ANTHROPIC_DEFAULT_SONNET_MODEL
A Claude Code environment variable, read out of the shipped bundle. It has been in the build since v2.1.138, including the newest one read.
What it is
Model ID that the sonnet alias resolves to, and that opusplan uses when Plan Mode is not active. See [Model configuration](/docs/en/model-config#environment-variables)
Anthropic's own wording. Read off Environment variables, captured 2026-08-28.
Presence across releases
| Releases | Reading | Declared type | Default |
|---|---|---|---|
| 2.1.245 – 2.1.250 5 releases | never mined | — | — |
| 2.1.160 – 2.1.243 75 releases | in the build | str | — |
| 2.1.138 – 2.1.159 20 releases | in the build | — | — |
A row reading never mined is a release with no archived bundle behind it. Nothing was read out of it, so nothing here says whether the name was in it. A declared type or a default is only ever what that release's own bundle stated.
Changelog entries naming it
No changelog entry here has ever named it. That is a statement about what has been written, not about the name: it has been in the build since v2.1.138 without anybody writing a line about it.
Documentation pages
- Environment variables reference table Claude Code CLI
- Claude Code on Amazon Bedrock mentions it Claude Code CLI
- Claude Code changelog mentions it Claude Code CLI
- Claude Code on Claude Platform on AWS mentions it Claude Code CLI
- Claude Code on Google Cloud's Agent Platform mentions it Claude Code CLI
- Claude Code on Microsoft Foundry mentions it Claude Code CLI
- Model configuration mentions it Claude Code CLI
- Enterprise deployment overview mentions it Claude Code CLI
A reference table page is one whose own table defines this name, and it is where the description above came from. A page that mentions it carries the name somewhere in its text and may say nothing about it at all. Every page carrying it.
Names beside it
Every environment variable in the inventory starting anthropic_default_sonnet, up to twelve of them.
ANTHROPIC_DEFAULT_SONNET_MODEL_DESCRIPTIONDisplay description for the pinned Sonnet model in the /model picker. When not set, defaults to Custom Sonnet model, or Custom Sonnet model (1M context) if the pinned model ID has the [1m] suffix and CLAUDE_CODE_DISABLE_1M_CONTEXT isn't turned on. See [Model configuration](/docs/en/model-config#customize-pinned-model-display-and-capabilities) 2.1.138
ANTHROPIC_DEFAULT_SONNET_MODEL_NAMEDisplay name for the pinned Sonnet model in the /model picker. Defaults to the model ID when not set. See [Model configuration](/docs/en/model-config#customize-pinned-model-display-and-capabilities) 2.1.138
Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the environment variable does. All environment variables.