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Overview

The re-run from step feature in Agent Builder Preview allows you to re-run an agent workflow from a previously executed step, reusing the preserved state and outputs from earlier steps. This streamlines iteration and debugging for complex, multi-step agents by skipping re-execution of unchanged steps. Previously, making changes to any step in a multi-step agent required re-running the entire workflow from the beginning. With this feature, you can quickly test changes to later steps without waiting for the whole workflow to re-execute.

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Key concepts

  • Eligibility: Only steps that were successfully executed in the most recent Preview run are eligible for re-run. Steps in unexecuted branches, sub-agents, or loops are not eligible.
  • Session limitation: re-run is available for approximately 2 hours after the last Preview run. After this period, a full run is required to re-enable the feature.

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What you can do with re-run from step

  • Re-run your agent from any successfully executed step without re-running earlier steps
  • Quickly iterate on later steps in your workflow without waiting for the full execution
  • Review which steps are cached versus re-executed in the debug view

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Re-run an agent from a specific step

  1. Open your agent in the Agent Builder and run a full Preview to execute all steps.
  2. In the workflow or step list view, select any step that was successfully executed in the most recent Preview run.
  3. Click Play from this step to re-run the agent from that point onward, reusing the states and outputs from earlier steps.
  4. Review results in the debug view. Cached steps and re-executed steps are clearly distinguished in the UI.
Each re-run from a step creates a new session to preserve the integrity of the workflow and debugging context. Follow-up queries use the context from the re-run session.

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Eligibility and invalidation

Steps become ineligible for re-run if:
  • The workflow is modified (steps added, removed, or edited)
  • Inputs change
  • The session expires (after approximately 2 hours)
  • Preview is reset
If a step is ineligible, the play button is disabled.

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Known behaviors and limitations

  • Only top-level workflow steps are supported. Steps inside sub-agents or loops are not eligible for re-run.
  • Only the most recent Preview session is supported. You cannot select historical runs.
  • Re-run always continues through to the end of the workflow. Single-step execution is not supported.
  • Editing or manipulating step outputs directly is not supported.
  • After 2 hours or after workflow, input changes or preview reset, a new full run is required to re-run any steps.