Continue a structured handoff in a fresh thread

[timothyachumba]

A long agent thread often contains one completed task and the context for the next. Carrying the full conversation forward wastes context, while manually opening a thread and rebuilding the useful state is easy to skip.\n\nI propose a small explicit flow for web and desktop. An agent skill emits a compact handoff inside a versioned HTML-comment marker. The completed assistant response then shows Continue in new thread. Clicking it atomically creates and starts a thread in the same project and checkout, sends the handoff as the first message with a backlink, and settles the previous thread when supported.\n\nThe marker keeps completion detection explicit and avoids guessing from ordinary responses. It also lets Claude, Codex, and other providers share the same client behavior without provider-specific changes.

[timothyachumba]

I should have searched the existing discussions and closed PRs before opening this. #8433 already tracks agent-controlled T3 threads, while PRs #7487, #8452, and #8492 explored agent-requested and fresh-thread handoffs. #8452 was explicitly closed on August 28, 2026 because a separate Continue in new thread action is not a priority. Closing this duplicate rather than splitting the proposal history.