The whole hunk
from line 11, old and new numbered
/
lines
from line 11
1111## Models
1212
1313```text wrap
14For complex agentic coding and enterprise work: Claude Opus 5: claude-opus-5
14Recommended default for most work, including complex agentic coding: Claude Opus 5: claude-opus-5
15Step up for the hardest long-running agentic and research tasks, at 2x Claude Opus 5 pricing: Claude Fable 5.1: claude-fable-5-1
1516Previous Opus model: Claude Opus 4.8: claude-opus-4-8
1617Smart model: Claude Sonnet 5: claude-sonnet-5
1718For fast, cost-effective tasks: Claude Haiku 4.5: claude-haiku-4-5-20251001
from line 621
620621* `any` tells Claude that it must use one of the provided tools.
621622* `tool` forces Claude to always use a particular tool.
622623* `none` prevents Claude from using any tools.
624
625On Claude Fable 5.1 and Claude Mythos 5.1, `any` and `tool` return a 400 error. Leave `tool_choice` at `auto` and set `"strict": true` on the tool definition to guarantee that any call Claude makes matches the tool's `input_schema`. See [Strict tool use](https://platform.claude.com/docs/en/agents-and-tools/tool-use/strict-tool-use).
623626
624627### JSON output
625628