MCP workflow executions now return immediately
The execute_workflow MCP tool now triggers workflows without waiting for completion, returning an execution ID instantly. A circular JSON serialization bug in get_execution was also fixed.
The execute_workflow tool in n8n's MCP integration previously waited for workflows to complete before returning results. This blocking behavior created problems for long-running workflows and contributed to timeout errors.
Now the tool triggers a workflow execution and immediately returns an execution ID with status "started" — no waiting, no timeout. Developers can use the separate get_execution tool to poll for results when needed.
A secondary fix addresses circular reference errors in the get_execution tool. When serialization encountered circular data structures, it would fail. The jsonStringify calls now use replaceCircularRefs to handle these gracefully.
These changes live in the MCP tools layer of the n8n CLI package, affecting how AI assistants and external systems can integrate with n8n workflows.
View Original GitHub Description
Summary
- Making
execute_workflowMCP tool async - now it only triggers an execution without waiting for it to finish - Fixing circular JSON issue in
get_executiontool
Related Linear tickets, Github issues, and Community forum posts
Fixes ADO-4423
Review / Merge checklist
- PR title and summary are descriptive. (conventions) <!-- **Remember, the title automatically goes into the changelog. Use `(no-changelog)` otherwise.** -->
- Docs updated or follow-up ticket created.
- Tests included. <!-- A bug is not considered fixed, unless a test is added to prevent it from happening again. A feature is not complete without tests. -->
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Backport to Beta,Backport to Stable, orBackport to v1(if the PR is an urgent fix that needs to be backported)