I fixed a smolagents bug that confused everyone who hit it (with Sentry watching the whole time)

This is a submission for DEV's Summer Bug Smash: Clear the Lineup powered by Sentry. ...

giovedì 16 luglio 2026 New tab

1,267 words~6 min read

This is a submission for DEV's Summer Bug Smash: Clear the Lineup powered by Sentry.

Project Overview

I picked huggingface/smolagents, the 28k+ star agent framework where agents literally think in Python code. It had a bug open since issue #1108 that anyone combining MCP tools with agent serialization would eventually slam into.

Call agent.to_dict() on a CodeAgent holding MCP tools (or save() or push_to_hub(), same path) and you get this beauty:

ValueError: Tool validation failed for MCPAdaptTool:

I fixed a smolagents bug that confused everyone who hit it (with Sentry watching the whole time)

I fixed a smolagents bug that confused everyone who hit it (with Sentry watching the whole time)

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Related reading

The smolagents bug that made my agent retry the same valid code three times

4 Silent Failures, 2 Undocumented APIs, and a Container That Crashed Because of…

Smash Stories: The Bug That Whispered for Two Weeks Before I Heard It

One line of math froze my AI agent forever. The timeout watched and did nothing.

My agent kept forgetting what it was doing. A scratchpad fixed it.

smolagents Is Powerful Because It Runs Code. That Is Also the Boundary.