Model configuration changedmodel-config
Nearest release: v2.1.283, published 5 hours before upstream edited the page. Shown because the two are within 24 hours of each other. Nothing here says the release caused the edit.
Upstream edited this page at 26 Sep 2026 00:33 UTC, give or take a minute or two: the time comes from Anthropic’s own sitemap rather than from a commit. This site recorded the change at 26 Sep 2026 00:37 UTC.
Upstream edited
Recorded here
Lines+11added
Lines−7removed
From line
622
where the diff opens
First seen
14 Aug 2026
this site's first read of the page
Recorded edits42to this page, all time
The whole hunk
from line 622, old and new numbered
/
from line 622
622622
623623The effort scale is calibrated per model, so the same level name does not represent the same underlying value across models.
624624
625Opus 5.5 [defaults to `medium`](#adjust-effort-level), one level below Opus 5's default of `high`. In Anthropic's testing, Opus 5.5 at `medium` matches or exceeds Opus 5 at `high` on coding and knowledge-work evaluations. At a given level, Opus 5.5 tends to think more per turn than Opus 5. When you move from Opus 5 to Opus 5.5, start at `medium` rather than carrying over the level you used on Opus 5. To test levels against your own work, see [Calibrate effort](https://platform.claude.com/docs/en/build-with-claude/prompt-engineering/prompting-claude-opus-5-5#calibrate-effort) in the Opus 5.5 prompting guide.
626
625627#### Use ultrathink for one-off deep reasoning
626628
627629Include `ultrathink` anywhere in your prompt to request deeper reasoning on that turn without changing your session effort setting. Claude Code recognizes the keyword and adds an in-context instruction. The effort level sent to the API is unchanged. Claude Code passes other phrases such as "think", "think hard", and "think more" through as ordinary prompt text and doesn't recognize them as keywords.
from line 809
807809| `ANTHROPIC_DEFAULT_HAIKU_MODEL` | The model to use for `haiku`, or [background functionality](/docs/en/costs#background-token-usage) |
808810| `CLAUDE_CODE_SUBAGENT_MODEL` | The default model for [subagents](/docs/en/sub-agents#choose-a-model), [agent team](/docs/en/agent-teams#specify-teammates-and-models) teammates, and [workflow](/docs/en/workflows) agents that aren't assigned a model another way. Accepts an alias such as `haiku` or a full model name. A per-invocation model or a definition's `model` field, including `inherit`, takes precedence. To change that, set [`CLAUDE_CODE_SUBAGENT_MODEL_FORCE`](/docs/en/sub-agents#run-every-subagent-on-one-model) |
809811
812On third-party providers, [Customize pinned model display and capabilities](#customize-pinned-model-display-and-capabilities) describes what a pinned model's row in the `/model` picker shows.
813
810814Note: `ANTHROPIC_SMALL_FAST_MODEL` is deprecated in favor of
811815`ANTHROPIC_DEFAULT_HAIKU_MODEL`.
812816
from line 935
931935
932936Claude Code automatically uses [prompt caching](/docs/en/prompt-caching) to optimize performance and reduce costs. You can disable prompt caching globally or for specific model tiers:
933937
934| Environment variable | Description |
935| ------------------------------- | ------------------------------------------------------------------------------------------------- |
936| `DISABLE_PROMPT_CACHING` | Set to `1` to disable prompt caching for all models. Takes precedence over the per-model settings |
937| `DISABLE_PROMPT_CACHING_HAIKU` | Set to `1` to disable prompt caching for Haiku models only |
938| `DISABLE_PROMPT_CACHING_SONNET` | Set to `1` to disable prompt caching for Sonnet models only |
939| `DISABLE_PROMPT_CACHING_OPUS` | Set to `1` to disable prompt caching for Opus models only |
940| `DISABLE_PROMPT_CACHING_FABLE` | Set to `1` to disable prompt caching for Fable models only |
938| Environment variable | Description |
939| ------------------------------- | ------------------------------------------------------------------------------------------------------------- |
940| `DISABLE_PROMPT_CACHING` | Set to `1` to disable prompt caching for all models. Takes precedence over the per-model settings |
941| `DISABLE_PROMPT_CACHING_HAIKU` | Set to `1` to disable prompt caching for the [default Haiku model](/docs/en/prompt-caching#disable-prompt-caching) |
942| `DISABLE_PROMPT_CACHING_SONNET` | Set to `1` to disable prompt caching for Sonnet models only |
943| `DISABLE_PROMPT_CACHING_OPUS` | Set to `1` to disable prompt caching for Opus models only |
944| `DISABLE_PROMPT_CACHING_FABLE` | Set to `1` to disable prompt caching for Fable models only |
941945
942946To choose the cache TTL for the main conversation and for subagents separately, see [choose the TTL yourself](/docs/en/prompt-caching#choose-the-ttl-yourself). For what triggers a cache miss, see [How Claude Code uses prompt caching](/docs/en/prompt-caching).
943947
No line in this hunk matches that.