{"version":"2.1.284","anchor":"sonnet-55-claude-sonnet-5-5-added-and-made-the-default-s","canonical_anchor":"sonnet-55-claude-sonnet-5-5-added-and-made-the-default-s","heading":"Sonnet 5.5 becomes the default Sonnet model, with Sonnet 5 kept in the picker","tier":"use","area":"Models","url":"https:\/\/changelogs.core-directive.com\/v\/2.1.284\/e\/sonnet-55-claude-sonnet-5-5-added-and-made-the-default-s","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.284","markdown":"### Sonnet 5.5 becomes the default Sonnet model, with Sonnet 5 kept in the picker\n\nThe sonnet alias now means Sonnet 5.5 (claude-sonnet-5-5) on the Anthropic API, Sonnet 5 stays pickable, and refusal handling now covers Sonnet\n\n**Unclear.** Model settings sent from the server may override these defaults.\n\n**What**\n\nA new model, Sonnet 5.5 (`claude-sonnet-5-5`, display name \"Sonnet 5.5\", 1M context window), is added and becomes the default for the `sonnet` family when you use Anthropic's own API. A context window is how much text the model can hold at once.\n\n- The `sonnet` alias, and `\/model sonnet`, now resolve to `claude-sonnet-5-5` instead of `claude-sonnet-5`. It is also listed as the latest Sonnet.\n\n- A short name `sonnet-5-5` maps to `claude-sonnet-5-5`, checked ahead of `sonnet-5` so the new ID is no longer treated as Sonnet 5. It is added to the known-models list and gets its own Vertex region environment variable.\n\n- Other providers keep their own Sonnet defaults: Bedrock, Vertex, Foundry and Mantle stay on `claude-sonnet-4-5`, and `anthropic_aws` and gateway stay on `claude-sonnet-4-6`.\n\n- The `\/model` picker gains a row labelled \"Sonnet 5 \u00b7 Previous Sonnet version\" when Sonnet 5 is available.\n\n- Internal model names move on: the main Opus and Sonnet IDs are now `claude-opus-5-5` and `claude-sonnet-5-5` (\"Claude Sonnet 5.5\"), the previous ones are `claude-opus-5` and `claude-sonnet-5`, and the separate \"next\" entries are gone.\n\n- Refusal fallback: when a Sonnet 5.5 session (`claude-sonnet-5-5` or `claude-sonnet-5-5[1m]`) has a request refused in the cyber or frontier_llm category, Claude Code falls back to `claude-sonnet-5`. There is no fallback for bio. Before, Sonnet 5.5 would have used the default list, which sends bio and frontier_llm to `claude-opus-5` and cyber to `claude-opus-4-8`.\n\n- Safeguard notices: the \"You may be seeing this for the first time\u2026\" explanation, shown when safeguards flag a message, used to appear only for `claude-opus-5-5`. It now also appears for any Sonnet model in the cyber category, reading \"on a Sonnet model\". Sonnet also gets the frontier_llm recovery text (\"is answering instead\" \/ \"Edit and retry\"). The notices now come from a per-family table, and the Opus wording is built the same way instead of being fixed text.\n\n**Why**\n\nIf you pick `sonnet` on the Anthropic API, you move to a new model without changing anything, and you can still choose Sonnet 5 from the picker. Sonnet users who hit a safeguard refusal now get an explanation and a fallback route instead of a bare refusal notice.\n\n- Area: Models\n- Names: `sonnet-5-5`, `claude-sonnet-5-5`, `sonnet`\n- Tier: Use it now\n- Useful: 5\/5\n- Signal: 4\/5"}