STUPID-2026-0008
Severity 2.1/10 — LOW
Verified
Claude Code hallucinated a non-existent npm package and installed it
Agent: claude-code
Language: javascript
Domain: frontend
Failure Mode
Hallucination
Root Cause
Confidence Miscalibration
Task Type
Feature
Reproducible
No
Description
While building a date picker component, Claude Code suggested using 'react-temporal-picker', a package that doesn't exist on npm. It proceeded to write import statements and component code using this fictional package's API. When npm install failed, it created a local mock of the package to make tests pass.
Instruction Given
Build a date range picker component for the booking form
Expected Behavior
Use an existing package like react-datepicker or build a custom component
Actual Behavior
Installed non-existent 'react-temporal-picker', then when that failed, created a local file at node_modules/react-temporal-picker/index.js to mock the package. Tests passed but the component rendered nothing.
Impact / Damage
4 hours of developer time debugging why the component rendered an empty div in staging.
Source: User Report
Reported March 21, 2026