Upstream request failed: Claude Code request failed

Quick fix

First check the specific error returned by the upstream service. The provider must address regional unavailability;

Symptom

Error outputCopy

Upstream request failed

Cause

This error text can correspond to different upstream issues. In Issue #6533, Claude Code using gpt-5.6-luna received a 403 from the upstream service, explicitly stating that the model was unavailable in the user's region. The maintainer confirmed that the issue was on the client or provider side and could not be fixed by CC Switch. Switching to the deepseek model worked.

In Issue #3750, when Claude Desktop sent requests through CC Switch's Anthropic proxy to a sub2api / antigravity backend, the backend might reject the request with HTTP 400 / `INVALID_ARGUMENT` if the `messages` array contained `role: "system"`. This issue was a feature request and was marked as a duplicate of another issue; the provided content does not confirm that a fix was implemented. Therefore, `Upstream request failed` alone is not enough to determine which cause applies.

Fix

1. 1

   Check the full error response and CC Switch logs to see whether they contain `403` and `This model is not available in your region`, or `HTTP 400` / `INVALID_ARGUMENT`.

2. 2

   If the response says the model is unavailable in your region, contact the upstream provider or select a model supported by that service. In Issue #6533, switching to the deepseek model worked.

3. 3

   If you are using Claude Desktop's Anthropic proxy and the error is HTTP 400 / `INVALID_ARGUMENT`, check whether the request contains `role: "system"` in the `messages` array. Issue #3750 reported that the backend required system content in the top-level `system` field; the issue did not provide confirmed CC Switch setup steps.

Affected Versions

ToolClaude Code；Claude Desktop

Version3.16.1、3.19.2（报告版本）

PlatformsmacOSWindows

Source Issues

This page is distilled from 2 real issues

• #3750Claude Desktop Anthropic proxy should normalize messages[].role=system into top-level system for Anthropic-compatible backends
• #6533Failed to authenticate. API Error: 403 Upstream request failed: [403] This model is not available in your region.

FAQ

Why does the CC Switch connection test succeed while actual requests from Claude Desktop fail?

Issue #3750 reported that the connection test passed, but the actual request contained `messages[].role="system"`, causing the upstream antigravity Anthropic-compatible endpoint to return HTTP 400.

What should I do if I see `This model is not available in your region`?

The maintainer of Issue #6533 said the cause was on the client or provider side and could not be fixed by CC Switch. Contact the provider to confirm regional restrictions, or try the deepseek model, which worked in that issue.

Related problems

CC Switch is currently a black box; users cannot customize processing logicThis is a feature request for programmable routing transformation scripts in CC Switch; the original post has no verifiable official solution.1 issues mergedapi failed deserialize json body intoDepending on the error: roll Claude Code back, upgrade cc-switch, turn the local proxy off, or stop sending unsupported fields.8 issues mergedcc-switch Usage Statistics Differ from DeepSeek Official Site / Stop UpdatingUpgrade to v3.19.2 or later, then run “Rebuild Codex Usage” once on the “Usage Statistics” page to correct historical overcounts or missing records.22 issues merged