API Error: 400 Error (text content blocks must contain non-whitespace text) in Claude Code TUI

Written by Claudio Kuenzler - 0 comments

Published on June 11th 2026 - Listed in AI Linux Coding

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As I am a die hard command line user I use vim to edit 90% of code, so I added Claude Code into the terminal (TUI).

Claude Code itself is a npm package which connects to a local Claude Code Router (ccr), which is another npm package. The ccr connects to an AI provider in the background, where the LLM is accessed (and where the money goes). In my situation I am using Venice AI as AI provider.

This setup has worked quite fine for me, although I haven't used it too often. For the recent changes on the check_smart monitoring plugin I have worked "together" with Claude Code.

Get 10$ worth of token credits on Venice AI, when you sign up using this link.

API Error: 400 Error from provider

But all of a sudden, ccr code stopped working. Whatever prompt I entered, I always got the same error:

ck@mint ~/Git/check_smart $ ccr code

> Hello

API Error: 400 Error from provider(venice,claude-opus-4-5: 400): {"error":"system: text content blocks must contain non-whitespace text","request_id":"MG8uTF0O6lSQVtRUXlGaQ"}Error: Error from provider(venice,claude-opus-4-5: 
  400): {"error":"system: text content blocks must contain non-whitespace text","request_id":"MG8uTF0O6lSQVtRUXlGaQ"}
      at qn (/usr/lib/node_modules/@musistudio/claude-code-router/dist/cli.js:582:7451)
      at fD (/usr/lib/node_modules/@musistudio/claude-code-router/dist/cli.js:582:11338)
      at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
      at async cN (/usr/lib/node_modules/@musistudio/claude-code-router/dist/cli.js:582:8659)

How do you ask AI how to fix this when AI is broken? ;-)

ChatGPT focused on the ccr (Claude Code Router) configuration file and thought there could be a problem - but there wasn't. It also suggested to temporarily remove my local ~/.claude directory and try with an empty/new profile. None of the suggestions worked.

A legacy research on Google pointed me to similar error messages on GitHub, but the issues were either still open or closed without resolution.

The logs in ~/.claude-code-router/logs did not show anything useful (if at all anything) either. 

As ccr code stopped working from one day to another (without having touched the npm packages), maybe I was running an outdated npm package and the AI provider expects the data (prompt) in a newer/different format?

Update npm packages

So let's make sure, we get the latest packages.

ck@mint ~ $ sudo npm install -g @musistudio/claude-code-router
ck@mint ~ $ sudo npm install -g @anthropic-ai/claude-code

With this, the packages should be the latest release.

ck@mint ~ $ npm list -g
/usr/lib
|-- @anthropic-ai/claude-code@2.1.170
|-- @musistudio/claude-code-router@2.0.0
|-- corepack@0.34.6
|-- npm@10.8.2

Now restarting ccr, just to make sure the new version is used:

ck@mint ~ $ ccr stop
claude code router service has been successfully stopped.

ck@mint ~ $ ccr start &
[1] 322902

ck@mint ~ $ ccr status

Claude Code Router Status
===================================
Status: Running
Process ID: 322902
Port: 3456
API Endpoint: http://127.0.0.1:3456
PID File: /home/ck/.claude-code-router/.claude-code-router.pid

Ready to use! Run the following commands:
   ccr code    # Start coding with Claude
   ccr stop   # Stop the service

But right after this, the same error 400 showed up - again!

Cache Cleaning

At this point I thought I will start over. I should remove all packages and ~/.claude* directories and start from scratch. For this I opened the Claude Code for Linux Guide from Venice AI. 

While reading through the whole document, I stumbled on something I haven't really noticed before: The Caching section.

A small drop down menu "When to use cleancache" showed something interesting:

Well, the error message itself does not mention a caching issue at all - but I'm experiencing a "strange behaviour". Let's give it a shot, shall we?

As mentioned in the guide, I added the "cleancache" option into the AI provider's transformer option:

ck@mint ~ $ vi ~/.claude-code-router/config.json
ck@mint ~ $ grep transformer -A 1  ~/.claude-code-router/config.json
      "transformer": {
        "use": ["anthropic", "cleancache"]

And then restarted Claude Code Router using ccr stop and ccr start.

Now a new attempt in my check_smart Git repo:

And this time it worked!!! The prompt responded and no API Error 400 showed up anymore! 

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