The sneaky move that I hate most is when Claude (and does seem to mostly be a Claude-ism I haven’t encountered on GPT Codex or GLM) is when dealing with an external data source (API, locally polling hardware, etc) as a “helpful” fallback on failures it returns fake data in the shape of the expected output so that the rest of the code “works”.

Latest example is when I recently vibe coded a little Python MQTT client for a UPS connected to a spare Raspberry Pi to use with Home Assistant, and with a just few turns back and forth I got this extremely cool bespoke tool and felt really fun.

So I spent a while customizing how the data displayed on my Home Assistant dashboard and noticed every single data point was unchanging. It took a while to realize because the available data points wouldn’t be expected to change a whole lot on a fully charged UPS but the voltage and current staying at the exact same value to a decimal place for three hours raised my suspicions.

After reading the code I discovered it had just used one of the sample command line outputs from the UPS tool I gave it to write the CLI parsing logic. When an exception occurred in the parser function it instead returned the sample data so the MQTT portion of the script could still “work”.

Tbf Claude did eventually get it over the finish line once I clarified that yes, using real data from the actual UPS was in fact an important requirement for me in a real time UPS monitoring dashboard…