Claude 3.5 Sonnet vs. GPT-4o: AI Coding & Agent Showdown

Anthropic's Fable 5.1 shows a 33% improvement on one of its coding benchmarks and a 75% reduction in cache-read pricing. Meanwhile, OpenAI's GPT-5.6 Sol has a lower promotional API price and has led independent coding-agent evaluations. Here's the thing: The public numbers don't definitively say which is better for developers. Fable 5.1 appears well-suited for long, context-heavy agent sessions. What's interesting is that Sol has a substantial price advantage in its listed rates. Anthropic states that Fable 5.1 is their most capable model for coding and agentic tasks. Its per-token price remains unchanged from Fable 5, but the cache-read price is now 25 cents per million tokens, down from one dollar. This 75% price cut means typical workloads could be 25% cheaper, and highly agentic sessions up to 45% cheaper. This matters because coding agents often reuse the same repository context. The bottom line is that the best choice depends on specific developer needs and workload types.