MB002: multiple-definitions

🚨 Breaking ❌ Not Fixable

MB002: Multiple cells define the same variable.

What it does

Analyzes the dependency graph to detect variables that are defined in more than one cell, which violates marimo's fundamental constraint for reactive execution.

Why is this bad?

Multiple definitions prevent marimo from:

• Determining the correct execution order
• Creating a reliable dependency graph
• Running notebooks as scripts
• Providing consistent reactive updates

This is a breaking error because it makes the notebook non-executable.

Examples

Problematic:

# Cell 1
x = 1

# Cell 2
x = 2  # Error: x defined in multiple cells

Solution:

# Cell 1
x = 1

# Cell 2
y = 2  # Use different variable name

References

• Multiple Definitions Guide
• Understanding Errors