What causes TASK_GRAPH_CYCLE_DETECTED?

Task A is set as a predecessor of Task B, and Task B (or a chain from B) is set as a predecessor of Task A, creating a loop. A refactoring of task dependencies introduced a cycle by adding a new predecessor link without checking the full graph. Programmatically generated task dependency configurations contain a logical error that creates a cycle

How do I fix TASK_GRAPH_CYCLE_DETECTED?

Step 1: Map out the full task dependency graph using SHOW TASKS and CURRENT_TASK_GRAPHS, or query TASK_HISTORY in the Snowflake ACCOUNT_USAGE schema.. Step 2: Identify the cycle by tracing predecessor chains — look for any task that eventually lists a descendant as its own predecessor.. Step 3: Break the cycle by removing or rerouting the dependency that creates the loop. Use ALTER TASK REMOVE AFTER to detach a predecessor.. Step 4: After fixing the dependency, resume the root task with ALTER TASK ... RESUME and verify the graph runs successfully with EXECUTE TASK.

High severityconfiguration

Power BI Refresh Error:
TASK_GRAPH_CYCLE_DETECTED

What does this error mean?

Snowflake rejected a task dependency configuration because the defined predecessor relationships form a circular dependency, violating the requirement that a task graph must be a Directed Acyclic Graph.

Common causes

1Task A is set as a predecessor of Task B, and Task B (or a chain from B) is set as a predecessor of Task A, creating a loop
2A refactoring of task dependencies introduced a cycle by adding a new predecessor link without checking the full graph
3Programmatically generated task dependency configurations contain a logical error that creates a cycle

How to fix it

1Step 1: Map out the full task dependency graph using SHOW TASKS and CURRENT_TASK_GRAPHS, or query TASK_HISTORY in the Snowflake ACCOUNT_USAGE schema.
2Step 2: Identify the cycle by tracing predecessor chains — look for any task that eventually lists a descendant as its own predecessor.
3Step 3: Break the cycle by removing or rerouting the dependency that creates the loop. Use ALTER TASK REMOVE AFTER to detach a predecessor.
4Step 4: After fixing the dependency, resume the root task with ALTER TASK ... RESUME and verify the graph runs successfully with EXECUTE TASK.

Frequently asked questions

Does Snowflake detect cycles at task creation or at runtime?

Snowflake validates the DAG structure when you attempt to resume the root task. A cycle will prevent the root task from being resumed and will produce the cycle detection error at that point.

Can I have cross-database task dependencies?

No. Snowflake task graphs must be contained within a single database. Cross-database predecessor relationships are not supported.