### Preflight Checklist - [x] I have searched [existing issues](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20state%3Aopen%20label%3Abug) and this hasn't been reported yet - [x] This is a single bug report (please file separate reports for different bugs) - [x] I am using the latest version of Claude Code ### What's Wrong? ### What Should Happe

[BUG] each tool_use must have a single result. Found multiple `tool_result` blocks

Status Closed — not planned

Maintainer reply None cached

Activity 12 comments · opened Dec 16, 2025 · closed Mar 2, 2026

Preflight Checklist

[x] I have searched existing issues and this hasn't been reported yet
[x] This is a single bug report (please file separate reports for different bugs)
[x] I am using the latest version of Claude Code

What's Wrong?

What Should Happen?

Run without error, IDK how the issue happend therefore I don't have a clear idea how it works in normal.

Error Messages/Logs

API Error: 400 {"error":{"message":"litellm.BadRequestError: OpenAIException - litellm.BadRequestError: Vertex_aiException BadRequestError - 
    {\"type\":\"error\",\"error\":{\"type\":\"invalid_request_error\",\"message\":\"messages.10.content.1: each tool_use must have a single result. Found 
    multiple `tool_result` blocks with id: toolu_vrtx_01WjbYafn5hwELEqiDQ4n2wv\"},\"request_id\":\"req_vrtx_011CW9avnHYBK1RUB8buj7oH\"}. Received Model 
    Group=claude-4.5-haiku\nAvailable Model Group Fallbacks=None. Received Model Group=openai/claude-4.5-haiku\nAvailable Model Group 
    Fallbacks=None","type":null,"param":null,"code":"400"}}

Steps to Reproduce

claude
Ask some questions which would lead claude trying to do with tools

Claude Model

Not sure / Multiple models

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.0.70 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_

View original on GitHub ↗

12 Comments

martinpal · 8 months ago

In my case this seems to happen for task agent only. But it started to happen everytime the task agent is created. Very frustrating. I need to rollback the conversation to before the point where Claude had the idea to create the task agent.

npm-global 2.0.72

changchiyou · 7 months ago

This issue still persists in the latest version, 2.1.7.

hztBUAA · 7 months ago

caiyexiang · 7 months ago

Same issue.
This problem occurs when I use project sub-agents with project skills.
ClaudeCode version: 2.1.7

Jont828 · 7 months ago

+1 as well. I have this error with routing through LiteLLM. Saw this thread describing that downgrading Claude Code fixed it for them, might be of interest.

datduyng · 7 months ago

cervajs · 7 months ago

redhair-vibing · 7 months ago

still 2.1.15

changchiyou · 7 months ago

Hi @iammorganparry, I noticed that you have add a workaround for this issue, but I encountered this error again here:

⏺ Explore(查找 nodeType 設定)                                                                                                                                                                   
  ⎿  Done (0 tool uses · 0 tokens · 0s)                                                                                                                                                         
  ⎿ API Error: 400 {"error":{"message":"litellm.BadRequestError: OpenAIException - litellm.BadRequestError: Vertex_aiException BadRequestError -                                                
    b'{\"type\":\"error\",\"error\":{\"type\":\"invalid_request_error\",\"message\":\"messages.12.content.1: each tool_use must have a single result. Found multiple `tool_result` blocks with  
    id: toolu_vrtx_01PyuN2kaKnfvxXt3aXjH8H9\"},\"request_id\":\"req_vrtx_011CXZHyJStdS7Aq9aM7vAXV\"}'. Received Model Group=claude-4.5-sonnet\nAvailable Model Group Fallbacks=None. Received   
    Model Group=openai/claude-4.5-sonnet\nAvailable Model Group Fallbacks=None","type":null,"param":null,"code":"400"}}

Updated: mb, didn't found that you created the PR in another project instead

Rabusek · 7 months ago

+1 same issue just now
⎿ API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.172.content.2: each tool_use must have a single result. Found multiple
tool_result blocks with id: toolu_012GT7qNPHCz3zUJDx1stJGc"},"request_id":"req_011CXhFdprUZgRGWvsizjziQ"}

Didn't really even use agents, as visible below

github-actions[bot] · 6 months ago

Closing for now — inactive for too long. Please open a new issue if this is still relevant.

github-actions[bot] · 5 months ago

This issue has been automatically locked since it was closed and has not had any activity for 7 days. If you're experiencing a similar issue, please file a new issue and reference this one if it's relevant.