feat: partial turn preservation and cooperative stream cancellation

CHANGELOG.md

@@ -13,6 +13,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 
 * The `.stream()` and `.stream_async()` methods now yield `ContentThinking` objects (instead of plain strings) for thinking/reasoning content when `content="all"`. This allows downstream packages like shinychat to provide specific UI for thinking content. (#276)
+* New `StreamController` class for cooperative stream cancellation. Pass a controller to `.stream()` or `.stream_async()` and call `controller.cancel()` to stop the stream cleanly (e.g., from a Shiny "stop generating" button). The partial response is preserved in conversation history. (#279)
+* When a stream is interrupted (closed early, cancelled, or errors), the accumulated content is now saved as a partial `AssistantTurn` so conversation state isn't lost. Partial turns display `[interrupted]` (or the cancellation reason) in the `Chat` repr and are excluded from token/cost accounting. (#279)
 * Built-in tools (`tool_web_search()`, `tool_web_fetch()`) now include `description` and `annotations` properties, making their metadata consistent with user-defined tools created by `Tool()`. (#278)
 
 ### Bug fixes

chatlas/__init__.py

@@ -33,6 +33,7 @@
 from ._provider_perplexity import ChatPerplexity
 from ._provider_portkey import ChatPortkey
 from ._provider_snowflake import ChatSnowflake
+from ._stream_controller import StreamController
 from ._tokens import token_usage
 from ._tools import Tool, ToolBuiltIn, ToolRejectError
 from ._tools_builtin import tool_web_fetch, tool_web_search
@@ -83,6 +84,7 @@
     "interpolate",
     "interpolate_file",
     "Provider",
+    "StreamController",
     "token_usage",
     "Tool",
     "ToolBuiltIn",