{"version":"2.1.237","anchor":"system-prompt-caching-now-requires-a-recognised-endpoint","canonical_anchor":"system-prompt-caching-now-requires-a-recognised-endpoint","heading":"System prompt caching now requires a recognised endpoint","tier":"notice","area":"Prompt Caching","scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.237\/e\/system-prompt-caching-now-requires-a-recognised-endpoint","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.237","markdown":"### System prompt caching now requires a recognised endpoint\n\nIf you point Claude at a proxy or custom gateway, the system prompt is no longer cached.\n\n**What**\n\nThe check deciding whether the system prompt block may be marked cacheable used to only require that experimental betas were not disabled. It now also requires a known provider and endpoint: Bedrock, Vertex and Mantle qualify only when `ANTHROPIC_BEDROCK_BASE_URL`, `ANTHROPIC_VERTEX_BASE_URL` and `ANTHROPIC_BEDROCK_MANTLE_BASE_URL` are unset, and Foundry only when `ANTHROPIC_FOUNDRY_BASE_URL` is unset or its hostname ends in `.services.ai.azure.com`. Behind a proxy or custom gateway, the system block stops being cached.\n\n**Details**\n\n- First-party and Anthropic-on-AWS paths still have to pass the existing beta and base-URL checks.\n- No feature flag; the outcome is decided entirely by the provider and those environment variables, and it is live for everyone on this build.\n\n**Evidence**\n\n`.services.ai.azure.com`\n\n- Area: Prompt Caching\n- Names: `ANTHROPIC_BEDROCK_BASE_URL`, `ANTHROPIC_VERTEX_BASE_URL`, `ANTHROPIC_BEDROCK_MANTLE_BASE_URL`, `ANTHROPIC_FOUNDRY_BASE_URL`\n- Tier: You'll notice\n- Useful: 4\/5\n- Signal: 3\/5"}