Claude Code can run Sonnet as your main model and bring in Opus only for the hard calls: one flag, --advisor opus. Set it up in 4 steps: 1. Launch with: claude --model sonnet --advisor opus 2. Claude decides when to ask Opus: before it commits to a plan, when an error keeps coming back, and before it says it's done. 3. Put the grunt work on Haiku: a subagent file in .claude/agents with model: haiku for searching and reading big files. 4. Give any subagent that tests risky changes isolation: worktree, so it works on its own copy of the repo. /advisor turns it on or off mid-session. It needs the Anthropic API; it isn't on Bedrock or Google Cloud yet. https://t.co/RDx6YSGDg8