Ask an aside from selected text without interrupting the agent #25533

Selecting text in an assistant response currently offers Cite. Sometimes I just want to ask what that part means while the agent keeps working. Sending the question normally steers the agent or adds another turn to the main conversation.

Add Aside next to Cite. Select a phrase, ask a question about it, and read the answer in a dismissible panel.

• Use the provider's native side-question mechanism, starting with Claude's /btw.
• Include the selected text and use the current session's context.
• Leave the running turn alone. Neither the question nor the answer should enter the main conversation history.
• Make the action unavailable when the provider or session cannot do native side questions.

For example, select “byte-array round-trip” and ask “What does that mean here?” without changing the task the agent is working on.

Start with the existing text-selection menu on web and desktop. Claude Agent SDK 0.3.276 exposes askSideQuestion at runtime, but omits it from its TypeScript declarations; SDK and CLI compatibility need checking before relying on it.

Related: #15758 covers the broader Side Chat workflow. This request scopes Aside to the selection menu and the provider's native side-question behavior.

Created with GPT-6.1 Sol in Codex, running in T3 Code.