{"name":"ANTHROPIC_SMALL_FAST_MODEL","slug":"anthropic-small-fast-model","family":"env","title":"Environment variables","noun":"environment variable","description":"\\[DEPRECATED] Name of [Haiku-class model for background tasks](\/docs\/en\/costs)","description_source":"docs","described_by":{"doc":"claude-code\/env-vars","title":"Environment variables"},"presence":{"first_seen":"2.1.138","removed_in":null,"in_current_build":true,"newest_mined":"2.1.308","builds":149,"mined_builds":149,"first_cited":{"version":"2.1.261","released_at":"2026-09-04 17:49:34","spans":1}},"aliases":[],"entries":[{"version":"2.1.296","anchor":"prompt-hooks-always-use-the-default-small-model","heading":"Prompt hooks no longer pick the main model on gateway setups","line":"Prompt hooks now use their own configured model or the default small model, without a gateway special case","released_at":"2026-10-09 16:58:10","reason":"found in this entry's text"},{"version":"2.1.295","anchor":"gateway-provider-falls-back-to-a-gateway-default-model-when","heading":"Gateway users without a small model set fall back to the default model","line":"With a gateway provider and no Haiku-class model set, hooks use the main model and failed side requests retry on the default","released_at":"2026-10-08 18:22:58","reason":"found in this entry's text"},{"version":"2.1.261","anchor":"bedrock-count-tokens-fallback-no-longer-uses-haiku-probe","heading":"Bedrock count_tokens fallback no longer uses Haiku probe","line":"Bedrock token counting fallback now uses your own model instead of a Haiku probe.","released_at":"2026-09-04 17:49:34","reason":"found in this entry's text, named in this entry"},{"version":"2.1.227","anchor":"bedrock-and-vertex-share-one-stale-model-check","heading":"Bedrock and Vertex share one stale-model check","line":"Bedrock and Vertex now share one check for outdated pinned model variables.","released_at":"2026-08-10 20:56:57","reason":"found in this entry's text"},{"version":"0.2.62","anchor":"model-configuration-updates","heading":"Model Configuration Updates","line":null,"released_at":"2025-04-04 02:56:58","reason":"found in this entry's text"}],"entries_total":5,"docs":[{"source":"claude-code","path":"env-vars","title":"Environment variables","documented":true},{"source":"claude-code","path":"amazon-bedrock","title":"Claude Code on Amazon Bedrock","documented":false},{"source":"claude-code","path":"model-config","title":"Model configuration","documented":false},{"source":"claude-code","path":"prompt-caching","title":"How Claude Code uses prompt caching","documented":false}],"docs_total":4,"gates":[],"related":[{"name":"ANTHROPIC_SMALL_FAST_MODEL_AWS_REGION","slug":"anthropic-small-fast-model-aws-region","description":"Override AWS region for the Haiku-class model when using Amazon Bedrock or Amazon Bedrock Mantle. On Amazon Bedrock, this only takes effect when `ANTHROPIC_DEFAULT_HAIKU_MODEL` or the deprecated `ANTHROPIC_SMALL_FAST_MODEL` is also set, since Amazon Bedrock otherwise runs background tasks on the [default Sonnet model or the primary model](\/docs\/en\/amazon-bedrock#4-pin-model-versions) in the session region"}],"url":"https:\/\/changelogs.core-directive.com\/reference\/env\/anthropic-small-fast-model","family_url":"https:\/\/changelogs.core-directive.com\/reference\/env.json"}