VS Code extension: Support /side and /btw side conversations

What variant of Codex are you using?

IDE Extension (VS Code)

What feature would you like to see?

Please add side conversations to the Codex VS Code extension, accessible through /side and /btw or an equivalent UI action.

While Codex is working on a task, I want to ask questions about its reasoning, findings, or the code without interrupting or redirecting that task. The side conversation should inherit the main conversation's context so I do not need to repeat the background.

Proposed behavior

• Open a side conversation from the current chat, including while the main task is running.
• Give the side conversation access to the main chat's context.
• Keep side-chat messages and answers separate from the main conversation; they should not automatically steer the active task.
• Let the main task continue while I ask follow-up questions in the side chat.
• Prefer a side-by-side pane so both conversations remain visible, with a straightforward way to close the side chat and return to the main chat.

Example use case

Codex is implementing a change. I want to ask, "Why did you choose this approach?" or "Can you explain the function you just mentioned?" in a side conversation while implementation continues.

Related issues

• #18125 — Add a way to ask side questions without affecting the main session context (closed; requested for CLI and Codex app).
• #28186 — Render /side and /btw conversations in a TUI sidecar pane (terminal UI presentation).
• #34498 — Show /side chats in a split pane instead of replacing the main chat (description specifies CLI).

This request specifically asks for side-conversation support in the VS Code extension, with the related issues providing context for the desired interaction.

Start by reviewing the VS Code extension's existing chat and task-running flows, then compare the requested behavior with related issues #18125, #28186, and #34498. Define how a side conversation inherits context without steering the active task, remains visible alongside it, and can be closed; done means these interactions work while the main task continues.