Claude Code v2.1.156 fixes the third-party provider breakage

Yesterday I wrote about how Claude Code v2.1.154 broke every third-party API provider. The bug was in the fallback logic: Claude Code’s retry handler only caught HTTP 400, but providers return HTTP 422 for validation errors. The beta feature that sends role: "system" in the messages array would fail, the fallback would not trigger, and your conversation died.

Anthropic shipped v2.1.156 a few hours ago. It fixes this.

What changed in v2.1.156

The fallback detection now catches both HTTP 400 and 422. When a provider rejects the mid-conversation-system beta with either status code, Claude Code removes the beta header and falls back to putting system instructions in <system-reminder> blocks inside user messages. This is the same fallback that already worked for first-party API calls that happened to return 400.

Versions 2.1.154 and 2.1.155 still have the bug. Upgrade to 2.1.156 or later.

What claude-multi users need to do

If you are on claude-multi v0.6.0 or later:

claude-multi doctor fix

This reinstalls the pinned Claude binary at ~/.claude-multi/bin/ to v2.1.156 and updates any wrapper scripts that still point to the old version.

If you are on an older version of claude-multi, update first:

bun update -g claude-multi
claude-multi doctor fix

Auto-updates are back on

When the breakage hit, we disabled auto-updates in claude-multi to prevent Claude Code from silently updating to a broken version. Now that v2.1.156 fixes the issue, auto-updates are re-enabled. New instances created with provider templates will not have DISABLE_AUTOUPDATER=1 or DISABLE_UPDATES=1 injected into their settings.

If you have existing instances with those env vars in their settings.json, you can remove them manually or re-apply the provider template. They are harmless to leave in place; they just prevent Claude Code from auto-updating.

The safety infrastructure stays

We are keeping the version pinning and health check code in place, labeled with [SAFE PARK] comments throughout the codebase. If a future Claude Code update breaks third-party providers again, we can reactivate it by flipping a few constants:

• isThirdPartyApiBroken() in src/version.ts gets an updated version range
• COMPATIBLE_CLAUDE_VERSION gets the last working version number
• PROVIDER_COMMON_ENV in src/templates.ts gets DISABLE_AUTOUPDATER and DISABLE_UPDATES back
• autoUpdates in src/config.ts flips back to false

The doctor fix command and the TUI health screen will pick up the changes automatically. No new code needed.

This is the second time in recent months that a Claude Code update has broken provider compatibility. Keeping the safety code parked and ready seems prudent.

TL;DR

• v2.1.156 fixes the HTTP 422 bug that broke third-party providers in v2.1.154 and v2.1.155
• Run claude-multi doctor fix to update your pinned binary
• Auto-updates are re-enabled for new instances
• The pinning safety code stays parked, ready to reactivate if it happens again