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Claude Code v2.1.284 ·

Model aliases like opus now pick the first matching model in a configured list

With a configured model list, opus, sonnet and haiku now map to the first model of that family in the list, not the canonical claude- ID

You'll notice Improvements
JSON All of v2.1.284
You'll noticeTier: how much it should matter to you
2Useful: my rating, 1 to 5
1Signal: worth watching, 1 to 5
ModelsArea: what it touches
ImprovementsKind: in v2.1.284,
ImprovementsSection of the release

Unclear It is not clear where the configured model list comes from or which features use this lookup.

What

When Claude Code has a configured list of models, it turns the aliases opus, sonnet and haiku into a model ID from that list. Each alias now maps to the first entry of that family in the list.

Before, Claude Code preferred the canonical ID of the family, such as a claude- name or a dated ID, and only fell back to other entries when no canonical one was present.

Why

If you use a custom model list, for example through a gateway, the order of the list now decides which model an alias like opus uses. Check that the model you want comes first in its family.

Read from
Names in the bundleopussonnethaiku
Since it was published

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.

Added since A small documentation edit on Claude Code on Amazon Bedrock touched a line naming haiku after this was published. Entries with the `anthropic.` prefix are added as custom picker options, and the ones that match the Mantle format are routed to Mantle. Replace `anthropic.claude-haiku-4-5` with the model ID your account has been granted. See [Restrict mo… amazon-bedrock see the edit
Confirmed since Anthropic's documentation has since written up haiku, on Agents. - `"claude-haiku-4-5"` api/beta/agents see the edit
Added since A small documentation edit on Model configuration touched a line naming opus after this was published. When you set an `ANTHROPIC_DEFAULT_*_MODEL` variable, the `/model` picker shows one row for that model in place of the family's built-in rows, including any 1M context rows. To reach the 1M window without adding the suffix to that variable… model-config see the edit
Confirmed since Anthropic's documentation has since written up sonnet, on Error reference. Model "Sonnet5" is not a recognized model id. Did you mean 'claude-sonnet-5'? errors see the edit
Added since A small documentation edit on Model configuration touched a line naming sonnet after this was published. Administrators can use `availableModels` in [managed or policy settings](/docs/en/managed-settings) to restrict which models users can select. Entries match a model family such as `sonnet`, a version prefix such as `claude-sonnet-4-5`, or … model-config see the edit
Confirmed since Anthropic's documentation has since written up opus, on structured-outputs. "model": "claude-opus-5-5", build-with-claude/structured-outputs see the edit
How sure we are
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubtIt is not clear where the configured model list comes from or which features use this lookup.
Anthropic's documentation agreesAnthropic's documentation has since written up opus, on structured-outputs.

See this entry in the whole of v2.1.284 →

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