Synchronous Callout in Trigger #274
Description
Record-triggered flows that run synchronously (i.e., in the "after the record is saved" path that executes immediately) are not allowed to include elements that perform external callouts, such as HTTP Callout actions or actions that invoke external services synchronously.
The Flow Builder UI enforces this restriction by default, preventing users from adding synchronous callout-capable elements directly in the immediate execution path of a record-triggered flow. Attempting to do so typically results in validation errors or blocked configuration in the builder.
However, flows created or modified outside the standard UI—such as through the Metadata API, deployment tools, source control merges, manual XML edits, or certain package installations—can sometimes include these invalid configurations.
This rule in Lightning Flow Scanner detects record-triggered flows containing synchronous callouts in paths that run immediately (synchronous context), which would cause runtime failures, transaction rollbacks, or platform exceptions (e.g., "You have uncommitted work pending" or callout-specific governor limit violations in mixed DML contexts).