# \`BaseRestartWorkChain\`: upcoming changes in behavior for unhandled failures **URL:** \ **Category:** Developer\ **Created:** [December 8, 2025, 10:51pm UTC](https://aiida.discourse.group/t/baserestartworkchain-upcoming-changes-in-behavior-for-unhandled-failures/697 "2025-12-08T22:51:52Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![mbercx](https://yyz2.discourse-cdn.com/free1/user_avatar/aiida.discourse.group/mbercx/32/345_2.png) [@mbercx](https://aiida.discourse.group/u/mbercx)\ **Post date:** [December 8, 2025, 10:51pm UTC](https://aiida.discourse.group/t/baserestartworkchain-upcoming-changes-in-behavior-for-unhandled-failures/697/1 "2025-12-08T22:51:52Z")
Hi all, We’re very close to merging the following PR, which will be a part of the upcoming v2.8.0 release: > > > Currently, the \`BaseRestartWorkChain\` has hardcoded behavior for unhandled failu…res: it restarts once, then aborts on the second consecutive failure with the \`ERROR\_SECOND\_CONSECUTIVE\_UNHANDLED\_FAILURE\` exit code. This approach lacks flexibility for different use cases where users might want immediate abort or allow for human evaluation through pausing. > > This commit introduces a new optional input \`on\_unhandled\_failure\` that allows users to configure how the work chain handles unhandled failures. The available options are: > > \- \`abort\` (default): Abort immediately with ERROR\_UNHANDLED\_FAILURE > \- \`pause\`: Pause the work chain for user inspection > \- \`restart\_once\`: Restart once, then abort if it fails again (similar to old behavior) > \- \`restart\_and\_pause\`: Restart once, then pause if it still fails > > BREAKING: The default behavior is set to \`abort\`, which is the most conservative option. In many cases this is the desired behavior, since doing a restart without changing the inputs will typically fail again, wasting resources. Users who want the old "restart once" behavior can explicitly set \`on\_unhandled\_failure='restart\_once'\`. > > BREAKING: The exit code \`ERROR\_SECOND\_CONSECUTIVE\_UNHANDLED\_FAILURE\` has been renamed to \`ERROR\_UNHANDLED\_FAILURE\` to better reflect the new flexible behavior where failure doesn't necessarily mean "second consecutive" anymore. which makes some changes in the behavior of the `BaseRestartWorkChain` when dealing with unhandled failures (see the commit message below for reference). This might affect your usage in two ways: 1. By default the `BaseRestartWorkChain` will now immediately abort when encountering an unhandled failure. In the majority of cases, this is desirable: rerunning with the same inputs typically leads to another failure and loss of resources. In case you prefer the old behavior, you can explicitly set `on_unhandled_failure='restart_once'`. 2. The exit code `ERROR_SECOND_CONSECUTIVE_UNHANDLED_FAILURE` has been renamed to `ERROR_UNHANDLED_FAILURE`. This might affect code that checks for this exit code to e.g. decide on the next step in a workflow. I’ve searched GitHub for this exit code, and could not find such usage, save for tests in packages we maintain. We apologise in case these changes cause you any inconvenience. Happy computing! 🚀 * * * ### Commit message Currently, the `BaseRestartWorkChain` has hardcoded behavior for unhandled failures: it restarts once, then aborts on the second consecutive failure with the `ERROR_SECOND_CONSECUTIVE_UNHANDLED_FAILURE` exit code. This approach lacks flexibility for different use cases where users might want immediate abort or allow for human evaluation through pausing. This commit introduces a new optional input `on_unhandled_failure` that allows users to configure how the work chain handles unhandled failures. The available options are: - `abort` (default): Abort immediately with `ERROR_UNHANDLED_FAILURE` - `pause`: Pause the work chain for user inspection - `restart_once`: Restart once, then abort if it fails again (similar to old behavior) - `restart_and_pause`: Restart once, then pause if it still fails BREAKING: The default behavior is set to `abort`, which is the most conservative option. In many cases this is the desired behavior, since doing a restart without changing the inputs will typically fail again, wasting resources. Users who want the old “restart once” behavior can explicitly set `on_unhandled_failure='restart_once'`. BREAKING: The exit code `ERROR_SECOND_CONSECUTIVE_UNHANDLED_FAILURE` has been renamed to `ERROR_UNHANDLED_FAILURE` to better reflect the new flexible behavior where failure doesn’t necessarily mean “second consecutive” anymore.