Future versions of `shiny` will import these components from `shinychat`. By maintaining these components via a separate library, we can ship features more quickly and independently of `shiny`.