{"version":"2.1.170","anchor":"fable-5-environment-variables-for-custom-providers","canonical_anchor":"fable-5-environment-variables-for-custom-providers","heading":"Fable 5 Environment Variables for Custom Providers","tier":null,"area":null,"scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.170\/e\/fable-5-environment-variables-for-custom-providers","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.170","markdown":"### Fable 5 Environment Variables for Custom Providers\n\n**What**\n\nFour new environment variables let BYOC (Bring Your Own Claude) and API-gateway deployments point Claude Code at a custom Fable 5 endpoint.\n\n**Usage**\n\n`export ANTHROPIC_DEFAULT_FABLE_MODEL=my-fable-5-endpoint export ANTHROPIC_DEFAULT_FABLE_MODEL_NAME=\"My Fable 5\" export ANTHROPIC_DEFAULT_FABLE_MODEL_DESCRIPTION=\"Custom Fable 5 model\" export ANTHROPIC_DEFAULT_FABLE_MODEL_SUPPORTED_CAPABILITIES=vision,tools` **Details** - `ANTHROPIC_DEFAULT_FABLE_MODEL` \u2014 custom Fable 5 model ID (enables the alias and fallback logic even on non-firstParty providers) - `ANTHROPIC_DEFAULT_FABLE_MODEL_NAME` \u2014 display name shown in the model picker - `ANTHROPIC_DEFAULT_FABLE_MODEL_DESCRIPTION` \u2014 description shown alongside the model - `ANTHROPIC_DEFAULT_FABLE_MODEL_SUPPORTED_CAPABILITIES` \u2014 capabilities string for the model - `VERTEX_REGION_CLAUDE_FABLE_5` \u2014 region override for Fable 5 on Vertex AI (same pattern as the existing `VERTEX_REGION_CLAUDE_*` vars) - When `ANTHROPIC_DEFAULT_FABLE_MODEL` is set, Claude Code shows a \"Custom Fable model\" entry in the picker in place of the default Fable 5 entry (on non-firstParty providers) - A new fallback hint is also surfaced for providers where these vars are absent: \"To enable automatic fallback on this provider, set `ANTHROPIC_DEFAULT_FABLE_MODEL` to your Fable 5 model ID and `ANTHROPIC_DEFAULT_OPUS_MODEL` to your Opus 4.8 model ID.\" **Evidence** Env var registration (search for `\"ANTHROPIC_DEFAULT_FABLE_MODEL\"`) and custom-model picker entry (search for `\"Custom Fable model\"`)"}