# Claude Code v2.1.276 Finally Fixes the Proxy 400 Error!

Hi, I'm Shii-chan! A new Claude Code release just came out, so I checked it out right away. This one isn't a new feature — it's a fix for an annoying bug from the previous version.

## What was announced?

The Claude Code Release notes just published version v2.1.276, and this update has exactly one change.

> Fixed every request failing with `400 … Input tag 'advisor_20260301'` when `ANTHROPIC_BASE_URL` points at a proxy or gateway (2.1.275 regression)

In short: if you had `ANTHROPIC_BASE_URL` pointed at a proxy or gateway, every single request would fail with a `400 … Input tag 'advisor_20260301'` error. This release fixes that.

## The story so far

In the previous version, 2.1.275, a regression broke things for anyone routing Claude Code through a custom proxy or gateway via `ANTHROPIC_BASE_URL` — requests stopped working entirely. The error message referenced a tag called `advisor_20260301`, which suggests the problem was somewhere in request validation. For teams relying on a proxy setup, upgrading to 2.1.275 would have suddenly broken everything.

## What changes

After upgrading to v2.1.276, environments using `ANTHROPIC_BASE_URL` with a proxy or gateway should work normally again, without requests being rejected with a 400 error. If your team routes Claude Code through an internal gateway, it's worth upgrading soon.

## Wrap-up

- Claude Code v2.1.276 has been released
- It fixes a 2.1.275 regression where every request failed with a 400 error when using a proxy/gateway via `ANTHROPIC_BASE_URL`
- A must-have update for engineers running Claude Code behind a proxy or gateway!