Add Code Errors to Agent Context with @diagnostics

When working in the Agent Panel, you can now use @diagnostics to inject current language server errors and warnings directly into your conversation. This makes it effortless to get AI help fixing compiler errors or code issues.

How to Use

1. Open the Agent Panel and start a new thread
2. Type @diagnostics in the message editor
3. Select it from the autocomplete menu
4. The agent receives all current LSP diagnostics as context
5. Ask the agent to fix the errors

What Gets Included

By default, @diagnostics includes:

• Errors: All compilation errors from your language server
• File locations: Exact file paths and line numbers
• Error messages: Full diagnostic descriptions

You can also include warnings with:

@diagnostics?include_warnings=true

Example Workflow

You: @diagnostics Fix these TypeScript errors

Agent: I see 3 type errors in your code:
1. src/app.ts:42 - Property 'name' does not exist on type 'User'
2. src/utils.ts:15 - Type 'string' is not assignable to type 'number'
...

Let me fix them for you.

Why It’s Useful

Faster debugging: No need to manually copy-paste error messages into the chat.

Full context: The agent sees all errors at once, not just the one you’re focused on.

Cursor-aware workflow: Stay in the Agent Panel instead of switching to slash commands or text threads.

Parity with text threads: Brings the /diagnostics slash command functionality to the new thread experience.

Perfect for when you have a pile of compiler errors and need AI assistance to resolve them quickly!

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Related PR: #42270