Forking a snapshot into a different vendor: the new session starts from a handoff bundle from `export_context` instead of the vendor's native fork, and the UI labels it a handoff, not a true fork. Same-vendor forks from a snapshot exist (see "Forking" in `docs/operations.md`).
`spawn_stages(stages[])` and `collect(stage_ids[])` MCP tools let agents build workflows on the fly, using the same stage definition format. An optional per-workflow human gate on spawning. Spawned stages show in the task's UI tree marked as just-in-time, and a just-in-time structure can be saved as a reusable workflow.