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Claude Code sends Anthropic Messages requests, and Prism exposes an Anthropic-compatible /v1/messages endpoint, so you can point the CLI at Prism with environment variables. No gateway is required.

Copy for your agent

If no key exists, ask the workspace owner for an existing PRISM_API_KEY.

Configure

Set these variables in the environment that launches claude:
Use the host without a /v1 suffix. Claude Code appends /v1/messages itself, so a /v1 in ANTHROPIC_BASE_URL produces /v1/v1/messages and a 404. ANTHROPIC_MODEL overrides Claude Code’s built-in Claude model IDs, which Prism does not serve. ANTHROPIC_SMALL_FAST_MODEL covers background requests such as title generation; set it to a Prism model so those requests succeed too.

Verify

You should see PRISM OK. The request appears in your Prism usage once it completes.

Notes

  • Prism accepts both ANTHROPIC_AUTH_TOKEN (Bearer) and ANTHROPIC_API_KEY (x-api-key). Prefer ANTHROPIC_API_KEY if you want to leave your claude.ai login untouched.
  • Messages, streaming, thinking blocks, tool use, structured output, and count_tokens are supported. Prompt-cache hints such as context_management are accepted and ignored.
  • Prism discards request inputs and outputs after processing. See Zero data retention.
Last modified on October 12, 2026