Model Routing

Claude Code Reroutes Your Pinned Sonnet ARN to Opus 4.8

Claude Code 2.1.312 (27 Oct 2026) extends its post-refusal model switch to model names it doesn't recognise, so a flagged session on a Bedrock application inference profile ARN now moves to a region-prefixed Opus 4.8 ID (Opus 5 for bio and frontier_llm) for the rest of the session, at 2.5x Sonnet's list price if the profile fronted Sonnet 5.5. On 2.1.311 the refusal stood. The same release cuts the ARN's first request from 27,204 to 5,917 characters of system prompt and 46,609 to 30,326 characters of tool definitions. Tested with 34 headless runs against a local fake Bedrock and Anthropic endpoint; modelOverrides, availableModels, ANTHROPIC_DEFAULT_OPUS_MODEL, switchModelsOnFlag and the two CLAUDE_CODE_DISABLE_REFUSAL_* variables are the controls that worked, ANTHROPIC_DEFAULT_SONNET_MODEL is not.