Date: September 16th, 2026 8:07 PM Author: Beta corn cake
How much does context rot cost on agentic coding tasks? We prefilled 250k–500k tokens of context and ran GPT-5.6 Sol and Claude Opus 5 on terminal-bench tasks to find out.
Sol performance drops significantly at longer contexts, even when the context is completely unrelated to the task. Opus 5 holds flat on unrelated context but degrades when the context is related.