In the final fallback branch of direct API client construction, used when no gateway, Bedrock, or Vertex provider applies, the client config now sets baseURL to ANTHROPIC_BASE_URL when that environment variable is present. This replaces a prior unconditional no-op spread, so ANTHROPIC_BASE_URL is now respected in this fallback path.
Names in the bundleANTHROPIC_BASE_URL
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Added since
A small documentation edit on Claude Code changelog touched a line naming ANTHROPIC_BASE_URL after this was published.
* Fixed every request failing with `400 … Input tag 'advisor_20260301'` when `ANTHROPIC_BASE_URL` points at a proxy or gateway (2.1.275 regression)changelog see the edit
Confirmed since
Anthropic's documentation has since written up ANTHROPIC_BASE_URL, on Claude Code changelog.
* Fixed every turn failing with HTTP 400 on third-party Anthropic-compatible endpoints (`ANTHROPIC_BASE_URL`) since 2.1.265: a regex in the Artifact tool's input schema that those endpoints rejectchangelog see the edit
One source agreesOne thing we can check says the same as this entry.
Anthropic's documentation agrees
Anthropic's documentation has since written up ANTHROPIC_BASE_URL, on Claude Code changelog.