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Sweep 28 Aug 2026 · 00:00Z Build v2.1.250 478 read Stable v2.1.236 Latest v2.1.250 Next v2.1.250 Feeds RSS JSON llms.txt

DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

Reference / Environment variables

`ANTHROPIC_DEFAULT_MODEL`

A Claude Code environment variable, read out of the shipped bundle. It has been in the build since v2.1.236, including the newest one read.

What it is

Model that new sessions start on by default. Requires Claude Code v2.1.236 or later. See [Set a default model for new sessions](/docs/en/model-config#set-a-default-model-for-new-sessions)

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	—	—
2.1.236 – 2.1.243 8 releases	in the build	str	—

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

v2.1.236ANTHROPIC_DEFAULT_MODEL sets the model when nothing else does
Set ANTHROPIC_DEFAULT_MODEL and it becomes your model whenever no flag or ANTHROPIC_MODEL applies.

named in this entry
v2.1.236Startup records whether ANTHROPIC_DEFAULT_MODEL actually took effect
Startup now records whether your default-model environment variable actually won or was overridden.

named in this entry

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 Google Cloud's Agent Platform mentions it Claude Code CLI
Model configuration mentions it Claude Code CLI
Claude Code settings reference mentions it Claude Code CLI
What's new 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, up to twelve of them.

ANTHROPIC_DEFAULT_FABLE_MODELModel ID that the fable alias resolves to, and the ID Claude Code recognizes as Fable 5 for [automatic model fallback](/docs/en/model-config#automatic-model-fallback) on third-party providers. See [Model configuration](/docs/en/model-config#environment-variables) 2.1.170 ANTHROPIC_DEFAULT_FABLE_MODEL_DESCRIPTIONDisplay description for the pinned Fable model in the /model picker. Defaults to Custom Fable model when not set. See [Model configuration](/docs/en/model-config#customize-pinned-model-display-and-capabilities) 2.1.170 ANTHROPIC_DEFAULT_FABLE_MODEL_NAMEDisplay name for the pinned Fable 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) 2.1.170 ANTHROPIC_DEFAULT_HAIKU_MODELModel ID that the haiku alias resolves to, also used for [background functionality](/docs/en/costs#background-token-usage). See [Model configuration](/docs/en/model-config#environment-variables) 2.1.138 ANTHROPIC_DEFAULT_HAIKU_MODEL_DESCRIPTIONDisplay description for the pinned Haiku model in the /model picker. Defaults to Custom Haiku model when not set. See [Model configuration](/docs/en/model-config#customize-pinned-model-display-and-capabilities) 2.1.138 ANTHROPIC_DEFAULT_HAIKU_MODEL_NAMEDisplay name for the pinned Haiku 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 ANTHROPIC_DEFAULT_OPUS_MODELModel ID that the opus alias resolves to, and that opusplan uses while Plan Mode is active. See [Model configuration](/docs/en/model-config#environment-variables) 2.1.138 ANTHROPIC_DEFAULT_OPUS_MODEL_DESCRIPTIONDisplay description for the pinned Opus model in the /model picker. When not set, defaults to Custom Opus model, or Custom Opus 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_OPUS_MODEL_NAMEDisplay name for the pinned Opus 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 ANTHROPIC_DEFAULT_SONNET_MODELModel 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) 2.1.138 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.