Think: /sidechat and Steer Conversations

[esokullu]

Let's think, discuss how we could technically add these features. Don't touch the code yet, because these need careful planning beforehand.

[alectimison-maker]

I suggest implementing this in two phases. First, model /sidechat as an independent side conversation linked to the main conversation through a parentConversationId. It should have its own thread and transcript, optionally receive selected text and a read-only snapshot of the parent task, while the main conversation continues running. By default, Side Chat should operate in Ask/Chat mode only and should not inherit browser actions, file writes, or other side-effectful tools. The read-only safety boundary in CoWork-OS Side Chat, and the hidden child-session, parent-child relationship, and context-inheritance design in dsh-side-chat, would be useful references.

In the second phase, introduce a run-scoped follow-up queue in the agent runtime: regular messages use enqueue and are processed FIFO after the current turn finishes, while steer messages are injected before the next LLM request; if the current turn has already completed, the message should automatically fall back to the queue. Queue and steering state should be owned by the background/agent runtime rather than only the UI, so messages are not lost when the sidebar reloads, with explicit states such as queued, injected, fallback, and failed. The queue/steer/interrupt design in Junction, together with the semantics documented in GitHub Copilot SDK's Steering and Queueing, provides a useful reference. This would give us a safe, testable Side Chat foundation before adding full steering support.