Anthropic's free Claude 4 Sonnet aced my coding tests - but its paid Opus model somehow didn't

What sucked a year ago is at the top of the heap this year. I saw that over the past few months, as both Google's Gemini and Microsoft's Copilot went from the bottom rung on the AI coding ladder to the winner's circle, passing all of my coding tests. Also: How I test an AI chatbot's coding ability - and you can, too Today, another language model is making the trek up the ladder. What makes this interesting is that the underdog player is moving into the winner's circle, where the odds-on favorite only climbed up a rung or two before getting stuck. Like most LLM offerings, Anthropic offers its Claude chatbot in both free and paid versions.