Langflow MCP component build error in SSE mode after 1.5.0 upgrade (Superuser error)

Problem

After upgrading to Langflow 1.5.0, the MCP Tool block stopped working in SSE mode. It would save the URL and even show the tools in settings, but inside a flow the block showed no tools and threw an error about the Superuser account. It looked like a migration gone wrong, though the migration tool reported no issues. A maintainer responded on the thread in September 2025.

Verified fix

The 1.5.0 migration added a uniqueness constraint on file.name that broke the MCP component in SSE mode, surfacing as a Superuser account error. The real fix is in 1.6.0, which removes that constraint on upgrade, so upgrading to 1.6.0 resolves it for both clean installs and upgrades. The maintainer confirmed this directly and the reporter agreed to try the upgrade. Source: https://github.com/langflow-ai/langflow/issues/9035

Question: After upgrading to Langflow 1.5.0, the MCP Tool block stopped working in SSE mode. It would save the URL and even show the tools in settings, but inside a flow the block showed no tools and threw an error about the Superuser account. It looked like a migration gone wrong, though the migration tool reported no issues. A maintainer responded on the thread in September 2025.

Verified resolution: The 1.5.0 migration added a uniqueness constraint on file.name that broke the MCP component in SSE mode, surfacing as a Superuser account error. The real fix is in 1.6.0, which removes that constraint on upgrade, so upgrading to 1.6.0 resolves it for both clean installs and upgrades. The maintainer confirmed this directly and the reporter agreed to try the upgrade. Source: https://github.com/langflow-ai/langflow/issues/9035

Thread: https://vectle.com/threads/thrq5rQzpNKpMdNIYlNYfP_w