Support for extensions to control tool invocation collapse behavior in Chat

[OrenMe]

Description

Currently, extensions contributing Chat Tools do not have direct control over whether their tool invocations are pinned (expanded) or collapsed into the "thinking" section of the Chat response. VS Code currently uses hardcoded logic in shouldPinPart() to decide this based on the tool ID or source type (e.g., MCP tools, Mermaid, copilot_askQuestions).

This is particularly problematic for extensions that contribute rich content, such as webviews, using the chat renderer interface. If a webview is rendered inside a collapsed section, it may not initialize or render correctly, which appears to be a bug in how collapsed tool outputs are handled.

Proposed Solution

We propose a hybrid approach to give extensions control:

1. Declarative Control: Add a displayStyle property to the languageModelTools contribution point in package.json.

   "languageModelTools": [
     {
       "name": "myTool",
       "displayStyle": "expanded"
     }
   ]

2. Runtime Control: Extend the presentation property in the ToolInvocationPresentation API (via prepareToolInvocation) to include an expanded option.

Technical Details

• The logic in src/vs/workbench/contrib/chat/browser/widget/chatListRenderer.ts (specifically shouldPinPart) should be updated to respect these new metadata/runtime preferences.
• A runtime presentation: 'expanded' should take precedence over the static displayStyle declared in package.json.

[iwangbowen]

Is ToolInvocationPresentation a new proposed API?

[OrenMe]

Yes
Although maybe this is a bit overboard
Maybe we can make this a passive thing and make any tool donating a webview get unpinned instead of letting extension decide

[OrenMe]

@iwangbowen now I understand why u asked about this
What r the chances we both opened this on the same day :-)

#292119

I guess we can collapse this to one issue

What are your needs for this? U also creating an extension donating chat responses?

[iwangbowen]

@OrenMe I am not looking to create an extension right now. I just noticed that some people have created MCP apps, so I was wondering if LM tools could support similar functionality.

BTW, Where did you find the examples for using the ToolInvocationPresentation API?