Unclear What the check now does for a Haiku model name is not known.
When you use Claude through a third-party provider, Claude Code runs a check that sets up which model counts as the Sonnet default. That check used to stop straight away for claude-sonnet-4-6, claude-sonnet-4-5 and any model name starting with claude-haiku-. It now stops early only for the two Sonnet names.
Haiku model names now carry on into the part of the check that reads ANTHROPIC_DEFAULT_SONNET_MODEL and CLAUDE_CODE_3P_PROBE_WROTE_SONNET_DEFAULT.
This matters if you use a third-party provider and pin model names, especially Haiku ones.
Where `opus` or `sonnet` resolves to an older model, newer models are available by selecting the full model name explicitly or setting `ANTHROPIC_DEFAULT_OPUS_MODEL` or `ANTHROPIC_DEFAULT_SONNET_MODEL`.see the edit
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Opus 4.6 and Sonnet 4.6 reach the 1M window when you append `[1m]` to the deployment name in `ANTHROPIC_DEFAULT_OPUS_MODEL` or `ANTHROPIC_DEFAULT_SONNET_MODEL`, as [Pin models for third-party deployments](/docs/en/model-config#pin-models-f…microsoft-foundry see the edit
What the check now does for a Haiku model name is not known.
ANTHROPIC_DEFAULT_SONNET_MODEL on Model configuration