Cost
5 articles
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AgentsSonnet 5.5 Scored Worse at Max Effort
Claude Sonnet 5.5 scored 52.1% on FrontierCode at xhigh effort and 46.2% at max. Anthropic's footnote says that at max the model more often ran Claude Code's code-review skill, fanning out to subagents, which caused timeouts and out-of-scope edits. Effort now changes behavior, not just thinking depth: pin it per workload, sweep levels on your own eval, and cap fan-out.
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LLMOpus 5.5 Is 40% Cheaper Because the Default Effort Dropped
Claude Opus 5.5 and GPT-6 Sol both launched on 22 September as cheaper models. Anthropic says Opus 5.5 costs 40% less than Opus 5 at default settings, but a request that omits effort now runs at medium instead of high, and at the same effort label the model thinks more per turn. Set effort explicitly, log it, and sweep two levels on your own tasks.
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EngineeringOpenAI Explains Cache Misses. Its Own Agent Still Causes One.
OpenAI's Prompt Cache Diagnostics, GA since 8 September, label every Responses API cache miss with one of nine reasons. One of them, reasoning_effort_changed, already has a fix in GPT-6 Astra's configuration_update, and the Codex CLI still changes effort the old way. On Astra a cache write costs $12.50 per million tokens against $1 for a read, so a miss caused by your harness is now a surcharge, not a lost discount.
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AgentsOne Wasted File Read, Billed 470 Times
Sonar instrumented 18 pull requests written by a coding agent on its own codebase and published the traces on 1 September. One 800-line PR was billed 156 million tokens for 289,000 tokens of output. 152.8 million of those were cache reads, which means the cost of a file read is set by how early in the session the agent made it.
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ModelsUS Models Fell From 70 to 30 Percent of OpenRouter Traffic in a Year
American models fell from 70 percent of OpenRouter token traffic to about 30 percent in a year, while Chinese open-weight models took the rest. It is a cost story, not a quality story, and real companies are already routing production workloads across the 60 to 90 percent price gap.