v2.1.276 Claude Code Release Notes

Sep 18, 2026

Claude's Analysisby Sonnet 5

Emergency same-day fix: v2.1.275 broke every request for anyone routing through a custom API proxy or gateway with a 400 error.

Change

Total Changes (vs Average)

0.1×

Version Type

Patch

Release Focus

Bug Fix

Days Since Prior Release

Release # This Month

#18 of 18

Bug Fix Ratio

100%

Post-Release Edits

—

Change Category

Key Themes

1Proxy/Gateway Hotfix

May Help If You've Noticed

Every request failed instantly with a 400 error after updating to the last release

Fixed1 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)

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v2.1.276 Claude Code Release Notes

Sep 18, 2026

Claude's Analysisby Sonnet 5

Full Analysis

Emergency same-day fix: v2.1.275 broke every request for anyone routing through a custom API proxy or gateway with a 400 error.

Change

Total Changes (vs Average)

0.1×

Version Type

Patch

Release Focus

Bug Fix

Days Since Prior Release

Release # This Month

#18 of 18

Bug Fix Ratio

100%

Post-Release Edits

—

Change Category

Key Themes

1Proxy/Gateway Hotfix

May Help If You've Noticed

Every request failed instantly with a 400 error after updating to the last release

Fixed1 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)

v2.1.276 Claude Code Release Notes

Changes in Claude Code v2.1.276

Fixed1 change

v2.1.276 Claude Code Release Notes

Changes in Claude Code v2.1.276

Fixed1 change