Rerun a run

Every run in Union.ai is durable: its task, code, inputs, and configuration are all recorded on the backend. That means you can launch a brand-new run from any previous one without having the original code checked out locally. This is useful for retrying a transient failure, reproducing a result, or tweaking a few inputs and running again.

You can rerun at two levels of granularity:

The whole run: re-execute the entry point task (the a0 action) and everything it calls.
A single action: re-execute one nested action on its own.

And you can trigger a rerun from three places: the UI, the CLI, or programmatically with the Python SDK.

Rerun from the UI

Rerun an entire run

Open the run in the UI. In the top-right corner of the run view, click Rerun.

This opens the launch form pre-filled with the original run’s inputs, environment variables, and code. You can either:

Trigger the run as-is to reproduce the original execution exactly, or
Edit the inputs, environment variables, and other launch settings in the form before triggering to run a variation.

The launch form, pre-filled with the run’s recorded inputs

Rerun a single action

You can also rerun an individual action without rerunning the whole workflow. Navigate to the action in the run’s action list, open its details view, and use the Rerun action option (in the action menu in the top-right of the action details panel).

This launches a new run starting from that action, using the action’s recorded inputs. As with a full rerun, you can adjust the inputs in the launch form first.

Run lineage

When you rerun a run from the UI, Union.ai records the run you started from as the new run’s parent. This provenance is captured automatically, so you never have to set it yourself. A parent link is also recorded when a run is derived from another run in other ways, such as recovering a failed run.

Run lineage lets you trace a run back to the one it was started from.

The parent is surfaced in two places in the console:

In the run list, a rerun is marked with a rerun icon next to its run ID. Hover the icon to see “Rerun of” and the ID of the parent run, so you can tell at a glance which runs were started from an earlier run. A rerun also shows no trigger and is owned by the user who started it, rather than by a schedule.

A run list with the rerun icon and “Rerun of” tooltip on a rerun row

On the run details page, a rerun shows a Rerun badge next to its status. Hover the badge, or open Run info, to see the Rerun of link to the parent run.

The Rerun badge and “Rerun of” parent link on the run details page

Rerun from the CLI

flyte rerun fetches the prior run’s task and inputs from the backend and launches a new run. You don’t need the original code checked out locally. Everything is pulled from the platform:

        
# Rerun with the prior run's exact code and inputs
flyte rerun <run-name>

# Give the new run a name and stream its parent-action logs
flyte rerun <run-name> --name retry-1 --follow

Common options:

Option	Description
`-p`, `--project`	Project for the new run (defaults to your config).
`-d`, `--domain`	Domain for the new run (defaults to your config).
`--name`	Name for the new run (a random name is generated if unset).
`-e`, `--env KEY=VALUE`	Override an environment variable for the new run. Repeatable.
`--label KEY=VALUE`	Set a label on the new run. Repeatable.
`-f`, `--follow`	Stream the parent action’s logs after launch.

flyte rerun reuses the prior run’s inputs as-is. To change input values from the command line, use the programmatic flyte.rerun(<run-name>, key=value) form shown below.

Rerun compared with a fresh run

Command	Code	Inputs
`flyte run <file> <task>`	local	from CLI
`flyte rerun <run>`	fetched from backend	prior run’s

Both start the run over from the beginning. To instead keep the successful actions of a failed run and re-execute only what failed, add --recover to flyte rerun. See Recover a failed run.

flyte rerun never substitutes local code, with or without --recover. To replay a prior run with code you have changed, see Fork a run.

Rerun programmatically

Use flyte.rerun() to rerun from Python. Like the CLI, it fetches the prior run’s task and inputs from the backend, so no local code is required:

        
import flyte

flyte.init_from_config()

# Rerun a prior run with its exact inputs (task + inputs fetched from the platform):
flyte.rerun("ul56wcvgqrb9vzhzz5l2")

# Change input parameters — they are converted against the prior run's interface:
flyte.rerun("ul56wcvgqrb9vzhzz5l2", x_list=[1, 2, 3])

flyte.rerun() returns a flyte.remote.Run, just like flyte.run(), so you can monitor it, wait on it, and retrieve its outputs in the same way. See Interact with runs and actions for details.

To control launch settings (name, project, domain, environment variables, labels) use flyte.with_runcontext(...).rerun(...):

        
    
flyte.with_runcontext(
    name="retry-1",
    env_vars={"LOG_LEVEL": "20"},
).rerun("ul56wcvgqrb9vzhzz5l2")

Recover a failed run: re-run only what failed, reusing the actions that succeeded.
Interact with runs and actions: retrieve, monitor, and inspect runs and actions.
Run command options: the full set of flyte run options.