v2.5.15

A Workflow can now be used directly as a step inside another workflow, enabling modular composition of reusable sub-pipelines. The inner workflow runs as a single step in the outer workflow, with its output chained to the next step via the standard StepInput/StepOutput interface. Complex orchestrations can be broken into smaller, independently testable units and assembled without duplicating logic — the same sub-workflow can be reused across multiple parent workflows.

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Details:

• Pass a Workflow instance to a Step via Step(name="...", workflow=inner_workflow), or use the shorthand auto-wrap by placing the workflow directly in the steps list (uses the workflow's name as the step name)
• Inner workflows support the full set of primitives — Condition, Loop, Router, Parallel, agents, and custom executors — mixed in any combination
• Session state is deep-copied into the inner workflow before execution and merged back into the outer workflow after, keeping state consistent across levels
• Workflows can be nested multiple levels deep; streaming events bubble up with a nested_depth field so outer and inner events can be distinguished by depth, workflow_id, and workflow_name
• Enables modular workflow design: build reusable research, processing, or review sub-pipelines once and compose them into larger orchestrations

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See the Nested Workflow docs to learn more.